Machiavellian robots will kill us all

This is roughly analogous to some of the stuff we've been talking with Jeremy about doing with bacteria...

The evolution of information suppression in communicating robots with conflicting interests

Sara Mitri, Dario Floreano, and Laurent Keller

Published online before print September 3, 2009, doi: 10.1073/pnas.0903152106

Abstract

Reliable information is a crucial factor influencing decision-making and, thus, fitness in all animals. A common source of information comes from inadvertent cues produced by the behavior of conspecifics. Here we use a system of experimental evolution with robots foraging in an arena containing a food source to study how communication strategies can evolve to regulate information provided by such cues. The robots could produce information by emitting blue light, which the other robots could perceive with their cameras. Over the first few generations, the robots quickly evolved to successfully locate the food, while emitting light randomly. This behavior resulted in a high intensity of light near food, which provided social information allowing other robots to more rapidly find the food. Because robots were competing for food, they were quickly selected to conceal this information. However, they never completely ceased to produce information. Detailed analyses revealed that this somewhat surprising result was due to the strength of selection on suppressing information declining concomitantly with the reduction in information content. Accordingly, a stable equilibrium with low information and considerable variation in communicative behaviors was attained by mutation selection. Because a similar coevolutionary process should be common in natural systems, this may explain why communicative strategies are so variable in many animal species.

Movement signal choreography unaffected by receiver distance in the Australian Jacky lizard, Amphibolurus muricatus

Richard A. Peters and Simon J. Allen - Behavioral Ecology and Sociobiology, 69: 11, pp 1593-1602

Abstract
Theory explains the structure of animal signals in the context of the receiver sensory systems, the environment through which signals travel and their information content. The influence of signalling context on movement-based signalling strategies is becoming clearer. Building upon recent findings that demonstrated changing environmental plant motion conditions resulted in a change of signalling strategy by the Australian lizard Amphibolurus muricatus, we examined whether receiver distance also influences signalling strategies. We found that signalling lizards did not modify their introductory tail flicking in response to distant viewers in the absence of competing, irrelevant plant image motion despite significant reductions in signal structure at the eye of the viewer. The magnitude of resultant effect sizes strongly suggests that receiver distance does not contribute to signalling strategies as much as the presence of motion noise in the environment.

Here

TRANSGENERATIONAL EPIGENETIC INHERITANCE: PREVALENCE, MECHANISMS, AND IMPLICATIONS FOR THE STUDY OF HEREDITY AND EVOLUTION

Eva Jablonka and Gal Raz

Quarterly Review of Biology Vol. 84 No. 2 June 2009


Ok so this doesn't have anything to do directly with fish, but it is an excellent review article that outlines the key elements of a transgenerational mechanism that might have interesting implications for sexual selection.


Abstract: This review describes new developments in the study of transgenerational epigenetic inheritance, a component of epigenetics. We start by examining the basic concepts of the field and the mechanisms that underlie epigenetic inheritance. We present a comprehensive review of transgenerational cellular epigenetic inheritance among different taxa in the form of a table, and discuss the data contained therein. The analysis of these data shows that epigenetic inheritance is ubiquitous and suggests lines of research that go beyond present approaches to the subject. We conclude by exploring some of the consequences of epigenetic inheritance for the study of evolution, while also pointing to the importance of recognizing and understanding epigenetic inheritance for practical and theoretical issues in biology.

The evolutionary origins of beneficial alleles during the repeated adaptation of garter snakes to deadly prey

Feldman et al., PNAS
A very cool story about adaptation at the amino acid level.

Age in influences life history traits in gulls.

This is the type of empirical variation that gets me excited...although of course many details are left out. I wonder what type of mating system they have here?

