Working with various organizations over the past 8 years, I have conducted extensive field research in Peru, Venezuela, Costa Rica, Belize, Kenya, and the U.S. The primary theme of my research has been the structuring of biodiversity patterns across habitat types and disturbance regimes, and has focused on taxa that include butterflies, ants, feather-wing beetles, dung beetles, and scorpionflies.

Recent research is examining the causes and consequences of species loss for the functioning of communities, with a focus on the interactions between mammals, plants, and dung beetles. Growing evidence suggests that accelerating species extinctions could lead to rapid ecosystem destabilization and decay. Development of conservation management strategies will depend on an understanding of both the mechanisms and the consequences of extinction for ecological functioning. Unfortunately, studies of both processes are rarely linked.

Photo by André Bärtschi, www.wildtropix.com

Local Extinction Mechanisms
Intensifying levels of land-use are altering landscapes, creating isolated patches of habitat. Land-use and habitat fragmentation are the leading cause of biodiversity loss. Dung beetles are a useful group for answering one piece of the extinction mechanism puzzle. The neotropics boast an incredible diversity of dung beetles. Standardized sampling methods quickly yield abundance data for the entire dung beetle community of a study site. Dung beetles are linked to mammal populations through their dependence on dung and exhibit a graded response to various types of disturbance, including fragmentation.

My research on forested islands of Guri Lake, Venezuela is revealing the mechanisms behind local extinctions of dung beetles and the factors that influence the structure of the dung beetle guild. Interestingly, large-bodied species are at especially high extinction risk. What causes local extinctions and population declines of dung beetle species in forest fragments and why is the effect stronger on large-bodied species? Are there thresholds at which mechanisms change with fragment size? Answering these questions requires examination of the interplay between beetle species traits, including movement patterns, and changing habitat area, habitat quality, and food web dynamics.

Species Diversity and Ecological Function
Species loss may cause functional shifts that disrupt ecological processes. Several studies have examined the relationship between diversity and ecological function, although most have measured plant diversity and primary production in grassland ecosystems. Artificially assembled communities are poor at helping us understand real communities where species are not lost randomly. Few studies have examined species diversity and ecosystem functioning in tropical forests where most of the earth’s biodiversity is concentrated. Arthropods represent the majority of this diversity, occupying many functional niches and microhabitats.

Dung beetles comprise a keystone guild in the tropics by acting as secondary seed dispersers for monkey-dispersed seeds. By burying dung and the seeds it contains, beetles protect seeds that otherwise suffer from intense rodent predation, and thereby greatly increase seed survival. Beetle-mediated dung burial further contributes to ecosystem functioning through nutrient cycling and soil conditioning, increasing the availability of nitrogen and phosphorus to plants. Dung burial also helps control helminth parasite and pest fly populations. Larger-bodied beetle species bury more dung and contribute the bulk of ecological function. The selective extinction of many larger-bodied species of dung beetles in response to fragmentation, hunting of mammals, and other anthropogenic impacts can rapidly result in the disruption of this ecological function. I am examining the nature of this relationship, with particular focus on the contribution of large extinction-prone dung beetle species to seedling recruitment across different habitat types and disturbance regimes.