What’s leaf got to do with it? Leaf tissue sampling for restoration genetic research

By Ashlee Wolf 

October 2020

New Mexico is home to a wide diversity of landscapes—from creosote and cactus flats of the Chihuahuan Desert to rolling hills and incised arroyos of pinyon-juniper forests to alpine peaks of the southern Rocky Mountains. The variety of climates and topography found across the state supports a parallel diversity in native plant species. Coupled with this is an unseen component of biodiversity: genetic diversity at the molecular level that can reveal the deep history of plant populations, as well as the biotic and abiotic factors that influence them. Although unseen, genetic patterns across a species’ distribution can have important implications for ecological restoration.
IAE’s Southwest Office collaborated with the New Mexico Bureau of Land Management and United States Geologic Survey (USGS) on a landscape-scale genetic study that includes several species commonly used in restoration in New Mexico. Species that we are sampling for this project include hairy false golden aster (Heterotheca villosa), side-oats grama grass (Bouteloua curtipendula), Fendler’s globemallow (Sphaeralcea fendleri), and sand dropseed (Sporobolus cryptandrus). The IAE Southwest team is helping to identify target species, collect tissue samples, and provide technical and logistical support.  I have enjoyed coordinating the field component of this project alongside our seed collection activities. The study is led by Rob Massatti, USGS Research Ecologist
at the Southwest Biological Science Center in Flagstaff, Arizona.

The following four photos are of species targeted for tissue sampling (photos by Max Licher):

Bouteloua curtipendula

Heterotheca villosa

Sphaeralcea fendleri

Sporobolus cryptandrus

All the blue stars in the map represent locations where crews collected leaves for this project

Conservation Corps of New Mexico intern, Elizabeth Buhr, collecting seed from one of the leaf tissue target species, Sphaeralcea fendleri

The goal of this research is to establish seed transfer zones. Seed transfer zones are geographic areas that tell us how far from a source population plant materials can be moved before they are no longer adapted to local conditions at a restoration site. Even when a plant species is native and locally present, introducing plant materials (seeds and/or container plants) that are not adapted to the local environment, or are distantly related to nearby populations of the same species, can lead to undesirable effects and make it more difficult to meet restoration goals.

In lieu of research guiding seed transfer for each restoration species, practitioners often use generalized seed transfer zones based on climate (such as Provisional Seed Zones) and/or ecoregions defined by the dominant vegetation and soil characteristics (such as EPA Level III Ecoregions). However, due to other factors that influence plants’ adaptations to their environments (e.g. soils, topography, microclimates), not to mention that all species are not influenced by environments in the same way, these generalized seed transfer zones are not always effective in making sure seeds are well-suited to a restoration site. Landscape-scale genetic patterns can reveal both adaptation to regional environmental conditions and the deeper history of relationships among a species’ populations. In turn, this information can be applied to delineate species-specific seed transfer zones that ensure plant materials are locally-adapted and that protect species’ innate patterns of genetic diversity.

For the field component of this study, field crews in Santa Fe and Carlsbad, New Mexico have been collecting leaves from species that are important for restoration across the state. Crews collect 3-5 leaves from 10 individuals in a population and place the samples in plastic bags with silica to preserve the leaf tissue. So far, our crews have collected leaves from over 100 populations across the state. Leaf samples collected by field crews this summer will be shipped to Flagstaff and processed using molecular techniques; genomic data will be used to reveal relationships and genetic patterns across the landscape.

IAE Southwest hosts a collaborative regional program to improve the availability of ecologically appropriate seed for restoration called the Southwest Seed Partnership (SWSP).  Major gaps in research guiding appropriate seed movement has hindered our work and even slowed down some of our production efforts.  Results of this study and future studies of its kind will be highly beneficial to SWSP stakeholders and provide the information we need to better support our local ecology.

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