Background: Understanding genetic diversity is a core issue in conservation genetics. However, previous genetic diversity evaluations of narrowly distributed species have rarely used closely related widespread species as a reference. Furthermore, identifying natural hybridization signals between narrowly and widely distributed sympatric species is of great importance for the development of species conservation programs.Methods: In this study, population genotyping by sequencing (GBS) was performed for a narrowly distributed species,Geodorum eulophioides(endemic and endangered in Southwest China), and a widespread species,G. densiflorum. A total of 18,490 high-quality single nucleotide polymorphisms (SNPs) were identified at the whole-genome level.Results: The results showed that the nucleotide diversity and heterozygosity ofG. eulophioideswere significantly higher than those ofG. densiflorum, confirming that narrowly distributed species can still preserve high genetic diversity. Consistent with taxonomic boundaries, all sampled individuals from the two species were divided into two genetic clusters and showed high genetic differentiation between species. However, in a sympatric population, a fewG. eulophioidesindividuals were detected with genetic components fromG. densiflorum, suggesting potential interspecific natural hybridization. This hypothesis was supported by Treemix analysis and hand-hybridization trials. Invasion of the habitat ofG. eulophioidesinvasion byG. densiflorumunder anthropogenic disturbance may be the main factor causing interspecific hybridization.Conclusions: Therefore, reducing or avoiding habitat disturbance is a key measure to protect theG. eulophioidespopulations. This study provides valuable information for future conservation programs for narrowly distributed species.

Camellia perpetua is a rare and unique species in the karst regions in Guangxi of south China, it is a rare camellia group that blooms almost all year round and its peak flowering period is in summer. To understand the rhythm of nectar secretion and the pattern of pollination of this species in different seasons, and exploring the influence of composition and amount of nectar on the behavior of its pollinator species. The average amount of nectar a single flower of C. perpetua was 129.14 ± 4.48 μL in the summer and sugar concentration was 25.77 ± 5.94%, which was 453.66 ± 4.67 μL and 25.77 ± 5.94% in winter, respectively. The rhythm of nectar secretion showed that less nectar was secreted during the day, much more nectar was secreted during the evening and night. The nectar was sucrose dominant in summer and winter, and composed mainly of sucrose, glucose and fructose. There were 18 types of amino acids in C. perpetua in summer, with a total of 1,317 ± 23.68 μg·mL-1, and 9 types of amino acids in winter, with a total of 530 ± 15.96 μg·mL-1. The bee pollinators visited the flowers more frequently in the summer than in the winter, while the birds visited the flowers more frequently in the winter. The change of pollinators’ adaptive behavior may be related to nectar production, sugar concentration and amino acid type and content in different seasons.

Keteleeria davidiana var. calcarea is an endangered plant endemic to China. It is mainly distributed in the karst areas of the Guangxi and Guizhou Provinces. It is characterized by small populations and intermittent distribution. This study aimed to explore the genetic diversity and mating system of wild populations of Keteleeria davidiana var. calcarea in fragmented habitats. To achieve this, we genotyped 46 maternal trees and 214 progenies from four fragmented populations of Keteleeria davidiana var. calcarea using nine pairs of microsatellite primers. The genetic diversity of Keteleeria davidiana var. calcarea (Ho = 0.68, He = 0.63) was lower than that of the species overall but higher than that of other Keteleeria plants. The incidence of unbiased expected heterozygosity (uHe) and allelic richness (Ar) was higher in the maternal generation than in the progeny. This suggests that the genetic diversity of the progeny was lower than that of the maternal generation. Keteleeria davidiana var. calcarea is divided into four populations, but there is significant genetic exchange between the populations according to STRUCTURE and gene flow analyses. The multilocus mating system analysis (MLTR) results indicate that the multilocus outcrossing rate (t_m) was 0.902, the single-locus outcrossing rate (t_s) was 0.606, the bimaternal inbreeding coefficient (t_m-t_s) was 0.295, and the coefficient of inbreeding depression(δ) was 0.904. These results suggest a certain degree of selfing and inbreeding in Keteleeria davidiana var. calcarea. To prevent problems associated with inbreeding and conserve the genetic diversity of Keteleeria davidiana var. calcarea, we recommend establishing seed gardens, using artificial pollination, and employing asexual propagation techniques for conservation intervention.