... Each focal taxon (Harpactes ardens, Ceyx melanurus, Pachycephala philippinensis, Pycnonotus urostictus, Irena cyanogastra, Dicaeum hypoleucum, Prionochilus olivaceus, Aethopyga pulcherrima) has traditionally been considered a single species (Dickinson et al. 1991; Kennedy et al. 2000; Gill and Donsker 2013); although under lineage-focused species recognition criteria, each could be considered a suite of allopatric replacement species (Peterson 2006; Moltesen et al. 2012; Andersen et al. 2013; Hosner et al. 2013a). ...
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Using congruence between operational criteria from both genetic markers (strongly supported monophyly, strong genetic differentiation between geographically-circumscribed groups) and phenotypic characters (fixed, diagnosable differences in plumage/morphology; assessed from museum specimens), the eight focal species would instead be partitioned into 16: C. melanurus partitioned into Ceyx melanurus, C. samarensis, and C. mindanensis (Collar 2011; Andersen et al. 2013); I. cyanogastra partitioned into I. cyanogastra I. ellae, and I. melanochlamys (including hoogstraali; Moltesen et al. 2012); D. hypoleucum partitioned into D. hypoleucum (including mindanense), D. pontifex, and D. obscurum (including cagayanense); Aethopyga pulcherrima, partitioned into A. pulcherrima A. jeffreyi, and A. decorosa (Hosner et al. 2013a). Two species require further evaluation because evidence from molecular markers and phenotype do not agree. Pachycephala philippinensis is genetically highly structured, yet the only populations differing in fixed plumage characters are the two distinctive populations inhabiting Calayan and Camiguin Norte islands to the north of Luzon, making phenotypically similar populations from the Luzon and Mindanao PAICs paraphyletic. Similarly, Luzon and Mindanao PAIC populations of P. olivaceus are each distinctive and diagnosable in plumage, but we recovered birds from Samar as sister to the Luzon PAIC populations rather than to Mindanao populations. Harpactes ardens and P. urostictus each include strongly differentiated populations genetically, but differences in appearance are subtle; populations are not diagnosable by fixed plumage or morphological differences.
