Genetic Diversity and Fitness in Peripheral and Central Populations of the European Tree Frog Hyla Arborea

Abstract

Genetic diversity is expected to decrease in small and isolated populations as a consequence of founder effects, bottlenecks, inbreeding and genetic drift. In this study we analyse temporal and spatial effects on genetic variation and progeny viability of the European tree frog (Hyla arborea) at two scales. First, the Swedish distribution has been isolated from the continental distribution for more than 8000 thousand years, and secondly, within Sweden, recent habitat alterations that have taken place during this century have increased isolation between local populations. Genetic variation and progeny survival in relation to isolation was studied within the entire Swedish distribution of the tree frog. Allozyme electrophoresis analysis of froglets, sampled across the Swedish distribution, revealed a low overall genetic variation (1.06 alleles/locus) at the protein level in comparison with continental populations (1.54–1.68 alleles/locus). However, egg hatchability (97 %) and early larval survival (95 %) were not lower than in other parts of the tree frog distribution or in other anuran species. Within the Swedish distribution, early larval survival was lower in isolated breeding ponds than in more central ones. However, no differences in genetic variation were found in relation to isolation. Polymorphism was detected only at a single locus, and was restricted geographically to the eastern part of the Swedish distribution. Bottlenecks due to climatic changes and fragmentation of suitable habitat (primarily natural pastures with ponds) are suggested as possible causes of the low genetic diversity of the Swedish tree frog population.

Small edge populations at risk: genetic diversity of the green lizard (Lacerta viridis viridis) in Germany and implications for conservation management

“…This illustrates that the Brandenburg L. v. viridis populations show the typical genetic pattern of a northern edge population within a species range (e.g. Lammi et al 1999;Edenhamn et al 2000;Hewitt 2001). The cause for the reduced genetic diversity of these edge populations may be simply explained by their small census size, or by more complex processes such as isolation or genetic drift, further investigations will clarify the possible mechanisms reducing the genetic diversity of the L. v. viridis edge populations.…”

The scale of genetic differentiation in the Dunes Sagebrush-Lizard (Sceloporus arenicolus), an endemic habitat specialist

“…Populations on the periphery of a species' range usually have lower effective population sizes because habitat quality is often marginal away from the center of the range (Edenhamn et al 2000;Vucetich and Waite 2003). Similarly, bottlenecks and founder events can reduce genetic diversity within populations and contribute to higher than expected levels of interpopulation differentiation (Wade and McCauley 1988).…”

Conservation phylogeography: does historical diversity contribute to regional vulnerability in European tree frogs (Hyla arborea)?

“…Thus, the low levels of genetic diversity in Western and Northern Europe, also reported from previous regional studies (Edenhamn et al . ; Andersen et al . ; Arens et al .…”

“…In line, several population genetics surveys independently documented low levels of variability in Western Europe, where H. arborea is the most vulnerable (Edenhamn et al . ; Andersen et al . ; Arens et al .…”