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Ardisia gigantifolia is a critically endangered medicinal plant endemic to China and only 77 wild individuals were found at present. To provide detailed information for selecting its restoration habitats, plantlets of this species were transplanted into four sites with different habitats, including two current sites (GLQ and HK) with extant populations, one historical site (NX) and one site (BG) outside its historical range but near the existing range. The survival, growth and physiological performance of transplanted plantlets and habitat characters were compared among the four sites, and the population structure and physiological traits of wild individuals were compared among the two extant populations. The results revealed that relative irradiance would be the main factor influencing the photosynthesis and growth of transplanted plantlets. Transplanted plantlets at NX presented the best overall performance in survival, growth and physiology, and presented better physiological performance than wild seedlings at the two current sites, revealing that NX was the optimal habitat for reintroduction of A. gigantifolia. Compared to NX, severe shading at GLQ and HK resulted in the decrease of light energy utilization efficiency and growth parameters. Wild seedlings at GLQ exhibited significantly lower light energy utilization efficiency but significantly higher malondialdehyde content than those at HK, which would explain the lower proportion of young individuals and the smaller growth trend in the GLQ population.

Based on the analysis of introduction and survival records, this paper reports the status of introduction, survival, and ex-situ conservation of plant species in the South China National Botanical Garden (SCNBG). The results are as follows: (1) A total of 19 154 species, 99 subspecies and 136 varieties (80 597 accession numbers) of vascular plants belonging to 325 families and 3 952 genera have been introduced since 1956, of which 11 581 species, 52 subspecies and 80 varieties (24 352 accession number) belonging to 290 families and 2 777 genera are surviving currently; the introduction records include 565 species of National Key Protected Wild Plants (421 species survived), covering 94.7% (36/38) of the first-class National Key Protected Wild Plants (29 species survived), 76.4%（269/352）of the second-class National Key Protected Wild Plants (229 species survived), and 54.3%（547/1 008）threatened species (414 species survived) in South China. (2) The most species are introduced from Guangdong Province (7 193 accession numbers, 2 523 species), followed by Hainan Province (3 658 accession numbers, 1 593 species), Guangxi Province (4 744 accession numbers, 1 559 species) and other surrounding provinces (regions); the SCNBG has obtained some precious plant resources from the same latitude regions by introducing and exchanging species with 61 countries around the world. (3) 17 specialized gardens for ex-situ conservation based on plant taxa (e. g. Magnolia Garden) show a high level in terms of introduction quantity and survival rate. (4) The correlation between the number of surviving species and the frequency of introduction is extremely significant (r = 0.85***). (5) The survival rate of introduced species distributed naturally in South China is higher than that in other provinces. In the future, the SCNBG needs to strengthen the ex-situ conservation of plants through following points: (1) On the basis of investigation, cataloguing, evaluation and research, strengthening the introduction and collection of rare and endangered plants, native plants and economically important plants in tropical and subtropical regions, further improving the quantity and quality of ex-situ conservation; (2) Establishing an ex-situ conservation network system for plants in South China to effectively protect plant diversity in this region; (3) Improving the infrastructure construction and information management level of ex-situ conservation for higher efficiency; (4) Enhancing international scientific research cooperation and species exchange.

Abstract Background The factors that maintain phenotypic and genetic variation within a population have received long-term attention in evolutionary biology. Here the genetic basis and evolution of the geographically widespread variation in twig trichome color (from red to white) in a shrub Melastoma normale was investigated using Pool-seq and evolutionary analyses. Results The results show that the twig trichome coloration is under selection in different light environments and that a 6-kb region containing an R2R3 MYB transcription factor gene is the major region of divergence between the extreme red and white morphs. This gene has two highly divergent groups of alleles, one of which likely originated from introgression from another species in this genus and has risen to high frequency (> 0.6) within each of the three populations under investigation. In contrast, polymorphisms in other regions of the genome show no sign of differentiation between the two morphs, suggesting that genomic patterns of diversity have been shaped by homogenizing gene flow. Population genetics analysis reveals signals of balancing selection acting on this gene, and it is suggested that spatially varying selection is the most likely mechanism of balancing selection in this case. Conclusions This study demonstrate that polymorphisms on a single transcription factor gene largely confer the twig trichome color variation in M. normale, while also explaining how adaptive divergence can occur and be maintained in the face of gene flow.

