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Influence of Recent Geography and Paleogeography on the Structure of Reptile Communities in a Land-Bridge Archipelago Author(s): Simone Fattorini Source: Journal of Herpetology, 44(2):242-252. 2010. Published By: The Society for the Study of Amphibians and Reptiles DOI: 10.1670/09-046.1 URL: http://www.bioone.org/doi/full/10.1670/09-046.1 BioOne (www.bioone.org) is an electronic aggregator of bioscience research content, and the online home to over 160 journals and books published by not-for-profit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Journal of Herpetology, Vol. 44, No. 2, pp. 242–252, 2010 Copyright 2010 Society for the Study of Amphibians and Reptiles Influence of Recent Geography and Paleogeography on the Structure of Reptile Communities in a Land-Bridge Archipelago SIMONE FATTORINI Water Ecology Team, Department of Biotechnology and Biosciences, University of Milano Bicocca, Piazza della Scienza 2, I-20126, Milan, Italy; E-mail: [email protected] ABSTRACT.—The herpetofauna of the Tuscan Islands (Central Italy) is well known and represents an ideal subject to understand the role of current and historical factors responsible for biogeographical patterns in a complex archipelago. Multidimensional Scaling, cluster analyses, species-area relationships, Mantel tests and co-occurrence statistics were used to investigate the influence of current geography and Pleistocene connections with the mainland on the structure of insular communities. Although reptile colonization likely occurred via land bridges for islands that were connected to the mainland in the Pleistocene, a long time relaxation (species extinction by island habitat loss after disconnection and new colonization by over sea dispersal or human-assisted introductions) equilibrated the faunas according to island area. Biogeographical similarities among islands increased for islands located farther from Corsica and Tuscany, thus suggesting that, for remote islands, interisland faunal exchanges occurred more frequently than mainland-island colonization. Also, a possible influence of Pleistocene geography emerged more clearly when populations suspected to be introduced by man were removed. Co-occurrence analyses indicated a nonrandom distribution influenced by island area and distance, suggesting that the time elapsed since post-Pleistocene disconnection may have reshaped biogeographical similarities by an increase in competition resulting from reduction in island areas and introduction of certain species. From a conservation viewpoint, the land-bridge distribution of organisms with poor mobility should be carefully considered in conservation biogeography, because depletion of island populations cannot be balanced by new immigrations from the mainland, whereas introduction of nonnative species may have a negative impact on the original fauna. The biogeography of the Tuscan Islands from Tuscany. In fact, recent studies demon- (Fig. 1) has long been studied to highlight the strated that, at least in animals with high major ecological and historical factors that are mobility (such as chrysidid hymenopterans potentially responsible for present day distribu- and butterflies), a transitional pattern can be tional patterns, making this archipelago one of simply explained by current geography alone the best investigated in the Mediterranean Basin (Fattorini, 2009a). (e.g., Baroni Urbani, 1971; Societa` Italiana di Although for oceanic islands (i.e., islands Biogeografia, 1974; Piantelli et al., 1990; Fattor- never connected to the mainland) a general ini, 2009a). model has been recently proposed that takes Because of their location between the Corsar- into account island evolution through time dian plate (Corsica plus Sardinia) and Tuscany (Whittaker et al., 2008; Fattorini, 2009b), there region (Central Italy), the Tuscan Islands are is no comprehensive theory on the evolution of expected to show transitional faunas, and this land-bridge islands. According to the model has already been well demonstrated for several postulated by Fattorini (2009a) for the Tuscan groups (Fattorini, 2009a). The common opinion Islands, land-bridge islands were largely colo- is that paleogeography is a key factor in nized (and possibly saturated) by different determining the distribution of plants and groups during the Pleistocene sea regressions, animals on these islands, which have been and then there have been extensive