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Who Is Paying the Extinction Debt? Phylogenetic and Functional Structuring on Greek Islands Is Shaped by Sea-Level
Nathan M Michielsen1,2,3, Cyril Hammoud4, Johannes Foufopoulos5
1Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam Amsterdam the Netherlands.
Ecology and Evolution
|June 30, 2026
Summary
Global sea-level rise reshaped islands since the Last Glacial Maximum, causing extinctions. Island age and isolation drive species loss through competition, favoring more distantly related species.
Area of Science:
- Ecology
- Paleogeography
- Evolutionary Biology
Background:
- Global sea-level rise since the Last Glacial Maximum has altered coastlines, fragmenting islands and impacting island communities.
- Island community dynamics are influenced by geographical changes, but the specific ecological drivers of species extinction remain unclear.
Purpose of the Study:
- To investigate how past geographical changes influenced island community structure.
- To assess the ecological processes driving species extinction patterns on Mediterranean islands.
Main Methods:
- Integration of a paleo-coastline model with squamate (reptile and amphibian) community data from 163 Mediterranean islands.
- Evaluation of phylogenetic and functional community structure in relation to paleogeographic variables.
Main Results:
- Phylogenetic overdispersion, where co-occurring species are more distantly related than expected, dominates island communities.
- Phylogenetic overdispersion is more pronounced on older islands, suggesting ongoing community relaxation and extinctions driven by interspecific competition.
- Island time-since-isolation is the strongest predictor of phylogenetic structuring, indicating longer isolation leads to selective extinction of closely related species.
Conclusions:
- Relaxation dynamics, particularly interspecific competition, significantly shape insular communities.
- Island age and isolation are key factors influencing phylogenetic structure and extinction patterns.
- Understanding past geographical changes is crucial for predicting future island community assembly.
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