Effects Of Climate Warming And Physiological Factors On Lizards With Different Reproductive Patterns

Climate warming affects organisms in all biomes and ecosystems,particularly for ectotherms.Live-bearing(viviparity)is a reproductive mode that evolves from egg-laying(oviparity)through gradual increases in the length of egg retention and intrauterine development.Physiological changes accompanied by the evolution of viviparity is hypothesized to be the reason for why viviparous species are more vulnerable to climate warming.However,physiological,behavioral and/or genetic adjustments can enhance their ability to tolerate climate warming.Here,we used four oviparous species(Phrynocephalus przewalskii,Eremias argus,Sphenomorphus incognitus and Plestiodon chinensis)and three viviparous species(Phrynocephalus guinanensis,Eremias multiocellata and Sphenomorphus indicus)of lizards to test how climate warming differentially affects various aspects(behavior,thermal preference,female reproduction,offspring phenotype,post-hatching growth and survival and other physiological traits)of lizards with different parity modes.The effects of climate warming on terrestrial organisms are population-dependent,which are in parallel with their physiological tolerance and the rate of warming.Some studies show that climate warming affects high-latitude ectotherms more evidently than those from low latitudes,whereas others show opposite results.Here,we design 3(populations: Wulate ?1025 m,Zhangye ?1782 m,and Jiuquan ?2887 m)× 2(temperature treatments: 20 ? and 28 ?)factorial design experiment to test the combined effects of population source and temperature.Our data show that activity and birth date decreased and thermal preference increased as ambient temperature increase in three populations,and that female reproductive output was positive with temperature in low latitudes population and had a difference,but this result did not exist in other populations.Gravid females thermoregulated more actively but selected lower body temperatures than did nongravid females and adult male.Climate warming reduced the time allotted for thermoregulation in all three populations,and constrained activity more dramatically in high-altitude populations.However,thermal preference decreased as altitude increased.Thus,our data support the idea that lizards from high-altitude populations are more vulnerable to climate warming,while the opposite result was found on the thermal preference.Nest-site choice can affect offspring phenotypes and fitness,and this especially true for oviparity species.Numerous studies have proved that temperature and water are important factors affecting egg incubation and offspring phenotype and fitness,but to date the studies focusing on the combined effects of both factors are rare.Moreover,we know little about whether the timing of female reproduction affects nest-site choice.Here,we addressed those topics by randomly assigning gravid P.przewalskii among three treatments(20,24 and 28 ?)and then determining whether they would adjust strategies of nest-site choice.We fed the hatchings until they laid eggs,and then recorded clutch shifts in nest-site choice.We found that lizards tended to lay eggs in relatively cold and wet nests on the opposite side of the heating source at relatively high ambient temperatures,and relatively warm and dry nests close to the heating source at relatively low ambient temperatures.Hatching success in the nests on the opposite side of the heating source was 48.8 %,which was significantly higher than that(11.7 %)in the nests close to the heating source.We found that lizards were more likely to lay eggs in the nests where hatching success was high as they laid later clutches.Our data showed that temperature had a more important role than moisture in affecting nest-site choice in P.przewalskii,and that previous experience with laying eggs in right nests if of importance in enhancing hatching success in the lizard.We maintained gravid Chinese skinks(Plestiodon chinensis)at three constant temperatures(25,28 and 31 °C)and incubated eggs laid at these temperatures to determine maternal thermal effects on female reproduction and hatchling phenotype.Within the range of 25-31 °C,maternal temperature affected egg-laying date,hatching success and hatchling linear size(snout-vent length,SVL)but not clutch size,egg size,egg component,and embryonic stage at laying.More specifically,females at higher temperatures laid eggs earlier than did those at low temperatures,eggs laid at 31 °C were less likely to hatch than those laid at 25 °C or 28 °C,and hatchlings from eggs laid at 31 °C were smaller in SVL.Our finding that maternal temperature(pre-ovipositional thermal condition)rather than incubation temperature(post-ovipositional thermal condition)affected hatching success indicated that embryos at early stages were more vulnerable to temperature than those at late stages.Our data provide an inference that moderate maternal temperatures enhance reproductive fitness in P.chinensis.Ectotherms are considered