Workshop 3: Spatial Heterogeneity in Biotic and Abiotic Environment: Effects on Species Ranges, Co-evolution, and Speciation

(February 6,2006 - February 10,2006 )

Organizers


Sergey Gavrilets
Mathematics, University of Tennessee
Mark Kirkpatrick
Section of Integrative Biology, University of Texas
John Thompson
Ecology and Evolutionary Biology, University of California, Santa Cruz

Most biological organisms face biotic and abiotic environments that are spatially heterogeneous across their species ranges. Traditionally, the theoretical studies of the evolutionary consequences of this heterogeneity have concentrated mostly on the conditions for establishment of locally adapted genotypes and on the maintenance of genetic variation across the whole species.

Recently, the interest and emphasis have begun to shift towards biological questions concerning larger scale effects. For example, one important question is about the effects of the immigration of locally deleterious genes on the degree of local adaptation and the ability of species to expand their ranges. Answering this question has implications for the origin and maintenance of biodiversity. Also, the co-evolutionary roles played by organisms can vary substantially across their species ranges, which can result in complex geographic mosaic of co-evolutionary interactions and rapid changes in local populations. The interactions of spatially heterogeneous selection, the limitation of mating possibilities caused by isolation-by-distance, and the evolution of genetically-based mating preferences can result in splitting the initial population into reproductively isolated populations, i.e., in parapatric speciation. The development of adequate population genetic models of parapatric speciation is necessary to guide the development of statistical methods and hypotheses using emerging genomics data to infer the history of speciation in specific groups of biological organisms.

The complexity of the evolutionary dynamics driven by ecological and co-evolutionary interactions in a spatially explicit context requires the development of modeling approaches that are both sophisticated and realistic. This will hardly be possible without genuinely cross-disciplinary interactions. This workshop will bring together physicists, mathematicians, and theoretical and empirical biologists in an attempt to initiate and simplify such interactions.

Accepted Speakers

Jordi Bascompte
Estaction Biologica de Donana, Consejo Superior de Investigaciones Cient'i ficas (CSIC)
Craig Benkman
Zoology and Physiology, University of Wyoming
Edmund (Butch) Brodie
Biology, Indiana University
Roger Butlin
Animal and Plant Sciences, The University of Sheffield
Laurent Excoffier
Zoological Institute, University of Bern
Sylvain Gandon
Génétique et Evolution des Maladies Infectieuses, UMR CNRS/IRD 2724
Sergey Gavrilets
Mathematics, University of Tennessee
Richard Gomulkiewicz
School of Biological Sciences, Washington State University
Ilkka Hanski
Biological and Environmental Sciences, University of Helsinki
Richard Harrison
Ecology and Evolutionary Biology, Cornell University
Jane Hill
Biology, University of York
Robert Holt
Zoology, University of Florida
Henrik Jensen
Mathematics, Imperial College London
Masakado Kawata
Ecology and Evolutionary Biology, Tohoku University
Mark Kirkpatrick
Section of Integrative Biology, University of Texas
Jim Mallet
Biological Diversity, University College London
Alan McKane
Theoretical Physics Group, University of Manchester
Scott Nuismer
Biological Sciences, University of Idaho
John Thompson
Ecology and Evolutionary Biology, University of California, Santa Cruz
Monday, February 6, 2006
Time Session
10:00 AM
11:15 AM
Roger Butlin - Adaptation to Environmental Gradients: Observations on Littorina saxatilis and a simulation

Adaptation to environmental gradients has received much attention recently in two contexts: understanding range margins and their response to environmental change, and evolution of reproductive isolation in parapatry. These two issues are linked by common features in the behaviour of marginal populations and hybrid zones. The rocky shore snail, Littorina saxatilis, has evolved distinct morphotypes at different points on the steep intertidal environmental gradient. This has apparently happened independently at least three times in Europe. AFLP-based approaches have allowed us to investigate the genetic architecture of these adaptations and the barrier to gene flow that they generate. I will also discuss some results from an individual-based simulation of adaptation at range margins. This work has focused on the consequences of introducing factors such as mating dispersal and finite population size into the framework developed by Kirkpatrick and Barton. Adding these real-world features increases the range of parameter space in which stable range margins occur.

11:30 AM
12:45 PM
Ilkka Hanski - Spatially Realistic Models of Metapopulation Dynamics

Models of metapopulation ecology, genetics, and evolution have tended to assume a simple description of landscape structure, which has hindered the testing of models with empirical data. Recent work has attempted to link a more realistic description of landscape structure with modelling of the ecological metapopulation dynamics. It would be helpful to develop a comparable framework for genetic and evolutionary studies. I discuss some empirical results on a well-studied butterfly metapopulation, including coupling of the ecological and evolutionary dynamics in host plant selection and evolution of dispersal in fragmented landscapes.


02:15 PM
03:30 PM
Sylvain Gandon - Fluctuating Epistasis (with or without coevolution) and the Evolution of Recombination in a Metapopulation

Evolutionary biologists have identified several factors that could explain the widespread phenomena of sex and recombination. One hypothesis is that host-parasite interactions favor sex and recombination because they favor the production of rare genotypes. A problem with many of the early models of this so-called Red Queen hypothesis is that several factors are acting together: directional selection, fluctuating epistasis, and drift. It is thus difficult to identify what exactly is selecting for sex in these models. Is one factor more important than the others or is it the synergistic action of these different factors that really matters? Here we focus on the analysis of a simple model with a single mechanism that might select for sex: fluctuating epistasis. We first analyze the evolution of recombination when the temporal variation is driven by the abiotic environment. We then analyze the evolution of recombination in a specific two-species coevolution model. In this model there is no directional selection (allele frequencies remain fixed), and the temporal variation in epistasis is induced by the coevolution with an antagonist species. In both cases we contrast situations with weak or strong selection. In the single species model we derive an expression for the evolutionarily stable (ES) recombination rate. This ES strategy decreases with the speed of the fluctuations of epistasis, but even when fluctuations are very slow (period longer than 100 generations) some recombination rate (>0) can be selected for. In the two-species coevolution model we find that the evolutionary outcome is mainly governed by the maintenance of coevolutionary cycles. In both situations we discuss the effect of migration when recombination evolves in a metapopulation with an infinite number of large populations, using an island model of dispersal.

