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.