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Immunoecology of Species with Alternative Reproductive Tactics and Strategies. J ZOOL SYST EVOL RES 2022. [DOI: 10.1155/2022/3248731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Alternative reproductive tactics and strategies (ARTS) refer to polymorphic reproductive behaviours in which in addition to the usual two sexes, there are one or more alternative morphs, usually male, that have evolved the ability to circumvent direct intra-sexual competition. Each morph has its own morphological, ecological, developmental, behavioural, life-history, and physiological profile that shifts the balance between reproduction and self-maintenance, one aspect being immunity. Immunoecological work on species with ARTS, which is the topic of this review, is particularly interesting because the alternative morphs make it possible to separate the effects of sex per se from other factors that in other species are inextricably linked with sex. We first summarize the evolution, development, and maintenance of ARTS. We then review immunoecological hypotheses relevant to species with ARTS, dividing them into physiological, life-history, and ecological hypotheses. In context of these hypotheses, we critically review in detail all immunoecological studies we could find on species with ARTS. Several interesting patterns emerge. Oddly, there is a paucity of studies on insects, despite the many benefits that arise from working with insects: larger sample sizes, simple immune systems, and countless forms of alternative reproductive strategies and tactics. Of all the hypotheses considered, the immunocompetence handicap hypothesis has generated the greatest amount of work, but not necessarily the greatest level of understanding. Unfortunately, it is often used as a general guiding principle rather than a source of explicitly articulated predictions. Other hypotheses are usually considered a posteriori, but perhaps they should take centre stage. Whereas blanket concepts such as “immunocompetence” and “androgens” might be useful to develop a rationale, predictions need to be far more explicitly articulated. Integration so far has been a one-way street, with ecologists delving deeper into physiology, sometimes at the cost of ignoring their organisms’ evolutionary history and ecology. One possible useful framework is to divide ecological and evolutionary factors affecting immunity into those that stimulate the immune system, and those that depress it. Finally, the contributions of genomics to ecology are being increasingly recognized and sometimes applied to species with ARTS, but we must ensure that evolutionary and ecological hypotheses drive the effort, as there is no grandeur in the strict reductionist view of life.
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Boyd RJ, Kelly TR, MacDougall-Shackleton SA, MacDougall-Shackleton EA. Alternative reproductive strategies in white-throated sparrows are associated with differences in parasite load following experimental infection. Biol Lett 2019; 14:rsbl.2018.0194. [PMID: 29973391 DOI: 10.1098/rsbl.2018.0194] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 06/11/2018] [Indexed: 11/12/2022] Open
Abstract
Immune defences often trade off with other life-history components. Within species, optimal allocation to immunity may differ between the sexes or between alternative life-history strategies. White-throated sparrows (Zonotrichia albicollis) are unusual in having two discrete plumage morphs, white-striped and tan-striped. Within each sex, white-striped individuals are more aggressive and provide less parental care than tan-striped individuals. We extended immunocompetence handicap models, which predict sex differences in immunity and parasitism, to hypothesize that infection susceptibility should be greater in white-striped than tan-striped birds. We inoculated birds of both morphs with malarial parasites. Contrary to our prediction, among birds that became infected, parasite loads were higher in tan-striped than white-striped individuals and did not differ between the sexes. Circulating androgen levels did not differ between morphs but were higher in males than females. Our findings are not consistent with androgen-mediated immunosuppression. Instead, morph differences in immunity could reflect social interactions or life-history-related differences in risk of injury, and/or genetic factors. Although plumage and behavioural morphs of white-throated sparrow may differ in disease resistance, these differences do not parallel sex differences that have been reported in animals, and do not appear to be mediated by differences in androgen levels.
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Affiliation(s)
- R J Boyd
- Biology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5B7
| | - T R Kelly
- Biology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5B7
| | - S A MacDougall-Shackleton
- Biology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5B7.,Psychology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5C2
| | - E A MacDougall-Shackleton
- Biology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5B7
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Escallón C, Belden LK, Moore IT. The Cloacal Microbiome Changes with the Breeding Season in a Wild Bird. Integr Org Biol 2019; 1:oby009. [PMID: 33791516 PMCID: PMC7671126 DOI: 10.1093/iob/oby009] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The symbiotic microbial communities, or “microbiomes,” that reside on animals are dynamic, and can be affected by the behavior and physiology of the host. These communities provide many critical beneficial functions for their hosts, but they can also include potential pathogens. In birds, bacteria residing in the cloaca form a complex community, including both gut and sexually-transmitted bacteria. Transmission of cloacal bacteria among individuals is likely during the breeding season, when there is direct cloacal contact between individuals. In addition, the major energetic investment in reproduction can draw resources away from immune responses that might otherwise prevent the successful establishment of microbes. We assessed dynamic variation in the cloacal microbiome of free-living rufous-collared sparrows (Zonotrichia capensis) through sequential breeding and non-breeding seasons. We found that the cloacal bacterial communities differed between the sexes when they were in breeding condition. Further, in males, but not in females, the bacterial community became more diverse with the onset of reproduction, and then decreased in diversity as males transitioned to non-breeding condition. Individuals sampled across sequential breeding seasons did not accumulate more bacterial taxa over seasons, but bacterial community composition did change. Our results suggest that the cloacal microbiome in birds is dynamic and, especially in males, responsive to breeding condition.