03:45 PM
05:00 PM
Scott Nuismer - Polygenic Traits and Local Adaptation in Antagonistic Interactions

Empirical studies of host-parasite and predator-prey interactions commonly demonstrate local maladaptation in at least one of the component species. These empirical results are in line with theoretical predictions based upon models of host-parasite interactions mediated by simple genetic mechanisms of infection and resistance. The extent to which these theoretical results extend to host-parasite or predator-prey interactions mediated by quantitative traits is, however, unclear. I will present mathematical and numerical results for a model of spatially structured coevolution mediated by quantitative traits. The results demonstrate that local maladaptation is substantially less likely when coevolution is mediated by quantitative traits.

Tuesday, February 7, 2006
Time Session
09:15 AM
10:30 AM
Richard Harrison - Mosaic Hybrid Zones: Twenty Years After

Two papers published in 1986 set forth the notion that some hybrid zones might profitably be viewed as mosaics of populations or genotypes, reflecting an underlying habitat and/or resource template. I review the theoretical and empirical literature on mosaic hybrid zones that has accumulated in the past two decades, and discuss the insights that have emerged. I also summarize our current understanding of patterns of variation in a field cricket (Gryllus) hybrid zone that provided the initial motivation for thinking about habitat mosaics and their influence on interactions between hybridizing species.

10:45 AM
12:00 PM
Masakado Kawata - Speciation by sensory drive through the evolution of visual pigments along an environmental light gradient

Although theoretical studies suggest sympatric and parapatric speciation can occur through disruptive natural or sexual selection, recent reevaluations of these speciation models indicated that conditions under which this happens are restrictive. Thus, it is important to investigate the probability of such speciation by using models based on explicit genetic mechanisms for female choice and male ornamentation. Here we first show that in simulations in which the evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception of individuals evolves to adapt to the light environment and that females prefer to mate with males whose nuptial color they perceive most intensively. In our simulations color perception depends on the absorption spectra of an individual fs visual pigments. Speciation occurred most frequently when the steepness of the environmental light color gradient was intermediate and dispersal distance of offspring was small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation. The genetic control for male nuptial color also affects the probability of speciation, but far less so then the genetics of female mating preference. We discuss putative cases of sympatric and parapatric speciation in fishes that might, at least partially, be explained by this model.

01:30 PM
02:45 PM
Richard Gomulkiewicz - Fixation of new mutations in spatially variable environments

Species often range over heterogeneous selective environments which, relative to a comparable uniform environment, can have unique impacts on the fate of a new mutation . Different approximations have been developed to characterize the probability of fixation of a new mutation in spatially variable environments for different combinations of migration and selection parameters. However, no single method seems to be accurate for all parameter combinations, and there are some parameter ranges for which no accurate approximation is available. This talk will review the performance of several approximations for the probability of fixation and present a new approximation, based on separation of the time scales of selection and migration. Simulations we performed with symmetric migration suggest that heterogeneous selection never decreased---and at times substantially increased--- the fixation probability of a new mutation compared to a new mutation experiencing homogeneous selection with the same mean intensity.

03:00 PM
04:15 PM
Alan McKane - Stochastic models in biology and their deterministic analogs

I discuss a systematic approach to the modeling of biological systems which starts from individual-based models, and then goes on to derive from these the corresponding deterministic equations which are valid when the size of the system is large. The formalism used to study the stochastic dynamics of the individual-based model is common to a large number of systems, such as models of epidemics, metapopulations, metabolic reactions, biodiversity --- including Hubbell's neutral theory --- as well as more conventional predator-prey and competition models. In contrast to most previous studies, these processes are modeled using master equations, which allows use to be made of well-established methods from the theory of these equations to analyze their behaviors. The formalism naturally generalizes to spatially explicit models, and I will compare the governing deterministic equations for these systems to those which are normally written down on phenomenological grounds. The consequences of these, and other novel aspects of the master equation description for the systems under consideration, will also be explored.

04:30 PM
05:45 PM
Robert Holt - Reflections on Demographic Constraints and Evolution in Heterogeneous Environments

Reflections on Demographic Constraints and Evolution in Heterogeneous Environments

Wednesday, February 8, 2006
Time Session
09:15 AM
10:30 AM
Edmund (Butch) Brodie - Phenotypic Mismatches Across the Geographic Range of a Predator-prey Arms Race

Coevolutionary interactions between species take place over a wide geographic scale. Population subdivision across that range and spatially variable selection within it may lead to a mix of local adaptation and maladaptation for a pair of interacting species. Toxic newts of the genus Taricha and their resistant garter snake predators in the genus Thamnophis illustrate this general pattern throughout their concurrent ranges in western North America. Understanding of the mechanisms of toxicity and resistance in this system allows us to evaluate the degree of ecologically relevant phenotype matching at any given locality. The resultant picture suggests that nearly half of localities are so phenotypically mismatched as to prevent direct reciprocal selection at present. In at least some of these populations, snake predators seem to have 'won' the arms race by evolving sufficiently high levels of resistance to withstand the effects of any observed level of toxicity. The genetic basis of resistance in garter snakes is at least partly understood and suggests that these mismatches may result from single amino acid substitutions in the sodium channels of resistant snake populations.

10:45 AM
12:00 PM
Craig Benkman - A Coevolutionary Arms Race Causes Ecological Speciation in Red Crossbills

Coevolution is widely accepted as one of the dominant forces driving the creation of biodiversity, however the way in which coevolution promotes speciation is not well understood. I will show that divergent selection as the result of a coevolutionary arms race between red crossbills (Loxia curvirostra complex) and Rocky Mountain lodgepole pine (Pinus contorta latifolia) in the South Hills, Idaho promotes ecological speciation in crossbills. Less than one percent of 1285 breeding South Hills crossbills paired with non-South Hills crossbills indicating considerable reproductive isolation. The low frequency of heterotypic pairing was the result of at least three factors. One was related to enhanced seed defenses of lodgepole pine in the South Hills and adaptation of each call type to alternative resources with South Hills crossbills depressing seed availability so that few of the other less well adapted call types persisted in the South Hills (competitive exclusion causing habitat isolation). Another pertained to temporal isolation. When crossbills of other call types moved into the South Hills late in the breeding season, feeding conditions were deteriorating because of seed depletion by crossbills (another competitive effect) so that relatively few non-South Hills crossbills bred. Finally, among those crossbills that bred, pairing was strongly assortative by call type (behavioral isolation) further contributing to reproductive isolation between South Hills crossbills and the two other call types most common in the South Hills (call types 2 and 5), with total reproductive isolation summing to 0.999 on a scale of zero to one. This extremely high level of reproductive isolation indicates that the divergent selection resulting from the coevolutionary arms race between crossbills and pine has not only favored the evolution of a South Hills crossbill, but is also causing it to speciate. Because divergent selection is the result of a coevolutionary arms race between crossbills and lodgepole pine, it provides an example of how a geographic mosaic of coevolution gives rise to divergent selection causing ecological speciation. Coevolution may often drive ecological speciation if coevolutionary trajectories vary among populations causing divergent selection as envisioned in the geographic mosaic theory of coevolution. Indeed, many recent studies have demonstrated that divergent selection between populations may be a common outcome of geographically structured coevolution, including studies of other populations of crossbills. Because ecologically based divergent natural selection is thought to be an important process promoting speciation and coevolution is likely to vary across the range of a species, coevolution could play a prominent role in generating new species via ecological speciation.

