Consequences of mating with siblings and nonsiblings on the reproductive success in a leaf beetle

Abstract

Choosing a suitable mating partner is crucial for the fitness of an individual, whereby mating with siblings often results in inbreeding depression. We studied consequences of mating with siblings versus nonsiblings in the mustard leaf beetle, Phaedon cochleariae (Coleoptera: Chrysomelidae), on lifetime reproductive traits. Furthermore, we analyzed whether cuticular hydrocarbon (CHC) profiles are family specific and could potentially influence the mating behavior of young adults. We hypothesized a reduced reproductive success of females mated with siblings and a more rapid mating of males with nonsiblings. The hatching rate from eggs of sibling pairs was lower compared to that of nonsibling pairs, pointing to inbreeding depression. Furthermore, the number of eggs laid by females decreased over time in both sibling and nonsibling pairs. Interestingly, the CHC profiles and the body mass differed between families. However, the beetles did not avoid siblings and accepted them as readily as nonsiblings for mating in no‐choice tests. In summary, although it had negative consequences to mate a sibling and although siblings could potentially be recognized by their CHC profiles, the beetles did not show a delayed mating with siblings. Our results indicate that P. cochleariae beetles have not developed a precopulatory mechanism to avoid inbreeding, at least under the test conditions applied here. We predict that instead a polyandrous mating system and/or postcopulatory mechanisms might have evolved in this species by which inbreeding costs can be reduced.

Lifetime inbreeding depression in a leaf beetle

“…The present study revealed that mustard leaf beetles suffer from strong inbreeding depression throughout their ontogeny. Inbreeding does not only reduce the larval hatching rate of the beetle as detected in a previous study (Müller & Müller, ), but also crucially increases the mortality of larvae prior adult emergence and of young adults. Moreover, the reproductive output of inbred females was reduced compared to outbred females, although their body mass was not decreased by inbreeding.…”

“…In a previous study on P. cochleariae , we disclosed that the larval hatching rate of inbred offspring is decreased in comparison with outbred offspring (Müller & Müller, ). Thus, this beetle species suffers from inbreeding depression and we consequently expected negative inbreeding effects on other fitness‐related traits throughout its ontogeny.…”

“…Inbreeding depression arises from an increase in genome‐wide homozygosity in the offspring generation, which results in the increased phenotypic expression of recessive deleterious mutations and the reduced expression of heterozygote advantage (Charlesworth & Willis, ; Keller & Waller, ). Inbreeding depression can become evident in the offspring of only one generation inbreeding (Müller & Müller, ) or after several generations inbreeding (Bilde, Maklakov, & Schilling, ). Moreover, inbreeding can also influence traits not closely linked to fitness, such as the chemical (Menzel, Radke, & Foitzik, ) or behavioral phenotype of insects (Müller & Juškauskas, ; Pilakouta & Smiseth, ; Richardson & Smiseth, ).…”

“…Thus, this beetle species suffers from inbreeding depression and we consequently expected negative inbreeding effects on other fitness‐related traits throughout its ontogeny. Moreover, the CHC profile, which is decisive for mate choice in P. cochleariae (Geiselhardt, Otte, & Hilker, ) and other insect species (Howard & Blomquist, ), differs between families (Müller & Müller, ). Although CHCs can function as mechanism to discriminate between closely related and unrelated individuals (Weddle, Hunt, & Sakaluk, ), the family‐specific CHC patterns in P. cochleariae do not mediate precopulatory inbreeding avoidance by a faster mating of nonsiblings compared to siblings (Müller & Müller, ).…”

Producing offspring in Armadillidium vulgare: Effects of genetic diversity and inbreeding

“…Likewise, better survival has been reported in heterozygous individuals in birds (Velando, Barros, & Moran, ) and annelids (McElroy, Presley, & Diehl, ). Inbred crosses often result in a decrease in fertility (i.e., offspring number), as observed in arthropods (Lihoreau, Zimmer, & Rivault, ; Müller & Müller, ), and as a result offspring production is one of the life history traits that has received the most attention in the literature. It is likely that the homozygous state of loci with deleterious recessive alleles leads to a decrease in inbred offspring fitness (Charlesworth & Willis, ).…”