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\begin{document}

\title{Extreme and short-lasting sea-level stands structure insular species
diversity of a continental-shelf archipelago (Aegean Sea, Greece)}



\author[1]{Cyril Hammoud}%
\author[2]{Konstantinos Kougioumoutzis}%
\author[3]{Kenneth F. Rijsdijk}%
\author[4]{Stylianos Simaiakis}%
\author[5]{Sietze Norder}%
\author[3]{E. Emiel Van Loon}%
\affil[1]{Ghent University}%
\affil[2]{University of Athens}%
\affil[3]{Universiteit van Amsterdam}%
\affil[4]{Natural History Museum - Crete}%
\affil[5]{Universidade de Lisboa}%


\vspace{-1em}



  
  \date{March 12, 2025}


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\selectlanguage{english}
\begin{abstract}
Recent research in island biogeography has highlighted the important
role of late Quaternary sea-level fluctuations in shaping
biogeographical patterns in insular systems, but largely focused on
volcanic oceanic systems. Through this study we aim to extend this work
by investigating the role of late Quaternary sea-level fluctuations in
shaping species richness patterns in continental shelf island systems.
Focusing on the Aegean archipelago, we first reconstructed the area's
geography using published data, under three sea-level stands: 1)
current; 2) median over the last nine Glacial-Interglacial cycles; 3)
Late Glacial Maximum (LGM). We compiled taxon-island occupancy for
angiosperms (70 islands) and centipedes (56 islands). We investigated
the impact of present-day and past geographical settings on chorological
groups by analysing Island Species-Area Relationships (ISARs) and using
Generalized Linear Mixed Models selection based on multiple metrics of
goodness-of-fit. Our results confirm that the Aegean's geography has
changed dramatically since the LGM, while the median sea-level scenario
only modestly differs from the present configuration. Paleogeographical
changes largely shaped Aegean plant diversity patterns, and to a lesser
degree centipede species richness patterns. The LGM geographic
configuration affected both native and endemic species diversity through
establishing connections between land-bridge islands and the mainland.
Particularly on land-bridge islands we detected supersaturation of
native species and stronger underrepresentation of endemics on those
same islands. Unlike oceanic islands, where the longer lasting median
configuration has ample effect on the current species diversity, the
shorter lasting LGM configurations promoted increased connectivity with
the mainland counteracting processes promoting endemism. Our study shows
that in terms of processes affecting species richness patterns,
continental archipelagos differ fundamentally from oceanic systems,
highlighting the importance of distinguishing between them while
studying biota from the perspective of historical biogeography.%
\end{abstract}%



\sloppy


Introduction

Islands are dynamic entities with continuously evolving geographical
settings influencing the distribution and genetic evolution of organisms
they host. At deep time scales (Ma), an island's ontogeny is controlled
by geological processes (Whittaker et al. 2008), while on shorter time
scales climatic processes dominate. Climate drives major sea-level
fluctuations causing islands to shrink and expand, fragment and merge,
or even disappear and emerge (e.g. Simaiakis et al. 2017).
Late-Quaternary sea-level changes have left their imprint on insular
species diversity patterns (Ali and Aitchison 2014, Rijsdijk et al.
2014, Weigelt et al. 2016, \selectlanguage{ngerman}Ávila et al. 2018, 2019, Norder et al. 2019).
All of these did however focus on volcanic oceanic islands, or did not
make a distinction between oceanic volcanic and continental insular
systems and lumped them in their analyses (Weigelt et al. 2016, Veron et
al. 2019). By disregarding the specifics of continental archipelagos,
relevant biogeographical processes are potentially overlooked (Ali 2017,
Simaiakis et al. 2017, Whittaker et al. 2017).

Continental shelf islands (\emph{sensu} Ali 2017) are characterized by
sitting on a continental shelf and may include ``land-bridge'' islands,
that were connected to the mainland in the past when sea levels were
lower. Another characteristic is the proximity of the mainland often
surrounding continental islands (Weigelt and Kreft 2013). The
geo-spatial effects of sea-level dynamics on continental island biota
have been studied extensively (e.g. Diamond 1972, Cardillo et al. 2008,
Itescu et al. 2020). The Aegean archipelago in the Mediterranean Sea is
located between the Greek and the Anatolian peninsulas, and is one of
the largest archipelagos on Earth (Blondel et al. 2010). Its complex
geological history and high environmental heterogeneity contribute to
its high biodiversity and endemism, thus rendering an ideal stage for
biogeographical studies (Strid 2016). The Aegean islands form a typical
continental shelf archipelago with a high geological heterogeneity and
numerous land-bridges due to sea-level change. Unsurprisingly, its
biogeography has been studied intensively (e.g. Triantis et al. 2018).
Although providing crucial biogeographical insights, most studies remain
limited in scope by focusing on a single explanatory factor of interest:
i.e., by not distinguishing between native and endemic species (Itescu
et al. 2020), by considering a single species group or a limited part of
the archipelago (e.g. Panitsa et al. 2010). The combined effect of area
change, fragmentation and connectivity driven by sea-level changes on
insular species diversity has never been investigated for the Aegean
archipelago; while we think that such a combined analysis is crucial to
interpret the relevant biogeographic processes correctly (see
Kougioumoutzis and Tiniakou 2014, Norder et al. 2019). Moreover, the
influence of continental land-bridge islands on biodiversity patterns in
different chorotypes as reflected in multivariate models and Island
Species-Area Relationships (ISARs) has never been quantitatively
assessed (e.g. Triantis et al. 2008, 2012). Since we have recently
quantified the paleogeographic change of islands in the Aegean Sea
(Simaiakis et al. 2017) and its biota are well studied, this setting
represents an ideal study system to test our hypotheses.

