Geographic variation in life-history traits among populations of wide-ranging species is influenced by both spatial and temporal aspects of the environment. Rarely, however, are the effects of both aspects exami...Geographic variation in life-history traits among populations of wide-ranging species is influenced by both spatial and temporal aspects of the environment. Rarely, however, are the effects of both aspects examined concurrently. We collected gravid female lizards (Sceloporus undulatus) from northern (Indiana), central (Mississippi) and southern (Florida) populations, spanning nearly the full latitudinal range of the species, to examine among-population differences in strategies of reproductive energy allocation. Adult females from the southern population were smaller, and produced fewer and smaller eggs in their first clutches than did females from the more northern populations. Southern females were more likely to produce a second clutch, and second clutches were smaller than first clutches for females from the 2 northern populations. Together these trends eliminated population differences in overall reproductive output after accounting for body size. The trend for greater reproductive energy to be allocated to first clutches at higher latitudes, and to later clutches at lower latitudes is corroborated by published data from field studies on multiple populations. Distributing reproductive effort by producing more clutches of smaller eggs may be an adaptive response to the long season available for egg incubation and lizard activity in sub-tropical southern environments. In contrast, allocating greater resources to early reproduction may enhance maternal fitness in the relatively short activity seasons that characterize more northern sites.展开更多
Vertebrate embryos require access to water;however,many species nest in terrestrial habitats that vary considerably in moisture content.Oviparous,non-avian reptiles have served as models to understand how environmenta...Vertebrate embryos require access to water;however,many species nest in terrestrial habitats that vary considerably in moisture content.Oviparous,non-avian reptiles have served as models to understand how environmental factors,like moisture availability,influence development because eggs are often exposed to prevailing environments in the absence of parental care.Though much research demonstrates the importance of water absorption by eggs,many ecological factors that influence moisture availability in natural nests have received little attention.For example,the type of substrate in which nests are constructed is understudied.We experimentally incubated eggs of the brown anole lizard(Anolis sagrei)in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations.One substrate consisted of sand and crushed seashells and the other was mostly organic material(i.e.decayed plant material).Both are common nesting substrates at our field site.When controlling for water uptake by eggs,we found that egg survival and hatchling phenotypes were similar between substrates;however,embryos developed more quickly in the sand/shell substrate than the organic substrate,indicating substrate-specific effects on embryo physiology.These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable;however,some aspects of development,like developmental rate,are affected by the type of substrate,independent of water availability.Further study is required to determine how natural substrates influence embryo physiology independent of water content.展开更多
Increases in extreme environmental events are predicted to be major results of ongoing global climate change and may impact the persistence of species.We examined the effects of heat and cold waves during embryonic de...Increases in extreme environmental events are predicted to be major results of ongoing global climate change and may impact the persistence of species.We examined the effects of heat and cold waves during embryonic development of painted turtles(Chrysemys picta)in natural nests on the occurrence of abnormal shell morphologies in hatchlings.We found that nests exposed to extreme hot temperatures for>60 h produced more hatchlings with abnormalities than nests exposed to extreme hot temperatures for shorter periods,regardless of whether or not nesting females displayed abnormal morphologies.We observed no effect of extreme cold nest temperatures on the occurrence of hatchlings with abnormalities.Moreover,the frequency of nesting females with abnormal shell morphologies was approximately 2-fold lower than that of their offspring,suggesting that such abnormalities are negatively correlated with survival and fitness.Female turtles could potentially buffer their offspring from extreme heat by altering aspects of nesting behavior,such as choosing shadier nesting sites.We addressed this hypothesis by examining the effects of shade cover on extreme nest temperatures and the occurrence of hatchling abnormalities.While shade cover was negatively correlated with the occurrence of extreme hot nest temperatures,it was not significantly correlated with abnormalities.Therefore,female choice of shade cover does not appear to be a viable target for selection to reduce hatchling abnormalities.Our results suggest that increases in the frequency and intensity of heat waves associated with climate change might perturb developmental programs and thereby reduce the fitness of entire cohorts of turtles.展开更多
基金This work was supported by grants from the Natural Science Foundation of China,‘One Hundred Talents Program’of the Chinese Academy of Sciences and the University of Sydney(to W.Du)the Australian Research Council(to R.Shine)+1 种基金the US National Science Foundation(DEB0949483 to T.Langkilde)D.Warner was supported by a grant from the US National Science Foundation(DEB0640932 to F.Janzen)during this research and T.R.Robbins by Sigma Xi Grants-in-Aid of Research.
