Australian house geckos are more aggressive than a globally successful invasive Asian house gecko

Abstract

Invasive species are implicated in native species declines globally, but predicting the effect of specific invaders on a given native species remains difficult. Many successful invaders are highly aggressive, whereas others are not. The highly successful invasive Asian house gecko, Hemidactylus frenatus, has achieved a pantropical distribution. We investigated direct interactions between H. frenatus and a sympatric native Australian house gecko (Gehyra dubia) to determine the strength and nature of aggressive exclusion and which species may be competitively superior. Intraspecific aggression was strong in the native, and individuals were more aggressive as residents than as intruders, suggesting this species shows site defence. In contrast, the invasive species displayed little aggression in intraspecific encounters. Overall, residents of the native species were more aggressive than residents of the invasive species. Aggression in the native species was influenced by the degree of aggression of the intruding gecko, but not by the species of intruder. Aggression from invasive residents was low and was not influenced by either the intruder's species or their behavior. Our study suggests that native Australian house geckos (G. dubia) are unlikely to be directly displaced by invasive H. frenatus, but rather that this native gecko will aggressively defend its resources when necessary. In this case, the tolerance of the invasive species for others in close proximity may contribute to its success.