01:30 PM
02:45 PM
Sergey Gavrilets - Dynamic Patterns of Adaptive Radiation

Adaptive radiation is defined as the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. When it occurs, adaptive radiation typically follows the colonization of a new environment or the establishment of a "key innovation" which opens new ecological niches and/or new paths for evolution. Here, we take advantage of recent developments in speciation theory and modern computing power to build and explore a large-scale, stochastic, spatially explicit, individual-based model of adaptive radiation driven by adaptation to multidimensional ecological niches. We are able to model evolutionary dynamics of populations with hundreds of thousands of sexual diploid individuals over a time span of 100,000 generations assuming realistic mutation rates and allowing for genetic variation in a large number of both selected and neutral loci. Our results provide theoretical support and explanation for a number of empirical patterns including "area effect", "overshooting effect", "least action effect", as well as for the idea of a "porous genome". Our findings suggest that the genetic architecture of traits involved in the most spectacular radiations might be rather simple. We show that a great majority of speciation events are concentrated early in the phylogeny. Our results emphasize the importance of ecological opportunity and genetic constraints in controlling the dynamics of adaptive radiation.

03:00 PM
04:15 PM
John Thompson - Coevolution, Geographic Ranges, and Speciation: Current Results and Unanswered Questions

Long-term coevolution of species is an inherently geographic process. It is shaped by geographic selection mosaics that create spatially structured coadaptation among pairs and groups of species. It is further fueled by gene flow and by coevolutionary coldspots where one species falls outside the geographic range of the other species or by lack of reciprocal selection in some coexisting populations. In addition, the coevolutionary process is continually reshaped by the appearance of new tips on phylogenetic branches as some locally coevolving populations diverge into coevolving sibling species complexes. These dynamics of coeadaptation and speciation are the interface of microevolution and macroevolution in coevolutionary biology. Moreover, these are the collective processes that allow lineages to coevolve across millennia, despite the transient dynamics and lack of persistence of most locally coevolving populations. Current data and models suggest specific needs for future modeling on how the geographic mosaic coevolution drives adaptation and speciation, and, in turn, how adaptation and speciation collectively reshape the geographic mosaic of coevolution across millennia.

Thursday, February 9, 2006
Time Session
09:15 AM
10:30 AM
Jane Hill - Evolutionary Changes during Climate-driven Range Expansion

Some species are responding to current global climate warming and shifting their distributions polewards and/or uphill. It is becoming clear that evolutionary changes are occurring as a consequences of this climate-driven range expansion. Evidence for increased dispersal ability, shifts onto novel host-plants and increased ability to tolerate poor larval hostplant quality in populations at expanding range margins suggest that some species may be able to keep track of environmental changes. However these changes are balanced by evolutionary trade-offs in fecundity, and most species are failing to expand due to loss of breeding habitat, regardless of any evolutionary adaptations. In addition, reduced genetic diversity in populations expanding through patchy habitats is also likely to affect species' ability to respond to novel environments. I discuss the implications of these findings for the future distribution of biodiversity.

10:45 AM
12:00 PM
Jane Hill - Evolutionary Changes during Climate-driven Range Expansion

Some species are responding to current global climate warming and shifting their distributions polewards and/or uphill. It is becoming clear that evolutionary changes are occurring as a consequences of this climate-driven range expansion. Evidence for increased dispersal ability, shifts onto novel host-plants and increased ability to tolerate poor larval hostplant quality in populations at expanding range margins suggest that some species may be able to keep track of environmental changes. However these changes are balanced by evolutionary trade-offs in fecundity, and most species are failing to expand due to loss of breeding habitat, regardless of any evolutionary adaptations. In addition, reduced genetic diversity in populations expanding through patchy habitats is also likely to affect species' ability to respond to novel environments. I discuss the implications of these findings for the future distribution of biodiversity.

01:30 PM
02:45 PM
Troy Day - Evolutionary Change in Spatially Distributed Populations: A kin selection perspective

Historically, a great deal research in theoretical evolutionary ecology has modeled biological populations by supposing that the population size can take on any of a continuum of values. This assumption is reasonable so long as the population size is relatively large. Much of this research has ignored the consequences of the spatial distribution of populations, but the last couple of decades have seen an increased interest in developing explicitly spatial models for ecological and evolutionary processes. Interestingly, many of these models continue to assume that population sizes at each spatial location can take on a continuum of values. This assumption is often questionable because, although many real biological populations are relatively large, they are often distributed across a spatial range such local population sizes are quite small. I will discuss these issues in more detail, and present some theoretical results illustrating how such finite local population sizes can influence evolutionary change. This will involve an interesting application of ideas related to kin selection theory.

03:00 PM
04:15 PM
Jordi Bascompte - The Spatial Dimension of Ecological Networks

Recent studies have started to unravel the structure of large networks of ecological interactions. This has provided valuable information on network dynamics, coevolution, and responses to human-induced perturbations. What remains to be done is to bring a spatial dimension to these ecological networks. As an example, I will consider two cases. First, I will explore how network structure is molded by spatial processes in a large Caribbean food web. Second, I will consider how the structure of mutualistic networks affects species responses to habitat destruction, a major cause of biodiversity loss and mutualism disruption.


 


References



  1. Fortuna, M.A., and J. Bascompte. Habitat loss and the structure of plant-animal mutualistic networks. Ecology Letters, in press.

