Correlated evolution of sexually selected traits: interspecific variation in ejaculates, sperm morphology, copulatory mate guarding, and body size in two sympatric species of garter snakes

2017 ◽  
Vol 71 (12) ◽  
Author(s):  
Christopher R. Friesen ◽  
Emily J. Uhrig ◽  
Ehren J. Bentz ◽  
Leslie A. Blakemore ◽  
Robert T. Mason
Keyword(s):  
Body Size ◽  
Sperm Morphology ◽  
Mate Guarding ◽  
Interspecific Variation ◽  
Sympatric Species ◽  
Garter Snakes ◽  
Correlated Evolution ◽  
Sexually Selected Traits ◽  
Selected Traits

scholarly journals Benefits of size dimorphism and copulatory silk wrapping in the sexually cannibalistic nursery web spider, Pisaurina mira

2016 ◽  
Vol 12 (2) ◽  
pp. 20150957 ◽  
Author(s):  
Alissa G. Anderson ◽  
Eileen A. Hebets
Keyword(s):  
Body Size ◽  
Relative Size ◽  
Male Reproductive Success ◽  
Male Fitness ◽  
Male Size ◽  
Treatment Groups ◽  
Web Spider ◽  
Sexually Selected Traits ◽  
Mate Acquisition ◽  
Selected Traits

In sexually cannibalistic animals, male fitness is influenced not only by successful mate acquisition and egg fertilization, but also by avoiding being eaten. In the cannibalistic nursery web spider, Pisaurina mira , the legs of mature males are longer in relation to their body size than those of females, and males use these legs to aid in wrapping a female's legs with silk prior to and during copulation. We hypothesized that elongated male legs and silk wrapping provide benefits to males, in part through a reduced likelihood of sexual cannibalism. To test this, we paired females of random size with males from one of two treatment groups—those capable of silk wrapping versus those incapable of silk wrapping. We found that males with relatively longer legs and larger body size were more likely to mate and were less likely to be cannibalized prior to copulation. Regardless of relative size, males capable of silk wrapping were less likely to be cannibalized during or following copulation and had more opportunities for sperm transfer (i.e. pedipalpal insertions). Our results suggest that male size and copulatory silk wrapping are sexually selected traits benefiting male reproductive success.

scholarly journals Cancer susceptibility and reproductive trade-offs: a model of the evolution of cancer defences

2015 ◽  
Vol 370 (1673) ◽  
pp. 20140220 ◽  
Author(s):  
Amy M. Boddy ◽  
Hanna Kokko ◽  
Felix Breden ◽  
Gerald S. Wilkinson ◽  
C. Athena Aktipis
Keyword(s):  
Cell Proliferation ◽  
Body Size ◽  
Cancer Susceptibility ◽  
Large Body ◽  
Large Body Size ◽  
Trade Off ◽  
Extrinsic Mortality ◽  
Sexually Selected Traits ◽  
Trade Offs ◽  
Selected Traits

The factors influencing cancer susceptibility and why it varies across species are major open questions in the field of cancer biology. One underexplored source of variation in cancer susceptibility may arise from trade-offs between reproductive competitiveness (e.g. sexually selected traits, earlier reproduction and higher fertility) and cancer defence. We build a model that contrasts the probabilistic onset of cancer with other, extrinsic causes of mortality and use it to predict that intense reproductive competition will lower cancer defences and increase cancer incidence. We explore the trade-off between cancer defences and intraspecific competition across different extrinsic mortality conditions and different levels of trade-off intensity, and find the largest effect of competition on cancer in species where low extrinsic mortality combines with strong trade-offs. In such species, selection to delay cancer and selection to outcompete conspecifics are both strong, and the latter conflicts with the former. We discuss evidence for the assumed trade-off between reproductive competitiveness and cancer susceptibility. Sexually selected traits such as ornaments or large body size require high levels of cell proliferation and appear to be associated with greater cancer susceptibility. Similar associations exist for female traits such as continuous egg-laying in domestic hens and earlier reproductive maturity. Trade-offs between reproduction and cancer defences may be instantiated by a variety of mechanisms, including higher levels of growth factors and hormones, less efficient cell-cycle control and less DNA repair, or simply a larger number of cell divisions (relevant when reproductive success requires large body size or rapid reproductive cycles). These mechanisms can affect intra- and interspecific variation in cancer susceptibility arising from rapid cell proliferation during reproductive maturation, intrasexual competition and reproduction.

scholarly journals Why the Static Allometry of Sexually-Selected Traits Is So Variable: The Importance of Function

2019 ◽  
Vol 59 (5) ◽  
pp. 1290-1302 ◽  
Author(s):  
Rafael Lucas Rodríguez ◽  
William G Eberhard
Keyword(s):  
Body Size ◽  
Body Part ◽  
Positive Allometry ◽  
Large Structures ◽  
Sexually Selected Traits ◽  
Body Sizes ◽  
Selected Traits ◽  
Courtship Signals ◽  
Aggressive Signals ◽  
Static Allometry

