Pedesta similissima (Devyatkin, 2002) syn. n. (Fig. 26) Thoressa similissima Devyatkin, 2002: 127, type locality: Thanh Hoa Province, northern Vietnam. = Pedesta submacula (Leech, 1890). Note. Re-examination of the type specimens of Pedesta similissima (Fig. 26, Fig. 27) shows that both the external and genitalic characters are identical to those of P. submacula (Figs. 9–17, Fig. 18), suggesting the two species are conspecific. The analysis of COI gene sequences confirmed this point (Fig. 1). Devyatkin (2002) mistook P. rubella for P. submacula and thus resulted in this synonym. Distribution. Based upon the specimens examined, data from literature (e.g. Ikeda et al. 2001; Wang & Tang 2012; Chen 2016; Zhu et al. 2017) and results of the present study, a distribution map of Pedesta submacula and P. rubella is provided (Fig. 28). It shows that P. submacula is widely distributed from northwestern Qinling Mountains through the southern mainland China to central Vietnam, but in southern Guangxi and northern Vietnam, it is replaced by P. rubella. Both species have not been found sympatrically so far. Although P. submacula is separated by P. rubella into two groups, specimens from China and Vietnam are not distinguishable by stable external or genitalic characters. Therefore, the Vietnamese population of P. submacula is not considered a separate subspecies. Geographical gaps between populations of species caused by natural factors are not rare in the butterfly fauna of Indochina. Disjunctions observed differ in their distance and direction. The majority of disjunctions in the Sino- Himalayan ranges has been observed between populations of northern Vietnam (e.g. Hoang Lien Son mountains) and northern part of central Vietnam (northern Truong Son ridge), and populations of W. China and E. Himalayas. During the last two decades, detailed studies of the Vietnamese butterfly fauna have showed disjunctions in representatives of different taxonomical groups, e.g. Pazala Moore, 1888 (Hu et al. 2018, 2019), Devyatkinia Monastyrskii & Uémura, 2016, Lethe Hübner, 1819 (Lang & Monastyrskii 2016), Ypthima Hübner, 1818 (Monastyrskii & Holoway 2013), etc. Sometimes these disjunctions may be filled with the populations of closely related species, showing the characters of vicariance, the existence of refugiums and the speciation processes occurred in this area. Judging from the modern distribution pattern of Pedesta submacula (Fig. 28), it is very possible that the Vietnamese population of this species was separated from the main distribution range in the course of geological and climatic changes, and then, it adapted to new conditions and lost contact with the main populations; this resulted in the formation of a new taxon, viz. P. rubella. Such a distribution pattern may suggest that the range of this species was larger in the past, when the corresponding habitats shifted down the slopes during cooler and drier glacial period. During the warmer eras, the species may become isolated when these habitats receded to higher altitudes. Such cycles of habitat changes may have also led to varying degrees of divergence in some groups of butterflies. At present, this scenario presents a suitable explanation for range disjunctions of many separate montane butterfly taxa in Vietnam.

Published as part of Li, Meng, Monastyrkii, Alexander L., Kolesnichenko, Kirill A., Liu, Zihao, Xue, Guoxi, Long, Jifeng & Tang, Huaxing, 2020, Morphological and molecular characters reveal the status of Pedesta rubella (Devyatkin, 1996) stat. n. and P. similissima (Devyatkin, 2002) syn. n. (Lepidoptera, Hesperiidae), pp. 217-231 in Zootaxa 4743 (2) on pages 224-229, DOI: 10.11646/zootaxa.4743.2.5, http://zenodo.org/record/3687821