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“The influence of non-random mating on population growth”

Fri, 07 Jun 2013 05:00:00 GMT

First two-sex model of population structured along continuous trait. Shows when non-random mating affects population growth

Size, sex and squirrels

The body size of an animal influences its survival, fertility, and mating chances. In addition, who is reproducing and with whom determines how a species evolves. Despite the important fact that body size and mating decisions shape the population and the course of evolution, there have been limited methods so far to study how both together affect population growth. A team of scientists from the UK, France, and Canada has developed a model that tracks body size evolution and allows the mating pattern to be changed. They studied the consequences of altering the mating behavior from random to non-random mating and analyzed the effect of the three most prominent departures from random mating. The first scenario is when mates tend to be of similar size, the second when they are very different in size, and the third when large males are preferred by all the females.

The scientists applied their model to the Columbian ground squirrel, as it is an ideal model species with plastic mating behavior which includes the potential for one of the three scenarios to occur. Interestingly, they found that the effect of the mating pattern alone on population growth rate is rather small. But the rate can be substantially affected when non-random mating co-occurs with sex differences. These findings are of great importance, since the majority of species shows sex differences, for instance when males live shorter lives, when females invest more energy into offspring, or when mothers have more influence on offspring’s phenotype than their fathers do. Researchers can now address these issues with the new model. Read the Article

“Bourgeois behavior and freeloading in the colonial orb-web spider Parawixia bistriata (Araneae, Araneidae)”

Fri, 07 Jun 2013 05:00:00 GMT

A team of scientists from six different nations has been making detailed field observations in southern Brazil on the fascinating social spider Parawixia bistriata. During the day, hundreds of these spiders doze quietly together in a bivouac, a soccer-ball-sized huddle of hundreds of spiders in a bush or tree. The bivouac sits at the centre of a network of thick silk lines which radiate out to adjacent trees and bushes. Things change dramatically at sunset. The spiders move out along the silk lines and build many adjacent orb webs, normally one per spider. Before daybreak, each spider consumes its own web and returns to the safety of the bivouac.

Darwin almost certainly observed this species while travelling overland in Argentina in October 1832, describing them in his Voyage of the Beagle as “many large black spiders, with ruby-colored marks on their backs, having gregarious habits.” After describing their adjacent individual webs attached to common lines, he went on to remark that “this gregarious habit, in so typical a genus as Epeira, among insects, which are so bloodthirsty and solitary that even the two sexes attack each other, is a very singular fact.”

Almost two centuries later, we now understand the spiders’ behavioral strategies that keep the peace and prevent these dangerous well-armed carnivores from getting into costly confrontations with their neighbors. Early in the evening, when there is still plenty of web-building space, spiders building their webs bounce up and down at potential intruders. Invariably, the intruder moves off, looking for its own vacant space within the network of permanent silk lines.

However, things change once all the potential web-building sites become occupied. Webless spiders now ignore a resident’s bounces and sit patiently at the web perimeter; they are occasionally rewarded by sneaking in to share a large insect prey with the resident. Modeled in terms of hawk-dove game theory, this switch in the behavioral strategy of webless spiders makes perfect sense. Early in the evening all spiders conventionally agree to respect the resident’s ownership because there is a high chance of finding a web-building site. Later on, when there is little chance of finding a web-building site, it is better to ignore the bouncing and hang around an existing web rather than search. But it is never worth fighting; one night’s food is not worth risking death for. The paper admirably combines traditional natural history observations with modern thinking about alternative behavioral strategies. Read the Article

“On the genetic architecture of cytoplasmic incompatibility: inference from phenotypic data”

Thu, 06 Jun 2013 05:00:00 GMT

This paper infers a parsimonious poison-antidote genetic interpretation of complex cytoplasmic incompatibility data

