Centipede diversity
The remarkably low z-value (<0.18) for all centipedes, even
lower than reported for vertebrates (Triantis et al. 2008), is probably
explained by low degrees of island isolation fitting with the
paleogeography of the Aegean, where most of the islands were recently
connected either with continental Greece or the Anatolian peninsula.
Although Crete became permanently isolated approximately 9 Mya from
Anatolia to the east and 5.5 Mya from mainland Greece from the west, the
majority of the islands were isolated less than 21 Kya (Perissoratis and
Conispoliatis 2003). The absence of endemic centipedes on land-bridge
islands confirms our H2, namely that endemism is demoted
on land-bridge islands. For native centipedes, higher z-values and
R2 values on true islands compared to land-bridge
islands support higher levels of native centipede diversity. This
counterintuitive trend is most likely a reflection of suitable
cryptozoic habitat types on true islands, the change of occurring on
these islands increases with island size. All centipedes are predatory
soil animals with distinguished dispersal abilities that show ecological
preferences to microhabitats such as leaf litter in the upper soil
layer, into cavities in the deeper soil layers as well as under stones
and barks (Voigtländer 2011). Because
of their cryptozoic life-style most centipede species seem to be more
insensitive than most angiosperms to geographical changes caused by
sea-level rise in the Aegean archipelago. This could justify the less
significant role of paleogeography (LGM and median) in the diversity
patterns of the centipedes in the Aegean archipelago. One of the most
exceptional features of certain centipede species, particularly
geophilomorphs, is that they reside on the sea shore between tidemarks
(e.g. Pachymerium ferrugineum , Tuoba poseidonis , see Lewis
1981). Thus, periods of high rates of sea-level rise such as following
the LGM might have caused fast extinctions in these taxa, leading faster
to a new equilibrium. Centipede species richness is therefore mainly
determined by present-day geography (Table 1), with area and distance
from mainland being the most significant variables for total species
richness, meaning that centipedes tend to be faunistically relaxed.
However, Kastelorizo, Ro and Stroggyli are supersaturated with
centipedes as a result of their connection to Turkey during the LGM.
Kastelorizo for example is about 800 times smaller than Crete but hosts
19 species of centipedes – roughly half the richness found in Crete.