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New insights into the taxonomy and evolutionary process of bamboo bats of genus Tylonycteris in Southeast Asia with the description of a new species to science

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An international team of scientists including members of the Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology (IEBR-VAST), the Hungarian Natural History Museum, the Natural History Museum of Geneva (Swiss), and the Muséum national d'Histoire naturelle (Paris, France) published results of a study entitled "Comparative phylogeography of bamboo bats of the genus Tylonycteris (Chiroptera, Vespertilionidae) in Southeast Asia" in the European Journal of Taxonomy 274: 1-38.

Prior to this study, bamboo bats of the genus Tylonycteris Peters, 1872 in Southeast Asia, have traditionally been classified into two wide-ranging species, T. pachypus (Temminck, 1840) and T. robustula Thomas, 1915, with several subspecies recognised for each taxon

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Fig. 1. The distribution range (shade) of T. pachypus (A) and T. robustula (B) and type localities of their recognised subspecies in Asia; and the study area of this study in Southeast Asia (small rectangle)

In this study, the comparative phylogeographic analyses based on two mitochondrial and seven nuclear genes, combined with multivariate morphological analyses, show that these species actually represent cryptic species complexes that share a similar biogeographic history in three major regions, i.e., Sundaic islands (Java and Borneo), southern Indochina, and northern Indochina. The molecular dating estimates suggest that Pleistocene climatic oscillations and sea level changes have repeatedly isolated ancestral populations of Tylonycteris spp. in distant bamboo forest refugia. Accordingly, a new taxonomic systematic of the genus Tylonycteris in Southeast Asia is proposed. For instance, the species names T. pachypus and T. robustula are considered for populations found restrictedly from the Sundaland, where the type specimens were collected (Fig. 2), two following species names previously used for populations occurring in mainland Southeast Asia are revalidate: the first is T. fulvida should be applied to continental bats of the T. pachypus complex; the second is T. malayana should be applied to populations of the T. robustula complex found in Peninsular Malaysia, southern Indochina, and northern India. In contrast, all bats of the T. robustula species complex endemic to northern Indochina should be included in the new species T. tonkinensis Tu, Csorba, Ruedi & Hassanin sp. nov. (Fig. 3).  

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Fig. 2. Distribution range of recorgnised taxa within two species cryptic complexes

Systematic description
Tylonycteris tonkinensis Tu, Csorba, Ruedi & Hassanin sp. nov.
Etymology: The specific epithet refers to the current restricted occurrence of the new species in north-eastern Laos and northern Vietnam (Fig. 2). The Vietnamese portion of this region was previously called “Tonkin” during the Nguyễn dynasty and French colonial era (from the 19th to the mid-20th centuries) to separate it from the country’s centre (Annam) and southern regions (Cochinchina). The proposed English name is “Tonkin’s greater bamboo bat” and the proposed Vietnamese name is ‘Dơi ống tre Bắc Bộ’.

Holotype: VIETNAM:  Copia Nature Reserve, Co Ma commune, Thuan Chau District, Son La Province. Paratypes: LAOS: Hat Hin, Nam Sing River, Phongsaly Province. VIETNAM: Hang Kia, Pa Co Nature Reserve, Hoa Binh Province.
Referred material: Cho Don (Bac Kan Province) and Na Hang Nature Reserve (Tuyen Quang Province)

Description
Tylonycteris tonkinensis is a small-size species with a forearm length of 25.1–27.8 mm and the greatest skull length of 11.91–12.60 mm). The head is dorsoventrally very flattened. Pelage coloration is relatively variable, more or less golden red at the base of the dorsal fur, to dark brown near the tips of the dorsal hairs, and lighter golden brown on the underparts (Fig. 3). The ears have a triangular shape, with broadly rounded tips. The tragus is short and blunt. The wing membranes are dark brown. The base of thumbs and soles of hind feet have fleshy pads (Fig. 3). These morphological features are thought to be adaptations for roosting in small cavities with smooth surfaces such as the internodes of bamboo stalks or narrow crevices in trees and rocks. 

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Fig. 3. Morphological characteristics of T. tonkinensis Tu, Csorba, Ruedi & Hassanin sp. nov. (holotype, IEBR-VN11-0055). Head profiles, ventral and dorsal views, fleshy pads at the base of the thumb and on the sole of the foot, and different views of the skull (dorsal, ventral and lateral). Scale = 10 mm.

Ecology and habitat
Like other species of Tylonycteris, T. tonkinensis sp. nov. is associated with woody bamboo groves. The new species is usually found in sympatry with the smaller species T. fulvida.

Distribution: Currently, the new species is known to occur in north-eastern Laos and northern Vietnam only (Fig. 2).

Conservation status: Recently, little is known regarding current trend of T. tonkinensis. However, like many other wildlife found in sympatry in the region, this taxon might be vulnerable mainly due to the high rates of habitat loss and growing exploitation of natural resources. In this context, more comprehensive researches are needed to be carried out in order to strengthen conservation actions that ensure human well-being, local bats and other wildlife can be maintained.
Find out more: http://dx.doi.org/10.5852/ejt.2017.274 (free access)

Translated by: Dr. Vuong Tan Tu
Link to Vietnamese version

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