Sunday, December 19, 2010

Magic and muggle in Austria speciation meeting


Set against a backdrop of vineyards and castles, and held in the summer palace of the Hapsburgs in Laxenburg, was the First European Conference on Speciation Research, organized by Ulf Dieckmann and Ake Brannstrom. Thirty or so talks and many posters fomented a great environment for argument and debate – with or without liquid encouragement.

A principle item of argument was the role of “magic traits” in speciation. The term was originally coined by Sergey Gavrilets in a derisive way to suggest the implausibility of natural populations having traits (or genes) that were under divergent natural selection and also influenced mate choice. Traits/genes like this make speciation, particularly sympatric speciation, much easier and frequently appear in theoretical models demonstrating that sympatric speciation is “plausible.” The funny thing was that empiricists quickly pointed to a large number of traits that seemingly do have these joint effects, including body size in stickleback, beak size in finches, color in butterflies and hamlet fishes, and habitat choice in herbivorous insects. And so magic traits quickly became a rallying point for people studying speciation in sympatry or parapatry: i.e., speciation with gene flow. Now many empirical studies invoke the existence of apparent magic traits in their study system as a way of suggesting an easy, perhaps even inevitable route to speciation. And new theoretical models are now invoking magic traits in a proactive way, rather than cloaking them in alternative genetic structures and explained them away in an apologetic fashion.

So what’s to debate? The first point was that some people felt the term shouldn’t be invoked because it implied that such traits are not believable – when they may actually be common. Others at the meeting disliked the term because it wasn’t defined precisely – although several people are working on doing precisely this. My own point of concern was partly related to this ambiguity. In particular, just how much of the reproductive isolation evolving between two species must such a dual-effect trait explain to warrant the term “magic.” To me, magic implied something important - perhaps speciation wouldn’t have occurred without the magic trait. But it was pointed out by Maria Servedio that the original definition doesn’t imply any effect size. I resisted this for some time, but then realized that not all magic has to be important. Hermione might use “trivial magic” to make a feather float, whereas she might use “important magic” to save Harry’s life. Both actions are magic but only the latter matters. So maybe we need to distinguish “trivial magic traits” from “important magic traits.” Best of all, however, Eva Kisdi noted that the appropriate antonym for a non-magic trait is clearly a “muggle trait,” and so I realized I loved the term.

And so I stayed out until 2 am drinking and arguing with Maria Servedio, Dan Bolnick, Louis Bernatchez, and Isabelle Olivieri. Then I caught a cab for the airport at 4:30 am, and watched the magic of lightly falling snow illuminated by the light from ancient buildings against the inky backdrop of the pre-dawn sky. Trivial perhaps – but no less magic to a muggle.



Other blog posts about the conference:

http://benaustria.blogspot.com/2010/12/speciation-2010.html

http://svenssonresearchlaboratory.blogspot.com/2010/12/greetings-from-speciation-meeting-in.html

Wednesday, December 8, 2010

Anthropogenic disturbance and evolutionary parameters from a natural population of lemon sharks


Little is known about the potential for adaptive evolution to save natural populations faced with environmental change, despite an increasingly present human hand in modifying their environment. These modifications likely reduce the degree to which populations are adapted to their local conditions, thereby decreasing mean fitness and possibly leading to local extinction. Such adaptive processes depend on several factors such as population connectivity, initial population size, mortality rates, adaptive plasticity (or maternal effects), genetic variation, and the strength and form of selection. And yet few studies to date assess if and how each of these factors has changed in the face of anthropogenic forces.