  2. Bascompte, J., and C. J. Meli?n. (2005). Simple trophic modules for complex food webs. Ecology, 86: 2868-2873.

  3. Meli?n, C.J., J. Bascompte, and P. Jordano. (2005). Spatial structure and dynamics in a marine food web. In Aquatic Food Webs, A. Belgrano et al. editors. Oxford University Press, pp. 19-24.

  4. Bascompte, J., P. Jordano, C. J. Meli?n and J.M. Olesen. (2003). The nested assembly of plant-animal mutualistic networks. Proceedings of the National Academy of Sciences USA, 100: 9383-9387.

  5. Meli?n, C.J., and J. Bascompte. (2002). Food web structure and habitat loss. Ecology Letters , 5: 37-46.

04:30 PM
05:45 PM
Henrik Jensen - The Tangled Nature Model: A study of community structure, species area relation and species diversity within a model of co-evolution

We present a review of the attempt within the Tangled Nature [1,2] model to understand the effect of evolution and interaction on ecological and evolutionary observables. We report on the relation between the interaction structure in genotype space and the resulting Species Abundance Distribution. Ecological relevant SADs are only obtained if the genotype space allow for a potential high connectivity between species [3]. We also study the relation between the degree of genotype interaction and species diversity [4]. Furthermore we include spatial degrees of freedom to investigate the Species Area Relation from an evolutionary perspective.


The model has been generalised to include correlations in genotype (or phenotype) space and a conserved resource for which all existing types have to compete. This allows us to study, from an evolutionary perspective, the relation between community structure and availability of the conserved resource [5].



  1. K. Christensen, S. A. di Collobiano, M. Hall, and H. J. Jensen, "Tangled Nature: a model of evolutionary ecology." J. of Theor. Biol., vol. 216,73 (2002).

  2. M. Hall, K. Christensen, S. A. di Collobiano and H. J. Jensen, "Time dependent extinction rate and species abundance in the Tangled Nature model of biological evolution." Phys. Rev. E. vol. 66, 011904 (2002).

  3. P. Anderson and H.J. Jensen, "Network Properties, Species Abundance and Evolution in a model of Evolutionary Ecology." J. Theor. Biol. 232/4 , 551-558 (2004).

  4. D. Lawson, H.J. Jensen and K. Kaneko, "Diversity as a product of interspecial interactions." arXiv:q-bio.PE/0505019.

  5. S. Laird and H.J. Jensen, "The Tangled nature model with inheritance and constraint: Evolutionary ecology restricted by a conserved resource." arXiv:q-bio.PE/0510008.

Friday, February 10, 2006
Time Session
09:15 AM
10:30 AM
Jim Mallet - Speciation in Sympatry: Is it so difficult?

After a general introduction, I will concentrate on cases of Lepidoptera speciation I know about. I will argue that many cases of intermediate speciation occur in sympatry, both just below the traditional species level, and just above. The coexistence of these intermediate stages in nature suggests that the whole process of speciation isn't as difficult as all that, especially given local spatial variation in ecological factors. Whether you call this "sympatry" is a matter of taste, but I'll attempt to persuade you that it is sensible to do so, at least if you want any natural populations to be classified as "sympatric" at all.


The idea that speciation in the presence of gene flow is difficult seems merely to be an artifact of a rigid and highly non-darwinian idea: that species are "real" (whatever that means). They are also regarded as "the only real taxon". This was proposed along with the "biological species concept" around 65 years ago, coupled with lots of naivete about about the supposed power of gene flow. Natural populations are telling us that "species reality" and the concomitant "difficulty of speciation" are both greatly overstated. Instead, species are demonstrably continuous with "varieties" in nature, and the evidence of continuous speciation processes is all around us. I believe it would solve a lot of problems to go back to a much more pragmatic view of species and speciation, closer to Darwin's own ideas, and dispense with all that mid-20thC mystical nonsense about "species reality" once and for all.

10:45 AM
12:00 PM
Mark Kirkpatrick - Chromosome Inversions, Local Adaptation, and Speciation

Chromosome inversions may play an important role in adaptation to local environmental conditions. I will discuss models for the evolution of inversions that capture locally-adapted alleles when two populations are exchanging migrants or hybridizing. By suppressing recombination between the loci, a new inversion can spread. Neither drift nor coadaptation between the alleles (epistasis) is needed, so this local adaptation mechanism may apply to a broader range of genetic and demographic situations than alternative hypotheses that have been widely discussed. The mechanism can explain many features observed in inversion systems. The mechanism can establish postzygotic barriers and thus contribute to speciation: it can establish underdominant inversions that decrease heterokaryotype fitness by several percent if the cause of fitness loss is structural, while if the cause is genic there is no limit to the strength of underdominance that can result. The mechanism is expected to cause loci responsible for adaptive species-specific differences to map to inversions, as seen in recent QTL studies.

