Japan Eco-Evo English Seminar #4

The seminar aims to initiate interactions between international and Japanese researchers and students in the field of Ecology and Evolution.
The 4th event is specially presented by three great speakers.

Elio Borghezan (Kyoto University) from 3pm -
Iki Murase (University of the Ryukyus) from 4pm
Marta Quitián (Tokyo Metropolitan University) from 5pm

on Dec. 13th(Fri). 

Please join us if you have time.
https://sites.google.com/view/jee-english-seminar

We’ll meet at L4-E1 or via zoom.

You can get the zoom link after registering from the following link. 
https://docs.google.com/forms/d/e/1FAIpQLSf67u80HNik6YePCyHYNENst5IVEc2Jq4xpkXbWwrU-y1W5HQ/viewform

*JEEES is created by Jamie M Kass (Economo Unit) and me to cultivate interactions between international and domestic researchers/students in ecology/evolution in Japan.

Totile 1. “Someone like me: Size-assortative pairing and mating in an Amazonian fish, sailfin tetra Crenuchus spilurus” by Elio Borghezan

Abstruct:
Preference for larger mates is expected to evolve, as larger individuals are typical of higher potential fitness. Large females are often more fecund and carry larger eggs (which result in higher number and better quality of offspring), whereas larger males usually have more conspicuous ornaments and are better at defending resources. However, intrasexual competition can limit the access to larger partners, especially when opportunities for mate takeover abound. Here we investigate the relationship between individual’s size and mate choice in relation to one’s own size and their respective mate’s size using the sailfin tetra, a sexually dimorphic Amazonian fish species. We show that ornaments of larger males are exponentially more conspicuous, and larger females are more fecund and carry larger eggs. Contrary to expectation, neither males nor females associated for longer with the larger of two offered potential mates. Instead, individuals of both genders chose opposite-sex individuals of similar sizes to themselves. Additionally, similar-sized pairs were more likely to spawn than couples with higher size asymmetries. Based on field observations, we propose that prudent choice should be particularly important in this system, since courtship is long (often taking several days), which offers opportunities for mate takeover. Intrasexual competition; however, cannot readily explain female choice for similar-sized males. It is suggested that such preference might be best explained by avoidance of filial cannibalism.

Title 2. “Spatio-temporal variation in life history traits of an amphidromous fish” by Iki Murase.

Abstruct:
Studying the geographic variation in temperature-dependent phenotypic patterns of organisms is important to predict their responses to environmental changes. Recently, anthropogenic climate change modifies the original geographic and seasonal variations of sea surface temperature (SST), which likely affects the temperature-dependent phenotypic patterns in aquatic organisms. The amphidromous fish ayu, Plecoglossus altivelis altivelis, is a species suitable for examining geographic variations in life history traits because this species is distributed in wide latitudinal range (from the southwestern part of Hokkaido to Kagoshima). Using otolith analyses, latitudinal clines of growth rates (mm/day) and growth period (day) in the marine stage, and the body length (mm) at upstream migration were compared between the Sea of Japan side (SJS) and Pacific Ocean side (POS) of individuals collected in 2001 (n = 231) and 2019 (n = 247). In the 2001 populations, the growth rates and growth period showed negative and positive latitudinal clines in both the SJS and POS. The fish collected in 2019 had higher growth rates and shorter growth period than those collected in 2001. Our findings demonstrate that water temperature is responsible for the observed geographic patterns in life history traits, and are consistent with the patterns likely caused by the global warming-driven microgeographic/seasonal changes of coastal SST.

Title 3. “Sayonara, bees: Impacts of invasive species on the pollination interaction network of the Ogasawara Islands” by Marta Quitián

Abstruct:
Introduction of invasive species can cause strong imbalances in ecosystem functioning, especially in sensitive oceanic islands with high endemism because the inhabitants and the interactions between them have evolved in isolation. The Ogasawara Islands of Japan is an oceanic archipelago of World Heritage status (~1,000km S of Tokyo), which in recent decades has faced increasing disturbance from invasive species including the Green anole (Anolis carolinensis) and the European honey bee (Apis mellifera). These invasive species can have strong direct and indirect effects through predation and competition on the native island pollination system which, among other pollinator groups, it originally comprised nine native bee species from social (Certainini, Xylocopini) and solitary (Lithurgini, Megachilini, Osmini) lineages. In this study, we use an ecological network approach to compare islands with different degrees of impact from invasion. We present preliminary data on how these invasive species have affected the original island pollinator community and how this has influenced pollination interaction networks in different islands.