Habitat Fragmentation

Responses to habitat fragmentation

Habitat fragmentation studies have predominantly emphasized among-population processes, that is, the empirical and theoretical investigation of the causes and consequences of population differentiation. While this line of research is important, I have additionally focused on a rarely-studied aspect of habitat fragmentation: the behavioral and genetic changes that occur within isolated populations that may impact their viability. Fragmentation-induced alterations to dispersal and within-population processes (e.g. sociobiology - comprising kin interactions, social organization, and mating system) likely impinge on reproductive success and thus are fundamental to population declines and extinctions. For my doctoral work, I used large-scale non-invasive genetic sampling (hair) to examine within-population processes of southern hairy-nosed wombats (Lasiorhinus latifrons) in contiguous and fragmented habitats. To achieve this, I used GIS mapping to identify outliers to the major wombat population centers, and then visited over 90% of these in multi-month fieldtrips involving 15,000 km and 12 flat tires. In addition to finding that females are the dispersing sex, which is exceedingly rare in mammals, I found that habitat fragmentation affected sociobiology. This work resulted in papers in Molecular Ecology (Walker et al. 2007, 2008a, 2008b) the Journal of Mammalogy (Walker et al. 2006), and PLOS ONE (Alpers et al. 2016).

Other within-population research includes 1) investigation of demographic changes over 20 years in a small population of De Brazza's monkeys (Cercopithecus neglectus) in Kisere Forest, Kenya, where I worked as a Fulbright Scholar (Walker & Sajita 2011); and, 2) determination of which Tammar wallabies (Macropus eugenii) to use in a reintroduction program, which has subsequently been very successful.

For among-population questions related to fragmentation of habitat, I have collaborated on projects 1) examining phylogeography and recent habitat fragmentation of squirrel gliders (Petaurus norfolcensis) (Pavlova et al. 2010, Taylor et al. 2011), and 2) evaluating via simulation the most effective approaches for identifying recent barriers to gene flow (Blair et al. 2012).