Abstract Detail

Population Genetics/Genomics

Fajardo, Kristine [1], Fajardo, Kristine [1], Duque, Josue [1], Waselkov, Katherine [1].

Tracing the Origin of Central California Amaranthus palmeri Populations and Identifying Possible Genes of Adaptation.

Palmer amaranth (Amaranthus palmeri), a native to parts of the Southwestern United States, has become one of the most harmful agricultural weeds in the Southeast, and has also established itself in parts of the Midwest and more recently in Central California. Anatomical and physiological adaptive traits characteristic to Amaranthus spp. and specifically A. palmeri, such as herbicide resistance, have aided A. palmeri in becoming an extremely opportunistic plant in many agronomic settings. Yet, it is unknown how this Southwestern native began its invasion in Central California. Prior to this proposed study, no genome-wide evaluations have been done on Central California A. palmeri populations to explore possible invasion scenarios. As part of a larger population genetic investigation of these invasions, we are asking questions such as, “What is the origin of A. palmeri populations found in California’s Central Valley? Are there any genes possibly linked to adaptation in recent emerging California populations?” The aim of this study is to elucidate the origins of the Central California populations with the use of population genetic analysis through the investigation of genetic diversity and connectivity of Central California populations relative to native and nonnative populations in other parts of the U.S. Support for different invasion scenarios will be evaluated via genotyping-by-sequencing and analysis of single nucleotide polymorphisms (SNPs) using population genetic analysis and approximate Bayesian computation (ABC). In addition, analysis of SNP data from California populations will be done to screen for overlap in outliers possibly linked to adaptation. Results so far have been obtained from surveys of herbarium records and field sampling in 2017-2018, and 2021 (when field collections were obtained from 11 Eastern US populations). These surveys reveal that A. palmeri’s distribution in the US is continuing to expand north and northeast beyond its historical Southwestern native range, suggesting that invasion is ongoing in this species, facilitated by establishment in agricultural fields. Agricultural practices in the Central Valley of California are different from the Eastern US, with recent sampling in Central California recording populations appearing in orchard and vineyard crops (with shaded understories) and in saline soils, both uncommon growing environments in other parts of the species’ range. These observations suggest that adaptation to these new agricultural conditions may be evolving. Ongoing genetic analysis will evaluate invasion scenarios for California populations and identify genes involved in adaptation. Implications of this study are the potential to facilitate future research identifying other weedy source populations for invasive A. palmeri populations, to suggest alternative strategies for more sustainable agronomic practices, and to create models for evolutionary adaptation applicable to invasiveness, evolution, and weedy plants.

1 - California State University, Fresno, Department of Biology, 2555 East San Ramon Ave, M/S SB73 , Fresno, CA, 93740, USA

agricultural weed
Amaranthus palmeri
population genomics
invasive species.

Presentation Type: Poster
Number: PPG002
Abstract ID:183
Candidate for Awards:None

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