The diverse nature of island isolation and its effect on land bridge insular faunas

Aim: Isolation is a key factor in island biology. It is usually defined as the distance to the geographically nearest mainland, but many other definitions exist. We explored how testing different isolation indices affects the inference of impacts of isolation on faunal characteristics. We focused on land bridge islands and compared the relationships of many 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: Many 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 ordinary least squares regressions (controlling for island area when needed) and a meta‐analysis. Results: Isolation was significantly (and negatively) associated with species richness in 10 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 that of island area, regardless of the index tested. Spatial indices generally out‐performed temporal indices, and indices directly related to the mainland out‐performed 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 impacts of isolation on biological patterns. The nearly automatic, ubiquitous use of distance to the geographically nearest mainland misrepresents the complexity of the effects of isolation. We recommend the simultaneous testing of several indices that represent different aspects of isolation, in order to produce more constructive and thorough investigations and avoid imprecise inference

Tackling the lionfish invasion in the Mediterranean. the EU-LIFE RELIONMED Project: progress and results

The lionfish invasion in the Western Atlantic has been characterised as one of the most ecologically harmful marine fish introductions to date; associated with habitat modifications, and severe impacts on native communities. In the Mediterranean, lionfish followed similar expansion trends and raised significant concerns among the scientific community due to its potential to cause devastating ecological and socioeconomic impacts. The coastal ecosystems of Cyprus, near the Suez Canal, are amongst the first Mediterranean waters to be affected by the lionfish invasion. Cyprus sentinel location offers therefore, an ideal site for the development of an early warning and rapid response system of marine bioinvasions. RELIONMED (Preventing a LIONfish invasion in the MEDiterranean through early response and targeted REmoval) is a four-year project, funded by the EU LIFE instrument, aiming to make Cyprus the first line of defence against the invasion of lionfish in the Mediterranean. The project has started successfully on September 2017 with a number of early (preparatory) project actions including stakeholder consultation and baseline assessment of social awareness, biological analyses of a small lionfish sample, and the development of a lionfish risk assessment following the guidelines of the Regulation 1143/2014 to include the species in the EU IAS priority list. Forthcoming project’s actions strongly rely on citizen scientists’ and stakeholders’ participation and RELIONMED aims to develop the capacity and tools for control of lionfish, particularly in priority habitats. Preliminary results such as early maturity, high growth rates, generalist diet, and reproduction throughout the year indicate that lionfish can become a ferocious invader for the basin and RELIONMED calls for regional collaborations and coordinated management measures against lionfish invasion in the basin

Phylogeography of Aegean green toads (Bufo viridis subgroup): continental hybrid swarm vs. insular diversification with discovery of a new island endemic

BACKGROUND: Debated aspects in speciation research concern the amount of gene flow between incipient species under secondary contact and the modes by which post-zygotic isolation accumulates. Secondary contact zones of allopatric lineages, involving varying levels of divergence, provide natural settings for comparative studies, for which the Aegean (Eastern Mediterranean) geography offers unique scenarios. In Palearctic green toads (Bufo viridis subgroup or Bufotes), Plio-Pleistocene (~ 2.6 Mya) diverged species show a sharp transition without contemporary gene flow, while younger lineages, diverged in the Lower-Pleistocene (~ 1.9 Mya), admix over tens of kilometers. Here, we conducted a fine-scale multilocus phylogeographic analysis of continental and insular green toads from the Aegean, where a third pair of taxa, involving Mid-Pleistocene diverged (~ 1.5 Mya) mitochondrial lineages, earlier tentatively named viridis and variabilis, (co-)occurs. RESULTS: We discovered a new lineage, endemic to Naxos (Central Cyclades), while coastal islands and Crete feature weak genetic differentiation from the continent. In continental Greece, both lineages, viridis and variabilis, form a hybrid swarm, involving massive mitochondrial and nuclear admixture over hundreds of kilometers, without obvious selection against hybrids. CONCLUSIONS: The genetic signatures of insular Aegean toads appear governed by bathymetry and Quaternary sea level changes, resulting in long-term isolation (Central Cyclades: Naxos) and recent land-bridges (coastal islands). Conversely, Crete has been isolated since the end of the Messinian salinity crisis (5.3 My) and Cretan populations thus likely result from human-mediated colonization, at least since Antiquity, from Peloponnese and Anatolia. Comparisons of green toad hybrid zones support the idea that post-zygotic hybrid incompatibilities accumulate gradually over the genome. In this radiation, only one million years of divergence separate a scenario of complete reproductive isolation, from a secondary contact resulting in near panmixia

Can additive beta-diversity be reliably partitioned into nestedness and turnover components?

