Tropical rainforests are considered as hotspots for bird diversity, yet little is known about the system that upholds the coexistence of species. Differences in body size that are associated with foraging strategies and spatial distribution are believed to promote the coexistence of closely related species by reducing competition. However, the fact that many babbler species do not differ significantly in their morphology has challenged this view. We studied the foraging ecology of nine sympatric babbler species (i.e., Pellorneum capistratum, P. bicolor, P. malaccense, Malacopteron cinereum, M. magnum, Stachyris nigriceps, S. nigricollis, S. maculata, and Cyanoderma erythropterum) in the Krau Wildlife Reserve in Peninsular Malaysia. We investigated; i) how these babblers forage in the wild and use vegetation to obtain food, and ii) how these trophically similar species differ in spatial distribution and foraging tactics. Results indicated that most babblers foraged predominantly on aerial leaf litter and used gleaning manoeuvre in intermediate-density foliage but exhibited wide ranges of vertical strata usage, thus reducing interspecific competition. The principal component analysis indicated that two components, i.e., foraging height and substrate are important as mechanisms to allow the coexistence of sympatric babblers. The present findings revealed that these bird species have unique foraging niches that are distinct from each other, and this may apply to other insectivorous birds inhabiting tropical forests. This suggests that niche separation does occur among coexisting birds, thus following Gause' law of competitive exclusion, which states two species occupying the same niche will not stably coexist.
The Indo-Malayan bioregion has provided some of the most spectacular discoveries of new vertebrate species (e.g. saola, khanyou, bare-faced bulbul) over the last 25 years. Yet, very little is known about the processes that led to the current biodiversity in this region. We reconstructed the phylogeographic history of a group of closely related passerines, the Alophoixus bulbuls. These birds are continuously distributed in Indo-Malaya around the Thailand lowlands such that their distribution resembles a ring. Our analyses revealed a single colonization event of the mainland from Sundaland with sequential divergence of taxa from southwest to northeast characterized by significant gene flow between parapatric taxa, and reduced or ancient gene flow involving the two taxa at the extremities of the ring. We detected evidence of population expansion in two subspecies, including one that was involved in the closing of the ring. Hence, our analyses indicate that the diversification pattern of Alophoixus bulbuls fits a ring species model driven by geographic isolation. To our knowledge, the Alophoixus bulbuls represent the first case of a putative broken ring species complex in Indo-Malaya. We also discuss the implications of our results on our understanding of the biogeography in Indo-Malaya.
The complete mitochondrial genomes of two jungle crows (Corvus macrorhynchos) were sequenced. DNA was extracted from tissue samples obtained from shed feathers collected in the field in Sri Lanka and sequenced using the Illumina MiSeq Personal Sequencer. Jungle crow mitogenomes have a structural organization typical of the genus Corvus and are 16,927 bp and 17,066 bp in length, both comprising 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal subunit genes, and a non-coding control region. In addition, we complement already available house crow (Corvus spelendens) mitogenome resources by sequencing an individual from Singapore. A phylogenetic tree constructed from Corvidae family mitogenome sequences available on GenBank is presented. We confirm the monophyly of the genus Corvus and propose to use complete mitogenome resources for further intra- and interspecies genetic studies.
Biogeographic connections between Australia and other continents are still poorly understood although the plate tectonics of the Indo-Pacific region is now well described. Eupetes macrocerus is an enigmatic taxon distributed in a small area on the Malay Peninsula and on Sumatra and Borneo. It has generally been associated with Ptilorrhoa in New Guinea on the other side of Wallace's Line, but a relationship with the West African Picathartes has also been suggested. Using three nuclear markers, we demonstrate that Eupetes is the sister taxon of the South African genus Chaetops, and their sister taxon in turn being Picathartes, with a divergence in the Eocene. Thus, this clade is distributed in remote corners of Africa and Asia, which makes the biogeographic history of these birds very intriguing. The most parsimonious explanation would be that they represent a relictual basal group in the Passerida clade established after a long-distance dispersal from the Australo-Papuan region to Africa. Many earlier taxonomic arrangements may have been based on assumptions about relationships with similar-looking forms in the same, or adjacent, biogeographic regions, and revisions with molecular data may uncover such cases of neglect of ancient relictual patterns reflecting past connections between the continents.