Larger is not better: No mate preference by European Common Frog (Rana temporaria) males

According to classical sexual selection theory, females are the choosy sex in most species. Choosiness is defined as the individual effort to invest energy and time to assess potential mates. In explosive breeding anurans, high intrasexual competition between males leads to a sexual coercion ruled mating system, where males could have evolved preferences for specific female traits. In the current study, we tested male mating preference in the explosive breeding European Common Frog without intrasexual competition. We hypothesized that males show preferences towards larger female body size in the absence of male competition. We conducted mate choice experiments, placing a male and two differently sized females in a box and recorded their mating behavior. Males did not show any preference considering female body size, neither in the attempt to grab a female nor during the formation of pairs. We witnessed a high failure rate of male mating attempts, which might make the evolution of mate choice too costly. However, small males are faster in attempting females, which could be an alternative strategy to get access to females, because their larger competitors have an advantage during scramble competition. Nonetheless, in successfully formed pairs, the females were on average larger than the males, an observation which deviated from our null-model where pairs should be of similar size if mating would be random. This indicates that selection takes place, independent from male mating preference or scramble competition.

Investigating in vitro mating preference between or within the two forms of Pyrenophora teres and its hybrids

Net blotch diseases result in significant yield losses to barley industries worldwide. They occur as net-form and spot-form net blotch caused by P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), respectively. Hybridisation between the forms was proposed to be rare, but recent identifications of field hybrids has renewed interest in the frequency and mechanisms underlying hybridisation. This study investigates the mating preference of Ptt, Ptm and laboratory-produced hybrids in vitro, using 24 different isolates and four different experimental setups. Two crosses in our study produced ascospores during two intervals separated by a 32-35 day period of no ascospore production. For these crosses Ptt isolates mated with isolates of the same form during the early ascospore production interval and produced hybrids during the later interval. Ptm isolates did not mate with isolates of the same form, instead hybridised with Ptt isolates. Analyses based on DArTseq™ markers confirmed that laboratory-produced hybrids, when given the choice to mate with both Ptt and Ptm, mated with Ptt isolates. These results unravel a novel concept that Ptt seems to have a greater reproduction robustness than Ptm, which could lead to increased prevalence of hybrid incidences in vivo.