| Mate choice can affect reproductive success.Both males and females choose high-quality individuals as their mates.For example,males choose larger females as mates,and females prefer distant related males with larger body sizes.Offspring grow faster or be larger body sizes,if they have larger parents or higher parental reproductive investments.Inbreeding or outbreeding cause inbreeding depression or outbreeding depression,which have a negative impact on the growth and development of offspring.Therefore,the relative studies of parental sizes,parental investment,and parental coefficient relatedness on the offspring growth and development can provide the basis for studying sexual selection and reproduction strategies for animals.The Asiatic toad(Bufo gargarizans)is an explosive breeder widely distributed and with a large population.Breeding seasons and the time period of growth until metamorphosis of their offspring are relatively short.So,it is an excellent model species to study the relationship between parents and offspring.Previous researches about B.gargarizans were mainly focused on its medicinal values.However,there were fewer studies about its reproduction ecology,especially the effects of parental reproduction on the growth and development of the offspring from fertilized eggs to metamorphosis at all relatively important stages.During February to March of 2016 and February to March of 2019,we measured snout to vent length(SVL)and mass and collected samples of B.gargarizans at a breeding site in Badagongshan National Nature Reserve.Sangzhi,Hunan Province.Then,we measured the body sizes of tadpoles and acquired the coefficient of relatedness for parents by microsatellite molecular marker to explore the relationship between the parents and the offspring.A total of 6 indicators of parents were collected,which were parental relatedness,paternal investment,dam SVL,dam mass,sire SVL and sire mass.We took sire SVL × dam and sire mass × dam as the analysis indicators,owing to the mutual influence of sire and dam.In accordance with developmental duration,growth rate and body sizes of the offspring at G25,G42 and G46,we collected 16 indicators:G0-G25 developmental duration,G0-G42 developmental duration,G0-G46 developmental duration,G25-G42 developmental duration,G42-G46 developmental duration,G0-G25 growth rate,G25-G42 growth rate,G0-G42 growth rate,G42-G46 growth rate,G25 total length,G25 body width,G42 total length,G42 body width,G46 SVL,G46 body width,G46 tibiofibula length.We constructed generalized linear models between the indicators of parents and the indicators of the offspring growth and development in 2016 and 2019.On the basis of Akaike information criteria(AIC)and information theory to screen out the optimal model sets of parents and offspring,which could analyze the value of parental factors impact on the offspring fitness.The results of our studies are as follows:(1)Parental body sizes were important factors affecting the offspring growth and development.That is,weights and SVLs of parents,which were dam SVL,sire SVL,and sire SVL × dam SVL in this study,were important factors.Linear regression showed a significantly positive correlation between sire mass and G42 body width of the offspring(R2=0.201,P<0.05);a significantly positive correlation was showed between sire mass× dam mass and G46 body width of the tadpoles(R2=0.166,P<0.05).These meant that larger parents might lead to larger offspring with higher offspring fitness.(2)Linear regression in 2016 showed a significantly negative correlation between the parental reproductive investment and G25-G42 growth rate of the tadpoles(R2=0.551,P<0.05).Linear regression in 2019 did not show any significant relationship between parental reproductive investment and G46 body width of the tadpoles(R2=0.139,P=0.210);G46 tibiofibula length of the tadpoles(R2=0.221,P=0.105).The trends for these regressions was positive.These meant that higher the parental reproduction investment might lead to slower offspring growth rate with larger offspring.Tadpoles might increase body sizes by extending the developmental duration.Larger tadpoles with longer tibiofibula can enhance their jumping ability,thereby increasing offspring fitness.(3)Linear regression did not show any significant relationship between the estimated inbreeding coefficient and the growth and development of the tadpoles.The trends for these regressions in 2016 and 2019 was negative between the estimated inbreeding coefficient and G42-G46 developmental duration of the tadpoles(R2=0.080,P=0.181),G46 body width of the tadpoles(R2=0.137,P=0.075);the trends for the regressions was positive between the estimated inbreeding coefficient and G42-G46 growth rate of the tadpoles(R2=0.044,P=0.324).The trends for the regressions in 2016 was negative between the estimated inbreeding coefficient and G0-G46 developmental duration of the tadpoles(R2=0.434,P=0.341),G46 body width of the tadpoles(R2=0.868,P=0.068);the trends for the regressions was positive between the estimated inbreeding coefficient and G42-G46 growth rate of the tadpoles(R2=0.232,P=0.518).The trends for these regressions in 2019 was negative between the estimated inbreeding coefficient and G42-G46 developmental duration of the tadpoles(R2=0.012,P=0.644),G46 body width of the tadpoles(R2=0.065,P=0.276),G25-G42 growth rate of the tadpoles(R2=0.140,P=0.104).These meant that closer parental relatedness might lead to smaller offspring with longer the developmental duration.Inbreeding might lead to lower survival rate of the tadpoles with lower offspring fitness.In conclusion,we have the following results based on our study:when the parents were large(SVL and mass),its offspring fitness was also high;when the father invested more in reproduction,the offspring fitness was also high;inbreeding led up to low offspring fitness.This study provides a basis for revealing amphibian mate choice,breeding strategy and parental impact on offspring fitness. |
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