Satyrinae butterflies from Sardinia and Corsica show a kaleidoscopic intraspecific biogeography (Lepidoptera, Nymphlidae)

Biological Journal of the Linnean Society, 2010, 100, 195–212. With 6 figures Satyrinae butterflies from Sardinia and Corsica show a kaleidoscopic intraspecific biogeography (Lepidoptera, Nymphlidae) LEONARDO DAPPORTO* Received 6 November 2009; accepted for publication 16 December 2009 bij_1434 195..212 The Mediterranean islands of Sardinia and Corsica are known for their multitude of endemics. Butterflies in particular have received much attention. However, no comprehensive studies aiming to compare populations of butterflies from Sardinia and Corsica with those from the neighbouring mainland and Sicily have been carried out. In the present study, the eleven Satyrinae species inhabiting Sardinia and Corsica islands were examined and compared with continental and Sicilian populations by means of geometric morphometrics of male genitalia. Relative warp computation, discriminant analyses, hierarchical clustering, and cross-validation tests were used to identify coherent distributional patterns including both islands and mainland populations. The eleven species showed multifaceted distributional patterns, although three main conclusions can be drawn: (1) populations from North Africa and Spain are generally different from those belonging to the Italian Peninsula; (2) populations from Sardinia and Sicily often resemble the North Africa/Spain ones; Corsica shows transitional populations similar to those from France; and (3) sea barriers represent filters to dispersal, although their efficacy appears to be unrelated to their extension. Indeed, the short sea straits between Sardinia and Corsica and between Sicily and the Italian Peninsula revealed a strong effectiveness with respect to preventing faunal exchanges; populations giving onto sea channels between Corsica and Northern Italy and between Sicily and Tunisia showed a higher similarity. A comparison of island and mainland distributions of the eleven taxa have helped to unravel the complex co-occurrence of historical factors, refugial dynamics, and recent (post-glacial) dispersal with respect to shaping the populations of Mediterranean island butterflies. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 195–212. ADDITIONAL KEYWORDS: geometric morphometrics – glacial maxima – Mediterranean – refugia. INTRODUCTION Sardinia and Corsica, approximately located at the centre of the West Mediterranean sea, should be considered as fragment islands because they separated from southern Europe during the late Miocene (Meulenkamp & Sissingh, 2003). Generally, flying insect faunas on fragment islands are endemic poor because the relatively short distances to the mainland allow gene flow (Dennis & Shreeve, 1997; Dennis et al., 2000; Dapporto et al., 2009). Nevertheless, because of the occurrence of many endemic taxa, *E-mail: Sardinia and Corsica are considered to be among the most important biodiversity hotspots for butterflies in the Mediterranean (Grill et al., 2002; Kudrna, 2002; Balletto, Monelli & Cassulo, 2005; Dapporto & Dennis, 2009). Despite the large amount of attention received by Sardinia and Corsica Lepidoptera, their phylogeography and systematics are far from being understood. Indeed, relationships between insular and mainland taxa have been mainly assessed by subjective visual comparisons of external characteristics (generally the wing pattern) (Dennis, 1997; Kudrna, 2002; Balletto et al., 2005). Moreover, phylogeographic and biogeographic studies of Mediterranean butterflies have often focused either on island © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 195–212 195 Istituto Comprensivo Materna Elementere Media Convenevole da Prato via 1° Maggio 40, 59100, Prato, Italy 196 L. DAPPORTO neighbouring continental areas. Such an approach may reveal patterns of intraspecific similarities and the degree of divergence between insular and continental populations. Finally, a direct comparison of distributional patterns may suggest the existence of common colonization routes to the West Mediterranean islands. MATERIAL AND METHODS A total of 995 males were examined, belonging to the West Mediterranean mainland (North Africa, Spain, France, Italian Peninsula) and to islands in Sardinia, Corsica, and Sicily (Fig. 1; for locality details, see Supporting Information, Appendix S1). Different areas of the Italian Peninsula represent the nearest source for the three islands. For this reason, it was decided to divide this area into Northern Italy and Southern Italy (using the latitude of Rome as a boundary). Eleven species or groups of related species were analysed separately: Lasiommata megera and Lasiommata paramegaera group; Pararge aegeria; Coenonympha pamphilus and Coenonympha lyllus group; Coenonympha corinna corinna and Coenonympha corinna elbana group; Pyronia cecilia; Pyronia tithonus; Maniola jurtina; Maniola nurag Brintesia circe; Hipparchia neomiris; and the Hipparchia semele, Hipparchia aristaeus, Hipparchia algirica, Hipparchia blachieri and Hipparchia neapolitana group (a detailed sample size is given in Table 1). Because Maniola nurag is a strict Sardinian endemic, specimens were compared with the M. jurtina sample. The 17 specimens, showing the typical characteristics of M. nurag (small size and large orange areas on wings) were collected at approximately 1200 metres a.s.l., where M. jurtina is suggested to be rare (Grill et al., 2007). Hipparchia neomiris is also an island endemic living on Sardinia, Corsica, Capraia, and Elba; the latter is a continental island located very near to Northern Italy. For this reason, specimens belonging to Elba, Corsica and Sardinia were compared. Hipparchia semele and the H. aristaeus complex of species create a quite complete vicariant pattern of several sister taxa in the Mediterranean area. In particular, H. aristaues complex in the West Mediterranean shows the sister taxa: H. aristaeus (Sardinia, Corsica and Tuscan islands), H. algirica (North Africa), H. blachieri (Sicily), and H. neapolitana (Sothern Italy and Pontine islands). In Sicily and Southern Italy, both H. semele and H. aristaeus complexes occur. Thereafter, specimens were attributed to the two complexes by discriminant analysis and the H. aristaeus group occurring on Corsica and Sardinia was assessed in greater detail. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 195–212 or on mainland populations, and rarely on both (Schmitt, Röber & Seitz, 2005; Schmitt, 2007). Dennis, Williams & Shreeve (1991) carried out a comprehensive study on European and North African butterflies on the basis of presence/absence data compiled at the regional scale and highlighted several well-defined faunal regions. However, the largest Mediterranean islands were not coherently classified, probably as a result of impoverishment generating incomparable small faunas (Dapporto & Dennis, 2009) (...truncated)