PATCHINESS IN POPULATIONS OF ENTOMOPATHOGENIC NEMATODES

The distribution and abundance of entomopathogenic nematodes within an d among sites were investigated by taking soil samples along transects at several locations in southwestern New Jersey and by assaying for n ematodes using the Galleria-bait method. Entomopathogenic nematodes we re found at 12 of 13 sites (92.3%) and in 72 of 600 soil samples (12.0 %). Heterorhabditids (probably Heterorhabditis bacteriophora) were fou nd in 60 samples from 12 sites. Steinernematids were rarer, with Stein ernema glaseri being found in 8 samples from 3 sites, S. feltiae (=bib ionis) in 4 samples from 2 sites, and S. carpocapsae in 2 samples from 2 sites. Heterorhabditids differed significantly in abundance among s ites with from 0 to 47.5% of samples from individual sites proving pos itive. Overall, heterorhabditids were equally abundant in turf and wee dy habitats but significantly less abundant in closed-canopy forest wh ere no positive records were obtained. Within sites, heterorhabditids were aggregated, with individual soil samples being much more likely t o contain sufficient nematodes to infect multiple Galleria larvae than predicted based on the total number of positive soil samples and a ra ndom distribution. However, this patchiness occurred on a relatively s mall scale since the occurrences of nematodes in successive soil sampl es taken at 4-m intervals along transects were statistically independe nt of one another. Spatial heterogeneity is probably a fundamental asp ect of the population biology of these species and has important ramif ications for their population dynamics, population genetics, and commu nity structure. (C)1994 Acodemic Press, Inc.