Proximate causes of altitudinal differences in body size in an agamid lizard

Abstract

Body size is directly linked to key life history traits such as growth, fecundity, and survivorship. Identifying the causes of body size variation is a critical task in ecological and evolutionary research. Body size variation along altitudinal gradients has received considerable attention; however, the underlying mechanisms are poorly understood. Here, we compared the growth rate and age structure of toad‐headed lizards (Phrynocephalus vlangalii) from two populations found at different elevations in the Qinghai‐Tibetan Plateau. We used mark‐recapture and skeletochronological analysis to identify the potential proximate causes of altitudinal variation in body size. Lizards from the high‐elevation site had higher growth rates and attained slightly larger adult body sizes than lizards from the low‐elevation site. However, newborns produced by high‐elevation females were smaller than those by low‐elevation females. Von Bertalanffy growth estimates predicted high‐elevation individuals would reach sexual maturity at an earlier age and have a lower mean age than low‐elevation individuals. Relatively lower mean age for the high‐elevation population was confirmed using the skeletochronological analysis. These results support the prediction that a larger adult body size of high‐elevation P. vlangalii results from higher growth rates, associated with higher resource availability.

Environmental causes of between-population difference in growth rate of a high-altitude lizard

“…Consistent with our prediction, potential prey availability was more abundant at the high-elevation site than at the low-elevation site, and high-elevation juveniles grew faster than low-elevation ones. Actually, higher growth rates for high-elevation P. vlangalii were also confirmed in another study using field mark-recapture data and von Bertalanffy growth parameters [ 39 ]. As suggested by some previous studies, the effect of food availability on lizard growth rate is more immediate [ 27 ].…”

“…The Qinghai toad-headed lizard ( Phrynocephalus vlangalii ), which is widely distributed in the Qinghai-Tibetan Plateau with an elevation range from 2000 to 4500 m, provides an excellent model to study altitudinal variation of growth rate in reptiles. Our previous study indicated that P. vlangalii individuals at a high-elevation site (Maduo, 4250 m elevation) can grow faster and reach a larger adult size than those at a low-elevation site (Maqu, 2930 m elevation) [ 39 ]. In this study, we conducted a mark-recapture experiment in the field and a common-garden experiment in the laboratory to determine genetic vs environmental components of this between-population difference in juvenile growth rate.…”

Comparison of thermoregulation and metabolic characteristics in Phrynocephalus vlangalii (Lacertilia, Agamidae) from different altitudes

“…As the changeable plateau climate and low environmental temperature allyear-round, it is difficult for reptile species from different populations to keep similar body temperature. Meanwhile, combined with a high food abundance at high altitude (Lu, Xu et al 2018), the P. vlangalii living at Maduo selected a relatively low body temperature may be more conducive to improving the efficiency of energy utilization and may conduce to allocate more energy on territories occupied, mating, avoiding predator and predation (Gvoždík 2002).…”

Age and growth of the common wall lizard, Podarcis muralis (Laurenti, 1768)

“…The parameters L ∞ (asymptotic SVL) and k, and their asymptotic confidence intervals (CI), were estimated by means of a non-linear regression procedure using the IBM SPSS 21.0 software program. Then, the growth rates were calculated as R = k(L ∞ − L t ) (Bülbül et al, 2016a;Lu et al, 2017). The growth curves were considered to be significantly different if the 95% confidence intervals of the growth coefficient k did not overlap (James, 1991;Wapstra et al, 2001).…”