Niphadomimus species

Grebennikov, Vasily V., 2014, DNA barcode and phylogeography of six new high altitude wingless Niphadomimus (Coleoptera: Curculionidae: Molytinae) from Southwest China, Zootaxa 3838 (2), pp. 151-173 : 167

Niphadomimus species delimitation, generic diversity and distribution

The availability of DNA data with their superior lineage resolution power, as compared to morphological characters only, tends to intensify, rather than to clarify, the long-recognised uncertainty on species limits ( Darwin 1859: 44). When delimiting species among the well-resolved and closely related lineages, it becomes a necessity to make an unambiguous reference as to which species concept has been used ( Funk & Omland 2003). In the present work the “phylogenetic species concept” of Mishler & Theriot (2000) is followed, though it likely just one of the aspects of the more inclusive “unified” species concept of De Queiroz (2007). For most of the analysed Niphadomimus it is irrelevant which species concept is used, except for two specimens #2439 and #4429 presently recognised as the only two known representatives of N. alcyone sp. n. Under a different “species concept” it could have been possible, or perhaps necessary, to designate each of them as a separate species, since the specimens are morphologically dissimilar (compare Figs. 1 and 2 ), have uncorrected genetic p-distance of 5.94% ( Fig. 12 ) and are allopatric ( Fig. 14 ). Moreover, both specimens exhibit uncorrected DNA p-distance of 6.24% and each qualifies for a separate Barcode Index Numbers, recently suggested as a rough species approximation (Ratnasingham & Herbert 2013). Adopting the “phylogenetic species concept” of Mishler & Theriot (2000) permits grouping both specimens into the same nominal species, which can be tested again later, when more specimens of this clade become available for analysis.

It is highly likely that even after the present study, the genus Niphadomimus will for years or decades remain an inadequately known group of “rare” and undersampled organisms. Such is the fate for many, if not the majority of, invertebrate lineages, also quite often irrespective of their economic significance. Consider that among 278 Agrilus ( Coleoptera : Buprestidae ) species-group taxa native to East Asia, 74 (26.6%) were new to science ( Jendek & Grebennikov 2011), while this genus harbours Agrilus planipennis Fairmaire , the infamous Emerald Ash Borer, the agent of “the most costly biological invasion by an exotic forest insect to date” ( Herms & McCullough 2014). Therefore, and similarly to any poorly known invertebrate group, the true number of Niphadomimus species is likely in time, if not in order of magnitude, greater than the present count of eight. This estimation is made based on the following five observations: (1.) the present paper quadruples the number of species from two to eight and increases the number of known specimens from two to exactly 100; (2.) except for N. electra sp. n. and N. maia sp. n., all other species are known by three or less specimens; (3.) with the exceptions N. alcyone sp. n. (but see its species concept above) and perhaps N. nigriventris , all Niphadomimus species are known only from the type localities; (4.) one of two species sampled in relatively great numbers, N. maia sp. n., was detected in a single sample among three taken in relative proximity to each other; (5.) in two of five sampled areas (Chinese localities, Fig. 14 ) two sympatrically occurring Niphadomimus species were detected. Such elevated species number estimations were even exceeded for the Middle American litter inhabiting weevil genus Theognete Champion , which in a single publication ( Anderson 2010) multiplied its numbers from two syntypes to 94 species, and still counting (R.S. Anderson, pers. comm.). All these facts strongly suggest that Niphadomimus species are normally restricted in their distribution to a single high-altitude area, not necessarily allopatric, rarely sampled even when targeted for and, therefore, numerous new species can be expected to inhabit other suitable habitats along the great wrinkled arc formed by the south-eastern edge of the Tibetan Plateau ( Fig. 14 ) and stretching for at least 2500 km from central Nepal to Qinling Mt. Range in Shaanxi, China.

Figures

FIGURE 1. Niphadomimus alcyone sp. n., holotype, female, #2493. A-D: habitus; E: apical part of basal hemisternite 9 (“coxite”) and much smaller apical cylindrical hemisternite 9 (=“stylus”); F: sternites 8 and IX; G: sternite 8 (sternite 9 in the background).

FIGURE 2. Niphadomimus alcyone sp. n., paratype, female, #4429. A–D: habitus; E: spermatheca.

FIGURE 12. Bayesian inference phylogram positioning monophyletic Niphadomimus among other analysed Molytinae genera using the 658bp of the DNA barcoding CO1 gene fragment. Niphadomimus and the three other genera currently assigned to Typoderini are in red. Values at nodes are posterior probabilities; clades supported with less than 0.5 posterior probabilities are ignored and collapsed. The tree is rooted on Graptus circassicus (Entiminae; not shown). Habitus images are denoted by abbreviated genus and species letters on the same level with the terminal and are not to scale.

FIGURE 14. Known distribution of the genus Niphadomimus in Nepal (two species) and China (six species). The overlaying topology illustrates sister-group relations between the easternmost N. merope sp. n. from the Qinling Mt. Range and the unresolved rest of the genus. Base map generated using the on-line SimpleMappr tool (Shorthouse 2010).