Numerous insects carry intracellular bacteria manipulating their reproduction and thus facilitating their own spread. Cytoplasmic incompatibility (CI) is a common form of such manipulation, where a (currently uncharacterized) bacterial modification of male sperm induces the early death of embryos unless the fertilized eggs carry the same bacteria, inherited from the mother. The death of uninfected embryos provides an indirect selective advantage to infected ones, thus enabling the spread of the bacteria. Here we use and expand recently developed algorithms to infer the genetic architecture underlying the complex incompatibility data from the mosquito Culex pipiens. We show that CI requires more genetic determinants than previously believed, and that quantitative variation in gene products potentially contributes to the observed CI patterns. In line with population genetic theory of CI, our analysis suggests that toxin factors (those inducing embryo death) are present in fewer copies in the bacterial genomes than antitoxin factors (those ensuring that infected embryos survive). In combination with comparative genomics, our approach will provide helpful guidance to identify the genetic basis of CI, and more generally of other toxin / anti-toxin systems that can be conceptualized under the same framework.

“Sex-specific fitness consequences of nutrient intake and the evolvability of diet preferences”

Thu, 06 Jun 2013 05:00:00 GMT

Well-adapted dietary preferences are fundamental in guiding an organism to acquire the best combination of nutrients available from their environment. In some species, feeding preferences for major macronutrients are poorly adapted to current environmental conditions. For example, in some human populations, attempts to consume a target amount of protein often result in the overconsumption of fat and carbohydrate, which in turn leads to obesity and its associated ill-health effects. While it is easy to imagine natural selection having optimized feeding preferences to match ancestral nutrient availabilities, it is unclear how readily feeding preferences can adapt to new conditions via natural selection. This question is not easily tested in long-lived vertebrates.

To address this question, Reddiex and colleagues study the feeding preferences of male and female fruit flies that have not been allowed to adapt to a novel food environment. Taking an integrative approach, they first determine the fitness consequences for males and females forced to feed on different blends of protein and carbohydrate. Second, they examine what males and females eat when able to choose freely between carbohydrate and protein. Interestingly, flies in the study prefer high-carbohydrate diets, neglecting their source of protein, which is essential for optimal fitness in both sexes. Together, these results suggest that feeding preferences are poorly adapted to the availability of nutrients in the population. By scoring the genotypes of the feeding flies, the researchers have been able to estimate how much genetic variation the population contains for feeding preferences to adapt via natural selection. Surprisingly, genotypes display quite varied preferences for protein and carbohydrate. The net result is that dietary preferences have substantial evolutionary potential—much higher than average—in this population. These results suggest that in populations where selection can operate, maladapted feeding may only be a relatively short-lived phenomenon. Read the Article

“Predators with multiple ontogenetic niche shifts have limited potential for population growth and top-down control of their prey”

Thu, 06 Jun 2013 05:00:00 GMT

Overfishing has brought fish populations to collapse, and some cod stocks have not recovered in twenty years. Even where fishing has diminished or been banned altogether, cod numbers have not necessarily been able to bounce back. Understanding the failure of these populations to recover goes to the core question in ecology: how do species interactions and food web structure affect ecosystem stability? Researchers from the Theoretical Ecology group at the University of Amsterdam and the Department of Aquatic Resources at the Swedish University of Agricultural Sciences falsify a popular hypothesis that is commonly postulated to explain the absence of cod recovery. The hypothesis postulated that competition for zooplankton between prey species and small (young) cod resulted in a self-enforcing mechanism: when there are plenty of cod, the large ones cull down the prey, allowing small cod to face reduced competition for zooplankton resources. When cod populations collapse, prey populations (the competitors of small-cod) boom. The increased density of prey may hamper the growth of small cod and therefore limit cod population recovery. Attractive as this explanation may be, it does not hold in a food web model where the scientists considered a third, intermediate, phase in the life history of cod. Cod individuals stop eating zooplankton and settle and forage on the sea bottom when they are about five centimeters in length—a life stage that is often ignored. Resource availability during this life stage is vital for predator population growth: Limitation of the resources that are essential in this life stage results in the creation of a growth bottleneck of the juvenile cod, preventing a large population biomass from building up. The observed patterns in the food web can therefore be explained by changes in the benthic environment, possibly resulting from the disturbance of sea-bottom fauna by fisheries activity. Read the Article

