Gaps in North American butterfly inventory knowledge

Study assessing inventory completeness of butterflies in Canada, the US and Mexico reveals narrowing data gaps, but increasing bias

GBIF-mediated data resources used : 2,421,261 species occurrences
Speyeria atlantis
Speyeria atlantis Edwards, 1862 observed in North Cochrane District, ON, Canada by Jack Farley (CC BY-NC 4.0)

Gaps in openly-accessible biodiversity data limit attempts to address important ecological and evolutionary questions. Knowing where and when gaps occur is critical not only for choosing scales for analyses, but also for prioritizing efforts to fill such gaps.

In this study, researchers assessed the inventory completeness of North American butterflies, i.e., how many species have been recorded versus how many species would be expected. With range maps derived from field guides as a baseline for expected richness, the author used species occurrences from GBIF, iDigBio and eButterfly as the comparison for recorded richness.

Overall, more than 90 per cent of occurrences fell within delineations from range maps. Inventory completeness was spatially heterogeneous, with noticeable gaps in the far north of Canada, midwestern United States and northern Mexico. A comparison between occurrence records based on specimens with those based on community observations revealed a slightly higher average completeness ratio for the latter. Incomplete sampling was highest in regions facing the most severe threats from a rapid changing climate—particularly in areas surrounding Hudson Bay.

The study proposes initiatives of community partnerships to increase both opportunistic sampling, as well as structured surveys. As human footprint is found to be the main driver behind inventory completeness, the authors argue that such efforts must be directed far from densely-populated regions, if they are to be effective in filling data gaps.

Shirey V, Belitz MW, Barve V and Guralnick R (2021) A complete inventory of North American butterfly occurrence data: narrowing data gaps, but increasing bias. Ecography. Wiley 44(4): 537–547. Available at: