Tracing the colonization history of the Indian Ocean scops-owls (Strigiformes: Otus) with further insight into the spatio-temporal origin of the Malagasy avifauna

Abstract

BackgroundThe 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.ResultsOur 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.ConclusionOur 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.

Determining the Specific Status of Korean Collared Scops Owls

“…A slight genetic difference between the Korean collared scops owl and O. semitorques was detected in cyt b gene (Table 3), which may be considered as a regional variation (Deignan, 1950;Weick, 2006 (Weick, 2006) and members of the genus Otus are similar in plumage. Species discrimination of some taxa relies only on vocalization (Weick, 2006;Fuchs et al, 2008) We had similar results with the MHC II gene (534 bp, nuclear DNA, unpublished to date), which grouped Japanese specimens together with Korean collared scops owls with very low genetic differentiation (d= =0.004). No regional difference between Korean and Japanese specimens was detected.…”

“…The taxonomic status of this species with other related Otus species is not clear. Several studies have been performed to resolve this issue (Heidrich et al, 1995;Wink and Heidrich, 2000;Ryu and Park, 2003;Wink et al, 2004;Fuchs et al, 2008) (König et al, 1999;Weick, 2006;Fuchs et al, 2008;Lok et al, 2009). Their population has been decreasing gradually owing to many anthropogenic factors especially collision and traffic accidents (Kim, 2006;CHA, 2010).…”

“…Therefore, some recent literatures also note these populations as two different species (O. lempiji ussuriensis and O. semitorques semitorques) (Clements, 2007) or even merge these groups into one single species O. lempiji (O. lempiji ussuriensis and O. l. semitorques) (Tomek, 1999) (König and Weick, 2008) which is distributed in southeast Siberia to Japan (del Hoyo et al, 1999;Weick, 2006;Fuchs et al, 2008). While there is record that Korean population has paler and grayer tones than Japanese population especially in its light markings (Deignan, 1950), when considering the geographic proximity and the possible existence of a local population belonging to Japanese population on Jeju island in Korea, the scops owl occurs in Korea may more closely related with O. semitorques rather than O. lempiji and O. bakkamoena.…”

“…The phylogeny of Otus remains unclear (Heidrich et al, 1995;del Hoyo et al, 1999;Ryu and Park, 2003;Proudfoot et al, 2007;Fuchs et al, 2008 …”

Did postglacial sea-level changes initiate the evolutionary divergence of a Tasmanian endemic raptor from its mainland relative?

“…Examples of marine dispersal of similar or greater magnitude by other raptors (some migratory) are also documented both from direct observations [59,60], palaeontological evidence ( [61], e.g. the swamp harrier, Circus approximans, colonizing New Zealand probably less than 1000 years ago; [62]), and reconstructions of phylogenetic relationships [63][64][65].…”