Phylogenetic island disequilibrium: evidence for ongoing long-term population dynamics in two Mediterranean butterflies
Our aims were to verify the existence of phylogenetic disequilibrium between butterfly lineages at the subcontinental scale for islands and the nearest mainland and to test the capacity of islands for hosting ancestral populations of butterflies and the significance of such relict populations. Location
The western Mediterranean continental area of Europe and North Africa together with several large and small islands (Balearics, Tuscan Archipelago, Aeolian Archipelago, Capri, Sardinia, Sicily, Corsica). Methods
Using geometric morphometrics, the shape of male genitalia was analysed in two common butterflies (Pyronia cecilia and Pyronia tithonus), whose spatial heterogeneity in the Mediterranean region has recently been described. Observed patterns in genital shapes were compared with shapes predicted for islands and fossil islands to assess the contribution of historical and current events in accounting for the transition from a refugial model to an equilibrium model. Measurements were taken for 473 specimens in 90 insular and mainland sites. Results
The shape of the genitalia of populations of most islands differed substantially from that predicted by the equilibrium hypothesis while closely fitting the refugial hypothesis. The comparison between different models strongly suggests that islands maintain ancestral lineages similar to those living in Spain (P. cecilia) and France (P. tithonus). A high correlation between observed and predicted patterns on islands and fossil islands occurs during the first steps of modelled introgressive hybridization while the following steps exposed a successively lower fit, suggesting that the process from a refugial to an equilibrium situation is highly skewed towards an earlier non-equilibrium. Main conclusions
The observed non-equilibrium pattern supports the refugial hypothesis, suggesting that an ancestral lineage was originally distributed from Spain to Italy, and also occupied offshore islands. This lineage, replaced in Italy, has persisted on the islands owing to their isolation. A comparison of the distribution patterns for genetic and morphometric markers in several species indicates that the situation highlighted for Pyronia may represent a common biogeographic feature for many Mediterranean butterflies.
Document Type: Research Article
Department of Biogeography, Trier University, D-54296 Trier, Germany
ICREA and Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
CRA Centro di Ricerca per l’Olivicoltura e l’Industria Olearia, I-87036 Rende (Cosenza), Italy
Markusstrasse 17, D-3490, Bad Driburg, Germany
Área de Zoología, Facultad de Biología, Campus ‘Miguel de Unamuno’ Universidad de Salamanca, 37007 Salamanca, Spain
NESOS, Associazione pro Isole, Corso Vittorio Emanuele, 24 98055 Lipari (ME), Italy
Publication date: May 1, 2011
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Gayubo, Severiano F.
González, José A.
Lo Cascio, Pietro
Dennis, Roger L. H.