The Trade-offs In Reproductive Investment Of The Female Toad-headed Lizard Phrynocephalus Vlangalii At Different Altitudes

Phrynocephalus vlangalii is a species with the largest vertical distribution span on the Tibetan Plateau among reptiles.Therefore,the female P.vlangalii is an ideal experimental material to study the trade-offs in reproductive investment at different altitudes.There are few reports that combine the physiological and reproductive characteristics of a lizard.In this study,we choose the pregnant female P.vlangalii of Maduo population(4257 meters)and Delingha population(2910 meters)as experimental materials at high altitudes and low altitudes,respectively.We analyzed the physiological characteristics of pregnant female P.vlangalii,such as resting metabolic rate,sport performance,and selected body temperature,with its reproductive parameters,so as to explore the trade-offs in reproductive investment.The results showed that,compared with the postpartum period,at the end of the pregnancy,the two populations had higher resting metabolism rate,lower sprint speed and lower selected body temperature.Compared with the lower altitude population,the higher altitude population had higher selected body temperature in the prenatal and postnatal period,but there was no significant difference in sprint speed.It indicated that pregnancy and inhabitant altitude are the important factors that affect the resting metabolic rate and selected body temperature of female P.vlangalii,but both factors had little influence on the ability of sport.The correlation analysis of reproductive parameters and physiological characteristics showed that:(1)The reproduction was the direct factor affecting the level of metabolic rate;(2)The energy investment in the sport ability was relatively constant during the reproductive process,which was the basic requirement for the stability of the body to maintain the state;(3)The reason why pregnant females in higher altitude chose higher body temperature may be that their relative reproductive investment was smaller,or it was the important limiting factor of their relative reproductive investment.Furthermore,we also had examined the reproductive characteristics(including the delivery date,snout-vent length(SVL),postpartum body mass,litter mass,litter size,mean hatchling mass,and relative litter mass(RLM))of the female P.vlangalii and morphological characteristics of the offspring(including body mass,SVL,tail length,head length,head width,fore-limb length,and hind-limb length).The results showed that the pregnant female lizards gave birth from July 20 th to August 19 th,and the lower altitude population was earlier and more dispersed than that of the higher altitude population.There were significant differences between altitudes in other reproductive characteristics except mean hatchling mass of the female P.vlangalii.In addition to the SVL and fore-limb length,the other morphological characteristics of the offspring were significantly different between the two populations,and all the other characteristics of the lower altitude were greater than that of the higher.The postpartum mass,litter size and litter mass of both populations were significantly positively correlated with the SVL of female P.vlangalii.Partial correlation analysis showed that the litter sizes of two populations were negatively correlated with the mean hatchling mass,and the postpartum state was negatively correlated with the litter size.There was a significant positive correlation between litter mass and relative fecundity of two populations,however,the mean hatchling mass was not related to the relative fecundity in the both populations.Relative litter mass and relative fecundity of the Delingha population was significantly positively correlated,but not significantly correlated in Maduo populations.