Spatial Ecology of Entomopathogenic Nematodes with Contrasting Foraging Strategies

Laboratory studies have identified a dichotomy in foraging behavior of entomopathogenic nematodes (EPNs) but little is known about their dispersal patterns in the field. Overall goal of this dissertation research was to examine the dispersal behavior of two EPN species with contrasting foraging strategies, cruiser, <i>Heterorhabditis</i> <i>bacteriophora</i> and ambusher, <i>Steinernema</i> <i>carpocapsae</i> from nematode-infected host cadavers in soil in laboratory and field conditions which will expand our knowledge of EPN field population dynamics to fully utilize their biological control potential. Objectives of this research were to assess the rate of active lateral movement and dispersal patterns of the two EPN species from nematode-infected host cadavers in soil in the absence of hosts, in the presence of vegetation and mobile and non-mobile hosts in the greenhouse conditions and further, quantify their short-term dispersal potential in the field and finally, artificially select ambusher, <i>S</i>. <i>carpocapsae</i> for enhanced dispersal. The results revealed that the two species differed in the spatio-temporal pattern of dispersal but showed similar average population displacement (~6 cm/day) in the absence of hosts. While a majority of <i>S</i>. <i>carpocapsae</i> dispersed <3.8 cm from the source cadaver, a majority of <i>H</i>. <i>bacteriophora</i> dispersed between 7-15 cm away from the source cadaver. However, a greater percentage of <i>S</i>. <i>carpocapsae</i> (~2.5 times) travelled faster than the fastest <i>H</i>. <i>bacteriophora</i> to larger distances, 15-61 cm. These apparent ‘sprinters’ may represent an adaptive dispersal strategy by the otherwise ambush forager <i>S</i>. <i>carpocapsae</i> in the absence of hosts. Vegetation enhanced dispersal of both species but more so for <i>H</i>.<i> bacteriophora</i>. Mobile hosts enhanced dispersal of both species. <i>S</i>. <i>carpocapsae</i> showed significantly greater average displacement than <i>H</i>. <i>bacteriophora</i> in the presence of mobile and non-mobile hosts. A greater percentage of <i>S</i>. <i>carpocapsae</i> (~14.5%) than <i>H</i>. <i>bacteriophora</i> (~0.4%) IJs dispersed the farthest distance, 11.4 cm in the presence of mobile hosts, with no difference in the presence of non-mobile hosts. A considerable proportion of IJs of both species ambushed near (<3.8 cm) the source cadaver in the presence of hosts. In the field, <i>S</i>. <i>carpocapsae</i> dispersed as far as <i>H</i>. <i>bacteriophora</i> with similar average displacements (27-28 cm/day) in a potato field and adjoining grassy border over a five day period. The two habitats did not differ in the abundance of surface active and soil-dwelling arthropods. <i>S</i>. <i>carpocapsae</i> was detected in larger numbers than <i>H</i>. <i>bacteriophora</i> in pitfall traps. However, Trombidiformes (mites) were significantly correlated with percent <i>H</i>. <i>bacteriophora</i> dispersed. <i>S</i>. <i>carpocapsae</i> responded positively to selection for dispersal with enhanced dispersal rate and reduced nictation, but also low reproduction potential. Dispersal increased significantly (13-23 fold) during the first five rounds of selection and showed only a marginal increase thereafter. The sprinters of the selected lines comprised of a greater proportion of males than the ones in the foundation population. The results provide quantitative understanding of EPN dispersal and suggest artificial selection as a promising approach for enhancing <i>S</i>. <i>carpocapsae</i> dispersal, which would have implications for designing strategies for innundative application and establishing sustainable populations of these important biocontrol agents.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Entomology

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Bal, Harit Kaur

Contributors dc:contributor

• Grewal, Parwinder

• Entomology
• lateral dispersal
• ambushers
• cruisers
• <i>Steinernema</i> <i>carpocapsae</i>
• <i>Heterorhabditis</i> <i>bacteriophora</i>
• pattern of dispersal
• sprinters

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1357164528

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1357164528