Miranda et a/. • TAXONOMY OF PHILLIPINE SCOPS OWLS 
451 
Our study supported the third model. All montane 
Otus taxa between islands comprised one clade 
and the lowland Otus in other islands formed 
another parallel clade. This split within the Otus 
clade may extend deeper within the strigiform 
phylogeny; the extent of which can be revealed by 
more extensive taxon sampling and phylogenetic 
analysis. 
The 0. megalotis intraspecific genetic distances 
was relatively large with p-distance between O. m. 
everetti and 0. m. megalotis at 3.8%, 0. in. 
nigrorum and O. m. everetti at 3.6%, and O. in. 
mgrontm and 0. /n. megalotis at 4.2% (Table 3). 
These values were much higher than the p- 
distances between the three non-Philippine spe¬ 
cies with O. bakkamoena and O. lempiji at 0.03%. 
between 0. bakkamoena and O. lettia at 1.0%, 
and between O. lempiji and O. lettia at 1.2%. The 
p-distance values observed among the Philippine 
0. megalotis subspecies were also comparatively 
higher than those observed between subspecies of 
other Otus species elsewhere (Proudfoot et ul. 
2007). Genetic distances are approximations of 
differentiation (Meier et al. 2006) and may not 
necessarily be diagnostic of species limits (Wink¬ 
er 2009, 2010). However, the distances we 
observed are consistent and comparable with 
species-level differentiation among birds (Kerr 
et al. 2007). These distances are congruent with 
the discrete morphological differences among the 
Otus taxa that u'e documented in this study. 
Estimating divergence dates within a clade 
based on either island emergence chronology 
(Cooper and Penny 1997, Steppan et al. 2003. 
Weir and Schluter 2004) or sequence divergence 
values (Lovette 2005) are promising but with 
caveats (Garcia-Moreno 2004). A recent analysis 
supported the 2% per million years constant of the 
mitochondrial molecular clock for most avian 
lineages (Weir and Schluter 2008). and we applied 
this generality with caution. Our well-supported 
phylogeny showed the lowland invasion of the 
Philippine Archipelago by the lineage that led to 
M. gurneyi started in Greater Mindanao. Sequence 
divergence between M, gumeyi and non-Philip- 
pine lowland scops owls ( O. spilocephalus/O. 
U'tiia/O. lempiji/O. bakkamoena) was calculated 
al 11 - 0.06%. Assuming a 2% sequence 
divergence per million years (at least for the 
cyt -b gene), a divergence date of 5.5 mya 
coincided with the most recent date of emergence 
of Mindanao Island (estimated at 8 to 6 mya). 
Extensive volcanism followed island emergence 
from the sea floor, and it is likely that colonization 
by ancestral M, gumeyi occured much later, rather 
than earlier. The second calibration was the 
divergence of O. m. nigrorum from the ancestral 
M. gumeyi. Sequence divergence of 5.6% sug¬ 
gests a colonization date of the Greater Panay- 
Negros Island block at 2.8 mya. The Panay- 
Negros block emerged from the sea floor de novo 
about 2 mya (Steppan et al. 2003); the discrep¬ 
ancy of 0.8 mya can be explained either by (1) 
later estimates for the emergence of the Panay 
Negros block, or (2) overestimation of rates due to 
genetic drift, bottlenecks, and founder effects 
(Carson and Templeton 1984. Thorpe et al. 1994) 
as the Greater Panay-Ncgros block experienced 
fragmentation during the last Pleistocene ice age. 
100,000 to 10,000 years ago (Heaney 1986). 
We present evidence that parallel multiple 
colonization in two elevational zones shaped the 
pattern of the genus Otus community within the 
Philippine Archipelago. It is possible that Mind¬ 
anao Island was colonized three times; once along 
the montane route ( O. minis), and possibly twice 
via the lowland route. O. megalotis nigrorum from 
the Visayas is basal to the much larger Luzon and 
Mindanao islands. The question for Mimizuku 
remains whether it represents a lineage from a 
third colonization event, or speciated de novo 
within the ancestral megalotis. 
Taxonomic Changes .—We reviewed the litera¬ 
ture to find the rationale for keeping the three O. 
megalotis island populations within one species 
(Marshall 1978. Amadon and Bull 1988). How¬ 
ever. previous phenotypic analysis was lacking 
and no defined character analysis, based on either 
morphology or vocalizations, was conducted. Our 
analyses based on genetic (molecular) and mor¬ 
phological approaches, suggest the three mega¬ 
lotis subspecies represent evolutionarily distinct 
taxa under the phylogenetic species concept 
(PSC). We strongly suggest recognition of species 
status for the three megalotis subspecies; Luzon 
Lowland Scops Owl (0. megalotis), Mindanao 
Scops Owl (0. everetti). and Visayan Scops Owl 
(0. nigrorum). The relatively large size of the 
Giant Scops Owl represents an autapomorphy but 
its phylogenetic position as a terminal lineage 
does not warrant genus status. We suggest the 
Giant Scops Owl be designated as Otus gumeyi. 
ACKNOWLEDGMENTS 
W’e thank Glenn Storrs. Heim Mays (CMC), and Ron 
DeBry (University of Cincinnati) for tissue bans, and Jean 
