Abstract
BackgroundTwo previous studies on interspecific body size variation of anurans found that the key drivers of variation are the species’ lifestyles and the environments that they live in. To examine whether those findings apply at the intraspecific level, we conducted a study of the Asian common toad (Duttaphrynus melanostictus), a terrestrial anuran distributed in tropical regions. The body size of toads from 15 locations, covering the majority of their geographic range, and local environmental data were summarized from published literature. We used a model selection process based on an information-theoretic approach to examine the relationship between toad body size and those environmental parameters.ResultsWe found a positive correlation between the body size of the Asian common toad and the water deficit gradient, but no linkage between body size and temperature-related parameters. Furthermore, there was a positive correlation between the seasonality of precipitation and body size of females from different sampled populations.ConclusionsAs a terrestrial anuran, the Asian common toad should experience greater pressure from environmental fluctuations than aquatic species. It is mainly distributed in tropical regions where temperatures are generally warm and stable, but water availability fluctuates. Therefore, while thermal gradients are not strong enough to generate selection pressure on body size, the moisture gradient is strong enough to select for larger size in both males and females in dryer regions. Larger body size supports more efficient water conservation, a pattern in accordance with the prediction that lifestyles of different species and their local habitats determine the relationship between body size and environment. In addition, larger females occur in regions with greater seasonality in precipitation, which may happen because larger females can afford greater reproductive output in a limited reproductive season.
Highlights
Two previous studies on interspecific body size variation of anurans found that the key drivers of variation are the species’ lifestyles and the environments that they live in
The annual mean temperature experienced by each population ranged from 15.8 °C to 28.1 °C; the water deficit level ranged from 0.46 mm to 66.28 mm; and the precipitation seasonality ranged from 49 to 104 (Fig. 1a-c; Additional file 1: Table S2)
Correlation between body size and environmental gradients When sex differences were considered, of the 32 models constructed, results showed that the mean body size of male Asian common toad was unaffected by environmental temperature gradients but was influenced by environmental dryness level (Table 1; Fig. 2a and b)
Summary
Two previous studies on interspecific body size variation of anurans found that the key drivers of variation are the species’ lifestyles and the environments that they live in To examine whether those findings apply at the intraspecific level, we conducted a study of the Asian common toad (Duttaphrynus melanostictus), a terrestrial anuran distributed in tropical regions. Anurans from the Brazilian Cerrado in South America showed a positive correlation between body size and water deficit, a measurement of environmental dryness [30] Those findings indicate that body size in anurans is strongly affected by environmental background: in regions where temperature fluctuates more, but precipitation fluctuates less (e.g., Holarctic), the major forces are thermal conditions, but in regions where temperature fluctuates less than precipitation (e.g., Neotropics), precipitation becomes the limiting factor [30]. We hypothesized that toads would be larger in regions where the environmental water deficit is high, but that there would be no relationship between body size and thermal gradients [30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
