Species coexistence in Plethodon salamander communities
A human-introduced Plethodon salamander occurs at Mountain Lake Biological Station (MLBS). The Northern Gray-Cheeked Salamander (Plethodon montanus) was captured at Mt. Rogers and released at MLBS sometime during the 1930s-40s. MLBS is outside of the species native range, yet it has successfully established and seems to be thriving.
The native Plethodon community at MLBS consists of a small species, P. cinereus, and a large species, P. glutinosus. Plethodon montanus is intermediate in size. This system has allowed us to measure the effects of body size guild niche overlap on Plethodon behavior and ecology without further manipulating communities.
Plethodon communities are divided into body size guilds, or species of comparable sizes that use shared resources in similar ways. They are also strictly terrestrial and tend to live in dense, speciose communities. Because they share similar ecological functions, they undergo intense competition for limited resources. We studied communities made up of small (P. cinereus, left), intermediate (P. montanus, center), and large (P. glutinosus, right) species.
We identified 3 Plethodon communities where the intermediate-sized species, P. montanus, was either absent, introduced by humans 80 years prior to our study, or native. In each community, we established 16, 15 x 3 m transects. The small- and large-bodied species were present in all three communities.
What are the ecological consequences of increased niche overlap? By repeatedly surveying our focal species, we were able to estimate the abundance of each species in each community. We found that the introduction of P. montanus caused a shift in community composition at MLBS, which is driven by a decline in P. cinereus.
Manuscript in prep - A. Blackman and A. Novarro
How do salamander species live together in densely populated communities? One way they coexist is by dividing space through climbing behavior. We found that different-sized species climb on plants at different rates, and that climbing behavior is affected by competition intensity. However, the effect of competition depends on the size of the species. Overall, climbable structures such as plants facilitate larger population sizes and greater species diversity.
Manuscript in review - T. Mezebish, A. Blackman, and A. Novarro
In 2016, we recorded the location of 101 P. montanus and 38 P. glutinosus at MLBS. We marked each individual to make sure that we didn't observe the same individual more than once. The heat map to the right shows occurrences of P. montanus, with red indicating areas of greatest density and blue indicating areas of lowest density. As of now, I don't have any plans for this data. If you're interested in this system and would like to run some spatial analyses, get in touch!