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Simons MJP, Sebire M, Verhulst S, Groothuis TGG. Androgen Elevation Accelerates Reproductive Senescence in Three-Spined Stickleback. Front Cell Dev Biol 2022; 9:752352. [PMID: 34977010 PMCID: PMC8718761 DOI: 10.3389/fcell.2021.752352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022] Open
Abstract
Costs of reproduction shape the life-history evolution of investment in current and future reproduction and thereby aging. Androgens have been proposed to regulate the physiology governing these investments. Furthermore, androgens are hypothesized to play a central role in carotenoid-dependent sexual signaling, regulating how much carotenoids are diverted to ornamentation and away from somatic maintenance, increasing oxidative stress, and accelerating aging. We investigated these relationships in male three-spined stickleback in which we elevated 11-ketotestosterone and supplied vitamin E, an antioxidant, in a 2 × 2 design. Androgen elevation shortened the time stickleback maintained reproductive activities. We suspect that this effect is caused by 11-ketotestosterone stimulating investment in current reproduction, but we detected no evidence for this in our measurements of reproductive effort: nest building, body composition, and breeding coloration. Carotenoid-dependent coloration was even slightly decreased by 11-ketotestosterone elevation and was left unaffected by vitamin E. Red coloration correlated with life expectancy and reproductive capacity in a quadratic manner, suggesting overinvestment of the individuals exhibiting the reddest bellies. In contrast, blue iris color showed a negative relationship with survival, suggesting physiological costs of producing this aspect of nuptial coloration. In conclusion, our results support the hypothesis that androgens regulate investment in current versus future reproduction, yet the precise mechanisms remain elusive. The quadratic relationships between sexual signal expression and aspects of quality have wider consequences for how we view sexual selection on ornamentation and its relationship with aging.
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Affiliation(s)
- Mirre J P Simons
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
| | - Marion Sebire
- The Centre for Environment, Fisheries and Aquaculture Science, Weymouth, United Kingdom
| | - Simon Verhulst
- Behavioural Biology, Centre for Behaviour and Neuroscience, University of Groningen, Groningen, Netherlands
| | - Ton G G Groothuis
- Behavioural Biology, Centre for Behaviour and Neuroscience, University of Groningen, Groningen, Netherlands
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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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3
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Cantarero A, Pérez-Rodríguez L, Romero-Haro AÁ, Chastel O, Alonso-Alvarez C. Carotenoid-based coloration predicts both longevity and lifetime fecundity in male birds, but testosterone disrupts signal reliability. PLoS One 2019; 14:e0221436. [PMID: 31442265 PMCID: PMC6707625 DOI: 10.1371/journal.pone.0221436] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 08/06/2019] [Indexed: 01/09/2023] Open
Abstract
Sexual selection promotes the evolution of conspicuous animal ornaments. To evolve as signals, these traits must reliably express the “quality” of the bearer, an indicator of individual fitness. Direct estimates of individual fitness may include the contribution of longevity and fecundity. However, evidence of a correlation between the level of signal expression and these two fitness components are scarce, at least among vertebrates. Relative fitness is difficult to assess in the wild as age at death and extra-pair paternity rates are often unknown. Here, in captive male red-legged partridges, we show that carotenoid-based ornament expression, i.e., redness of the bill and eye rings, at the beginning of reproductive life predicts both longevity (1–7 years) and lifetime breeding output (offspring number and hatching success). The recently proposed link between the individual capacity to produce red (keto) carotenoid pigments and the efficiency of cell respiration could, ultimately, explain the correlation with lifespan and, indirectly, fecundity. Nonetheless, in males of avian species, carotenoid-based coloration in bare parts is also partially controlled by testosterone. We also manipulated androgen levels throughout life by treating males with testosterone or antiandrogen compounds. Treatments caused correlations between signal levels and both fitness components to disappear, thus making the signals unreliable. This suggests that the evolution of carotenoid-based sexual signals requires a tightly-controlled steroid metabolism.
