Understanding land use decisions that lead to deforestation is essential to biodiversity conservation. The MODEF project incorporates expertise from four scientific disciplines, addressing deforestation through the use of socioeconomic and biodiversity surveys, mathematical and statistical modeling, and geographic information systems. We have three goals: (1) develop a theoretical framework for understanding the interrelationships between socioeconomic systems and land use; (2) assess the impact of current and projected land use on the viability of endangered species; and (3) provide an interdisciplinary approach to human and biodiversity field studies, quantitative modeling techniques, and GIS applications. In my role as biodiversity coordinator, I am conducting population surveys (lemurs, chameleons, birds, rodents, insectivores, dung beetles) and habitat assessments (forest structure, direct anthropogenic effects) on transects in 12 sites around Ranomafana National Park. These transects link forest edges to intact interior forest, reflecting disturbance gradients associated with nearby villages and their land use patterns.

In my previous research at Andringitra and Vevembe, I have studied the role of ecology in the interaction of red-fronted brown lemurs, white-fronted lemurs and their hybrids. Specifically, I examine how shifts in local habitat structure, demography, feeding behavior, and behavioral interactions may impact speciation. Among the significant findings is the identification of novel genetic markers within the large hybrid zone. This strongly suggests that gene flow through this boundary population is restricted, thus facilitating the divergence of the two species. I have recorded variation in habitat structure, food availability, social structure, and morphology across populations. These factors may function as mechanisms limiting gene flow across the hybrid zone. In particular, poor habitat quality and perhaps increased intergroup agonism may inhibit dispersal. Moreover, morphological characters linked to sexual selection vary across populations, suggesting different strategies for mate competition and/or mate choice.

In the next phase of research, my objective is to expand previous research centered at Andringitra and Vevembe to include all sites within the restricted range of white-collared lemurs. I intend to investigate patterns of gene flow and population structure to establish demographic trends, connectivity among fragmented populations, and, ultimately, risks of extirpation and extinction for this critically endangered taxon. This project will also include comparisons of pure populations of each parental species adjacent to the hybrid zone with those found in habitats separated by major biogeographic boundaries (the Andringitra Massif and larger river systems).

Johnson SE, Gordon AD, Stumpf RM, Overdorff DJ, and Wright PC (2005) Morphological variation in populations of Eulemur albocollaris and E. fulvus rufus. International Journal of Primatology 26(6):1399-1416.

Irwin MT, Johnson SE, and Wright PC (2005) The state of lemur conservation in south-eastern Madagascar: Population and habitat assessments for diurnal lemurs using surveys, satellite imagery and GIS. Oryx 39(2):204-218.

Overdorff DJ, and Johnson S (2004) Eulemur, true lemurs. In SM Goodman and J Benstead (eds.): The Natural History of Madagascar. Chicago: University of Chicago Press, pp 1320-1324.

Dalecky A, Kerdelhué C, Johnson S, Razafindratsita VR, Grassi C, Razafiarimalala AC, Overdorff D, and Rasplus J-Y (2004) Moraceae, Ficus and associated fauna. In SM Goodman and J Benstead (eds.): The Natural History of Madagascar. Chicago: University of Chicago Press, pp 322-334.

Wyner Y, Johnson S, Stumpf R, and DeSalle R (2002) A genetic assessment of a white-collared X red-fronted lemur hybrid zone at Andringitra, Madagascar. American Journal of Primatology 57(2):51-66.

Johnson S, and Wyner Y (2000) Notes on the biogeography of E. f. albocollaris. Lemur News 5:25-28.

Johnson S, and Overdorff D (1999) A census of brown lemurs (Eulemur fulvus sspp.) in southeastern Madagascar: methods-testing and conservation implications. American Journal of Primatology 47(10):51-60.