Name Affiliation
Al-Zein, Mohammad malzein@odu.edu Biological Sciences, Old Dominion University
Allen, Linda linda.j.allen@ttu.edu Mathematics, Texas Tech University
Ayati, Bruce ayati@math.uiowa.edu Math Department, Southern Methodist University
Barany, Ernest ebarany@nmsu.edu Mathematical Sciences, New Mexico State University
Bascompte, Jordi bascompte@ebd.csic.es Estaction Biologica de Donana, Consejo Superior de Investigaciones Cient'i ficas (CSIC)
Benkman, Craig cbenkman@uwyo.edu Zoology and Physiology, University of Wyoming
Best, Janet jbest@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Birand, Aysegul aysegul@nmsu.edu Biology, New Mexico State University
Bolker, Ben bolker@zoo.ufl.edu Department of Zoology, University of Florida
Brodie, Edmund (Butch) edb3@bio.indiana.edu Biology, Indiana University
Butlin, Roger r.k.butlin@sheffield.ac.uk Animal and Plant Sciences, The University of Sheffield
Calder, Catherine calder@stat.ohio-state.edu Statistics, The Ohio State University
Campbell, Lesley campbell.633@osu.edu Evolution, Ecology and Organismal Biology, The Ohio State University
Christensen, Kim k.christensen@imperial.ac.uk Physics, Imperial College London
Cressie, Noel ncressie@stat.ohio-state.edu Statistics, The Ohio State University
Cudney, Jennifer cudney.3@osu.edu Aquatic Ecology Laboratory, The Ohio State University
Day, Troy Other, University of Edinburgh
Djordjevic, Marko mdjordjevic@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Drossel, Barbara barbara.drossel@physik.tu-darmstadt.de Institut fuer Festkoerperphysik, Technische Universitaet Darmstadt
Eaton, Carrie eaton@math.utk.edu Mathematics, University of Tennessee
Enciso, German German_Enciso@hms.harvard.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Excoffier, Laurent laurent.excoffier@zoo.unibe.ch Zoological Institute, University of Bern
Filotas, Elise elise.larose-filotas@UMontreal.CA Geography, University of Montreal
Gandon, Sylvain sylvain.gandon@mpl.ird.fr Génétique et Evolution des Maladies Infectieuses, UMR CNRS/IRD 2724
Garcia-Ramos, Gisela ggarc0@uky.edu Biology, University of Kentucky
Gavrilets, Sergey sergey@tiem.utk.edu Mathematics, University of Tennessee
Gibbs, H. Lisle gibbs.128@osu.edu EEOB, The Ohio State University
Goel, Pranay goelpra@helix.nih.gov Mathematical Biosciences Institute (MBI), The Ohio State University
Gomulkiewicz, Richard gomulki@wsu.edu School of Biological Sciences, Washington State University
Grajdeanu, Paula pgrajdeanu@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Gravner, Janko gravner@math.ucdavis.edu Mathematics Department, University of California, Davis
Greenwald, Katy greenwald.35@osu.edu Evolution, Ecology and Organismal Biology, The Ohio State University
Guan, Bo guan@math.ohio-state.edu Mathematics, The Ohio State University
Guttal, Vishwesha vguttal@princeton.edu Physics, The Ohio State University
Hanski, Ilkka ilkka.hanski@helsinki.fi Biological and Environmental Sciences, University of Helsinki
Harrison, Richard rgh4@cornell.edu Ecology and Evolutionary Biology, Cornell University
Herbers, Joan herbers.4@osu.edu Biology, The Ohio State University
Hill, Jane jkh6@york.ac.uk Biology, University of York
Holt, Robert predator@zoo.ufl.edu Zoology, University of Florida
Irwin, Darren irwin@zoology.ubc.ca Zoology, University of British Columbia
Jensen, Henrik h.jensen@ic.ac.uk Mathematics, Imperial College London
Johnson, Christine johnson.2746@osu.edu Evolution, Ecology & Organismal Biology, The Ohio State University
Just, Winfried just@math.ohio.edu MBI, The Ohio State University
Kawata, Masakado kawata@mail.tains.tohoku.ac.jp Ecology and Evolutionary Biology, Tohoku University
Kimbrell, Tristan kimbrell@ufl.edu Zoology, University of Florida
Kirkpatrick, Mark kirkp@mail.utexas.edu Section of Integrative Biology, University of Texas
Lenormand, Thomas thomas.lenormand@cefe.cnrs.fr Departement Biologie des populations, CEFE - CNRS
Lim, Sookkyung limsk@math.uc.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Lin, Shili lin.328@osu.edu Statistics, The Ohio State University
Loladze, Irakli iloladze@math.unl.edu MBI, The Ohio State University
Lou, Yuan lou@math.ohio-state.edu Mathematics, The Ohio State University
Luo, Jing luo.59@osu.edu Horticulture and Crop Science, The Ohio State University
Malik, Vikas malik.68@osu.edu Evolution, Ecology and Organismal Biology, The Ohio State University
Mallet, Jim j.mallet@ucl.ac.uk Biological Diversity, University College London
Marschall, Libby marschall.2@osu.edu Evolution, Ecology and Organismal Biology, The Ohio State University
McKane, Alan alan.mckane@man.ac.uk Theoretical Physics Group, University of Manchester
Mercer, Kristin mercer.97@osu.edu Evolution, Ecology and Organismal Biology, The Ohio State University
Michalakis, Yannis Yannis.Michalakis@mpl.ird.fr Genetique et Evolution des Maladies Infectieuses, UMR CNRS
Miriti, Maria miriti.1@osu.edu EEOB, The Ohio State University
Moody, Michael miclmood@indiana.edu Biology, Indiana University
Myers, Ransom Ocean Studies, Dalhousie University
Nevai, Andrew anevai@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Niedzwiecki, John niedzwjh@UCMAIL.UC.EDU Biological Sciences, University of Cincinnati
Nuismer, Scott snuismer@uidaho.edu Biological Sciences, University of Idaho
Ortiz-Barrientos, Daniel dortizba@indiana.edu Biology, Indiana University
Passino, Kevin passino.1@osu.edu Electrical and Computer Eng., The Ohio State University
Pitman, Damien pitman@math.ucdavis.edu Mathematics, University of California, Davis
Pol, Diego dpol@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Polechova, Jitka jitka@tiem.utk.edu Ecology & Evolutionary Biology, University of Tennessee
Potter, Dustin potter.153@osu.edu MBI, The Ohio State University
Quaranta, Vito jill.shell@Vanderbilt.Edu Vanderbilt Ingram Cancer Biology Center, Vanderbilt University
Quintero, Estela quintero.11@osu.edu Ecology, Evolution and Organismal Biology, The Ohio State University
Rikvold, Per Arne rikvold@csit.fsu.edu Computational Science and Physics, Florida State University
Rodriguez, Susana rodriguez.219@osu.edu EEOB, The Ohio State University
Ronce, Ophelie ronce@isem.univ-montp2.fr Genetique et Environnement cc 65, Universite Montepellier II
Schugart, Richard richard.schugart@wku.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Sevim, Volkan vs02c@garnet.acns.fsu.edu Physics, Florida State University
Srinivasan, Partha p.srinivasan35@csuohio.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Stigler, Brandy bstigler@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Terman, David terman@math.ohio-state.edu MBI/Math, The Ohio State University
Thompson, John thompson@biology.ucsc.edu Ecology and Evolutionary Biology, University of California, Santa Cruz
Tian, Paul tianjj@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
Waxman, David D.Waxman@sussex.ac.uk Centre for the Study of Evolution, University of Sussex
Wogan, Guin gwogan@berkeley.edu Integrative Biology, University of California, Berkeley
Zhou, Jin jzhou@mbi.osu.edu Mathematical Biosciences Institute (MBI), The Ohio State University
The Spatial Dimension of Ecological Networks

Recent studies have started to unravel the structure of large networks of ecological interactions. This has provided valuable information on network dynamics, coevolution, and responses to human-induced perturbations. What remains to be done is to bring a spatial dimension to these ecological networks. As an example, I will consider two cases. First, I will explore how network structure is molded by spatial processes in a large Caribbean food web. Second, I will consider how the structure of mutualistic networks affects species responses to habitat destruction, a major cause of biodiversity loss and mutualism disruption.


