ABSTRACT
Samples of Chrysomya megacephala were collected from five sites in Malaysia, namely Penang, Selangor, Pahang, Johor, and Sabah. Molecular analysis was conducted using the cytochrome oxidase gene and ISSR-PCR to identify polymorphic markers for distinguishing the populations and to estimate the genetic relatedness among these populations. Two SNPs were detected at sequence position 952 (M1) and 1120 (M2), involving transitional substitutions with cytosine (C) being replaced with thymine (T) and guanine (G) replaced with adenine (A), but there was no amino acid variation. Penang and Selangor shared the same nucleotide T at the M1 position, while M2 variation was found in Pahang population only. The NJ tree based on the COI sequence showed two main groups with branch A comprised of Penang and Selangor populations while branch B consisted of Johor, Pahang and Sabah populations. ISSR analysis indicated that 18 scorable bands (size 200 to 1800 bp) were amplified with UBC808 and UBC835, 11 bands of which were polymorphic and the rest monomorphic. Sabah population was left out for further analysis due to small number of specimens. UPGMA dendrogram using ISSR data showed two branches, one consisted of Penang and Selangor populations, while the other consisted of Pahang and Johor individuals. The polymorphic loci (P) for Johor Baru were 5.56%, Penang 16.70%, Selangor and Pahang 22.2%. Nei’s H values are respectively 0.018, 0.060, 0.050 and 0.051. Similarly the Shannon index diversity values are respectively 0.028, 0.089, 0.085 and 0.087. The lowest genetic distance (0.0997) was between Penang and Selangor populations, while the highest (0.613) was observed between Penang and Pahang populations. AMOVA shows low genetic differentiation among individuals within populations and that 85.6% of total genetic variance was among individuals between populations. This was also indicated by FST statistic of 0.8562. The gene flow between populations was low with Nm of 0.042, and Mantel’s test indicated a significant correlation between genetic distance and log geographic distance (P < 0.05 from 10,000 randomizations). In conclusion the Penang and Selangor fly populations are similar genetically, compared to the other populations.