Sexual size dimorphism（SSD） is a widespread phenomenon among animals, and whose evolution and maintenance has been a central topic in evolutionary biology since Darwin＇s time. SSD varies in direction among the majo...Sexual size dimorphism（SSD） is a widespread phenomenon among animals, and whose evolution and maintenance has been a central topic in evolutionary biology since Darwin＇s time. SSD varies in direction among the major taxonomic groups of animals and even within the same groups. In anurans, female biased SSD is the rule in many lineages, whereas male biased SSD is a rare phenomenon. In this paper, we analyze whether SSD exists inLeptobrachium leishanensis by comparing morphological characteristics between the sexes. Our results show that all six morphological characteristics measured are significantly different between the sexes. Males are significantly larger than females, indicating that the male biased SSD of this species is apparent. The size of the nuptial spines, a special secondary sex trait of males, is significantly and positively correlated with body size. We suggest that the resource defense polygyny mating system and parental care behavior may be explanations for the evolution of male biased SSD and nuptial spine development in this species.展开更多
Attendance patterns are a key factor affecting sexual selection and mating systems in lekbreeding species.However,there are few systematic studies on attendance patterns in lek-breeding anurans.In this study,we monito...Attendance patterns are a key factor affecting sexual selection and mating systems in lekbreeding species.However,there are few systematic studies on attendance patterns in lek-breeding anurans.In this study,we monitored a population of Omei treefrogs(Rhacophorus omeimontis) for four consecutive years to reveal in detail the effects of attendance patterns on mating systems.We found that(1) female nightly attendance was affected by male nightly attendance,and operational sex ratios(determined by male and female nightly attendance) ultimately determined the extent of female polyandry;(2) males surviving more than one breeding season maintained high chorus attendance and mating success,suggesting that male chorus attendance is a good predictor of male genetic quality;(3) the distributions of male mating success were not significantly different from a Poisson distribution,indicating a random mating pattern;and male mating success was not related to body size(size-assortative mating was not evident) but was significantly correlated with chorus attendance.Since the chorus attendance is a predictor of male genetic quality,females performing random mating were more likely to mate with more frequently present males and could therefore gain indirect benefits from mating with higher-than-average quality males,thereby producing good offspring without incurring the significant costs involved in prolonged searching for,and assessing males.Our systematic survey on the relationship between attendance patterns and the lek mating system in R.omeimontis could help us better understand in-depth anuran lek mating systems.展开更多
The worldwide declines in amphibian populations have largely been caused by infectious fungi and bacteria. Given that vertebrate immunity against these extracellular pathogens is primarily functioned by the major hist...The worldwide declines in amphibian populations have largely been caused by infectious fungi and bacteria. Given that vertebrate immunity against these extracellular pathogens is primarily functioned by the major histocompatibility complex（MHC） class Ⅱ molecules, the characterization and the evolution of amphibian MHC class Ⅱ genes have attracted increasing attention. The polymorphism of MHC class Ⅱ genes was found to be correlated with susceptibility to fungal pathogens in many amphibian species, suggesting the importance of studies on MHC class Ⅱ genes for amphibians. However, such studies on MHC class Ⅱ gene evolution have rarely been conducted on amphibians in China. In this study, we chose Omei treefrog（Rhacophorus omeimontis）, which lived moist environments easy for breeding bacteria, to study the polymorphism of its MHC class Ⅱ genes and the underlying evolutionary mechanisms. We amplified the entire MHC class ⅡB exon 2 sequence in the R. omeimontis using newly designed primers. We detected 102 putative alleles in 146 individuals. The number of alleles per individual ranged from one to seven, indicating that there are at least four loci containing MHC class ⅡB genes in R. omeimontis. The allelic polymorphism estimated from the 102 alleles in R. omeimontis was not high compared to that estimated in other anuran species. No significant gene recombination was detected in the 102 MHC class ⅡB exon 2 sequences. In contrast, both gene duplication and balancing selection greatly contributed to the variability in MHC class ⅡB exon 2 sequences of R. omeimontis. This study lays the groundwork for the future researches to comprehensively analyze the evolution of amphibian MHC genes and to assess the role of MHC gene polymorphisms in resistance against extracellular pathogens for amphibians in China.展开更多
