ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology during our centenary year, but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Glenna Clifton is an author on ‘ The bumpy road ahead: the role of substrate roughness on animal walking and a proposed comparative metric’, published in JEB. Glenna conducted part of the work on this Review article while a postdoctoral fellow in Nicholas Gravish's lab at La Jolla, USA. She is now Assistant Professor in Biology at the University of Portland, USA, investigating animal locomotion within the context of environmental and behavioural variability.

Glenna Clifton

Describe your scientific journey and your current research focus

I started my academic path as a double major in physics and dance at Barnard College. My experience as a professionally trained ballet dancer helped me understand motion from a visceral, in addition to a mathematical, perspective. Inspired by this integration of my passions, and with a deep fascination for animal diversity, I pursued a PhD in organismic and evolutionary biology at Harvard University in the lab of Andrew Biewener. I studied the anatomical patterns and paddling motions of foot-based swimming birds, including grebes and loons. After graduating in 2017, I completed a postdoctoral fellowship in mechanical and aerospace engineering at the University of California, San Diego (UCSD) in the lab of Nicholas Gravish. At UCSD, I combined field experiments with deep learning based tracking of large video datasets to understand how ants and cockroaches adjust walking to negotiate uneven terrain. Currently as an Assistant Professor at the University of Portland, my research aims to understand how an animal's anatomy relates to its locomotion under variable, naturalistic conditions. With current projects that span diverse clades, from crustaceans to insects to birds, work in my lab strives to analyze locomotion biomechanics under conditions that relate to an animal's ecology and evolution, while also inspiring field-capable robotics.

How would you explain the main message of your Review to a member of the public, and how would you explain the broader impact of research in this area?

From wind-swept sand dunes to mossy forest floors, natural environments are anything but flat. This bumpiness undoubtedly affects walking animals, and recent research in biomechanics is focusing on understanding walking on non-flat, ‘rough’ substrates. Our Review summarizes current knowledge of walking on rough ground, but importantly propounds that the influence of substrate roughness depends not on its absolute dimensions, but instead on its size relative to an animal: a mountain to an ant may be imperceptible to an elephant. We propose a new metric to be applied when studying legged movement over rough terrain, the roughness ratio. Then, we use this metric to classify substrate roughness into three regimes: roughness that influences how well a foot grasps or adheres to a surface, roughness that influences foot placement and body positioning and roughness that induces path planning. By delineating substrate roughness into these regimes, we hope to offer common terminology and a conceptual framework to facilitate comparisons among walking conditions and species.

An Argentine ant (Linepithema humile) walking over a 3D-printed rough substrate.

An Argentine ant (Linepithema humile) walking over a 3D-printed rough substrate.

What was your approach in organising background material and shaping this Review?

The review was partially inspired by the peer reviews of a previous paper. One reviewer questioned our use of the term ‘roughness’ and asked about the novelty of studying walking on non-flat ground. For our response, I compiled a table listing every paper that observed invertebrates walking across gaps, up steps and over bumps. There are 50, with fewer than 10 focusing on quantified, continuously rough ground. Our response also involved a deep investigation into the terminology and quantification of non-flat ground across diverse fields, revealing numerous roughness metrics with no consensus. While these findings weren't relevant for inclusion in our revised manuscript, we were persuaded that the field of biomechanics lacked a formal discussion of this complexity and needed a conceptual framework that would help guide and advance research on locomotion over rough ground.

What do you see as the main value of Review-type articles?

Reviews are critical for scientific advancement. While research articles may present and contextualize new findings, review articles may synthesize broad findings, identify key areas for future investigation, and shift the framework within which we understand new findings. In other words, if new findings are seen as the result of ‘standing on the shoulders of giants’, then review articles may provide a field guide, direct one's gaze, or provide a pair of light-filtering glasses.

What changes do you think could improve the lives of early-career researchers?

I think ECRs would benefit from a greater discussion of and support for the diversity in potential academic pathways. ECRs are often prepared for a future career at an R1 [university with very high research activity], when, in reality, there are many academic career options, from community colleges to teaching-focused universities to research institutes. I work at a primarily undergraduate institution (PUI), and while I am deeply passionate about research and scientific progress, my contributions differ from those at an R1. I think broader discussion, acceptance and support for these multiple pathways in academic research could help improve the lives of ECRs. Several funding agencies offer specific grant solicitations for research at PUIs, and I think journals (and the broader scientific community) could further aid researchers at non-R1 institutes by promoting the acceptance of shorter articles. Often short-format articles focus on especially impactful findings. But research at non-R1 institutes may result in smaller, while still important, contributions. Increased opportunity for publishing these bite-sized findings would not only support researchers at diverse institutions but would also support all ECRs as they are transitioning to an independent position and setting up a lab.

Glenna Clifton's contact details: 5000 N Willamette Blvd, Portland, OR 97203, USA.

E-mail: [email protected]

The bumpy road ahead: the role of substrate roughness on animal walking and a proposed comparative metric
J. Exp. Biol.