Colony genetic structure and effects of inbreeding on body size in three populations of Reticulitermes flavipes in the southeastern U.S.

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Title: Colony genetic structure and effects of inbreeding on body size in three populations of Reticulitermes flavipes in the southeastern U.S.
Author: Nino, Bernardo Daniel
Advisors: David Tarpy, Committee Member
Coby Schal, Committee Member
Edward Vargo, Committee Chair
Abstract: In this study, I expanded the knowledge base of the eastern subterranean termite R. flavipes by investigating colony and population genetic structure in previously unstudied areas in Florida and Mississippi. I used microsatellite markers to infer colony breeding structure and population genetic structure and genotyped 20 workers in each of 20-30 colonies per population at eight microsatellite loci. I conducted pedigree analysis on the worker genotypes to determine the proportions of colonies that were simple families, extended families or mixed families. I also estimated the coefficient of relatedness and F-statistics and compared these values to those based on computer simulations of different breeding systems to infer levels of inbreeding and numbers of reproductives within colonies. An unexpected finding was the presence of two distinct populations in one collection site in Mississippi (MS). These two populations, MS1 and MS2, differed in the predominant family type. MS1 consisted mainly of simple family colonies whereas MS2 was composed primarily of extended family colonies. The breeding structure in the extended family colonies in both populations was consistent with simulations for colonies with a low number of effective reproductives (2-6) which have been interbreeding for few generations. In Florida I found a high proportion of extended family colonies (~ 63%); the breeding structure in these colonies was consistent with the presence of a higher number of effective reproductives (> 6) which had been interbreeding for many generations. Mixed family colonies were collected in all three populations and composed about 10% of all colonies in each population. In addition, I investigated possible effects of inbreeding and colony family type on worker and soldier body size. Worker and soldier head widths were measured and correlated to colony inbreeding coefficient (FIC). This statistic is highly sensitive to the number of effective reproductives heading colonies. A negative correlation was discovered between worker and soldier body size and the effective number of reproductives heading colonies in two populations. I found a similar trend in the third population (MS1) but it was not significant, most likely due to small sample size. In population MS2 I found a significant effect of colony family type on body size; workers and soldiers in extended family colonies were smaller than individuals in simple family colonies. These finding may indicate a previously little appreciated consequence of inbreeding in termites.
Date: 2009-02-16
Degree: MS
Discipline: Entomology

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