Indochinese‐Sundaic faunal transition and phylogeographical divides north of the Isthmus of Kra in Southeast Asian Bulbuls (Aves: Pycnonotidae)

Abstract

Aim For terrestrial organisms, a faunal transition zone between the Indochinese and Sundaic regions is delimited north of the Isthmus of Kra on the Thai‐Malay Peninsula. We used a mitochondrial marker to test the predicted location of intraspecific north–south divides for four species of bulbuls ( Pycnonotus ). Phylogenetic relationships among Thai‐Malay populations and their closest relatives from the Greater Sundas were reconstructed from a multilocus data set including 35 Pycnonotus species. Location Indochina, Thai‐Malay Peninsula, Greater Sundas. Methods We sampled target species along a north–south transect spanning the Isthmus of Kra and reconstructed phylogeographical patterns based on ND2 haplotype networks. Phylogenies were reconstructed using Maximum likelihood and Bayesian inference. Divergence time estimates were inferred from single‐locus and multilocus data using * beast . Results We found mitochondrial north–south divides in all target species. Haplotypes of southern genetic clusters were distributed all across the Thai‐Malay Peninsula and north into Central Thailand. Local overlap of genetic lineages was confirmed at one location in one species only. In three of the focal species, the southern limits of southern haplotype clusters were restricted to the Thai‐Malay Peninsula and did not extend into the Greater Sundas. Peninsular north–south divides were dated to the late Pleistocene, whereas Indochinese‐Sundaic lineage divergence was dated to the late Pliocene. Main conclusions Population boundaries did not coincide with the Isthmus of Kra, but instead were located north of the Thai‐Malay Peninsula in Central Thailand. Only one of four divides represented an Indochinese‐Sundaic transition. Different phylogeographical patterns among target species were presumably shaped by different ecological preferences in Pleistocene palaeohabitats. Pliocene Indochinese‐Sundaic lineage divergence in bulbuls coincides with strong vegetational changes on the Peninsula that shaped two phytogeographical transitions. Distribution limits of bird species roughly coincide with these transition zones and therefore the avifaunal Thai‐Malay transition represents a broad zone rather than a sharp boundary.

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