Our aim is to investigate the combined impact on continental insular
species diversity of current as well as past island area and
connectivity for the Aegean archipelago for two well-studied taxonomic
groups, angiosperms and centipedes. Our first hypothesis
(H\textsubscript{1}) is that more native species occur on land-bridge
islands than on true islands, reflecting the higher establishing rates
of native species on land-bridge islands (Simaiakis et al. 2017). Our
second hypothesis (H\textsubscript{2}) is that endemism is negatively
influenced by land-bridge islands, as allopatric speciation is
suppressed by repetitive gene-flow from the continents. Our third
hypothesis (H\textsubscript{3}) concerns the effect of the duration of
the archipelagic configurations as a result of sea-level drop affecting
richness patterns. On oceanic islands, the median archipelago
configuration could largely explain the endemism richness patterns than
the extreme and short-lasting Late Glacial Maximum (LGM) configuration
(Norder et al. 2019). Thus on land-bridge islands, the long-lasting
median glacial configuration may have largely influenced the species
richness patterns, rather than the short lasting LGM extreme state,
assuming that short-lasting spatial configurations do not provide the
time needed for speciation to occur. To test our hypotheses, we analyse
the effects of land-bridge islands on species richness of different
endemism levels. We investigate H\textsubscript{3} by analysing species
richness patterns in relation to two paleogeographical settings: 1)
during LGM, and 2) the median sea level during the last
glacial-interglacial cycle (Figure 1).

\textbf{Method}

\emph{The Aegean archipelago}

The Aegean is at the convergence of three tectonic plates (Anatolian,
African and Eurasian) and has therefore developed major faults systems,
resulting in the formation of the South Aegean Volcanic Arc (Higgins
2009). However, even though plate tectonics have strongly shaped the
paleo-evolution of the Aegean archipelago, its recent history has been
mainly affected by the Pleistocene climatic fluctuations (Sakellariou
and Galanidou, 2016). Compared to the magnitude of the geographical
changes caused by the sea-level oscillations during the last 150 Ka BP,
the importance of the tectonic changes occurring at the same time scale
is mostly negligible (Simaiakis et al. 2017). During the LGM (26.5 -- 19
ka BP), the global sea level was \textasciitilde{}135 m lower than
present and locally \textgreater{} 140 m lower in the Mediterranean
(Lambeck and Purcell 2005, Clark et al. 2009, Lambeck et al. 2014).
Subsequent sea-level rise caused dramatic changes in the Aegean basin
with most of the marine transgression observed during 16-11 Ka BP, when
sea-level rise rates were 12 m/1 Ka (Simaiakis et al. 2017). This led to
a major reduction of total island area by ca. 70\% in the Aegean basin
and to a rapid increase of Aegean islands. Large islands
(\textgreater{}20 km\textsuperscript{2}) were rapidly shrinking and
becoming isolated during that time (20\% and 40\% per 1 Kya,
respectively - Simaiakis et al. 2017). Islands emerged near the coast of
Turkey and Greece that were formerly peninsulas, the western connection
between the Peloponnese peninsula and the mainland was lost and the
Cycladic paleo-island fragmented into the Cyclades islands group
(Figures 1 and 2).

\emph{Target organisms}

Angiosperms and centipedes are known for their diversity and endemism
rate in the Aegean (Strid 2016, Triantis et al. 2018). Based on
biogeographical affinities, different phytogeographical regions have
been identified resulting from similar environmental conditions and
divergent historical influences (Strid and Tan 1997, Kougioumoutzis et
al. 2017).

\emph{Species richness data}

We compiled a plant matrix for 70 Aegean islands, including a total of
3246 native vascular plant taxa (species and subspecies). The
angiosperms are a well-studied group in the Aegean, and we compiled data
on five chorotypes and two combined chorotypes (Figure 1) based on an
extensive bibliographical database for the Aegean archipelago (see
Appendix S1 in Kougioumoutzis et al. 2017). The `native non-endemics',
here termed `natives', are a widely spread taxonomic group that occur
both on the Greek Islands and on the mainland across the Mediterranean
(2673 taxa).

The `Greek endemics' are species exclusively occurring both on the Greek
mainland and the Aegean islands (689 Taxa). The `Aegean endemics' (AE)
are found on multiple islands but not on the mainland (91 taxa). The
'phyto-region endemics' (PE) are restricted to one or multiple islands
located within the same Aegean phytogeographical region
\emph{sensu}Strid and Tan (1997 - 384 taxa). Finally, the single island
endemics (SIEs), are endemics occurring exclusively on one of the Aegean
islands (292 taxa). We also combined chorotypes to compare general
trends of endemics with non-endemics and to assess trends in similar
multiple endemics chorotypes. We combined both phyto-region and Aegean
endemics to form `multiple islands endemics' (MIEs) \emph{sensu stricto}
(450 taxa). We also combined all endemic chorotypes into an
``all-endemics group'' (E\textsubscript{ALL}).

A similar matrix was compiled for 56 Aegean islands and 70 centipedes
(see Simaiakis et al. 2004, 2005). Two chorotypes were distinguished:
`native' and `endemics' (65 and 5 species, respectively). The data set
for single island endemics of centipedes was too small for a statistical
assessment.

\emph{Paleo-island morphometry}

To test our hypotheses, we estimated the past insular areas and
distances to the mainland in order to use these metrics as predictors of
current species diversity. Herein, we were interested in the difference
between the present-day geographical setting, the situation during the
LGM and the situation under the median sea level over the last nine
glacial-interglacial cycles (MSL - Norder et al. 2019). Hence, besides
the present-day configuration of the Aegean islands, we used the work by
Simaiakis et al. (2017 -- Supplementary Material Appendix 1) for
paleogeographical configurations. To investigate the biogeographical
effects of past fragmentation from the mainland, we classified islands
into two different groups: those that remained isolated from the
mainland, referred to as ``true islands'' \emph{versus} those with an
episodic connection to the mainland during the LGM (``LGM land-bridge
islands'') or at median sea level (``median land-bridge islands'' -
Simaiakis et al. 2017).

