Describing relatedness patterns in bess beetles

Delayed dispersal occurs in many different taxa and has major implications for the evolution of sociality. It may be favored either through advantages to the delayer's fitness (direct benefits) or through the fitness of siblings or parents (indirect benefits). Despite evidence for both of these, we know very little about how the two types combine to favor delaying dispersal. My long-term goal is to understand the relationship between the direct and indirect benefits of delayed dispersal in the wood-feeding Horned Passalus beetle (Odontotaenius disjunctus). To assess the potential for inclusive fitness benefits in O. disjunctus, I will integrate direct behavioral observations using plexiglass-walled "observation logs" with indirect evidence regarding relatedness among individuals collected from the field. Relatedness will be measured using a novel next-generation sequencing technique, Illumina RAD (restriction-site associated DNA) sequencing, to assess polymorphic genetic markers. RADseq is a powerful genotyping method that will allow me to assess of relatedness with finer accuracy and provide me with the opportunity to investigate the genetic basis of dispersal. An important first step in this project will be to determine the potential benefits of delaying dispersal in this species. I propose to test several non-exclusive hypotheses regarding these benefits: H1, enhanced inclusive fitness gained through sibling cooperation (e.g. alloparental brood care or cooperative resource exploitation); H2, increased access to resources through parental food sharing; and H3, reduced dispersal costs by inheriting or "budding off" from the natal territory. In the lab, I will observe the behavior of individuals that delay dispersal to measure the frequency and nature of interactions between them and their putative parents or younger siblings. A key component of this study will be the use of genetic markers to measure relatedness, and hence the inclusive fitness potentially gained from these behaviors. I will assess predictions of the three hypotheses: H1, relatedness between apparent siblings that show cooperation will be high; H2, parents should be more willing to concede resources to offspring if they are indeed the genetic parents; H3, if offspring forego long distance dispersal in favor of colonizing independent nests in their natal log, colonies found within a single log should be more closely related when compared to colonies found in different logs. I chose to use RAD sequencing due to its power to uncover many markers in species for which no genetic information is available. This technique also may be valuable for assessing the genetics of complex behaviors like dispersal using quantitative trait loci analysis. RADseq uses restriction enzymes to select DNA fragments of appropriate size, which are then bar-coded and Illumina sequenced. These sequences are then analyzed for single nucleotide polymorphisms (SNPs) scattered around the genome. RADseq typically reveals hundreds of polymorphic markers important for estimating relatedness. I will input the SNP results into software (e.g., kinship) that calculates relatedness using probabilities of sharing alleles. The results will allow me to test if cooperative behaviors are associated with within colony relatedness (maternity, paternity, and sibling relatedness), and if between-colony relatedness indicates local dispersal.