The role of chromosomal rearrangements, polyploidy, and genome size variation in the diversity and ecological distribution of Asparagus L. species: a landscape cytogenetics meta-analysis approach

The Asparagus genus includes a group of plants with economic and medicinal importance. Although numerous cytogenetic and genetic studies have been conducted on Asparagus species, there are no reports on landscape genetics, landscape cytogenetics, or Asparagus cultivation in response to climate change. Therefore, we designed this study to answer the above-mentioned objectives. We performed a meta-analysis involving landscape genetic studies based on available cytogenetic data and reported DNA C-values for several Asparagus species from different countries. Additionally, species distribution modeling (SDM) was performed on some selected Asparagus species. This combined study not only identifies the genetic fragmentation and genetic clines within plant species but also predicts their growth and distribution across different regions and in response to climate change. We used discriminant analysis of principal components (DAPC) to group Asparagus taxa based on karyotype and chromosome pairing data. We also performed random forest (RF) analysis to determine the contribution of cytogenetic traits to Asparagus speciation based on the Gini index. An association study was performed using redundancy analysis (RDA) of cytogenetic data with geographic variables (longitude and latitude). We used spatial principal component analysis (sPCA) to analyze the contribution of spatial variables to the cytogenetic structure of the studied Asparagus species. We used Bioclim and Maxent species distribution models (SDMs) to predict and identify areas suitable for selected Asparagus species in response to climate change by 2050. Results indicated that ploidy and chromosome size, the occurrence of heterozygote translocation, frequency and distribution of chiasmata, and genome size play role in Asparagus species diversification and adaptation. These cytogenetic characters are significantly associated with spatial variables and Asparagus species formed cytogenetic clines in response to local environmental conditions. SDM analyses showed that a combination of temperature and precipitation factors affect Asparagus species distribution and that in the coming future, some of these species may have a reduced cultivation area due to climate change which must be tackled by planning a proper conservation program worldwide.