\emph{Inferential analysis}

ISARs were fitted using the logarithmic transformation of the Arrhenius
(1921) power model. We compared the models using
adjusted-R\textsuperscript{2} values as a measure of their
goodness-of-fit. As the models have the same number of fitted
parameters, the R\textsuperscript{2} are directly comparable, without
modification (Triantis et al. 2005). We also calculated the mean
area-adjusted species richness for all angiosperm and centipede
chorotypes and distinguished between true and land-bridge islands. To
investigate the impact of past geographical changes on current
diversity, we compared the performance of three alternative generalized
linear mixed models (GLMMs) in explaining species richness. The models
correspond to the geographical setting of the Aegean at three stages:
present-day, LGM and MSL. The present-day model (null model) consisted
of present-day area, distance to the mainland, and spatial
autocorrelation as fixed effect and phytogeographical province as random
effect. The models for the paleogeographical settings (LGM or median)
included the same predictors as the null model plus the following
metrics of change in insular geography compared to the present-day
setting: area loss, increase of distance to the mainland and whether an
island was a land-bridge island or remained a true island. We fitted
these three sets of predictors on the following response variables: the
species richness of all six chorotypes of angiosperms, the total
angiosperm species richness, total angiosperm endemics richness and
total centipede species richness. All models were fitted using a
log-link function and Poisson distribution for the error term (lmerTest
package, Kuznetsova et al. 2017). All variables with p-values
\textgreater{} 0.1 were excluded from the models to obtain a set of
``suggestive, but inconclusive'' predictors (Murtaugh 2014) before
refitting with the remaining variables. Multicollinearity was addressed
by computing the variance inflation factors (VIF) of the predictors and
removing variables with VIF \textgreater{} 2.5 (Dormann et al. 2013).
Finally, we identified the models that provided most explanatory
potential using multiple measures of goodness-of-fit: the corrected
Akaike Information Criterion (AICc), Bayesian Information Criterion
(BIC), conditional (R\textsuperscript{2}c) and marginal
(R\textsuperscript{2}m) R\textsuperscript{2} (MuMIn package, Barton
2009) and leave-one-out cross-validated (loocv)
pseudo-R\textsuperscript{2}. All analyses were performed in R version
3.4.2 (R core team 2018). Crete was excluded from all models fitted as
diagnostic residual plots of residuals vs. leverage systematically
designated it as an outlier (not shown). Because of the low number of
endemic centipede species and their over-dispersion in the islets
adjacent to Crete, we restrained our analysis of the centipede fauna to
native centipede diversity.

\textbf{Results}

\emph{Geographical changes in the Aegean}

Our reconstructions show that the geography of the Aegean archipelago
changed dramatically throughout the last climatic cycle of the
Quaternary (Figure 2). The current configuration and the LGM setting
represent two extremes of the sea-level fluctuations (highest now,
lowest during the LGM). Islands' morphometry and isolation varied
correspondingly: Island areas achieved a maximum size during the LGM and
are at their minimal size now, with intermediate values at the MSL,
while isolation was minimal in the LGM (Supplementary Material Appendix
2 Table A2.1). Fewer islands were connected to the mainland during the
MSL compared to the LGM (Supplementary Material Appendix 2 Table A2.2).

\emph{Explorative and inferential analyses of species richness}

The ISAR power function model explained a higher proportion of variance
on true islands than on land-bridge islands; the z-curve followed a
similar trend, apart from the Greek and phytogeographical endemics
(Table 1). Land-bridge islands appear to host more native taxa than true
islands, while the opposite trend is observed regarding endemic taxa
(Figure 3).

\emph{Models}

The proportion of variance explained was generally high for all models
(16-83\% - Table 2) and was overall greater for angiosperms than
centipedes. Biogeographical affinity explained a large proportion of
variance for all endemic categories (13-67\% - Table 2), but not for the
native angiosperms and centipedes (Table 2). Area was the most important
predictor in almost all models (Table 2; Figure 4). LGM-related
variables emerged as important predictors for all angiosperm chorotypes,
except for the Greek endemics and the SIEs (Table 2; Figure 4). MSL area
loss had an insignificant negative effect on SIE richness patterns
(Table 2; Figure 4).

\textbf{Discussion}

\emph{Species richness patterns}

Late Quaternary sea-level changes have left their mark on island species
richness patterns (e.g. Weigelt et al. 2016, Norder et al. 2019),
following theoretical expectations (Fernández-Palacios et al. 2015).
Recently, the question arose whether LGM paleogeographical
configurations or those more representative of the Pleistocene better
explain endemic species richness (Norder et al. 2019). It seems that on
oceanic islands the intermediate sea-level configuration shapes SIE and
MIE diversity patterns (Norder et al. 2019). Our study aimed to
investigate the possibility that different patterns might be observed on
continental islands, which have not been investigated with regard to
these questions so far.

Our power-function model had high predictive capacity (Table 2) and our
results are in line with Kreft et al. (2008), as well as the with values
reported for several Greek island phytogeographical regions (e.g.
Kagiampaki et al. 2011, Kougioumoutzis and Tiniakou 2014, Valli et al.
2019: 82--95\%). Our results corroborate H\textsubscript{1} and
H\textsubscript{2}: land-bridge islands host more native non-endemic
taxa, yet significantly fewer endemics (Figure 3). This pattern is also
reflected in ISAR z-values (Table 1; Appendix 3). The overall angiosperm
z-value (z = 0.329) falls within the range for continental shelf
settings (Triantis et al. 2012) and is similar to that of the East
Aegean islands (z = 0.326; Panitsa et al. 2010), which are land-bridge
islands. Aegean land-bridge islands host significantly more native taxa
and fewer endemics than true islands, thus implying that the former were
probably supersaturated in native taxa, after sea levels dropped. This
could result from the high geospatial connectivity states prevailing
during the Quaternary glacial sea-level low-stand periods, promoting
continuous influx of native taxa (e.g., Panitsa et al. 2018). These
biota are currently experiencing a relaxation period and have not
reached equilibrium (Simaiakis et al. 2017), a pattern reflected on
their endemic ISARs as well (low R\textsuperscript{2} values -- Table
1). The opposite trend is observed for all the endemic chorotypes --
being more pronounced for SIEs - as the ISAR slope is steeper for the
true islands (Appendix 3), confirming H\textsubscript{2}. Nevertheless,
the SIEs ISAR slope is significantly lower than reported from oceanic
islands (z = 0.8; Triantis et al. 2008), pointing to a state of endemic
underrepresentation on continental islands. The frequent reconnections
with the mainland during the glacial-interglacial cycles, enabled gene
flow between previously isolated insular and continental source
populations repeatedly re-established, thus hampering speciation and
consequently leading to lower endemism levels and species numbers
(Whittaker and Fernández-Palacios 2007).

