Limitations and gaps in global bat wing morphology trait data

Species' life-history traits have a wide variety of applications in ecological and conservation research, particularly when assessing threats. The development and growth of global species' trait databases are critical for improving trait-based analyses; however, it is vital to understand the gaps and biases in the available data. We reviewed bat wing morphology data, specifically mass, wingspan, wing area, wing loading, and aspect ratio, to identify issues with data reporting and ambiguity. Additionally, we aimed to assess taxonomic and geographic biases in trait data coverage. We found that most studies used similar field methodology, but that data reporting and quality were inconsistent/poor. Additionally, we noted several issues regarding semantic ambiguity in trait definitions, specifically around what constitutes wing area. Globally, we found that bat wing morphology trait coverage was low. Only six bat families had >= 40% trait coverage, and, of those, none consisted of more than 11 species in total. We found similar biases in trait coverage across International Union for Conservation of Nature Red List categories, with threatened species having lower coverage. Geographically, North America, Europe, and the Indomalayan regions exhibited higher overall trait coverage, while both the Afrotropical and Neotropical ecoregions showed poor trait coverage. The underlying biases and gaps in bat wing morphology data have implications for researchers conducting global trait-based assessments. Implementing imputation techniques may address missing data, but only for smaller regional subsets with substantial trait coverage. Due to generally low overall trait coverage, increasing species' representation in the database should be prioritised. We suggest adopting an Ecological Trait Standard Vocabulary to reduce semantic ambiguity in bat wing morphology traits, to improve data compilation and clarity. Additionally, we advocate that researchers adopt an Open Science approach to facilitate the growth of a bat wing morphology trait database.