GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 209-10
Presentation Time: 3:45 PM


ALUMBAUGH, Jamie L., Biological Sciences, Northern Illinois University, Dekalb, IL 60115; Geography, University of Tennessee, Knoxville, TN 37996

Within the genus Macronycteris, interspecific morphological differences are small, but sexual dimorphism is high and intraspecific geographic variation can be dramatic. On Madagascar, cranio-dental size has been previously correlated with bioclimatic variation. The presence of a recently extinct species, M. besaoka, from Anjohibe Cave in northwestern Madagascar suggests that this genus was once more morphologically diverse. Northwestern Madagascar became drier and less mesic starting at 4,900 years BP or even earlier, which possibly contributed to the extinction of M. besaoka. Bioclimatic shifts, as well as anthropogenic impacts, have likely affected Macronycteris communities elsewhere on the island. This study examines Macronycteris subfossils from Mitoho Cave in southwestern Madagascar, which range in age from ≥ 8,000 years BP to modern. Like Anjohibe Cave in the north, Mitoho Cave is still occupied by Macronycteris, and isotopic and palynological evidence suggests that the surrounding region was more mesic during the Pleistocene deglaciation and into the Holocene, with local environmental desiccation starting approximately 3,000 years BP. This study reports that Macronycteris community in the southwest has only recently changed, as evidenced by differences in cranio-dental size and shape between modern and subfossil specimens. Moreover, these subfossils are not statistically similar in shape to any modern M. commersoni population on Madagascar. These results indicate the existence of a previously undescribed morphotype and recent disturbance of Tsimanampesotse National Park’s Macronycteris community, which is most likely a result of deforestation and predation by the local human population rather than natural environmental changes.