Work

Towards Biodiversity Indicators from Opportunistic Records: Standardizing Sampling Effort and Accounting for Observer Behavior in French Coleoptera

Year: 2026

Type: article

Abstract: Opportunistic citizen-science records provide unprecedented volumes of biodiversity data, but uneven sampling effort and observer behavior complicate comparative inference. We evaluated a simple standardization framework based on fixed sampling depth, repeated resampling, observer profiling and limits on individual contributor influence, using iNaturalist Coleoptera records from France. S200, defined here as the mean number of distinct species represented in repeated standardized samples of 200 eligible observations, strongly reduced dependence on record volume (Pearson r = 0.847 for raw richness versus 0.206 after final standardization) while recovering expected geographical gradients. Incidence-based turnover (Simpson dissimilarity, βsim) was more sensitive to standardization: raw and final matrices remained correlated (r = 0.699), but pairwise relationships were appreciably reshaped. By contrast, regional structure based on relative recording frequencies (Bray–Curtis) was already pronounced in unstandardized data and increased only moderately after standardization (ANOSIM R = 0.714 to 0.777). Spatial patterns were broadly consistent across contrasting observer profiles and replicated in an independent French photographic dataset (cross-platform r = 0.701 for S200 and 0.851 for βsim).These results show that different biodiversity dimensions respond differently to opportunistic sampling: standardized observed richness requires strong standardization, incidence-based turnover remains sensitive to sample construction, whereas broad quantitative compositional structure can be comparatively robust. These metrics characterize the component of beetle diversity observable and identifiable under the specified sampling rules; they should not be interpreted as estimates of true departmental species richness.

Source: Diversity

DOI: 10.3390/d18110651

Author: Julien Touroult