Over-ocean dispersal inferred from the saltwater tolerance of lizards from Taiwan

Abstract

BackgroundFor non-marine organisms, crossing the sea requires the challenges of dehydration and hypersalinity to be faced. Thus, the rate of water loss and saltwater tolerance determine the ability of species to disperse over sea and further influence species distribution. However, this association between physiology and ecology has rarely been investigated in terrestrial vertebrates. In this study, we examined the lizard species differently distributed across Taiwan and the adjacent islands to determine whether these physiological responses reflect the geographical distribution. We performed immersion experiments on individuals and eggs to test the rate of water loss and the saltwater tolerance in the six chosen species, that is, four native species (Plestiodon elegans, Eutropis longicaudata, Diploderma swinhonis, and Hemidactylus frenatus) and two introduced species (E. multifasciata and Anolis sagrei). Results For the individuals, the results showed that P. elegans had the highest rate of water loss and the lowest saltwater tolerance, whereas E. longicaudata and E. multifasciata showed the lowest rate of water loss and the highest saltwater tolerance. D. swinhonis, H. frenatus, and A. sagrei had medium measurements compared with the aforementioned species. On the other hand, for the eggs, only the rigid-shelled eggs of H. frenatus were not influenced by the water immersion and were incubated successfully after experimental treatment. In contrast, the parchment-shelled eggs of E. longicaudata and D. swinhonis lost or gained water dramatically in the experiments, and none of them hatched after immersion. ConclusionsThese interspecies differences in water loss and saltwater tolerance strongly suggest the heterogeneity of over-ocean dispersal ability among these lizards. Combined with the historical geology and the origin areas of each species, the inferences of the results largely explain the current distribution of these lizards across Taiwan and the adjacent islands. Furthermore, this study also helps to elucidate the potential dispersal of two invasive species, E. multifasciata and A. sagrei, for conservation purposes.