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                    OPEN        Historical and contemporary

                                factors generate unique butterfly

                                communities on islands

            Received: 20 January 2016  Raluca Vodă 1,2,* , Leonardo Dapporto 1,3,* , Vlad Dincă , Tim G. Shreeve , Mourad Khaldi ,
              Accepted: 31 May 2016  Ghania Barech , Khellaf Rebbas , Paul Sammut , Stefano Scalercio , Paul D. N. Hebert  &
             Published: 29 June 2016  Roger Vila 1
                                The mechanisms shaping island biotas are not yet well understood mostly because of a lack of studies
                                comparing eco-evolutionary fingerprints over entire taxonomic groups. Here, we linked community
                                structure (richness, frequency and nestedness) and genetic differentiation (based on mitochondrial
                                DNA) in order to compare insular butterfly communities occurring over a key intercontinental area
                                in the Mediterranean (Italy-Sicily-Maghreb). We found that community characteristics and genetic
                                structure were influenced by a combination of contemporary and historical factors, and among the
                                latter, connection during the Pleistocene had an important impact. We showed that species can
                                be divided into two groups with radically different properties: widespread taxa had high dispersal
                                capacity, a nested pattern of occurrence, and displayed little genetic structure, while rare species
                                were mainly characterized by low dispersal, high turnover and genetically differentiated populations.
                                These results offer an unprecedented view of the distinctive butterfly communities and of the main
                                processes determining them on each studied island and highlight the importance of assessing the
                                phylogeographic value of populations for conservation.

                                Island communities share several features: the number of species is lower than on similarly sized mainland areas
                                (impoverishment), they host a disproportionate fraction of non-predatory and highly dispersive species (dis-
                                harmony) and they are characterized by a high fraction of endemic elements . In the last decades it has been
                                largely recognized that these features are shaped by colonization and extinction events but also by the long-term
                                persistence of populations, resulting in relictuality and endemicity . In turn, these processes depend on a large
                                number of factors related to both species and island characteristics, as well as to stochastic events . As a result,
                                no island populations and communities are identical and they have been regarded as “individuals” . Hence, rec-
                                ognizing the main drivers behind the formation of each community and developing specific conservation plans
                                require in-depth comparative analyses linking community and genetic approaches .
                                   An important property of island communities is that their structure tends to be nested, with some species
                                occurring on most islands, and others occurring on fewer islands, usually the largest and least isolated 9,10 . The
                                existence of nested patterns has important implications for conservation; when communities are highly nested,
                                conservation decisions are simplified and the usual strategy is to concentrate efforts on the most diverse commu-
                                nities . After a series of studies suggested that nested structures universally occur within different taxa and island
                                systems , the recent introduction of strict null models revealed that significantly nested patterns are less common
                                than previously hypothesized . There is also a debate 6,13  as to whether species occurrence in island communities
                                is mostly determined by their frequency in neighbouring source areas, as postulated by neutral theories 2,14 , or
                                1 Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta 37, 08003,
                                Barcelona, Spain.  Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina
                                13, 10123 Turin, Italy.  Department of Biology, University of Florence, 50019 Florence, Italy.  Centre for Biodiversity
                                Genomics, Biodiversity Institute of Ontario, University of Guelph, Guelph, N1G 2W1, Ontario, Canada.  Department
                                of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, OX3 0BP, UK.  Département
                                d’Agronomie, Université Mohamed Boudiaf de M’sila, 28000 M’sila, Algeria.  Département des sciences de la nature
                                et de la vie, Université Mohamed Boudiaf de M’sila, 28000 M’sila, Algeria.  137, “Fawkner/2” Dingli Road, Rabat RBT
                                9023, Malta.  Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Unità di Ricerca per la Selvicoltura
                                in Ambiente Mediterraneo, c.da Li Rocchi, I-87036 Rende (CS), Italy.  These authors contributed equally to this work.
                                Correspondence and requests for materials should be addressed to R.Vila (email:
         Scientific RepoRts | 6:28828 | DOI: 10.1038/srep28828                                                 1
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