Effects of parental age and food availability on the reproductive success of Heermann's Gulls in the Gulf of California

Ecology, August 2009

Abstract

Parental age, body condition, and food availability have been found to influence breeding parameters in seabirds, such as clutch size, number of chicks hatched and fledged, hatching, fledging, and reproductive success. In this paper we analyze the influence of parental age and body condition estimated by body mass, and food availability estimated from catch per unit effort (CPUE) statistics for Pacific sardine (Sardinops caeruleus) + northern anchovy (Engraulis mordax) by the local fishing fleet, on the breeding parameters of the Heermann's Gull (Larus heermanni; a vulnerable species according to Mexican federal law) nesting in Isla Rasa, Gulf of California, Mexico. Results are based on data from 1123 recaptures of known-age individuals, ranging from 4 to 13 years of age, during seven observation years between 1989 and 1997. Ages of mated male and female gulls were positively correlated. Breeding parameters showed their lowest values in 1992, an El Niño year in which the birds also showed significantly lower individual masses for both males and females, and in which the local CPUE of sardine + anchovies was lowest. All breeding parameters increased significantly with parental age and were highest at 10–12 years. No significant statistical interactions were found between food availability and parental age on the breeding parameters. Through a path analysis we found that there is a strong chained relationship between variables: food availability, which is strongly driven by oceanographic conditions, affects both the survival of eggs into hatchlings and the survival of hatchlings into fledglings. This external factor and parental age, a biological factor intrinsic to each nesting couple, explain 41% of the observed between-nest variation in fledgling success.

A hybrid zone revisited: molecular and morphological analysis of the maintenance, movement, and evolution of a Great Plains avian (Cardinalidae: Pheuc

R. D. METTLER and G. M. SPELLMAN

KEYWORDS
Great Plains • hybrid zone • mitochondrial DNA • nuclear loci • Pheucticus • tension zone

ABSTRACT

Black-headed grosbeaks (Pheucticus melanocephalus) and rose-breasted grosbeaks (Pheucticus ludovicianus) are passerine bird species known to hybridize in the Great Plains of North America. Both extrinsic (environmental) and intrinsic factors (pre- and postzygotic reproductive isolation) have been credited for the generation and maintenance of the grosbeak hybrid zone, but little is known about the genetic characteristics of this hybrid zone. To investigate the stability and extent of the grosbeak hybrid zone, we constructed clines from both molecular sequence data (mtDNA, three autosomal intron loci, and one Z-linked locus) and morphological data (morphometric analyses and hybrid index scores) to determined zone centre and width. Hybrid zone centre and width were also determined for samples collected across the zone 40 years ago from morphological data. The present and past clines were compared and provided support for stability in hybrid zone location and width, and the evolutionary implications of this are discussed. Three models of hybrid zone maintenance were investigated to consider the influence of intrinsic and extrinsic factors on this zone. Our results suggest low hybrid frequencies, a stable zone location and narrow width, and reduced hybrid fitness over the past 40 years best categorize the grosbeak hybrid zone as a tension zone.

http://www3.interscience.wiley.com/journal/122505418/abstract

Morphology, performance, fitness:

Functional insight into a post-Pleistocene radiation of mosquitofish

R. Brian Langerhans*
Biology Letters 2009;5 488-491

Bahamas mosquitofish (Gambusia hubbsi) colonized blue holes during the past approximately 15 000 years and exhibit relatively larger caudal regions in blue holes that contain piscivorous fish. It is hypothesized that larger caudal regions enhance fast-start escape performance and thus reflect an adaptation for avoiding predation. Here I test this hypothesis using a three-pronged, experimental approach. First, G. hubbsi from blue holes with predators were found to possess both greater fast-start performance and greater survivorship in the presence of predatory fish. Second, using individual-level data to investigate the morphology–performance–fitness pathway, I found that (i) fish with larger caudal regions produced higher fast-start performance and (ii) fish with higher fast-start performance enjoyed greater survivorship in the presence of fish predators—trends consistently observed across both predator regimes. Finally, I found that morphological divergence between predator regimes at least partially reflects genetic differentiation, as differences were retained in fish raised in a common laboratory environment. These results suggest that natural selection favours increased fast-start performance in the presence of piscivorous fish, consequently driving the evolution of larger caudal regions. Combined with previous work, this provides functional insight into body shape divergence and ecological speciation among Bahamian blue holes.

PNAS special issue on Darwin

Check out the June 16 issue of PNAS: In the Light of Evolution III: Two Centuries of Darwin Sackler Colloquium. Lots of good stuff here, including Nick and Adam's paper on sexual selection, genomics of ecological speciation, etc. Looking forward to more posts as everyone comes back to higher bandwidth!

