Environmental determinants of amphibian and reptile species richness in China

Abstract

Understanding the factors that regulate geographical variation in species richness has been one of the fundamental questions in ecology for decades, but our knowledge of the cause of geographical variation in species richness remains poor. This is particularly true for herpetofaunas (including amphibians and reptiles). Here, using correlation and regression analyses, we examine the relationship of herpetofaunal species richness in 245 localities across China with 30 environmental factors, which include nearly all major environmental factors that are considered to explain broad-scale species richness gradients in such theories as ambient energy, water Áenergy dynamics, productivity, habitat heterogeneity, and climatic stability. We found that the species richness of amphibians and reptiles is moderately to strongly correlated with most of the environmental variables examined, and that the best fit models, which include explanatory variables of temperature, precipitation, net primary productivity, minimum elevation, and range in elevation, explain ca 70% the variance in species richness for both amphibians and reptiles after accounting for sample area. Although water and temperature are important explanatory variables to both amphibians and reptiles, water variables explain more variance in amphibian species richness than in reptile species richness whereas temperature variables explain more variance in reptile species richness than in amphibian species richness, which is consistent with different physiological requirements of the two groups of organisms.

Climatic variables and altitude as predictors of anuran species richness and number of reproductive modes in Brazil

“…Among the explanatory variables studied herein (which explained 23.5% of the variance), the present study found that rainfall was the main variable related to species richness of anuran amphibians in Brazil, as it was in the previous studies performed in Australia (Williams & Hero 2001) and China (Qian et al 2007). The association of amphibians with humid areas is expected based on their physiological requirements (moist environments prevent desiccation of the animal, and allow cutaneous gas exchange) and also based on their reproductive requirements (anamniotic eggs that depend on water bodies or moist environments for an adequate development), which are unique characteristics of this animal group (Duellman & Trueb 1994).…”

“…Because locality area was not held constant among the selected localities, we first regressed species richness and number of reproductive modes, separately, on locality size area in order to statistically remove the effect of locality area before we conduct pRDA (Qian et al 2007). Then, we used the residual values as biotic variables for pRDA, because they contain the true information on species richness and reproductive modes.…”

“…rain-forest area and shape, and diversity of structural vegetation types), altitudinal diversity, and latitude are important for determining patterns of frog species richness in Australia (Williams & Hero 2001, Williams & Pearson 1997. Other variables considered important for amphibians are those concerning environmental productivity, such as net primary productivity explaining part of distribution of amphibian species richness in China (Qian et al 2007) and the amount of plant biomass as one of the main predictors of amphibian species richness in Europe (Rodríguez et al 2005). However, these variables are not considered the most important predictors of amphibian species richness in their respective localities, instead, rainfall has been pointed out as the main factor for determining species richness (Australia: Williams & Hero 2001;China: Qian et al 2007).…”

“…For example, bird species richness in South America is primarily affected by topography, latitude and precipitation (Rahbek & Graves 2001), and reptile species richness in China is most influenced by temperature (Qian et al 2007).…”

“…This dependence on climatic variables has shown that, in some areas, abiotic factors are more important for the structuring of frog assemblages than biotic factors are (Parris 2004, Werner et al 2007), but other studies have shown that spatial effects and stochasticity can also influence amphibian community composition (Ernst & Rödel 2005. Studies that verify the influence of the climatic variables on patterns of species richness distribution have been performed for amphibians in different regions of the world (Qian et al 2007, Rodríguez et al 2005, Williams & Hero 2001, and also for different animal groups in Brazil (Diniz-Filho et al 2008, Terribile & DinizFilho 2009, but this kind of study is still scarce for South American amphibians. The only study that verifies how spatial distribution of amphibian species richness responds to environmental variables was performed in the Brazilian cerrado biome, but results are inconclusive mainly because of the lack of a more extensive database on species occurrence at the analysed scale (Diniz-Filho et al 2008).…”