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Affiliation(s)
- Alejandro Cantarero
- Section of Ecology, University of Turku, Turku, Finland
- * E-mail: (AC); (CA-A)
| | - Lorenzo Pérez-Rodríguez
- Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC - UCLM - JCCM), Ciudad Real, Spain
| | | | - Olivier Chastel
- Centre d’Etudes Biologiques de Chizé, CNRS U.M.R. 7372 and Université de La Rochelle, Villiers-en-Bois, France
| | - Carlos Alonso-Alvarez
- Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales - CSIC, Madrid, Spain
- * E-mail: (AC); (CA-A)
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4
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Intra-sexual competition modulates calling behavior and its association with secondary sexual traits. Behav Ecol Sociobiol 2016. [DOI: 10.1007/s00265-016-2169-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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5
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Wenzel MA, Douglas A, James MC, Redpath SM, Piertney SB. The role of parasite-driven selection in shaping landscape genomic structure in red grouse (Lagopus lagopus scotica). Mol Ecol 2015; 25:324-41. [PMID: 26578090 DOI: 10.1111/mec.13473] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 11/09/2015] [Accepted: 11/10/2015] [Indexed: 12/25/2022]
Abstract
Landscape genomics promises to provide novel insights into how neutral and adaptive processes shape genome-wide variation within and among populations. However, there has been little emphasis on examining whether individual-based phenotype-genotype relationships derived from approaches such as genome-wide association (GWAS) manifest themselves as a population-level signature of selection in a landscape context. The two may prove irreconcilable as individual-level patterns become diluted by high levels of gene flow and complex phenotypic or environmental heterogeneity. We illustrate this issue with a case study that examines the role of the highly prevalent gastrointestinal nematode Trichostrongylus tenuis in shaping genomic signatures of selection in red grouse (Lagopus lagopus scotica). Individual-level GWAS involving 384 SNPs has previously identified five SNPs that explain variation in T. tenuis burden. Here, we examine whether these same SNPs display population-level relationships between T. tenuis burden and genetic structure across a small-scale landscape of 21 sites with heterogeneous parasite pressure. Moreover, we identify adaptive SNPs showing signatures of directional selection using F(ST) outlier analysis and relate population- and individual-level patterns of multilocus neutral and adaptive genetic structure to T. tenuis burden. The five candidate SNPs for parasite-driven selection were neither associated with T. tenuis burden on a population level, nor under directional selection. Similarly, there was no evidence of parasite-driven selection in SNPs identified as candidates for directional selection. We discuss these results in the context of red grouse ecology and highlight the broader consequences for the utility of landscape genomics approaches for identifying signatures of selection.
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Affiliation(s)
- Marius A Wenzel
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Alex Douglas
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Marianne C James
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Steve M Redpath
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Stuart B Piertney
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
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6
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Wenzel MA, James MC, Douglas A, Piertney SB. Genome-wide association and genome partitioning reveal novel genomic regions underlying variation in gastrointestinal nematode burden in a wild bird. Mol Ecol 2015; 24:4175-92. [PMID: 26179597 DOI: 10.1111/mec.13313] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 06/23/2015] [Accepted: 07/03/2015] [Indexed: 02/06/2023]
Abstract
Identifying the genetic architecture underlying complex phenotypes is a notoriously difficult problem that often impedes progress in understanding adaptive eco-evolutionary processes in natural populations. Host-parasite interactions are fundamentally important drivers of evolutionary processes, but a lack of understanding of the genes involved in the host's response to chronic parasite insult makes it particularly difficult to understand the mechanisms of host life history trade-offs and the adaptive dynamics involved. Here, we examine the genetic basis of gastrointestinal nematode (Trichostrongylus tenuis) burden in 695 red grouse (Lagopus lagopus scotica) individuals genotyped at 384 genome-wide SNPs. We first use genome-wide association to identify individual SNPs associated with nematode burden. We then partition genome-wide heritability to identify chromosomes with greater heritability than expected from gene content, due to harbouring a multitude of additive SNPs with individually undetectable effects. We identified five SNPs on five chromosomes that accounted for differences of up to 556 worms per bird, but together explained at best 4.9% of the phenotypic variance. These SNPs were closely linked to genes representing a range of physiological processes including the immune system, protein degradation and energy metabolism. Genome partitioning indicated genome-wide heritability of up to 29% and three chromosomes with excess heritability of up to 4.3% (total 8.9%). These results implicate SNPs and novel genomic regions underlying nematode burden in this system and suggest that this phenotype is somewhere between being based on few large-effect genes (oligogenic) and based on a large number of genes with small individual but large combined effects (polygenic).
