Life history consequences of nest-site variation in tropical pythons (Liasis fuscus)

We document and interpret microgeographic variation in life history traits of water pythons (Liasis fuscus) on the Adelaide River floodplain in tropic al Australia. Subpopulations of pythons separated by <2 km differ in reprod uctive timing, in survival rates at three different life history stages (ad ults, embryos, and hatchlings), in costs of reproduction, and in reproducti ve frequencies. Remarkably, these differences all seem to result from a min or divergence in nest-site characteristics, Female water pythons use two ma in types of nest sites: those with relatively low, variable temperatures (e specially hollows within paperbark root systems on the edge of the floodpla in) and those with higher, constant temperatures (burrows dug by large vara nid lizards in the higher, drier ridges similar to 2 km away). "Cool" nests delayed reproduction and reduced survival rates of hatchlings in at least one year. Females ovipositing in "cool" nests remained with the clutch thro ughout the 2-mo incubation period, whereas they deserted the clutch within a few days of laying in warmer nests. Most egg-attending females did not fe ed. Hence, "cool"-nesting females were emaciated by the end of incubation, and many died from starvation or predation; surviving females required two years to replenish their energy reserves before producing another clutch. I n contrast, "hot"-nesting females had higher rates of survival, and most co uld reproduce again the following year. Most females showed strong nest-sit e fidelity in successive clutches, but some moved between "hot" and "cool" nest sites. We have previously shown that the incubation thermal regime als o affects developmental rates and hatchling phenotypes (shape and behavior) . Thus, nest-site selection is a phenotypically plastic character, which al though superficially trivial, engenders significant microgeographic variati on in a wide range of life history traits.