4 research outputs found
Low parasitism rates in parthenogenetic bagworm moths do not support the parasitoid hypothesis for sex
No full textThe parasite hypothesis for sex is one of the many theories that have been suggested to solve the mystery of the widespread occurrence of sex despite its high short-term costs. It suggests that sexual lineages have an evolutionary advantage over parthenogens because they can frequently generate new genotypes that are temporarily less prone to coevolving parasites. In this study, we looked for further supporting evidence for the parasite hypothesis of sex in an attempt to understand the coexistence of sexual and parthenogenetic bagworm moths (Naryciinae). The bagworm moths and their parasitoids form one of the few natural host-parasite systems where sexual and parthenogenetic hosts are apparently not separated by ecological or geographical barriers. Furthermore, in support of the parasite hypothesis for sex, parthenogenetic presence is negatively correlated with parasitism rate. We specifically tested, by identifying the reproductive mode of the parasitized individuals, whether parasitoids preferentially attack the parthenogens in sites with both sexual and parthenogenetic forms, as predicted by the parasite hypothesis. We collected hosts from sites with different frequencies of parthenogenetic and sexual moths. A DNA barcoding approach was used to determine the reproductive mode of the parasitized hosts. Furthermore, we investigated whether differences in host and parasitoid phenology could provide an alternative explanation for the variation in parasitism rates between parthenogens and sexuals. Our results contradict the prediction of the parasite hypothesis because parthenogenetic bagworm moths were less parasitized than sexuals in sympatric sites. Our findings can be explained by differences in phenology between the parthenogenetic and sexual moths rather than genetic incompatibility between parthenogenetic hosts and parasitoids. The stable coexistence of sexual and parthenogenetic Naryciinae despite the many apparent costs of sex in this system remains a mystery. Our work adds to the list of studies were the assumptions of the parasite hypothesis for sex are not all met. © 2012 European Society For Evolutionary Biology
Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)
No full text1. Multiple male copulations can have detrimental effects on female fitness
due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are
short-lived and do not feed. Multiple male mating is therefore expected
to lead to sperm limitation in females. Sperm limitation and male
limitation are hypothesised as causes of the repeated evolution of
parthenogenetic reproduction in the Psychidae.
3. In this study, the effects of multiple male mating on female
reproduction are investigated in several species of Naryciinae by
allowing males multiple copulations. The results for two species,
Siederia listerella and Dahlica lichenella, are compared. The sex ratios
of 53 natural populations are examined for indications of male
limitation.
4. Previous copulations by the male increased the female's risk of
remaining unfertilised. However, contrary to expectations, those
unfertilised females were capable of successful re-mating.
5. In S. listerella, the number of previous copulations of males
negatively influenced female fitness. Females produced 30% fewer
offspring if they mated with a previously mated male. In D. lichenella,
the older the male and the lower its number of total lifetime
copulations, the higher the female's reproductive success.
6. Only a fraction of the investigated populations had a female-skewed
sex ratio, but differences in development time between males and females
could lead to reproductive asynchrony.
7. In conclusion, male mating history did not lead to strong sperm
limitation in Naryciinae as had been suggested by their life history
Investigating the origin of parthenogenesis and ploidy level in Dahlica fennicella (Lepidoptera: Psychidae)
No full textThe theories for the predominance of sexual reproduction predict that parthenogens should have no long-term evolutionary potential due to the lack of genetic recombination, despite short term advantages. Although parthenogenesis is rare among high order animals, true parthenogens can be found in various taxa. The intriguing question of the proliferation and persistence of parthenogenetic species needs investigation. An ideal species for such research is a parthenogenetic mont Dahlica fennicella that appears to be as equally successful as other coexisting sexual species. We investigated whether high ploidy level of D. fennnicella is due to hybridization between closely related sexual species. The results form flow cytometry measurements confirmed that D. fennicella is exclusively tetraploid whereas all sexual species of the genera Dahlica and Siederia are diploid. Our phylogenentic results showed the non-hybrid origin of the parthenogenetic D. fennicella in this group of Lepidoptera. Most likely, the parthenogenetic D. fennicella orginated by autopolyploidization of D. lazuri, which is one of its closely related sexual species. We suggest that the apparent evolutionary success of D. fennicella might be due to polyploidy that could mask deleterious mutuations and probide greater levels of genetic variations.peerReviewe
The costs and benefits of multiple mating in a mostly monandrous wasp
No full textFunding: NERC DTGThe taxonomically widespread nature of polyandry remains a puzzle. Much of the empirical work regarding the costs and benefits of multiple mating to females has, for obvious reasons, relied on species that are already highly polyandrous. However, this makes it difficult to separate the processes that maintain the current level of polyandry from the processes that facilitate its expression and initiated its evolution. Here we consider the costs and benefits of polyandry in Nasonia vitripennis, a species of parasitoid wasp that is “mostly monandrous” in the wild, but which evolves polyandry under laboratory culture conditions. In a series of six experiments, we show that females gain a direct fecundity and longevity benefit from mating multiply with virgin males. Conversely, mating multiply with previously mated males actually results in a fecundity cost. Sexual harassment may also represent a significant cost of reproduction. Harassment was, however, only costly during oviposition, resulting in reduced fecundity, longevity and disrupted sex allocation. Our results show that ecological changes, in our case associated with differences in the local mating structure in the laboratory can alter the costs and benefits of mating and harassment and potentially lead to shifts in mating patterns.Peer reviewe
