Habitat and Conservation of the Endemic Grenada Frog (Pristimantis euphronides)

Abstract

Invasive species, loss of habitat and climate change are just some of the many threats accelerating biodiversity loss. Understanding their impacts on endangered species is key to implementing effective conservation. The endemic Grenada frog (Pristimantis euphronides) is found only in high elevation cloud forests, habitat that is being invaded by the introduced Lesser Antillean frog (Eleutherodactylus johnstonei) and threatened by climate change. Between 2004 and 2020, our field team surveyed three key sites in the central highlands of Grenada to monitor populations of P. euphronides. Using generalized linear models and Spearman’s rank analysis, I found that the invasive E. johnstonei had a positive relationship with the endemic P. euphronides within each location (𝑡𝑡 = 2.830, 𝑑𝑑𝑑𝑑 = 159, 𝑝𝑝 = 0.005), but a negative correlation overall (𝜌𝜌=−0. 467). This shows the broad impacts of E. johnstonei on P. euphronidesdespite observations that the two species tend to increase together within each site. Sites differed significantly in abundance of P. euphronides, indicating that the differences in conditions at each site are worth examining further. We also created a potential habitat map that produced a larger potential range than previously identified, but more scouting and surveys are needed to properly assess the occupancy of this area. Because the overall negative impact of the invasive Lesser Antillean frog on the endemic Grenada frog was not detectable within sites where the relationship was positive, the importance of wider assessments to fully disentangle the myriad of pressures facing endangered species cannot be overstated.