Abstract
The mountains of southwest China are one of the hot spots of biodiversity in the world. However, the high-altitude fauna that inhabit these mountains remain a mystery. In this study, the species diversity of the aphids of the genus Cinara from the high-altitude coniferous forests was first assessed, and then the processes and the mechanisms of speciation were discussed. Three hundreds and four aphid samples that contained 3040 individuals were collected during fourteen field surveys. The molecular clusters derived from the DNA barcodes were used to explore the species diversity. Notably, the aphid alpha-diversity was high, with as many as 94 candidate species, and furthermore, 86.2% of the species collected had not been previously recorded. The centers of aphid species richness corresponded to the distributional pattern of the diversity of the host conifer plant species. The divergence time revealed that following the uplift of the Qinghai-Tibetan Plateau during the Pleistocene, the changes in the climate, ecology and host habitats were likely the most important factors that drove the rapid process of evolutionary radiation in the aphids. Our findings revealed the high species diversity of the aphids with DNA barcoding.
Highlights
Of Cinara have disjunctive distributions and different allopatric populations because of the specific geographic ranges of the host plants
The dispersal ability of species of Cinara is limited because of the high weight to wing length ratio[14], and some species are even recorded without winged morphs[15]; the absence of dispersal ability might accelerate the genetic diversification of species in an area with such complex topography[16]
These sequences were heavily biased toward A and T nucleotides, averaging 39.1% for T, 14.9% for C, 35.6% for A and 10.4% for G nucleotides. Both the clustering method based on the NJ tree and the genetic distances and the Automatic Barcode Gap Discovery (ABGD) method identified 94 candidate species from the 304 barcodes (Table S1)
Summary
Of Cinara have disjunctive distributions and different allopatric populations because of the specific geographic ranges of the host plants. Previous investigations on aphids in the high-altitude zones of the mountains of southwest China are rare. We first assessed the aphid diversity and focused on the species in the coniferous forests of the high-altitude zones with field surveys in the last ten years, during three targeted expeditions in 2012–2013. The aims of the research were as follows: 1) to identify the genetic diversity of the aphids and to determine the ratio of described to undescribed species, 2) to describe the distribution patterns of the species and to assess the roles of two factors (elevation and host plants) on the patterns of distribution, and 3) to estimate evolution of the host associations within the aphid genus and to discuss the processes and mechanisms of speciation for the aphid genus in this region
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