Group spawning, polyandry reproductive behaviors, and multiple paternity are increasingly reported in anuran species. The Omei treefrog （Rhacophorus omeimontis）, endemic to subtropical and mountainous forests of cen...Group spawning, polyandry reproductive behaviors, and multiple paternity are increasingly reported in anuran species. The Omei treefrog （Rhacophorus omeimontis）, endemic to subtropical and mountainous forests of central and southwestern China, is a polyandrous lek-patterned breeder commonly showing multiple males-one female matings during the breeding season. To detect the traits of social and genetic polyandry in this species and explore the relationships between these traits, we investigated the breeding behaviors of a population of R. omeimontis in the Fengtongzhai National Nature Reserve, Baoxing County, Sichuan, China. We conducted paternity analyses using six microsatellite genetic markers. A total of 30 matings were recorded in the field （four monogamous pairs and 26 spawning groups）. Our results revealed high proportions of social polyandry （86.7%） and multiple paternity （70.0%） and the numbers of joining males and genetic fathers among matings ranged from 1 to 8 and from 1 to 4, respectively. There was a significantly positive correlation between the intensities of social and genetic polyandry, indicating that multiple males-one female breeding behaviors could be an important promoter of multiple paternity. We considered the intense social polyandry and multiple paternity as consequences of intense male-male competition under a male-biased sex ratio and genetic benefits pursuing of the females. However, the proportion of genetic fathers in a spawning decreased with the increase of joining male number and most of their offspring belonged to a few males. This might be caused by a ＂making the best of a bad lot＂ reproductive strategy of the inferior male individuals.展开更多
Sexual selection is critical to both reproduction and evolution.The effects of male–male competition and female choice regarding body size have been examined in a large number of taxa,including toad species.Males and...Sexual selection is critical to both reproduction and evolution.The effects of male–male competition and female choice regarding body size have been examined in a large number of taxa,including toad species.Males and females have different optimal reproductive strategies,achieving breeding advantages in discrepant ways.Further,the relative contributions of intra-and inter-sexual size selection vary among species.Thus,to understand the mechanisms affecting mating success,it is important to consider both male–male and male–female interactions simultaneously and elucidate their interrelationship.In this study,we measured body sizes of all mated and unmated individuals in a population of Asiatic toad(Bufo gargarizans)and counted fertilized eggs of several clutches.Based on correlation and regression techniques,we tested for female choice and intra-sexual competition among males relative to body size gradients,and we compared the relative importance of these two processes for mating success.Our results reveal that male–male competition and female choice simultaneously contribute to sexual selection in toads.Furthermore,both interactions are most intense among smaller toads.The synergistic trends of male–male competition and female choice support the mutual mate choice hypothesis and works to stabilize body size in B.gargarizans.Normal distributions of breeding success relative to body size were detected for both sexes,suggesting that medium-sized individuals enjoy a reproductive advantage in the population studied.展开更多
Threatened species typically have a small or declining population size,which make them highly susceptible to loss of genetic diversity through genetic drift and inbreeding.Genetic diversity determines the evolutionary...Threatened species typically have a small or declining population size,which make them highly susceptible to loss of genetic diversity through genetic drift and inbreeding.Genetic diversity determines the evolutionary potential of a species;therefore,maintaining the genetic diversity of threatened species is essential for their conservation.In this study,we assessed the genetic diversity of the adaptive major histocompatibility complex(MHC)genes in an endangered and narrowly distributed amphibian species,Leptobrachium leishanense in Southwest China.We compared the genetic variation of MHC class I genes with that observed in neutral markers(5 microsatellite loci and cytochrome b gene)to elucidate the relative roles of genetic drift and natural selection in shaping the current MHC polymorphism in this species.We found a high level of genetic diversity in this population at both MHC and neutral markers compared with other threatened amphibian species.Historical positive selection was evident in the MHC class I genes.The higher allelic richness in MHC markers compared with that of microsatellite loci suggests that selection rather than genetic drift plays a prominent role in shaping the MHC variation pattern,as drift can affect all the genome in a similar way but selection directly targets MHC genes.Although demographic analysis revealed no recent bottleneck events in L.leishanense,additional population decline will accelerate the dangerous status for this species.We suggest that the conservation management of L.leishanense should concentrate on maximizing the retention of genetic diversity through preventing their continuous population decline.Protecting their living habitats and forbidding illegal hunting are the most important measures for conservation of L.leishanense.展开更多
基金supported by National Natural Science Foundation of China(No.31270425,No.31470442)
文摘Sexual size dimorphism（SSD） is a widespread phenomenon among animals, and whose evolution and maintenance has been a central topic in evolutionary biology since Darwin＇s time. SSD varies in direction among the major taxonomic groups of animals and even within the same groups. In anurans, female biased SSD is the rule in many lineages, whereas male biased SSD is a rare phenomenon. In this paper, we analyze whether SSD exists inLeptobrachium leishanensis by comparing morphological characteristics between the sexes. Our results show that all six morphological characteristics measured are significantly different between the sexes. Males are significantly larger than females, indicating that the male biased SSD of this species is apparent. The size of the nuptial spines, a special secondary sex trait of males, is significantly and positively correlated with body size. We suggest that the resource defense polygyny mating system and parental care behavior may be explanations for the evolution of male biased SSD and nuptial spine development in this species.