Webpage now up for the ASN Stand-alone Meeting

Wed, 05 Jun 2013 05:00:00 GMT

For information about the ASN stand-alone meeting in Asilomar, January 2014, check the webpage at http://w3.biosci.utexas.edu/amnatasilomar/

“Complex transient dynamics of stage-structured populations in response to environmental changes”

Wed, 05 Jun 2013 05:00:00 GMT

Nature changes continuously and is only seemingly at equilibrium. Temperature, humidity or insolation and other environmental parameters may strongly fluctuate on scales ranging from seconds to millions of years. As part of an ecosystem, species have to cope with these environmental changes. But how exactly does the environment influence the behavior of populations in transition? And how fast can populations recover from perturbations?

Thomas M. Massie and colleagues test for these questions using flow-through cultures (chemostats) of Chlorella vulgaris, a tiny green alga, and combine their experiments with a mathematical model including demographic structure. In the experiments as well as in the model, population structure arises from the interplay of algal cells with their growth-limiting resource, nitrogen. If nitrogen supply is constant, a population will attain a demographic steady state that allows cells to rush through their life cycle and reproduce quickly. Low nitrogen availability results in a low growth rate, which again results in a disproportionally large cohort of small and early-stage cells. Such populations show a significantly higher degree of synchrony than those with high nitrogen availability.

The researchers show that a population’s response to a change of the environment is basically determined by a population’s demographics before a change—especially the degree of synchrony. The more synchronized a population is before the perturbation, the stronger are the fluctuations caused by the changes of the population structure. Therefore, it takes the populations in general much longer to recover. In such transient conditions, a mechanism of otherwise minor importance becomes a decisive driver of population dynamics, namely resource-dependent cell size variability. An increase in resource concentration leads first to a dramatic decline in the number of cells before population increases to the new steady state. The explanation for this counter-intuitive behavior is given by the life-history strategy: If there are more resources, cells increase their individual size and fitness—but they do not reproduce, and the population declines due to mortality. An instant increase in the fitness of individuals might be disadvantageous for the entire population.

The study shows that demographic structure is a key to predicting transient behavior after environmental changes. Even minor environmental disturbances can cause changes in the population structure that alter population dynamics. Read the Article

“Environmental quality predicts optimal egg size in the wild”

Tue, 04 Jun 2013 05:00:00 GMT

In a perfect world, a parent would be able to produce many offspring and invest a great deal of time and energy caring for each offspring. In reality, however, parents don’t have infinite resources, so the number of offspring they produce must trade off against the care they can provide. One important evolutionary question, then, is how many offspring should a parent produce? Scientists have long suspected that the trade-off between parental care and family size depends on the environmental conditions that offspring are subjected to. When environmental conditions are adverse (e.g., the environment is too cold, or the predation risk is high), then the best strategy is for parents to produce a small family and invest heavily in parental care. But when environmental conditions are favorable, then the best strategy for parents is to avoid parental care and instead invest their energy in producing a very large family. An experiment performed by Canadian researchers provides long-awaited support for this theory. In the experiment, adult Atlantic salmon were mated in captivity, and the size of the eggs laid by each mother was measured. The bigger the egg, the more parental care the mother had provided to each offspring (i.e., energy given from the mother to the egg). Once the eggs hatched, the juvenile salmon were released into wild freshwater streams that differed in environmental conditions. Using DNA profiling, the researchers were able to measure which mothers produced the largest number of surviving juveniles in each environment. They were also able to tell how the amount of parental care (or energy) each juvenile received affected its chances of survival. As expected, the researchers found that as environmental conditions across streams got worse, the parents who did best were those that produced smaller families and provided more care to each offspring. Read the Article

“How does climate influence speciation?”

