Costs associated with the evolution of selfing in North American populations of Arabidopsis lyrata?

Abstract

Selfing can evolve if the transmission advantage of selfers outweighs the negative effects of inbreeding depression. It has been hypothesised that on the long term, selfing lineages are an evolutionary dead end, in part due to genetic degradation resembling that of Muller's ratchet in asexual lineages. There is a lack of empirical evidence for costs of selfing due to genetic degradation in recently evolved selfers. We tested whether such costs are apparent in recently established selfing populations of the generally outcrossing species Arabidopsis lyrata. Specifically, we compared selfing and outcrossing populations in their growth performance, and for traits that play a putative role in defence against herbivores. In line with our expectations, selfing populations had reduced germination rates, growth however was similar to outcrossing populations. Plants from selfing popu lations showed no consistent reduction in herbivore defence traits, and were equally palatable to caterpillars of the moth Mamestra brassicae. There were also no differences between outcrossers and selfers in phenotypic plasticity for putative defence traits and palatability after induction by herbivores. Overall, we interpret our results as showing some evidence for persistent costs of selfing due to drift or inbreeding load in terms of reduced seedling establishment, but providing no support for the hypothesis that selfing populations should be more susceptible to generalist herbivores, or rely more on induced defence.

Benefits and costs of aphid phenological bet-hedging strategies

“…During the doctoral thesis I asked whether aphids can use the novel temperature-day length combinations efficiently. I demonstrated that aphids suffer fitness constraints under short days, so the evolution of phenology might be constrained (Joschinski et al 2015a). Further research revealed that aphids are day-active (Joschinski et al 2016), which explains the fitness constraints of short days by a limited time budget.…”

“…Temperatures will rise by at least 1.5 °C in the course of the next 100 years, and possibly even more important, extreme events will become more frequent (IPCC 2014). To some extent species can tolerate such change, but change beyond tolerable limits leads to species extinctions (Urban 2015).…”

“…Phenotypic plasticity relies on the prediction of future conditions, for example day length changes in autumn predict the occurrence of frost in winter. Because climate variability alters the covariance structure of environmental parameters (Jackson et al 2009), cues that used to predict environmental hazards become less reliable. Thus, other strategies are needed.…”

“…A.pisum is an emerging model organism in ecology (Huang and Qiao 2014) and developmental biology (Brisson and Stern 2006). It is relatively large, the genome has been sequenced and annotated (The International Aphid Genomics Consortium 2010), and the polyphenism has been studied in detail (e.g., Le Trionnaire et al 2008, Le Trionnaire et al 2013.…”

“…Further research revealed that aphids are day-active (Joschinski et al 2016), which explains the fitness constraints of short days by a limited time budget. Apart from this focus on behavioral ecology and physiology, I also received training in evolutionary biology (Joschinski et al 2015b). Expected results and impact I expect that the experiment outlined in this proposal will be the first to demonstrate a longterm fitness advantage of bet-hedging in insects.…”