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Dougherty LR, Rovenolt F, Luyet A, Jokela J, Stephenson JF. Ornaments indicate parasite load only if they are dynamic or parasites are contagious. Evol Lett 2023; 7:176-190. [PMID: 37251584 PMCID: PMC10210455 DOI: 10.1093/evlett/qrad017] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 04/11/2023] [Accepted: 04/18/2023] [Indexed: 05/31/2023] Open
Abstract
Choosing to mate with an infected partner has several potential fitness costs, including disease transmission and infection-induced reductions in fecundity and parental care. By instead choosing a mate with no, or few, parasites, animals avoid these costs and may also obtain resistance genes for offspring. Within a population, then, the quality of sexually selected ornaments on which mate choice is based should correlate negatively with the number of parasites with which a host is infected ("parasite load"). However, the hundreds of tests of this prediction yield positive, negative, or no correlation between parasite load and ornament quality. Here, we use phylogenetically controlled meta-analysis of 424 correlations from 142 studies on a wide range of host and parasite taxa to evaluate explanations for this ambiguity. We found that ornament quality is weakly negatively correlated with parasite load overall, but the relationship is more strongly negative among ornaments that can dynamically change in quality, such as behavioral displays and skin pigmentation, and thus can accurately reflect current parasite load. The relationship was also more strongly negative among parasites that can transmit during sex. Thus, the direct benefit of avoiding parasite transmission may be a key driver of parasite-mediated sexual selection. No other moderators, including methodological details and whether males exhibit parental care, explained the substantial heterogeneity in our data set. We hope to stimulate research that more inclusively considers the many and varied ways in which parasites, sexual selection, and epidemiology intersect.
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Affiliation(s)
- Liam R Dougherty
- Department of Evolution, Ecology and Behaviour, University of Liverpool, Liverpool, United Kingdom
| | - Faith Rovenolt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, United States
| | - Alexia Luyet
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Jukka Jokela
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
- Institute for Integrative Biology, ETH Zürich, Zürich, Switzerland
| | - Jessica F Stephenson
- Corresponding author: University of Pittsburgh Department of Biological Sciences, Clapp Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260 USA.
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2
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Life-long testosterone and antiandrogen treatments affect the survival and reproduction of captive male red-legged partridges (Alectoris rufa). Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02878-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Abstract
Sexual steroids can play an important role as life-history organizers. In males, high circulating testosterone levels induce physiological/behavioral costs and benefits, leading to trade-offs. However, studies simultaneously testing the impact of these levels in both fitness components (survival and fecundity) during lifetime are scarce and limited to wild birds. To determine the mortality causes or hormonal manipulation impacts on male fertility is, nonetheless, a difficult task in free-ranging animals that could be easier in captivity. We longitudinally monitored captive red-legged partridges (Alectoris rufa) and exposed males to high exogenous testosterone levels, anti-androgens, or a control treatment during each breeding period throughout their lives. Theory predicts that individuals maintaining high androgen levels should obtain higher fitness returns via reproduction, but suffer reduced longevity. Testosterone-treated male partridges, accordingly, lived shorter compared to controls, since they were more prone to die from a natural bacterial infection. However, the same birds seemed to have a lower capacity to fertilize eggs, probably due to endocrine feedback reducing testicular mass. These results show that exogenous testosterone can exert unpredicted effects on fitness parameters. Therefore, caution must be taken when drawing conclusions from non-fully controlled experiments in the wild. Males treated with the androgen-receptor blocker flutamide did not outlive controls as predicted by the life-history trade-off theory, but their mates laid eggs with higher hatching success. The latter could be due to mechanisms improving sperm quality/quantity or influencing maternal investment in egg quality. Testosterone receptor activity/amount could thus be as relevant to fitness as testosterone levels.
Significance statement
It has repeatedly been hypothesized that high testosterone levels induce a cost in terms of reduced lifetime reproductive success. This can be due to reduced fecundity or via shorter lifespan. This is, however, only supported by a handful of studies, mostly in wild birds. We tested this in captive male red-legged partridges, which allowed us to determine reproductive success and mortality causes. We increased testosterone levels or blocked its action with antiandrogens throughout life. High testosterone levels reduced the survival by making birds more prone to die by infection. The eggs produced by their mates also showed lower hatching success, a probable manipulation artifact that should be considered in avian studies in the wild. Interestingly, the androgen-receptor blocker flutamide increased lifetime hatching success compared to controls, suggesting that androgen receptor amounts/activity are even more relevant to fitness than testosterone levels.
