Phylogenetics, Systematics and Genetic Diversification of Musk Shrew (Suncus murinus) in Southeast Asia

Qhairil Shyamri, Rosli (2019) Phylogenetics, Systematics and Genetic Diversification of Musk Shrew (Suncus murinus) in Southeast Asia. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Due to high phenotypic variation and synonyms of Suncus murinus based on different geographic region, a study on the systematics of Suncus murinus population focusing on Malaysia Borneo samples were conducted by inferring the mitochondrial DNA gene sequences accompanied by morphological variation analysis of the cranio-dental characters. The aim of this study was to identify the phylogenetic relationship based on mtDNA cytochrome b marker of Malaysian Borneo S. murinus population in comparison with other populations from Peninsular Malaysia and other Southeast Asia countries. The phylogenetic inference was obtained based on Maximum Likelihood, Maximum Parsimony, Neighbour Joining and Bayesian inference conducted in MEGA v7.2 and MrBayes software. The SPSS v 21.0 software was utilised to conduct the Principal Component Analysis (PCA) and Discriminant Function Analysis (DFA) based on 14 cranio-dental characters looking into characters overlapping and best characters to distinguish between populations. A total of 56 partial cytochrome b gene sequences with 940 base pair in length were used in the phylogenetic interpretation which resulted in distinct grouping of Malaysian Borneo (Sarawak) population from the Peninsular Malaysia population and other Southeast Asia countries. Based on the phylogenetic inferences, four major clades of S. murinus subspecies was recovered as S. m. caerulescens group, S. m. murinus group, S. m. subspecies 1 group and S. m. kandianus/montanus complex group. According to the generated phylogeny, it can hypothesised that the Malaysian Borneo population can be considered as a separate subspecies or a new subspecies due to unique cladding of the representatives. Malaysian Borneo S. murinus was more closely related to the population from Myanmar and Perak compared to the other geographic region and the highest genetic distance (8.8%) was between populations from Sri Lanka and Japan. Comparing the populations within Malaysia, vii the highest genetic distance (6.5%) was between Terengganu-Perak and Terengganu-Sarawak. The Principal Component Analysis (PCA) conducted on 14 cranio-dental characters were not able to separate the between populations. The analysis of variance (ANOVA) conducted on greatest length skull (GLS) measurement resulted in distinction between Peninsular Malaysia and Borneo Malaysia population for male individuals. Following that, the study was intrigued to pinpoint the diversification route and dispersal events that was undergone by Malaysian Borneo S. murinus population. This was examined by utilising BEAST v6.2 to estimate the divergence time of S. murinus between geographic regions and the S-DIVALIKE via BioGeoBears conducted in RASP v1.1 software to identify the ancestral range probability of each node. Following the results, it is evident that the earliest split of S. murinus in Asia started ~2.66 Mya during the Pliocene separating the Sri Lanka population, the parental ancestor, from the other populations. Moving into the Pleistocene, the divergence was observed beginning at ~2.01 Mya and the most recent splits was ~0.13 Mya. The ancestral range distribution showed that S. murinus ancestor in Asia originate from the Indian plate. This was supported by ancestral distribution probability of p=0.717. In conclusion, the findings suggest an early dispersal of the ancestral population to Malaysian Borneo as a result of exposed land bridges and hull fouling during the Holocene. It was shown that the Malaysian Borneo lineages possibly distinct from the lineages that occur in the other Sunda plate countries and was directly descended from the Sri Lankan population. This was later depicted by the morphological variation of the population. Thus, the Sarawak population should be considered as a potential biological subspecies and regarded as a distinct subspecies of S. murinus. Further examination involving other existing S. murinus subspecies should be conducted using different genetic marker.

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