Doctoral Dissertations

Date of Award

8-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Life Sciences

Major Professor

Susan E. Riechert

Committee Members

Christine Boake, Gordon Burghardt, Arthur Echternacht, David Etnier

Abstract

I investigated the behavioral ecology of territorial aggregation by the burrowing wolf spider Geolycosa xera archboldi McCrone in a scrub ecosystem in central Florida. I studied the formation and maintenance of aggregations and the consequences of having neighboring territory holders for individual G. xera. I examined the pattern of dispersion of G. xera at the level of both the macrohabitat and microhabitat. At the level of the macrohabitat, mapped burrow dispersion patterns were tested using pattern analyses and geostatistics and found to correlate with open sand substrata. This association was confirmed in experimental field enclosure tests for burrow site choice. At the level of the microhabitat I used discriminant analysis of burrow sites and non-burrow sites to determine habitat associations and found that only the absence of ground cover predicted burrow placement. I then tested for the correlation of substratum moisture and prey with aggregations of G. xera and found that neither were significantly correlated with aggregation. There were no predictors of individual burrow placement or aggregation beyond open sandy substrata at the spatial scales examined. I examined behavioral determinants of patterns of dispersion. By staging dyadic encounters in field enclosures, I confirmed that the uniformity of burrow spacing at a fine spatial scale was due to territorial behavior. I looked for a behavioral mechanism to account for the aggregations observed. I tested for conspecific attraction in choice tests in the field in two years and found no affect of conspecifics on site choice. I then quantified natal dispersal and found that the aggregations initially form by limited dispersal from the maternal burrow. I also found that experimentally released older juveniles also exhibited limited dispersal. Thus, habitat selection by G. xera involves limited dispersal within suitable habitat patches and avoidance of territorial conspecifics. I tested for an effect of both grouping and territorial neighbors on the success of individual G. xera. I found no influence of group size (number of neighbors within 1 m) on activity and site residency in two field tests. I then examined the affect of mean group size, mean nearest-neighbor size, and mean nearest-neighbor distance on rates of weight gain in individual G. xera. Using step-wise regression, I found that only mean nearest-neighbor size had a significant (negative) affect on weight gain. I propose that this loss of weight gain is caused by territorial overlap with larger neighbors who have priority of access to prey in the area of overlap. I hypothesize that smaller spiders trade-off this loss of weight gain against a risky change of burrow site.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS