TAIL SHEDDING IN ISLAND LIZARDS [LACERTIDAE, REPTILIA]: DECLINE OF ANTIPREDATOR DEFENSES IN RELAXED PREDATION ENVIRONMENTS

The ability of an animal to shed its tail is a widespread antipredator strategy among lizards. The degree of expression of this defense is expected to be shaped by prevailing environmental conditions including local predation pressure. We test these hypotheses by comparing several aspects of caudal autotomy in 15 Mediterranean lizard taxa existing across a swath of mainland and island localities that differ in the number and identity of predator species present. Autotomic ease varied substantially among the study populations, in a pattern that is best explained by the presence of vipers. Neither insularity nor the presence of other types of predators explain the observed autotomy rates. Final concentration of accumulated tail muscle lactate and duration of movement of a shed tail, two traits that were previously thought to relate to predation pressure, are in general not shaped by either predator diversity or insularity. Under conditions of relaxed predation selection, an uncoupling of different aspects of caudal autotomy exists, with some elements (ease of autotomy) declining faster than others (duration of movement, lactate concentration). We compared rates of shed tails in the field against rates of laboratory autotomies conducted under standardized conditions and found very high correlation values ( r > 0.96). This suggests that field autotomy rates, rather than being a metric of predatory attacks, merely reflect the innate predisposition of a taxon to shed its tail.     

Massive transoceanic gene flow in a freshwater turtle (Testudines: Geoemydidae: Mauremys rivulata)

The freshwater turtle Mauremys rivulata ranges from the Adriatic coast of the Balkan Peninsula through the Aegean region and coastal western and southern Turkey southwards to Israel. In addition, it occurs on several Aegean islands, Crete and Cyprus. Previous investigations using mtDNA sequences found virtually no genetic differentiation across its distribution range, despite some major biogeographical barriers for terrestrial and freshwater biota. Thus, the absence of any phylogeographical differentiation would be unexpected. To re‐examine genetic differentiation within M. rivulata, here we use a comprehensive rangewide sampling and information of 13 unlinked polymorphic microsatellite loci and compare these data against mtDNA variation. Our microsatellite analyses reveal a weak population structuring which conflicts, however, with most biogeographical barriers. We conclude that the genetic structure in the vast majority of the species' range has been shaped by massive transoceanic gene flow. This explanation is unlikely for the northernmost populations, which seem rather to be genetically impacted by intentionally released foreign turtles.