Character displacement or priority effects: immigration timing can affect community assembly with rapid evolution

Keiichi Morita, Masato Yamamichi

Proceedings of the Royal Society B: Biological Sciences (2024) 291: 20242145. DOI:10.1098/rspb.2024.214

Press release (In Japanese only)

Understanding how biological communities assemble in the presence of rapid evolution is becoming an important topic in ecology. Previous studies demonstrated that community assembly can be affected by two types of eco-evolutionary dynamics: evolution-mediated priority effect (EPE) and ecological character displacement (ECD). In EPE, early-arriving species prevent colonization of late-arriving species via local adaptation (i.e. community monopolization), whereas ECD promotes species coexistence by niche partitioning. Researchers tended to discuss the two processes separately, but it should be possible for those processes to operate in the same system depending on various conditions. Here, we developed a theoretical framework that integrates the two processes by using a simple two-species competition model with eco-evolutionary feedback. We revealed that, when an early-arriving species evolves, the difference in immigration timing between the early-arriving and a late-arriving species can be a key parameter. When the difference is small, ECD occurs because insufficient local adaptation of the early-arriving species allows colonization of the late-arriving species. When the difference is large, however, EPE occurs because niche pre-emption by local adaptation of the early-arriving species prevents colonization of the late-arriving species. Further theoretical and empirical studies will be important to better understand eco-evolutionary community assembly with ECD and EPE.

A complete classification of evolutionary games with environmental feedback

Hiromu Ito & Masato Yamamichi.

PNAS Nexus (2024). 3 (11): pgae455. DOI:10.1093/pnasnexus/pgae455

Press release (In Japanese only)

A tragedy of the commons, in which rational behavior of individuals to maximize their own payoffs depletes common resources, is one of the most important research topics in game theory. To better understand the social dilemma problem, recent studies have developed a theoretical framework of feedback-evolving game where individual behavior affects an environmental (renewable) resource and the environmental resource changes individual payoffs. While previous studies assumed that the frequency of defectors increases (prisoner’s dilemma [PD] game) when the environmental resource is abundant to investigate an oscillating tragedy of the commons, it is also possible for other types of game to produce the social dilemma. In this paper, we extend the feedback-evolving game by considering not only PD game, but also the other three game structures when the environmental resource is replete for a reasonably complete classification. The three games are Chicken game where defectors and cooperators coexist through minority advantage, Stag-Hunt (SH) game with minority disadvantage, and Trivial game where the frequency of cooperators increases. In addition, we utilize a dilemma phase plane to visually track (transient) dynamics of game structure changes. We found that an emergent initial condition dependence (i.e. bistability) is pervasive in the feedback-evolving game when the three games are involved. We also showed that persistent oscillation dynamics arise even with Chicken or SH games in replete environments. Our generalized analysis will be an important step to further extend the theoretical framework of feedback-evolving game to various game situations with environmental feedback.

Sawa Group / Multicellular Organization Laboratory

Distinct functions of three Wnt proteins control mirror-symmetric organogenesis in the C. elegans gonad

Shuhei So, Masayo Asakawa and Hitoshi Sawa

eLife (2024) Nov 1:13:e103035 DOI:10.7554/eLife.103035

Organogenesis requires the proper production of diverse cell types and their positioning/migration. However, the coordination of these processes during development remains poorly understood. The gonad in C. elegans exhibits a mirror-symmetric structure guided by the migration of distal tip cells (DTCs), which result from asymmetric divisions of somatic gonadal precursors (SGPs; Z1 and Z4). We found that the polarity of Z1 and Z4, which possess mirror-symmetric orientation, is controlled by the redundant functions of the LIN-17/Frizzled receptor and three Wnt proteins (CWN-1, CWN-2, and EGL-20) with distinct functions. In lin-17 mutants, CWN-2 promotes normal polarity in both Z1 and Z4, while CWN-1 promotes reverse and normal polarity in Z1 and Z4, respectively. In contrast, EGL-20 inhibits the polarization of both Z1 and Z4. In lin-17 egl-20 cwn-2 triple mutants with a polarity reversal of Z1, DTCs from Z1 frequently miss-migrate to the posterior side. Our further analysis demonstrates that the mis-positioning of DTCs in the gonad due to the polarity reversal of Z1 leads to mis-migration. Similar mis-migration was also observed in cki-1(RNAi) animals producing ectopic DTCs. These results highlight the role of Wnt signaling in coordinating the production and migration of DTCs to establish a mirror-symmetric organ.

Figure: Left: Development of wild type gonad in C. elegans. Z1 and Z4 cells have mirror-symmetric polarity and produces two DTCs at the distal ends of the gonad. Each DTC migrate distally. Center: In lin-17 egl-20 cwn-2 mutants, Z1 polarity is reversed, producing DTC at the center of the gonad which migrate posteriorly. Right：Images of migrating DTCs (green).

Associate professor Ken-ichi NONOMURA (Plant Cytogenetics Laboratory) was promoted to professor as of November 1, 2024. Congratulations!

> NONOMURA, Ken-ichi : Plant Cytogenetics Laboratory, Department of Gene Function and Phenomics

NONOMURA, Ken-ichi Professor