Desertification Drives the Shift in Egg Size-Number Trade-Off in an Agamid Lizard

Desertification is a serious ecological problem leading to significant biodiversity loss,but how desertification drives shifts in life history and fitness of animals remains understudied.To clarify whether habitat desertification causes shifts in life history strategies,we compared ecological factors and reproductive traits of Phrynocephalus przewalskii from three different desertification habitats-fixed dune,semi-fixed dune and mobile dune of a semi-arid region of Inner Mongolia,at the eastern edge of Hobq Desert,China.Our results showed a significant shift in the egg size-number trade-off of P.przewalskii in response to desertification,with lizards from the mobile dune habitat producing smaller clutches of larger eggs than lizards from the fixed and semi-fixed dune habitats.This life history shift is likely adaptive and driven by abiotic factors(temperature and precipitation)rather than biotic factors(food availability and lizard population density).Our study demonstrates that habitat desertification drives the shift in egg size-number trade-off in a lizard and highlights the importance of exploring the life history responses of animals to habitat desertification as well as to other traditionally well-studied factors like temperature,especially in the context of future global clima te change.

The Influence of Oxygen on the Development of Nanorana parkeri Tadpoles

Ectothermic animals are tolerant of variable oxygen availability, whether low-oxygen levels constrain the fitness of ectotherms remains unclear. Nanorana parkeri, an anuran endemic to the southern Tibetan plateau, is an excellent model with which to answer this question. In this study, we raised tadpoles ofN. parkeri in oxygenated water （high-oxygen group） and deoxygenated unchlorinated tap water （low-oxygen group） and monitored their growth, mortality, and telomere length. The growth rate for body length and body weight was higher in the low-oxygen group than in the high-oxygen group. However, dissolved oxygen did not affect development time, mortality, and telomere length of the tadpoles. These results suggest that although the oxygen concentration influenced some phenotype traits of plateau tadpoles, but it didn＇t influence the telomere length and survival rate, potential explanations are the local adaptation and N. parkeri tadpoles＇ wide oxygen tolerance, and fluctuant toxic content that resulted in little oxidative stress on tadpoles. These results indicated that low oxygen was not a stress to N. parkeri tadpoles＇ fitness and survival. This study is helpful in understanding the adaptation mechanisms of Tibetan plateau amphibians.

Altitudinal variation in life-history features of a Qinghai-Tibetan Plateau lizard

Environmental changes along an altitudinal gradient can facilitate the differentiation of life-history features in ectothermic species,but little attention has been devoted to the reciprocal influence of altitude and alpine slope directionality on life-history variation.According to life-history theory,increased environmental stress causes a change in reproductive allocation from number to quality of offspring,as well as a stronger trade-off between size and number of offspring.To clarify the influence of environmental pressures on the life-history features of the Qinghai toad-headed lizard Phrynocephalus vlangalii along an altitudinal cline,we surveyed late pregnant females from 3 populations of low(2,600 m),middle(3,400 m),and high(3,600 m)elevations in the Dangjin Mountain of Gansu,China from July to October 2019,and compared their inter-population differences in maternal body size,reproductive characteristics,offspring growth,and locomotor performance.Because of lower temperatures,higher humidity,and lower light intensity caused by slope aspect and altitude,the middle-altitude region experienced stronger environmental stress than the high-and low-altitude regions.Our results showed that females were larger at middle-and high-altitude sites and smaller at the low-altitude site,following Bergmann’s rule.We also found that females from low-altitude population gave birth earlier than those from the middle and high altitudes.Our results showed a shift in the offspring size-number trade-off of P.vlangalii in response to colder and harsher environments,with lizards from the alpine steppe(i.e.the middle-and high-altitude habitats)producing fewer but larger offspring than those from the warm steppe(i.e.the low-altitude habitat).Low-altitude juveniles grew faster than high-altitude ones,but at the same rates as middle-altitude juveniles.This result demonstrates that the growth of P.vlangalii was associated with temperature and light intensity.Our findings contribute to enhancing our understanding of the altitudinal variation in life-history features of plateau ectotherms and their phenotypic plasticity or local adaptation.

Taxonomic status of Chinese blue sheep(Pseudois nayaur):new evidence of a distinct subspecies

The blue sheep is an endemic species to the Qinghai-Tibet Plateau and surrounding regions.It has been regarded as having 2 subspecies:Pseudois nayaur nayaur and P.n.szechuanensis.However,such a classification remains controversial.Herein,we analyze 10 microsatellite loci and part of the mitochondrial control region for clarification in such taxonomic debates.We use samples from 168 individuals from 6 geographic populations covering almost all the distribution areas of the species in China to carry out comparisons.Phylogenetic trees derived from both the microsatellite and mitochondrial markers combined with the discriminant analysis of principal components(DAPC)and the STRUCTURE analysis reveal that the individuals in the Helan Mountains are well grouped with a distinct evolutionary lineage and are significantly different from the other populations of P.n.szechuanensis according to Fst values,implying that this isolated population should be categorized as a valid subspecies;namely,Pseudois nayaur alashanicus.The isolation-by-distance(IBD)analysis shows a significant positive relationship between genetic and geographical distances among the populations.