A recent paper from the Hendry lab attempted to fill this gap by combining long-term monitoring (13 years) of marked lemon sharks (Negaprion brevirostris) at an isolated nursery lagoon (Bimini, Bahamas) with genetic pedigree reconstruction (DiBattista et al. 2011, Evolutionary Applications 4[1]: 1-17). DiBattista et al. (2011) assessed whether habitat loss influenced population size, juvenile mortality, maternal effects, genetic variation, and selection in this lemon shark population. This analysis was only possible because recent human activities (i.e., mangrove removal) associated with a large-scale development project at Bimini conveniently bisected their dataset. Contrary to expectation, they found that samples after the disturbance (relative to before the disturbance) showed an increase in 1) the number of sharks breeding at this site, 2) neutral genetic variation, and 3) additive genetic variation for several key juvenile life-history traits (i.e., body size and growth). They also found a dramatic change in selection acting on those same life-history traits; habitat loss here appears to have changed which phenotypes are now favored by natural selection.

The authors therefore conclude that some species may be tolerant to some habitat loss, although this likely depends on the length and duration of the disturbance. Similarly, high levels of gene flow among population may act to buffer losses in neutral and additive genetic variation, and in some cases increase it. Based on the observed changes in the strength and sometimes direction of natural selection acting on life-history traits in this population, it would seem that habitat loss may impede adaptive processes by altering the fitness landscape.

Joseph DiBattista (NSERC postdoctoral fellow at the Hawaii Institute of Marine Biology, University of Hawaii)
Photo Credit
DiBattista JD, Feldheim KA, Garant D, Gruber SH, and Hendry AP (2011). Anthropogenic disturbance and evolutionary parameters: A lemon shark population experiencing habitat loss. Evolutionary Applications 4(1): 1-17.

Photo Credit: Matthew Potenski (http://www.matthewpotenskiphoto.com/)

*Save one, none of the other authors were bitten, maimed, or otherwise harmed during the tagging of said lemon sharks.

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Monday, November 22, 2010

Evolutionary causes and consequences of plasticity

Changes in phenotype directly induced by the environment, called phenotypic plasticity, can have strong evolutionary consequences. Recent papers from the Hendry lab have examined plasticity-evolution relationships (Crispo et al., 2010, EER 12: 47-66; Thibert-Plante & Hendry, in press, JEB).

Crispo et al. conducted a meta-analysis to determine whether phenotypic plasticity generally tends to evolve as a response to human-induced changes to the environment. They examined 20 studies in which plasticity was estimated between populations that were under the influence of anthropogenic stressors, and between closely related populations that had not. They found that it many cases, plasticity had evolved in response to anthropogenic disturbance, when compared to their non-disturbed counterparts. The direction of this change, however, varied greatly among taxa and trait types. For example, invertebrates often showed the evolution of increased plasticity in life history traits and decreased plasticity in morphology, whereas plants showed no trends in plasticity evolution. The authors therefore conclude that plasticity and its evolution might be important for adaptation, but that it should be examined on a case-by-case basis, rather than making general statements about whether increased or decreased plasticity is likely to evolve as an adaptive strategy. The full article can be found at http://www.evolutionary-ecology.com/abstracts/v12/n01/ffar2517.pdf.

Thibert-Plante and Hendry looked at the consequences of phenotypic plasticity on ecological speciation. The consequences of plasticity for ecological speciation depend on the timing of dispersal relative to the expression of the plasticity. On the one hand, if plasticity is expressed early in development, before any dispersal, the individuals dispersing to a different environment will have reduced fitness, relative to the case of no plasticity. On the other hand, if plasticity is expressed after dispersal, the fitness cost of dispersing can be greatly reduced or even completely removed. Those facts are of great importance in the context of ecological speciation, where we study the rise and fall of barriers to gene flow among populations. More details can be found at http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02169.x/abstract.

Xavier Thibert-Plante (FQRNT and NIMBioS postdoctoral fellow, Knoxville)

Erika Crispo (NSERC postdoctoral fellow in Royal Ontario Museum, Toronto)

* The authors have no competing interest, apart from space in high profile scientific journals.

Thursday, November 18, 2010

Constraints on ecological speciation?

