Factors Restricting Range Expansion for the Invasive Green Anole Anolis carolinensis on Okinawa Island, Japan

Photograph was taken in Hahashima, Ogasawara Islands, by Hideaki Mori.

We would like to introduce our recent paper on the invasive green anole (Suzuki-Ohno et al. 2017). In Japan, the green anole Anolis carolinensis invaded the Ogasawara Islands in 1960’s and Okinawa Island in 1980’s. In Ogasawara Islands, A. carolinensis expanded its range and had a significant negative impact on native species and the ecosystem. This becomes a big problem since Ogasawara Islands are designated as a natural heritage.

On Okinawa Island, A. carolinensis was first captured in 1989 and it did not expand its distribution until more than 25 years later, although its density is extremely high in the southern region. In the northern region of Okinawa Island, Yambaru area, native forests are preserved so that it is important to avoid the invasive effects of A. carolinensis. Thus, It is important to determine whether A. carolinensis has the potential to expand its distribution on Okinawa Island.

Phylogenetic analysis shows that the invader A. carolinensis originated in the western part of the Gulf Coast and inland areas of the United States. Interestingly, all of the invaded A. carolinensis in Ogasawara, Okinawa and Hawaii originated from the Gulf Coast and inland areas of the United States.

ND2 phylogeny using Okinawan, Ogasawaran, and Hawaiian populations in addition to haplotypes used by Campbell- Staton et al. (2012) and Hayashi et al. (2009).The major branches with high posterior probabilities of the Bayesian inference method (>0.99) are indicated in bold. The map was redrawn from Campbell-Staton et al. (2012). Cited from Suzuki-Ohno et al. (2017). Figure 2 of Suzuki-Ohno et al. (2017) lacks bold lines in error.

We used a species distribution model (MaxEnt) based on the distribution of native populations in North America to identify ecologically suitable areas on Okinawa Island. The MaxEnt predictions indicate that most areas in Okinawa Island are suitable for A. carolinensis. Therefore, A. carolinensis may have the potential to expand its distribution in Okinawa Island.

MaxEnt prediction of suitable areas for A. carolinensis in Okinawa Island according to the presence data for North America. Lighter and darker areas indicate high or low suitability, respectively. Points indicate the presence distribution of A. carolinensis. (a) prediction using all parameters, (b) prediction omitting mean diurnal range and precipitation of warmest quarter. Cited from Suzuki-Ohno et al. 2017.

The predictions indicate that habitat suitability is high in areas of high annual mean temperature and urbanized areas. The values of precipitation in summer in the northern region of Okinawa Island were higher compared with those of North America, which reduced the habitat suitability in Okinawa Island. Adaptation to low temperatures, an increase in the mean temperature through global warming, and an increase in open environments through land development will likely expand the distribution of A. carolinensis in Okinawa Island. We think that invasive anoles (A. calrolinensis and A. sageri) prefer open habitats.

Therefore, we suggest that A. carolinensis should be removed by using traps and/or chemicals. In addition, we must continue to be alert to the possibility that city planning that increases open environments may cause their range to expand.

These results were published as Suzuki-Ohno et al. (2017) Factors restricting the range expansion of the invasive green anole Anolis carolinensis on Okinawa Island, Japan. Ecology and Evolution