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Affiliation(s)
- Marius A Wenzel
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Marianne C James
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Alex Douglas
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
| | - Stuart B Piertney
- Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
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7
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Wenzel MA, Piertney SB. Fine-scale population epigenetic structure in relation to gastrointestinal parasite load in red grouse (Lagopus lagopus scotica). Mol Ecol 2014; 23:4256-73. [PMID: 24943398 PMCID: PMC4282444 DOI: 10.1111/mec.12833] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/10/2014] [Accepted: 06/11/2014] [Indexed: 12/27/2022]
Abstract
Epigenetic modification of cytosine methylation states can be elicited by environmental stresses and may be a key process affecting phenotypic plasticity and adaptation. Parasites are potent stressors with profound physiological and ecological effects on their host, but there is little understanding in how parasites may influence host methylation states. Here, we estimate epigenetic diversity and differentiation among 21 populations of red grouse (Lagopus lagopus scotica) in north-east Scotland and test for association of gastrointestinal parasite load (caecal nematode Trichostrongylus tenuis) with hepatic genome-wide and locus-specific methylation states. Following methylation-sensitive AFLP (MSAP), 129 bands, representing 73 methylation-susceptible and 56 nonmethylated epiloci, were scored across 234 individuals. The populations differed significantly in genome-wide methylation levels and were also significantly epigenetically (FSC = 0.0227; P < 0.001) and genetically (FSC = 0.0058; P < 0.001) differentiated. Parasite load was not associated with either genome-wide methylation levels or epigenetic differentiation. Instead, we found eight disproportionately differentiated epilocus-specific methylation states (FST outliers) using bayescan software and significant positive and negative association of 35 methylation states with parasite load from bespoke generalized estimating equations (GEE), simple logistic regression (sam) and Bayesian environmental analysis (bayenv2). Following Sanger sequencing, genome mapping and geneontology (go) annotation, some of these epiloci were linked to genes involved in regulation of cell cycle, signalling, metabolism, immune system and notably rRNA methylation, histone acetylation and small RNAs. These findings demonstrate an epigenetic signature of parasite load in populations of a wild bird and suggest intriguing physiological effects of parasite-associated cytosine methylation.
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Affiliation(s)
- Marius A Wenzel
- Institute of Biological and Environmental Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
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8
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Martínez-Padilla J, Pérez-Rodríguez L, Mougeot F, Ludwig S, Redpath SM. Intra-sexual competition alters the relationship between testosterone and ornament expression in a wild territorial bird. Horm Behav 2014; 65:435-44. [PMID: 24698833 DOI: 10.1016/j.yhbeh.2014.03.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 03/18/2014] [Accepted: 03/22/2014] [Indexed: 01/21/2023]
Abstract
In a reliable signalling system, individual quality is expected to mediate the costs associated with ornamental displays, with relatively lower costs being paid by individuals of higher quality. These relative costs should depend not only on individual quality, but also on levels of intra-sexual competition. We explored the current and delayed effects that testosterone implants have on bird ornamentation in populations with contrasted population densities, as a proxy for intra-sexual competition. In a replicated experiment, we manipulated testosterone in 196 yearling male red grouse Lagopus lagopus scoticus in autumn in populations of high and low levels of intra-sexual competition. Males were assigned to one of three exogenous testosterone (T) treatments: empty implants (T0), small T implants (T1) or larger T implants (T2). We monitored subsequent changes in testosterone levels, ornament size and carotenoid-based colouration, carotenoid levels and body condition from autumn to spring. Testosterone implants increased testosterone levels, comb redness and comb size, and decreased body condition but these effects depended on levels of intra-sexual competition. Specifically, T2-implanted birds increased testosterone levels and comb size more, and reduced body condition more, in populations where intra-sexual competition was low. In the following spring, testosterone levels of T2-treated birds kept increasing in populations where intra-sexual competition was high but not in populations where intra-sexual competition was low. Our results highlight that levels of intra-sexual competition alter the relationship between testosterone levels and ornament expression, influencing their condition-dependence; they also indicate that the outcome of standard hormone manipulation conducted in free-living animals vary depending on the population context.
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Affiliation(s)
- J Martínez-Padilla
- Department of Evolutionary Ecology, Museo Nacional de Ciencias Naturales, José Gutiérrez Abascal, 2, 23005, Madrid, Spain.
| | - L Pérez-Rodríguez
- Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC, UCLM, JCCM), Ronda de Toledo, s/n, 3005 Ciudad Real, Spain; Department of Evolutionary Ecology, Estación Biológica de Doñana, (EBD-CSIC), Avda. Americo Vespucio, s/n, 41092 Seville, Spain
| | - F Mougeot
- Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC, UCLM, JCCM), Ronda de Toledo, s/n, 3005 Ciudad Real, Spain; Estación Experimental de Zonas Áridas (CSIC), Ctra. de Sacramento s/n, La Cañada de San Urbano, 04120 Almería, Spain
| | - S Ludwig
- Game & Wildlife Conservation Trust, Eggleston Hall, Barnard Castle, DL12 0AG UK
| | - S M Redpath
- School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK
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9
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Martínez-Padilla J, Pérez-Rodríguez L, Mougeot F, Ludwig SC, Redpath SM. Experimentally elevated levels of testosterone at independence reduce fitness in a territorial bird. Ecology 2014; 95:1033-44. [DOI: 10.1890/12-1905.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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10
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Fletcher K, Hoodless AN, Baines D. Impacts of predator abundance on red grouseLagopus lagopus scoticaduring a period of experimental predator control. WILDLIFE BIOLOGY 2013. [DOI: 10.2981/12-009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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11
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Martínez-Padilla J, Redpath SM, Zeineddine M, Mougeot F. Insights into population ecology from long-term studies of red grouseLagopus lagopus scoticus. J Anim Ecol 2013; 83:85-98. [DOI: 10.1111/1365-2656.12098] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 04/30/2013] [Indexed: 01/17/2023]
Affiliation(s)
- Jesus Martínez-Padilla
- Museo Nacional de Ciencias Naturales; Department of Evolutionary Biology; José Guitérrez Abascal 2 28006 Madrid Spain
| | - Steve M. Redpath
- ACES; Department of Biological Sciences; University of Aberdeen; Zoology Building Tillydrone Av. Aberdeen AB24 2TZ UK
| | - Mohammed Zeineddine
- ACES; Department of Biological Sciences; University of Aberdeen; Zoology Building Tillydrone Av. Aberdeen AB24 2TZ UK
| | - François Mougeot
- EEZA-CSIC; La Cañada de San Urbano; 04120 Almeria Spain
- IREC (CSIC-UCLM-JCCM); Ronda de Toledo s/n 13005 Ciuada Real Spain
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12
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Vergara P, Redpath SM, Martínez-Padilla J, Mougeot F. Environmental conditions influence red grouse ornamentation at a population level. Biol J Linn Soc Lond 2012. [DOI: 10.1111/j.1095-8312.2012.01974.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Pablo Vergara
- School of Biological Sciences; University of Aberdeen; Tillydrone Av.; Aberdeen; AB24 2TZ; UK
| | - Stephen M. Redpath
- School of Biological Sciences; University of Aberdeen & The James Hutton Institute; Aberdeen Centre for Environmental Sustainability (ACES); Tillydrone Av.; Aberdeen; AB24 2TZ; UK
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13
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Vergara P, Martínez-Padilla J. Social context decouples the relationship between a sexual ornament and testosterone levels in a male wild bird. Horm Behav 2012; 62:407-12. [PMID: 22841824 DOI: 10.1016/j.yhbeh.2012.07.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 07/16/2012] [Accepted: 07/18/2012] [Indexed: 11/19/2022]
Abstract
In order to maximise fitness individuals should adjust their level of signalling according to their surrounding social environment. However, field experiments showing such adjustment of current signalling associated to changes in social context are lacking. Here, we manipulated levels of male aggressive- and dominance-related displays in a wild bird in our treated area by increasing testosterone levels using implants in a subset of males. We then compared the expression of sexual signals (i.e. comb size) between non-treated red grouse Lagopus lagopus scoticus males from control and treatment areas. We further explored the potential endocrinological mechanism linking social environment and signal expression by analysing testosterone levels in all males. Our treatment successfully increased overall aggressive- and dominance-related behaviours in the treatment area. Furthermore, testosterone-implanted birds increased their comb size as repeatedly shown in previous studies in male red grouse. Interestingly, untreated males living in the treatment area decreased their comb size, whilst increasing testosterone levels. Since comb size is a signal of dominance, untreated males from the treatment area may have perceived themselves as subordinate individuals and decreased their signalling levels to avoid confrontations with testosterone-treated, dominant individuals. In conclusion, our findings show that social context has the potential to regulate sexual signalling and testosterone levels. Our results highlight the role of social context when exploring the link between testosterone and behaviour, as it may reverse the relationship between both traits. Our results suggest that social context affects signalling and testosterone independently.
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Affiliation(s)
- Pablo Vergara
- School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK.
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14
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VERGARA P, MARTINEZ-PADILLA J, MOUGEOT F, LECKIE F, REDPATH SM. Environmental heterogeneity influences the reliability of secondary sexual traits as condition indicators. J Evol Biol 2011; 25:20-8. [DOI: 10.1111/j.1420-9101.2011.02399.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Bunnefeld N, Reuman DC, Baines D, Milner-Gulland EJ. Impact of unintentional selective harvesting on the population dynamics of red grouse. J Anim Ecol 2011; 80:1258-68. [PMID: 21595686 DOI: 10.1111/j.1365-2656.2011.01862.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
1. The effect of selective exploitation of certain age, stage or sex classes (e.g., trophy hunting) on population dynamics is relatively well studied in fisheries and sexually dimorphic mammals. 2. Harvesting of terrestrial species with no morphological differences visible between the different age and sex classes (monomorphic species) is usually assumed to be nonselective because monomorphicity makes intentionally selective harvesting pointless and impractical. But harvesting of the red grouse (Lagopus lagopus scoticus), a monomorphic species, was recently shown to be unintentionally selective. This study uses a sex- and age-specific model to explore the previously unresearched effects of unintentional harvesting selectivity. 3. We examine the effects of selectivity on red grouse dynamics by considering models with and without selectivity. Our models include territoriality and parasitism, two mechanisms known to be important for grouse dynamics. 4. We show that the unintentional selectivity of harvesting that occurs in red grouse decreases population yield compared with unselective harvesting at high harvest rates. Selectivity also dramatically increases extinction risk at high harvest rates. 5. Selective harvesting strengthens the 3- to 13-year red grouse population cycle, suggesting that the selectivity of harvesting is a previously unappreciated factor contributing to the cycle. 6. The additional extinction risk introduced by harvesting selectivity provides a quantitative justification for typically implemented 20-40% harvest rates, which are below the maximum sustainable yield that could be taken, given the observed population growth rates of red grouse. 7. This study shows the possible broad importance of investigating in future research whether unintentionally selective harvesting occurs on other species.
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Affiliation(s)
- Nils Bunnefeld
- Department of Life Sciences, Imperial College London, Silwood Park, Ascot, SL5 7PY, UK.
