A DNA analysis has proven what a curator's eyes already told him - there are three endemic scops owls in the Philippines.
Using two mitochondrial genes from the six generally accepted forms of Philippine scops owls, a three-man Texan team was able to show that three named subspecies of Otus megalotis (a fourth has been synonymised recently) - Philippine Scops Owl - formed one of two separate clades and represented three actual full species.
A paper in The Wilson Journal of Ornithology shows the phylogenetic tree in full, and this demonstrates not only the different species' relationships, but also allows their ancestors' patterns of colonisation to be inferred. The three island populations are split as Luzon Lowland Scops Owl O megalotis, Mindanao Lowland Scops Owl (aka Everett's Scops Owl according to the International Ornithological Union - IOU formerly the IOC) O everetti and Visayan Lowland Scops Owl (aka Negros Scops Owl per IOU) O nigrorum. They form a lowland clade with Mimizuku gurneyi, Giant Scops Owl, also found on Mindanao, and all are counter-intuitively derived from the same source as the widespread Montane Scops Owl O spilocephalus. Genetic distances between the species range from 3.6 to 4.2 per cent, bigger than many accepted good species.
The remaining two endemic forms - forming the other montane clade - are Luzon Scops Owl O longicornis and Mindanao Scops Owl O mirus share a common ancestor with the widespread Oriental Scops Owl O sunia.
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The three new species from top to bottom: Luzon Lowland Scops Owl, Visayan Lowland (Negros) Scops Owl and Mindanao Lowland (Everett's) Scops Owl. Illustration: Hector Miranda. |
Dr Dan Brooks, Curator of Vertebrate Zoology at the Houston Museum of Natural Science, knew upon first examination and his subsequent analysis of the specimens that different species were likely to be involved, because of their extreme differences in size and colour. “I was shocked when I first noticed the distinct physical characteristics among the birds - I knew that these had to be different species,” he said. “Sure enough, further testing proved this to be accurate.”
The two clades indicate at least two colonisation events producing a montane and lowland radiation in turn, a situation similar to the colonisation of island mammals. the authors also recommend that Giant Scops Owl is renamed O gurneyi.
The fact that the three new species are each endemic to unique regions of the Philippines translates directly into greater conservation value. The research serves to underline that the number of endemic species in the still little-studied Philippine archipelago, may be much higher than current estimates. Currently there are over 600 species of Philippine birds, of which nearly 200 are endemic. Mindanao and Luzon currently rank in the top 10 and 20 of global regions supporting the highest numbers of endemic birds, respectively. It is possible these regions could be even higher, pending the outcome of other unidentified Philippine species. As such, their importance as conservation priority as biodiversity hotspots would rank even higher, though, like many of the islands, their key habitats are continuously under threat from deforestation and climate change.
Reference
Miranda, H C Jr, Brooks, D M and Kennedy, R S. 2011. Phylogeny and taxonomic review of Philippine lowland scops owls (Strigiformes): parallel diversification of highland and lowland clades. The Wilson Journal of Ornithology 123: 441-452. http://www.hmns.org/files/PhilippineScopsEprint.pdf
