10.5061/DRYAD.15DV41NS9
Itescu, Yuval
0000-0002-6301-7112
Freie Universität Berlin
Foufopoulos, Johannes
University of Michigan–Ann Arbor
Pafilis, Panayiotis
National and Kapodistrian University of Athens
Meiri, Shai
0000-0003-3839-6330
Tel Aviv University
The diverse nature of island isolation and its effect on land-bridge
insular faunas
Dryad
dataset
2020
2020-10-23T00:00:00Z
2020-10-23T00:00:00Z
en
93581 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Aim Isolation is a key factor in island biology. It is usually defined as
the distance to the geographically nearest mainland, but multiple
alternatives exist. We explored how testing different isolation indices
affects the inference of isolation effects on faunal characteristics. We
focused on land-bridge islands and compared the relationships of multiple
spatial and temporal (i.e., through time) isolation indices with
community-, population-, and individual-level characteristics (species
richness, population density, and body size, respectively). Location
Aegean Sea islands, Greece. Time period: current. Taxon Multiple animal
taxa. Methods We estimated 21 isolation indices for 205 islands, and
recorded species-richness data for 15 taxa (invertebrates and
vertebrates). We obtained body size data for seven lizard species and
population density data for three. We explored how well indices predict
each characteristic, in each taxon, by conducting a series of OLS
regressions (controlling for island area when needed), and a
meta-analysis. Results Isolation was significantly (and negatively)
associated with species richness in ten of 15 taxa. It was significantly
(and positively) associated with body size in only one of seven species,
and was not associated with population density. The effect of isolation on
species richness was much weaker than island area, regardless of the index
tested. Spatial indices generally outperformed temporal indices, and
indices directly related to the mainland outperformed those related mainly
to neighbouring islands. No index was universally superior to others,
including the distance to the geographically nearest mainland. Main
Conclusions The choice of index can alter our perception of the effects of
isolation on biological patterns. The nearly automatic, ubiquitous, use of
distance to the geographically nearest mainland misrepresents the
complexity of isolation effects. We recommend to simultaneously test
multiple indices, that represent different aspects of isolation, to
produce more constructive and thorough investigations and avoid imprecise
inference.