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16
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Hawley DM, Altizer SM. Disease ecology meets ecological immunology: understanding the links between organismal immunity and infection dynamics in natural populations. Funct Ecol 2011. [DOI: 10.1111/j.1365-2435.2010.01753.x] [Citation(s) in RCA: 259] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Dana M. Hawley
- Department of Biology, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Sonia M. Altizer
- Odum School of Ecology, University of Georgia, Athens, Georgia 30602, USA
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17
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Dissecting the drivers of population cycles: Interactions between parasites and mountain hare demography. Ecol Modell 2011. [DOI: 10.1016/j.ecolmodel.2010.08.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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18
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Webster LMI, Paterson S, Mougeot F, Martinez-Padilla J, Piertney SB. Transcriptomic response of red grouse to gastro-intestinal nematode parasites and testosterone: implications for population dynamics. Mol Ecol 2010; 20:920-31. [PMID: 21073676 DOI: 10.1111/j.1365-294x.2010.04906.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A central issue in ecology is in understanding the relative influences of intrinsic and extrinsic effects on population regulation. Previous studies on the cyclic population dynamics of red grouse (Lagopus lagopus scoticus) have emphasized the destabilizing effects of either nematode parasites or territorial behaviour and aggression. The potential interacting effects of these processes, mediated through density-dependent, environmentally induced alterations of host immunocompetence influencing susceptibility to parasites have not been considered. Male red grouse at high density are more aggressive, associated with increased testosterone, which potentially could lead to reduced immunocompetence at a stage when parasites are most prevalent. This could depress individual condition, breeding performance and survival and thus drive or contribute to overall reductions in population size. Here, we characterize the transcriptomic response of grouse to nematode parasite infection and investigate how this is subsequently affected by testosterone, using a microarray approach contrasting red grouse with high and low parasite load at both high and low testosterone titre. A suite of 52 transcripts showed a significant level of up-regulation to either chronic parasite load or experimental parasite infection. Of these, 51 (98%) showed a reduced level of expression under conditions of high parasite load and high testosterone. The genes up-regulated by parasites and then down-regulated at high testosterone titre were not necessarily associated with immune response, as might be intuitively expected. The results are discussed in relation to the fitness and condition of individual red grouse and factors influencing the regulation of abundance in natural populations.
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Affiliation(s)
- L M I Webster
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
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19
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MARTÍNEZ-PADILLA J, MOUGEOT F, WEBSTER LMI, PÉREZ-RODRÍGUEZ L, PIERTNEY SB. Testing the interactive effects of testosterone and parasites on carotenoid-based ornamentation in a wild bird. J Evol Biol 2010; 23:902-13. [DOI: 10.1111/j.1420-9101.2010.01956.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Martínez-Padilla J, Dixon H, Vergara P, Pérez-Rodríguez L, Fargallo JA. Does egg colouration reflect male condition in birds? Naturwissenschaften 2010; 97:469-77. [PMID: 20309517 DOI: 10.1007/s00114-010-0660-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 02/16/2010] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
How colouration provides information about individuals in birds has been a central issue in recent decades. Although much information has been derived, little is known about the adaptive significance of egg colouration in birds. A recent idea suggests that biliverdin- and porphyrin-pigmented eggs may act as a post-mating sexual signal for males to assess female quality. In birds, it is common for males to influence prelaying female condition by courtship feeding. Using Eurasian kestrels, a species that lays protoporphyrin-pigmented eggs, we descriptively assessed the influence of male feeding on egg pigmentation by considering female phenotype, condition, breeding parameters and male body condition. We found that older females and females with greyer tails (an index of individual quality) produce highly pigmented eggs. However, male body condition was the only variable that explained egg colouration when considered together with the female-related variables. Therefore, females that mated with males in better condition laid highly pigmented eggs. With the same species, we also explored the cost of producing protoporphyrin-pigmented eggs using a food-supply experiment before the laying period. Food supplementation did not increase egg pigmentation, but hatching success and egg mass were positively related to egg colouration only in food supplied pairs. We suggest that egg colouration might be costly to produce and probably suggests egg quality. However, this cost cannot be explained by female quality, but by male condition instead. In general, our results do not support the theory that egg colouration is a post-mating sexual signal in species where males determine female condition at the time of laying.
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Affiliation(s)
- Jesús Martínez-Padilla
- Aberdeen Centre for Environmental Sustainability (ACES), University of Aberdeen & The Macaulay Institute, School of Biological Sciences, Tillydrone Avenue, Aberdeen, UK.
