Genetic diversity and population structure of Hibiscus aridicola, an endangered ornamental species in dry-hot valleys of Jinsha River

Hibiscus aridicola is an endangered ornamental shrub of the family Malvaceae that is endemic to the dryhot valleys of Jinsha River in southwestern China.This species is a typical plant species with extremely small populations(PSESP).To support and monitor future conservation,develop management measures,and genotype this species,we performed extensive field studies together with genetic analyses.Specifically,we screened eleven microsatellite loci of 69 individuals of H.aridicola from four accessions.The population genetics analyses indicated that H.aridicola possesses high genetic diversity at both the population(0.6962-0.7293)and species level(0.7837)compared to other endemic/endangered species in China.The low differentiation of populations(Fst=0.0971)and the high gene flow between populations of H.aridicola(Nm=2.3236)could be due to its distribution along rivers in the hot-valleys of the Jinsha River and the wind-mediated dispersal of its seeds.Furthermore,the genetic diversity of H.aridicola is slightly positively correlated with geographic distance.Two populations are undergoing a genetic bottleneck,and require more specific attention from conservationists.Additionally,our analyses of the population genetics of H.aridicola demonstrate that the declines in populations are not the result of the internal genetics of these populations but due to external human activities over the past decades.

Asterodiscus and Stigmatodiscus,two new apothecial dothideomycete genera and the new order Stigmatodiscales

During a survey on corticolous Dothideomycetes,several collections with ascospores matching the genera Asteromassaria and Stigmatomassaria(Pleomassariaceae,Pleosporales)were revealed from dead corticated twigs of Acer,Carpinus and Tamarix.Closer morphological examination showed that their ascomata were apothecial,with a hamathecium consisting of septate,branched paraphyses,which are apically swollen at maturity.Several collections were cultured and sequenced,and a Blast search of their nuc 28S rDNA sequences revealed dothideomycetous affiliation,but without a close match to a specific family or order.Phylogenetic analyses of a multigene matrix containing a representative selection of Dothideomycetes from four genes(nuc 18S rDNA,nuc 28S rDNA,rpb2 and tef1)revealed placement within Dothideomycetes but without a supported familial or ordinal affiliation.Based on the phylogenetic analyses and morphological investigations,the new genera Asterodiscus and Stigmatodiscus,with the two new species A.tamaricis and S.enigmaticus,are described and illustrated,and placed in the new family Stigmatodiscaceae and new order Stigmatodiscales.

Valsaria and the Valsariales

More than 100 recent collections of Valsaria sensu lato mostly from Europe were used to elucidate the species composition within the genus.Multigene phylogeny based on SSU,LSU,ITS,rpb2 and tef1 sequences revealed a monophyletic group of ten species within the Dothideomycetes,belonging to three morphologically similar genera.This group could not be accommodated in any known family and are thus classified in the new family Valsariaceae and the new order Valsariales.The genus Valsaria sensu stricto comprises V.insitiva,V.robiniae,V.rudis,V.spartii,V.lopadostomoides sp.nov.and V.neotropica sp.nov.,which are phylogenetically well-defined,but morphologically nearly indistinguishable species.The new monotypic genus Bambusaria is introduced to accommodate Valsaria bambusae.Munkovalsaria rubra and Valsaria fulvopruinata are combined in Myrmaecium,a genus traditionally treated as a synonym of Valsaria,which comprises three species,with M.rubricosum as its generic type.This work is presented as a basis for additional species to be detected in future.

Variation in floral characters,particularly floral scent,in sapromyophilous Stemona species

Flowers or inflorescences often deploy various signals, including visual, olfactory, and gustatory cues,that can be detected by their pollinators. In many plants,these cues and their functions are poorly understood.Deciphering the interactions between floral cues and pollinators is crucial for analyzing the reproductive success of flowering plants. In this study, we examined the composition of the fetid floral scents produced by several Stemona species, including nine S. tuberosa populations from across China, using dynamic headspace adsorption, gas chromatography, and mass spectrometry techniques. We compared variations in floral phenotype,including floral longevity, nectar rewards, pollinator behavior, and flower length and color among the Stemona species. Of the 54 scent compounds identified,the major compounds include fetid dimethyl disulfide,dimethyl trisulfide, 1-pyrroline, butyric acid, p-cresol,isoamyl alcohol, and indole. We detected striking differentiation in floral scent at both the species and population level, and even within a population of plants with different colored flowers. Floral characteristics related to sapromyophily and deceptive pollination,including flower color mimicking livor mortis and a lack of nectar, were found in five Stemona species, indicating that Stemona is a typical sapromyophilous taxon. Species of this monocot genus might employ evolutionary tactics to exploit saprophilous flies for pollination.