Aims: Quantifying β‐diversity (differences in the composition of communities) is central to many ecological studies. There are many β‐diversity metrics, falling mostly into two approaches: variance‐based (e.g., the Sørensen index), or diversity partitioning (e.g., additive β‐diversity). The former cannot be used when species–sites matrices are unavailable (which is often the case in island biogeography in particular) and only species richness data are provided. Recently, efforts have been made to partition additive β‐diversity, a metric calculated using only α‐diversity and γ‐diversity, into nestedness and turnover components (termed here “richness‐only β‐diversity partitioning”). We set out to test whether this form of β‐diversity partitioning generates interpretable results, comparable with metrics based on species incidence β‐diversity partitioning. Location: Global. Time period: Present day. Major taxa studied: Multiple taxa. Methods: We first provide a brief review of β‐diversity partitioning methods, with a particular focus on the development of richness‐only β‐diversity partitioning. Second, we use 254 empirical incidence matrices (provided with the paper) sourced from the literature to measure turnover and nestedness using incidence β‐diversity partitioning, comparing the resulting values with those calculated using richness‐only β‐diversity. Results: We provide an account of the emergence of β‐diversity partitioning, with particular reference to the analysis of richness‐only datasets, and to the definition and usage of the relevant metrics. Analytically, we report weak correlations between turnover and nestedness calculated using the two different approaches. We show that this is because identical values of α‐diversity and γ‐diversity can correspond to incidence matrices with a range of different structures. Main conclusions: Our results demonstrate that the use of richness‐only β‐diversity partitioning to measure turnover and nestedness is problematic and can produce patterns unrelated to conventional measures of turnover and nestedness. We therefore recommend that more accurate definitions are adopted for these terms in future studies.</br

Small-scale coexistence of two mouse lemur species (Microcebus berthae and M. murinus) within a homogeneous competitive environment

Understanding the co-occurrence of ecologically similar species remains a puzzling issue in community ecology. The species-rich mouse lemurs (Microcebus spec.) are distributed over nearly all remaining forest areas of Madagascar with a high variability in species distribution patterns. Locally, many congeneric species pairs seem to co-occur, but only little detailed information on spatial patterns is available. Here, we present the results of an intensive capture–mark–recapture study of sympatric Microcebus berthae and M. murinus populations that revealed small-scale mutual spatial exclusion. Nearest neighbour analysis indicated a spatial aggregation in Microcebus murinus but not in M. berthae. Although the diet of both species differed in proportions of food categories, they used the same food sources and had high feeding niche overlap. Also, forest structure related to the spatial distribution of main food sources did not explain spatial segregation because parts used by each species exclusively did not differ in density of trees, dead wood and lianas. We propose that life history trade-offs that result in species aggregation and a relative increase in the strength of intra-specific over inter-specific competition best explain the observed pattern of co-occurrence of ecologically similar congeneric Microcebus species

A biogeographical analysis of terrestrial isopods (Isopoda, Oniscidea) from the central Aegean islands (Greece)

Terrestrial isopods (Isopoda, Oniscidea) of forty-three central Aegean islands and islets are analysed from a biogeographical point of view. The oniscid fauna consists of sixty-nine species, thirty-two genera anti fourteen families anti is characterized by Aegean elements that have an eastern Mediterranean origin. Endemism is at the level of 20%, similar to that of oniscids from other Mediterranean archipelagoes. Analysis of species distribution through both idiographic and quantitative approaches (faunal similarity among islands using Jaccard&apos;s index, simple matching indices and the UPGMA clustering technique) resulted in the recognition of a major disjunction between Kyklades-plus-Ikaria and eastern islands-plus-Astypalca and four noteworthy island groups: the eastern islands, Naxos-Ikaria, Amorgos, and all other Kyklades. Island similarities are generally consistent with the known palaeogeography of the area with the exception of Ikaria&apos;s placement with Naxos among the Kyklades. Also, the &apos;eastern&apos; character of Astypalea is in conflict with evidence from other known taxa

Altitudinal effect on species richness of Oniscidea (Crustacea; Isopoda) on three mountains in Greece

Species richness decreases with altitude, and at the same rate on all three mountains. The faunal similarity among altitudinal zones is inversely related to species density (total number of species present at each mountain), but is not related to latitude. Species density is constrained by environmental harshness, but is also influenced by historical factors. -from Autho

TERRESTRIAL ISOPODS (CRUSTACEA, ONISCIDEA) FROM THE REMOTE GREEK ISLAND ANTIKITHIRA AND ITS SURROUNDING ISLETS

Terrestrial isopods from the southwestern Aegean island group of Antikithira are recorded here for the first time. Collecting was done on three islands, Antikithira, Prassonisi and Lagouvardhos, and a total of 20 species was found. One of them is new for science and is described here. Finally, a biogeographic interpretation of the results is attempted

The species-area relationship of terrestrial isopods (Isopoda; Oniscidea) from the Aegean archipelago (Greece): A comparative study

Data on species richness of terrestrial isopods (Oniscidea) from central Aegean islands (Greece), together with previously published data sets from other taxa and areas, are critically analysed under the basic premises of ecological biogeography. Habitat diversity seems to be the most important determinant of species richness for Oniscidea, although the relation to area is also significant. Comparison with other data sets demonstrates that the best fit model of the species-area relationship is case-specific and usually not unique, since the assumptions for appropriate use of any particular model (logS/logA, S/A or S/logA) cannot be satisfied by all species richness data sets, and since confidence limits around regression coefficients are usually broad for the relatively limited sizes of island groups. The values of slopes and intercepts of the species-area regression lines seem to be statistical artefacts that encompass the effects of several intervening factors, such as the data set size and range, and should be checked accordingly before any biological statements about differences between taxa or island groups can be made