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New L, Matthiopoulos J, Redpath S, Buckland S. Fitting Models of Multiple Hypotheses to Partial Population Data: Investigating the Causes of Cycles in Red Grouse. Am Nat 2009; 174:399-412. [DOI: 10.1086/603625] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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22
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Bunnefeld N, Baines D, Newborn D, Milner-Gulland EJ. Factors affecting unintentional harvesting selectivity in a monomorphic species. J Anim Ecol 2009; 78:485-92. [DOI: 10.1111/j.1365-2656.2008.01500.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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23
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Sherratt JA, Smith MJ. Periodic travelling waves in cyclic populations: field studies and reaction-diffusion models. J R Soc Interface 2008; 5:483-505. [PMID: 18211865 PMCID: PMC2408372 DOI: 10.1098/rsif.2007.1327] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Periodic travelling waves have been reported in a number of recent spatio-temporal field studies of populations undergoing multi-year cycles. Mathematical modelling has a major role to play in understanding these results and informing future empirical studies. We review the relevant field data and summarize the statistical methods used to detect periodic waves. We then discuss the mathematical theory of periodic travelling waves in oscillatory reaction-diffusion equations. We describe the notion of a wave family, and various ecologically relevant scenarios in which periodic travelling waves occur. We also discuss wave stability, including recent computational developments. Although we focus on oscillatory reaction-diffusion equations, a brief discussion of other types of model in which periodic travelling waves have been demonstrated is also included. We end by proposing 10 research challenges in this area, five mathematical and five empirical.
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Affiliation(s)
- Jonathan A Sherratt
- Department of Mathematics and, Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Edinburgh, UK.
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PIERTNEY STUARTB, LAMBIN XAVIER, MACCOLL ANDREWDC, LOCK KERRY, BACON PHILIPJ, DALLAS JOHNF, LECKIE FIONA, MOUGEOT FRANCOIS, RACEY PAULA, REDPATH STEVE, MOSS ROBERT. Temporal changes in kin structure through a population cycle in a territorial bird, the red grouse Lagopus lagopus scoticus. Mol Ecol 2008; 17:2544-51. [DOI: 10.1111/j.1365-294x.2008.03778.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Torr P, Spiridonov SE, Heritage S, Wilson MJ. Habitat associations of two entomopathogenic nematodes: a quantitative study using real-time quantitative polymerase chain reactions. J Anim Ecol 2007; 76:238-45. [PMID: 17302831 DOI: 10.1111/j.1365-2656.2006.01196.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Despite nematodes being the most abundant animals on earth, very few animal ecologists study them, probably because of the difficulties of identifying them to species by morphological methods. 2. A group of nematodes that are important both ecologically and economically is the entomopathogenic nematodes, which play a key role in regulating soil food webs and are sold throughout the world as biological insecticides, yet for which very little is known of their population ecology. 3. A novel detection and quantification method was developed for soil nematodes using real-time polymerase chain reaction (PCR), and the technique was used to estimate numbers of two closely related species of entomopathogenic nematodes, Steinernema kraussei and S. affine in 50 soil samples from 10 sites in Scotland representing two distinct habitats (woodland and grassland). 4. There was a high degree of correlation between our molecular and traditional morphological estimates of population size and our data clearly showed that Steinernema affine occurred only in grassland areas, whereas S. kraussei was found in grassland and woodland samples to a similar degree. 5. Real-time PCR offers a rapid and accurate method of detecting individual nematode species from soil samples without the need for a specialist taxonomist, and has much potential for use in studies of nematode population ecology.
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Affiliation(s)
- Peter Torr
- School of Biological Sciences, University of Aberdeen, Aberdeen, UK
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26
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Redpath S, Mougeot F, Leckie F, Evans S. The effects of autumn testosterone on survival and productivity in red grouse, Lagopus lagopus scoticus. Anim Behav 2006. [DOI: 10.1016/j.anbehav.2005.08.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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27
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Redpath SM, Mougeot F, Leckie FM, Elston DA, Hudson PJ. Testing the role of parasites in driving the cyclic population dynamics of a gamebird. Ecol Lett 2006; 9:410-8. [PMID: 16623726 DOI: 10.1111/j.1461-0248.2006.00895.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of parasites in regulating populations has been the subject of debate. We tested whether parasites caused population cycles in red grouse by manipulating parasite intensities in four, paired 1 km(2) study areas during cyclic population declines over 4 years. Parasite reductions led to (1) larger grouse broods, (2) higher population densities in both autumn and spring, (3) reduced autumn population declines in one of two regions, and (4) reduced spring declines, but only in the first year. We infer that a single trophic interaction between a parasite and its host does not explain cyclic dynamics in spring breeding density in this species, although it contributed to the start of a cyclic decline. Another process was operating to drive the populations down. Together with our other results these findings emphasize that both trophic and intrinsic processes may act within populations to cause unstable dynamics.