基金supported by the National Natural Science Foundation of China(No.31470442)。
文摘Attendance patterns are a key factor affecting sexual selection and mating systems in lekbreeding species.However,there are few systematic studies on attendance patterns in lek-breeding anurans.In this study,we monitored a population of Omei treefrogs(Rhacophorus omeimontis) for four consecutive years to reveal in detail the effects of attendance patterns on mating systems.We found that(1) female nightly attendance was affected by male nightly attendance,and operational sex ratios(determined by male and female nightly attendance) ultimately determined the extent of female polyandry;(2) males surviving more than one breeding season maintained high chorus attendance and mating success,suggesting that male chorus attendance is a good predictor of male genetic quality;(3) the distributions of male mating success were not significantly different from a Poisson distribution,indicating a random mating pattern;and male mating success was not related to body size(size-assortative mating was not evident) but was significantly correlated with chorus attendance.Since the chorus attendance is a predictor of male genetic quality,females performing random mating were more likely to mate with more frequently present males and could therefore gain indirect benefits from mating with higher-than-average quality males,thereby producing good offspring without incurring the significant costs involved in prolonged searching for,and assessing males.Our systematic survey on the relationship between attendance patterns and the lek mating system in R.omeimontis could help us better understand in-depth anuran lek mating systems.
基金supported by the National Natural Science Foundation of China(No.31201713,No.31270425 and No.31470442)
文摘The worldwide declines in amphibian populations have largely been caused by infectious fungi and bacteria. Given that vertebrate immunity against these extracellular pathogens is primarily functioned by the major histocompatibility complex（MHC） class Ⅱ molecules, the characterization and the evolution of amphibian MHC class Ⅱ genes have attracted increasing attention. The polymorphism of MHC class Ⅱ genes was found to be correlated with susceptibility to fungal pathogens in many amphibian species, suggesting the importance of studies on MHC class Ⅱ genes for amphibians. However, such studies on MHC class Ⅱ gene evolution have rarely been conducted on amphibians in China. In this study, we chose Omei treefrog（Rhacophorus omeimontis）, which lived moist environments easy for breeding bacteria, to study the polymorphism of its MHC class Ⅱ genes and the underlying evolutionary mechanisms. We amplified the entire MHC class ⅡB exon 2 sequence in the R. omeimontis using newly designed primers. We detected 102 putative alleles in 146 individuals. The number of alleles per individual ranged from one to seven, indicating that there are at least four loci containing MHC class ⅡB genes in R. omeimontis. The allelic polymorphism estimated from the 102 alleles in R. omeimontis was not high compared to that estimated in other anuran species. No significant gene recombination was detected in the 102 MHC class ⅡB exon 2 sequences. In contrast, both gene duplication and balancing selection greatly contributed to the variability in MHC class ⅡB exon 2 sequences of R. omeimontis. This study lays the groundwork for the future researches to comprehensively analyze the evolution of amphibian MHC genes and to assess the role of MHC gene polymorphisms in resistance against extracellular pathogens for amphibians in China.
