Inconsistent results from trait-based analyses of moth trends point to complex drivers of change

Trait-based approaches are advocated for their ability to predict population declines in data-deficient taxa and regions, potentially benefiting biodiversity conservation. Several reviews have, however, highlighted inconsistent results between traits studies, sometimes even for the same taxonomic group and biogeographical region. Traits studies of moths are commonplace and support this pattern of inconsistency, albeit with largely congruous results for traits relating to dietary and habitat breadth. We use the most comprehensive moth trends available, those for British macro-moths, to test the utility of traits approaches using a multi-model inference approach whilst controlling for phylogeny. We expected our results to add to the general pattern of inconsistency among moth traits studies. We found strong associations for several traits; woodland moths and those feeding on grasses and lichens or algae tend to be faring well, whereas declines were associated with univoltinism, narrow diet breadth, nocturnal flight period, overwintering as an egg, moorland habitat preference, and feeding on forbs. Abundance and distribution trends produced different outcomes, with no trait having significant associations for both measures of change. Our findings corroborate previous studies for certain traits, but for others they provide further evidence that traits analyses can yield inconclusive or contradictory results. We suggest that these inconsistencies are rooted in the complex drivers of population change, as well as incomplete knowledge of some traits. Overall, our study adds to evidence that unequivocal relationships between traits and population changes are lacking for most parameters, limiting the usefulness of trait-based approaches in predicting species declines.