AbstractSexually-selected traits often show positive static allometry, with large individuals bearing disproportionately large structures. But many other sexually-selected traits show isometry or even negative allometry, with trait size varying relatively little with body size. We recently proposed that the functions of these traits (as aggressive signals, weapons, courtship signals, and contact courtship devices) determine their allometries. Positive allometry is generally favored for aggressive signals because aggressive signals are selected to emphasize body size (and thus fighting prowess). In contrast, the biomechanics of force application in weapons only sometimes select for positive allometry; the content of courtship signals is even less often related to body size; and contact courtship devices are selected to be relatively invariant across body sizes. Here we summarize the arguments in favor of this “functional allometry” hypothesis and expand a comparative test of its predictions. Our results indicate that sexual traits have the allometric slopes predicted by our hypothesis, regardless of which body part bears the structure.

scholarly journals Mating system and brain size in bats

2005 ◽  
Vol 273 (1587) ◽  
pp. 719-724 ◽  
Author(s):  
Scott Pitnick ◽  
Kate E Jones ◽  
Gerald S Wilkinson
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Multiple Mating ◽  
Brain Size ◽  
Evolutionary Relationship ◽  
Brain Evolution ◽  
Correlated Evolution ◽  
Mate Fidelity ◽  
Sexually Selected Traits ◽  
Selected Traits

The contribution of sexual selection to brain evolution has been little investigated. Through comparative analyses of bats, we show that multiple mating by males, in the absence of multiple mating by females, has no evolutionary impact on relative brain dimension. In contrast, bat species with promiscuous females have relatively smaller brains than do species with females exhibiting mate fidelity. This pattern may be a consequence of the demonstrated negative evolutionary relationship between investment in testes and investment in brains, both metabolically expensive tissues. These results have implications for understanding the correlated evolution of brains, behaviour and extravagant sexually selected traits.

scholarly journals The growth factor BMP11 is required for the development and evolution of a male exaggerated weapon and its associated fighting behavior in a water strider

PLoS Biology ◽  
2021 ◽  
Vol 19 (5) ◽  
pp. e3001157
Author(s):  
William Toubiana ◽  
David Armisén ◽  
Séverine Viala ◽  
Amélie Decaras ◽  
Abderrahman Khila
Keyword(s):  
Body Size ◽  
Growth Factor ◽  
The Body ◽  
Specific Factor ◽  
Male Body ◽  
Water Strider ◽  
Fighting Behavior ◽  
Sexually Selected Traits ◽  
Morphogenetic Protein ◽  
Selected Traits

Exaggerated sexually selected traits, often carried by males, are characterized by the evolution of hyperallometry, resulting in their disproportionate growth relative to the rest of the body among individuals of the same population. While the evolution of allometry has attracted much attention for centuries, our understanding of the developmental genetic mechanisms underlying its emergence remains fragmented. Here we conduct comparative transcriptomics of the legs followed by an RNA interference (RNAi) screen to identify genes that play a role in the hyperallometric growth of the third legs in the males of the water strider Microvelia longipes. We demonstrate that a broadly expressed growth factor, Bone Morphogenetic Protein 11 (BMP11, also known as Growth Differentiation Factor 11), regulates leg allometries through increasing the allometric slope and mean body size in males. In contrast, BMP11 RNAi reduced mean body size but did not affect slope either in the females of M. longipes or in the males and females of other closely related Microvelia species. Furthermore, our data show that a tissue-specific factor, Ultrabithorax (Ubx), increases intercept without affecting mean body size. This indicates a genetic correlation between mean body size and variation in allometric slope, but not intercept. Strikingly, males treated with BMP11 RNAi exhibited a severe reduction in fighting frequency compared to both controls and Ubx RNAi-treated males. Therefore, male body size, the exaggerated weapon, and the intense fighting behavior associated with it are genetically correlated in M. longipes. Our results support a possible role of pleiotropy in the evolution of allometric slope.

scholarly journals Microgeographic variation in body condition of three Mexican garter snakes in central Mexico

2018 ◽  
Author(s):  
Erika Valencia-Flores ◽  
Crystian S Venegas-Barrera ◽  
Victor Fajardo ◽  
Javier Manjarrez
Keyword(s):  
Body Size ◽  
Body Condition ◽  
Climatic Factors ◽  
Major Axis ◽  
Sympatric Species ◽  
Central Mexico ◽  
Garter Snakes ◽  
Good Body Condition ◽  
Microgeographic Variation ◽  
Similar Body

Background. Geographic variation in body size and condition can reveal differential local adaptation to resource availability or climatic factors. Body size and condition are related to fitness in garter snakes (Thamnophis), thus good body condition may increase survival, fecundity in females, and mating success in males. Sympatric species are predicted to exhibit similar body condition when they experience similar environmental conditions. We focused on interspecific and geographical variation in body size and condition in three sympatric Mexican garter snakes from the highlands of Central Mexico. Methods. We assessed SVL, mass, and body condition (obtained from Major axis linear regression of ln-transformed body mass on ln-transformed SVL) in adults and juveniles of both sexes of Thamnophis eques, T. melanogaster, and T. scalaris sampled at different locations and over a 20-year period. Results. We provide a heterogeneous pattern of sexual and ontogenic reproductive status variations of body size and condition among local populations. Each garter snake species shows locations with good and poor body condition; juvenile snakes show similar body condition between populations, adults show varying body condition between populations, and adults also show sexual differences in body condition. We discuss variations in body condition as possibly related to the snakes’ life cycle differences.

scholarly journals Are sexually selected traits affected by a poor environment early in life?

