ABSTRACT
Stewartia sichuanensis is a rare plant species of Theaceae and is endemic to China. Its distribution area is highly restricted, and genomic information is extremely limited. The present study reports the first complete chloroplast of S. sichuanensis. The chloroplast genome length was 158,903 bp, with a GC content of 37.3%. The chloroplast genome was comprised of an 87,736 bp long large single copy (LSC), an 18,435 bp long small single copy (SSC), and two copies of inverted repeat (IR) regions of 26,366 bp. It contained 129 genes, including 85 encoding, 36 transfer RNA, and eight ribosomal RNA genes. The phylogenetic analysis suggested that S. sichuanensis was closely related to S. laotica and S. pteropetiolata.
ABSTRACT
The synthesis of evolutionary biology and community ecology aims to understand how genetic variation within one species can shape community properties and how the ecological properties of a community can drive the evolution of a species. A rarely explored aspect is whether the interaction of genetic variation and community properties depends on the species' ecological role. Here we investigated the interactions among environmental factors, species diversity, and the within-species genetic diversity of species with different ecological roles. Using high-throughput DNA sequencing, we genotyped a canopy-dominant tree species, Parashorea chinensis, and an understory-abundant species, Pittosporopsis kerrii, from fifteen plots in Xishuangbanna tropical seasonal rainforest and estimated their adaptive, neutral and total genetic diversity; we also surveyed species diversity and assayed key soil nutrients. Structural equation modelling revealed that soil nitrogen availability created an opposing effect in species diversity and adaptive genetic diversity of the canopy-dominant Pa. chinensis. The increased adaptive genetic diversity of Pa. chinensis led to greater species diversity by promoting co-existence. Increased species diversity reduced the adaptive genetic diversity of the dominant understory species, Pi. kerrii, which was promoted by the adaptive genetic diversity of the canopy-dominant Pa. chinensis. However, such relationships were absent when neutral genetic diversity or total genetic diversity were used in the model. Our results demonstrated the important ecological interaction between adaptive genetic diversity and species diversity, but the pattern of the interaction depends on the identity of the species. Our results highlight the significant ecological role of dominant species in competitive interactions and regulation of community structure.
ABSTRACT
The complexity of global biodiversity in the tropical Indochina Peninsula and subtropical China bioregions has fascinated biologists for decades, but little is known about the spatiotemporal patterns in these regions. Accordingly, the aims of present study were to investigate the evolutionary and distribution patterns of Engelhardia in these regions and establish a model for examining biogeographic patterns and geological events throughout the tropical Indochina Peninsula and subtropical China. The effects of geological events occurring in the area between the Indochina Peninsula and subtropical China bioregions on the two trees species (i.e., E. roxburghiana and E. fenzelii) were evaluated. A robust phylogenetic framework of 884 individuals from 79 populations was used to generate time-calibrated cytoplasmic and nuclear phylogenetic frameworks based on cpDNA, nrDNA, and nSSR data, respectively. When considered along with ancestral area reconstructions, the genetic data were also used to assess and reconstruct the species' population genetic structure and diversity. These analyses yielded important information about the (1) historical distribution relationships between the tropical and subtropical flora of China; (2) effects of the East Asian summer monsoon (EASM) on the evolutionary history of Asia's plants; and (3) importance of biogeography in conservation planning. Although cytoplasmic-nuclear discordance indicated cpDNA and nrDNA were subject to distinct evolutionary mechanisms that reflected respective evolutionary histories of the plastid and nuclear genomes of prior demographic and biogeographic events. The tropical elements of Engelhardia occupied the Indochina Peninsula during the early Eocene, whereas the subtropical elements were transformed from the tropical elements during Miocene cooling and the onset of the EASM at the Oligocene-Miocene boundary, intensified during the late Miocene and Pliocene, facilitating the transformation of Engelhardia from the tropical Indochina Peninsula to subtropical China. Demographic history provided insights into prominent planning frameworks in conservation biology, namely that subtropical China functioned as a refugium during past climate oscillations and will continue to serve in this capacity in the future.
Subject(s)
Biodiversity , Plants , China , DNA, Chloroplast , Humans , Indochina , Phylogeny , PhylogeographyABSTRACT
In this study a brinzolamide drug-resin ophthalmic thermosensitive in situ gelling system was developed and evaluated. Brinzolamide was combined with ion exchange resins to prolong the retention time of drugs in the eye and to reduce ocular and systemic side effects. Poloxamer F127 was used as gelling vehicle in combination with carbopol 934P, which acted as a viscosity-enhancing agent. They were prepared using the cold method. The optimized formulation exhibited a sol-gel transition at 33.2±1.1°C with pseudoplastic flow behavior. This formulation was stable and nonirritant to rabbit eyes. In vitro release studies demonstrated diffusion-controlled release of brinzolamide from the combined solutions over a period of 8 h. In vivo evaluation (the elimination of brinzolamide through tears and absorption of brinzolamide in aqueous humor) indicated that the solution combination was better able to retain the drug than commercial preparations. Thus this formulation is safe for ophthalmic use and significantly increases brinzolamide bioavailability in aqueous humor.