Ecological context shapes hybridization dynamics

Molecular Ecology (Volume 18 Issue 10, Pages 2077 - 2079)

PERSPECTIVE
Ecological context shapes hybridization dynamics

C. ALEX BUERKLE

ABSTRACT

Gene exchange among oak species (Quercus) in Europe is known to be pervasive and to complicate population genetic studies of this species complex. A study in this issue of Molecular Ecology adds geographical and stand-level resolution to the patterns of genetic variation among four species and documents the relatively high frequency of hybrids (10.7–30.5% of trees in a population, including hybrids between all pairs of species; Lepais et al. 2009). In addition, the authors show that the relative abundance of parental species affects the genetic composition of hybrids and shifts the average direction of introgression. Variation in the relative abundance of parental species is one example of how the ecological context of hybridization can influence the dynamics and outcome of contact between species and represents an opportunity to investigate the components of reproductive isolation between species. This research raises several questions about the dynamics of hybridization in this well-studied species complex, and highlights methodological and conceptual issues associated with contemporary research on hybridization.

The impact of environmental heterogeneity on genetic architecture in a wild population of Soay sheep

Matthew R. Robinson, AJ Wilson, JG Pilkington TH Clutton-Brock, JM Pemberton and LEB Kruuk.
Genetics 181: 1639-1648

Finally a paper in Genetics that I can understand, and it presents an intriguing idea. It caught my eye, because a friend of mine recently asked me if I knew of any examples of sexual dimorphism driven by natural selection. I couldn't think of any, at that time, and also was wondering how that could work. Well... this is perhaps how. From the giant database of the Soay sheep on that cold and windswept island of St Kilda. Be aware of complicated stats...


This work demonstrates that environmental conditions experienced by individuals can shape their development and affect the stability of genetic associations. The implication of this observation is that the environmental response may influence the evolution of traits in the wild. Here, we examined how the genetic architecture of a suite of sexually dimorphic traits changed as a function of environmental conditions in an unmanaged population of Soay sheep (Ovis aries) on the island of Hirta, St. Kilda, northwest Scotland. We examined the stability of phenotypic, genetic, and environmental (residual) covariance in males during the first year of life between horn length, body weight, and parasite load in environments of different quality. We then examined the same covariance structures across environments within and between the adult sexes. We found significant genotype-by-environment interactions for lamb male body weight and parasite load, leading to a change in the genetic correlation among environments. Horn length was genetically correlated with body weight in males but not females and the genetic correlation among traits within and between the sexes was dependent upon the environmental conditions experienced during adulthood. Genetic correlations were smaller in more favorable environmental conditions, suggesting that in good environments, loci are expressed that have sex-specific effects. The reduction in genetic correlation between the sexes may allow independent evolutionary trajectories for each sex. This study demonstrates that the genetic architecture of traits is not stable under temporally varying environments and highlights the fact that evolutionary processes may depend largely upon ecological conditions.

Alternative mating strategies may favour the persistence of a genetically based colour polymorphism in a pentamorphic fish

Jorge L. Hurtado-Gonzales and J. Albert C. Uy


Males of the pentamorphic fish, Poecilia parae, show a striking colour polymorphism that ranges from drab coloration resembling females to brilliant black and red stripes. We tested the hypothesis that the observed polymorphism may persist because each morph uses a unique but equally successful mating strategy. We quantified the mating behaviour, testes investment and sperm morphometrics of each morph. We found that the smallest morph (immaculata), which resembles drab females, used a ‘sneaker’ tactic (i.e. forgoing courtship and mostly ‘stealing’ copulations) as a mating strategy. Immaculata males also had larger testes, and produced larger ejaculates and sperm with longer flagella, which should provide advantages during sperm competition. The largest morph (parae) and the coloured blue, red and yellow morphs used a combination of courtship and sneaker tactics. However, they achieved greater copulation success as a result of courtships. The testes investment of parae and yellow morphs were similar but larger than those of the blue and red males. Our results suggest that male morphs of the pentamorphic Poecilia parae use unique mating strategies that exploit different aspects of pre- and postcopulatory sexual selection, which, in turn, may help maintain their relatively stable frequencies in the wild.

