Sapindus mukorossi (S. mukorossi) is an important biological washing material and biomass energy tree species whose peel is rich in saponins, and its kernels have a high oil content. We used the maximum entropy model (MaxEnt) to predict the suitable habitats of S. mukorossi globally, screen the dominant environmental factors affecting its distribution and analyse the changes in its suitable habitats under climate change from prehistory to the future, and the results will provide a scientific basis for germplasm resource collection, protection, introduction and cultivation. Twenty-two environmental variables and global distribution data for S. mukorossi were used to construct the species distribution model, and the receiver operating characteristic (ROC) curve was used to verify the accuracy of the model. The dominant environmental factors were screened through the jackknife method, and then, the geographical information system (ArcGIS) was used to complete the grade of suitable habitat division and area calculation. The results showed that the MaxEnt model had an excellent predictive effect, and the area under the ROC curve (AUC) value was as high as 0.969. The precipitation of the warmest quarter (Bio18), the minimum temperature of the coldest month (Bio6), temperature seasonality (Bio4) and isothermality (Bio3) were the dominant environmental factors that affected the distribution of S. mukorossi. The largest area of the world’s suitable habitats occurred during the last interglacial (LIG) (772.69 × 104 km2), and the area decreased sharply (614.46 × 104 km2) during the last glacial maximum (LGM). The area of suitable habitat showed an increasing trend during the Mid-Holocene (MH) and currently, with areas of 631.06 × 104 km2 and 706.82 × 104 km2, respectively. The area of suitable habitats for S. mukorossi globally was 718.35 × 104 km2 (SSP1-2.6), 636.85 × 104 km2 (SSP2-4.5), 657.64 × 104 km2 (SSP3-7.0) and 675.89 × 104 km2 (SSP5-8.5) under the four scenarios of the future climate. The area increased only in the SSP1 scenario. In summary, globally, the suitable area of S. mukorossi tended to migrate to higher latitudes and decrease in area with future climate change.

Predicting the potential global distribution of Sapindus mukorossi under climate change based on MaxEnt modelling

Distinct ecological habits and habitat responses to future climate change in three east and southeast Asian Sapindus species

We report the first chromosome-scale genome assembly of Sapindus mukorossi, covering ~391 Mb with a scaffold N50 of 24.66 Mb. Population genetic analyses showed that genetic diversity in the southwest of the distribution area is relatively higher than that in the northeast. Genome-wide selective sweep analysis showed that the selection of a large number of genes is involved in defense responses, growth, and development. Our identified candidate genes are associated with major agronomic traits, and this information can be used for further reference in the selection of superior germplasm resources.

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Chromosome-scale assembly and population diversity analyses provide insights into the evolution of Sapindus mukorossi

Sapindus is an important forest tree genus with utilization in biodiesel, biomedicine, and it harbors great potential for biochemical engineering applications. For advanced breeding of Sapindus, it is necessary to evaluate the genetic diversity and construct a rationally designed core germplasm collection. In this study, the genetic diversity and population structure of Sapindus were conducted with 18 expressed sequence tag-simple sequence repeat (EST-SSR) markers in order to establish a core germplasm collection from 161 Sapindus accessions. The population of Sapindus showed high genetic diversity and significant population structure. Interspecific genetic variation was significantly higher than intraspecific variation in the Sapindus mukorossi, Sapindus delavayi, and combined Sapindus rarak plus Sapindus rarak var. velutinus populations. S. mukorossi had abundant genetic variation and showed a specific pattern of geographical variation, whereas S. delavayi, S. rarak, and S. rarak var. velutinus showed less intraspecific variation. A core germplasm collection was created that contained 40% of genetic variation in the initial population, comprising 53 S. mukorossi and nine S. delavayi lineages, as well as single representatives of S. rarak and S. rarak var. velutinus. These results provide a germplasm basis and theoretical rationale for the efficient management, conservation, and utilization of Sapindus, as well as genetic resources for joint genomics research in the future.

