The patterns and environmental drivers of summer and autumn fruiting phenology are poorly understood; however, the timing of fruit ripening is important for the nutrition of animals that consume fruits, and for seed dispersal. One of the reasons for this gap in our knowledge of fruiting times is the paucity of long-term records of the autumn phenology of communities of fleshy-fruited species. Herbarium specimens, which are increasingly being digitized and made available online, occasionally contain ripe fruits and can provide a creative solution to this problem, as specimens are available from the 1800’s through the present day. We examined over 15,000 herbarium specimens from herbaria across New England, and found 3,177 specimens with ripe fruits. The specimens belong to 60 species of trees, shrubs, and vines common to New England, 40 of which are native and 20 of which are invasive. We examined patterns in fruiting phenology across species and native vs. invasive status; we also examined changes in fruiting phenology over time, and in relation to annual temperature variation, local temperature variation, and latitude and longitude.
We found that, on average, native species fruit earlier than invasive species by 33 days (p<0.001). The standard deviation in the fruiting times of invasive species is significantly higher than that of native species (p<0.001), which may be due to invasive species maintaining fruits longer into the season. Preliminary analysis shows no significant trends in fruiting phenology over time, or in relation to temperature, latitude and longitude. The protracted nature of fruiting, combined with the temporal and spatial resolution of herbarium specimens, makes it possible detect strong patterns between species, but challenging to track within-species responses to changing environmental cues. The result that invasive species fruit later and last longer into the season is important, given that migratory birds are passing through New England later over time and in warmer years, and thus may be increasingly likely to encounter, consume, and disperse invasive species.