\emph{Intermediate Pleistocene configurations and island fragmentation}

The long-lasting MSL configuration does not seem to have shaped
continental island species richness patterns (H\textsubscript{3}). LGM
configuration on the other hand, emerged as a major predictor for both
native and endemic species richness (Figure 4). The maximum, yet
short-lasting connectivity achieved during the LGM (Figure 2;
Sakellariou and Galanidou 2016) has negatively affected endemic
diversity (except SIEs), suggesting that the LGM spatial configuration
of the Aegean archipelago has left its imprint on species' distribution,
richness and evolutionary patterns (e.g., Poulakakis et al. 2015,
Kougioumoutzis et al. 2017). Quaternary fragmentation, as well as the
repeated and rapid paleo-islands fragmentation due to sea-level
oscillations during 20-11 Ka may be responsible for the observed
continental MIE patterns, apart from the dramatic island area-loss since
the LGM (\textgreater{} 70\%). This process affects island species
richness irrespective of area, via passive dispersal.
Island-fragmentation seems more prominent on continental rather than on
oceanic MIEs. The contrast in high numbers of islands shared by
continental MIEs and the low number of islands shared by oceanic islands
MIEs can be simply explained by much lower numbers of paleo-islands in
oceanic island settings that became fragmented by Pleistocene sea-level
oscillations (Norder et al. 2018) compared to what we see in continental
settings (Simaiakis et al. 2017). As a result, Aegean MIEs had typically
a much larger distribution on larger pre-existing paleo-islands,
sometimes even reaching beyond the Quaternary (Rechinger 1943, Rechinger
and Rechinger-Moser 1951, Runemark 1969, 1971, Greuter 1971, Snogerup
1971, Strid 1972). This may indicate that Aegean MIEs may have a
pre-Tertiary imprint of the paleogeography, when the sea level was as
high as during the Quaternary interglacials and these land-bridge
islands were true islands. Those paleo-islands fragmented earlier than
the Quaternary by geological processes over millions of years
(Creutzburg 1966, Dermitzakis 1990). For instance, pre-Pleistocene
paleo-connections existed between the (Pleistocene) true islands
Kythira, Crete, Karpathos and Rodos (Dermitzakis 1990, Schüle 1993) or
between the south-central Cyclades and Kriti (Kapsimalis et al. 2009,
Sakellariou and Galanidou 2016). Pleistocene sea-level oscillations
further fragmented the geologically earlier fragmented populations even
more, as for instance on the Cyclades (Simaiakis et al. 2017). Both
geological pre-Pleistocene breaking up of islands and Pleistocene
sea-level rise induced island fragmentation led to the fragmentation of
paleo-endemics that perhaps once were single island endemics on larger
pre-existing islands. In topographically complex islands, some of the
old MIEs probably gave rise to mostly neo-endemic SIEs through
allopatric speciation (e.g. Runemark 1969, 1971, Bittkau and Comes 2009,
Jaros et al. 2018). For these reasons, the usual classification of
endemics into SIEs or MIEs would make little sense in a
continental-shelf system that is both fragmented by regionally different
geological events and Pleistocene sea-level oscillations and where
dispersal distances between islands are short and past land-connections
were frequent. This highlights the importance of working with subsets of
species data that reflect the common evolutionary history of the species
included.

Continental SIEs however, are unaffected by past configurations (Table
2; Figure 4), contrary to oceanic SIEs which are driven by MSL
configurations (Norder et al. 2019). Oceanic island speciation and
endemism are elevated due to the MSL long-lasting, large island size
(Norder et al. 2019). Meanwhile, on continental islands large island
size was achieved during the LGM as a result of maximum connectivity.
This enabled increased gene-flow, thus leading to lower speciation and
endemism levels (e.g. Panitsa et al. 2018 and references therein). Most
Aegean SIEs occur on Crete and then on 25 other islands, most of them
(18 islands) containing only one SIE. Plant diversification and
speciation in the Aegean is mainly driven by random genetic drift
(Georghiou and Delipetrou 2010 and references therein) and active
species differentiation took place inside numerous islands (Cardona and
Cotandriopoulos 1978). Several Aegean endemics occupy precipitous
limestone cliffs, which are remnants of mountaintops that were most
pronounced during the LGM, when sea levels were up to 140 m lower. These
cliffs were virtually inaccessible even to the dominant components of
cliff communities in the adjacent mainland regions (e.g., \emph{Inula
verbascifolia} group and \emph{Campanula}
subsect.\emph{Quinqueloculares} ) and served as refugia during the
Quaternary glaciations, leading to high genetic differentiation and
systematic isolation (e.g., \emph{Linum arboreum} -- Thomson 2005). Only
three islands host more than 10 SIEs: Evvia, Samos and Samothraki, which
all were land-bridge islands since LGM; Samos was a land-bridge island
also during median sea levels. These three islands are mountainous and
topographically most pronounced, suggesting that topography plays an
additional important role in SIE formation and ecological isolation
might have driven speciation (e.g. Kallimanis et al. 2010, Trigas et al.
2013, Steinbauer et al. 2013, 2016). The topographic complexity and
geodiversity of these islands may also explain the ISAR SIE pattern. The
large number of SIEs occurring in Crete is due to its large size, long
isolation, high topographical and environmental heterogeneity, as well
as its paleogeographical history (Greuter 1972, 1975, Kagiampaki et al.
2011, Médail 2017).

\emph{Centipede diversity}

The remarkably low z-value (\textless{}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 H\textsubscript{2}, namely that endemism is demoted
on land-bridge islands. For native centipedes, higher z-values and
R\textsuperscript{2} 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.
\emph{Pachymerium ferrugineum} , \emph{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.