 


References



  1. Fortuna, M.A., and J. Bascompte. Habitat loss and the structure of plant-animal mutualistic networks. Ecology Letters, in press.

  2. Bascompte, J., and C. J. Meli?n. (2005). Simple trophic modules for complex food webs. Ecology, 86: 2868-2873.

  3. Meli?n, C.J., J. Bascompte, and P. Jordano. (2005). Spatial structure and dynamics in a marine food web. In Aquatic Food Webs, A. Belgrano et al. editors. Oxford University Press, pp. 19-24.

  4. Bascompte, J., P. Jordano, C. J. Meli?n and J.M. Olesen. (2003). The nested assembly of plant-animal mutualistic networks. Proceedings of the National Academy of Sciences USA, 100: 9383-9387.

  5. Meli?n, C.J., and J. Bascompte. (2002). Food web structure and habitat loss. Ecology Letters , 5: 37-46.

A Coevolutionary Arms Race Causes Ecological Speciation in Red Crossbills

Coevolution is widely accepted as one of the dominant forces driving the creation of biodiversity, however the way in which coevolution promotes speciation is not well understood. I will show that divergent selection as the result of a coevolutionary arms race between red crossbills (Loxia curvirostra complex) and Rocky Mountain lodgepole pine (Pinus contorta latifolia) in the South Hills, Idaho promotes ecological speciation in crossbills. Less than one percent of 1285 breeding South Hills crossbills paired with non-South Hills crossbills indicating considerable reproductive isolation. The low frequency of heterotypic pairing was the result of at least three factors. One was related to enhanced seed defenses of lodgepole pine in the South Hills and adaptation of each call type to alternative resources with South Hills crossbills depressing seed availability so that few of the other less well adapted call types persisted in the South Hills (competitive exclusion causing habitat isolation). Another pertained to temporal isolation. When crossbills of other call types moved into the South Hills late in the breeding season, feeding conditions were deteriorating because of seed depletion by crossbills (another competitive effect) so that relatively few non-South Hills crossbills bred. Finally, among those crossbills that bred, pairing was strongly assortative by call type (behavioral isolation) further contributing to reproductive isolation between South Hills crossbills and the two other call types most common in the South Hills (call types 2 and 5), with total reproductive isolation summing to 0.999 on a scale of zero to one. This extremely high level of reproductive isolation indicates that the divergent selection resulting from the coevolutionary arms race between crossbills and pine has not only favored the evolution of a South Hills crossbill, but is also causing it to speciate. Because divergent selection is the result of a coevolutionary arms race between crossbills and lodgepole pine, it provides an example of how a geographic mosaic of coevolution gives rise to divergent selection causing ecological speciation. Coevolution may often drive ecological speciation if coevolutionary trajectories vary among populations causing divergent selection as envisioned in the geographic mosaic theory of coevolution. Indeed, many recent studies have demonstrated that divergent selection between populations may be a common outcome of geographically structured coevolution, including studies of other populations of crossbills. Because ecologically based divergent natural selection is thought to be an important process promoting speciation and coevolution is likely to vary across the range of a species, coevolution could play a prominent role in generating new species via ecological speciation.

Phenotypic Mismatches Across the Geographic Range of a Predator-prey Arms Race

Coevolutionary interactions between species take place over a wide geographic scale. Population subdivision across that range and spatially variable selection within it may lead to a mix of local adaptation and maladaptation for a pair of interacting species. Toxic newts of the genus Taricha and their resistant garter snake predators in the genus Thamnophis illustrate this general pattern throughout their concurrent ranges in western North America. Understanding of the mechanisms of toxicity and resistance in this system allows us to evaluate the degree of ecologically relevant phenotype matching at any given locality. The resultant picture suggests that nearly half of localities are so phenotypically mismatched as to prevent direct reciprocal selection at present. In at least some of these populations, snake predators seem to have 'won' the arms race by evolving sufficiently high levels of resistance to withstand the effects of any observed level of toxicity. The genetic basis of resistance in garter snakes is at least partly understood and suggests that these mismatches may result from single amino acid substitutions in the sodium channels of resistant snake populations.

Adaptation to Environmental Gradients: Observations on Littorina saxatilis and a simulation

Adaptation to environmental gradients has received much attention recently in two contexts: understanding range margins and their response to environmental change, and evolution of reproductive isolation in parapatry. These two issues are linked by common features in the behaviour of marginal populations and hybrid zones. The rocky shore snail, Littorina saxatilis, has evolved distinct morphotypes at different points on the steep intertidal environmental gradient. This has apparently happened independently at least three times in Europe. AFLP-based approaches have allowed us to investigate the genetic architecture of these adaptations and the barrier to gene flow that they generate. I will also discuss some results from an individual-based simulation of adaptation at range margins. This work has focused on the consequences of introducing factors such as mating dispersal and finite population size into the framework developed by Kirkpatrick and Barton. Adding these real-world features increases the range of parameter space in which stable range margins occur.

Evolutionary Change in Spatially Distributed Populations: A kin selection perspective

Historically, a great deal research in theoretical evolutionary ecology has modeled biological populations by supposing that the population size can take on any of a continuum of values. This assumption is reasonable so long as the population size is relatively large. Much of this research has ignored the consequences of the spatial distribution of populations, but the last couple of decades have seen an increased interest in developing explicitly spatial models for ecological and evolutionary processes. Interestingly, many of these models continue to assume that population sizes at each spatial location can take on a continuum of values. This assumption is often questionable because, although many real biological populations are relatively large, they are often distributed across a spatial range such local population sizes are quite small. I will discuss these issues in more detail, and present some theoretical results illustrating how such finite local population sizes can influence evolutionary change. This will involve an interesting application of ideas related to kin selection theory.

