Reproductive biology of Magnolia sinica (Magnoliaecea), a threatened species with extremely small populations in Yunnan, China

Unravelling some factors affecting sexual reproduction in rock-specialist shrub: Insight from an endemic Daphne arbuscula (Thymelaeaceae)

The role of endemic species in global biodiversity is pivotal, and understanding their biology and ecology is imperative for their fitness and long-term survival, particularly in the face of ongoing climatic oscillations. Our primary goal was to investigate the sexual reproduction level of the endangered Western Carpathian endemic Daphne arbuscula (Thymelaeaceae), which inhabits extreme rocky habitats, and to comprehend the influence of specific factors on its reproductive success. We conducted the research across four populations, varying in size and environmental conditions. Over two years, we monitored flower and fruit production, analyzed genetic variability within and among populations, and studied pollination mechanisms. Daphne arbuscula proved to be strictly self-incompatible, with significant variations in flower and fruit production among populations and seasons. The average fruit production percentage consistently remained below 50% across populations, indicating challenges in sexual reproduction. Cold and harsh weather during the reproductive phase had a substantial negative impact on sexual reproduction efficacy, leading to decreased fruit production. Nevertheless, several individuals in sheltered microhabitats displayed significantly higher fruit production, ranging from 60% to 83%, emphasizing the critical role of microhabitat heterogeneity in sustaining sexual reproduction in this species. We found no pronounced differences in genetic diversity within or among populations, suggesting that genetic factors may not critically influence the reproductive success of this endemic species. The implications of our findings might be of paramount importance for the long-term survival of D. arbuscula and offer valuable insights for the development of effective conservation strategies for this species.

The chromosome-scale genome of Magnolia sinica (Magnoliaceae) provides insights into the conservation of plant species with extremely small populations (PSESP)

Magnolia sinica (Magnoliaceae) is a highly threatened tree endemic to southeast Yunnan, China. In this study, we generated for the first time a high-quality chromosome-scale genome sequence from M. sinica, by combining Illumina and ONT data with Hi-C scaffolding methods. The final assembled genome size of M. sinica was 1.84 Gb, with a contig N50 of ca. 45 Mb and scaffold N50 of 92 Mb. Identified repeats constituted approximately 57% of the genome, and 43,473 protein-coding genes were predicted. Phylogenetic analysis shows that the magnolias form a sister clade with the eudicots and the order Ceratophyllales, while the monocots are sister to the other core angiosperms. In our study, a total of 21 individuals from the 5 remnant populations of M. sinica, as well as 22 specimens belonging to 8 related Magnoliaceae species, were resequenced. The results showed that M. sinica had higher genetic diversity (θw = 0.01126 and θπ = 0.01158) than other related species in the Magnoliaceae. However, population structure analysis suggested that the genetic differentiation among the 5 M. sinica populations was very low. Analyses of the demographic history of the species using different models consistently revealed that 2 bottleneck events occurred. The contemporary effective population size of M. sinica was estimated to be 10.9. The different patterns of genetic loads (inbreeding and numbers of deleterious mutations) suggested constructive strategies for the conservation of these 5 different populations of M. sinica. Overall, this high-quality genome will be a valuable genomic resource for conservation of M. sinica.

Conservation of rare and endangered plant species in China

Rare and endangered plant species (REPs) are facing high danger of extinction, yet a comprehensive and up-to-date review on their conservation in China is still lacking. This paper systematically collected studies and achievements on REPs conservation, including species surveys and monitoring, cause of endangerment, in situ conservation, ex situ conservation, reintroduction, propagation, conservation legislation, public participation, progress in conservation of wild plant with extremely small populations, and progress in China's implementation of the Convention on Biological Diversity. Although enormous advances have been made in conservation policies and legislations, protection systems, and research, as well as public education and international collaborations, the conservation efficiency is still restricted largely by the conflict between economic growth and biodiversity conservation in China. In order to meet its commitments to the new Post-2020 Global Biodiversity Framework, more work on basic investigation and long-term observation, as well as advanced technologies and application-oriented research on REPs should be carried out.

Comparative analysis of the complete chloroplast genomes of six threatened subgenus Gynopodium (Magnolia) species

BACKGROUND

The subgenus Gynopodium belonging to genus Magnolia have high ornamental, economic, and ecological value. Subgenus Gynopodium contains eight species, but six of these species are threatened. No studies to date have characterized the characteristics of the chloroplast genomes (CPGs) within subgenus Gynopodium species. In this study, we compared the structure of CPGs, identified the mutational hotspots and resolved the phylogenetic relationship of subgenus Gynopodium.

