Molecular Data and Karyotype Revealed Two Distinct Species of Domesticated Water Buffaloes in the Philippines

Abstract

The six species of the genus Bubalus include the lowland and mountain anoa, Asian wild buffalo, tamaraw, swamp buffalo, and riverine buffalo. Few studies were conducted on the matrilineal phylogeny and genetic diversity of Bubalus species. In addition, there is controversy regarding the identity of the two domesticated water buffaloes in the Philippines – the introduced riverine and the native swamp buffalo. Thus, this study aimed to determine the genetic distance and phylogenetic relationship of Bubalus species using the mitochondrial cytochrome b (cytb) variation and to re-evaluate the taxonomic species designation of Bubalus bubalis. A total of499 Philippine cytb sequences from this study (n = 179), as well as other Asian countries (n = 319)and Syncerus caffer (n = 1), from NCBI were included in the analysis. The highest interspecies genetic distance (d) (0.040) was between the tamaraw and lowland anoa, whereas the lowest genetic distance (0.020) was between mountain and lowland anoa. Moreover, the phylogenetic tree indicated 52 haplotypes that delineated three groups, including lowland anoa, mountain anoa, and tamaraw with two domesticated buffaloes. The latter group further separated into three species – tamaraw, riverine, and swamp buffaloes. The analyses of genetic distance,phylogeny, and median-joining network structure based on cytb confirmed that the swamp buffaloes from Occidental Mindoro and South Cotabato, Philippines belong to maternal lineage B. Karyotype analysis consistently confirms that riverine buffaloes possess 50 chromosomes, whereas swamp buffaloes have 48 chromosomes, aligning with previous findings. Moreover, the swamp and riverine buffaloes appear to be distinct species, with the swamp buffalo having a closer affinity to the tamaraw than to the riverine buffalo. We, therefore, propose to revive the species assignment of the Bubalus kerabau Fitzinger, 1860 as a distinct species to the swamp buffalo. Furthermore, a common maternal ancestry was confirmed between the tamaraw and two domesticated buffaloes – the swamp and riverine. Research findings provided valuable information on understanding and monitoring the matrilineal genetic diversity of the genus Bubalus toward conservation and management.