Geographic distribution and genetic compatibility among six karyotypic forms of Anopheles peditaeniatus (Diptera: Culicidae) in Thailand

Fifty-three isolines of Anopheles peditaeniatus were established from individual wild-caught females collected from cow-baited traps in 17 provinces of Thailand. Three types of X (X-1, X-2, X-3) and 6 types of Y (Y-1, Y-2, Y-3, Y-4, Y-5, Y-6) chromosomes were determined based on different amounts of major block(s) of heterochromatin. These sex chromosomes comprised 6 karyotypic forms designated as Forms A (X-3, Y-1), B (X-1, X-2, X-3, Y-2), C (X-3, Y-3), D (X-1, X-2, X-3, Y-4), E (X-1, X-2, X-3, Y-5) and F (X-2, X-3, Y-6). Form F is a new metaphase karyotype discovered in this study and is commonly found in all regions. Form A was found only in Lampang province, whereas Form E is widespread throughout the country. Forms B, C and D were obtained from the northern, northeastern, western and southern regions. Crossing experiments among the 11 isoline colonies representing the 6 karyotypic forms of An. peditaeniatus indicated genetic compatibility yielding viable progenies and complete synapsis of salivary gland polytene chromosomes through to the F-2-generations. The results suggested the conspecific nature of these karyotypic forms which were further supported by very low intraspecific variation (genetic distance = 0.000-0.003) of nucleotide sequences in ribosomal DNA (ITS2) and mitochondrial DNA (COI and COII).