Fundamental research questions in subterranean biology

Abstract

Five decades ago, a landmark paper in Science titled The Cave Environment heralded caves as ideal natural experimental laboratories in which to develop and address general questions in geology, ecology, biogeography, and evolutionary biology. Although the ‘caves as laboratory’ paradigm has since been advocated by subterranean biologists, there are few examples of studies that successfully translated their results into general principles. The contemporary era of big data, modelling tools, and revolutionary advances in genetics and (meta)genomics provides an opportunity to revisit unresolved questions and challenges, as well as examine promising new avenues of research in subterranean biology. Accordingly, we have developed a roadmap to guide future research endeavours in subterranean biology by adapting a well‐established methodology of ‘horizon scanning’ to identify the highest priority research questions across six subject areas. Based on the expert opinion of 30 scientists from around the globe with complementary expertise and of different academic ages, we assembled an initial list of 258 fundamental questions concentrating on macroecology and microbial ecology, adaptation, evolution, and conservation. Subsequently, through online surveys, 130 subterranean biologists with various backgrounds assisted us in reducing our list to 50 top‐priority questions. These research questions are broad in scope and ready to be addressed in the next decade. We believe this exercise will stimulate research towards a deeper understanding of subterranean biology and foster hypothesis‐driven studies likely to resonate broadly from the traditional boundaries of this field.

Evidence for speciation underground in diving beetles (Dytiscidae) from a subterranean archipelago

“…A fundamental question in subterranean biology is whether the current patterns of subterranean biodiversity are best explained by a “history of colonization of surface ancestors or by in situ speciation and dispersal in subterranean habitats” (Mammola et al. 2020). The CRH and ASH are the generally accepted scenarios for the evolution of cave species in major animal groups—insects, arachnids, and vertebrates (Holsinger 1988, 2000; Peck and Finston 1993; Leys et al.…”

Let research on subterranean habitats resonate!

“…As reason prevailed upon mythology, caves became the arena for debating scientific ideas and ultimately good model systems for understanding the outside world (Poulson and White 1969). Yet, while we typically insist that our research is exciting, adventurous, and important to answer cutting-edge questions (Juan et al 2010;Sánchez-Fernández et al 2018;Mammola 2019;Mammola et al 2019Mammola et al , 2020, this potential is often lost when the results are translated into scientific publications. Too often, the generality of our results remains unexpressed insofar as cave research is written by cave scientists for cave scientists.…”

“…Encouraged by the inherent peculiarities of caves, we might have forgotten the importance of trying to address broad questions with our research, favouring the isolation of our research community and increasing our intellectual inbreeding. We believe that being aware of this potential is a fundamental step to frame broad-in-scope subterranean research (Mammola et al 2020), regardless of the journal in which it will end-up published. Inspired by the writer and philosopher Umberto Eco (1997), we propose a few bullet-point ideas for improving the generality of the literature on subterranean habitats, including both tips for framing broad-scoped research and for writing texts accessible to a general audience (Box 1).…”

“…1. Try to identify general questions that are scalable to other systems (Mammola et al 2020). Greeks brought philosophy into caves: we can also introduce our field into them.…”

Cave-adapted beetles from continental Portugal

“…Cave fauna has relatively low specific richness, but high conservation value for the global biodiversity of our planet (Mammola et al 2019). Subterranean species have unique traits that emerged as a result of isolation and convengent adaptation towards the underground life (Mammola et al 2020).…”