ALBERT

Description: 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, Samoan Islands, 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 area change, 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 intermediate archipelago configurations than by the 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.

Description: The Paleo Islands and Archipelago Configuration (PIAC) database containins sea level driven paleogeography changes over the late Quaternary of 178 islands in 27 archipelagos. The workflow developed to calculate archipelago configuration and paleo-area is provided to allow calculations for other islands, time steps, and higher spatiotemporal resolutions.