to be especially vulnerable to climate warming,because the environment experienced by parents or offspring can impact the female reproduction,the phenotype of offspring,growth and survival.Here,we manipulated parental temperature(20,24 and 28 °C)in the Mongolian racerunners(Eremias argus),an oviparous lacertid lizard.Eggs were incubated in four thermal regimes(25±5,25±3,25 and 28 °C),and hatchlings were reared in either grouped or isolated conditions.Our results showed that survival rate,incubation length and hatching success was negatively related to incubation temperature.Survival rate of adult females was highest in the 24oC treatment(25%)and lowest in the 28 oC treatment(0%),with the 20 oC treatment(10.5 %)in between.The Kaplan-Meier survival analysis showed that parental temperature rather than incubation temperature affected hatching survival.Social environment did not affect hatchings growth and survival rate.From this experiment we conclude that climate warming affect population persistence and that the effect shifts ontogenetically.In order to test how climate warming affect viviparous species,we maintained Eremis multiocellata at three temperatures(20,24 and 28 ?)to determine the effects of maternal temperature and breeding temperatures on birth date,female reproductive traits and offspring phenotype.Our data showed that: 1)parental temperature affected adult survival,birth date,and offspring size(snout-vent length,SVL)but not reproductive output and other offspring morphological traits;2)offspring survival rate decreased as parental temperature increased;3)temperature affected offspring growth but not offspring survival rate.These results provide an inference that climate warming affects population persistence and that extreme weather may have a more seriously effect.The reproductive maturation hypothesis,the terminal investment hypothesis and the senescence hypothesis are the most extensively evaluated hypotheses proposed to explain age-related patterns of reproduction in iteroparous organisms.We evaluated these hypotheses for the Mongolian racerunner(Eremias argus,oviparous)and the multi-ocellated racerunner(Eremias multiocellata,viviparous)by comparing multiple reproductive traits between females that completed reproductive cycles under the same laboratory conditions in two consecutive years.In E.multiocellata,we also compared their offspring growth and survival rate,in the 90 days.In this two species,we found that reproductive females gained linear size(snout-vent length,SVL)as they got one year older and during the breeding season.At same time,larger females generally laid eggs earlier and invested more in reproduction than did smaller ones.In E.argus,females switched from laying smaller eggs in the first clutch to larger eggs in the subsequent clutches,but kept clutch size and postpartum body mass constant between successive clutches in a breeding season and between years.Of the traits examined,only clutch frequency,annual fecundity and annual reproductive output were susceptible to ageing.More specifically,clutch frequency,annual fecundity and annual reproductive reduce with 1.1 clutches,3.1 eggs and 1.0 g,respectively,in 2009 compared to 2008.However,in E.multiocellata,our results show that little size increase by 0.3 neonates,little mass reduce with 0.1 g;neonate mass reduce with 0.1 g.Our results provide clear evidence that the reproductive maturation hypothesis better explains patterns of reproduction in young or prime-aged females of E.argus and E.multiocellata,while the senescence hypothesis better explains reproductive patterns in old females.The terminal investment hypothesis does not apply to any trait examined because no trait value was maximized in old females.Except that,we found reproductive senescence were different between reproduction models.Evaporative water loss can restrict expansion/evolution of species or populations.For pregnant females from arid regions,water is especial important.Is the evolution of viviparity accompanied by a relative decrease in evaporative evaporative water loss,thus allowing viviparous species to adaptive high latitudes or high altitude arid climatic region? To answer this question,we examined the effect of morphological(snout-vent length and body mass),treatment temperature(20,24 and 28 ?),environmental factors(annual average air temperature and annual average air moisture)and reproductive mode(oviparity and viviparity)on evaporative water loss in two pairs of lizards,which included two Phrynocephalus and two Sphenomorphus species with different reproductive modes.We found that morphological,temperature,and environmental factors were positively with increased evaporative water loss in two pairs of lizards.Especially,we found water loss rate had a positively relationship with the evolution of reproduction mode,from oviparity to viviparity.Our data show that the evolution of viviparity is not accompanied by a relative decrease in water loss in lizards.Conversely,they increase evaporative water loss allow the evolution of viviparity.