Abstract
Aim Understanding drivers of insect population declines is essential for the development of successful conservation plans, but data limitations restrict assessment across spatial and temporal scales. Museum records represent a unique source of historical data that can be leveraged to investigate temporal trends in insect communities. Native lady beetle decline has been attributed to competition with established alien species and landscape change, but the relative importance of these drivers is difficult to measure with short-term field-based studies. Here we assessed distribution patterns for native lady beetle species over 12 decades using museum records and evaluated the relative importance of alien species and landscape change as long-term drivers contributing to changes in lady beetle communities.
Location Ohio, USA.
Methods We compiled occurrence records for 28 lady beetle species collected in Ohio, USA from 1900-2018. Incidence-based measures of taxonomic beta-diversity were used to evaluate changes in lady beetle community composition over time. To evaluate the relative influence of temporal, spatial, landscape, and community drivers on the captures of native lady beetles, we constructed negative binomial generalized additive models.
Results We report evidence of declines in captures for several native species, including Adalia bipunctata, Coccinella novemnotata, Hippodamia convergens, and Coleomegilla maculata. Importantly, the timing, severity, and drivers of these documented declines were species-specific. Changes in lady beetle species composition began in the 1980s, when processes of species loss/gain and turnover shifted communities towards dominance by a few alien lady beetle species. Land cover change also was associated with declines in captures, particularly for C. novemnotata which declined prior to the arrival of alien species in the state.
Main conclusions Our study documented shifts in Ohio’s lady beetle communities beginning in the 1980s as alien species supplanted natives. Drivers of declines in captures of native lady beetle species were highly species-specific, emphasizing that mechanisms driving population losses cannot be generalized even among closely related species. These findings also indicate the importance of museum holdings and the analysis of species-level data when studying temporal trends in insect populations.
Competing Interest Statement
The authors have declared no competing interest.
