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Members of the aquatic plant genus Aponogeton are widely used commercially in aquariums because of their variable leaf shape and unique inflorescences. However, due to extensive similarity between species in this genus, morphological characters are generally inadequate for taxonomic classification. Currently, molecular makers available for taxonomic and phylogenetic studies of Aponogeton are limited. One approach to clarifying relationships between species in these complex groups is to use divergence hotspot regions within the genome. Here, we sequenced and analyzed the plastomes of five Aponogeton species collected from China, Zambia, and Kenya, and subsequently screened these plastomes for divergent DNA hotspots. The five plastomes are circular structures with sizes ranging from 154,167 bp to 154,860 bp. The Large and the Small Single Copies are separated by two Inverted Repeats. One hundred and thirteen unique genes were identified including 79 protein-coding, 30 tRNA, and four rRNA genes. We found that the most abundant repeats in all but one species were mononucleotide repeats (A/T) and that there were 23 potential RNA ending sites. Interestingly, a ~3 kb inversion, which includes the accD gene, was detected within the Asian species of Aponogeton . The inversion may be related to more frequent exchanges between this region and the nuclear genome. Furthermore, we detected mutational hotspot sites among the five Aponogeton species. Three of these hotspots are intergenic spacer regions ( accD-psaI , rbcL-accD and trnH-GUG-psbA ) that might be suitable for use as barcodes to resolve intra-generic relationships. We also identified four highly variable protein-coding genes ( ccsA , rpl22 , rps16 and ycf1 ) may be used as barcodes to resolve the higher-level phylogenies. Our study will provide valuable molecular resources for the taxonomic and phylogenomic study of the complex genus Aponogeton .

Background: Nelumbo nucifera Gaertn., a perennial aquatic macrophyte species, has been cultivated in several Asian countries for its economic importance, and medicinal uses. Two distinct ecotypes of the species are recognized based on the geographical location where the genotypes are adapted, i.e., tropical lotus and temperate lotus. The genetic diversity levels and differentiation of the tropical lotus from poorly studied geographic regions still remain unclear. Here, the population genetic diversity and structure of 15 tropical lotus populations sampled from the previous understudied natural distribution ranges, including India, Thailand, and Australia, were assessed using nine polymorphic SSR markers. Results: The SSR markers used to genotype the 216 individuals yielded 65 alleles. The highest and lowest genetic diversity estimates were found in Thailand and Indian populations, respectively. STRU CTU RE analysis revealed three distinct genetic clusters, with relatively low admixtures, supported by PCoA cluster analysis. Low levels of gene flow (mean N m = 0.346) among the three genetic clusters signified the Mantel test for isolation by distance, revealing the existence of a positive correlation between the genetic and geographic distances (r = 0.448, P = 0.004). Besides, AMOVA analysis revealed a higher variation among populations (59.98%) of the three groups. Overall, the populations used in this study exposed a high level of genetic differentiation (F ST = 0.596). Conclusions: The nine polymorphic microsatellite markers used in our study sufficiently differentiated the fifteen tropical N. nucifera populations based on geography. These populations presented different genetic variability, thereby confirming that populations found in each country are unique. The low genetic diversity (H E = 0.245) could be explained by limited gene flow and clonal propagation. Conserving the available diversity using various conservation approaches is essential to enable the continued utilization of this economically important crop species. We, therefore, propose that complementary conservation approaches ought to be introduced to conserve tropical lotus, depending on the genetic variations and threat levels in populations.

Understanding how species have adapted and responded to past climate provides insights into the present geographical distribution and may improve predictions of how biotic communities will respond to future climate change. Therefore, estimating the distribution and potentially suitable habitats is essential for conserving sensitive species such as Garuga forrestii W.W.Sm., a tree species endemic to China. The potential climatic zones of G. forrestii were modelled in MaxEnt software using 24 geographic points and nine environmental variables for the current and future (2050 and 2070) conditions under two climate representative concentration pathways (RCP4.5 and RCP8.5) scenarios. The resulting ecological niche models (ENMs) demonstrated adequate internal assessment metrics, with all AUC and TSS values being >0.79 and a pROC of >1.534. Our results also showed that the distribution of G. forrestii was primarily influenced by temperature seasonality (% contribution = 12%), elevation (% contribution = 27.5%), and precipitation of the wettest month (% contribution = 35.6%). Our findings also indicated that G. forrestii might occupy an area of 309,516.2 km2 in southwestern China. We note that the species has a potential distribution in three provinces, including Yunnan, Sichuan, and Guangxi. A significant decline in species range is observed under the future worst case of high-emissions scenario (RCP8.5), with about 19.5% and 20% in 2050 and 2070, respectively. Similarly, higher elevations shift northward to southern parts of Sichuan province in 2050 and 2070. Thus, this study helps highlight the vulnerability of the species, response to future climate and provides an insight to assess habitat suitability for conservation management.