Keywords: alternative mating strategy; frequency-dependent selection; genetic polymorphism; Poecilia parae; sperm competition

link from campus

Sex chromosome evolution

Accelerated Adaptive Evolution on a Newly Formed X Chromosome Bachtrog D, Jensen JD, Zhang Z PLoS Biology Vol. 7, No. 4, e82 doi:10.1371/journal.pbio.1000082

I'm finally getting back on this after my computer crash. Where is everybody?

Multiple paternity and offspring quality in tree swallows

Another study looking for good genes that instead found some mysterious "environmental" benefit of extra pair mating...

Peter O. Dunn, Jan T. Lifjeld and Linda A. Whittingham


There is mounting evidence in a variety of taxa that females increase offspring quality by mating with multiple males, often resulting in multiple paternity. In birds, however, few studies have explicitly examined the benefits of mating with several different males; instead, the focus has been on whether or not extra-pair mating occurs, and its adaptive significance remains controversial. We examined the hypothesis that offspring quality, particularly immune response (phytohaemagglutinin assay) and growth, increases with the number of sires in broods of socially monogamous tree swallows (Tachycineta bicolor). We found one of the highest known levels of multiple paternity in birds (84% of nests with two or more extra-pair young had at least two extra-pair sires). Among nests with extra-pair young, the number and diversity of sires continued to increase linearly with the number of extra-pair young, so there was no evidence that some males monopolized paternity at high levels of extra-pair fertilization. Indeed, the number of sires was actually greater than expected in large broods, suggesting that some females might be seeking more mates. We found no effect of the number of sires on nestling immune response or growth. In mixed paternity broods, the immune response of extra-pair young did not differ from that of their within-pair half-siblings. However, among all broods, nestlings had a stronger immune response in nests with at least one extra-pair nestling than in nests with all within-pair nestlings. These results are not consistent with a good genes benefit of extra-pair mating, but they do suggest that there are environmental effects associated with extra-pair mating that increase nestling immune response. These environmental effects could produce indirect genetic effects on sexual selection if they are heritable. The extraordinarily high number of sires in this species highlights a relatively unexplored source of sexual selection in birds.

Theoretical predictions strongly support decision accuracy as a major driver of ecological specialization

1. Colin R. Tosh, Jens Krause and Graeme D. Ruxton

We examine the proposal that the high levels of ecological specialization seen in many animals has been driven by benefits in decision accuracy that accrue from this resource-use strategy. Using artificial analogs of real neural processing (artificial neural networks), we examine the relationship between decision accuracy, level of ecological specialization/generalization, and the punishment/reward for selecting non-host resources. We demonstrate that specialists make more accurate resource-use decisions than generalists when the consequences of using a non-host are neutral or positive but not very positive. Pronounced unsuitability of non-host resources in fact promotes higher decision accuracy in generalists. These unusual predictions can be explained by the special properties of neural processing systems and are entirely consistent with patterns of performance of many specialists in nature, where non-used resources are, curiously, often quite suitable for growth and reproduction. They potentially reconcile the long-observed discrepancy between the presence of high levels of ecological specialization in many animal groups and the absence of strong negative fitness correlations across resources. The strong theoretical support obtained here, and the equally good support in experimental studies elsewhere, should bring the “neural limitations” hypothesis to the forefront of research on the evolutionary determinants of ecological range.

http://www.pnas.org/content/early/2009/03/20/0807247106.abstract?etoc

Physiological Stress Mediates the Honesty of Social Signals

Why can't I get more excited about condition-depending signaling in birds? The entire literature leaves me cold for some reason.