RESULTS

The CPGs of six subgenus Gynopodium species ranged in size from 160,027 bp to 160,114 bp. A total of 131 genes were identified, including 86 protein-coding genes, eight ribosomal RNA genes, and 37 transfer RNA genes. We detected neither major expansions or contractions in the inverted repeat region, nor rearrangements or insertions in the CPGs of six subgenus Gynopodium species. A total of 300 large repeat sequences (forward, reverse, and palindrome repeats), 847 simple sequence repeats, and five highly variable regions were identified. One gene (ycf1) and four intergenic regions (psbA-trnH-GUG, petA-psbJ, rpl32-trnL-UAG, and ccsA-ndhD) were identified as mutational hotspots by their high nucleotide diversity (Pi) values (≥ 0.004), which were useful for species discrimination. Maximum likelihood and Bayesian inference trees were concordant and indicated that Magnoliaceae consisted of two genera Liriodendron and Magnolia. Six species of subgenus Gynopodium clustered as a monophyletic clade, forming a sister clade with subgenus Yulania (BS = 100%, PP = 1.00). Due to the non-monophyly of subgenus Magnolia, subgenus Gynopodium should be treated as a section of Magnolia. Within section Gynopodium, M. sinica diverged first (posterior probability = 1, bootstrap = 100), followed by M. nitida, M. kachirachirai and M. lotungensis. M. omeiensis was sister to M. yunnanensis (posterior probability = 0.97, bootstrap = 50).

CONCLUSION

The CPGs and characteristics information provided by our study could be useful in species identification, conservation genetics and resolving phylogenetic relationships of Magnoliaceae species.

Comparison of the Bulk and Rhizosphere Soil Prokaryotic Communities Between Wild and Reintroduced Manglietiastrum sinicum Plants, a Threatened Species with Extremely Small Populations

Huagaimu (Manglietiastrum sinicum) trees are critically endangered species and classified as a plant species with extremely small populations in China. Rhizospheres and bulk soils prokaryotic communities play an important role to protect and promote plants health and growth. However, the compositions and structures of prokaryotic communities in wild and reintroduced M. sinicum rhizospheres and bulk soils are still poorly understood. In the present study, prokaryotic communities in wild and reintroduced M. sinicum rhizospheres and bulk soils were compared using high-throughput sequencing. Thirty-two phyla, 76 classes, 193 orders, 296 families, and 470 genera of prokaryotes were obtained. Proteobacteria and Acidobacteria were the two most abundant phyla in all soil samples. The compositions and structures of prokaryotic communities were overall similar, and the abundance of some taxa varied significantly among soil samples. Soil prokaryotic communities were significantly affected by soil pH, total nitrogen, total phosphorus, and total potassium. Eleven of predicted functions were significantly different among the four soil groups. This study provides for the first insights into the compositions, structures, and potential functions of prokaryotic communities associated with wild and reintroduced M. sinicum rhizospheres and bulk soils, and providing a foundation for future research to help protect this endangered species.

Comparative Analysis of Fungal Diversity in Rhizospheric Soil from Wild and Reintroduced Magnolia sinica Estimated via High-Throughput Sequencing

Magnolia sinica is a critically endangered species and considered a “plant species with extremely small populations” (PSESP). It is an endemic species in southeastern Yunnan Province, China, with reproductive barriers. Rhizosphere fungi play a crucial role in plant growth and health. However, the composition, diversity, and function of fungal communities in wild and reintroduced M. sinica rhizospheres remain unknown. In this study, Illumina sequencing of the internal transcribed spacer 2 (ITS2) region was used to analyze rhizospheric soil samples from wild and reintroduced M. sinica. Thirteen phyla, 45 classes, 105 orders, 232 families, and 433 genera of fungi were detected. Basidiomycota and Ascomycota were dominant across all samples. The fungal community composition was similar between the wild and reintroduced rhizospheres, but the fungal taxa relative abundances differed. The fungal community richness was higher in the reintroduced rhizosphere than in the wild rhizosphere, but the diversity showed the opposite pattern. Soil nutrients and leaf litter significantly affected the fungal community composition and functional diversity. Here, the composition, structure, diversity, and ecological functions of the fungal communities in the rhizospheres of wild and reintroduced M. sinica were elucidated for the first time, laying a foundation for future research and endangered species protection.