Are early blooming plant species more phenologically responsive?

Shifts in flowering phenology is one of the most well-studied, ecological signs of climate change. However, the extent and magnitude of observed phenological change varies significantly among both species and biomes, and general ecological rules predicting phenological change have yet to emerge. Using 2373 herbarium records of 21 common forest understory herbaceous species with diverse bloom times in Pennsylvania, USA we elucidate which species have adjusted their flowering times the most over the last century. Our results show that spring-blooming forbs exhibited the strongest phenological shifts over the past century. A negative relationship was detected between the shifts in flowering date and typical median bloom time. Early-blooming species flowered 2 days earlier per decade, while flowering time among summer-blooming remained remarkably consistent. Despite such patterns, climate change in our study region has driven temperatures higher year-round and not to a disproportionately greater degree in spring. The fitness consequences of these contrasting phenological responses also remain largely unexplored. Given the ecological consequences of phenological mismatches between plants and animals, a holistic framework that predicts phenological sensitivity among species and biomes that includes patterns that expand what we highlight here is urgently needed.