Human‐induced globalization of insular herpetofaunas

Abstract

Aim: The aim was to document the impact of the globalization of human activity on the biodiversity and biogeographical patterns of reptilian and amphibian faunas across islands worldwide. Location: Islands worldwide. Time period: From the 15th century to the present time. Major taxa studied: Reptiles and amphibians. Methods: We compiled lists of the reptilian and amphibian species that occurred on islands before the 15th century and of those that occur currently. For each species group, we calculated differences in species richness and in compositional similarities among islands, between the two periods. Regression models were used: (a) to associate the observed differences with spatial patterns of geographical, climatic, biotic and human factors; and (b) to quantify changes in the relative importance of non-human factors in explaining the spatial patterns of species richness and compositional similarity. Results: The richness of reptile and amphibian species increased consistently across islands worldwide. Hotspots of increase were detected in the Caribbean and the Indian Ocean. The composition of species assemblages was substantially homogenized; this was particularly true for amphibians within the Caribbean Sea and for reptiles within the Caribbean Sea and Indian Ocean and between the Indian and the Pacific Oceans. Our results showed that spatial patterns of change in species richness and compositional similarity are driven by human and natural factors. The driving role of mean annual temperature is particularly consistent, and current reptile richness and compositional similarity patterns for both species groups are increasingly being shaped by the global temperature gradient. Main conclusions: The globalization of human activity is eroding the regionalized character of insular herpetofaunas and leading to the emergence of global-scale gradients of taxonomic composition and species richness. Projections of increasing rates of biological invasions, extinctions and climate change suggest that these changes are likely to be aggravated even further in the coming decades.

Bridgehead effects distort global flows of alien species

“…Although there are 252 alien ant species worldwide, more than half of the established species in 83% of countries were established on all six continents. This implies that the global homogenization of alien species was due to a minority of widespread alien species, which has been observed in other taxa (Baiser et al, 2012;Capinha et al, 2020;Weigelt et al, 2016;Winter et al, 2009),. Yet, these taxa dominated intercontinental exchanges and blurred the links between actual donor and recipient regions.…”

Reproductive plasticity as an advantage of snakes during island invasion

“…Snakes become part of the global spread of invasive reptiles by stowing away and other human mediated processes (Capinha, Marcolin, & Reino, 2019). When tied with snakes' cryptic behavior, their ability to survive for long times without food, and their ability to deal with broad environmental conditions, snakes' ability to stow away greatly increases the risk that live snakes will arrive in new ecosystems through cargo and other inadvertent transit.…”

ReptIslands: Mediterranean islands and the distribution of their reptile fauna

“…Early works on island biogeography focused on how key geographical features of islands (e.g., area and isolation) determine species richness through a dynamic equilibrium between species colonization, extinction and speciation (McArthur & Wilson, 1967; Whittaker & Fernández‐Palacios, 2007). More recent works have added complexity to biogeographical analyses, stressing that isolation is a complex of factors that influence insular biodiversity (Itescu et al., 2020; Weigelt & Kreft, 2013) and that many factors beyond geographical features influence species distribution on islands, such as habitat heterogeneity, human influence and climate (Capinha et al., 2020; Helmus et al., 2014; Losos & Ricklefs, 2010; Santos et al., 2016; Whittaker & Fernández‐Palacios, 2007).…”