“Constraints on speciation suggested by comparing lake-stream stickleback divergence across two continents” – just appeared in Molecular Ecology (19:4963-4978). This paper tests whether the striking phenotypic (foraging morphology) and neutral genetic (microsatellite) divergence that characterizes incipient speciation across lake-stream transitions in Canadian (Vancouver Island) stickleback fish can also be found in some very young (150 years or less) European lake-stream pairs. The main findings are that, first, morphological divergence is generally much lower in the European population pairs, and there are striking overall phenotypic differences between the continents. Although alternative explanations are possible, it seems likely that there are some genetic constraints. Alleles that serve in adaptive lake-stream divergence (e.g. in body shape) in Canada appear to be absent in Europe. Limited time for morphological adaptation might also play a role. Second, there is only trivial divergence in microsatellite frequencies in the European pairs, contrary to the very high divergence found in some Canadian watersheds. This result suggests high gene flow and no evolved reproductive barriers in the young European systems. However, individual-based simulations tailored to these systems reveal that, even if reproductive barriers were absolute, it would be unlikely to see them with neutral markers. Those markers just evolve too slowly. It is thus possible that despite weak morphological divergence, reproductive isolation in Europe pairs could be strong, and hence we are simply dealing with the earliest stages of speciation. This could be possible if isolation is mediated by other traits not studied (e.g. behavior). Follow-up work is examining genome-wide divergence in these lake-stream pairs. This post was contributed by Daniel Berner.

Tuesday, October 19, 2010

Stickleback porn generates duelling papers

Mating isolation is a frequent contributor to ecological speciation – but how consistently does it evolve as a result of divergent selection? An excellent model system to address this question is the threespine stickleback, with its species pairs that evolved multiple times in a diversity of contrasting habitats. Mating isolation could arise through assortative mate choice, such as when females actively choose a male of their own type or when male-male competition does the job for them.

We designed an experiment aiming to demonstrate that at least one of these possibilities would lead to mating isolation in­ the Misty watershed on Vancouver Island, British Columbia. This watershed contains a very divergent but interconnected pair of lake-inlet stream stickleback. In the laboratory, gravid females were introduced into a tank where they could choose between, and be competed for, by two males of different types: lake, stream, or hybrid. Despite very different courtship behaviours of lake and stream males, and seemingly inferior levels of competition of hybrid males, mating patterns were not assortative. In fact, hybrid males obtained the most females. It is hard to define stickleback attractiveness if you are not a stickleback yourself, but hybrid males were reasonably large and aggressive (unlike stream males) and showed some elegance in their courtship (unlike lake males). This combination may have promoted their high mating success.

These results stand in contrast to other stickleback pairs which do show assortative mating, such as the benthic-limnetic and anadromous-freshwater pairs. So far, other studies in the Misty system also haven't found strong reproductive barriers. This is either because we haven't been looking close enough to find the real ecological cause(s) of reproductive isolation, because the real cause(s) are not visible in standard laboratory experiments, or because there is no strong progress towards ecological speciation. Either way, our results highlight the importance of considering the various factors that promote or constrain progress toward ecological speciation.

And just when we were checking the online version of our paper, a very similar study appeared online. Christophe Eizaguirre and colleagues from the Max-Planck Institute for Evolutionary Biology (Plön, Germany) showed that in their lake and stream system, stickleback do choose assortatively based on olfactory cues in a flow channel. Previous studies at MPI Plön have shown that lake and stream stickleback are infected by different parasite communities, and are highly divergent for MHC, a set of immune genes. Interestingly, these genes are also involved in mate choice. Being under both natural and sexual selection, MHC has the potential to act as a “magic trait”, accelerating ecological speciation.

The standing contrast then is that Plön stickleback choose their own type (lake or stream) based on olfactory cues, whereas Misty stickleback don't choose their own type (lake or stream) based on olfactory cues and visible cues together. The latter situation is certainly a more realistic setting. However, another contrast between our experiments was that Misty stickleback were second generation lab-reared fish, while Plön stickleback were captured in the wild. This is important as mating preferences could be learned based on imprinting on conspecifics or experience with heterospecifics (Kozak et al. 2009; Behav. Ecol). Much more work needs to be done to assess the consistency of mating barriers in stickleback, perhaps through reciprocal experiments: what if Misty sticklebacks can only smell their potential mates, and what if Plön sticklebacks can actually see their potential mates? To be continued...

