Spatial Ecology of Food Webs
Karthik Ram Ph.D.
- 2008. C.J. Dugaw & K. Ram. Consequences of heterogeneity in mortality on the long-term persistence of a seasonal microparasite Ecology In review
- 2008. Ram et al. Metapopulation dynamics override local limits on long-term parasite persistence. Ecology.89:12 3290-3297
- 2008. Ram et al. Dynamics of a subterranean trophic cascade in space and time. J. Nematology. 40(2):85-92
- 2007. Gruner, D, Ram, K and Strong, D.R. Soil mediates the interaction of coexisting entomopathogenic nematodes with an insect host. J. Invert Path. 94
2320 Storer Hall
1 Shields Ave
Davis, CA 95616
karthikxx [at] ucdavis [dot] edu [remove xx]
Dissertation Research: Population Biology of Microparasites
Trophic cascades can act as an important mechanism for the maintenance of plant biomass, species diversity, and ecosystem function in a variety of ecosystems (Shurin et al., 2002; Stenseth et al., 2002; Schmitz, 2006). The top predator is much larger than its prey and consumes more than one prey individual over the course of its lifespan (Lafferty and Kuris, 2002). Smaller organisms which don't fit this framework, such as parasites, parasitoids, and diseases, also can induce cascades, but empirical data are limited primarily to a small set of cases. The long-term outcomes in such cases may differ from 'typical' trophic cascades because a) the consumers are typically smaller than prey, making them highly susceptible to vagaries of the abiotic environment (Gubbins and Gilligan, 1997), and b) smaller organisms are limited in their spatial extent (Kotliar and Wiens, 1990).
In California's coastal prairie, a microparasitic entomopathogenic nematode Heterohabditis marelatus is the natural enemy of the ghost moth (Hepialus californicus) larvae which are root feeding herbivores of the bush lupine (Lupinus arboreus). By suppressing ghost moths, entomopathogenic nematodes protect lupines and increase seed set, growth and survivorship. In their absence, ghost moths can decimate large stands of lupines and can potentially alter the composition of the plant community. Entomopathogenic nematodes are however, highly extinction prone due to dual abiotic and biotic stressors.
In a highly seasonal abiotic environment with intrinsic variation in soils, vegetation structure, and host availability, natural populations this microparasite persisted at high incidence at some but not all sites. In my research I am trying to understand how different mechanisms such as survivorship, dispersal and spatial structure of host population affect long-term persistence of these entomopathogenic nematodes.