Beyond the Last Glacial Maximum: Island endemism is best explained by long-lasting archipelago configurations

• Articles in SCI Journals
• Jan, 2019

Summary:

Aim: To quantify the influence of past archipelago configuration on present-day insular biodiversity patterns, and to compare the role of long-lasting archipelago configurations over the Pleistocene to configurations of short duration such as at the Last Glacial Maximum (LGM) and the present-day.

Location: 53 volcanic oceanic islands from 12 archipelagos worldwide – Azores, Canary Islands, Cook Islands, Galápagos, Gulf of Guinea, Hawaii, Madeira, Mascarenes, Pitcairn, Revillagigedo, Samoa, and Tristan da Cunha.

Time period: The last 800 Kyr, representing the nine most recent glacial­–interglacial cycles.

Major taxa studied: Land snails and angiosperms.

Methods: Species richness data for land snails and angiosperms were compiled from existing literature and species checklists. We reconstructed archipelago configurations at the following sea-levels: the present-day high interglacial sea-level, the intermediate sea-levels that are representative of the Pleistocene, and the low sea-levels of the LGM. We fitted two alternative linear mixed models for each archipelago configuration on the number of single-island endemic, multiple-island endemic, and native non-endemic species. Model performance was assessed based on the goodness-of-fit of the full model, the variance explained by archipelago configuration, and model parsimony.

Results: Single-island endemic richness in both taxonomic groups was best explained by intermediate palaeo-configuration (positively by large palae- area, and negatively by palaeo-connectedness), whereas non-endemic native species richness was poorly explained by palaeo-configuration. Single-island endemic richness was better explained by long-lasting intermediate archipelago configurations than by the short-lasting archipelago configurations of the LGM or present-day.

Main conclusions: Archipelago configurations at intermediate sea-levels – which are representative of the Pleistocene – have left a stronger imprint on single-island endemic richness patterns on volcanic oceanic islands than extreme archipelago configurations that persisted for only a few thousand years (such as the LGM). In understanding ecological and evolutionary dynamics of insular biota it is essential to consider longer-lasting environmental conditions, rather than extreme situations alone.

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https://onlinelibrary.wiley.com/doi/10.1111/geb.12835