Twenty-one new species of the Simulium (Gomphostilbia) asakoae species group (Diptera, Simuliidae) in Thailand, with their genetic relationships

Abstract

Females and males reared from pupae, their pupal exuviae and cocoons, and mature larvae of the Simulium (Gomphostilbia) asakoae species group from various localities in Thailand were morphologically examined. A total of 25 species was identified, including two of four known species (Simulium asakoae Takaoka & Davies and S. chiangdaoense Takaoka & Srisuka), one newly confirmed species (S. myanmarense Takaoka, Srisuka & Saeung, originally described from Myanmar), one newly transferred species (S. inthanonense Takaoka & Suzuki formerly of the S. ceylonicum species group), and 21 new species. Descriptions of all 21 new species are given, and the first full description of the male of S. inthanonense, together with the revised descriptions of its female, pupa, and larva, is also provided. Keys to identify all 27 members of this species group from Thailand are given for females, males, pupae, and larvae. The genetic relationships of all but one species were resolved using COI gene sequence-based analysis. All 26 species were divided into nine subgroups, I–IX, each consisting of two, one, four, nine, one, three, two, one and three species, respectively.

From bites to barcodes: uncovering the hidden diversity of black flies (Diptera: Simuliidae) in Vietnam

“…The clustering of closely related nominal species in these species groups corresponds with a low level of minimum interspecific genetic distance between them, impeding the efficacy of the COI gene for identification. Previous studies revealed no or very low levels of minimum interspecific genetic divergence in some putative species of black flies, particularly closely related species [ 24 , 28 , 29 , 31 , 71 ] and members of species complexes [ 21 , 72 ].…”

“…Nevertheless, these pairs can be morphologically distinguished from their sister species based on the number of male upper-eye facets and differences in pupae [ 3 , 6 , 7 ]. In the S. asakoae species group in Thailand where there is considerable morphological variation but few COI gene changes, the inference is that some members of the group might have recently diverged from a common ancestor, rendering the use of the COI gene insufficient to discriminate the species [ 31 ]. Previous studies have demonstrated limited differentiation among some members of the S. asakoae species group when using only the COI gene [ 29 , 34 ].…”

“…The group includes species of medical and veterinary importance. Females of most members of this group are structurally similar, rendering morphological identification difficult [ 3 , 6 , 7 , 31 ], particularly when only females are collected from the field [ 32 ]. Previous studies show that species boundaries between certain members of the S. asakoae species group in Malaysia and Thailand are poorly resolved using the COI gene alone [ 33 , 34 ], suggesting the need for a more variable genetic marker.…”

A new species of black fly, formerly cytoform C of the Simulium angulistylum complex (Diptera: Simuliidae), from a high mountain in northeastern Thailand

“…nov. and the S. angulistylum cytoform B (0.69%) that overlapped with intraspecific genetic divergence. No or very low interspecific genetic divergence is not uncommon for tropical black fly species, particularly for members of the subgenus Gomphostilbia (Pramual et al, 2011(Pramual et al, , 2021Pramual & Adler, 2014;Takaoka et al, 2020;Srisuka et al, 2021). Recent DNA barcoding analysis found that 12 species of black flies in Thailand have no genetic differentiation based on their COI sequence (Pramual et al, 2021).…”

“…In the S. epistum species-group, no genetic differentiation was found between S. whartoni and S. cheongi based on COI sequences. Low genetic variation between closely related species could be due to misidentification, incomplete lineage sorting or inadequate phylogenetic signal for the COI sequences because they had possibly diverged from a common ancestor only recently (Takaoka et al, 2020). Thus, more variable molecular markers are needed, such as big zinc finger (BZF) and the elongation complex protein 1 gene (ECP1) that have been successfully used for differentiation of the closely related black fly species in Thailand (Thaijarern et al, 2017;Aupalee et al, 2020).…”