Raunkiæran shortfalls: Challenges and perspectives in trait-based ecology

Trait-based ecology, a prominent research field identifying traits linked to the distribution and interactions of organisms and their impact on ecosystem functioning, has flourished in the last three decades. Yet, the field still grapples with critical challenges, broadly framed as Raunkiæran shortfalls. Recognizing and interconnecting these limitations is vital for designing and prioritizing research objectives and mainstreaming trait-based approaches across a variety of organisms, trophic levels, and biomes. This strategic review scrutinizes eight major limitations within trait-based ecology, spanning scales from organisms to the entire biosphere. Challenges range from defining and measuring traits (SF 1), exploring intraspecific variability within and across individuals and populations (SF 2), understanding the complex relationships between trait variation and fitness (SF 3), and discerning trait variations with underlying evolutionary patterns (SF 4). This review extends to community assembly (SF 5), ecosystem functioning and multitrophic relationships (SFs 6 and 7), and global repositories and scaling (SF 8). At the core of trait-based ecology lies the ambition of scaling up processes from individuals to ecosystems by exploring the ecological strategies of organisms and connecting them to ecosystem functions across multiple trophic levels. Achieving this goal necessitates addressing key limitations embedded in the foundations of trait-based ecology. After identifying key SFs, we propose pathways for advancing trait-based ecology, fortifying its robustness, and unlocking its full potential to significantly contribute to ecological understanding and biodiversity conservation. This review underscores the significance of systematically evaluating the performance of organisms in standardized conditions, encompassing their responses to environmental variation and effects on ecosystems. This approach aims to bridge the gap between easily measurable traits, species ecological strategies, their demography, and their combined impacts on ecosystems.