Future work and caveats
Our study is unique in its spatial and taxonomic extent, yet the
majority of the species used are in Odonata and Lepidoptera. This is not
surprising, since these clades have relatively large body sizes and are
easy to see and photograph. In addition to the taxonomic biases in our
dataset, the 25 x 25-km grid cells that were included in our analyses
were biased geographically, with most cells occurring in metropolitan
areas in the Eastern Temperate Forests ecoregion and along the
California Coast. There are noticeable sampling gaps in the Great
Plains, North American deserts, and the complex and diverse ecoregions
of southern Mexico. Finally, we note that increasing observer effort,
measured as the number of observations, did show a significant, albeit
relatively weak effect on phenology estimates. Although our modeling
framework attempted to control for these effects, care must be taken
when fitting estimations using community science datasets. As the amount
of available incidental data continues to grow, we expect better
spatial, and phylogenetic resolution, albeit with biases still likely,
unless concerted efforts are made by community scientists to survey more
rural locations
(Shirey et al.,
2021).
Even if more species-specific phenology estimates can be generated for
insects, our full ability to understand drivers of insect phenology will
be hampered by the lack of available trait data. We had enough
incidental intra-annual observations to generate phenological estimates
for 154 species with at least five year-by-cell combinations but could
only use 101 species because of missing trait data. This is particularly
problematic because our results highlight the importance of life history
traits in predicting all aspects of adult insect phenology. Therefore,
to better understand how insects will respond to climate change and
urbanization, it is imperative that continued effort goes into
generating, compiling, and archiving openly available insect life
history information
(e.g.,
Middleton-Welling et al., 2020). Improving insect trait knowledge and
access will allow researchers to better understand ecological processes
using the accelerating accumulation of occurrence and other natural
history records. This research showcases a framework to gather and use
these resources to answer fundamental questions about the duration of
adult activity across broad spatial and phylogenetic scales.