|Campbell, James - Jim|
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2003
Publication Date: 8/15/2003
Citation: CAMPBELL, J.F., LEWIS, E.E., STOCK, S.P., NADLER, S.A., KAYA, H.K. EVOLUTION OF HOST SEARCH STRATEGIES IN ENTOMOPATHOGENIC NEMATODES (NEMATODA: STEINERNMATIDAE). 2003. JOURNAL OF NEMATOLOGY. Vol. 35. p. 142-145. Interpretive Summary: Insect-parasitic nematodes are important biological control agents of many pest species. A group of insect parasitic nematodes (Steinernema species) actively search for insect hosts to infect. Within Steinernema, there is a great deal of variation among species in the way that they search for insects. This variation suggests that the nematodes use one of three different search strategies; ambush or sit and wait, cruise or active search, or an intermediate strategy. To address questions about how these different search strategies may have evolved, we mapped traits associated with each species onto a tree of the hypothesized evolutionary relationships among Steinernema species. Based on our results, we hypothesize that the ancestral Steinernema species was an intermediate forager and that ambush and cruise foraging each evolved at least once in Steinernema. This is significant because it suggests that some of the behavioral traits associated with specialized foraging strategies are derived and therefore tests to determine their adaptive value can be conducted.
Technical Abstract: There is interspecific variation in infective juvenile behavior within the entomopathogenic nematode genus Steinernema. This variation is consistent with use of different host searching (foraging) strategies along a continuum between ambush and cruise foraging. To address questions about the evolution of foraging strategy, behavioral and morphological characters swere mapped by parsimony on a phylogeny of Steinernema. Three species, all in the same clade, were classified as ambushers based on standing bout duration and host finding ability. One clade included six species that were all cruisers based on both host-finding and lack of standing behavior. Species in the ambusher clade had a high jumping rate, species in the cruiser clade had no jumping behavior, and most intermediate foragers exhibited some level of jumping. Response to volatile and contact host cues was variable even within a foraging strategy. Infective juveniles in the ambusher clade were all in the smallest size category, species in the cruiser clade were in the largest size categories, and intermediate in size. We hypothesize that the ancestral Steinernema species was an intermediate forager and that ambush and cruise foraging each evolved at lease once in the genus.