FORMATION OF POPULATION GENETIC STRUCTURE AND MAINTENANCE OF HAPLOTYPE COEXISTENCE IN OBLIGATE PARTHENOGENETIC DAPHNIA CF. PULEX IN A SMALL POND

How the population genetic structure changes during colonization in a novel habitat has been a main topic in ecology. Lakes, as semi-closed systems, have been effective model environments for studying it. However, genetic changes during early colonization remain poorly understood because early-stage populations are rarely observed. Using a paleolimnological approach with diapausing eggs, we revealed the long-term dynamics of an obligate parthenogenetic Daphnia cf. pulex population in Lake Fukami-ike, Japan. Furthermore, we examined the mechanisms underlying haplotype coexistence. Paleolimnological analyses revealed that the D. cf. pulex population established and persisted with one predominant haplotype and limited genetic diversity. In recent years, genetically distant haplotypes from a predominant one appeared but did not replace the predominant one. We tried to understand how these lineages coexist, focusing on the Storage effect. Laboratory experiments showed the recently appeared haplotype tended to produce diapausing eggs in broader environmental conditions than the predominant one. Empirically parameterized theoretical analyses suggested that different photoperiodic responses can promote coexistence via the storage effect when the growing season length fluctuates. Overall, our study suggests that an obligate parthenogenetic population can establish and persist even with limited genetic diversity, a condition generally considered to constrain adaptation in novel habitats. We also suggest that variation in diapause-induction timing may facilitate coexistence between genetically distant haplotypes.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Yurie Otake, Kyoto University (otake.y02@gmail.com)

Authors:

Masato Yamamichi, Center for Frontier Research, National Institute of Genetics  (mst.yama@gmail.com)

Hajime Ohtsuki, Tohoku University  (ohtsuki.hajime.tohoku@gmail.com)

Kazuyoshi Yamada, Waseda University  (kyamada@waseda.jp)

Yuka Hirata, University of Tokyo  (hirata.yk16@gmail.com)

Haruka Odagiri, University of Tokyo  (girigiri215@outlook.jp)

Jotaro Urabe, Tohoku University  (urabe@tohoku.ac.jp)

Takehito Yoshida, University of Tokyo  (ty@g.ecc.u-tokyo.ac.jp)