We analyzed corticosterone deposited in growing feathers as an integrated measure of hypothalamic-pituitary-adrenal activity in a wild territorial bird, the red grouse Lagopus lagopus scoticus. We manipulated two key, interrelated components, parasites and testosterone, which influence both ornamentation and fitness. Birds were initially purged of parasites, and later challenged with parasites or not, while at the same time being given testosterone or control implants, using a factorial experimental design. At the treatment level, testosterone enhanced ornamentation, while parasites reduced it, but only in males not implanted with testosterone. Among individuals, the degree to which both parasites and testosterone had an effect was strongly dependent on the amount of corticosterone in the feather grown during the experiment. The more stressors birds had experienced (i.e., higher corticosterone), the more parasites developed, and the less testosterone enhanced ornamentation.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0004983

Spatial effects on preference evolution

This is a continuous-time spatial version of the basic model of Pomiankowski et al. (1991). Day starts out by saying that no models show that costly preferences can not evolve, which is not entirely accurate. He published in 2000, and there are ~ 5 different models showing that costly preferences can evolve. Nevertheless, the results show that preferences can evolve when traits are distributed spatially due to different naturally selected optima. I thought that this could be of some use to you swordtail people. I am interested to see if your data coincide with Day's predictons. There is a ton of advanced math, but the figures do a good job summing up the results.

Enjoy!

SEXUAL SELECTION AND THE EVOLUTION OF COSTLY FEMALE PREFERENCES: SPATIAL EFFECTS

Troy Day ^{1 1}

¹ Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada

¹ Present address: Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada; E-mail: dayt@zoo.utoronto.ca.

Abstract.—Models of Fisher's runaway process show that if there is a cost to female preference, no preference or male trait exaggeration will evolve. Surprisingly, this is true no matter how small the cost, which reveals that these models of Fisher's process are structurally unstable (Bulmer 1989). Here a model of Fisher's runaway process is presented to demonstrate that costly female preference evolves very easily when space is explicitly included in the model. The only requirement is that the optimal male phenotype changes across the species' range. The model shows that the spatial average of the female preference and male trait reach an evolutionary equilibrium that is identical to those of nonspatial models, but that the preference and male trait can deviate greatly from these averages at any point in space. For example, if random mating results in the lowest cost to females, then at equilibrium the spatial average preference will be zero. Nevertheless, there will be some locations at which females prefer males with larger ornaments and others where they prefer males with smaller ornaments. Results also show that the structural instability of nonspatial models of Fisher's process is less of a problem in spatial models. In particular, many of the main qualitative features of cost-free spatial models of Fisher's process remain valid even when there are small costs of female preference. Finally, the model shows that abrupt changes in the optimal male phenotype across space can result in an amplification of this pattern when preference has a small cost, but it can also result in a pattern similar to reproductive character displacement. Which of these occurs depends on the magnitude of the cost of female preference. This suggests that some patterns of reproductive character displacement in nature might be explained simply by sexual selection rather than by hybrid dysgenesis and reinforcement.

Production and perception of communicatory signals in a noisy environment

David A Luther* and R. Haven Wiley 2009 Biology Letters vol. 5 no. 2 183-187


Many animals communicate in situations that make it difficult to discriminate a species' signals from those of others. Consequently, coexisting species usually have signals that differ by more than the minimum required to prevent overlap in acoustic features. These gaps between signals might facilitate detection and discrimination of degraded signals in noisy natural conditions. If so, perception of signals should have broader scope than production. We investigated this possibility by studying song production and perception of two species of birds in an especially noisy environment, the Amazonian dawn chorus. With software developed for this study, we digitally synthesized songs of two species, as well as intermediate versions of their songs. Experimental playbacks of these synthesized songs to individuals of both species confirmed that perception (as indicated by responses) was broader than production of songs. We propose that broader perception than production of song promotes communication in noisy situations and limits the similarity between signals of coexisting species.

So this seems relevant, in the sense that they address the evolution of species recognition cues in a a noisy background. Except the authors don't try to put their findings along work done on signal evolution in other environments or types of signals, which is too bad.

The impact of human-made ecological changes on the genetic architecture of Daphnia species

1. Nora Brede^a,^b,¹,
2. Christoph Sandrock^a,²,
3. Dietmar Straile^c,
4. Piet Spaak^b,^d,
5. Thomas Jankowski^c,³,
6. Bruno Streit^a and
7. Klaus Schwenk^a,¹⁴

+Author Affiliations

1. ^aDepartment of Ecology and Evolution, Goethe-University Frankfurt am Main, Siesmayerstrasse 70, D-60054 Frankfurt am Main, Germany;
2. ^cLimnological Institute, University of Konstanz, D-75457 Konstanz, Germany;
3. ^bEawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland; and
4. ^dInstitute of Integrative Biology, ETH Zürich, CH-8092 Zürich, Switzerland

1. ↵¹N.B. and K.S. contributed equally to this work.

