Genetic Assessment of Beardless Chinchweed

As climate change impacts the environment at an accelerated pace, the conservation of endangered plant species has become increasingly necessary. A 2022–2025 study coordinated through the Desert Southwest CESU Network supported a collaborative research partnership between Northern Arizona University and National Park Service. Researcher Dr. Sara Souther, in collaboration with land management agency leads, JoAnn Balack, Julie Crawford and Angela Dahlby, sought solutions for the preservation of beardless chinchweed in Sky Islands region of Coronado National Monument. Prior to this study, investigations into the conservation of plants in the Sky Islands were very limited. 

Beardless chinchweed is an endangered plant native to the Sky Islands, with 80% of known specimens located within Coronado National Monument. The spatial concentration of beardless chinchweed in Coronado makes a single disturbance potentially perilous to the species, so it is particularly vulnerable to the effects of climate change. It is vital that scientists act pre-emptively to stop extinction and shift the trajectory towards recovery. The study focused on understanding genetic variation, critical for long-term persistence of beardless chinchweed and essential for designing effective conservation strategies. 

To begin their study, Souther’s lab examined the genes of beardless chinchweed using reduced representation genomic sequencing (or RADSeq). RADSeq targets specific parts of a genome to identify genetic variation, which can then be analyzed in relation to environmental and climate factors affecting beardless chinchweed. To gather this data, the scientists retrieved leaf samples from several populations of beardless chinchweed and extracted DNA at the University of Minnesota Genomics Facility. 

Next, they developed a restoration garden to test whether patterns of genetic variation are adaptive – in other words, whether the genetic differences identified among populations translated into traits that improved performance under particular environmental conditions. The team established an experimental restoration garden using seeds collected from seed collected from 25 different locations spanning the region from the southern Huachuca Mountains to the Santa Rita Mountains. The effort was paired with advanced genetic analyses using the RADSeq data to identify specific genes and genetic markers potentially associated with environmental adaptation. By evaluating these populations in a common garden setting, the researchers were able to better understand how different populations respond to environmental conditions in order to guide future restoration efforts.

According to the results, the researchers found that gene flow – or the movement of pollen and seed - between beardless chinchweed populations was low, particularly among populations isolated from the CNM. When gene flow is low, the likelihood of inbreeding depression increases. Inbreeding depression may make extinction more likely and render populations less able to persist when conditions are unfavorable, such as during drought events. The scientists carefully weighed the risks and benefits of increasing genetic diversity in the plant’s small, isolated populations. They recognized that introducing new genetic material could strengthen the species, but only if done strategically. Their solution was to improve gene flow by creating a network of suitable habitats that would reconnect isolated groups and reduce inbreeding. They envisioned a series of directly seeded “steppingstone” restoration gardens placed across the landscape, each acting as a link in a future corridor that would allow plants from more genetically diverse populations to mix and spread.

Using these insights, the team developed practical tools and strategies to support park management. Updated population estimates for Coronado enabled them to create a detailed map of existing populations and optimal locations for restoration gardens. They combined this mapping effort with a comprehensive restoration plan that can guide park managers in future restoration efforts.

Environmental studies such as this one are becoming increasingly important as climate change continues to intensify. By integrating diverse methods for gathering data, this team of scientists gained a deeper understanding of beardless chinchweed that will be critical for its survival as a species. Identifying conservation pathways to maintain connectivity and support demographic and genetic resilience is vital for preserving the unique landscape of Coronado National Monument.

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