Penises play a key role in sperm transport and in stimulating female genitals.This should impact post-copulatory competition,and expose penis characteristics to sexual selective pressures.Studies of male genitalia hav...Penises play a key role in sperm transport and in stimulating female genitals.This should impact post-copulatory competition,and expose penis characteristics to sexual selective pressures.Studies of male genitalia have repeatedly reported negative static allometries,which mean that,within species,large males have disproportionally small genitals when compared with smaller individuals.Males of some sperm-storing bat species may stand as an exception to such a pattern by arousing from hibernation to copulate with torpid females.The selection for large penises might take place,if a long organ provides advantages during post-copulatory competition and/or if females have evolved mechanisms allowing the choice of sire,relying on characters other than pre-copulatory traits(e.g.,penis size).In this study,we measured dimensions of the erected penis in 4 sperm-storing bat species.Furthermore,we collected sperm and evaluated the link between penis dimensions and sperm velocity.Our results revealed steep allometric slopes of the erected penis length in Barbastella barbastellus and an inverse allometry of penis head width in Myotis nattereri.More detailed studies of copulatory behavior are urgently needed to explain the range of observed scaling relations.Furthermore,penis head width correlates with sperm velocity in Plecotus auritus.For this last species,we propose that penis shape might act as a marker of male fertility.展开更多
Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and ...Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and environmental factors can influence segregation of sexes and sex ratios,many of which originate with density-dependent processes.Departure from 50:50 sex ratios of double-crested cormorants(Phalacrocorax auritus)collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer’s weighted Z-tests.In addition,a specifically-designed randomization test was used to evaluate density-dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21-year period.Cormorants collected from breeding colonies were strongly male-biased,whereas cormorants collected from feeding flocks were slightly biased toward females.Cormorants were partly segregated by sex on the wintering grounds,with significantly more males found in areas with intensive channel catfish aquaculture.The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected:more male embryos were produced during rapid population growth,whereas at maximum nesting number more female embryos were produced.Once populations stabilized,the sex ratio was more equal.This examination of sex ratios indicates that different management methods and locations result in sex-biased culling of cormorants.Sex-biased culling in cormorants could make population reduction efforts more efficient and reduce overall take.We suggest further research to examine density-dependent effects on primary sex ratios documented here.展开更多
基金This project was financed by the Swiss Science Foundation(grant nb.P2BEP3_168709)N.J.F.and by the National Science Center,Poland(grant nb.DEC-2013/10/E/NZ8/00725)。
文摘Penises play a key role in sperm transport and in stimulating female genitals.This should impact post-copulatory competition,and expose penis characteristics to sexual selective pressures.Studies of male genitalia have repeatedly reported negative static allometries,which mean that,within species,large males have disproportionally small genitals when compared with smaller individuals.Males of some sperm-storing bat species may stand as an exception to such a pattern by arousing from hibernation to copulate with torpid females.The selection for large penises might take place,if a long organ provides advantages during post-copulatory competition and/or if females have evolved mechanisms allowing the choice of sire,relying on characters other than pre-copulatory traits(e.g.,penis size).In this study,we measured dimensions of the erected penis in 4 sperm-storing bat species.Furthermore,we collected sperm and evaluated the link between penis dimensions and sperm velocity.Our results revealed steep allometric slopes of the erected penis length in Barbastella barbastellus and an inverse allometry of penis head width in Myotis nattereri.More detailed studies of copulatory behavior are urgently needed to explain the range of observed scaling relations.Furthermore,penis head width correlates with sperm velocity in Plecotus auritus.For this last species,we propose that penis shape might act as a marker of male fertility.
文摘Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and environmental factors can influence segregation of sexes and sex ratios,many of which originate with density-dependent processes.Departure from 50:50 sex ratios of double-crested cormorants(Phalacrocorax auritus)collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer’s weighted Z-tests.In addition,a specifically-designed randomization test was used to evaluate density-dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21-year period.Cormorants collected from breeding colonies were strongly male-biased,whereas cormorants collected from feeding flocks were slightly biased toward females.Cormorants were partly segregated by sex on the wintering grounds,with significantly more males found in areas with intensive channel catfish aquaculture.The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected:more male embryos were produced during rapid population growth,whereas at maximum nesting number more female embryos were produced.Once populations stabilized,the sex ratio was more equal.This examination of sex ratios indicates that different management methods and locations result in sex-biased culling of cormorants.Sex-biased culling in cormorants could make population reduction efforts more efficient and reduce overall take.We suggest further research to examine density-dependent effects on primary sex ratios documented here.
