Study On The Morphological Characteristics And The Variation In Life-history Traits Of Tylototriton Shanjing In Two Geographical Populations

The variation of the animal morphological characteristics and life-history traits is important to the life-history evolution theory research.The life-history of amphibians is very complex.The morphological characteristics and life-history traits of an animal species are the result of long-term adaptation to their living environment.It has an important significance for understanding the species-evolutionary mechanism and amphibian ecological adaptability to study on the variation of the morphological and life-history characteristics between two geographic populations.Red Knobby Newts(Tylototriton shanjing)distributed in western mountain environment of Yunnan province is a typical specie of caudate amphibians,which belongs to Salamandridae Tylototriton.There were some reports about the morphology,the geographical distribution,the taxonomic status,the behavioral changes during reproduction,and the early embryonic development of the Red Knobby Newts.However,so far,their basic characteristics and variation of the two population of life-history were not completely understood.In this study,the two populations of the Red Knobby Newts from Cangshan Mountain(1610 m)and Ailao Mountain(1900 m)Yunnan,respectively,were chose as the research objects.We recorded the population number,the morphological characteristic data,the reproductive characteristic of female,collected the clipped phalange materials,and surveyed the body condition of Red Knobby Newts of Cangshan Mountain population in Yangbi County,Yunnan during the breeding season in May to June,2018 and June to July,2019.Data collected earlier of the morphological and life-history characteristic,the phalangeal material,and the reproduction from Ailao Mountain population(Ailao Mountain,Xinping County,Yunnan)was analyzed and compared with that from the Cangshan Mountain populations(Cangshan Mountain and Ailao Mountain,Yunnan).In this paper,the differences in the morphological characteristics of the two geographic populations at different altitudes,such as the body size and the sexual dimorphism were analyzed.The differences of the life-history traits between two newts populations were compared and analyzed by the skeletochronology methods,such as the age of sexual maturity,the maximum life span,and the adult growth rate of individuals.According to the correlation analysis and the comparison of the clutch size and the body size,the variation of the reproductive characteristics of the two geographical populations was studied.The relationship of the body condition and the breeding time of Red Knobby Newts from Cangshan Mountain was analyzed.In this work,the variation and the evolution of the life-history characteristics of Red Knobby Newts from two geographic populations were completely analyzed by comparing the morphology,the skeletochronology,and the reproductive ecology to explore the general pattern of life-history traits variation in amphibians.The results of this research as follows:1.There were the sexual size dimorphism phenomena of Red Knobby Newts in the two geographic populations.The morphological characteristics of female,such as the body mass,the snout-vent length,and the length from axilla to groin were larger than that of male,which were consistent with the fertility selection hypothesis.The morphological characteristics,such as snout-vent length and body mass,abided by Bergman's rules.The morphology geographical variation of Red Knobby Newts may be the reason of the external temperature and the food.2.The skeletochronology was successfully applied to identify the age structure of the Red Knobby Newts(249 individuals from two populations).The maximum life expectancy of the female and male Red Knobby Newts from Cangshan Mountain were 11 and 9 years old,respectively,and the sexual maturity ages of female and male were 4 and 3 years old,respectively.However,the maximum life expectancy of female and male Red Knobby Newts from Ailao Mountain were 11 and 7 years old,respectively,and the sexual maturity ages of female and male were 5 and 3-4 years old,respectively.There was a significant difference in the two sexes between these two populations.At the same time,the female sexual maturity age was older than that of male.There was no significant difference in the average age of the two populations.3.The ages of the male and the female from the two geographic populations were increased with the increasing of the body mass and the snout-vent length,which had a significant correlation with the length from axilla to groin of female individuals.At the same age,the growth rate of the sexual maturity early stages from the high-altitude areas was higher than that from the low-altitude.4.The data of female reproductive from the two Red Knobby Newts populations was analyzed,which suggested that the clutch size,the clutch weight,and the relative weight of clutch had a significantly positive correlation with the size of female individuals.In another words,the large female individuals have the strong reproductive ability.The clutch size,the clutch weight,and the relative weight of clutch had a significant difference in the two populations.The individuals from the high altitudes respond to the pressure of the external environment by increasing the clutch size and the clutch weight.High-altitude populations respond to the pressure of the external environment by increasing breeding investment,such as clutch weight and relative clutch weight,in order to increase the survival rate.5.The female individuals from the Cangshan in the early stages of reproduction were larger in the body mass,the snout-vent length,and the body condition than those in the later stages of reproduction.There was a significant difference in different breeding periods.The male individuals had a significant difference in snout-vent length and body mass.The percentages of the small individuals were increased in the later stages of reproduction,which may be the result of different reproduction strategies for male and female individuals with different physical conditions.The results of the morphological characteristics and life-history variation of Red Knobby Newts from two geographical populations indicate that the body size from high-altitude populations have larger body size,faster growth rate before the sexual maturity,and greater investment in reproduction than that from the low-altitude,while there are no significant difference in the populations age structure and sexual maturity age.The breeding time of the large body size individuals is earlier than that of smaller ones.These differences in the morphology and the life-history characteristics are the results of the adaptations of species to different environmental conditions.As a representative of near-endangered species of tailed amphibians,the study of Red Knobby Newts variation of life-history traits from two geographic populations have an important scientific significance for the protection of these species and other caudate amphibians.