Thermal and Behavioral Adaptations of the Invasive Asian House Geckos (Hemidactylus frenatus)
- Publication Type:
- Thesis
- Issue Date:
- 2021
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The Asian house gecko (𝘏𝘦𝘮𝘪𝘥𝘢𝘤𝘵𝘺𝘭𝘶𝘴 𝘧𝘳𝘦𝘯𝘢𝘵𝘶𝘴) is one of the most widespread invasive species in the world; however, little is known about the factors that facilitated the success of this invasive gecko. Despite the tropical origin, the gecko has established populations in temperate regions of southeastern Australia. Therefore, I investigated thermal tolerance, thermal hardening, and thermal preference of the introduced geckos in New South Wales (NSW), in comparison with their native populations in Thailand. I found that house geckos from NSW could tolerate colder temperatures, responded to thermal stresses faster, and selected lower body temperatures than geckos from Thailand. The introduced geckos also showed an ability to acclimate seasonally and thermoregulate after feeding (post-feeding thermophily). These thermal adaptions would enable the geckos to survive and perform well in the cold climate of temperate regions, and conserve energy during the winter when food is limited.
Previous studies suggested that successful invasive species have a suite of correlated behaviors that facilitate the invasion. However, since the benefits of each behavior could vary among situations, the ability to adjust behaviors should be necessary for invasive species. Therefore, I investigated the behaviors of the Asian house geckos from different populations to determine the effects of community composition on the expressions. For exploratory behavior, I found that the geckos from core communities tended to hide more and explore less. This behavioral type ensures their safety, as well as increases their chance of getting introduced. In contrast, the geckos from edge populations tended to hide less and explore more, so they should extend their range quickly. For agonistic behavior, I found that the geckos from a competitor-rich community were more aggressive than conspecifics from a competitor-released community. I suggest that the geckos adjust their behavior to balance the trade-off between access to resources and energy consumption.
My study has demonstrated the ability of the Asian house gecko to adjust both thermal biology and behavior in responding to different ecological contexts. Therefore, the gecko is likely to expand its range further, and cause problems beyond those predicted by static models. More screening of entry points, and community-based citizen science projects whereby people identify house geckos and their locations, may help to control and prevent future spread. Future studies of the molecular pathways underpinning shifts in thermal biology, along with studies of aggressive behaviors in other communities, would be useful for evaluating the generality of my results.
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