Paraboeazunyiensis (Gesneriaceae), a new species from north Guizhou, China.

A new lithophytic species, Paraboeazunyiensis T.Deng, F.Wen & R.B.Zhang (Gesneriaceae), inhabiting Karst rocks in northern Guizhou, China, is introduced and depicted in this study. It bears a resemblance to P.crassifolia (Hemsl.) B.L. Burtt, yet is distinguishable by its shorter filaments and staminodes, triangular ovate calyx segments, and ovaries surpassing the styles in length. Moreover, the phylogenetic tree constructed from nuclear DNA (ITS) and plastid DNA (trnL-F) data firmly support the differentiation of this novel species from P.crassifolia.

Paraphlomis kuankuoshuiensis (Lamiaceae), a new species from the limestone areas of northern Guizhou, China.

Paraphlomis kuankuoshuiensis (Lamiaceae), a new species found in the limestone areas of northern Guizhou, China, is described and illustrated in this paper. Based on its tubular-campanulate calyx, this taxon should be a member of sect. Paraphlomis Prain. The new species resembles P. patentisetulosa C.Y. Wu & H. W. Li, P. hispida C.Y. Wu, and P. hirsutissima C.Y. Wu & H.W. Li, but differs from these three taxa in the following aspects: the stems are very short (<7 cm), with one or two short internodes, giving the impression of having a tuft of basal leaves; it has sparsely setose hairs on the outer surface of the calyces and short fruiting calyces. The florescence, fruit period, habitat, and the geographical distribution of P. kuankuoshuiensis are also quite different from the three closely related species.

Evolutionary history and complementary selective relaxation of the duplicated PI genes in grasses.

Gene duplication plays an important role in the evolution of organisms by allowing functional innovation and the divergence of duplicate genes. Previous studies found two PI-like genes in grass species, suggesting functional divergence between the paralogous copies. Here, we reconstructed the evolutionary history of two PI genes from major lineages of grasses and other monocot species, and demonstrated that two PI genes (PI1 and PI2) arose from a whole genome duplication that occurred in a common ancestor of extant grasses. Molecular evolutionary analyses at the family and tribal levels found strong purifying selection acting on two genes in grasses, consistent with the conserved class B function of the PI genes. Importantly, we detected different patterns of selective relaxation between the duplicated PI genes although no signature of positive selection was found. Likelihood ratio tests revealed that the ω ratio for M domain is significantly higher in PI1 than in PI2 but that for K domain is significantly higher in PI2 than in PI1. These findings imply that complementary selective relaxation occurs in two PI genes after duplication, and provide additional molecular evidence for the subfunctionalization of the duplicated PI genes in grasses.

Contrasting population genetic structure and gene flow between Oryza rufipogon and Oryza nivara.

The cross compatible wild relatives of crops have furnished valuable genes for crop improvement. Understanding the genetics of these wild species may enhance their further use in breeding. In this study, sequence variation of the nuclear Lhs1 gene was used to investigate the population genetic structure and gene flow of Oryza rufipogon and O. nivara, two wild species most closely related to O. sativa. The two species diverge markedly in life history and mating system, with O. rufipogon being perennial and outcrossing and O. nivara being annual and predominantly inbreeding. Based on sequence data from 105 plants representing 11 wild populations covering the entire geographic range of these wild species, we detected significantly higher nucleotide variation in O. rufipogon than in O. nivara at both the population and species levels. At the population level the diversity in O. rufipogon (Hd = 0.712; theta (sil) = 0.0017) is 2-3 folds higher than that in O. nivara (Hd = 0.306; theta (sil) = 0.0005). AMOVA partitioning indicated that genetic differentiation among O. nivara populations (78.2%) was much higher than that among O. rufipogon populations (52.3%). The different level of genetic diversity and contrasting population genetic structure between O. rufipogon and O. nivara might be explained by their distinct life histories and mating systems. Our simulation using IM models demonstrated significant gene flow from O. nivara to O. rufipogon, indicating a directional introgression from the annual and selfing species into the perennial and outcrossing species. The ongoing introgression has played an important role in shaping current patterns of genetic diversity of these two wild species.