Department of Environmental Life Sciences
Division of Ecology and Evolutionary Biology

Plant Ecology 分野

Satoki Sakai
キャンパス Aobayama キャンパス
専攻分野 Laboratory of Functional Ecology
連絡先 022-795-6697

I specialize in the evolutionary ecology of plants. Our purpose is to investigate the ultimate cause as to why the ecological characteristics of plants evolved. We engage in theoretical analysis using mathematical models and the empirical research thereof.
Outside of the lab, I enjoy soccer. I am a big fan of Vegalta Sendai and the Japan national team.


Graduated, Faculty of Science, Kyoto University
Completed botany doctoral program (Doctor of Science), Graduate School of Science, University of Tokyo
Achieved current position after serving as a Researcher; Grassland Laboratory, Ministry of Agriculture, Forestry and Fisheries


See the following.


Ecological Society of Japan
Ecological Society of America
Society for the Study of Evolution
Botanical Society of America


Plant Evolutionary Ecology (5th semester)


We are engaged in analysis using mathematical models and the verification thereof, concerning tradeoffs between seed size and number as well as optimum seed size The problem of how many seeds to create and of what size by using a fixed amount of resources is one that contributes significantly to life cycle strategies in plants. The bigger a seed that is made, the higher the germination rate needs to be of each individual seed. However, the number of seeds that can be produced decreases. Conversely, the smaller the seed that is created, the lower the individual germination rate, but the number of seeds that can be produced increases. So, what are the optimum size and number? Until now, research concerning this problem has hypothesized a tradeoff relationship in which seed size equals the amount of resources invested in seed production divided by the number of seeds. Essentially, the hypothesis is the size and number of seeds are an inverse proportion. The total amount of seed substance (seed size multiplied by seed number) does not change regardless of the number of seeds. However, we have shown theoretically that this inverse proportion tradeoff relationship is not feasible (Sakai and Harada 2001, Evolution 55: 467-476; American Naturalist 157: 348-359). We predict that even if you decrease the number of seeds, the seed size does not increase to the extent of a true inverse proportion (figure). The total amount of seed substance decreases the more you decrease the number of seeds. This occurs because resources decrease in value during seed production due to maintenance respiration (see our papers for details). Under Sakai and Harada’s tradeoff, sacrificing seed size to increase the number of seeds is advantageous, and, as such, optimum seed size is smaller than optimum seed size under the inverse proportion tradeoff. These predictions are backed by testing using Cardiocrinum cordatum (Sakai and Sakai 2005, Oikos 108:105-114).


The ecological characteristics of plants are truly diverse. For example, flower color and shape differ greatly between species, groups, and individuals. Seed size can range from big like the coconut to being like dust as are those of orchids. Our laboratory is attempting to understand why this diversity of ecological characteristics evolved. We are attempting to discover the reasons why these characteristics evolved from the perspective that having such characteristics was advantageous for survival and reproduction. Our research methods are centered on field research and theoretical analysis. Each student sets research themes and engages in research based on their own individual interests. Those who see the diversity of plants and are struck by the wonder of this, those who wish to understand why such diversity has evolved; why not research plant evolutionary ecology with us?