Extinction Resilience of Island Species: An Amphibian Case and a Predictive Model

Abstract

Extreme overall divergence and high extinction rates are typical of insular endemics. Thus, detecting and understanding nativeness is critical on islands. Resilience to extinction is explored through a mechanistic approach focusing on midwife toads (Anura: Alytidae: Alytinae), an ancient lineage that includes continental and insular species. All alytines need urgent conservation action, including control of emerging diseases and spatially explicit reserve design aimed at ensuring ecosystem health and connectivity. The only extant insular alytine is additionally affected by an introduced continental predator. This alien species acts as a driver of the prey's near-extinction and has not elicited any evolutionary response. Both IUCN criteria and EDGE scores show that alytines are top conservation priorities. However, there is a need for also considering phenotypic and ecological uniqueness in the assessment of conservation status and urgency. The reason is that phenotypes render ecosystems functional and insular ones uniquely so. In contrast, phylogenetic relatedness is just a constraint upon, not a motor of, evolutionary novelty. Insular species are indeed particularly susceptible, but can be similarly endangered as continental ones. This paradox may be solved by recognizing the insularity syndrome in any isolated or nearly-insular ecosystem, as a function of evolutionary and dispersal potentials. This predictive model may be useful for island biogeography, invasion biology and conservation planning.

Extinction through Climate Change: Review of Evidence and Analysis of Two Land Snails from the Seychelles Islands

“…On continents, changing weather has been invoked in several extinctions. In spite of previous hypotheses involving global atmospheric changes [44], it is now clear that the widespread decline of amphibians is causally linked to the human-induced expansion of chytridiomycosis [45,46] southern South America, but vanished just over three centuries ago. At that time the original grasslands experienced deep changes [47].…”

“…The snail's decline might have been caused by the combined effects of several exotic invasive species (Figure 5c). Non-native species have deep effects on island ecosystems [20,46]; remote and inhospitable Aldabra is no exception. The atoll's vegetation suffered exotic invasive species that look wrought havoc on that remote island.…”

Ensemble Models Predict Invasive Bee Habitat Suitability Will Expand under Future Climate Scenarios in Hawai’i

“…Endemic Hylaeus are especially vulnerable to the impacts of climate-induced biological invasions because they have fewer opportunities to adapt by altering their distribution [31,33]. The smaller land area of islands generally translates into very small populations and ranges for endemic insects such as Hylaeus [31,[34][35][36]. Additionally, because of the limited area, Hylaeus endemic to Hawai'i are more vulnerable to invasive species through competition, predation, and disease spread [18,36,37].…”

Global Climate Change Impacts on Pacific Islands Terrestrial Biodiversity: A Review

“…Island species may be limited in their ability to cope with climate change due to a range of characteristics, including smaller geographic ranges, limited genetic variation, small colonizing populations, reduced species richness, and poor adaptations to avoid predation [13,18,23,[25][26][27]. The smaller land area of islands provides a smaller realized niche space, which generally translates into very small ranges for island species and especially for endemics [28,29]. As a result, harmful effects from climate change can encompass an island species' entire habitat more readily than a continental species' habitat [30].…”