extinctions regarded as a classical example of land-bridge as a result of area and, hence, habitat loss. islands (see references in Mariotti, 1990; Dap- However, although mobile animals were able to porto and Cini, 2007). According to this view, currently colonize virtually all islands, mostly islands that were connected to Tuscany during erasing the historical signal and resulting in a Pleistocene glacial maxima are characterized by negative correlation of species richness and a preponderance of species that reached the distance, even small distances preclude less Tuscan Islands from the Italian mainland, mobile groups such as tenebrionid coleopterans whereas islands closer to Corsardinia (but from colonizing an island regularly, such that which were isolated during Pleistocene glacial no correlation between species richness and maxima) exhibit a larger proportion of species distance appears in these insects (Fattorini, distributed in Corsica and Sardinia but absent 2009c). Thus, the role of dispersal should be REPTILE BIOGEOGRAPHY ON LAND-BRIDGE ISLANDS 243 FIG. 1. The Tuscan Archipelago and its relative position in the Mediterranean. Present day land (black) and extent of land mass during the last (Pleistocene) glacial maximum (dark grey) are indicated. Depth contours are also shown for 200 m (light grey). CAP: Capraia, ELB: Elba, GIA: Giannutri, GIG: Giglio, GOR: Gorgona, MON: Montecristo, MTA: Mt. Argentario, PIA: Pianosa. accurately considered for understanding the phy (Whittaker et al., 2005) stresses the impor- evolution of archipelagos that include land- tance of considering biogeographical informa- bridge islands. Compared with other groups, tion in assessing conservation priorities. Thus, reptiles are relatively less mobile; thus, their the understanding of the processes underlying island faunas tend to be usually relictual (e.g., reptile biogeographical patterns in the Tuscan Foufopoulos and Ives, 1999). Therefore, the Islands may serve as a case study to address reptiles of the Tuscan Islands may represent some general problems of biological conserva- an excellent model to investigate the role of tion in land-bridge archipelagos. current and historical factors in determining The aims of this paper were as follows: (1) to biogeographical patterns in a composite archi- investigate the biogeographical relationships of pelago, which includes both land-bridge and reptile faunas of the Tuscan Islands; (2) to oceanic islands. determine the relative importance of current The herpetofauna of the Tuscan Islands has (Recent) and historical (Pleistocene) geography been investigated by naturalists for more than a in determining such patterns; (3) to assess the century, and all of these islands are faunistically mechanisms that may explain the role of Recent well known (Balletto, 2005; Vanni and Nistri, and Pleistocene factors; and (4) to discuss some 2006). However, there is no detailed study implications for biodiversity conservation. aimed to understand the role of current and historical factors responsible for biogeographi- cal patterns. An analysis of the relative impor- MATERIALS AND METHODS tance of current and historical factors is partic- ularly compelling because of the conservation Data Sources.—The study islands included concern of these islands, which are included in Capraia, Gorgona, Montecristo, Elba, Pianosa, the Tuscan Archipelago National Park. The Giglio, Giannutri, and the fossil-island of Mt. recent development of conservation biogeogra- Argentario (Dapporto and Cini, 2007; Fig. 1). 244 S. FATTORINI TABLE 1. Reptile distribution in the Tuscan Archipelago. Presence/absence indicated by 1/0. Gorgona Capraia Elba Pianosa Giglio Montecristo Giannutri Mt. Argentario Tarantola mauritanica 1 111 1 0 1 1 Hemidactylus turcicus 1 111 1 1 1 1 Euleptes europaea 0 111 1 1 1 1 Lacerta bilineata 0 010 0 0 0 1 Podarcis sicula 0 111 1 1 1 1 Podarcis muralis 1 011 0 0 0 1 Chacides chalcides 0 010 0 0 0 1 Hierophis viridiflavus 1 111 1 1 1 1 Coronella austriaca 0 010 0 0 0 0 Zamenis longissimus 0 010 0 0 0 1 Elaphe quattorilineata 0 000 0 0 0 1 Natrix natrix 0 010 0 0 0 1 Vipera aspis francisciredi 0 010 0 0 0 1 Vipera aspis hugyi 0 000 0 1 0 0 Distributional data are taken from Fattorini (Elba, Portoferraio islet, Palmaiola, Scoglio della (2009a; Table 1). Field research was performed Paolina, fossil islands of Massoncello and Punta on Giglio and Giannutri in August 2008. Ala), Podarcis muralis insulanica