The population genetics study is crucial as it helps in understanding the epidemiological aspects of dengue and help improving a vector control measures. This research aims to investigate the population genetics structure of two common species of Aedes mosquitoes in Penang; Aedes aegypti and Aedes albopictus using Cytochrome Oxidase I (COI) mitochondrial DNA (mtDNA) marker. Molecular investigations were derived from 440 bp and 418 bp mtDNA COI on 125 and 334 larvae of Aedes aegypti and Aedes albopictus respectively, from 32 locations in Penang. All samples were employed in the BLASTn for species identification. The haplotype diversity, nucleotide diversity, neutrality test and mismatch distribution analysis were conducted in DnaSP version 5.10.1. AMOVA analysis was conducted in ARLEQUIN version 3.5 and the phylogenetic reconstructions based on maximum likelihood (ML) and neighbor-joining (NJ) methods were implemented in MEGA X. The relationships among haplotypes were further tested by creating a minimum spanning tree using Network version 4.6.1. All samples were genetically identified and clustered into six distinct species. Among the species, Ae. albopictus was the most abundant (67.2%), followed by Ae. aegypti (25.2%) and the rest were counted for Culex sp. and Toxorhynchites sp. Both Ae. aegypti and Ae. albopictus show low nucleotide diversity (π) and high haplotype diversity (h), while the neutrality test shows a negative value in most of the population for both species. There are a total of 39 and 64 haplotypes recorded for Ae. aegypti and Ae. albopictus respectively. AMOVA analysis revealed that most of the variation occurred within population for both species. Mismatch distribution analysis showed bimodal characteristic of population differentiation for Ae. aegypti but Ae. albopictus showed unimodal characteristics of population differentiation. Genetic distance based on Tamura-Nei parameter showed low genetic divergent within population and high genetic divergent among population for both species. The maximum likelihood tree showed no obvious pattern of population genetic structure for both Ae. aegypti and Ae. albopictus from Penang and a moderate to high bootstrap values has supported this conclusion. The minimum spanning network for Ae. aegypti and Ae. albopictus showed five and three dominant haplotypes respectively, which indicates a mixture of haplotypes from the regions analysed. This study revealed that there is no population genetic structure exhibited by both Ae. aegypti and Ae. albopictus in Penang. Mutation has occurred rapidly in both species and this will be challenging in controlling the populations. However, further analysis needed to confirm this statement.
Mitochondrial cytochrome oxidase subunit I (COI) gene was utilized to assess the population genetics of the commercially important black scar oyster, Crassostrea iredalei among 11 populations throughout the west and east coasts Peninsular Malaysia and Sabah (Malaysian Borneo). Overall, populations of C. iredalei demonstrated low nucleotide diversity π (0.000-0.004) and low-to-high haplotype diversity h (0.000-0.795) levels. Genetic structuring was detected between the Peninsular Malaysia and Sabah populations as revealed by the FST analysis. However, the COI gene analyses showed minimal and non-significant (p > 0.05) population differentiation within the east and west coasts Peninsular Malaysia and Sabah regions. This was attributed to both high larval dispersal along the east and west coasts and human-driven spat translocation between the two coastlines due to C. iredalei cultivation practices. Phylogeographic relationships inferences were also conducted to further support these hypotheses. The neutrality and mismatch distribution analyses suggested that C. iredalei had experienced a/several bottleneck event(s), followed by population expansion. The molecular information obtained from this study could be incorporated in a pragmatic aquaculture management strategy of wild broodstock and the hatchery lines of C. iredalei in Malaysia.