Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

Klemme, Ines; Soulsbury, Carl D.; Henttonen, Heikki

doi:10.1098/rspb.2014.1291

Cited by 13 publications

(5 citation statements)

References 70 publications

(84 reference statements)

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“…Sexually selected strategies are adjusted by ecological factors such as food restriction (Janicke, David & Chapuis, ), and RTS or ejaculate expenditure can be readily altered by food resources available to males (e.g. the dung fly Scatophaga (= Scathophaga ) stercoraria Simmons & Parker, ; the moth Plodia interpunctella , Gage, ; the tick Amblyomma cajennense , Anholeto et al ., ; voles, Klemme, Soulsbury & Henttonen, ; the moth Achroia grisella , Cordes et al ., ). The fact that GSI changes often quite radically through the year in many seasonal breeding invertebrates and vertebrates, and is so much used by biologists to determine peak breeding season, also implies a trade‐off between soma and gonads.…”

Section: Trade‐offsmentioning

confidence: 97%

The evolution of expenditure on testes

Parker

2016

Journal of Zoology

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Evolutionary theory for expenditure on gonads attracted little attention until studies in the past 3-4 decades of allocation to male and female function in hermaphrodites, and of relative testes size (RTS) in animals with separate sexes. RTS appears to have varied enormously over evolutionary time, from extremely high (over 40%) in some broadcast spawners to less than 1% in some taxa with copulation and internal fertilization. Reasons for this wide evolutionary diversity in testes expenditure deserve attention. Sperm demand (the product of expenditure per ejaculate and mating rate) increases expenditure on testes, and is moulded by a number of selective forces: sperm competition, mating rate and sperm limitation are identified as the three typically most powerful. Trade-offs between somatic and testes expenditures can be complex, particularly those between pre-and post-copulatory expenditure. Theoretical models predict that RTS should correlate positively with sperm demand, and there is much evidence from many taxa that RTS increases with sperm competition level. The relation between RTS and expenditure on each ejaculate is predicted to be positive over low sperm competition (risk) levels, and negative over high (intensity) sperm competition levels. Sexual cascade logic suggests that gonad expenditure should be high and equal for the two sexes soon after the early evolution of anisogamy, but should diverge widely through evolutionary time, with RTS reducing notably in those taxa that have evolved advanced mobility and internal fertilization.

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Section: Trade‐offsmentioning

confidence: 97%

The evolution of expenditure on testes

Parker

2016

Journal of Zoology

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“…Males reared in the presence of [more] rivals or their cues have been shown to develop larger testes (Gage, ; Stockley & Seale, ; Scharer & Ladurner, ; Tan et al ., ; Bailey et al ., ), a faster rate of spermatogenesis (Giannakara et al ., ), larger (Bailey et al ., ; Bretman et al ., ) or smaller (Sloan et al ., ) accessory glands, and better body condition (Bailey et al ., ; Simmons & Buzatto, ). In vertebrates, correlational evidence from natural populations has suggested that males may adjust their expenditure on sperm production according to environmental or social cues that are indicative of reproductive competition (Brown & Brown, ; Long & Montgomerie, ; Firman & Simmons, ; Dziminski et al ., ; Klemme et al ., ), whereas empirical studies that have manipulated the social environment to emulate different levels of reproductive competition during sexual development have produced mixed results (Evans & Magurran, ; Ramm & Stockley, ; Lemaitre et al ., ; Smith & Ryan, ; Firman et al ., ; Ramm et al ., ).…”

Section: Introductionmentioning

confidence: 99%

A competitive environment influences sperm production, but not testes tissue composition, in house mice

Firman

García‐González

Simmons

et al. 2018

J of Evolutionary Biology

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Due to the physiological cost of sperm production, males are expected to be prudent in their expenditure and adjust their investment according to current social conditions. Strategic adjustments in sperm expenditure during development can be made via changes in testes size, sperm production rates or testes tissue composition. Here, using house mice, we test the hypothesis that elevated sperm production is driven by a plastic response in the spatial organization of the testes. We reared males under different social conditions (competitive vs. noncompetitive) and quantified sperm number and the proportion of sperm-producing tissue within the testes. Further, because sperm quality is a critical determinant of competitive fertilization success, we used computer-assisted sperm analysis to quantify six sperm motility traits. Our investigation revealed that males reared in an environment with a perceived risk of reproductive competition produced more sperm in the absence of changes in testes morphology. We discuss this result in relation to fixed and flexible phenotypically plastic responses to future competitive conditions, and conclude that adaptive adjustments in sperm number in response to the social environment are likely attributable to variation in sperm production rate. Further, we found no difference in in vitro sperm motility parameters among males from the different social environment regimes. Overall, this investigation improves our understanding of the mechanisms of male plastic responses to reproductive competition experienced during sexual development.

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“…Other traits involved in mate searching that may also be favoured at low population densities include larger wings, more flight muscle and larger visual sensory organs [10,13,15]. Investment in these traits may be traded-off against other reproductive functions: for example, the risk of sperm competition may increase with population density, and males may respond with greater investment in sperm production [9,11,15,[25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Anticipatory flexibility: larval population density in moths determines male investment in antennae, wings and testes

2017

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Developmental plasticity provides individuals with a distinct advantage when the reproductive environment changes dramatically. Variation in population density, in particular, can have profound effects on male reproductive success. Females may be easier to locate in dense populations, but there may be a greater risk of sperm competition. Thus, males should invest in traits that enhance fertilization success over traits that enhance mate location. Conversely, males in less dense populations should invest more in structures that will facilitate mate location. In Lepidoptera, this may result in the development of larger antennae to increase the likelihood of detecting female sex pheromones, and larger wings to fly more efficiently. We explored the effects of larval density on adult morphology in the gum-leaf skeletonizer moth, , by manipulating both the number of larvae and the size of the rearing container. This experimental arrangement allowed us to reveal the cues used by larvae to assess whether absolute number or density influences adult responses. Male investment in testes size depended on the number of individuals, while male investment in wings and antennae depended upon larval density. By contrast, the size of female antennae and wings were influenced by an interaction of larval number and container size. This study demonstrates that male larvae are sensitive to cues that may reveal adult population density, and adjust investment in traits associated with fertilization success and mate detection accordingly.

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Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

Cited by 13 publications

References 70 publications

The evolution of expenditure on testes

The evolution of expenditure on testes

A competitive environment influences sperm production, but not testes tissue composition, in house mice

Anticipatory flexibility: larval population density in moths determines male investment in antennae, wings and testes

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