Shifts in thermal preference of introduced Asian house geckos (Hemidactylus frenatus) in temperate regions of southeastern Australia.

Despite its tropical origin, the Asian house gecko (Hemidactylus frenatus) is currently invading higher latitudes around the world. In this study, we investigated whether the introduced geckos in the subtropical/temperate region of southeastern Australia have shifted their thermal biology to cope with colder temperatures. In the lab, we measured the body temperatures of geckos from Thailand and Australia in a cost-free thermal gradient. Native H. frenatus from Thailand displayed a diel pattern of thermoregulation. Geckos maintained higher body temperatures during mid-afternoon and at dusk but selected cooler temperatures during the night. Introduced geckos showed a similar pattern of thermoregulation, but selected lower body temperatures in summer (mean = 28.9 °C) and winter (mean = 25.5 °C) than native geckos (mean = 31.5 °C). While the Asian house geckos from Thailand did not alter their body temperatures after feeding, their conspecifics from southeastern Australia selected body temperatures that were 1.6-3.1 °C higher after feeding. In conclusion, our study shows that invasive house geckos in Australia have shifted their preferred body temperatures downwards relative to their native conspecifics in Thailand, presumably as a result of plasticity or natural selection. Our findings suggest that these tropical geckos have adapted to colder regions, and thus, they may spread much further than expected for a tropical ectotherm

Plasticity in thermal hardening of the invasive Asian house gecko

The Asian house gecko (Hemidactylus frenatus) is a tropical invasive species that has established and spread throughout several temperate regions around the world. In some invasive species, rapid thermal acclimation (thermal hardening) may contribute to their success in occupying a wide range of climates. In this study, we investigated whether invasive house geckos from southeastern Australia show differing thermal hardening responses than individuals from the native range in Thailand. In the laboratory, we measured the basal heat tolerance (CTmax) of the geckos and their heat hardening response after being subjected to the second thermal stress after 1, 3, 5, 7, 9, or 11 h. When geckos had recovered, we measured their basal cold tolerance (CTmin) and cold hardening response over the same time intervals. We then explored whether hardening responses differed between populations or among time intervals. We found that basal heat tolerances did not differ between populations, but geckos from Australia had lower cold tolerance than geckos from Thailand. The magnitude of the heat hardening was similar between populations, but the introduced geckos had a higher magnitude of cold hardening. The native geckos could maximize their cold tolerance capacity for only 0.6 °C, versus 0.9 °C for the introduced geckos. Also, geckos from Australia exhibited faster responses to thermal stress than did geckos from Thailand. Maximum thermal tolerances as a result of hardening responses peaked within three hours after thermal stress in Australian geckos (adjusted means = 44.0 °C for CTmax and 9.9 °C for CTmin) and at five hours after thermal stress in Thailand geckos (adjusted means = 44.2 °C and 10.2 °C, respectively). The plasticity in the thermal hardening of the invasive gecko should enable it to survive rapid temperature fluctuations, especially winter cold snaps that occur in temperate regions

Shifts in thermal tolerance of the invasive Asian house gecko (Hemidactylus frenatus) across native and introduced ranges

The ability to rapidly adjust thermal tolerance in response to variable temperatures may facilitate the success of invasive species in non-native ranges. The Asian house gecko Hemidactylus frenatus is native to the tropics of South and Southeast Asia. This small lizard has spread across the globe and has also successfully invaded colder regions of Australia. In this study, we investigated whether this species displays plasticity in thermal tolerance in its introduced range. We measured cold tolerance (CTmin) and heat tolerance (CTmax) of H. frenatus from two native tropical populations in Thailand, and two introduced subtropical populations in southeastern Australia. We also explored seasonal variation in the thermal tolerance of the introduced populations. We found that heat tolerance (CTmax) of geckos did not differ among four populations in Thailand and Australia (range = 43.4–43.7 °C). By contrast, geckos from southeastern Australia had lower cold tolerance (CTmin) (mean = 10.43 °C) than geckos from Thailand (mean = 11.57 °C). We also documented seasonal shifts in cold tolerance of H. frenatus from southeastern Australia. Geckos captured in winter had cold tolerances 1–2 °C lower than those captured in summer. Unexpectedly, this shift in cold tolerance was accompanied by a 1–2 °C upward shift in heat tolerance. Our results support a growing body of evidence showing that tropical invaders can adjust cold tolerance downwards via plasticity or acclimation. Such changes may allow tropical invaders to expand their geographic range into colder regions of non-native ranges

A taxonomic review of Rhinolophus coelophyllus Peters 1867 and R. shameli Tate 1943 (Chiroptera: Rhinolophidae) in continental Southeast Asia

Recent field studies have provided new data for a review of the taxonomy, acoustic characters, distribution, and ecology of two often confused rhinolophid species, which have essentially parapatric distributions in continental Southeast Asia. Rhinolophus coelophyllus is widespread ranging from northern Myanmar to northern Malaysia, eastern Thailand and provisionally western Lao PDR. R. shameli is restricted to eastern Thailand, Cambodia, Lao PDR, and central and southern Vietnam. There are well defined differences in skull morphology, size, and echolocation call frequency, which discriminate between the two taxa