Abstract
Understanding the population genetic pattern and process of gene flow requires a detailed knowledge of how landscape characteristics structure populations. Although Cynodon dactylon (L.) Pers. (common bermudagrass) is widely distributed in the world, information on its genetic pattern and population structure along latitudinal gradients is limited. We tried to estimate the genetic diversity and genetic structure of C. dactylon along a latitudinal gradient across China. Genetic diversity among different ploidy levels was also compared in the study. The material used consisted of 296 C. dactylon individuals sampled from 16 geographic sites from 22°35′ N to 36°18′ N. Genetic diversity was estimated using 153 expressed sequence tag-derived simple sequence repeat (EST-SSR) loci. Higher within-population genetic diversity appeared at low-latitude, as well as having positive correlation with temperature and precipitation. The genetic diversity increased with the ploidy level of C. dactylon, suggesting polyploidy creates higher genetic diversity. No isolation by distance and notable admixture structure existed among populations along latitudes. Both seed dispersal (or vegetative organs) and extrinsic pollen played important roles for gene flow in shaping the spatial admixture population structure of C. dactylon along latitudes. In addition, populations were separated into three clusters according to ploidy levels. C. dactylon has many such biological characters of perennial growth, wind-pollination, polyploidy, low genetic differentiation among populations, sexual and asexual reproduction leading to higher genetic diversity, which gives it strong adaptability with its genetic patterns being very complex across all the sampled latitudes. The findings of this study are related to landscape population evolution, polyploidy speciation, preservation, and use of bermudagrass breeding.
Highlights
IntroductionUnderstanding genetic variation distribution over latitudinal gradients has been a central interest of population genetics in evolutionary biology, molecular ecology, and other related disciplines
Understanding genetic variation distribution over latitudinal gradients has been a central interest of population genetics in evolutionary biology, molecular ecology, and other related disciplines.Genetic variation of individuals and genetic differentiation among populations have been caused in history by adaptation to the environment and population processes
After four groups were separated by latitude, we observed that the highest genetic diversity appeared within the group at low latitude and in contrast three other groups had lower values (Table 3)
Summary
Understanding genetic variation distribution over latitudinal gradients has been a central interest of population genetics in evolutionary biology, molecular ecology, and other related disciplines. Genetic variation of individuals and genetic differentiation among populations have been caused in history by adaptation to the environment and population processes. The processes include genetic drift, migration, dispersal, and gene flow [1], which are traditionally assayed using neutral genetic tools such as microsatellite markers [2,3]. Diversity 2019, 11, 135 provided using population genetic sampling and measures for detecting genetic relationships within continuously distributed populations in a landscape gradient [4,5]. Different levels of genetic diversity may occur in response to local different population size and habitat [6]
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