Genetic diversity and genotypic differentiation between the sexes in swarm aggregations decrease inbreeding in the Formosan subterranean termite

Abstract

The life of a colony of subterranean termites, such as Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), has natural inbreeding and outbreeding cycles. Reproductives of mature colonies can be replaced by their offspring, which increases the degree of inbreeding in each generation. High degrees of inbreeding may lead to inbreeding depression. In this study we focused on mechanisms for inbreeding avoidance during swarming that do not require kin recognition. We investigated genetic differentiation between swarm aggregations (isolation by distance), genetic diversity within swarm aggregations (multiple colony origin) and genetic differentiation between sexes. Alates were collected from fi ve swarm aggregations in New Orleans, La. The genetic make-up of each swarm aggregation was then described by microsatellite genotyping. Alates from the different swarm aggregations were genetically differentiated; however, no isolation by distance up to at least 1000 m was detected. The dispersal distance of alates was suffi cient to guarantee mixing of an average of 13 colonies within swarm aggregations. On average, eleven percent of all possible pairs of alates in each swarm aggregation were putative full siblings. Genotypic frequencies differed signifi cantly between males and females. This could not be explained by sex-biased dispersal. We hypothesize sex-biased investment at the colony level to account for this difference. Genetic differentiation between the sexes and dispersal distances suffi cient to promote high genetic diversity within swarm aggregations each facilitate inbreeding avoidance. These observations are consistent with the results of previous studies demonstrating that the majority of simple family colonies in Louisiana populations are headed by unrelated and outbred pairs of reproductives.

Genetic diversity and colony breeding structure in native and introduced ranges of the Formosan subterranean termite, Coptotermes formosanus

“…Geographical separation of the colonies of the two subpopulations of Maui does not exceed swarming distance (Messenger and Mullins 2005;Husseneder et al 2006;Simms and Husseneder 2009), yet there is little admixture of the colonies. Apparently, interbreeding of Maui colonies is a rare event, as supported by the fact that all simple families in both subpopulations are headed by nestmate pairs, i.e., alates or neotenic pairs from the same colony.…”

Size and heterozygosity influence partner selection in the Formosan subterranean termite

“…Individuals were scored at the same 8 microsatellite loci previously used to describe the genetic structure of colonies and alate samples of Formosan subterranean termites in New Orleans (Husseneder et al 2005, 2006). A detailed description of the conditions for polymerase chain reaction and genotype scoring procedures can be found in Vargo and Henderson (2000).…”

Alate Trap-Based Assessment of Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Dispersal Flight Phenology Associated With an Urbanized Barrier Island Ecosystem

“…During dispersal ßight periods, the maximum distances traveled by C. formosanus alates are typically shorter that 1 km (Messenger and Mullins 2005, Husseneder et al 2006, Lax and Wiltz 2009. Thus, natural range expansion of C. formosanus would presumably proceed at a relatively slow pace if unassisted by humans.…”