Tue, 04 Jun 2013 05:00:00 GMT

Researchers developed a mathematical model to examine the association between climatic niche evolution and speciation

Variation in climatic conditions over space and time is thought to be an important driver of speciation. However, the role of climate has not been explored in the theoretical literature on speciation, and the theory underlying empirical studies of climate and speciation has come largely from informal, verbal models. In this study, we develop a quantitative model in order to test a relatively new but theoretically untested model of speciation (speciation via niche conservatism) and to examine the climatic conditions under which speciation via niche conservatism versus niche divergence are most plausible. Our results have three broad implications for the study of speciation: (1) ecological similarity over time (niche conservatism) can be an important part of speciation, despite traditional emphasis on ecological divergence, (2) long-term directional climate change promotes speciation via niche conservatism for species with low climatic niche lability, whereas climatic oscillations promote speciation via niche divergence for species with high climatic niche lability, and (3) population extinction can be a key component of speciation. Read the Article

“Evolution of discrete phenotypes from continuous norms of reaction”

Mon, 03 Jun 2013 05:00:00 GMT

Evolution of discrete phenotypes from continuous norms of reaction

Discrete phenotypic variation often involves threshold expression of a trait with polygenic inheritance. How such discrete polyphenisms evolve starting from continuously varying phenotypes has received little theoretical attention. We model the evolution of sigmoid norms of reaction in response to variation in an underlying trait or in a continuous environment to identify conditions for the evolution of discontinuity. For traits with expression depending on a randomly varying underlying factor, such as developmental noise, polyphenism is unstable under constant phenotypic selection for 2 selective peaks, and reaction norm evolution results in a phenotypic distribution concentrated at only 1 peak. But with frequency-dependent selection between 2 adaptive peaks, a steep threshold maintaining polyphenism can evolve. For inducible plastic traits with expression conditioned on an environmental variable that also affects phenotypic selection, the steepness of the evolved reaction norm depends both on the differentiation of the environment in time or space and on its predictability between development and selection. Together with recent measurements of genetic variance of threshold steepness, these predictions suggest that quasi-discrete phenotypic variation may often evolve from continuous norms of reactions rather than being an intrinsic property of development.

“How individual movement response to habitat edges affects population persistence and spatial spread”

Mon, 03 Jun 2013 05:00:00 GMT

From movement behavior to invasion speeds in patchy landscapes: how behavior matters

How individual-level movement decisions in response to habitat edges influence population-level patterns of persistence and spread of a species is a major challenge in spatial ecology and conservation biology. Here, we integrate novel insights into edge behavior, based on habitat preference and movement rates, into spatially-explicit growth-dispersal models. We demonstrate how crucial ecological quantities (e.g. minimal patch size, spread rate) depend critically on these individual-level decisions. In particular, we find that including edge behavior properly into these models gives qualitatively different and intuitively more reasonable results than some previous studies that did not consider this level of detail. Our results highlights the importance of new empirical work on individual movement response to habitat edges. Read the Article

“Nowhere to run, nowhere to hide: The importance of enemies and apparency in adaptation to harsh soil environments”

Mon, 03 Jun 2013 05:00:00 GMT

Bare, simplified searching environments, often associated with sparsely vegetated harsh soils, may cause both plant and animal inhabitants to be apparent and conspicuous. “Apparency” has been a key concept to explain the diversity of plant defensive chemistry, but has been difficult to test. In animals, there is extensive work on camouflage and crypsis, adaptations to apparency that reduce detection by predators. Here, we explore apparency as a challenge in bare soil habitats characterized by sparse vegetative cover for both plants and animals. Using experiment and observation, we show that attack rates from enemies on vulnerable plants and undefended caterpillar models are greater in barer serpentine habitats than in adjacent more vegetated ones. Palatable Streptanthus species (Brassicaceae) may have adapted to apparency with a crypsis defense, typically considered the purview of animals. In S. breweri, leaf color is locally matched to soil outcrop color, and experimental mismatching of leaf and substrate color increases damage to plants, suggesting adaptation to apparency per se. Herbivore coloration may, too, have been influenced by greater enemy pressure and apparency in these sites. Adaptation to increased enemy pressure and apparency, with concomitant trade-offs in competitive ability, may be an underappreciated aspect of specialization to harsh soils, especially in plants. Apparency may be a useful framework for understanding trade-offs driving soil specialization and global biodiversity patterns. Read the Article