2. Edited by Nelson G. Hairston, Cornell University, Ithaca, NY, and accepted by the Editorial Board February 2, 2009 (received for review July 24, 2008)

Abstract

The overenrichment (eutrophication) of aquatic ecosystems with nutrients leading to algal blooms and anoxic conditions has been a persistent and widespread environmental problem. Although there are many studies on the ecological impact of elevated phosphorus (P) levels (e.g., decrease in biodiversity and water quality), little is known about the evolutionary consequences for animal species. We reconstructed the genetic architecture of a Daphnia species complex in 2 European lakes using diapausing eggs that were isolated from sediment layers covering the past 100 years. Changes in total P were clearly associated with a shift in species composition and the population structure of evolutionary lineages. Although environmental conditions were largely re-established after peak eutrophication during the 1970s and 1980s, original species composition and the genetic architecture of species were not restored but evolved along new evolutionary trajectories. Our data demonstrate that anthropogenically induced temporal alterations of habitats are associated with long-lasting changes in communities and species via interspecific hybridization and introgression.

Cognitive and neural foundations of religious belief - PNAS Early Edition

Dimitrios Kapogiannis^a,^b,Aron K. Barbey^a,^c,Michael Su^a,Giovanna Zamboni^a,Frank Krueger^a andJordan Grafman^a,¹

+Author Affiliations

1. ^aNational Institute of Neurological Disorders and Stroke/National Institutes of Health, MSC 1440, 10 Center Drive, MSC 1440, Bethesda, MD 20892-1440;
2. ^bNational Institute on Aging/National Institutes of Health, 3001 South Hanover Avenue, Baltimore, MD 21225; and
3. ^cDepartment of Psychology, Georgetown University, White-Gravenor Hall 306, 37th and O Street NW, Washington, D.C. 20057

1. Edited by Marcus E. Raichle, Washington University School of Medicine, St. Louis, MO, and approved February 3, 2009 (received for review November 17, 2008)

We propose an integrative cognitive neuroscience framework for understanding the cognitive and neural foundations of religious belief. Our analysis reveals 3 principle psychological dimensions of religious belief (God's perceived level of involvement, God's perceived emotion, and doctrinal/experiential religious knowledge), which functional MRI localizes within networks processing Theory of Mind regarding intent and emotion, abstract semantics, and imagery. Our results are unique in demonstrating that specific components of religious belief are mediated by well-known brain networks, and support contemporary psychological theories that ground religious belief within evolutionary adaptive cognitive functions.

--------------------------

I haven't read the paper yet but at first blush this reinforces my belief that much of the fMRI stuff is latter-day phrenology. Why does a "well-known brain network" imply "evolutionarily adaptive cognitive functions"? The clitoris is a "well-known sexual organ" yet does not produce any "evolutionarily adaptive reproductive functions". Plus they misspelled "principal" in PNAS.

Variability in Sensory Ecology: Expanding the Bridge Between Physiology and Evolutionary Biology

The Quarterly Review of Biology

March 2009, vol. 84, no. 1



OLIVIER DANGLES and DUNCAN IRSCHICK and LARS CHITTKA and JEROME CASAS


ABSTRACT
Sensory organs represent the interface between the central nervous system of organisms and the environment in which they live. To date, we still lack a true integration of ecological and evolutionary perspectives in our understanding of many sensory systems. We argue that scientists working in sensory ecology should expand the bridge between sensory and evolutionary biology, and, in working toward this goal, we advocate a combination of the experimental rigor of the sensory physiologist with population-based as well as evolutionary views.