\emph{Biogeographical affinity}

Biogeographical affinity (i.e., the random effect in our models)
explained only a small fraction of the variance for the native taxa.
This can be attributed to the fact that a large portion
(\textasciitilde{}40\%) of the present Aegean flora has reached the
Aegean islands as a result of human action in prehistoric or early
historic times (Greuter 1979). The presence of these naturally or
artificially distance-insensitive species clearly justifies the less
significant role of biogeographical affinity in the diversity patterns
of the native plant taxa occurring in the Aegean archipelago. On the
other hand, the largest proportion of variance for all the endemic
species richness metrics is attributed to biogeographical affinity. This
is in line with previous studies stating that in the Aegean,
bioregionalization is primarily a result of the region's complex
paleogeographical history (Kougioumoutzis et al. 2017) This is also due
the high proportion of narrowly-ranged species and consequently of high
species turnover in Aegean island plant communities: nearly
\textasciitilde{}45\% of the endemic taxa occurring in the Aegean are
SIEs, the vast majority of which occur in Crete and Evvia (Panitsa et
al. 2018). Other factors such as climate and geodiversity probably play
an important role in shaping current endemic diversity patterns in the
Aegean, as is actually the case for the central (Kougioumoutzis and
Tiniakou 2014), eastern (Panitsa et al. 2010, Panitsa and Tzanoudakis
2010) and southern (Kagiampaki et al. 2011) Aegean islands. In addition,
favourable climatic conditions most probably permitted a relict flora to
persist in the southern (i.e., Crete, Karpathos, Rodos) and eastern
(e.g., Ikaria: Christodoulakis 1996a, b) Aegean archipelago (Runemark
1969, 1971). In topographically complex islands, some of the old MIEs
formed neo-endemic SIEs through allopatric speciation (Runemark 1969,
1971, Bittkau and Comes 2005, 2009, Comes et al. 2008, Jaros et al.
2018). Geographical isolation through sea-level oscillations may have
supported the recent diversification of neo-endemic species, especially
in the central Aegean where several non-adaptive radiations occurred
(e.g. \emph{Campanula} , \emph{Nigella} , \emph{Erysimum} -- e.g. Comes
et al. 2008, Jaros et al. 2018), as a result of a turbulent and
labyrinthine sequence of island-splitting events in a short time-period,
since most of the geographic configuration change occurred during marine
transgression in the Aegean within 5000 years between 16 and 11 Ka BP
(Simaiakis et al. 2017). Especially when considering the repetitive
character of fragmentation over the last 2 My, the fragmented and
disconnected state existed during every glacial-interglacial interval
for \textasciitilde{}20 ka disrupting the longer lasting glacially
connected state, leading to cumulative genetic divergence between
populations (Aguilée et al. 2009). One prominent example for this is the
differentiation of the \emph{Nigella arvensis} species complex which is
due to non-adaptive radiation and random genetic drift as a result of
several vicariant events during the Pliocene/Pleistocene (Bittkau and
Comes 2005, Bittkau and Comes 2009).

\emph{Continental-shelf and oceanic archipelagos}

The geographical setting of the LGM is an extreme configuration that was
represented only sporadically and for short time-periods throughout the
Pleistocene, with only 2\% of the last 800 Ka BP estimated to have a
similarly low sea level (Norder et al. 2019). Therefore, the duration of
these episodes may have been too short to have had a significant impact
on the diversity and composition of insular biota on oceanic islands
(Porter 1989, Heaney et al. 2013, Norder et al. 2019). Our results show
however, that in a continental-shelf archipelago, most of the Aegean
angiosperm endemic richness patterns are best explained by LGM
configurations, and the richness of native non-endemic angiosperm
species and to a lesser extent, centipedes still shows an impact of the
same configuration. We explain this as the result of extreme
connectivity that was achieved during the LGM between the expanded
Aegean true islands, land-bridge islands and the surrounding continental
land mass. This connectivity with the mainland, even though
short-lasting, promoted both conditions of native supersaturation on
islands that were once connected to the mainland and conditions of lower
endemism levels in the Aegean island biota. The \selectlanguage{greek}Ι\selectlanguage{english}SAR z-values for total
angiosperm richness fall into the z-value range for continental island
settings. On the other hand, the endemic richness z-values are much
lower than those on oceanic islands, pointing to reduced endemism on
continental islands. The mean adjusted species richness of natives on
land-bridge islands point to oversaturation of natives on land-bridge
islands. We also observed that the high degree of Aegean island
fragmentation by Pleistocene sea-level oscillations led to MIEs sharing
much more islands (\textgreater{} 5) than is observed for oceanic
archipelagos. The multiple island angiosperm endemism manifest in the
Aegean today is indeed largely shaped by the fragmentation of large
landmasses into smaller islands by the present high sea level. Lastly,
we noted that deep time pre Quaternary geological island fragmentation
left a distinct signature on endemism. Native species supersaturation
and reduced endemism are thus essential processes that distinguish
continental and oceanic island from the perspective of historical
biogeography. It remains to be tested in how far maximum connectivity
conditions are exclusively related to the lowest short-lasting sea-level
stand, or whether for most biota maximum connectivity was reached
earlier and lasted longer than the LGM. Clearly this depends on the
geometry and depth of the basin under study, influencing the sea-level
thresholds at which island area and connectedness change significantly
(Norder et al. 2019). We can conclude there is a crucial difference
between oceanic and continental islands: the rate of area loss, as well
as the degree of fragmentation, is far greater in continental islands
and as such, the recent sea-level changes might have influenced more
intensely their biota mediated through increased connectivity with the
nearby mainland during marine low-stands. Moreover, speciation as a
result of isolation and ecological speciation (through vacant niche
space) is the main driver of species richness on oceanic islands, in
contrast to continental islands where supersaturation and species
disequilibria due to greater extinction debt are seen as prevalent.
Single island endemism is generally supressed on continental islands,
and when endemism does manifest, it is then the result of higher
variability in topography or geodiversity offered by the continental
islands (e.g. Panitsa et al. 2010).

\textbf{Conclusions}

The Aegean continental islands were separated from the mainland for a
very long period of time (\textgreater{}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.

\textbf{Declarations}

The authors declare no conflicts of interest. CH was partially funded by
a FWO research grant (ref. 11C5219N) during this work. SJN received
funding from the Portuguese National Funds, through Funda\selectlanguage{ngerman}ção para a
Ciência e a Tecnologia (FCT), within the project UID/BIA/00329/2013 and
the Research Fellowship PD/BD/114380/2016.