“Repeated parallel evolution reveals limiting similarity in subterranean diving beetles”

Mon, 03 Jun 2013 05:00:00 GMT

Evidence for self-organizing limiting similarity found in the body size structure of subterranean diving beetles

Five million years ago, climate change in Western Australia set up a truly remarkable, replicated natural experiment. Aridification led to the independent evolution of hundreds of species of blind water beetles in more than 50 isolated subterranean aquifers. The results of this evolution are striking: although each aquifer now has its own unique set of species, those species show the same body size pattern in all aquifers and fall into two or three distinct size classes. Ecologists have formulated different theories for species evolution. Notably, species that now inhabit natural communities could have evolved to adapt to their physical habitat, or alternatively to cope with the competition all living organisms exert on each other when sharing limited food or space. The repeated independent evolution of the water beetles presents a rare opportunity for simultaneously testing the ‘habitat’ and ‘competition’ theories. Evolutionary biologist Remko Leijs from the South Australian Museum (Australia) and theoretical ecologists Remi Vergnon, Egbert van Nes and Marten Scheffer from the University of Wageningen (Netherlands) use ecological modeling to show that the repeated size distribution patterns are the predictable outcomes of evolution driven by competition. The surprising take-home message of their study is that the starting material does not matter, because any mix of beetle ancestors will evolve through competition into similar patterns of distinct species groups. Competition is one of the fundamental engines of evolution, and the highly replicated emergence of subterranean water beetles communities has now led to a deeper understanding of this mechanism. Read the Article

“A quantitative genetic model of r- and K-selection in a fluctuating population”

Wed, 01 May 2013 05:00:00 GMT

Researchers present a general analysis of fluctuating density-dependent selection on a vector of quantitative characters

A stochastic quantitative genetic model for the joint dynamics of population size N and evolution of a multidimensional mean phenotype z-bar under density-dependent selection is analyzed. This generalizes our previous theories of evolution in uctuating environments to include density-dependent but frequency-independent selection on quantitative characters. We assume that appropriate constraints or trade-offs between fitness components exist to prevent unlimited increase of fitness. We also assume weak selection such that the expected rate of return to equilibrium is much slower for z-bar than N. The mean phenotype evolves to a stationary distribution around an equilibrium point z_opt maximizing a simple function determined by ecological parameters governing the dynamics of population size. For any z-bar the expected direction of phenotypic evolution is determined by the additive genetic covariance matrix G and the gradient of this function with respect to the mean phenotype. For the theta-logistic model of density dependence, evolution tends to maximize the expected value of N^θ. Read the Article

“Assortative mating in animals”

Wed, 01 May 2013 05:00:00 GMT

Do opposites attract? Not among many animal species. Researchers from the University of Texas at Austin analyzed published data on a total of 254 species, from earthworms to koalas, and concluded that in nature it is very common for animals to mate with individuals that are similar to themselves (“assortative mating”), rather than with opposites or at random. Mated pairs have been reported to resemble each other in a variety of characters, such as age, size, body condition, behavior, and certain genes. But just how similar are the members of a pair? The researchers looked at average similarity across all species and found it to be weak. These results hint that this tendency for like animals to pair with one another does not evolve because the offspring are more fit or attractive to mates. Instead, it is likely to arise because animals can only mate with other available mates. For example, strong males may scoop up the most desirable females, leaving the weaker ones to pair among themselves. This kind of mating is one way for one species to become two, because it isolates populations from one another. Getting a handle on just how common and strong assortative mating is helps evolutionary biologists better understand the origins of biodiversity. Despite these advances, it remains unknown why such mating is so common in nature and the attraction of opposites so rare. Read the Article

“Separating intrinsic and environmental contributions to growth and their population consequences”

