Niphadomimus

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 : 168-169

Niphadomimus temporal phylogeography

The most significant phylogeographic result is the detection of the relatively robust Niphadomimus tree with the sister group relations between the Qinling species N. merope sp. n. and the rest of the genus. Similarly to the genus Niphadomimus , numerous other Animalia clades are restricted in their distribution to the highlands of the southeastern edges of the Tibetan Plateau ( Fig. 14 , Favre et al. 2014), i.e. the eastern Himalayas ( Nepal, Sikkim, Bhutan and Arunachal Pradesh), the Hengduan mountains (northern Myanmar and the adjacent parts of SW China) and the Qinling mountain range (Shaanxi). The Red Panda ( Ailurus fulgens Cuvier ) presently ranges longitudinally through Sichuan, Yunnan, northern Myanmar, Bhutan, Sikkim and Nepal and unlike Niphadomimus it seems to be a recent inhabitant resulting from a post-glacial range expansion by this presumably highly mobile mammalian species (Le et al. 2005). The presumably less mobile Asian shrew-like moles ( Uropsilus Milne-Edwards ) have a distribution more closely matching that of Niphadomimus and exhibit a robust phylogeographic structure with their single sampled Qinling population nested deeply inside the Hengduan clade ( Wan et al. 2013). The latter is not similar to the Niphadomimus pattern, where the Qinling species N. merope sp. n. forms the sister group to the rest from Hengduan ( Fig. 14 ). The comparison of the Niphadomimus temporal phylogeography with the aforementioned examples should be done with caution, since they also rely on an a priori DNA substitution rate taken as the main dating source, which introduces a significant element of circular logic.

Only a few works on the low dispersing wingless weevils distributed in temperate mountains are detailed enough to permit adequate comparison with the reported Niphadomimus phylogeographic results. Among them, Meregalli et al. (2013) offers the best reference point being the most comparable in size and nature to the DNA data, as well as dealing with a genus of high altitude wingless weevils distributed along the southern edge of the last glacial maximum in South Europe. The authors utilized 775 nt of 18 CO1 haplotypes representing seven Dichotrachelus Stierlin species sampled on the southern slopes of the Alps. They reported the mean interspecies p - distance in the range of 11.0–16.7%, which by using the 2.1% MY -1 sequence divergence rate dated the speciation events between 6.5 MY and 3.3 MY, i.e. from later Miocene to late Pliocene. They concluded that instead of being the main force behind the Dichotrachelus phylogeographic structure, the Quaternary glaciation cycles are primary responsible for the highly fragmented present day high-altitude species distribution. For the most part the conclusions on Dichotrachelus phylogeography match those for Niphadomimus , and conceivably suggest a common pattern, even though both studies used a markedly different sequence divergence rate for the same CO1 gene (2.1% MY - 1 in Meregalli et al. 2013, as compare to 3.6% MY -1 adopted here).

Regardless of the uncertainties about the exact order of the bifurcation points in the ( Niphadomimus except N. merope sp. n.) clade (compare Figs. 12 and 13 ), temporal analysis places all events leading to the origin of all presently recognised Niphadomimus species well before Pleistocene (the last dichotomy between N. celaeno sp. n. and N. strerope sp. n. taking place in mid Pliocene at about 3.64 MY; Fig. 13 ). These results add to the growing body of evidence denying the Pleistocene repeated glaciation and aridification effects of being the most important stimulus to the present day speciation. The mtDNA distance-based interpretation of Niphadomimus species diversification agrees well with the similar conclusions reached based on fossil records for the North American amphibians and reptiles ( Holman 1995: 28) and mammals ( Barnosky 2005). These similarities further corroborate the hypothesis that the Quaternary climatic changes do not represent the main driving force of the presently observed species diversity ( Rull 2008). These Niphadomimus temporal results, however, should be taken only tentatively, since the generic tree ( Fig. 13 ) is likely lacking many more extant branches for numerous hypothetically undetected species. If true, they will be likely inserted among those already known and some of them originating more recently, than what is presently hypothesised.

Figures

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 13. Ultrametic time tree of the Chinese species of the genus Niphadomimus using BEAST software to analyse 658bp of the “barcoding” mtDNA calibrated at a rate of 0.018 substitutions/site/MY. Numbers at nodes and on the scale below are million years before present (MY). Node bars represent a 95% confidence interval of the age estimate. Epoch dating after Cohen et al. (2013). Alternating snowflake and sun symbols denote Pleistocene climatic fluctuations.

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).