Can neutral genetic differentiation explain geographical variation in body size of the natterjack toad, Epidalea calamita?

MARANGONI, F.

ACTA HERPETOLOGICA

FIRENZE UNIV PRESS

Año: 2023 vol. 18 p. 69 - 78

1827-9635

Population genetic studies are crucial for evolutionary biologists because the 2 population is the basic substrate on which evolution is forged. However little empirical 3 evidence has been able to demonstrate the role that isolation and gene flow play in 4 maintaining differentiation in populations at short geographic scales. Epidalea calamita 5 exhibits a steep variation in body size and reproductive traits in southwestern Spain, 6 associated with changes in the geological substrate. This implies a decrease of 70.9% of body 7 mass and 28.5% in snout-vent length, on a micro-geographic scale of only 110 km. Previous 8 results from both metamorphic and juvenile common garden experiments showed that genetic 9 differentiation may be a causal determinant of geographic variation in adult. In this study 10 I tested if whether neutral genetic differentiation can explain the geographical variation in the 11 body size observed in E. calamita. It was addressed this analyzing the level of genetic 12 structuring and gene flow among populations along the cline, comparing the genetic diversity 13 between and within populations, as well as between ecological environments. The study 14 showed that the geographic variation in body size observed in E. calamita has evolved in 15 absence of geographic isolation, with moderate gene flow connecting the populations. Thus, 16 neutral genetic differentiation cannot explain the geographical variation observed. Future 17 studies are needed on the interaction between the genetic component with the environmental 18 factors and will be necessary to analyze the contribution of the maternal effects in the origin 19 and evolution of the geographical variation in the body size observed in E. calamita from 20 southern Spain.