Geographic patterns of genomic diversity in the C4 grass Panicum hallii

Can new genomics approaches be used to assess and understand intraspecific diversity across large geographic distributions?

Geographic patterns of diversity within plant species are shaped by historical and contemporary factors that drive evolutionary processes. A plant species’ life history, including its breeding system and dispersal mechanisms, has a profound influence on its genetic diversity and distribution. Current plant species distributions are the result of geological events that have had influence on soil patterns and changes in climate. Genomic approaches can now be used to understand the influence of such factors on the current distribution of genetic variation.

In their new study published in AoBP, Palacio-Mejía et al. studied diversity of the C4 grass Panicum hallii across its native range in North America. The species, commonly known as Hall’s panicgrass, has a distribution that spans from south-eastern Mexico through the south-central and south-western regions of the USA. In its natural range, P. hallii is found across several environmental gradients, including mesic to xeric (east to west), semi-tropical to temperate zones (south to north) and altitudinal (from sea level along the coastal shore of the Gulf of Mexico to over 2200 metres above sea level in the Guadalupe Mountains, Texas).

This picture describes the perfectly the habitat preferences of Panicum hallii var. halli in West Texas (Davis Mountains, Fort Davis, Texas), growing in a rocky soil, well drained slopy areas and as a solitary grass. Image credit: Palacio-Mejía et al.

In their study, Palacio-Mejía et al. sampled plants extensively across Mexico and the USA to generate DNA sequence data for 423 individuals from 118 locations. They observed strong genetic and morphological divergence across seven genetic clusters that follow major ecoregions. South Texas was identified as a hotspot of genetic diversity with the co-occurrence of all seven genetic clusters and admixture between two described varieties. South Texas is likely a recolonization and convergence point of formerly diverged populations.

Together, the data and analyses in this study provide a foundation for understanding the natural history and evolution of P. hallii and highlight some of the important factors leading the observed structure and genetic diversity in the group. The authors suggest that a practical application of these results could be the creation of a core collection of P. hallii samples to streamline screening for particular traits of interest.

Researcher highlight

Juan Diego Palacio-Mejía is a Colombian agronomist who grew up in the coffee region of the country. Juan got a MSc degree in plant genetics resources from the National University of Colombia and conducted a PhD in plan biology at The University of Texas at Austin. Currently he is the Director of the main Agricultural Field Research Station in Colombia, called Tibaitatá belonging to the Colombian National Agricultural Research Corporation AGROSAVIA.

In a broad sense, Juan’s research interest involves the plant domestication process which made the huge agrobiodiversity of useful plants and relatives possible. To do so, he uses genomic tools to understand the micro evolution and genomic diversity of this plant genetic resources. One of his professional goals in the future is to take advantage of the agrobiodiversity to improve native tropical crops.

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