2016 ◽  
Author(s):  
Regina Vega-Trejo ◽  
Michael D. Jennions ◽  
Megan L. Head
Keyword(s):  
Body Size ◽  
Fitness Costs ◽  
Rate Dependent ◽  
Sexually Selected Traits ◽  
Catching Up ◽  
Limited Food ◽  
Additional Costs ◽  
Nutritional Environment ◽  
Selected Traits

AbstractConditions experienced early in life can affect key life-history traits. Individuals that experience a poor nutritional environment early in life can reduce potential costs by delaying sexual maturation. The direct costs of delaying maturation are well known (i.e. delayed onset of breeding), but individuals can also face additional costs as adults. Some of these ‘hidden costs’ accrue due to cryptic morphological and physiological changes. In mosquitofish (Gambusia holbrooki), males with limited food intake early in life delay maturation to eventually reach a similar adult body size to their well-fed counterparts (‘catch-up growth’). Here we tested whether a poor diet early in life incurs hidden costs due to reduced expression of sexually selected male traits (genital size and ejaculate traits). We found that diet early in life significantly influenced sperm reserves and replenishment rate due to age and development-rate dependent effects. Although catching-up in body size ameliorates some of the costs of a poor start in life for males, our findings suggest that long-term fitness costs might arise because of sexually selection against these males. Our results highlight that fitness costs of a poor start in life can extend into adulthood.

scholarly journals The allometry between secondary sexual traits and body size is nonlinear among cervids

2014 ◽  
Vol 10 (3) ◽  
pp. 20130869 ◽  
Author(s):  
J. F. Lemaître ◽  
C. Vanpé ◽  
F. Plard ◽  
J. M. Gaillard
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Life History Theory ◽  
Male Body ◽  
Allometric Relationships ◽  
Secondary Sexual Traits ◽  
Sexually Selected Traits ◽  
Large Size ◽  
Antler Size ◽  
Selected Traits

Allometric relationships between sexually selected traits and body size have been extensively studied in recent decades. While sexually selected traits generally display positive allometry, a few recent reports have suggested that allometric relationships are not always linear. In male cervids, having both long antlers and large size provides benefits in terms of increased mating success. However, such attributes are costly to grow and maintain, and these costs might constrain antler length from increasing at the same rate as body mass in larger species if the quantity of energy that males can extract from their environment is limiting. We tested for possible nonlinearity in the relationship between antler size and body mass (on a log–log scale) among 31 cervids and found clear deviation from linearity in the allometry of antler length. Antler length increased linearly until a male body mass threshold at approximately 110 kg. Beyond this threshold, antler length did not change with increasing mass. We discuss this evidence of nonlinear allometry in the light of life-history theory and stress the importance of testing for nonlinearity when studying allometric relationships.

scholarly journals Greater sperm complexity in the Australasian old endemic rodents (Tribe: Hydromyini) is associated with increased levels of inter-male sperm competition

2017 ◽  
Vol 29 (5) ◽  
pp. 921 ◽  
Author(s):  
Hanna J. McLennan ◽  
Stefan Lüpold ◽  
Pete Smissen ◽  
Kevin C. Rowe ◽  
William G. Breed
Keyword(s):  
Sperm Competition ◽  
Sperm Morphology ◽  
Tail Length ◽  
Sperm Head ◽  
Sperm Tail ◽  
Apical Hook ◽  
Sexually Selected Traits ◽  
Male Sperm ◽  
Murid Rodents ◽  
Selected Traits

Spermatozoa exhibit considerable interspecies morphological variation across mammals, especially among murid rodents. In Australasia, most murids in the tribe Hydromyini have a spermatozoon with a highly complex head exhibiting an apical hook, characteristic of most murids, and two projections that extend from its upper concave surface, the ventral processes. In the present study we performed a phylogenetically controlled comparison of sperm morphology across 45 species of hydromyine rodents to test the hypothesis that the length and angle of both the apical hook and ventral processes, as well as the length of the sperm tail, increase with relative testes mass as a proxy for differences in levels of inter-male sperm competition. Although both sperm head protrusions exhibited considerable variation in their length and angle across species, only the angles increased significantly in relation to relative testes mass. Further, the length of the sperm flagellum was positively associated with relative testes mass. These results suggest that, in hydromyine rodents, the angle of the apical hook and ventral processes of the sperm head, as well as the sperm tail length, are likely to be sexually selected traits. The possible functional significance of these findings is briefly discussed.

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