Yumi Nakadera

Research Interests

One of my research interests is sexual selection in simultaneously hermaphroditic animals. Historically, researches have believed that hermaphrodites are not exposed to sexual selection. In contrast, many of them show bizarre reproductive life-history traits (e.g., time-consuming mating, biting off a partner’s penis, love-dart shooting). The evolution of these traits are likely explained by sexual selection, but empirical studies proving this are still required.
In my PhD project, I mainly focus on sperm competition of the great pond snail, Lymnaea stagnalis. My aim is to (1) find “sexy males” in wild populations and (2) investigate how they succeed. In addition, I am interested in their sex allocation depending on internal conditions or external environmental factors.

Selected Publications

Y. NAKADERA, C. SUTCHARIT, T. UBUKATA, K. SEKI, H. UTSUNO, S. PANHA and T. ASAMI (2010). Enantiomorphs differ in shape in opposite directions between populations. Journal of Evolutionary Biology23:2377-2384.

Research project

Evaluating sexual selection and sperm competition in wild snail populations of Lymnaea stagnalis 

Sexual encounters are usually accompanied by conflicts of interest between the mating partners. In animals with separate sexes such sexual conflicts can play a crucial role in the evolution of reproductive systems, and can even lead to speciation. Conflict arises when male strategies evolve that enhance the chances of fertilization, but at the same time reduce the reproductive potential of the female partner. That such conflicts also occur in simultaneous hermaphrodites may seem less obvious. After all, simultaneous hermaphrodites are male and female at the same time and especially for that reason potential conflicts have long been overlooked. However, recent research has revealed that sexual conflicts can occur and may even take more extreme forms that in species with separate sexes. Upon copulation, the hermaphroditic pond snail Lymnaea stagnalis transfers, next to sperm, seminal fluid components that influence the partner's egg laying. Recent experimental work has established that this may form the basis for a sexual conflict in this simultaneous hermaphrodite. However, it is unknown whether these observations can be extrapolated to sperm competition and sexual conflict in the wild. In my PhD project, I will examine whether sperm competitiveness varies in wild L. stagnalis populations, and whether this sperm competitiveness has a genetic basis. I expect that my results will contribute significantly to our understanding of reproductive interests of sperm donors and recipients, as well as sexual selection in hermaphroditic animals in general.

Participants:Dr. Joris M Koene, Prof. Dr. Nico van Straalen