Genetic data indicate that most field-collected woodroach pairs are unrelated

Extra-pair paternity in the wood-feeding cockroach Cryptocercus punctulatus Scudder: Social but not genetic monogamy

Subsocial Cryptocercus cockroaches are the sister group to termites and considered to be socially monogamous. Because genetic monogamy is a suggested requirement for evolution of cooperative breeding/eusociality, particularly in hymenopterans, clarification of the mating biology of Cryptocercus would help illuminate evolutionary trends in eusocial insects. To investigate possible extra-pair paternity in C. punctulatus, microsatellite markers were used to analyse offspring parentage, the stored sperm in females and results of experimental manipulation of sperm competition. Extra-pair paternity was common in field-collected families, but a lack of maternal alleles in several nymphs suggests sampling error or adoption. Isolating prereproductive pairs and assaying subsequently produced nymphs confirmed that nymphs lacked alleles from the pair male in 40% of families, with extra-pair male(s) siring 27%-77% of nymphs. Sperm of extra-pair males was detected in the spermatheca of 51% of paired prereproductive females. Mate switching and surgical manipulation of male mating ability indicated a tendency towards last male sperm precedence. Overall, the results demonstrate that about half of young females are serially monogamous during their maturational year, but bond, overwinter and produce their only set of offspring in company of the last mated male (=pair male). Repeated mating by the pair male increases the number of nymphs sired, but because many females use stored sperm of previous copulatory partners to fertilize eggs, pair males extend parental care to unrelated nymphs. The results suggest that genetic monogamy either developed in the termite ancestor after splitting from the Cryptocercus lineage, or that genetic monogamy may not be a strict prerequisite for the evolution of termite eusociality.

Genetic insights into family group co-occurrence in Cryptocercus punctulatus, a sub-social woodroach from the southern Appalachian Mountains

The wood-feeding cockroach Cryptocercus punctulatus Scudder (Blattodea: Cryptocercidae) is an important member of the dead wood (saproxylic) community in montane forests of the southeastern United States. However, its population biology remains poorly understood. Here, aspects of family group co-occurrence were characterized to provide basic information that can be extended by studies on the evolution and maintenance of sub-sociality. Broad sampling across the species’ range was coupled with molecular data (mitochondrial DNA (mtDNA) sequences). The primary questions were: (1) what proportion of rotting logs contain two or more different mtDNA haplotypes and how often can this be attributed to multiple families inhabiting the same log, (2) are multi-family logs spatially clustered, and (3) what levels of genetic differentiation among haplotypes exist within a log, and how genetically similar are matrilines of co-occurring family groups? Multi-family logs were identified on the premise that three different mtDNA haplotypes, or two different haplotypes among adult females, is inconsistent with a single family group founded by one male–female pair. Results showed that of the 88 rotting logs from which multiple adult C. punctulatus were sampled, 41 logs (47%) contained two or more mtDNA haplotypes, and at least 19 of these logs (22% overall) were inferred to be inhabited by multiple families. There was no strong evidence for spatial clustering of the latter class of logs. The frequency distribution of nucleotide differences between co-occurring haplotypes was strongly right-skewed, such that most haplotypes were only one or two mutations apart, but more substantial divergences (up to 18 mutations, or 1.6% uncorrected sequence divergence) do occasionally occur within logs. This work represents the first explicit investigation of family group co-occurrence in C. punctulatus, providing a valuable baseline for follow-up studies.