2024 HARPER PRIZE SHORTLIST: For the next two weeks, we are featuring the articles shortlisted for the 2024 Harper Prize. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology. Daiki Takahashi’s ‘Deer grazing drove an assemblage-level evolution of plant dwarfism in an insular system’ is one of those shortlisted for the award.

About the paper:

• What is your shortlisted paper about, and what are you seeking to answer with your research? 

We tested whether assemblage-level plant dwarfism is influenced by herbivore grazing. Focusing on a UNESCO-listed island with over 100 dwarf plant taxa at high altitudes, we conducted a meta-analysis of 40 taxa pairs, assessing climate, nutrients, and grazing pressure. Our results suggest that grazing, rather than climate or nutrients, significantly shaped plant size variation. This implies that herbivore grazing has potentially driven the assemblage-level evolution of plant dwarfism.

Fieldwork in the high altitude area of Yakushima Island, Japan (photo: Kana Magota).

• Were you surprised by anything when working on it? Did you have any challenges to overcome?

Since we applied a meta-analysis approach, we needed to collect samples from as many taxa as possible, both from the island and the mainland. This required extensive fieldwork, including monthly climbs up to 2,000 meters to gather reproductive samples. In total, we measured over 4,000 samples. The sheer scale of sampling was a challenge, but it enabled more robust inferences across species. Additionally, due to COVID-19, I conducted most of the fieldwork alone, making data collection even more demanding.

A dwarf plant, Solidago minutissima at Yakushima Island, (photo: Daiki Takahashi)

• What is the next step in this field going to be? 

The next step is to reveal why such large-scale dwarfism can occur in the island. This is challenging, but by focusing on other islands which exhibit historically high density of deer and especially on the genomic bases of plant dwarfism.

A dwarf plant, Angelica longiradiata var. yakushimensis at Yakushima Island (photo: Daiki Takahashi).

• What are the broader impacts or implications of your research for policy or practice? 

Our research highlights the crucial balance between animals and plants. Globally, the rapid increase in herbivores, especially deer, has significantly impacted plant communities, but dwarf plant assemblages like our field were not observed as long as we know. This implies that a moderate herbivore population may support coexistence with diverse plant species, and emphasises the need for sustainable wildlife management and conservation policies.

About the author:

Daiki Takahashi in the high altitude area of Yakushima Island (photo: Kana Magota).

• How did you get involved in ecology? 

As a child, my parents often took me to natural parks, forests and oceans, sparking my early interest in biodiversity. This fascination grew over time, and during university, several lectures by ecologists deepened my understanding of ecology. I became especially interested in uncovering the mechanisms and patterns that shape biodiversity, leading me to pursue ecological research.

• What is your current position?

Assistant professor (tenure track) in Kyushu University, Japan.

• Have you continued the research your paper is about?

Yes, I have continued this research, focusing on plant evolution under herbivore pressure. One of my next targets is studying areas where deer populations have been protected and have grown in high density for over 1,000 years due to religious reasons in Japan. This unique setting provides an opportunity to further explore the long-term evolutionary impacts of herbivory on plant communities and assess how prolonged grazing pressure shapes plant traits and biodiversity.

A dwarf plant, Astilbe glaberrima var. saxatilis at Yakushima Island (photo: Daiki Takahashi).

• What one piece of advice would you give to someone in your field? 

I believe two key aspects are essential in ecological studies. First, careful and prolonged field observation is crucial, as the complexity and diversity of wildlife cannot be fully understood through short-term studies or data alone. Second, testing a hypothesis requires a sufficient sample size, both in the number of individuals and species, to ensure robust inferences. More samples and greater effort lead to stronger, more reliable conclusions, ultimately enhancing the accuracy and impact of ecological research.

Find the other early career researchers and their articles that have been shortlisted for the 2024 Harper Prize here!