Greetings from Belgium,

Joost Raeymaekers

Raeymaekers JAM, Boisjoly M, Delaire L, Berner D, Räsänen K & Hendry AP (Early online). Testing for mating isolation between ecotypes: laboratory experiments with lake, stream and hybrid stickleback. Journal of Evolutionary Biology. (http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02133.x/abstract)

Eizaguirre C., Lenz T.L., Sommerfeld R.D., Harrod C., Kalbe M. and Milinski M. (Early online). Parasite diversity, patterns of MHC II variation and olfactory based mate choice in diverging three-spined stickleback ecotypes. Evolutionary Ecology. (http://www.springerlink.com/content/0269-7653/?k=10.1007%2fs10682-010-9424-z)

Tuesday, September 7, 2010

Alewife feeding leads to feedbacks


The concept of eco-evolutionary feedbacks unites two well-established theories, which have traditionally existed in isolation. The theory of adaptive radiation, which comes from evolutionary biology, posits that the biotic and abiotic environment determines niche availability, and that lineages diversify until available niches are filled. In contrast, theories of environmental modification, which come from ecology, posit that the activities of organisms modify important aspects of the biotic and abiotic environment. The concept of eco-evolutionary feedbacks integrates these perspectives by recognizing that both processes can occur simultaneously. According to this integrated theoretical framework, adaptive diversification can simultaneously shape and be shaped by the niche-modifying abilities of organisms.

Compelling evidence for the importance of eco-evolutionary feedbacks in the wild comes from our work on alewife-zooplankton interactions in lakes. Anadromous alewives (Alosa pseudoharengus) migrate annually from the Atlantic Ocean to inland lakes where they spawn. Juveniles rear in these lakes, usually for one summer, before departing for the ocean to mature. Our research shows that the isolation of lakes from the ocean by human-constructed dams has led to the evolution of landlocked alewife populations. The ecological effects of landlocked alewife populations are well known from classic work in Connecticut lakes by John Brooks and Stanley Dodson and from studies of the alewife invasion of the Great Lakes. Predation by landlocked alewives drives dramatic shifts in mean body size, biomass, and species composition of crustacean zooplankton. But what about anadromous alewives? Our work shows that the ecological effects of anadromous alewives differ markedly from those of landlocked alewives. In lakes harboring anadromous populations, zooplankton effects are largely seasonal – when the juveniles depart each fall, large-bodied zooplankton recover. However, in landlocked lakes predation pressure is year-round – zooplankton communities are continuously dominated by small-bodied species. A key question is: how do landlocked alewives persist under such unfavorable (small-bodied) prey conditions? Our research shows that the answer lies in contemporary evolution. After eliminating large zooplankton from the lake, landlocked alewife populations rapidly evolve morphological traits (gape width and gill raker spacing) and behavioral traits (prey selectivity) that enable them to be efficient foragers on small-bodied zooplankton. Altered foraging traits then further modify zooplankton community structure and influenced the strength of trophic cascades.

The above results point to an eco-evolutionary feedback. The contemporary evolution of landlocked alewife populations from anadromous ancestors led to changes in zooplankton communities, which in turn shaped the evolution of alewife foraging traits, with then further impacts the structure of prey communities and cascading trophic interactions. Thus, rather than adapting to an existing ecological template (niche), which would be the assumption based on traditional theory, alewives participate in creating the niche to which they are adapted. And the resulting phenotypic divergence then drives further ecological effects. Not a bad days work for a hungry little fish.

Saturday, August 28, 2010

Contemplating speciation from Iceland.

Photo: Andrew Hendry contemplates Holar, where biologists contemplate speciation.

