Spatial association between entomopathogenic and other free-living nematodes and the influence of habitat

Abstract

Spatial association between entomopathogenic and free-living nematode populations in soil were analyzed at the landscape scale. GPS coordinates were obtained for 479 locations where soil samples were collected to extract nematodes. Habitats sampled included vegetable and agronomic crop fields, grassy borders adjacent to fields, residential lawns, meadow and forested wetlands in a vegetable growing region in northwest Ohio. Free-living nematodes were classified according to trophic level (bacterivores, fungivores, carnivores, and omnivores) and life history characteristics (r-selected colonizing versus K-selected persisting species on a 1-5 scale). Spatial associations based on spatial analysis of distance indices (SADIE) were analyzed and compared among entomopathogenic nematodes and free-living nematode functional guilds defined by the classifications described above. Spatial aggregation indices (Ia) revealed that each functional guild's spatial pattern varied among habitats. Considering all data regardless of habitat, spatial aggregation indices showed that functional guilds with K-selected persisting life history traits were less aggregated, whereas those with r-selected colonizer life history traits were more aggregated. The spatial aggregation index of entomopathogenic nematodes was similar to that of the r-selected colonizer type free-living nematodes, which share several life history traits including bacteriophagy, high reproductive rates, insect phoresy, and greater abundance in grassy borders, where spatial associations between entomopathogenic and r-selected colonizing functional guilds of free-living nematodes were particularly strong. The spatial aggregation patterns of entomopathogenic and free-living nematodes, suggest that these species associate over larger areas than previously measured and that the extent of these spatial associations might be predicted by the nematode life history traits. ? 2013 .