\textbf{Data Accessibility Statement}

All relevant GIS files, species matrixes and R scripts will be made
available using Dryad data repository.

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\textbf{Tables.}

Table 1. Log\textsubscript{10}-transformed species area curve parameters
with mean z-values (slope) and correlation coefficients. S is all
species, N is native species, SIEs is single island endemics, MIEs is
Multiple island endemics (= PR+A), G is Greek island endemics, PE is
phytoregion endemics, AE is Aegean endemics.\selectlanguage{english}
\begin{longtable}[]{@{}lllllllll@{}}
\toprule
\textbf{Angiosperms} & \textbf{z-values} & \textbf{z-values} &
\textbf{z-values} & \textbf{R\textsuperscript{2}} &
\textbf{R\textsuperscript{2}} & \textbf{R\textsuperscript{2}} &
\textbf{R\textsuperscript{2}} &
\textbf{R\textsuperscript{2}}\tabularnewline
\midrule
\endhead
& Land-bridge islands & True Islands & Both Islands & Land-bridge
islands & Land-bridge islands & True Islands & Both Islands & Both
Islands\tabularnewline
S & 0.299*** & 0.328*** & 0.329*** & 0.728 & 0.796 & 0.796 & 0.796 &
0.801\tabularnewline
N & 0.299*** & 0.326*** & 0.331*** & 0.729 & 0.779 & 0.779 & 0.779 &
0.788\tabularnewline
SIEs & 0.298* & 0.367*** & 0.338*** & 0.204 & 0.447 & 0.447 & 0.447 &
0.394\tabularnewline
MIEs & 0.187 & 0.245*** & 0.137* & 0.034 & 0.290 & 0.290 & 0.290 &
0.048\tabularnewline
G & 0.380* & 0.334*** & 0.298*** & 0.224 & 0.520 & 0.520 & 0.520 &
0.329\tabularnewline
PE & 0.253* & 0.214*** & 0.136* & 0.157 & 0.184 & 0.184 & 0.184 &
0.048\tabularnewline
AE & 0.131 & 0.253*** & 0.141* & -0.007 & 0.330 & 0.330 & 0.330 &
0.059\tabularnewline
All-E & 0.353* & 0.319*** & 0.256*** & 0.256 & 0.507 & 0.507 & 0.507 &
0.248\tabularnewline
\textbf{Centipedes} & Land-bridge islands & True Islands & Both Islands
& Land-bridge islands & True Islands & True Islands & True Islands &
Both Islands\tabularnewline
S & -0.034 & 0.157*** & 0.134*** & -0.109 & 0.362 & 0.362 & 0.362 &
0.252\tabularnewline
N & -0.034 & 0.176*** & 0.15*** & -0.109 & 0.368 & 0.368 & 0.368 &
0.259\tabularnewline
All-E & NA & 0.003 & 0.004 & NA & -0.022 & -0.022 & -0.022 &
-0.018\tabularnewline
\bottomrule
\end{longtable}

\textbf{Hosted file}

\verb`image1.emf`  available at \url{https://authorea.com/users/314450/articles/444809-extreme-and-short-lasting-sea-level-stands-structure-insular-species-diversity-of-a-continental-shelf-archipelago-aegean-sea-greece}

Table 2: Selected GLMM models for each chorotype with overall best
performance in bold. Model performance was assessed based on AICc, BIC,
R\textsuperscript{2}m, R\textsuperscript{2}c and loocv
pseudo-R\textsuperscript{2}. In each of these models, variables with
p-values higher than 0.1 or VIF higher than 2.5 were removed. Meaning of
model variables: \emph{S-A} = spatial autocorrelation; \emph{prov} =
phytogeographical province; \emph{logApr} = logarithm of current
area;\emph{Dpr} = current shortest distance to the mainland;
\emph{dDmed} = increase in distance to the mainland compared to median
sea level;\emph{dAmed} = insular area loss compared to median sea
level;\emph{typemed} = island type (land-bridge island or true island)
based on median sea level; \emph{dDlgm} = increase in distance to the
mainland compared to LGM sea level; \emph{dAlgm} = insular area loss
compared to LGM sea level; \emph{typelgm} = island type based on LGM sea
level.

Supplementary Materials

\emph{Appendix 1}

In this earlier work, the Aegean archipelago was reconstructed based on
a geophysical model of relative sea-level change that uses generalized
sea-level equations accounting for hydro isostatic adjustments and
applied on a topographic and bathymetric grid with a resolution of 30
arc-seconds (Simaiakis et al. 2017). For the median value we took a
global eustatic median sea-level stand of 65 m below present for last
nine glacial-interglacial cycles (Norder et al. 2019). We assumed that
the regional geophysical effects affecting for this eustatic median
sea-level stand were minimal and comparable by the post glacial
sea-level rise conditions at 11 ka BP when this sea level was achieved
lastly. Islands smaller than the surface of a grid cell
(\textasciitilde{}1 km\textsuperscript{2}) were excluded from the
analysis, and islands separated by a distance smaller than the grid size
(\textasciitilde{}1 km\textsuperscript{2}) were aggregated in the
paleogeographic reconstruction to obtain a conservative estimate of the
fragmentation dynamics occurring in the system (see Rijsdijk et al.
2014). All geographical data were processed in ArcGIS 10.2.2. Past and
present areas and distance to the mainland were used to calculate the
magnitude of geographical change caused by sea-level rise (difference
between current and past values). For land-bridge islands (distance = 0
at Median sea level or Late Glacial Maximum), the area considered is
that of the island at the time step (1 Kya) preceding the connection to
the mainland (see Appendix S1 in Kougioumoutzis et al. 2017).