Wed, 01 May 2013 05:00:00 GMT

Among-individual heterogeneity in growth is a commonly observed phenomenon that has clear consequences for population and community dynamics yet has proved difficult to quantify in practice. In particular observed among-individual variation in growth can be difficult to link to any given mechanism. Here we develop a Bayesian state-space framework for modeling growth that bridges the complexity of bioenergetic models and the statistical simplicity of phenomenological growth models. The model allows for intrinsic individual variation in traits, a shared environment, process stochasticity, and measurement error. We apply the model to two populations of steelhead trout (Oncorhynchus mykiss) grown under common but temporally varying food conditions. Models allowing for individual variation match available data better than models that assume a single shared trait for all individuals. Estimated individual variation translated into a ~2-fold range in realized growth rates within populations. Comparisons between populations showed strong differences in trait means, trait variability, and responses to a shared environment. Together, individual- and populationlevel variation have substantial implications for variation in size and growth rates among and within populations. State-dependent life history models predict this variation can lead to differences in individual life history expression, lifetime reproductive output, and population life history diversity. Read the Article

“Adaptive dynamics with interaction structure”

Wed, 01 May 2013 05:00:00 GMT

Evolutionary dynamics depend critically on a population’s interaction structure—the pattern of which individuals interact with which others, depending on the state of the population and the environment. Previous research has shown, for example, that cooperative behaviors disfavored in well-mixed populations can be favored when interactions occur only between spatial neighbors or group members. Combining the adaptive dynamics approach with recent advances in evolutionary game theory, we here introduce a general mathematical framework for analyzing the long-term evolution of continuous game strategies for a broad class of evolutionary models, encompassing many varieties of interaction structure. Our main result, the canonical equation of adaptive dynamics with interaction structure, characterizes expected evolutionary trajectories resulting from any such model, thereby generalizing a central tool of adaptive dynamics theory. Interestingly, the effects of different interaction structures and update rules on evolutionary trajectories are fully captured by just two real numbers associated with each model, which are independent of the considered game. The first, a structure coefficient, quantifies the effects on selection pressures and thus on the shapes of expected evolutionary trajectories. The second, an effective population size, quantifies the effects on selection responses and thus on the expected rates of adaptation. Applying our results to two social dilemmas, we show how the range of evolutionarily stable cooperative behaviors systematically varies with a model’s structure coefficient. Read the Article

“Choosy males could help explain androdioecy in a selfing fish”

Wed, 01 May 2013 05:00:00 GMT

Sexual selection was first discussed by Darwin, quickly becoming a highly controversial topic. In most species females are the “choosy” sex because they tend to invest more in reproduction, while males fight to get access to as many females as possible. However, in some species it is not so clear. Sometimes individuals that are of both sexes (hermaphrodites) can self-fertilize, although they also coexist with pure males—a situation called androdioecy. In such populations, males tend to be present at very low frequencies. But males must have some advantage, as in theory hermaphrodites could do without them. Why and how males coexist with hermaphrodites is a big unanswered question that Sonia Consuegra and her group at Aberystwyth University are investigating, using a very unique species as a model, the mangrove killifish (Kryptolebias marmoratus).

This unique fish can self-fertilize and its populations are made up of hermaphrodites and males, the latter only present at low frequency. But hermaphrodites cannot outcross with each other, only with the males, and outcrossing with males increases genetic diversity and parasite resistance in the offspring. One could thus expect that the hermaphrodites would prefer unrelated males, genetically different from themselves, in order to have diverse and healthy offspring. At Aberystwyth, Amy Ellison, now a post-doc at Cornell University, and two final-year undergraduates studied the preferences of males and hermaphrodites for individuals with different degrees of relatedness.

