Updated information about lab-meeting on April 9: ERC, phylogenies and tropical diversification

This is an update about the coming lab-meeting on Tuesday April (10.30), as there was some mis-communication, and it turns out Lesley will not be able to attend the meeting due to a course in landscape genetics, and this is probably also the case for Rachel and Maren. The lab-meeting on Tuesday will start with  Jessica presenting her ERC-talk for the coming interview in Brussels, and she can then get final feedback from the lab-members that attend. Our new student Anais from Cataluna has also promised to bring some catalunian "fika", and we can try out the red wine she brought last week.

Then, we should discuss this paper that I originally suggested which deals with how the use of multiple phylogenies can be used to answer basic ecological and evolutionary questions about the niche conservatism and range expansions and test the classical "tropical conservatism" hypothesis. This paper is in press in Evolution, and is quite long, but in case you have time you can also read the shorter paper Lesley suggested that was published in Ecology Letters. 

Both these papers are thematically similar and demonstrate the power of a phylogenetic perspective and modern comparative methods to address fundamental problems and general processes in ecology and evolution. The titles and abstracts of both papers are posted below. Enjoy!

WHAT CAN MULTIPLE PHYLOGENIES SAY ABOUT THE LATITUDINAL DIVERSITY GRADIENT? A NEW LOOK AT THE TROPICAL CONSERVATISM, OUT OF THE TROPICS, AND DIVERSIFICATION RATE HYPOTHESES

1. Roland Jansson, 
2. Genoveva Rodríguez-Castañeda, 
3. Larisa E. Harding

We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16–22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no difference in diversification between tropical and temperate sister lineages; thus, diversity of tropical clades was not explained by higher diversification rates in this zone. Moreover, lineages with latitudinal stasis diversified more compared to sister lineages entering a new latitudinal zone. This preserved preexisting diversity differences between latitudinal zones and can be considered a new mechanism for why diversity tends to peak in the zone of origin.

Species interactions constrain geographic range expansion over evolutionary time

Alex L. Pigot^*, 

Joseph A. Tobias

Whether biotic interactions limit geographic ranges has long been controversial, and traditional analyses of static distribution patterns have made little progress towards resolving this debate. Here, we use a novel phylogenetic approach to test whether biotic interactions constrain the transition to secondary sympatry following speciation. Applying this temporal framework to a diverse clade of passerine birds (Furnariidae), we reject models of geographic range overlap limited purely by dispersal or environmental constraints, and instead show that rates of secondary sympatry are positively associated with both the phylogenetic and morphological distance between species. Thus, transition rates to sympatry increase with time since divergence and accelerate as the ecological differences between species accumulate. Taken together, these results provide strong empirical evidence that biotic interactions – and primarily ecological competition – limit species distributions across large spatial and temporal scales. They also offer phylogenetic and trait-based metrics by which these interactions can be incorporated into ecological forecasting models.

On cliff effects, male mate preferences and niche use in Calopteryx

#by Maren Wellenreuther

I am following Erik’s recommendation that we should all start to more actively promote our own research, and will present some of my most recent publications.The first work  that I would like to highlight is a paper that was started in 2007, when Shawn Kuchta and I arrived in Sweden to start our postdocs on the two charismatic Calopteryx damselfly species found in Sweden, C. virgo and C. splendens. We both arrived just at the start of the field season in May 2007 and had never worked on odonates before. It was an exciting time: we were both living at the University's field station in the middle of the forest, which was also used as a military training ground, and so we could relax in the evening after a hard day in the field, while watching the military training tanks and troops drive through the forest and fields outside the station. Shawn had worked for many years on salamanders while I had studied marine fish, and the different view points and ideas that came along with having studied such different study systems made our conversations about science and evolution rich and interesting. Shawn's work on  Calopteryx damselflies is seeking to measure the strength of natural selection acting on the two Calopteryx species (see photograph below), by collecting wings from feeding stations and comparing them to the variation present in natural populations. Although Shawn has left Sweden and is now an Assistant Professor at Ohio University, he is still actively involved in Calopteryx research and is currently writing up this data-so stay tuned for more on this soon!