\emph{Appendix 2}Table A2.1

Current and past insular area and distance to the mainland.\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
Island & Current area (km\textsuperscript{2}) & Area at MSL
(km\textsuperscript{2}) & Area at LGM (km\textsuperscript{2}) & Current
distance to mainland (km) & MSL distance to mainland (km) & LGM distance
to mainland (km)\tabularnewline
\midrule
\endhead
\emph{Agathonisi} & 13..44 & 36.39 & 54.13 & 17.89 & 13.00 &
0.00\tabularnewline
\emph{Agios Efstratios} & 42.02 & 74.41 & 233.17 & 82.98 & 79.20 &
0.00\tabularnewline
\emph{Aigina} & 84.22 & 210.65 & 359.54 & 6.71 & 4.12 &
0.00\tabularnewline
\emph{Alatonisi} & 1.83 & 1.83 & 8.97 & 53.45 & 21.21 &
2.24\tabularnewline
\emph{Alimia} & 7.47 & 12.47 & 105.01 & 37.44 & 38.01 &
35.85\tabularnewline
\emph{Alonnisos} & 113.08 & 123.85 & 372.58 & 40.82 & 27.00 &
0.00\tabularnewline
\emph{Amorgos} & 121.33 & 179.61 & 295.05 & 105.38 & 76.49 &
49.82\tabularnewline
\emph{Anafi} & 38.52 & 80.45 & 258.77 & 140.13 & 101.64 &
93.48\tabularnewline
\emph{Andros} & 441.78 & 734.17 & 7616.97 & 12.08 & 10.77 &
5.39\tabularnewline
\emph{Antikythira} & 19.68 & 34.00 & 161.09 & 59.54 & 58.25 &
38.21\tabularnewline
\emph{Antimilos} & 8.81 & 15.98 & 23.48 & 92.85 & 92.10 &
77.00\tabularnewline
\emph{Antiparos} & 61.69 & 966.62 & 7616.97 & 110.54 & 105.95 &
5.39\tabularnewline
\emph{Astypalaia} & 95.87 & 182.34 & 360.01 & 80.23 & 40.80 &
33.62\tabularnewline
\emph{Chalki} & 27.20 & 43.15 & 105.01 & 45.12 & 45.12 &
35.85\tabularnewline
\emph{Chios} & 843.92 & 952.13 & 952.13 & 7.07 & 0.00 &
0.00\tabularnewline
\emph{Dia} & 11.88 & 20.04 & 39.61 & 210.95 & 203.67 &
200.11\tabularnewline
\emph{Donoussa} & 13.66 & 29.05 & 7616.97 & 118.34 & 89.83 &
5.39\tabularnewline
\emph{Dragonada} & 2.87 & 16.35 & 31.17 & 181.96 & 159.31 &
158.82\tabularnewline
\emph{Elasa} & 4.04 & 6.35 & 10906.46 & 180.85 & 163.17 &
87.24\tabularnewline
\emph{Fokionisi Megalo} & 1.59 & 182.34 & 360.01 & 89.89 & 40.80 &
33.62\tabularnewline
\emph{Folegandros} & 32.35 & 54.43 & 7616.97 & 131.47 & 127.42 &
5.39\tabularnewline
\emph{Gavdopoula} & 1.77 & 7.58 & 358.21 & 180.94 & 180.55 &
169.16\tabularnewline
\emph{Gavdos} & 32.72 & 67.60 & 358.21 & 191.09 & 187.54 &
169.16\tabularnewline
\emph{Gioura} & 11.05 & 21.64 & 178.07 & 59.48 & 57.58 &
3.61\tabularnewline
\emph{Gyali} & 8.42 & 12.69 & 27.02 & 19.10 & 8.25 & 6.32\tabularnewline
\emph{Gyaros} & 17.55 & 34.24 & 7616.97 & 38.95 & 38.01 &
5.39\tabularnewline
\emph{Ikaria} & 254.68 & 327.96 & 504.25 & 50.70 & 18.25 &
0.00\tabularnewline
\emph{Ios} & 108.45 & 160.75 & 7616.97 & 145.01 & 134.00 &
5.39\tabularnewline
\emph{Irakleia} & 18.12 & 33.21 & 7616.97 & 146.01 & 127.19 &
5.39\tabularnewline
\emph{Kalymnos} & 248.26 & 272.57 & 293.03 & 16.49 & 4.00 &
0.00\tabularnewline
\emph{Kandelioussa} & 3.28 & 3.28 & 7.27 & 38.59 & 17.03 &
16.03\tabularnewline
\emph{Karpathos} & 393.83 & 471.05 & 831.28 & 85.15 & 85.15 &
84.53\tabularnewline
\emph{Kasos} & 66.71 & 149.74 & 831.28 & 140.94 & 135.00 &
84.53\tabularnewline
\emph{Kastellorizo} & 15.13 & 15.13 & 16.56 & 3.00 & 2.83 &
0.00\tabularnewline
\emph{Kea} & 130.38 & 166.65 & 239.21 & 19.65 & 13.60 &
0.00\tabularnewline
\emph{Keros} & 15.09 & 30.34 & 7616.97 & 138.45 & 109.66 &
5.39\tabularnewline
\emph{Kimolos} & 48.66 & 344.91 & 710.79 & 101.07 & 97.58 &
73.98\tabularnewline
\emph{Kinaros} & 4.56 & 9.21 & 63.78 & 82.39 & 59.51 &
23.85\tabularnewline
\emph{Kithnos} & 99.43 & 138.82 & 229.74 & 37.64 & 32.53 &
5.39\tabularnewline
\emph{Kos} & 288.10 & 438.91 & 438.91 & 7.00 & 0.00 &
0.00\tabularnewline
\emph{Koufonisi} & 4.18 & 21.04 & 10906.46 & 221.47 & 203.08 &
87.24\tabularnewline
\emph{Kounoupoi} & 3.98 & 182.34 & 360.01 & 80.52 & 40.80 &
33.62\tabularnewline
\emph{Koutsomytis} & 1.51 & 182.34 & 360.01 & 82.76 & 40.80 &
33.62\tabularnewline
\emph{Kriti} & 8264.62 & 9208.39 & 10906.46 & 95.08 & 93.98 &
87.24\tabularnewline
\emph{Kyra Panagia} & 24.76 & 38.34 & 178.07 & 62.37 & 47.13 &
3.61\tabularnewline
\emph{Kythira} & 277.23 & 365.72 & 646.13 & 13.45 & 7.07 &
6.00\tabularnewline
\emph{Leipsoi} & 15.87 & 46.91 & 118.79 & 36.67 & 32.39 &
0.00\tabularnewline
\emph{Lesvos} & 1636.73 & 2007.52 & 2007.52 & 9.00 & 7.81 &
