Salmonella enterica Infection of Synanthropic Non-native Geckos in Southern Florida.

Wild geckos are a significant source of human salmonellosis. We swabbed the cloacas of 37 non-native synanthropic geckos (Gekko gecko, n = 16; Phelsuma grandis, n = 21) from southern Florida, USA, and assayed swab DNA extracts using quantitative polymerase chain reaction of the invA gene. Salmonella enterica was detected in both species with a pooled prevalence of 13.5% (5/37; 95% CI 5.3-27.1%), indicating the potential for zoonotic transmission. Implications for human health in the region are discussed.

In situ adaptation and ecological release facilitate the occupied niche expansion of a non-native Madagascan day gecko in Florida.

AIM: To investigate whether the frequently advocated climate-matching species distribution modeling approach could predict the well-characterized colonization of Florida by the Madagascar giant day gecko Phelsuma grandis. LOCATION: Madagascar and Florida, USA. METHODS: To determine the climatic conditions associated with the native range of P. grandis, we used native-range presence-only records and Bioclim climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence-only data and projected it onto Madagascar. We constructed a third model using native-range presences for both P. grandis and the closely related parapatric species P. kochi. RESULTS: Despite performing well within the native range, our Madagascar Bioclim model failed to identify suitable climatic habitat currently occupied by P. grandis in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by P. kochi. The model built using the combined P. kochi/P. grandis dataset modestly improved the prediction of the range of P. grandis in Florida, thereby implying competitive exclusion of P. grandis by P. kochi from habitat within the former's fundamental niche. These findings thus suggest ecological release of P. grandis in Florida. However, because ecological release cannot fully explain the divergent occupied niches of P. grandis in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida. MAIN CONCLUSIONS: Our models suggest that the discrepancy between the predicted and observed range of P. grandis in Florida is attributable to either in situ adaptation by P. grandis within Florida, or a combination of such in situ adaptation and competition with P. kochi in Madagascar. Our study demonstrates that climate-matching species distribution models can severely underpredict the establishment risk posed by non-native herpetofauna.

A Global-Scale Mid-Domain Effect Cannot Explain the Latitudinal Gradient in Species Richness.

The latitudinal gradient in species richness is perhaps the most fundamental pattern of biodiversity, yet a satisfactory explanation for its existence remains elusive. A geometric "mid-domain effect" is often cited as having potential to help explain the latitudinal gradient in species richness, but the logic underpinning this hypothesis is apparently built on two incorrect assumptions: (1) that a given great circle-usually the Equator-can constitute the geometric "mid-domain" of the Earth's surface, and (2) that geophysical or bioclimatic boundaries are of geometric relevance in the context of a global-scale mid-domain effect. This article gives a brief overview of the relevant literature and history of thought on the subject, and describes in clear and simple terms why a global-scale mid-domain effect cannot arise, and thus cannot possibly represent a mechanistic basis for the latitudinal gradient in species richness. Explicit acknowledgement of this fact is of great importance, as it allows us to dispense with a commonly cited hypothesis for the latitudinal gradient in species richness.