What better place to have a workshop on speciation than Iceland? This dynamic island has contributed so much to our modern understanding of how environmental differences can drive the evolution of reproductive isolation, so-called “ecological speciation”. As freshwater habitats were opened up following the last glaciation, Arctic char, threespine stickleback, and a few other fish species established new populations. These populations then adaptively radiated into new forms, most famously the four reproductively isolated types of Arctic char found in Thingvallavatn, the largest lake in Iceland.

On this inspiring Icelandic backdrop in the first week of August 2010 was held a speciation workshop at Holar University College (ww2.holar.is). The workshop was organized by Skuli Skulason, Ake Brannstrom, and Ulf Dieckmann under the aegis of FroSpects (www.iiasa.ac.at/Research/EEP/FroSpects/). Graciously hosted by Skuli, Bjarni Kristjansson, and their Holar colleagues, the workshop brought together dozens of speciation scientists from Europe and North America. Each person presented talks or posters in the auditorium under the watchful eye of 700 years of Holar bishops.

So what transpired? Many things were discussed, of course, and I can’t cover them all – nor would you wish to read it. So I have merely selected one topic that jumped out as being unresolved. A number of speakers presented theoretical arguments that phenotypic plasticity should promote ecological speciation – by allowing the colonization of new environments or the use of new resources. By contrast, a number of other speakers presented theoretical arguments that phenotypic plasticity should constrain ecological speciation – by reducing divergent selection on genotypes. Both sets of speakers could accept the basic points made by the other, and so we were left with no concrete conclusion about how plasticity ultimately influences ecological speciation.

This topic is likely to remain a hot one over the next few years. I am confident of this partly because it was one of the major points of late-night argument at Bjarni’s “beer club,” only a few years old and already a Holar institution. With the highest diversity of beer at any bar in Iceland – and even some single malt whisky on request – beer club may is becoming another Icelandic inspiration for speciation research. Move over Thingvallavatn.

Tuesday, May 25, 2010

When can ecological speciation be detected with neutral loci?

In this paper we test the statistical power of using neutral markers to infer ecological speciation. We find that this method is powerful only in a limited number of cases, namely when migration is intermediate and selection is strong.

Click here for more details

Friday, May 14, 2010

Sex trips death in the dance of speciation

The following is a press release from The American Naturalist.

Darwin argued that the origin of new species is driven by adaptation to different environments and recent research has confirmed his intuition and given the process its current name "ecological speciation". At the same time, it has become increasingly apparent that different environments do not always cause ecological speciation. Some other forces must therefore constrain the evolution of reproductive barriers that irrevocably sunder one species into several. Jacques Labonne of INRA in France and Andrew Hendry of McGill University in Canada investigate one of these constraining forces by developing simulation models of population divergence in Trinidadian guppies.

Trinidadian guppies are caught up in a perpetual tug of war between sex and death. Colorful males are often favored by females during mating (top image), whereas those same males are thought to be more susceptible to predators (bottom image). As a result, guppy populations above waterfalls, which evolve without dangerous predators, often have more colorful males than those below waterfalls evolving with dangerous predators. Given this evidence of adaptation to different environments, the theory of ecological speciation would predict that the two types of guppies (low-predation and high-predation) should be on their way to speciation, which is not the case. Hendry suggests that "maybe colorful low-predation males moving into high-predation populations pay the price of imminent death, but until then, reap the benefits of more sex." The authors' simulation models confirm that the end result of this conflict between sex and death can be little progress toward ecological speciation. This study illustrates the importance of considering multiple factors that promote and constrain progress toward speciation.

For more details see: Labonne, J., and A.P. Hendry. Natural selection can giveth and taketh away reproductive barriers: models of population divergence in guppies. American Naturalist. To be published in July issue.

