Conclusions
The Aegean continental islands were separated from the mainland for a
very long period of time (>2.6 Ma) thus promoting endemism;
the extreme and recent paleo-configurations of high connectivity with
the mainland that started with the onset of the Quaternary greatly
affected their species richness and speciation patterns. These
connections with the mainland manifested as “shocks” of sorts, when
isolated islands became connected with the mainland (Sondaar and Van der
Geer 2005). We hypothesise that increasing lower sea levels over the
Quaternary period led to migration waves of continental species to ever
more continental islands disrupting allopatric evolutionary processes,
induced extinctions in single island endemic species, ultimately leading
to signals of endemic underrepresentation and native supersaturation
tuned to the most extreme (LGM) configurations prevalent at the end of
the Pleistocene. We noted for some multiple endemic chorotypes, the high
z-values on land-bridge islands and a dependency on present day
distance, which may reflect a relict response to the pre-Quaternary
conditions, when these land-bridge islands still were true islands.
Continental systems therefore hold ample evidence of the effect of
paleogeography on the species richness, speciation and biogeographical
patterns of the Aegean islands. The noted principal differences in
geographic and evolutionary mechanisms between oceanic and continental
islands make statistical assessments of endemic species data of combined
oceanic and continental islands fundamentally problematic and studies
involving both systems should explicitly incorporate their differences
in statistical models.