Fluctuating Epistasis (with or without coevolution) and the Evolution of Recombination in a Metapopulation

Evolutionary biologists have identified several factors that could explain the widespread phenomena of sex and recombination. One hypothesis is that host-parasite interactions favor sex and recombination because they favor the production of rare genotypes. A problem with many of the early models of this so-called Red Queen hypothesis is that several factors are acting together: directional selection, fluctuating epistasis, and drift. It is thus difficult to identify what exactly is selecting for sex in these models. Is one factor more important than the others or is it the synergistic action of these different factors that really matters? Here we focus on the analysis of a simple model with a single mechanism that might select for sex: fluctuating epistasis. We first analyze the evolution of recombination when the temporal variation is driven by the abiotic environment. We then analyze the evolution of recombination in a specific two-species coevolution model. In this model there is no directional selection (allele frequencies remain fixed), and the temporal variation in epistasis is induced by the coevolution with an antagonist species. In both cases we contrast situations with weak or strong selection. In the single species model we derive an expression for the evolutionarily stable (ES) recombination rate. This ES strategy decreases with the speed of the fluctuations of epistasis, but even when fluctuations are very slow (period longer than 100 generations) some recombination rate (>0) can be selected for. In the two-species coevolution model we find that the evolutionary outcome is mainly governed by the maintenance of coevolutionary cycles. In both situations we discuss the effect of migration when recombination evolves in a metapopulation with an infinite number of large populations, using an island model of dispersal.

Dynamic Patterns of Adaptive Radiation

Adaptive radiation is defined as the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. When it occurs, adaptive radiation typically follows the colonization of a new environment or the establishment of a "key innovation" which opens new ecological niches and/or new paths for evolution. Here, we take advantage of recent developments in speciation theory and modern computing power to build and explore a large-scale, stochastic, spatially explicit, individual-based model of adaptive radiation driven by adaptation to multidimensional ecological niches. We are able to model evolutionary dynamics of populations with hundreds of thousands of sexual diploid individuals over a time span of 100,000 generations assuming realistic mutation rates and allowing for genetic variation in a large number of both selected and neutral loci. Our results provide theoretical support and explanation for a number of empirical patterns including "area effect", "overshooting effect", "least action effect", as well as for the idea of a "porous genome". Our findings suggest that the genetic architecture of traits involved in the most spectacular radiations might be rather simple. We show that a great majority of speciation events are concentrated early in the phylogeny. Our results emphasize the importance of ecological opportunity and genetic constraints in controlling the dynamics of adaptive radiation.

Fixation of new mutations in spatially variable environments

Species often range over heterogeneous selective environments which, relative to a comparable uniform environment, can have unique impacts on the fate of a new mutation . Different approximations have been developed to characterize the probability of fixation of a new mutation in spatially variable environments for different combinations of migration and selection parameters. However, no single method seems to be accurate for all parameter combinations, and there are some parameter ranges for which no accurate approximation is available. This talk will review the performance of several approximations for the probability of fixation and present a new approximation, based on separation of the time scales of selection and migration. Simulations we performed with symmetric migration suggest that heterogeneous selection never decreased---and at times substantially increased--- the fixation probability of a new mutation compared to a new mutation experiencing homogeneous selection with the same mean intensity.

Spatially Realistic Models of Metapopulation Dynamics

Models of metapopulation ecology, genetics, and evolution have tended to assume a simple description of landscape structure, which has hindered the testing of models with empirical data. Recent work has attempted to link a more realistic description of landscape structure with modelling of the ecological metapopulation dynamics. It would be helpful to develop a comparable framework for genetic and evolutionary studies. I discuss some empirical results on a well-studied butterfly metapopulation, including coupling of the ecological and evolutionary dynamics in host plant selection and evolution of dispersal in fragmented landscapes.


Mosaic Hybrid Zones: Twenty Years After

Two papers published in 1986 set forth the notion that some hybrid zones might profitably be viewed as mosaics of populations or genotypes, reflecting an underlying habitat and/or resource template. I review the theoretical and empirical literature on mosaic hybrid zones that has accumulated in the past two decades, and discuss the insights that have emerged. I also summarize our current understanding of patterns of variation in a field cricket (Gryllus) hybrid zone that provided the initial motivation for thinking about habitat mosaics and their influence on interactions between hybridizing species.

Evolutionary Changes during Climate-driven Range Expansion

Some species are responding to current global climate warming and shifting their distributions polewards and/or uphill. It is becoming clear that evolutionary changes are occurring as a consequences of this climate-driven range expansion. Evidence for increased dispersal ability, shifts onto novel host-plants and increased ability to tolerate poor larval hostplant quality in populations at expanding range margins suggest that some species may be able to keep track of environmental changes. However these changes are balanced by evolutionary trade-offs in fecundity, and most species are failing to expand due to loss of breeding habitat, regardless of any evolutionary adaptations. In addition, reduced genetic diversity in populations expanding through patchy habitats is also likely to affect species' ability to respond to novel environments. I discuss the implications of these findings for the future distribution of biodiversity.

Evolutionary Changes during Climate-driven Range Expansion

Some species are responding to current global climate warming and shifting their distributions polewards and/or uphill. It is becoming clear that evolutionary changes are occurring as a consequences of this climate-driven range expansion. Evidence for increased dispersal ability, shifts onto novel host-plants and increased ability to tolerate poor larval hostplant quality in populations at expanding range margins suggest that some species may be able to keep track of environmental changes. However these changes are balanced by evolutionary trade-offs in fecundity, and most species are failing to expand due to loss of breeding habitat, regardless of any evolutionary adaptations. In addition, reduced genetic diversity in populations expanding through patchy habitats is also likely to affect species' ability to respond to novel environments. I discuss the implications of these findings for the future distribution of biodiversity.

Reflections on Demographic Constraints and Evolution in Heterogeneous Environments

Reflections on Demographic Constraints and Evolution in Heterogeneous Environments

The Tangled Nature Model: A study of community structure, species area relation and species diversity within a model of co-evolution

We present a review of the attempt within the Tangled Nature [1,2] model to understand the effect of evolution and interaction on ecological and evolutionary observables. We report on the relation between the interaction structure in genotype space and the resulting Species Abundance Distribution. Ecological relevant SADs are only obtained if the genotype space allow for a potential high connectivity between species [3]. We also study the relation between the degree of genotype interaction and species diversity [4]. Furthermore we include spatial degrees of freedom to investigate the Species Area Relation from an evolutionary perspective.


The model has been generalised to include correlations in genotype (or phenotype) space and a conserved resource for which all existing types have to compete. This allows us to study, from an evolutionary perspective, the relation between community structure and availability of the conserved resource [5].



