Predicting Plant Hybrids: UNR Researchers Develop Method to Forecast Hybrid Zones in Fragmented Landscapes

In the vast, rugged expanses of the western United States, where landscapes are increasingly carved up by roads, agriculture, and urban development, a team of researchers from the University of Nevada, Reno (UNR) has unveiled a groundbreaking method to predict where plant hybrids will thrive. This innovation, detailed in recent studies, focuses on mosaic hybrid zones—patchy areas where closely related plant species interbreed, creating offspring with blended genetic traits suited to unique environmental niches. Hybridization, the process by which two different plant varieties or species cross-pollinate to produce hybrid offspring, has long been recognized as a driver of biodiversity, but predicting these zones in fragmented habitats has proven challenging until now.

The Great Basin region, spanning about 200,000 square miles across Nevada and surrounding states, serves as a prime example of fragmented landscapes. Here, dominant shrubs like big sagebrush and rubber rabbitbrush face pressures from wildfires, invasive grasses, and shifting climates. By leveraging environmental data such as precipitation, temperature, and elevation, UNR scientists can now reliably forecast hybrid hotspots without needing extensive genetic sampling on the ground. This approach not only expands our understanding of plant evolution but also offers practical tools for land managers aiming to restore ecosystems after disturbances.

Understanding fragmented landscapes starts with recognizing how human activities and natural events break continuous habitats into isolated patches. This fragmentation disrupts gene flow—the movement of genetic material between populations—potentially leading to inbreeding and reduced adaptability. However, hybrids emerging in these mosaics can act as bridges, stitching together genetic diversity and enhancing resilience.

🌿 Decoding Mosaic Hybrid Zones in Plants

Mosaic hybrid zones differ from traditional tension zones, which form narrow bands where two species meet along environmental gradients. Instead, mosaics appear as scattered patches within overlapping ranges of parental species, driven by fine-scale environmental variation rather than just geography. In these zones, hybrids occupy intermediate conditions—for instance, spots with moderate precipitation where neither parent dominates.

Historically, plant hybridization was viewed with skepticism, sometimes labeled as rare or maladaptive. Yet, modern genomics reveals it's a fundamental evolutionary force, generating novel trait combinations that fuel adaptation. In the western U.S., glacial cycles during the Pleistocene era isolated plant populations in mountain ranges and valleys, fostering genetic lineages that now hybridize as climates warm.

For example, consider rubber rabbitbrush (Ericameria nauseosa), a resilient shrub common in disturbed areas. Its varieties hybridize in zones with balanced seasonal precipitation, producing plants better equipped for variable conditions. Similarly, big sagebrush (Artemisia tridentata), a keystone species supporting sage-grouse and other wildlife, forms hybrids that extend its ecological footprint.

• Hybrids fill environmental gaps, increasing total species range by significant margins—often making distributions "much, much smaller" if ignored.
• These zones promote genetic variation, the raw material for natural selection in dynamic environments.
• Mosaics are prevalent in topographically complex areas like the Great Basin, where elevation and microclimates create diverse niches.

This pattern holds across multiple taxa, suggesting a widespread phenomenon ripe for prediction and management.

🎓 The UNR Research Breakthrough

Led by co-authors Trevor Faske (Ph.D. from UNR's Ecology, Evolution and Conservation Biology program, class of 2024) and Thomas Parchman (Professor of Biology at UNR), alongside Elizabeth Leger (Foundation Professor of Biology at UNR) and Rob Massatti (formerly USGS, now co-founder of Landscape Stewardship Collective), the team analyzed six ecologically vital plant species in the West. Their work, building on a 2025 PNAS publication titled "Suturing fragmented landscapes: Mosaic hybrid zones in plants may facilitate ecosystem resiliency," demonstrates that simple environmental variables outperform complex genomic surveys for locating hybrids.

Methods involved collecting occurrence data from field surveys and herbarium records, layering it with high-resolution climate grids (e.g., mean annual precipitation, winter lows, summer highs), and applying species distribution models. Genomic confirmation via DNA sequencing verified predictions, showing hybrids cluster in predicted intermediate habitats with high accuracy.

"Environmental variation does an amazing job of predicting where you're going to find species A, species B, or hybrids," Parchman noted. Across rabbitbrush, sagebrush, and globemallow (Sphaeralcea spp.), patterns were consistent, with mosaic zones dotting the landscape like a patchwork quilt.

Key predictors included:

• Precipitation seasonality, favoring hybrids in transitional wet-dry areas.
• Temperature extremes, where hybrids tolerate moderate stresses.
• Elevation gradients, creating microhabitats amid fragmentation.

This predictive power scales regionally, applicable from Nevada's deserts to broader western rangelands.

🔬 Detailed Findings and Examples

The study's three focal systems highlight real-world applications. In big sagebrush, hybrids between subspecies expand occupancy by bridging arid lowlands and moister uplands, crucial post-wildfire. Rubber rabbitbrush hybrids thrive in disturbed sites, aiding soil stabilization. Globemallow variants show similar mosaics, supporting pollinators in fragmented meadows.

Statistics underscore impact: without hybrids, modeled ranges shrink dramatically, limiting resilience. Under climate projections, hybrid zones shift upslope, tracking warming trends and potentially outpacing parental species.

"Genetic diversity is the agent that natural selection acts upon," Faske explained. "You need variation for adaptation." Field data confirmed over 80% overlap between predicted and observed hybrids in tested areas.

For deeper insights, explore the full study via PNAS publication or UNR's detailed coverage at Nevada Today.

🌍 Implications for Restoration Ecology

Fragmentation exacerbates wildfire cycles in sagebrush ecosystems, where invasives like cheatgrass dominate burns. Traditional restoration seeds pure parental lines, but hybrids offer superior adaptability. UNR's models guide seed mixes, prioritizing local hybrids to boost establishment rates.

The Landscape Stewardship Collective, founded by Faske and Massatti, is crafting genetic management plans for 30 priority species, partnering with the Forest Service and BLM. Actionable steps for practitioners:

• Map sites using free tools like ClimateNA for intermediate env projections.
• Source diverse seeds from predicted hybrid zones via native plant suppliers.
• Monitor post-planting with eDNA for hybrid success.

Such strategies enhance rangeland health, benefiting livestock, wildlife, and carbon sequestration. Researchers driving these advances often pursue research jobs in conservation biology, where field and lab skills converge.

☀️ Adapting to Climate Change Through Hybrids

As climates shift, plants must migrate or adapt rapidly. Hybrids accelerate this by combining drought tolerance from one parent with cold resistance from another. In simulations, including mosaics maintains or grows distributions under RCP scenarios, countering fragmentation's gene flow barriers.

This echoes broader evolutionary biology: hybrids as "creative destruction," sparking speciation. Yet, balanced management avoids issues like maladaptive introgression. UNR's work empowers proactive stewardship, positioning hybrids as allies in resilience.

Professionals in faculty positions at institutions like UNR lead such efforts, mentoring the next generation in evolutionary ecology.

Photo by Kelsy Gagnebin on Unsplash

📈 Future Directions and Opportunities

Expanding models to more species and finer scales promises wider impact. Integrating remote sensing and AI could real-time track zone shifts. For aspiring ecologists, this field offers career advice on leveraging interdisciplinary skills.

In summary, UNR's predictive method transforms how we view hybrids—from anomalies to ecosystem sutures. Land managers, policymakers, and academics alike stand to benefit. Share your thoughts in the comments below, rate courses or professors at Rate My Professor, and explore openings at Higher Ed Jobs, University Jobs, or post your own at Recruitment. Stay ahead in higher education with Higher Ed Career Advice.