Cytotaxonomy, Morphology and Ecology of the <i>Simulium nobile</i> Species Group (Diptera: Simuliidae) in Thailand

Abstract

The polytene chromosomes of 512 larvae of the Simulium nobile species group collected from 16 stream sites in northern, central and southern Thailand were examined. Band-by- band comparisons relative to the established standard chromosome map for the subgenus Simulium distinguished the 2 species of this group, S. nobile and S. nodosum. The differences are mainly due to the position of the nucleolar organizer, pseudochromocenter, and fixed and polymorphic inversions. S. nobile is a monomorphic species, while S. nodosum is a polymorphic species. The morphology of these taxa is described based on the gill filaments and the color of the antennae and female genitalia. S. nobile is distributed in southern Thailand at low altitudes, whereas the distribution of S. nodosum is in the north at higher altitudes.

DNA barcoding of tropical black flies (Diptera: Simuliidae) of Thailand

“…The relatively long branch connecting these species suggests divergence, in agreement with their chromosomal, morphological and ecological differentiation (Tangkawanit et al . ).…”

Tests of conspecificity for allopatric vectors: Simulium nodosum and Simulium shirakii (Diptera: Simuliidae) in Asia

“…Taiwanese and Thai populations had the nucleolar organizer in the end of IIS, undifferentiated sex chromosomes, and only two autosomal polymorphisms each, one of which (IIIL-1) was shared. The frequency of IIIL-1 was 0.99—nearly fixed—in Taiwan, and an average of 0.28 in Thai populations analyzed by Tangkawanit et al [ 15 ]. The chromosome map of Tangkawanit et al [ 15 ] for IIIL, however, shows the homozygous sequence for the IIIL-1 inversion rather than the claimed standard sequence; in addition, the distal breakpoint is shown as extended by one band beyond the actual breakpoint.…”

“…Larvae were collected by hand into ethanol from five sites in Myanmar, Taiwan, Thailand, and Vietnam (Table 1 ). Additional samples of larvae from Taiwan were collected into 1:3 acetic ethanol for chromosomal comparison with published information [ 15 ]. Habitat characteristics at each collection site were recorded, including altitude, canopy cover, and stream depth, temperature, and width.…”

“…Larval carcasses were deposited in the Clemson University Arthropod Collection. The chromosomes of all 51 larvae (25 females, 26 males) were compared band-for-band with the standard map for the subgenus Simulium [ 33 , 34 ] and with the chromosomes of larvae analyzed by Tangkawanit et al [ 15 ] from nine sites in Thailand.…”

Chromosomal relationships of Simulium suzukii, an Old World member of the Simulium tuberosum species group (Diptera: Simuliidae)

“…The chromosomal similarity is so great that if S. suzukii had not already been formally described morphologically, it could have been designated a cytoform in the S. tani complex, the significance of the fixedinversion di#erences and unique sex chromosomes and autosomal polymorphisms being unknown because of the allopatric nature of the Taiwan population vis a ◊ vis S. tani. Morphologically, the S. tani complex di#ers from other nominal members of the S. tuberosum group in Southeast Asia by having a narrow median sclerite in the male, a pair of short terminal spines in the pupa, and small ventral tubercles in the larva (Tangkawanit et al 2009b). Simulium suzukii shares these features, except ventral tubercles, with the S. tani complex (Takaoka, 1977).…”