文摘Geographic variation in life-history traits among populations of wide-ranging species is influenced by both spatial and temporal aspects of the environment. Rarely, however, are the effects of both aspects examined concurrently. We collected gravid female lizards (Sceloporus undulatus) from northern (Indiana), central (Mississippi) and southern (Florida) populations, spanning nearly the full latitudinal range of the species, to examine among-population differences in strategies of reproductive energy allocation. Adult females from the southern population were smaller, and produced fewer and smaller eggs in their first clutches than did females from the more northern populations. Southern females were more likely to produce a second clutch, and second clutches were smaller than first clutches for females from the 2 northern populations. Together these trends eliminated population differences in overall reproductive output after accounting for body size. The trend for greater reproductive energy to be allocated to first clutches at higher latitudes, and to later clutches at lower latitudes is corroborated by published data from field studies on multiple populations. Distributing reproductive effort by producing more clutches of smaller eggs may be an adaptive response to the long season available for egg incubation and lizard activity in sub-tropical southern environments. In contrast, allocating greater resources to early reproduction may enhance maternal fitness in the relatively short activity seasons that characterize more northern sites.
基金The research was approved by Auburn University IACUC(protocol 2019-3465)This study was supported by funds from Auburn University.J.M.H.was supported by the National Science Foundation(NSF DEB-1942145 to DAW)during the preparation of this manuscript.
文摘Vertebrate embryos require access to water;however,many species nest in terrestrial habitats that vary considerably in moisture content.Oviparous,non-avian reptiles have served as models to understand how environmental factors,like moisture availability,influence development because eggs are often exposed to prevailing environments in the absence of parental care.Though much research demonstrates the importance of water absorption by eggs,many ecological factors that influence moisture availability in natural nests have received little attention.For example,the type of substrate in which nests are constructed is understudied.We experimentally incubated eggs of the brown anole lizard(Anolis sagrei)in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations.One substrate consisted of sand and crushed seashells and the other was mostly organic material(i.e.decayed plant material).Both are common nesting substrates at our field site.When controlling for water uptake by eggs,we found that egg survival and hatchling phenotypes were similar between substrates;however,embryos developed more quickly in the sand/shell substrate than the organic substrate,indicating substrate-specific effects on embryo physiology.These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable;however,some aspects of development,like developmental rate,are affected by the type of substrate,independent of water availability.Further study is required to determine how natural substrates influence embryo physiology independent of water content.
基金supported by National Science Foundation grant LTREB DEB-0089680 to F.J.Janzensupported by a United States EPA STAR fellowship+1 种基金supported by NSF LTREB DEB-0640932 to F.J.Janzensupported by the Iowa State University Program for Women in Science and Engineering.
文摘Increases in extreme environmental events are predicted to be major results of ongoing global climate change and may impact the persistence of species.We examined the effects of heat and cold waves during embryonic development of painted turtles(Chrysemys picta)in natural nests on the occurrence of abnormal shell morphologies in hatchlings.We found that nests exposed to extreme hot temperatures for>60 h produced more hatchlings with abnormalities than nests exposed to extreme hot temperatures for shorter periods,regardless of whether or not nesting females displayed abnormal morphologies.We observed no effect of extreme cold nest temperatures on the occurrence of hatchlings with abnormalities.Moreover,the frequency of nesting females with abnormal shell morphologies was approximately 2-fold lower than that of their offspring,suggesting that such abnormalities are negatively correlated with survival and fitness.Female turtles could potentially buffer their offspring from extreme heat by altering aspects of nesting behavior,such as choosing shadier nesting sites.We addressed this hypothesis by examining the effects of shade cover on extreme nest temperatures and the occurrence of hatchling abnormalities.While shade cover was negatively correlated with the occurrence of extreme hot nest temperatures,it was not significantly correlated with abnormalities.Therefore,female choice of shade cover does not appear to be a viable target for selection to reduce hatchling abnormalities.Our results suggest that increases in the frequency and intensity of heat waves associated with climate change might perturb developmental programs and thereby reduce the fitness of entire cohorts of turtles.