Calopteryx splendens (left) have wing patches that cover roughly 50% of the wings, while C. virgo have almost fully melanised wings.

At that time that Shawn and I started our work on Calopteryx damselflies in Sweden, another member joined the lab group. Her name is Elodie Vercken, and she was a newly finished postdoc from France who had worked with Jean Clobert on colour morphs and alternative strategies in the common lizard Lacerta vivipara. She is now a researcher at INRA (National Institute for Agronomical Research) in Sophia Antipolis in France.

Elodie Vercken in the field in Sweden catching damselflies fort mate choice experiments.

Together with Elodie, I spent my days out in the field to measure male and female mate choice in different populations, and trying to relate this mate preference data to population ecology and phenotypic traits (sympatry versus allopatry and so on). It was a hot summer and we tried to stay cool while tethering males and females of both species to bamboo sticks and painting their wings to perform mate presentation experiments. It was great fun.

Maren Wellenreuther presenting tethered damselflies in the field

Part of the data that we gathered during that summer was recently used in a modeling paper on cliff-edge effects, which tests the counterintuitive idea that the trait value associated with the maximum of an asymmetrical fitness function is not necessarily the value that is selected for when the trait shows variability in its phenotypic expression.
Vercken E, Wellenreuther M, Svensson EI, Mauroy B (2012) Don't Fall Off the Adaptation Cliff: When Asymmetrical Fitness Selects for Suboptimal Traits. PLoS ONE 7(4): e34889.

From that field season, Elodie, Erik and I also published a paper on male mate preferences in C. splendens, to address the question whether males can distinguish between immigrant and resident females, something previously found for females.

Wellenreuther M, Vercken E and Svensson EI (2010) A role for ecology in male mate discrimination of immigrant females in Calopteryx damselflies? Biological Journal of the Linnean Society 100: 506-518

In addition to these two papers, I further delved into an area that I had investigated extensively during my PhD work: Habitat use and divergence in habitat space between species. The idea was to extent the work that was previously done by our lab and other groups on the habitat use of the two Calopteryx species, by expanding the spatial scale so that broader questions can be asked. To do this, a large data set for the whole of Fennoscandia was generated using field data and museum records, and niche modelling was used to estimate the extent of niche divergence versus conservatism and to identify the most important environmental variables that correspond to niche differences.  The large data set in this paper also allowed us to look into the following question: what is the extent of niche divergence in species that are thought to have primarily evolved through sexual selection on secondary sexual traits? Based on our results, we argue that adaptive niche diversification appears to play a relatively minor role in speciation and evolutionary divergence in species groups such as salamaders, East African cichlids, and odonates where sexual selection on secondary sexual traits is pronounced and a key element of diversification. This work was done in collaboration with Keith W Larson who has excellent modelling skills and likes to analyze large data sets.

Wellenreuther M, Larson K W and Svensson E I. (in press) Climatic niche similarity and geographic range limits in ecologically similar co-existing damselflies –Ecology

Maybe Anna Runemark, who is currently finishing her PhD thesis on the Skyros Wall lizard, would like to write the next blog post by telling us about her most recent articles.


Happy Researching!

The abstracts to the papers are posted below. 

Vercken E, Wellenreuther M, Svensson EI, Mauroy B (2012) Don't Fall Off the Adaptation Cliff: WhenAsymmetrical Fitness Selects for Suboptimal Traits. PLoS ONE 7(4): e34889.

