Invasion Ecology of the South American Cactus Moth

Species invasions represent an important threat to the structure and function associated with ecological communities.  Escaped biological control organisms like the South American cactus moth (Cactoblastis cactorum) provide a number of unique opportunities to assess the mechanism(s) associated with invasion success.  Our work has demonstrated that there are multiple ecotypes of C. cactorum in the native range and that these differ in their host association (Marsico et al. 2011, Brooks et al. 2012, Brooks et al. in press).  This host association is also apparent in the exotic distribution of the moth across the southern United States (Sauby et al. 2012).  Our current work is focused on assessing the role of specific host traits that determine the differential patterns of infestation that we have observed.

Trait-based Ecology of

Prickly Pear - Cactus Insect Associations

The implications of understanding the role that host traits play in the dynamics of associated consumers are far-reaching. The vast majority of agricultural pests and emerging infections pathogens are capable of attacking hosts of more than one species.  Theoretical work in our lab (Brooks and Zhang 2010) and by others has suggested that it is the distribution of these traits within a host community that constrains consumer dynamics.  Our lab is focused on the suite of functionally-critical host traits, understanding the mechanisms that generate diversity in these traits, and using that information to predict consumer fitness.  Prior work in our lab suggests that there may be a limited suite of host traits that are important in determining the distribution of cactus moths in their native and non-native ranges.

The Role of Host Traits in Cactus Moth Population Dynamics
Interactions Among Cactophilic & Cactophagous Insects

There are myriad species that are commonly associated with prickly pear cactus.  Just among the Diptera there are species of Drosophilidae (like the D. hamatofolia shown at left), Syrphidae and Tephritidae that can be found in Texas alone.  Many of these Diptera and some Lepidoptera (e.g., larvae of some Tineadae) feed on the communities of microorganisms inside rotting prickly pear tissue. There has been extensive work on the host specificity that emerges from these interactions, but little on the potential indirect effects among cactophagous insects that feed directly on Opuntia tissues and cactophilic species that specialize on yeasts and other microorganisms which colonize rotting tissue. We are just beginning to culture some of these species in an effort to examine indirect interactions among these species and the host plants.

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