Surprisingly, although sexually mature hermaphrodites preferred to associate with males than with other hermaphrodites, they did not show a preference for the genetic background of the males. In contrast, males displayed a strong preference for genetically different hermaphrodites, suggesting that males could be the drivers of the mate choice in this androdioecious species. Thus, according to this study, male mate choice could be a critical factor for the coexistence of males and hermaphrodites in cases when self-fertilization is associated with inbreeding depression. Read the Article

“Differences in speed and duration of bird migration between spring and autumn”

Wed, 01 May 2013 05:00:00 GMT

Ornithologists have long discussed whether and to what degree birds might migrate faster in spring than in autumn because of competition for early arrival at breeding grounds. Researchers at Lund University in Sweden decided to use the rapidly increasing number of studies that track migrating birds to test this. They looked at over 70 studies where migrating birds were tracked during both spring (towards the breeding grounds) and autumn (away from the breeding grounds).

The pattern that emerges is striking: there is a clear dominance of cases where spring migration is faster than autumn migration—in flight speed, stopover duration as well as total migration speed. This suggests that spring and autumn migrations often constitute quite different evolutionary processes, involving different main selection pressures and adaptive solutions during the two seasons. Competition for prior occupancy of breeding resources could result in a race to the breeding grounds in spring, but there could also be environmental effects that make the spring journey easier and therefore faster. Increased migration speed in spring is one way birds are predicted to deal with a warmer climate, but if spring migration speed is already at its limit, this might not be possible. “We hope that this summary will open up the question of differences between spring and autumn migration and inspire critical tests of what determines migration speed,” says lead author Cecilia Nilsson from the bird migration group at Lund University. Read the Article

“Tradeoffs, geography and limits to thermal adaptation in a tidepool copepod”

Wed, 01 May 2013 05:00:00 GMT

Antagonistic correlations among traits may slow the rate of adaptation to a changing environment. The tidepool copepod Tigriopus californicus is locally adapted to temperature, but within populations the response to selection for increased heat tolerance plateaus rapidly, suggesting either limited variation within populations, or costs to increased tolerance. To measure possible costs of thermal tolerance, we selected for increased upper lethal limits for ten generations in 22 lines of T. californicus from six populations. Then for each line, we measured six fitness-related traits. Selected lines showed an overall increase in male and female body size, fecundity and starvation resistance, suggesting a small benefit, rather than a cost to increased tolerance. The effect of selection on correlated traits also varied significantly by population for five traits, indicating that the genetic basis for the selection response differed among populations. Our results suggest that adaptation was limited by the presence of variation within isolated populations, rather than costs of increased tolerance. Read the Article

NESCent Workshop on Evolutionary Quantitative Genetics co-sponsored by ASN

Mon, 29 Apr 2013 05:00:00 GMT

In this workshop we will review the basics of theory in the field of evolutionary quantitative genetics and its connections to evolution that is observed at various time scales. Quantitative genetics deals with the inheritance of measurements of traits that are affected by many genes. Quantitative genetic theory for natural populations was developed considerably in the period 1970-90 and up to the present time. It has been applied to a wide range of phenomena including the evolution of differences between the sexes, sexual preferences, life history traits, plasticity of traits, as well as the evolution of body size and other morphological measurements. Textbooks have not kept pace with these developments, and currently few universities offer courses in this subject aimed at evolutionary biologists. There is a need for evolutionary biologists to understand this field because of the ability to collect large amounts of data by computer, the development of statistical methods for changes of traits on evolutionary trees and for changes in a single species through time, and the realization that quantitative characters will not soon be fully explained by genomics. This workshop aims to fill this need by reviewing basic aspects of theory and illustrating how that theory can be tested with data. Participants will learn to use R, an open-source statistical programming language, to build and test evolutionary models. The intended participants for this workshop are graduate students, postdocs, and junior faculty members in evolutionary biology.

The course will run from August 5-10, 2013 at the National Evolutionary Synthesis Center (NESCent) in Durham, NC.

Tuition will be $400 (with reduced tuition for participants who are members of the American Society of Naturalists. Participants are responsible for their own travel costs, including transportation and accommodation. A limited number of travel scholarships from NESCent are available for US-based participants. Preference will be given to participants from under-represented minorities.

Online application form

If you aren't already, you can join the ASN for the opportunity to receive reduced tuition (limited number available: first come, first served).

More information here.