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Hund AK, Hubbard JK, Albrecht T, Vortman Y, Munclinger P, Krausová S, Tomášek O, Safran RJ. Divergent sexual signals reflect costs of local parasites. Evolution 2020; 74:2404-2418. [PMID: 32385910 DOI: 10.1111/evo.13994] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 04/12/2020] [Accepted: 04/26/2020] [Indexed: 01/27/2023]
Abstract
Many closely related populations are distinguished by variation in sexual signals and this variation is hypothesized to play an important role in reproductive isolation and speciation. Within populations, there is considerable evidence that sexual signals provide information about the incidence and severity of parasite infections, but it remains unclear if variation in parasite communities across space could play a role in initiating or maintaining sexual trait divergence. To test for variation in parasite-associated selection, we compared three barn swallow subspecies with divergent sexual signals. We found that parasite community structure and host tolerance to ecologically similar parasites varied between subspecies. Across subspecies we also found that different parasites were costly in terms of male survival and reproductive success. For each subspecies, the preferred sexual signal(s) were associated with the most costly local parasite(s), indicating that divergent signals are providing relevant information to females about local parasite communities. Across subspecies, the same traits were often associated with different parasites, indicating that parasite-sexual signal links are quite flexible and may evolve relatively quickly. This study provides evidence for (1) variation in parasite communities and (2) different parasite-sexual signal links among three closely related subspecies with divergent sexual signal traits, suggesting that parasites may play an important role in initiating and/or maintaining the divergence of sexual signals among these closely related, yet geographically isolated populations.
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Affiliation(s)
- Amanda K Hund
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309.,Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108
| | - Joanna K Hubbard
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309.,Department of Biology, Truman State University, Kirksville, Missouri, 63501
| | - Tomáš Albrecht
- Institute of Vertebrate Biology, Czech Academy of Sciences, Brno, 60365, Czech Republic.,Department of Zoology, Faculty of Science, Charles University, Prague, 128 44, Czech Republic
| | - Yoni Vortman
- Department of Animal Sciences, Tel Hai Academic College, Upper Galilee, 1220800, Israel
| | - Pavel Munclinger
- Department of Zoology, Faculty of Science, Charles University, Prague, 128 44, Czech Republic
| | - Simona Krausová
- Department of Zoology, Faculty of Science, Charles University, Prague, 128 44, Czech Republic
| | - Oldřich Tomášek
- Institute of Vertebrate Biology, Czech Academy of Sciences, Brno, 60365, Czech Republic
| | - Rebecca J Safran
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309
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4
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Lindsay WR, Andersson S, Bererhi B, Höglund J, Johnsen A, Kvarnemo C, Leder EH, Lifjeld JT, Ninnes CE, Olsson M, Parker GA, Pizzari T, Qvarnström A, Safran RJ, Svensson O, Edwards SV. Endless forms of sexual selection. PeerJ 2019; 7:e7988. [PMID: 31720113 PMCID: PMC6839514 DOI: 10.7717/peerj.7988] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 10/04/2019] [Indexed: 12/11/2022] Open
Abstract
In recent years, the field of sexual selection has exploded, with advances in theoretical and empirical research complementing each other in exciting ways. This perspective piece is the product of a "stock-taking" workshop on sexual selection and sexual conflict. Our aim is to identify and deliberate on outstanding questions and to stimulate discussion rather than provide a comprehensive overview of the entire field. These questions are organized into four thematic sections we deem essential to the field. First we focus on the evolution of mate choice and mating systems. Variation in mate quality can generate both competition and choice in the opposite sex, with implications for the evolution of mating systems. Limitations on mate choice may dictate the importance of direct vs. indirect benefits in mating decisions and consequently, mating systems, especially with regard to polyandry. Second, we focus on how sender and receiver mechanisms shape signal design. Mediation of honest signal content likely depends on integration of temporally variable social and physiological costs that are challenging to measure. We view the neuroethology of sensory and cognitive receiver biases as the main key to signal form and the 'aesthetic sense' proposed by Darwin. Since a receiver bias is sufficient to both initiate and drive ornament or armament exaggeration, without a genetically correlated or even coevolving receiver, this may be the appropriate 'null model' of sexual selection. Thirdly, we focus on the genetic architecture of sexually selected traits. Despite advances in modern molecular techniques, the number and identity of genes underlying performance, display and secondary sexual traits remains largely unknown. In-depth investigations into the genetic basis of sexual dimorphism in the context of long-term field studies will reveal constraints and trajectories of sexually selected trait evolution. Finally, we focus on sexual selection and conflict as drivers of speciation. Population divergence and speciation are often influenced by an interplay between sexual and natural selection. The extent to which sexual selection promotes or counteracts population divergence may vary depending on the genetic architecture of traits as well as the covariance between mating competition and local adaptation. Additionally, post-copulatory processes, such as selection against heterospecific sperm, may influence the importance of sexual selection in speciation. We propose that efforts to resolve these four themes can catalyze conceptual progress in the field of sexual selection, and we offer potential avenues of research to advance this progress.
