Fescue Rescue: ecology and recovery of Guadalupe fescue (Festuca ligulata), an endangered grass of the northern Sierra Madre Oriental

Background/Question/Methods

Guadalupe fescue (Festuca ligulata) is an endangered perennial grass that is endemic to the Sky Islands of the northern Sierra Madre Oriental. The species was listed as endangered in the USA under the Endangered Species Act in 2017 and is a species of conservation concern in Mexico. Little is known about the ecology and reproductive biology of the species, which are critical to recovery actions. We report here on the geographical distribution, demography, habitat requirements, response to fire, and reproduction of Guadalupe fescue, as well as on in situ transplant trials. Prior to the study, only two Guadalupe fescue populations, with a total of fewer than 5000 plants, had been confirmed—one in the Maderas del Carmen Protected Area (MCPA) in Coahuila, Mexico, and the other in the Chisos Mountains of Big Bend National Park (BIBE), Texas, USA. For subsets of each population, we documented plant vigor, reproductive output, nearest neighbor distance, and microenvironmental conditions. We collected and germinated seeds from each population. Seeds were also germinated from 25-yr old collections from BIBE. We implemented an initial transplant trial in Mexico. Finally, we re-censused plants in BIBE six months after a low-moderate severity wildfire.

Results/Conclusions

For 99 plants at MCPA and 335 at BIBE, we found that Guadalupe fescue grows within a narrow elevational range (2066-2394 m), in single canyons, on rocky microsites with relatively open canopy and forest floor conditions, compared to random microsites. 70% of plants were reproducing at MCPA, 51% at BIBE. Seed fill rates were 61% at MCPA, 31% at BIBE. Germination for recently collected seed was 33% for MCPA and 8% for BIBE; germination was 92% for 25-yr old seeds stored in sub-zero conditions. Five of 14 transplanted seedlings survived through the monsoon season. We discovered an additional thriving population in Coahuila. Survival from before to after the South Rim 4 Wildfire was 44%. Only 7% of those survivors reproduced, compared to 51% before the fire. The number of spikelets produced by the censused population declined from 8151 pre-fire to 290 post-fire. These results suggest that (1) Guadalupe fescue grows in a narrow environmental range, (2) two small populations in Mexico are thriving, (3) population augmentation is feasible, and (4) wildfire had strong negative short-term effects, with longer-term results pending. These are important baseline ecological data for the development of a long-term recovery plan for Guadalupe fescue.