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Affiliation(s)
- C Escallón
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA.,Departamento de Ciencias Básicas, Universidad de La Salle, Cra 2 No. 10-70, Bogotá, Colombia
| | - L K Belden
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - I T Moore
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
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Costantini D. Meta-analysis reveals that reproductive strategies are associated with sexual differences in oxidative balance across vertebrates. Curr Zool 2018; 64:1-11. [PMID: 29492033 PMCID: PMC5809033 DOI: 10.1093/cz/zox002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 01/16/2017] [Indexed: 12/14/2022] Open
Abstract
Oxidative stress is a key physiological mechanism underlying life-history tradeoffs. Here, I use meta-analytic techniques to test whether sexual differences in oxidative balance are common in vertebrates and to identify which factors are associated with such differences. The dataset included 732 effect size estimates from 100 articles (82 species). Larger unsigned effect size (meaning larger sexual differences in a given marker) occurred in: reptiles and fish; those species that do not provide parental care; and oviparous species. Estimates of signed effect size (positive values meaning higher oxidative stress in males) indicated that females were less resistant to oxidative stress than males in: reptiles while males and females were similar in fish, birds, and mammals; those species that do not provide parental care; and oviparous species. There was no evidence for a significant sexual differentiation in oxidative balance in fish, birds, and mammals. Effect size was not associated with: the number of offspring; whether the experimental animals were reproducing or not; biomarker (oxidative damage, non-enzymatic, or enzymatic antioxidant), the species body mass; the strain (wild vs. domestic); or the study environment (wild vs. captivity). Oxidative stress tended to be higher in females than males across most of the tissues analyzed. Levels of residual heterogeneity were high in all models tested. The findings of this meta-analysis indicate that diversification of reproductive strategies might be associated with sexual differences in oxidative balance. This explorative meta-analysis offers a starting platform for future research to investigate the relationship between sex and oxidative balance further.
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Affiliation(s)
- David Costantini
- UMR 7221, Muséum National d'Histoire Naturelle, 7 rue Cuvier 75231 Paris Cedex 05, France
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, Berlin 10315, Germany
- Behavioural Ecology & Ecophysiology Group, Department of Biology, University of Antwerp, Universiteitsplein 1, Wilrijk 2610, Belgium
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Evans JK, Buchanan KL, Griffith SC, Klasing KC, Addison B. Ecoimmunology and microbial ecology: Contributions to avian behavior, physiology, and life history. Horm Behav 2017; 88:112-121. [PMID: 28065710 DOI: 10.1016/j.yhbeh.2016.12.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 11/29/2016] [Accepted: 12/05/2016] [Indexed: 12/21/2022]
Abstract
Bacteria have had a fundamental impact on vertebrate evolution not only by affecting the evolution of the immune system, but also generating complex interactions with behavior and physiology. Advances in molecular techniques have started to reveal the intricate ways in which bacteria and vertebrates have coevolved. Here, we focus on birds as an example system for understanding the fundamental impact bacteria have had on the evolution of avian immune defenses, behavior, physiology, reproduction and life histories. The avian egg has multiple characteristics that have evolved to enable effective defense against pathogenic attack. Microbial risk of pathogenic infection is hypothesized to vary with life stage, with early life risk being maximal at either hatching or fledging. For adult birds, microbial infection risk is also proposed to vary with habitat and life stage, with molt inducing a period of increased vulnerability. Bacteria not only play an important role in shaping the immune system as well as trade-offs with other physiological systems, but also for determining digestive efficiency and nutrient uptake. The relevance of avian microbiomes for avian ecology, physiology and behavior is highly topical and will likely impact on our understanding of avian welfare, conservation, captive breeding as well as for our understanding of the nature of host-microbe coevolution.
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Affiliation(s)
- Jessica K Evans
- School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Geelong 3220, Victoria, Australia; Department of Biological Sciences, Macquarie University, 2122, New South Wales, Australia
| | - Katherine L Buchanan
- School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Geelong 3220, Victoria, Australia
| | - Simon C Griffith
- Department of Biological Sciences, Macquarie University, 2122, New South Wales, Australia
| | - Kirk C Klasing
- Department of Animal Science, University of California, 1 Shields Avenue, Davis, CA 95616, USA
| | - BriAnne Addison
- School of Life and Environmental Sciences, Deakin University, Waurn Ponds, Geelong 3220, Victoria, Australia.
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