Status changes in the wild bees of north-eastern North America over 125 years revealed through museum specimens

1. Though recent literature highlights widespread bee declines, detailed information on local communities and individual species remains scarce. In order to accurately direct conservation initiatives and to evaluate the status of wild bees, regional long-term data on these populations are critical. 2. This study analysed 119 wild bee species within New Hampshire, USA, over 125 years (1891-2016) using museum data. Examining pollinator communities across regional spatial scales has the power to highlight small-scale changes that go undetected in larger investigations. In the light of unknown effects of introduced species and cumulative range expansions of exotic taxa, monitoring wild communities closely and extensively over time is becoming increasingly important. 3. The composition of the New Hampshire wild bee community has changed between the historical and contemporary time periods with 14 species found to be statistically significantly declining and eight species found to be statistically significantly increasing. Over half of the species found to be in statistically significant decline experienced a significant elevational or latitudinal range shift, many are regionally important crop pollinators, and all are native New Hampshire taxa. 4. Guild affiliations were not found to be indicators of change, suggesting that the requirements and behaviour of individual species must be examined in order to evaluate the current and future stability of the wild bee community. Many of these species occur in varied landscapes, climates, and habitats; thus, monitoring changes at regional scales is critical to informing conservation recommendations broadly and focusing future research directions.