Distribution of entomopathogenic nematodes in an Irish sand dune system

Abstract

A 100 × 800 m section of the sand dune system at North Bull Island, Dublin Bay, Ireland, was surveyed for entomopathogenic nematodes (EPN) by baiting soil cores with Galleria mellonella in July and August of 2001 and 2002. Two species were found: Steinernema feltiae (2.5 and 3.2% of cores) and Heterorhabditis downesi (1.9 and 3.8% of cores in 2001 and 2002, respectively). In each year, two colour variants of the G. mellonella cadavers containing H. downesi were found: purple and yellow. In both 2001 and 2002, H. downesi was most prevalent in the front 20 m of the dune system. Steinernema feltiae occurrence generally increased with distance into the dunes. In 2002, H. downesi was recovered most often in sandy paths than any other habitat surveyed but there was no habitat differentiation for S. feltiae. Human traffic may be an important factor in the distribution of both EPN and their insect hosts on Bull Island.

Intraspecific variation among isolates of the entomopathogenic nematode Steinernema feltiae from Bull Island, Ireland

“…A shared colonisation origin on Bull Island is the most likely explanation for the genetic similarity of the widely separated 1E(I) and 75J(I) (distance between soil cores 761.64 m); however, it is also possible that sand transported by human activities may have given rise to this disjunct in distribution. In terms of unaided dispersal, the chance of direct gene flow between two populations from either end of the 800 × 100 m sample area of Rolston et al (2005) is low. The greater the geographic distance between populations, the smaller chance of gene flow, which may eventually give rise to genetic isolation by distance (Page & Holmes, 1998).…”

“…Information on gene flow between EPN populations is sorely lacking (see Blouin et al, 1999) and is in need of urgent investigation in order to attempt to estimate both the natural diversity of EPN populations and the potential impact of introduced alien or commercially applied nematodes on natural populations in the soil. The EPN populations of Bull Island may be ideal for an extended study of the level of gene flow within each of the two species that exist there due to their seemingly patchy population structures and the variable habitats within the dune system itself (Rolston et al, 2005).…”

“…There were 20 replicates per cross. ASSESSMENT OF CROSS BREEDING Four Bull Island isolates were selected for cross breeding studies, two from the extremities of the sample area of Rolston et al (2005), isolates 1.E. (1) and 77.J.…”

“…Of the three species of EPN found in Ireland (Griffin et al, 1991), Steinernema feltiae and Heterorhabditis downesi co-exist on Bull Island, Dublin Bay, Ireland, although EPN distribution throughout the dune system is species-dependent (Rolston et al, 2005). This study investigates the intraspecific variation among isolates of S. feltiae from Bull Island (Rolston et al, 2005) in terms of fitness, relative infectivity, outbreeding potential and fecundity.…”

“…This study investigates the intraspecific variation among isolates of S. feltiae from Bull Island (Rolston et al, 2005) in terms of fitness, relative infectivity, outbreeding potential and fecundity. As a means of establishing if there is a genetic basis for variance in the sample set, phylogenetic relationships between isolates are also assessed using EPIC-PCR of the β-tubulin gene region.…”