Variation in body size and metamorphic traits of Iberian spadefoot toads over a short geographic distance

MARANGONI, F.; TEJEDO, M.

JOURNAL OF ZOOLOGY (1987)

The Zoological Society of London

Lugar: London, U.K. ; Año: 2008 vol. 275 p. 97 - 105

0952-8369

Determinants of geographic variation in body size are often poorly understood, especially in organisms with complex life cycles. We examined patterns of adult body size and metamorphic traits variation in Iberian spadefoot toad (Pelobates cultripes) populations, which exhibit an extreme reduction in adult body size of 71.6% reduction in body mass, in just about 30 km at southwestern Spain. We hypothesized that size at and time to metamorphosis would be predictive of the spatial pattern observed in adult body size. Larvae from eight populations were raised in a common garden experiment at two different larval densities that allow to differentiate whether population divergence was genetically based or it was simply a reflection of environmental variation and, in addition, if this population divergence was modulated by differing crowding larval environments. Larger adult size populations had higher larval growth rates attaining bigger sizes at metamorphosis, and exhibited higher survival than smaller-sized populations at both densities, although accentuated at low larval density. These population differences appeared consistent once embryo size variation was controlled for, suggesting that this phenotypic divergence is not due to maternal effects. Our results suggest considerable genetic differentiation in metamorphic traits that parallels and may be a causal determinant of geographic variation in adult body size. Keywords: amphibians, body size, geographic variation, metamorphosis