Tracing the colonization history of the Indian Ocean scops-owls (Strigiformes: Otus) with further insight into the spatio-temporal origin of the Malagasy avifauna
1 UMR5202 «Origine, Structure et Evolution de la Biodiversité», Département Systématique et Evolution, Muséum National d'Histoire Naturelle, 55 Rue Buffon, 75005 Paris, France
2 Service Commun de Systématique Moléculaire, IFR CNRS 101, Muséum National d'Histoire Naturelle, 43, rue Cuvier, 75005 Paris, France
3 DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, Rondebosch 7701, Cape Town, Republic of South Africa
4 Museum of Vertebrate Zoology and Department of Integrative Biology, 3101 Valley Life Science Building, University of California, Berkeley, CA 94720-3160, USA
5 Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605, USA
6 Vahatra, BP3972, Antananarivo (101), Madagascar
7 CEBC-CNRS, Beauvoir sur Niort, 79360, France
8 UMR5175 Centre d'Ecologie Fonctionnelle et Evolutive, 1919 Route de Mende, F-34293 Montpellier Cedex 5, France
9 Nature Seychelles, PO Box 1310, Victoria, Mahé, Republic of Seychelles
10 BirdLife International, Wellbrook Court, Girton Road, Cambridge CB3 0NA, UK
11 The Peregrine Fund, 5668 West Flying Hawk Lane, Boise Idaho 83709, USA
12 Department of Biology, Leicester University, LE1 7RH, UK
13 Department of Ornithology, National Museums of Kenya, P.O. Box 40658, Nairobi, Republic of Kenya
14 Department of Environment, Ministry of Agriculture, Natural Resources, Environment and Cooperatives, Zanzibar Revolutionary Government, P.O. Box 811, Zanzibar, United Republic of Tanzania
15 Genoscope, Centre National de Séquençage, 2 rue Gaston Crémieux, CP5706, 91057 Evry Cedex, France
BMC Evolutionary Biology 2008, 8:197 doi:10.1186/1471-2148-8-197Published: 9 July 2008
The island of Madagascar and surrounding volcanic and coralline islands are considered to form a biodiversity hotspot with large numbers of unique taxa. The origin of this endemic fauna can be explained by two different factors: vicariance or over-water-dispersal. Deciphering which factor explains the current distributional pattern of a given taxonomic group requires robust phylogenies as well as estimates of divergence times. The lineage of Indian Ocean scops-owls (Otus: Strigidae) includes six or seven species that are endemic to Madagascar and portions of the Comoros and Seychelles archipelagos; little is known about the species limits, biogeographic affinities and relationships to each other. In the present study, using DNA sequence data gathered from six loci, we examine the biogeographic history of the Indian Ocean scops-owls. We also compare the pattern and timing of colonization of the Indian Ocean islands by scops-owls with divergence times already proposed for other bird taxa.
Our analyses revealed that Indian Ocean islands scops-owls do not form a monophyletic assemblage: the Seychelles Otus insularis is genetically closer to the South-East Asian endemic O. sunia than to species from the Comoros and Madagascar. The Pemba Scops-owls O. pembaensis, often considered closely related to, if not conspecific with O. rutilus of Madagascar, is instead closely related to the African mainland O. senegalensis. Relationships among the Indian Ocean taxa from the Comoros and Madagascar are unresolved, despite the analysis of over 4000 bp, suggesting a diversification burst after the initial colonization event. We also highlight one case of putative back-colonization to the Asian mainland from an island ancestor (O. sunia). Our divergence date estimates, using a Bayesian relaxed clock method, suggest that all these events occurred during the last 3.6 myr; albeit colonization of the Indian Ocean islands were not synchronous, O. pembaensis diverged from O. senegalensis about 1.7 mya while species from Madagascar and the Comoro diverged from their continental sister-group about 3.6 mya. We highlight that our estimates coincide with estimates of diversification from other bird lineages.
Our analyses revealed the occurrence of multiple synchronous colonization events of the Indian Ocean islands by scops-owls, at a time when faunistic exchanges involving Madagascar was common as a result of lowered sea-level that would have allowed the formation of stepping-stone islands. Patterns of diversification that emerged from the scops-owls data are: 1) a star-like pattern concerning the order of colonization of the Indian Ocean islands and 2) the high genetic distinctiveness among all Indian Ocean taxa, reinforcing their recognition as distinct species.