  1. K. Christensen, S. A. di Collobiano, M. Hall, and H. J. Jensen, "Tangled Nature: a model of evolutionary ecology." J. of Theor. Biol., vol. 216,73 (2002).

  2. M. Hall, K. Christensen, S. A. di Collobiano and H. J. Jensen, "Time dependent extinction rate and species abundance in the Tangled Nature model of biological evolution." Phys. Rev. E. vol. 66, 011904 (2002).

  3. P. Anderson and H.J. Jensen, "Network Properties, Species Abundance and Evolution in a model of Evolutionary Ecology." J. Theor. Biol. 232/4 , 551-558 (2004).

  4. D. Lawson, H.J. Jensen and K. Kaneko, "Diversity as a product of interspecial interactions." arXiv:q-bio.PE/0505019.

  5. S. Laird and H.J. Jensen, "The Tangled nature model with inheritance and constraint: Evolutionary ecology restricted by a conserved resource." arXiv:q-bio.PE/0510008.

Speciation by sensory drive through the evolution of visual pigments along an environmental light gradient

Although theoretical studies suggest sympatric and parapatric speciation can occur through disruptive natural or sexual selection, recent reevaluations of these speciation models indicated that conditions under which this happens are restrictive. Thus, it is important to investigate the probability of such speciation by using models based on explicit genetic mechanisms for female choice and male ornamentation. Here we first show that in simulations in which the evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception of individuals evolves to adapt to the light environment and that females prefer to mate with males whose nuptial color they perceive most intensively. In our simulations color perception depends on the absorption spectra of an individual fs visual pigments. Speciation occurred most frequently when the steepness of the environmental light color gradient was intermediate and dispersal distance of offspring was small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation. The genetic control for male nuptial color also affects the probability of speciation, but far less so then the genetics of female mating preference. We discuss putative cases of sympatric and parapatric speciation in fishes that might, at least partially, be explained by this model.

Chromosome Inversions, Local Adaptation, and Speciation

Chromosome inversions may play an important role in adaptation to local environmental conditions. I will discuss models for the evolution of inversions that capture locally-adapted alleles when two populations are exchanging migrants or hybridizing. By suppressing recombination between the loci, a new inversion can spread. Neither drift nor coadaptation between the alleles (epistasis) is needed, so this local adaptation mechanism may apply to a broader range of genetic and demographic situations than alternative hypotheses that have been widely discussed. The mechanism can explain many features observed in inversion systems. The mechanism can establish postzygotic barriers and thus contribute to speciation: it can establish underdominant inversions that decrease heterokaryotype fitness by several percent if the cause of fitness loss is structural, while if the cause is genic there is no limit to the strength of underdominance that can result. The mechanism is expected to cause loci responsible for adaptive species-specific differences to map to inversions, as seen in recent QTL studies.

Speciation in Sympatry: Is it so difficult?

After a general introduction, I will concentrate on cases of Lepidoptera speciation I know about. I will argue that many cases of intermediate speciation occur in sympatry, both just below the traditional species level, and just above. The coexistence of these intermediate stages in nature suggests that the whole process of speciation isn't as difficult as all that, especially given local spatial variation in ecological factors. Whether you call this "sympatry" is a matter of taste, but I'll attempt to persuade you that it is sensible to do so, at least if you want any natural populations to be classified as "sympatric" at all.


The idea that speciation in the presence of gene flow is difficult seems merely to be an artifact of a rigid and highly non-darwinian idea: that species are "real" (whatever that means). They are also regarded as "the only real taxon". This was proposed along with the "biological species concept" around 65 years ago, coupled with lots of naivete about about the supposed power of gene flow. Natural populations are telling us that "species reality" and the concomitant "difficulty of speciation" are both greatly overstated. Instead, species are demonstrably continuous with "varieties" in nature, and the evidence of continuous speciation processes is all around us. I believe it would solve a lot of problems to go back to a much more pragmatic view of species and speciation, closer to Darwin's own ideas, and dispense with all that mid-20thC mystical nonsense about "species reality" once and for all.

Stochastic models in biology and their deterministic analogs

I discuss a systematic approach to the modeling of biological systems which starts from individual-based models, and then goes on to derive from these the corresponding deterministic equations which are valid when the size of the system is large. The formalism used to study the stochastic dynamics of the individual-based model is common to a large number of systems, such as models of epidemics, metapopulations, metabolic reactions, biodiversity --- including Hubbell's neutral theory --- as well as more conventional predator-prey and competition models. In contrast to most previous studies, these processes are modeled using master equations, which allows use to be made of well-established methods from the theory of these equations to analyze their behaviors. The formalism naturally generalizes to spatially explicit models, and I will compare the governing deterministic equations for these systems to those which are normally written down on phenomenological grounds. The consequences of these, and other novel aspects of the master equation description for the systems under consideration, will also be explored.

Polygenic Traits and Local Adaptation in Antagonistic Interactions

Empirical studies of host-parasite and predator-prey interactions commonly demonstrate local maladaptation in at least one of the component species. These empirical results are in line with theoretical predictions based upon models of host-parasite interactions mediated by simple genetic mechanisms of infection and resistance. The extent to which these theoretical results extend to host-parasite or predator-prey interactions mediated by quantitative traits is, however, unclear. I will present mathematical and numerical results for a model of spatially structured coevolution mediated by quantitative traits. The results demonstrate that local maladaptation is substantially less likely when coevolution is mediated by quantitative traits.

Coevolution, Geographic Ranges, and Speciation: Current Results and Unanswered Questions

Long-term coevolution of species is an inherently geographic process. It is shaped by geographic selection mosaics that create spatially structured coadaptation among pairs and groups of species. It is further fueled by gene flow and by coevolutionary coldspots where one species falls outside the geographic range of the other species or by lack of reciprocal selection in some coexisting populations. In addition, the coevolutionary process is continually reshaped by the appearance of new tips on phylogenetic branches as some locally coevolving populations diverge into coevolving sibling species complexes. These dynamics of coeadaptation and speciation are the interface of microevolution and macroevolution in coevolutionary biology. Moreover, these are the collective processes that allow lineages to coevolve across millennia, despite the transient dynamics and lack of persistence of most locally coevolving populations. Current data and models suggest specific needs for future modeling on how the geographic mosaic coevolution drives adaptation and speciation, and, in turn, how adaptation and speciation collectively reshape the geographic mosaic of coevolution across millennia.