Abstract: The cliff-edge hypothesis introduces the counterintuitive idea that the trait value associated with the maximum of an asymmetrical fitness function is not necessarily the value that is selected for if the trait shows variability in its phenotypic expression. We develop a model of population dynamics to show that, in such a system, the evolutionary stable strategy depends on both the shape of the fitness function around its maximum and the amount of phenotypic variance. The model provides quantitative predictions of the expected trait value distribution and provides an alternative quantity that should be maximized (“genotype fitness”) instead of the classical fitness function (“phenotype fitness”). We test the model's predictions on three examples: (1) litter size in guinea pigs, (2) sexual selection in damselflies, and (3) the geometry of the human lung. In all three cases, the model's predictions give a closer match to empirical data than traditional optimization theory models. Our model can be extended to most ecological situations, and the evolutionary conditions for its application are expected to be common in nature.

Wellenreuther M, Vercken E and Svensson EI (2010) A role for ecology in male matediscrimination of immigrant females in Calopteryx damselflies? Biological Journal of the Linnean Society 100: 506-518

Abstract: Sexual selection against immigrants is a mechanism that can regulate premating isolation between populations but, so far, few field studies have examined whether males can discriminate between immigrant and resident females. Males of the damselfly Calopteryx splendens show mate preferences and are able to force pre-copulatory tandems. We related male mate responses to the ecological characteristics of female origin, geographic distances between populations, and morphological traits of females to identify factors influencing male mate discrimination. Significant heterogeneity between populations in male mate responses towards females was found. In some populations, males discriminated strongly against immigrant females, whereas the pattern was reversed or nonsignificant in other populations. Immigrant females were particularly attractive to males when they came from populations with similar predation pressures and densities of conspecifics. By contrast, immigrant females from populations with strongly dissimilar predation pressures and conspecific densities were not attractive to males. Differences in the abiotic environment appeared to affect mating success to a lesser degree. This suggests that male mate discrimination is context-dependent and influenced by ecological differences between populations, a key prediction of ecological speciation theory. The results obtained in the present study suggest that gene-flow is facilitated between ecologically similar populations.

Wellenreuther M, Larson K W and Svensson E I. (in press) Climatic niche similarity and geographic range limits in ecologically similar co-existing damselflies –Ecology
The factors that determine species' range limits are of central interest to biologists. One particularly interesting group are odonates (dragonflies and damselflies), which show large differences in secondary sexual traits and respond quickly to climatic factors, but often have minor interspecific niche differences, challenging models of niche-based species co-existence. We quantified the environmental niches at two geographic scales to understand the ecological causes of northern range limits and the co-existence of two congeneric damselflies (Calopteryx splendens and C. virgo). Using environmental niche modelling, we quantified niche divergence first across the whole geographic range in Fennoscandia and second only in the sympatric part of this range. We found evidence for interspecific divergence along the environmental axes of temperature and precipitation across the northern range in Fennoscandia, suggesting that adaptation to colder and wetter climate might have allowed C. virgo to expand further northwards than C. splendens. However, in the sympatric zone in southern Fennoscandia we found only negligible and non-significant niche differences. Minor niche differences in sympatry lead to frequent encounters and intense interspecific sexual interactions at the local scale of populations. Nevertheless, niche differences across Fennoscandia suggest that species-differences in physiological tolerances limit range expansions northwards, and that current and future climate could have large effects on the distributional ranges of these and ecological similar insects. 

Welcome Lesley Lancaster, our new postdoc

I am pleased to welcome Lesley Lancaster, our new incoming postdoc, funded by BECC ("Biodiversity and Ecosystem Services in Changing Climate"). Lesley will arrive to Lund in late May or early June, and she will work with me and Bengt Hansson on the population genetics and ecology of range limit evolution, particularly using our favourite model organism: the damselfly Ischnura elegans ("Common Bluetail") as the main study object. Both Bengt and I are very excited about this project and about recruiting Lesley, who will bring with her new skills and perspectives from her previous research.

