A molecular sexing method by polymerase chain reaction (PCR) amplification of a portion of the sexdetermining region Y (SRY) and the zinc finger (ZF) gene, as well as six equine Y-chromosome-specific microsatellite markers, were tested in the Malayan tapir (Tapirus indicus). While the microsatellite markers did not yield any male-specific amplicons for sex-typing, the SRY/ZF marker system produced reliable molecular sexing results by accurately sex-typing 31 reference Malayan tapirs, using whole blood, dried blood spot (DBS), or tissue samples as materials for DNA extraction. The marker system was also tested on 16 faecal samples, and the results were in general consistent with the predetermined sexes of the animals, despite some amplification failures. A preliminary estimation of wild Malayan tapir population sex ratio was estimated from the Wildlife Genomic Resource Bank (WGRB) database of the Malaysian Department of Wildlife and National Parks (PERHILITAN), zoos, and the Sungai Dusun Wildlife Conservation Centre (WCC), as well as from the results of molecular sexing 12 samples of unknown sex. The overall sex ratio favoured females, but the deviation from parity was statistically not significant when tested using the binomial test (p > 0.05), which may be due to reduced statistical power caused by small sample sizes. Sex ratio, conventionally defined according to life-history stages such as pre-birth (e.g. sex ratio at fertilisation) or post-birth (e.g. sex ratio at birth, adult sex ratio), is used to describe a population 1. The sex ratio at different stages of life is influenced by one or a set of sex-differential processes such as sex determination, survival, development, maturation, migration, mate competition, and parental investment 2-4. One of the types, the adult sex ratio, is estimated by counting the number of males and females who have matured, regardless of whether they are sexually active or have produced offspring 2. Adult sex ratio can vary depending on species, for examples, in species with heterogametic males (e.g. mammals), the ratio tend to be female-biased, while in species with heterogametic females (e.g. birds), the ratio tends to be male-biased 5. In mammals, at birth, the populations are expected to have a 1:1 ratio for male to female offspring because of the Mendelian mode of inheritance of sex chromosomes-theoretically half of the offspring would possess the XY genotype, thus developing into males; and if the cost to produce either sex is equal, parity in adult sex ratio is expected 4,6. However, in reality, mammalian population sex ratios may vary with the costs and benefits of producing male and female offspring 7. The Malayan tapir (Tapirus indicus) is an endangered mammal species listed in the International Union for Conservation of Nature (IUCN) Red List 8. This tapir species is the only Old-World species in the family Tapiridae and can be found in regions of Southeast Asia 9. Its worldwide population is declining due to threats

The Malayan tapir (Tapirus indicus) is an endangered species in Southeast Asia (SEA). Over the years, there has only been a few reports on its population genetic structure and evolutionary history in SEA. In particular, while the captive Malayan tapir population in Thailand has received fairly more research in recent years, there has not been any widescale population genetic study in the Malay Peninsula since the last decade. In this study, we report on the genetic diversity and attempt to make inferences on the phylogeography of the Malayan tapir in the Malay Peninsula, using the mitochondrial DNA control region, including also data from previous studies. We identified 12 novel haplotypes and two distinct Malayan tapir clades with a divergence time of 14.6 million years ago (mya) in the Peninsular Malaysia (i.e. southern Malay Peninsula) samples, as opposed to only one clade found in the Thai (i.e. Thailand western border and northern Malay Peninsula) captive individuals, with an almost two-fold higher nucleotide diversity compared to the latter. The co-occurrence of the two lineages in southern Malay Peninsula suggested past historical events of population isolation, migration and admixture as a result of episodic glacial periods and paleoenvironmental changes in SEA. Only one haplotype shared between the populations of the two regions suggested further gene flow restriction at the narrow corridor of the Malay Peninsula as of present day. Keywords D-loop • Asian tapir • Peninsular Malaysia • Thailand • Population genetic structure Communicated by Pradeep Kumar Divakar.