Phylogenetic relationships of entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) inferred from partial 18S rRNA gene sequences.

Aligned 265-bp sequences of partial 18S rRNA gene were used to infer phylogenetic relationships among entomopathogenic nematodes by using maximum parsimony and likelihood methods. Phylogenetic analyses support Heterorhabditidae and Steinernematidae belonging to different monophylies. There was more sequence divergence in Steinernema species than in Heterorhabditis species. These results are congruent with the phylogenies based on morphological, life cycle, and distributional evidence. Examination of all trees within 1% of the length of the most parsimonious trees and bootstrap analyses support most relationships among Steinernema species but the relationships among Heterorhabditis species were not supported. We suggest that the partial 18S rRNA gene sequences may be too conserved for phylogenetic inference among Heterorhabditis species, but are well suited for phylogenetic inference within and among closely related families and genera of entomopathogenic nematodes and for inferring phylogenetic relationships among Steinernema species.

Effects of nitrogen and Douglas-fir allelochemicals on development of the gypsy moth,Lymantria dispar.

Two experiments were conducted to examine the influence of foliar nitrogen, terpenes, and phenolics of Douglas-fir on the development of gypsy moth larvae. In the first experiment, foliar concentrations of nitrogen and allelochemicals were manipulated by fertilizing 3-year-old potted seedlings with 0 or 200 ppm nitrogen. Concentrations of foliar nitrogen (0.33-2.38%) were negatively correlated with the phenolics (15.8-24.4 mg/g). Sixth-instar larvae previously reared on current-year Douglas-fir needles were allowed to feed on these seedlings. Pupal weights (312.8-995.6 mg) were positively correlated with levels of foliar nitrogen, negatively correlated with amounts of foliar phenolics, and uncorrelated with terpene concentrations. In the second experiment, terpene and phenolic extracts from Douglas-fir foliage were incorporated at natural levels into artificial diets with high and low levels of protein nitrogen. Neonate larvae grew faster and were larger on the high nitrogen control diet (4.1-4.5%), however, fourth instars performed better on the control diet with low nitrogen levels (2.5-2.7%). Foliar terpenes incorporated into diet had little effect on neonate fitness, but may induce subtle physiological changes in later instar larvae. Phenolics, alone or in combination with terpenes, excessively suppressed growth and survival, with no individuals living through the fourth instar, regardless of the nitrogen level. Incorporating foliar phenolic extracts into artificial diet caused unnatural levels of toxicity and failed to clarify the effects of Douglas-fir phenolics on gypsy moth fitness. Foliar nitrogen is a key factor influencing gypsy moth development on Douglas fir, but may be mitigated to some degree by phenolics.

White alder and Douglas-fir foliage quality and interegg-mass influences on larval development of gypsy moth,Lymantria dispar.

Individual families of gypsy moth collected from a single population exhibited different degrees of fitness when fed diets of white alder, a suitable broadleaf host, and Douglas-fir, an unsuitable conifer host. Members of families on diets of Douglas-fir had significantly lower survival, longer larval periods, lower pupal weights, and shorter pupal periods than members of the same families fed alder. Foliar nutritional quality, including nitrogen level and allelochemical composition (terpenes and phenols), was considered the key factor responsible for these differences. Growth parameters differed significantly for families within diet treatments, indicating that the genetic resources of a family did affect performance somewhat. The influence of a family's genetic resources on larval survival was most notable when larvae were under the greatest nutritional stress.