Sunday, April 11, 2010

Spatiotemporal variation in natural selection


Forthcoming in Evolution


Weese, D.J., S.P. Gordon, A.P. Hendry, and M.T. Kinnison. Spatiotemporal variation in linear natural selection on body color in wild guppies (Poecilia reticulata)


Despite a number of good examples of the ecological consequences of ongoing evolutionary change (i.e., contemporary evolution), establishing the generality of these eco-evolutionary interactions remains an important challenge. The relevance of such effects in any given situation will depend, at least partly, on the temporal dynamism of the evolutionary mechanisms (selection, gene flow, mutation) that are functionally linked to ecological processes. Testing for contemporary evolution has been facilitated by the recent development of analytical methods that estimate the strength and pattern of natural selection in wild populations using multiple regressions to predict individual fitness from trait values (the slopes of these regressions are called selection coefficients). By replicating these measurements in time, we can reveal the temporal scale at which eco-evolutionary effects are likely to be important.


Along with my co-authors, I used a series of mark-recapture experiments to investigate variation in natural selection on body color in Trinidadian guppies. Among-population variability in male colour is predicted to reflect a balance between the benefits of colour (attracting females) and the costs of colour (attracting predators). consistent with this idea, our natural selection coefficients were negative, colourful guppies generally had lower survival than did drab guppies. However, we also found that selection in this system is highly variable both spatially (among populations) and temporally (within the same population). Surprisingly, this variation was not consistently associated with the presence of dangerous guppy predators. These findings suggest complicated and dynamic interactions among sexual selection, natural selection, predation, and phenotypic evolution in this system. These types of interactions operating on very fine spatiotemporal scales suggest that eco-evolutionary dynamics may be commonplace, and relevant to ecological processes occurring in contemporary time.

Wednesday, March 24, 2010

Phenotypic plasticity and adaptation

I am interested in the role of phenotypic plasticity in adaptation to different environments. Divergent selection can result in adaptive genetic divergence among populations. However, individuals can also adapt through a plastic response; i.e. the environment might have a direct impact on the phenotype without influencing genetic change. The relative contribution of each (genetic vs. plastic adaptation) should be related to the level of dispersal and gene flow among selective environments. Gene flow can constrain adaptive genetic divergence, and therefore plasticity might be favoured under high gene flow scenarios. If heritable variation for plasticity occurs in a meta-population, I predict that plasticity might evolve in response to gene flow. At the same time, plasticity might permit increased dispersal and gene flow among environments.

During my doctoral studies at McGill, I developed a conceptual framework for understanding the above pathways. I then tested some of the framework's predictions in an empirical system: an African cichlid fish from high-oxygen rivers and adjacent low-oxygen swamps. I found that morphological plasticity, in response to dissolved oxygen concentration, was high overall in this species, but that plasticity was higher at locations where dispersal between environments should also be higher. I infer that plasticity might have evolved in response to gene flow between oxygen environments, but more studies are needed to determine causality.

The conceptual framework is published in the following article. The empirical studies are currently in review.
Crispo, E. (2008) Modifying effects of phenotypic plasticity on interactions among natural selection, adaptation and gene flow. Journal of Evolutionary Biology 21:1460-1469

Latest news: I successfully defended my PhD dissertation yesterday!

Sunday, March 14, 2010

What are eco-evolutionary dynamics?

Evolution is obviously driven by ecological differences: think of the adaptive radiation of Darwin’s finches. Just as obviously, ecological processes are influenced by evolution: ecosystems depend on the oxygen produced following the evolution of photosynthesis. Less obvious is how these interactions play out on the short time scales most relevant to conservation and management. Do ecological changes (e.g., invasive species, climate change) drive appreciably evolutionary change over years or decades (i.e., “contemporary evolution”)? Does any such evolution influence ecological variables (population dynamics, community composition, ecosystem function) on similar time scale? These potential interactions between ecology and evolution, as shown in the figure, represent the growing field of eco-evolutionary dynamics.

