Isozyme evidence for three sibling species in the Anopheles sundaicus complex from Indonesia

Abstract

Electrophoretic studies of isoenzymes in three chromosomally distinct forms (A, B and C) of the mosquito Anopheles sundaicus Theobald (Diptera: Culiciae) were undertaken on wild samples collected from six geographically isolated populations in Indonesia. Analyses of 12 enzyme systems comprising 15 loci revealed significant allelic variations, genetic polymorphism, within and among the populations of the An. sundaicus complex. Phylogenetic dendrograms produced by analysis using the Biosys-1 program based on UPGMA methods show that all the populations of form A fall into one cluster, which is closely related to the form C cluster, whereas the populations of form B belong to a more distinct cluster. Allelic frequency and Wright's F statistics of Mpi (mannose phosphate isomerase) are sufficient to identify individuals of each cytological form. This isozyme data correlates with our previous cytological evidence for the existence of three isomorphic species within the taxon An. sundaicus in Indonesia. These three species of the An. sundaicus complex were found together sympatrically at one locality, Asahan in North Sumatra.

Speciation and phylogeography of the Southeast Asian Anopheles sundaicus complex

“…Subsequently, approaches in genetics using different markers established the presence of a species complex in distinct geographic areas of Southeast Asia. The presence of three genetic forms (A, B and C) in Indonesia (Sumatra and Java) and in Thailand was demonstrated by cytogenetics, and confirmed by isozyme analysis (Sukowati et al, 1996(Sukowati et al, , 1999 (Table 1). Form A was found in all study sites in both countries.…”

“…The Indonesian lineage does not correspond specifically to either form B or C of Sukowati et al (1996Sukowati et al ( , 1999 in Sumatra and its status in relation to form D (Nanda et al, 2004;Alam et al, 2006) on Nicobar Island is uncertain. Form D was recognised through cytogenetics and ITS2 analysis.…”

“…to compare the cytogenetic identification of two forms (B and C) (Sukowati et al, 1996(Sukowati et al, , 1999) with molecular profiles. However, the small number of specimens limited the interpretation.…”

“…This is not the first time that such incongruence has been noted in Anopheles species (Besansky, 1999). The presence of chromosomal inversions was correlated with the salinity of habitats where larvae of forms B and C were collected (Sukowati et al, 1996(Sukowati et al, , 1999. Chromosome inversions in members of the A. gambiae complex are known to be related to environmental adaptation (White, 1973;Coluzzi, 1982;Toure et al, 1998), but not necessarily linked to speciation (Rieseberg, 2001).…”

“…Form C was restricted to Asahan in northern Sumatra. Asahan was the only site where all three cytotypes occurred in sympatry (Sukowati et al, 1996(Sukowati et al, , 1999. In addition, molecular approaches identified two allopatric species based on two mitochondrial markers, cytochrome oxidase I (COI) and cytochrome b (Cyt-b) (Dusfour et al, 2004b) (Table 1).…”