Abstract Hybridization is very common in flowering plants and it plays a significant role in plant evolution and adaptation. Melastoma L. (Melastomataceae) comprises about 80–90 species in tropical Asia and Oceania, among which 41 species occur in Borneo. Natural hybridization is frequently reported in Melastoma in China, but so far there have been no confirmed cases of hybridization in Southeast Asia (including Borneo), where most species occur. Here, we identified a case of natural hybridization between Melastoma malabathricum L. and Melastoma beccarianum Cogn. in Sarawak, Malaysia, by using sequence data of three nuclear genes and one chloroplast intergenic spacer. Melastoma malabathricum is the most widespread species of this genus, occurring in almost the whole range of this genus, while M. beccarianum is a local species endemic to northern Borneo. Our results showed that natural hybridization and introgression occur between M. malabathricum and M. beccarianum, and the introgression was asymmetrical, mainly from M. malabathricum to M. beccarianum. As adaptive traits can be transferred by introgression, our study suggests that natural hybridization should be a significant mechanism for the evolution and adaptation of Melastoma in Southeast Asia. However, introgression from the common species M. malabathricum to the relatively rare species M. beccarianum may cause the decline of M. beccarianum, incurring conservation concern. With a large number of species of Melastoma and almost year‐around flowering in Southeast Asia, more cases of natural hybridization are expected to be found and identified in near future.

Inferring the origins of hybrid taxa based on morphology alone is difficult because morphologically similar hybrids can arise from hybridization between different populations of the same parental species or be produced by hybridization of different parental species. In this study, we investigated the origins of two semi-creeping taxa in Melastoma, which are morphologically similar to a natural hybrid, M. intermedium, by sequencing a chloroplast intergenic spacer, nuclear ribosomal internal transcribed spacer and two low-copy nuclear genes (tpi and cam) in these taxa and their putative parental species. Our sequence analysis provides compelling evidence for the hybrid status of the two semi-creeping taxa: one originating from hybridization between M. dodecandrum and M. malabathricum, and the other between M. dodecandrum and M. normale. The origins of these hybrids are therefore clearly different from M. intermedium, and morphological similarity for the three hybrids is most likely due to their origins from hybridization between the same creeping species M. dodecandrum and a different erect species in each of the three cases. We also observed low rate of introgression from M. normale to M. dodecandrum, and genetic exchange between them may transfer adaptive traits to M. dodecandrum. Rare occurrence of these two hybrids may be due to small range overlaps between parental species in one case, and different flowering periods between parental species in the other.

Inferring the origins of hybrid taxa based on morphology alone is difficult because morphologically similar hybrids can arise from hybridization between different populations of the same parental species or be produced by hybridization of different parental species. In this study, we investigated the origins of two semi-creeping taxa in Melastoma, which are morphologically similar to a natural hybrid, M. intermedium, by sequencing a chloroplast intergenic spacer, nuclear ribosomal internal transcribed spacer and two low-copy nuclear genes (tpi and cam) in these taxa and their putative parental species. Our sequence analysis provides compelling evidence for the hybrid status of the two semi-creeping taxa: one originating from hybridization between M. dodecandrum and M. malabathricum, and the other between M. dodecandrum and M. normale. The origins of these hybrids are therefore clearly different from M. intermedium, and morphological similarity for the three hybrids is most likely due to their origins from hybridization between the same creeping species M. dodecandrum and a different erect species in each of the three cases. We also observed low rate of introgression from M. normale to M. dodecandrum, and genetic exchange between them may transfer adaptive traits to M. dodecandrum. Rare occurrence of these two hybrids may be due to small range overlaps between parental species in one case, and different flowering periods between parental species in the other. [ABSTRACT FROM AUTHOR]

Twelve polymorphic microsatellite loci were isolated and characterized from an AC-enriched genomic library of Nothotsuga longibracteata. The average allele number of these microsatellites was 8.3 per locus, ranging from two to 13. The ranges of observed and expected heterozygosities were 0.03–0.97 and 0.09–0.88, respectively. These polymorphic markers provide useful tools for the study of evolutionary history and conservation genetics of N. longibracteata. [ABSTRACT FROM AUTHOR]