Many studies have shown that ecological changes cause phenotypic changes in natural populations (eco-to-evo). Examples include species introduced to new environments, native species responding to introduced species, populations exposed to harvesting or pollution, and populations facing climate change. Existing work has shown that the phenotypic changes can be substantial, particularly when humans are involved. What isn’t known generally is just how much of this phenotypic change is the result of evolutionary change versus phenotypic plasticity. Even less is known about how these contemporary phenotypic changes then influence ecological variables on similar time frames (evo-to-eco) – but some nice examples can be provided.

Populations: Phenotypic changes from one year to the next clearly influence population size in ungulates. The genetic contribution to this phenotypic change is not known, whereas a study of butterflies has documented effects of genetic change on population sizes. What remains to be determined is just how common these effects are, and how important they are relative to traditional “ecological” effects (e.g., rainfall or temperature). In addition, it isn’t clear under which conditions these population dynamical effects of evolution can actually save natural populations from extinction (i.e., evolutionary rescue).

Communities: Genetic and phenotypic differences between individual plants have been shown to have noteworthy effects on arthropod communities. Similarly, genetically-based phenotypic differences between fish populations have strong influences on aquatic macro-invertebrate communities. What remains to be determined is, again, how common these effects are and, also, how year-to-year changes in these genes and traits (as opposed to the currently-studied static differences) influence those communities.

Ecosystems: In the same plants and fish studied for community effects (above), genetic and phenotypic differences have been shown to influence ecosystem variables such as decomposition rates, dissolved organic material, light attenuation, and primary productivity. Since the study systems are the same as above, what remains to be discovered is also the same. It will also be interesting to know how often these ecosystem effects of evolution fall into the category of “ecosystem services” that have become so integral to conservation efforts.

The above listing highlights a few specific examples of how evolutionary change might influence ecological variables on short time scales. In addition to the specific uncertainties listed above, some additional general ones come to mind. How often do evolutionary effects on communities and ecosystems flow through the effects of evolution on population dynamics (indirect effects – red to black arrows in the figure) versus changes in the traits themselves (direct effects – red arrows only)? Do the effects of evolutionary change on ecological processes decrease from population to community to ecosystem variables? How often do true feedbacks occur – that is an ecological process drives evolution (green arrows) that then alters that same ecological process (red arrows) and so on? Eco-evolutionary dynamics is an area ripe for future work.


A special journal issue on eco-evolutionary dynamics: http://rstb.royalsocietypublishing.org/content/364/1523

Friday, March 5, 2010

Thesis submission

On February first Xavier submitted his thesis "The driving factors of ecological speciation and their interactions" in which he looked at the effects of gene flow on local adaptation, and reciprocally, the effects of local adaptation on gene flow.

Wednesday, February 24, 2010

Evolution revealed by resurrecting historical resting eggs

Recently published in the January issue of Evolutionary Ecology!

Derry, A.M., S.E. Arnott, and P.T. Boag. 2010. Evolutionary shifts in copepod acid tolerance in an acid-recovering lake indicated by resurrected resting eggs. Evolutionary Ecology 24: 133-145.
http://www.springerlink.com/content/668651t1247q3v18/fulltext.pdf

Long-lived resting eggs of zooplankton are an ecological and evolutionary reservoir that can impact population and community responses to environmental change in lake ecosystems.
I investigated if adaptive shifts in copepod acid tolerance had arisen over a century of environmental change in an acid-recovering lake by resurrecting resting eggs dating from the late 1800s to present. My results suggest that copepods underwent shifts in acid tolerance following both anthropogenic acidification and pH recovery. Further, I found evidence to suggest that maternal effects (the effects of female body condition on the fitness of their offspring) can have an important role for the fitness of older zooplankton genotypes, irrespective of egg age, when historic resting eggs are given an opportunity to hatch into contemporary communities. Adaptive responses through time are important to consider because of their potential to influence community-level interactions in ecosystems recovering from anthropogenic disturbance.

Ben and I are planning to do some individual-based modelling to learn further about the effects of stochastic hatching from historical resting egg banks on contemporary evolution to environmental change.