Population Density of a Clonal Gecko Species in Its Northernmost Range, the Ryukyus in Japan

Many species of organisms are known to have expanded their distributional ranges and established highly dense populations in their nonnative areas due to human activities. Several gecko species have been introduced from tropics to seasonal subtropics with the aid of artificial transportations. However, it has not yet been well-documented as to whether invasive tropical geckos flourish in extra-tropical cooler areas outside their native range. Here, I report demographic information of the mourning gecko, Lepidodactylus lugubris , in its northernmost distribution, the Ryukyu Archipelago in Japan. I conducted a mark-recapture survey of mourning geckos inhabiting a coastal vegetation habitat and estimated their population size using the Jolly-Seber open population model. An estimated 94–284 individuals lived in a small beachfront forest. The population showed a high density (880–2,656 geckos/ha), which is comparable to that of other invasive gecko populations in tropical areas. The results imply a successful colonization of clonal geckos at their northernmost invasion front.