4.1 Genetic diversity in C. hainanense
The genetic diversity of plants is usually influenced by their range, longevity, reproductive systems, seed dispersal mechanisms, and evolutionary history (Zhang et al., 2021; Nybom et al., 2004). SNP variants are the most significant and extensive type of sequence variation in plant genomes and can be easily identified by sequence alignment (Fang et al., 2014). Our study yielded 477588 high-quality SNPs through screening and filtering. C. hainanense has a wide ecological population in the natural wild state, but the seeds require high germination conditions in the natural environment, limiting the population. The natural wild C. hainanense is distributed as individuals in fragments in the natural tropical forest. So far, no clusters of communities have been found, so the population density of wild C. hainanense is very low, resulting in the population’s weak stress resistance and reproductive ability. Population development is long, and natural recovery is slow.
The genetic diversity of C. hainanense was low. The genetic diversity of C. hainanense was low. The finding that the genetic diversity of C. hainanense is low has significant implications for the conservation and management of this species. C. hainanense is a plant species native to Hainan Island in China. The low genetic diversity, as indicated by the heterozygosity values ranging from 10.79% to 14.55% with an average of 13.15%, suggests that this species may be at risk for several reasons. Low genetic diversity can reduce a species’ ability to adapt to environmental changes, such as shifts in climate or the emergence of new diseases or pests. A more genetically diverse population has a greater chance of possessing the necessary genetic traits to survive and adapt to new challenges. With low genetic diversity, there is an increased likelihood of inbreeding, which can lead to inbreeding depression. This is a reduction in fitness and overall health caused by the increased expression of harmful recessive genes that become more prevalent in a closely related population. Low genetic diversity can make a species more vulnerable to extinction due to its reduced adaptability and potential for inbreeding depression. When a species faces a new threat, it may not have the genetic variation necessary to evolve and survive. Genetic diversity is essential for maintaining the long-term stability and resilience of ecosystems. A species with low genetic diversity might have a reduced ability to fulfill its ecological role, which can negatively impact the overall health and functioning of the ecosystem.
WPESP in nature can lead to an increase in inbreeding due to genetic drift or bottleneck effects, which can lead to a decrease in population genetic diversity, as well as a decrease in population fitness, leaving populations unable to adapt to changing environments and facing extinction (Theodorou, et al., 2015; Nayak, et al., 2010). Xu (2022) reviewed the research on the genetic variation of 120 extremely small populations of wild plants and found that only 10 of the 44 species studied had low genetic diversity at the species level. They areAbies ziyuanensis, thaya argyrophylla, Firmiana danxiaensis, Glyptostrobus pensili, Nyssa yunnanensis, Oreocharis mileensis, Pinus squamata, Sinojackia huangmeiensis、Taxus contorta, Vatica guangxiensis (Xu et al., 2022). At present, the distribution area of C. hainanense is very narrow, and the population collapse, dividing narrowly distributed may be less heritable than widely dividing plant species due to inbreeding and genetic drift(Setoguchi, et al., 2011; Zhang, et al., 2021). Low levels of genetic diversity may impair the population’s ability to adapt to new soil and photoperiodic environments during migration, thereby inhibiting the population’s adaptive potential (Yang et al., 2018). In addition, our field surveys showed that wild resources of C. hainanensewere affected by human activities, such as logging, which led to the fragmentation of its habitat. Habitat fragmentation not only reduces the number of plant populations but also increases the spatial isolation between populations, directly or indirectly affecting species dispersal, gene exchange between populations, and species interactions, and hinders the maintenance of population genetic diversity (Aguilar et al., 2008). The findings revealed that the distribution of C. hainanensepopulations is fragmented. Many native populations have been lost due to fragmentation. Most of the C. hainanense populations were found in protected areas. It also shows human intervention in nature has extended into protected areas. There is an urgent need to prevent the degradation of the remaining high-quality forest ecosystems by protecting and restoring intact forests where possible, as well as by paying attention to those forest landscapes embedded in human modifications, such as those near logging fronts and those near population centers.