Finding the gaps in crop wild relative conservation

These data came from online databases like PlantSearch, the Global Biodiversity Information Facility, and GRIN-Global. Their search revealed where plants occur in their natural habitats, at least historically.

The authors combined these occurrence points with climatic and topographic information to predict the native range of each taxon.

“Modeling allows us to make maps that show the general distribution of the species using point data based on where we’ve collected them in the wild,” Greene says. “When you bring in other characteristics like environmental variables, then we can predict this envelope on the landscape that has the sort of conditions where we’d expect these species to actually exist.”

Native ranges can also point the team toward specific collection sites that aren’t currently represented in conservation repositories, including for certain characteristics like drought or cold tolerance. By collecting in areas where these conditions are likely to occur, they can get a broader range of genetic diversity for use in plant breeding.

To find the gaps, researchers compared their modeled ranges against the sites where samples had already been taken. Locations not yet sampled represent gaps in current ex situ conservation. They found major ex situ conservation gaps for 93.3% of all CWR, including 83 taxa completely absent from conservation repositories.

Then the team added another layer: in situ conservation. Is the plant conserved in its natural habitat through habitat preservation?

The researchers scored for in situ conservation using the representation of taxon ranges within locations listed in the World Database on Protected Areas (WDPA). This includes national parks, wilderness areas, and many other open-space conservation categories.

Combining in situ and ex situ conservation analysis, the team assigned each CWR a current conservation score. Shockingly, they categorized 58.8% of all taxa as in urgent need of further conservation action based on these combined in situ and ex situ assessments.

Finally, putting all these conservation maps together helped the group identify taxonomic richness hotspots—locations where the ranges of multiple CWR species overlap.

“Hotspots can be very useful both for collections and for in situ conservation,” says Williams, who directs the USDA program for collection expeditions across the United States and in other countries. “Not only can we sometimes collect multiple CWR on one expedition, we can prioritize these areas for conservation.”

The study provides an intense and eye-opening report of what we’re missing, making it easier to prioritize which species we need to collect now and how to direct further conservation efforts. It’s all about being strategic to maximize limited resources and protect the CWR most in need.

Conservation Action

Conservation efforts for native CWR are already well underway both in situ and ex situ.

In the wild, the Wild Chile Botanical Area in the Tumacacori Highlands of southern Arizona stands as one of the few national preserves dedicated to protecting a crop wild relative—the chiltepin pepper (Capsicum annuum var. glabriusculum). The Cranberry Glades Botanical Area in the Monongahela National Forest in West Virginia and the Cranberry Bog Botanical Area in the Olympic National Forest in Washington are examples of other preserves dedicated to CWR. Their success hints at the potential of the modeling created by Khoury, Greene, Williams, and their collaborators. The hotspots identified in the modeling provide strong foundations for choosing other areas to set aside.

“This gap analysis provides basic knowledge for land management agencies that are responsible for setting up natural reserves for CWR—like the BLM and the U.S. Forest Service. I hope it provides them the information they need to secure these materials in the landscape,” Greene says.

Meanwhile, new projects are underway that partner the boots-on-the-ground power of the U.S. Forest Service to support conservation of CWR with the capacity of the USDA-ARS and other institutions to conserve these resources in ex situ collections. Williams and other ARS members collaborated with the U.S. Forest Service to create a framework for this partnership. In fact, Williams completed one project so far that studied 45 populations of wild cranberries in National Forests across the country for consideration as in situ preserves for CWR. Williams was part of a team that published preliminary findings on the breadth of genetic diversity in cranberries in a recent Plants article (https://doi.org/10.3390/plants9111446).

“We’ve limited our work so far to conservation of CWR on National Forests,” Williams says. “We hope that collaboration can be extended to other land management entities in the U.S.”

A central purpose of the gap analysis is to guide strategic decision making for plants that are often out of the spotlight. Partnerships between land management agencies are a great start, but another critical step is bringing the project to the public. One way to increase education is through the help of botanic gardens in the U.S., which receive more than 120 million visitors in an average year.

“Based on current conservation activity, it would take perhaps 50 years to get everything done based on the information we generated,” Khoury says. “We really need to generate momentum, more collaborations, more resources, and in five years, accomplish the conservation activities that will protect these plants for the future.”

Pioneers in CWR research and conservation, like Jack Harlan, would be proud to see the progress enabled by database searches and modeling. With the dedication of this research team, we have everything we need to conserve these important cultural-genetic-natural resources, from sunflower to wild grape, cranberry to chile pepper.