Insects are the most speciose group of animals, but the phylogenetic relationships of many major lineages remain unresolved. We inferred the phylogeny of insects from 1478 protein-coding genes. Phylogenomic analyses of nucleotide and amino acid sequences, with site-specific nucleotide or domain-specific amino acid substitution models, produced statistically robust and congruent results resolving previously controversial phylogenetic relations hips. We dated the origin of insects to the Early Ordovician [~479 million years ago (Ma)], of insect flight to the Early Devonian (~406 Ma), of major extant lineages to the Mississippian (~345 Ma), and the major diversification of holometabolous insects to the Early Cretaceous. Our phylogenomic study provides a comprehensive reliable scaffold for future comparative analyses of evolutionary innovations among insects.
Five species of the genus Labiobaetis (Baetidae) are recognized from China based on mature nymphs, including a new species, Labiobaetis ancoralis n. sp. and a new combination, Labiobaetis mustus (Kang & Yang) n. comb. The new species differs from L. multus (Müller-Liebenau) and L. pulchellus (Müller-Liebenau & Hubbard) by the spatulate submarginal setae on labrum and the apical segment of maxillary palpus with a pronounced excavation near apex. Imago stage of L. mustus (Kang & Yang) n. comb. is described for the first time based on male and female imagoes reared from nymphs, which can be distinguished from other known imagoes of Labiobaetis by the color pattern of abdominal terga and hind wing having a tiny vestigial costal process. All Oriental species previously transferred to Pseudocloeon are reassigned to Labiobaetis in the present paper. An identification key is provided to the known mature nymphs of Oriental Labiobaetis species.
To understand the global distribution patterns of litter-dwelling thrips, a total 150 leaf litter samples were collected from 6 natural reserves located in three climatic regions, temperate, subtropical and tropical. The results showed the relative abundance of Thysanoptera was over 3.0% in 4 natural reserves from subtropical and tropical zone, and reached 5.9% in one tropical reserve, only less than Acarina and Collembola. In contrast it was only 0.3% in the warm temperate natural reserves, and no thrips were collected in a mid temperate reserve. The order on the average species numbers per plot of litter thrips was tropic > subtropics > temperate (n=25, p<0.05). Mean density of litter thrips per plots in the tropics and subtropics was significantly higher than that in the temperate region (n=25, p<0.05), but the average density was not significantly different between tropical and subtropical zones (n=25, p>0.05). The diversity of litter thrips in the tropics and subtropics was much higher than that in the temperate area based on comparsions of Shannon-Wiener diversity index (H'), Pielou eveness index (J), and Simpson dominance index (D). All of these results indicated that litter-dwelling thrips lived mainly in tropical and subtropical regions; meanwhile, species number and relative abundance increased with decreasing latitude.
Litter-dwelling thrips are an important component of soil macroinvertebrates in tropical and subtropical regions. However, little is known about assemblage composition, seasonal abundance and vertical distribution of litter-dwelling thrips. A survey of forest litter-dwelling thrips and other soil macroinvertebrates was conducted in an urban forest remnant at Guangzhou, China during 2004-2005 and 2008-2009. A total of 835 Tullgren samples were collected during the study. Thysanoptera constituted 6.5% of total litter-dwelling macroinvertebrate individuals extracted, representing three families, 19 genera, and 25 species. Psalidothrips ascitus Ananthakrishnan (Thysanoptera: Phlaeothripidae) and Hyidiothrips guangdongensis Wang, Tong and Zhang represented 78.5% of all individuals of litter-dwelling thrips during the survey. Numbers of species and density of leaf-litter thrips fluctuated between different months. Density of litter thrips increased from March until October, reaching a maximum of 41.1 individuals/m2 followed by a decrease. In January and February only a few larval thrips were present. Species diversity gradually increased from July (four species) to December (10 species), and then declined rapidly. The vertical distribution showed that the leaf-litter thrips species richness and abundance decreased significantly with soil depth; they were found only in the litter layer and upper soil layer (0-5 cm in depth) and were entirely absent in deeper soil layers. The results suggest that litter-dwelling thrips are a common group of litter invertebrates with high species diversity in subtropical regions. These urban forest remnants should be given special consideration in forest conservation planning, because of their significance as refugia for the litter invertebrate assemblages, especially for leaf-litter thrips.
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