Parthenogenetic Females of the Stick Insect Clitarchus hookeri Maintain Sexual Traits

Abstract

The New Zealand stick insect Clitarchus hookeri has both sexual and parthenogenetic (all-female) populations. Sexual populations exhibit a scramble competition mating system with distinctive sex roles, where females are signalers and males are searchers, which may lead to differences in the chemical and morphological traits between sexes. Evidence from a range of insect species has shown a decay of sexual traits is common in parthenogenetic lineages, especially those traits related to mate attraction and location, presumably due to their high cost. However, in some cases, sexual traits remain functional, either due to the recent evolution of the parthenogenetic lineage, low cost of maintenance, or because there might be an advantage in maintaining them. We measured morphological and chemical traits of C. hookeri to identify differences between males and females and between females from sexual and parthenogenetic populations. We also tested the ability of males to discriminate between sexual and parthenogenetic females in a laboratory bioassay. Our results show that male C. hookeri has morphological traits that facilitate mobility (smaller body with disproportionately longer legs) and mate detection (disproportionately longer antennae), and adult females release significantly higher amounts of volatile organic compounds than males when this species is sexually active, in accordance with their distinctive sex roles. Although some differences were detected between sexual and parthenogenetic females, the latter appear to maintain copulatory behaviors and chemical signaling. Males were unable to distinguish between sexual and parthenogenetic females, suggesting that there has been little decay in the sexual traits in the parthenogenetic lineage of C. hookeri.

Phylogeography of the Poecilimon ampliatus species group (Orthoptera: Tettigoniidae) in the context of the Pleistocene glacial cycles and the origin of the only thelytokous parthenogenetic phaneropterine bush-cricket

“…Apparently, reduction of auditory function could be fast, as a result of rapid specialization, as is the case with P. jablanicensis (see Chobanov and Heller 2010). In contrast, a stick insect from New Zealand, Clitarchus hookeri (White, 1846), has both sexual and asexual populations with males being rare or absent in marginal, previously glaciated areas, where parthenogenetic females yet maintain sexual traits (Nakano et al 2019). One possible explanation for this phenomenon is the recent origin of C. hookeri, less than 40 kya (Morgan-Richards et al 2019).…”

De novo transcriptome analysis for examination of the nutrition metabolic system related to the evolutionary process through which stick insects gain the ability of flight (Phasmatodea)

“…We estimate that different host plants would affect the expression profile of transcripts involved in the carbohydrate metabolic process in the insect midgut because the amount of nutrients depends on the condition and development of their host plants [ 19 , 20 ]. Although the eight stick insects have different host plants, they can also eat a wide range of plants [ 9 , 21 – 25 ].…”

Clones on the run - the genomics of a recently expanded facultative asexual species

“…In our original model (11) the sexual wave always assimilated the clonal lineages unless asexual reproduction was less costly than sex and impeded the spread of a sexual wave. Accumulation of deleterious mutations that hamper the intricate sexual mechanisms has been observed in clonal species (8, 64), and is expected because such mutations will appear neutral during asexual expansion. As we show in our new model, if the capacity for sexual reproduction is successively lost in a clone, this will prolong survival extensively of those clones that escaped during the early phase of the expansion, while younger clones will be caught up by the sexual wave while they are still sexually competent.…”