Genetic differentiation and natural hybridization between the Sardinian endemicManiola nuragand the EuropeanManiola jurtina

Abstract

The Mediterranean island of Sardinia is known for its multitude of unique genetic lineages. We view one of them in a larger phylogeographic context. The endemic Sardinian Meadow Brown butterfly, Maniola nurag, is restricted to the mountainous areas of the island, whereas its widespread close relative, Maniola jurtina, also occurs on the coast. At intermediate altitudes the species’ distributions overlap. There, a number of individuals exhibit phenotypic characteristics intermediate between the two species. We examined patterns of intra‐ and interpopulation variation in 10 M. nurag populations from Sardinia and 16 M. jurtina populations from Sardinia and continental Europe, as well as 17 intermediate individuals, sampled in 1999–2002, by means of allozyme markers, combining it with a morphometric analysis based on 18 wing‐characters of 52 males. At the 15 loci studied (aldolase, aat‐1, aat‐2, g6pdh, gpd, idh‐1, idh‐2, mdh‐1, mdh‐2, mpi, me, leu‐ala, pgi, pgm, and 6pgdh), 76 different alleles were detected, 63 of which were shared by M. nurag and M. jurtina. None of the loci was found to be alternatively fixed between the two species. In that respect, this study testifies to the difficulties that may arise when trying to identify hybrids from genotypic data. Levels of genetic variation in island populations (M. jurtina: HO = 0.137–0.189; M. nurag: HO = 0.141–0.270) were comparable to those of mainland M. jurtina (HO = 0.141–0.236). A Bayesian admixture analysis supported the hypothesis of mixed (hybrid) ancestry of individuals occurring at intermediate altitudes. Similarly, neighbour‐joining and unweighted pair‐group method with arithmetic averaging (UPGMA) analyses, as well as morphometrics hinted at the existence of a Maniola‐hybrid zone in Sardinia at intermediate altitudes. We discuss the results in the light of the phylogeography of other Sardinian taxa with the aim to reach a general understanding of the biogeographic history of this island's endemic species.

Phylogeography of Sardinian Cave Salamanders (Genus Hydromantes) Is Mainly Determined by Geomorphology

“…Mountain chains and elevational gradients have been reported to act as barriers to gene flow in amphibians [18], [56], [57], [58] and mountain regions have been recognized as centers of high endemism and diversification for many Sardinian organisms (e.g., [59], [60], [61]). Many biogeographic and phylogeographic studies have included Sardinian organisms (e.g., [62], [63], [64], [65], [66], [67], [68]), but very few of them focused on diversification patterns within this island, often using only a very sparse sampling (but see [28]).…”

A hybrid zone provides evidence for incipient ecological speciation inHeliconiusbutterflies

“…This study therefore adds to a growing number of studies of ecotonal divergence (Schneider et al . 1999; Grill et al . 2007; Blum 2008).…”

Tracing the radiation of Maniola (Nymphalidae) butterflies: new insights from phylogeography hint at one single incompletely differentiated species complex

“…Among them, four species are narrowly endemic to islands and therefore belong to those butterflies of Europe with the smallest ranges: M. cypricola Graves, 1928 on Cyprus, M. chia Thomson, 1987 on the Aegean islands Chios and Inousses, M. halicarnassus Thomson, 1990 on the Aegean island Nisyros and the neighboring Turkish Bodrum peninsula, and M. nurag Ghiliani, 1852 on Sardinia (Grill et al. ; Kudrna et al. ).…”