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Genetic Diversity Analysis of Sapindus in China and Extraction of a Core Germplasm Collection Using EST-SSR Markers

Geographical differences of leaf traits of the endangered plant Litsea coreana Levl. var. sinensis and its relationship with climate

To explore differences in leaf morphology between Sapindus mukorossi and Sapindus delavayi, and how the environment might drive these differences, 80 germplasm samples from the Sapindus germplasm nursery in Fujian Province were selected. The study revealed a wide variation and diversity in 16 germplasm traits, both within and between species grown under the same conditions. On average, the relative contribution of intraspecific variability to total variability was more important (83%) than the relative contribution of interspecific variability (17%). PERMANOVA analysis showed differences in leaflet thickness, length, perimeter, length to width ratio, and leaf hairs or trichome density. Correlation analyses between leaf morphological traits and environmental variables indicated that leaves tended to be larger, longer, and thicker in wetter, warmer, and low-altitude conditions. Our analysis of the relationship between climate and leaf morphology revealed that S. mukorossi had a greater sensitivity to climate variation, particularly in response to mean temperatures of the coldest and warmest seasons, which led to differences in leaf traits and the distribution of the two species. These findings contribute to the understanding of leaf morphology variations in S. mukorossi and S. delavayi, and provide a basis for the collection of Sapindus germplasm resources, their cultivation and use to help address climate change.

Biogeographic divergence in leaf traits of Sapindus mukorossi and Sapindus delavayi and its relation to climate

Sapindus L. species are widely cultivated for biodiesel, biomedical, and biochemical raw materials in southern China. However, yields fluctuate widely due to the lack of high-yielding, high-quality, stable cultivars. Therefore, the objectives of this study were to evaluate three species and one variety among 149 nationwide Sapindus species and screen for elite accessions which would serve as Sapindus breeding materials. Accessions were evaluated on 19 agro-morphological traits by correlation analysis and principal component analysis. These displayed substantial diversity and a broad range of economic traits. In particular, accessions of Sapindus mukorossi and Sapindus rarak had more variation in economic traits than Sapindus delavayi and Sapindus rarak var. velutinus. Increased saponin accumulation may be achieved at the cost of seed oil production. Thirty elite accessions for oil and saponin production, and for comprehensive utilization were screened and accessions no. 80, 110, and 112 had significant potential to produce high yields. These elite accessions will facilitate the identification of genetic determinants of valuable traits and the effective utilization of trait variability in Sapindus breeding.

Screening of Sapindus germplasm resources in China based on agro-morphological traits


 Background: Sapindus is an important biodiesel, biomedical, and multifunctional economic forest species in Asia, however its germplasms have been persistently damaged or lost. It is imperative to conserve the diversity of Sapindus. This study aimed to reveal the potential habitat distribution patterns of Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in response to current environment and future climate change, and identify hotspots of habitat degradation/expansion to facilitate climate change-adaptive biological conservation. Methods: Using current environmental data and future climate projections (2021–2100), we simulated the present and potential future habitats of Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in east and southeast Asia using a maximum entropy (MaxEnt) model that was developed based on 2041 occurrence records. Results: The model showed that precipitation may play an important role in framing the potential habitats of Sapindus; however, S. delavayi was more sensitive to minimum temperatures (-2 °C to 3 °C) and elevation (1200-2000 m), while S. rarak was more demanding in terms of solar radiation (annual mean Uvb of 4600 to 5000 J/m2/day). Under the current environment, S. mukorossi has the widest suitable habitat distribution (250.24 × 104 km2), followed by that of S. rarak (173.49 × 104 km2), and S. delavayi (78.85 × 104 km2). Under future climate change scenarios, the habitat distribution of S. mukorossi will expand and contract, that of S. delavayi exhibited significant expansion. In contrast, future S. rarak habitat distribution exhibited significant contraction. Conclusions: There were significantly distinct ecological adaptations among Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak in east and southeast Asia. The contraction areas should be subject to germplasm collection and ex situ conservation preferentially. The modelled unchanged areas should be used for potential future Sapindus mukorossi, Sapindus delavayi, and Sapindus rarak conservation and utilization.

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Xin Wang

Papers

Biogeographic divergence in leaf traits of Sapindus mukorossi and Sapindus delavayi and its relation to climate

Screening of Sapindus germplasm resources in China based on agro-morphological traits

Distinct Ecological Adaptations and Habitat Responses to Future Climate Change in Three East and Southeast Asian Sapindus Species