0.00\tabularnewline
\emph{Levitha} & 9.12 & 19.98 & 63.78 & 65.28 & 46.40 &
23.85\tabularnewline
\emph{Limnos} & 477.03 & 879.62 & 1794.26 & 58.24 & 26.25 &
0.00\tabularnewline
\emph{Milos} & 196.57 & 344.91 & 710.79 & 103.37 & 97.58 &
73.98\tabularnewline
\emph{Mykonos} & 85.80 & 144.22 & 7616.97 & 86.05 & 84.63 &
5.39\tabularnewline
\emph{Naxos} & 430.17 & 966.62 & 7616.97 & 120.25 & 105.95 &
5.39\tabularnewline
\emph{Nisyros} & 41.28 & 55.84 & 76.27 & 16.64 & 15.23 &
13.34\tabularnewline
\emph{Ofidousa} & 3.79 & 5.78 & 360.01 & 109.12 & 69.64 &
33.62\tabularnewline
\emph{Paros} & 238.19 & 966.62 & 7616.97 & 107.62 & 105.95 &
5.39\tabularnewline
\emph{Patmos} & 34.22 & 67.88 & 104.40 & 48.80 & 33.00 &
0.00\tabularnewline
\emph{Paximada} & 1.53 & 16.35 & 31.17 & 179.49 & 159.31 &
158.82\tabularnewline
\emph{Polyaigos} & 18.12 & 344.91 & 710.79 & 109.18 & 97.58 &
73.98\tabularnewline
\emph{Pontikousa} & 2.43 & 4.03 & 360.01 & 102.42 & 62.36 &
33.62\tabularnewline
\emph{Psara} & 40.04 & 75.04 & 173.51 & 61.27 & 19.00 &
12.00\tabularnewline
\emph{Pserimos} & 14.63 & 438.91 & 438.91 & 8.06 & 0.00 &
0.00\tabularnewline
\emph{Rineia} & 14.06 & 50.46 & 7616.97 & 83.44 & 82.07 &
5.39\tabularnewline
\emph{Ro} & 2.60 & 4.27 & 22.01 & 5.00 & 5.00 & 0.00\tabularnewline
\emph{Rodos} & 1407.68 & 1615.73 & 1982.09 & 18.03 & 17.09 &
13.93\tabularnewline
\emph{Samothraki} & 180.51 & 225.11 & 250.23 & 35.36 & 29.07 &
0.00\tabularnewline
\emph{Schoinousa} & 8.13 & 56.13 & 7616.97 & 146.82 & 116.40 &
5.39\tabularnewline
\emph{Serifos} & 74.09 & 102.86 & 176.48 & 62.80 & 58.52 &
34.01\tabularnewline
\emph{Sifnos} & 77.38 & 110.49 & 161.28 & 86.83 & 82.42 &
57.71\tabularnewline
\emph{Sikinos} & 41.74 & 72.12 & 7616.97 & 142.27 & 137.54 &
5.39\tabularnewline
\emph{Skantzoura} & 6.23 & 15.31 & 31.55 & 59.55 & 42.05 &
8.06\tabularnewline
\emph{Skiathos} & 47.33 & 72.32 & 72.32 & 4.12 & 0.00 &
0.00\tabularnewline
\emph{Skopelos} & 125.96 & 141.33 & 372.58 & 22.00 & 6.08 &
0.00\tabularnewline
\emph{Skyropoula} & 6.05 & 6.29 & 38.89 & 26.17 & 26.17 &
26.17\tabularnewline
\emph{Skyros} & 206.93 & 317.85 & 586.30 & 33.62 & 34.13 &
30.41\tabularnewline
\emph{Stroggyli} & 3.50 & 3.50 & 4.80 & 1.41 & 1.41 &
0.00\tabularnewline
\emph{Symi} & 58.00 & 102.60 & 125.78 & 8.00 & 8.00 &
5.00\tabularnewline
\emph{Syrna} & 7.94 & 14.48 & 40.87 & 70.46 & 41.62 &
38.47\tabularnewline
\emph{Syros} & 83.78 & 127.92 & 7616.97 & 58.82 & 57.43 &
5.39\tabularnewline
\emph{Thasos} & 383.75 & 472.28 & 472.28 & 8.00 & 0.00 &
0.00\tabularnewline
\emph{Thira} & 75.74 & 123.10 & 252.44 & 169.92 & 130.77 &
120.33\tabularnewline
\emph{Tilos} & 61.83 & 99.55 & 134.76 & 21.02 & 20.40 &
20.62\tabularnewline
\emph{Tinos} & 233.43 & 734.17 & 7616.97 & 50.93 & 10.77 &
5.39\tabularnewline
\emph{Ydra} & 49.75 & 82.36 & 82.36 & 2.83 & 2.83 & 0.00\tabularnewline
Average & \textbf{223} & \textbf{329} & \textbf{2104} & \textbf{74} &
\textbf{61} & \textbf{31}\tabularnewline
\bottomrule
\end{longtable}

Table A2.2

Distribution of island type at Median and Late Glacial Maximum sea
levels (MSL and LGM, respectively), including the islands of both the
angiosperms and centipedes datasets (n = 84).\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
& Sea level & Sea level\tabularnewline
\midrule
\endhead
& MSL & LGM\tabularnewline
Land-bridge & 5 & 22\tabularnewline
True island & 79 & 62\tabularnewline
\bottomrule
\end{longtable}

\emph{Appendix 3:}

Species-area relationships for selected chorotypes of angiosperms on
land-bridge islands and true islands. In blue dots the data points and
regression lines for land-bridge islands, in green triangles the true
islands. NNE stands for `native non endemics'; EAll for `all endemics';
AE for `Aegean endemics'; SIEs for `single island endemics'; GE for
`Greek endemics' and; MIEs for `multiple island endemics'.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure1/Figure1}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure2/Figure2}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure3/Figure3}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure4/Figure4}

\end{center}
\end{figure}

\selectlanguage{english}
\FloatBarrier
\end{document}

