Biodiversity on islands is influenced by geophysical processes and sea-level fluctuations. Oceanic islands (never connected to a landmass) are initially vacant with diversity accumulating via colonisation and speciation, and then declining as islands shrink. Continental islands have species upon disconnection from the mainland and may have transient land-bridge connections. Theoretical predictions for the effects of these geophysical processes on rates of colonisation, speciation, and extinction have been proposed. However, paleogeographic reconstructions are currently unavailable for most islands, and phylogenetic models overlook island ontogeny, sea-level changes, or past landmass connections. We analyse to what extent ignoring geodynamics in the inference model affects model predictions when confronted with data simulated with geodynamics.
Simulations of oceanic and continental islands.
We extend the island biogeography simulation model DAISIE to include: (i) area-dependent rates of colonisation and diversification associated with island ontogeny and sea-level fluctuations, (ii) continental islands with biota present upon separation from the mainland, and (iii) shifts in colonisation to mimic temporary land-bridges. We quantify the error of ignoring geodynamic processes by applying DAISIE's inference method to geodynamic simulations.
Robustness of the model to dynamic island area is generally high for oceanic islands and for continental islands that have been separated for a long time, suggesting that it is possible to obtain reliable results when ignoring geodynamics. However, for continental islands that have been recently or frequently connected, robustness of the model is low.
Under many island biogeographic geodynamic scenarios (oceanic islands and ancient continental fragments) a simple phylogenetic model ignoring geodynamics is empirically applicable and informative. However, recent connection to the continent cannot be ignored, requiring new model development. Our results show that for oceanic islands, reliable insights can be obtained from phylogenetic data in the absence of paleogeographic reconstructions of island area.
- community assembly
- continental island
- island biogeography
- island ontogeny
- phylogenetic analysis
- robustness analysis