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Affiliation(s)
- Willow R. Lindsay
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - Staffan Andersson
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - Badreddine Bererhi
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - Jacob Höglund
- Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Arild Johnsen
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Charlotta Kvarnemo
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - Erica H. Leder
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Jan T. Lifjeld
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Calum E. Ninnes
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, United States of America
| | - Mats Olsson
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - Geoff A. Parker
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Tommaso Pizzari
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, United Kingdom
| | - Anna Qvarnström
- Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Rebecca J. Safran
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, United States of America
| | - Ola Svensson
- School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden
| | - Scott V. Edwards
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, United States of America
- Gothenburg Centre for Advanced Studies in Science and Technology, Chalmers University of Technology, Göteborg, Sweden
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5
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Escallón C, Becker MH, Walke JB, Jensen RV, Cormier G, Belden LK, Moore IT. Testosterone levels are positively correlated with cloacal bacterial diversity and the relative abundance of Chlamydiae in breeding male rufous‐collared sparrows. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12696] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Camilo Escallón
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
| | - Matthew H. Becker
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
| | - Jenifer B. Walke
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
| | - Roderick V. Jensen
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
| | - Guy Cormier
- Georgia Advanced Computing Resource Center The University of Georgia 4098C Stegeman Coliseum Athens Georgia 30602 USA
| | - Lisa K. Belden
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
| | - Ignacio T. Moore
- Department of Biological Sciences Virginia Tech 2119 Derring Hall Blacksburg Virginia 24061 USA
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Merrill L, González-Gómez PL, Ellis VA, Levin II, Vásquez RA, Wingfield JC. A blurring of life-history lines: Immune function, molt and reproduction in a highly stable environment. Gen Comp Endocrinol 2015; 213:65-73. [PMID: 25712433 DOI: 10.1016/j.ygcen.2015.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 01/26/2015] [Accepted: 02/14/2015] [Indexed: 10/24/2022]
Abstract
Rufous-collared sparrows (Zonotrichia capensis peruviensis) from valleys in the Atacama Desert of Chile, live in an extremely stable environment, and exhibit overlap in molt and reproduction, with valley-specific differences in the proportion of birds engaged in both. To better understand the mechanistic pathways underlying the timing of life-history transitions, we examined the relationships among baseline and stress-induced levels of corticosterone (CORT), testosterone, and bacteria-killing ability of the blood plasma (BKA), as well as haemosporidian parasite infections and the genetic structure of two groups of sparrows from separate valleys over the course of a year. Birds neither molting nor breeding had the lowest BKA, but there were no differences among the other three categories of molt-reproductive stage. BKA varied over the year, with birds in May/June exhibiting significantly lower levels of BKA than the rest of the year. We also documented differences in the direction of the relationship between CORT and BKA at different times during the year. The direction of these relationships coincides with some trends in molt and reproductive stage, but differs enough to indicate that these birds exhibit individual-level plasticity, or population-level variability, in coordinating hypothalamo-pituitary-adrenal axis activity with life-history stage. We found weak preliminary evidence for genetic differentiation between the two populations, but not enough to indicate genetic isolation. No birds were infected with haemosporidia, which may be indicative of reduced parasite pressure in deserts. The data suggest that these birds may not trade off among different life-history components, but rather are able to invest in multiple life-history components based on their condition.
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Affiliation(s)
- Loren Merrill
- Illinois Natural History Survey, University of Illinois, Urbana-Champaign, IL 61820, USA.
| | | | - Vincenzo A Ellis
- Department of Biology, University of Missouri, St. Louis, MO 63121, USA.
| | - Iris I Levin
- Department of Biology, Grinnell College, Grinnell, IA 50112, USA; Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309, USA(1).
| | - Rodrigo A Vásquez
- Instituto de Ecología y Biodiversidad, IEB, Universidad de Chile, Santiago, Chile.
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