Population structure and genetic diversity of Bromus tectorum within the small grain production region of the Pacific Northwest.

Nevin C. Lawrence,Ian C. Burke,Amber L. Hauvermale,Amit Dhingra

doi:10.1002/ece3.3386

Nevin C. Lawrence, Ian C. Burke + Show 2 more

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https://doi.org/10.1002/ece3.3386

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Abstract

Bromus tectorum L. is an invasive winter annual grass naturalized across the United States. Numerous studies have investigated B. tectorum population structure and genetics in the context of B. tectorum as an ecological invader of natural areas and rangeland. Despite the wealth of information regarding B. tectorum, previous studies have not focused on, or made comparisons to, B. tectorum as it persists in individual agroecosystems. The objectives of this study were to assess the genetic diversity and structure, the occurrence of generalist and specialist genotypes, and the influence of climate on distribution of B. tectorum sourced exclusively from within small grain production regions of the Pacific Northwest. Genetic diversity of B. tectorum sourced from agronomic fields was found to be similar to what has been observed from other land use histories. Six distinct genetic clusters of B. tectorum were identified, with no evidence to indicate that any of the genetic clusters were better adapted to a particular geographical area or climate within the region. Given the apparent random spatial distribution of B. tectorum genetic clusters at the spatial scale of this analysis, unique genotypes may be well mixed within region, similar to what was reported for other inbreeding weedy grass species.

Highlights

Agricultural weeds represent the ecological and evolutionary response of human crop cultivation to native and introduced flora (Neve, Vila-Aoib, & Roux, 2009)
Analysis of population genetics and genetic structure from downy brome collected within an agronomic region indicates that the heterozygous state of downy brome is similar, if not marginally greater, to what has been reported in previous literature
Downy brome exists within the PNW small grain production region as a series of generalist genotype clusters with limited evidence of spatial adaptation, similar to what was reported Novak et al (1991) in a broad survey of downy brome across North America

Summary

Introduction

Agricultural weeds represent the ecological and evolutionary response of human crop cultivation to native and introduced flora (Neve, Vila-Aoib, & Roux, 2009). The yearly disturbance of tillage, planting, and herbicide applications may impact how evolutionary forces such as genetic drift, selection, and breeding systems act against weed species in a different way than previously observed in rangeland or natural areas (Thrall et al, 2011). Neve et al (2009) argues modern weed management requires an approach based in evolutionary biology, of which the first step is understanding “the extent, structure, and significance of genetic variation.”. Downy brome (Bromus tectorum) is a widely distributed weed across North America, and the population genetics of the species has been well characterized.

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