__________________________________________________________________


In short, they are giving reasons why studying sensory systems will tell us more about evolutionary outcomes such as speciation, sexual selection, and variable behavior. In their own words:

"The investigation of variation in the performance of sensory systems among species, populations, and developmental stages, especially under natural conditions, represents a promising field of research that may serve not only to refine our understanding of the past evolution of sensory systems, but also to predict how animal behavior and sensory capabilities will continue to adapt to a changing world." (pg. 65)

A powerful regression-based method for admixture mapping of isolation across the genome of hybrids

Molecular Ecology

Volume 18, Issue 6, Pages 1207 - 1224

ZACHARIAH GOMPERT and C. ALEX BUERKLE


We propose a novel method that uses natural admixture between divergent lineages (hybridization) to investigate the genetic architecture of reproductive isolation and adaptive introgression. Our method employs multinomial regression to estimate genomic clines and to quantify introgression for individual loci relative to the genomic background (clines in genotype frequency along a genomic admixture gradient). Loci with patterns of introgression that deviate significantly from null expectations based on the remainder of the genome are potentially subject to selection and thus of interest to understanding adaptation and the evolution of reproductive isolation. Using simulations, we show that different forms of selection modify these genomic clines in predictable ways and that our method has good power to detect moderate to strong selection for multiple forms of selection. Using individual-based simulations, we demonstrate that our method generally has a low false positive rate, except when genetic drift is particularly pronounced (e.g. low population size, low migration rates from parental populations, and substantial time since initial admixture). Additional individual-based simulations reveal that moderate selection against heterozygotes can be detected as much as 50 cm away from the focal locus directly experiencing selection, but is not detected at unlinked loci. Finally, we apply our analytical method to previously published data sets from a mouse (Mus musculus and M. domesticus) and two sunflower (Helianthus petiolaris and H. annuus) hybrid zones. This method should be applicable to numerous species that are currently the focus of research in evolution and ecology and should help bring about new insights regarding the processes underlying the origin and maintenance of biological diversity.

Condition-dependent female remating resistance generates sexual selection on male size in a ladybird beetle

"Condition-dependent female remating resistance generates sexual selection on male size in a ladybird beetle"

Animal Behavior
Volume 77, Issue 3, March 2009, Pages 743-748

Jennifer C. Perry, Diana M.T. Sharpe and Locke Rowe


Behavioural resistance to remating by females is common, but the causes and consequences of resistance are rarely explained. Prominent hypotheses include resistance as a means of avoiding costly and superfluous mating, or as a means of biasing mating towards high-quality males. In species in which males produce nutritious nuptial gifts, females may further modulate resistance according to their need for nutrition. We investigated these hypotheses in the ladybeetle Adalia bipunctata, in which females frequently display vigorous resistance before copulation and ingest a spermatophore after copulation. In two experiments, we manipulated female nutritional state, depriving or satiating females for a short (16 h) or long (96 h) interval before a remating trial. We found that food-deprived females resisted mating more frequently and for longer periods than satiated females and consequently remated less frequently. This condition dependence of resistance supports the hypothesis that resistance functions to reduce superfluous and costly mating. Our finding that food-deprived females were more resistant suggests that mating imposes energetic costs, and that nuptial feeding does not offset these costs. In a third experiment, we investigated whether the extent of resistance depended on male size or whether resistance itself biased mating towards large males. The extent of female resistance was independent of male size, but resistance itself resulted in a mating bias towards large males. In summary, our results support the hypotheses that females resist mating simply because it is costly and superfluous, and that a side effect of resistance is sexual selection for large male size.

Genetic distance predicts the amount of transgressive segregation

When species hybridize, their genetic material recombines, and they can produce offspring with phenotypes that surpass those of their parents. Is this 'transgressive segregation' predictable? There is a phylogenetic component to certain traits or trait combinations being fixed in populations or species complexes. So when more similar species hybridize the extent of transgressive segregation should be less than when more distant species hybridize. This is indeed what the authors find in their litterature survey of reports of transgressive seggregation.

Stelkens RB & Seehausen O, Genetic distance between species predicts novel trait expression in their hybrids. Evolution 2009

Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve?

Monteiro A, Podlaha O (2009) Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve? PLoS Biol 7(2): e1000037 doi:10.1371/journal.pbio.1000037

This is from the "Unsolved Mysteries" series that "discuss a topic of biological importance that is poorly understood and in need of research attention": "How Do Functional New Complex Networks Evolve?"

Welcome to A.S.S.!

This blog features weekly updates on the latest scientific literature, compiled by members of the Rosenthal Lab at Texas A&M University. Each week, each person flags a paper from the most recent issue of one of their three assigned scientific journals. Stay tuned.