基金supported by the National Natural Science Foundation of China(No.31470442)
文摘Group spawning, polyandry reproductive behaviors, and multiple paternity are increasingly reported in anuran species. The Omei treefrog （Rhacophorus omeimontis）, endemic to subtropical and mountainous forests of central and southwestern China, is a polyandrous lek-patterned breeder commonly showing multiple males-one female matings during the breeding season. To detect the traits of social and genetic polyandry in this species and explore the relationships between these traits, we investigated the breeding behaviors of a population of R. omeimontis in the Fengtongzhai National Nature Reserve, Baoxing County, Sichuan, China. We conducted paternity analyses using six microsatellite genetic markers. A total of 30 matings were recorded in the field （four monogamous pairs and 26 spawning groups）. Our results revealed high proportions of social polyandry （86.7%） and multiple paternity （70.0%） and the numbers of joining males and genetic fathers among matings ranged from 1 to 8 and from 1 to 4, respectively. There was a significantly positive correlation between the intensities of social and genetic polyandry, indicating that multiple males-one female breeding behaviors could be an important promoter of multiple paternity. We considered the intense social polyandry and multiple paternity as consequences of intense male-male competition under a male-biased sex ratio and genetic benefits pursuing of the females. However, the proportion of genetic fathers in a spawning decreased with the increase of joining male number and most of their offspring belonged to a few males. This might be caused by a ＂making the best of a bad lot＂ reproductive strategy of the inferior male individuals.
基金supported by the National Natural Science Foundation of China(31071934)
文摘Sexual selection is critical to both reproduction and evolution.The effects of male–male competition and female choice regarding body size have been examined in a large number of taxa,including toad species.Males and females have different optimal reproductive strategies,achieving breeding advantages in discrepant ways.Further,the relative contributions of intra-and inter-sexual size selection vary among species.Thus,to understand the mechanisms affecting mating success,it is important to consider both male–male and male–female interactions simultaneously and elucidate their interrelationship.In this study,we measured body sizes of all mated and unmated individuals in a population of Asiatic toad(Bufo gargarizans)and counted fertilized eggs of several clutches.Based on correlation and regression techniques,we tested for female choice and intra-sexual competition among males relative to body size gradients,and we compared the relative importance of these two processes for mating success.Our results reveal that male–male competition and female choice simultaneously contribute to sexual selection in toads.Furthermore,both interactions are most intense among smaller toads.The synergistic trends of male–male competition and female choice support the mutual mate choice hypothesis and works to stabilize body size in B.gargarizans.Normal distributions of breeding success relative to body size were detected for both sexes,suggesting that medium-sized individuals enjoy a reproductive advantage in the population studied.
基金This study was supported by the National Natural Science Foundation of China(No.31201713,No.31270425)the research funds from CCNU(No.CCNU14B01001).
文摘Threatened species typically have a small or declining population size,which make them highly susceptible to loss of genetic diversity through genetic drift and inbreeding.Genetic diversity determines the evolutionary potential of a species;therefore,maintaining the genetic diversity of threatened species is essential for their conservation.In this study,we assessed the genetic diversity of the adaptive major histocompatibility complex(MHC)genes in an endangered and narrowly distributed amphibian species,Leptobrachium leishanense in Southwest China.We compared the genetic variation of MHC class I genes with that observed in neutral markers(5 microsatellite loci and cytochrome b gene)to elucidate the relative roles of genetic drift and natural selection in shaping the current MHC polymorphism in this species.We found a high level of genetic diversity in this population at both MHC and neutral markers compared with other threatened amphibian species.Historical positive selection was evident in the MHC class I genes.The higher allelic richness in MHC markers compared with that of microsatellite loci suggests that selection rather than genetic drift plays a prominent role in shaping the MHC variation pattern,as drift can affect all the genome in a similar way but selection directly targets MHC genes.Although demographic analysis revealed no recent bottleneck events in L.leishanense,additional population decline will accelerate the dangerous status for this species.We suggest that the conservation management of L.leishanense should concentrate on maximizing the retention of genetic diversity through preventing their continuous population decline.Protecting their living habitats and forbidding illegal hunting are the most important measures for conservation of L.leishanense.