Currently, Lesley is a postdoctoral scholar at  the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara (California, USA), where she has been since 2009. Her main focus of research has been to reconstruct historical evolutionary processes of adaptation, speciation, extinction and migration using time-calibrated molecular phylogenies of various Californian plant clades. She is also interested in historical habitat tolerances of the unique California chaparral habitat. Her postdoctoral research has resulted in some interesting papers in BMC Evolutionary Biology and Systematic Biology.

Lesley's thesis research was on a quite different topic: maternal effects, reproductive strategies and evolutionary ecology of a colour polymorphic lizard (Uta stansburiana), where she worked in the laboratory of Barry Sinervo at University of California, Santa Cruz (UCSC). Her thesis work also resulted in a number of interesting and impressive publications in American Naturalist, Ecology Letters, Evolution and PNAS. 

Lesley is thus an extremely broad and well-rounded biologist and a very experienced postdoc, who has worked at quite different levels of biological organization, and moved her research focus from studies of individual behaviour and evolutionary ecology, to broader macroevolutionary and macroecological questions. It is for precisely these reasons we are excited to bring her in to Lund; she has both sufficient much in common with our already ongoing research,  yet has many complementary skills that will be of interest to us and our research.

On "Evolutionary rescue", climate change and evolution of range limits

This week the lab-meeting will focus on  "Evolutionary rescue", which was a topic of a recent scientific conference involving several leading evolutionary biologists and ecologists in France, including leading population geneticist Mark Kirkpatrick who gave a talk entitled: "The evolution of a species’ range by beneficial mutations". 

The organisers of this interesting conference has been kind enough to put up videos on the internet of Mark's talk, which you can find here, as well as two other interesting talks by contributors. This is an excellent way of making it possible for others, like us, who could not take part in this meeting, and also a very environmentally-friendly way of spreading scientific information without necessarily travelling to every meeting you wish to attend.

I suggest that we meet the usual time (13.30 on Wednesday April 15 in "Argumentet") to listen to Mark's talk, and (if we have time), to one or two of the other talks. Thus, there is no need to read any paper before this lab-meeting, just come sharp and alert and be willing to discuss! Hopefully, we can arrange with Machteld's computer to be linked to the Powerpoint-projector so we can see the talk on a large screen. 

 

Lab-meeting on the evolution of plasticity in changing environments

This Wednesday (January 11 2012), we will discuss a relatively recent theoretical and conceptual paper in PLoS Biology entitled "Adaptation, plasticity and extinction in a changing environment: towards a predictive theory".  You can download it here.


Although this paper was published as recently as in 2010, but has already received 79 citations - a sign of a quite an influential paper. This is not surprising as it connects such topics as climate change, thermal adaptation and niche modelling with the evolution of phenotypic plasticity - all very important and central topics in ecology and evoutionary biology. Below you will find the Abstract for the paper. One of the co-authors is legendary evolutionary quantitative geneticist Russel Lande, by the way.

Time: Wednesday, January 11, 2012
Place: "Argumentet"

 

Summary 

Many species are experiencing sustained environmental change mainly due to human activities. The unusual rate and extent of anthropogenic alterations of the environment may exceed the capacity of developmental, genetic, and demographic mechanisms that populations have evolved to deal with environmental change. To begin to understand the limits to population persistence, we present a simple evolutionary model for the critical rate of environmental change beyond which a population must decline and go extinct. We use this model to highlight the major determinants of extinction risk in a changing environment, and identify research needs for improved predictions based on projected changes in environmental variables. Two key parameters relating the environment to population biology have not yet received sufficient attention. Phenotypic plasticity, the direct influence of environment on the development of individual phenotypes, is increasingly considered an important component of phenotypic change in the wild and should be incorporated in models of population persistence. Environmental sensitivity of selection, the change in the optimum phenotype with the environment, still crucially needs empirical assessment. We use environmental tolerance curves and other examples of ecological and evolutionary responses to climate change to illustrate how these mechanistic approaches can be developed for predictive purposes.