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Mougeot F, Dawson A, Redpath SM, Leckie F. Testosterone and autumn territorial behavior in male red grouse Lagopus lagopus scoticus. Horm Behav 2005; 47:576-84. [PMID: 15811360 DOI: 10.1016/j.yhbeh.2004.11.021] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 11/24/2004] [Accepted: 11/24/2004] [Indexed: 10/25/2022]
Abstract
In many bird species, males exhibit territorial aggression outside the breeding season, when testosterone concentrations are low and may not regulate territorial behaviors. The hormonal regulation of aggression at this time of year has only been studied in passerine birds. Here, we investigated the role of testosterone in the regulation of aggression in a non-passerine bird, the red grouse Lagopus lagopus scoticus. Male red grouse are aggressive in early spring when breeding starts, in autumn when they establish territories, and sporadically through much of the winter. We first describe seasonal variations in plasma testosterone concentrations and in the size of males' sexual ornaments, their red combs, which relates to aggressiveness. Testosterone concentrations and comb size were correlated. Both increased in autumn to a peak in October, and then increased again in spring, to a greater peak in early April. Secondly, we experimentally investigated the effects of testosterone, and of an anti-androgen (flutamide) used in combination with an aromatase inhibitor (ATD), on autumn territorial behavior. Males were treated with either empty implants, as controls (C-males), testosterone implants (T-males), or with flutamide and ATD implants (FA-males). One month after implanting, both T- and FA-males had higher concentrations of testosterone than C-males. Comb size, aggressive call rate, and response to playbacks of territorial call all significantly increased in T-males. However, the increase in testosterone in FA-males did not increase comb size or aggressive behavior. In the following spring, after the content of implants was used, FA-males had significantly lower testosterone than C-males, and had a reduced seasonal increase in comb size. The results suggest that testosterone plays a significant role in regulating red grouse aggressive behavior in autumn. However, the observation that flutamide and ATD treatment did not reduce territorial behavior, suggests that estradiol may also be involved in the regulation of non-breeding aggression.
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Affiliation(s)
- François Mougeot
- Centre for Ecology and Hydrology, Banchory, Aberdeenshire AB31 4BW, UK.
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Mougeot F, Evans SA, Redpath SM. Interactions between population processes in a cyclic species: parasites reduce autumn territorial behaviour of male red grouse. Oecologia 2005; 144:289-98. [PMID: 15891828 DOI: 10.1007/s00442-005-0080-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Accepted: 03/01/2005] [Indexed: 01/17/2023]
Abstract
The causes of population cycles fascinate and perplex ecologist. Most work have focused on single processes, whether extrinsic or intrinsic, more rarely on how different processes might interact to cause or mould the unstable population dynamics. In red grouse (Lagopus lagopus scoticus), two causal mechanisms have been supported: territorial behaviour (changes in autumn aggressiveness) and parasites (parasite induced reduction in fecundity). Here, we report on how these two regulatory processes might interact, by testing whether the parasite suspected to cause the grouse cycles, the nematode Trichostrongylus tenuis, reduces male autumn territorial behaviour. We either treated males with an anthelmintic, to remove parasites (dosed or D-males), or challenged them with infective T. tenuis larvae, to increase parasite intensity (challenged or C-males). We first show that dosing was effective in removing T. tenuis parasites, while parasite intensities increased in challenged birds during the autumn. Because old males initially had more parasites than young males, the treatments generated greater differences in parasite intensity in old than in young males. We also show that various aspects of territorial behaviour (increase in testosterone-dependent comb size in autumn, territorial call rate, likelihood of winning territorial interactions and over-winter survival) were significantly higher in dosed than in challenged males, but in old birds only. Our data thus supported the hypothesis that parasites reduce male aggressiveness during the autumn territorial contests, and could thereby influence recruitment. Our results also highlight that the territorial behaviour of young males, which have fewer parasites, is not as limited by parasites as that of old, previously territorial males. We discuss the implications of these findings for our understanding of the processes regulating red grouse populations and causing their complex, unstable population dynamics.
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Affiliation(s)
- Franccois Mougeot
- Centre for Ecology and Hydrology, Hill of Brathens, AB31 4BW, Banchory, Scotland, UK.
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