Climate change might de-couple plant-pollinator relationships if species respond
differentially to environmental cues, such as temperature, but studies have been
hindered by lack of long-term data. This research validates natural history collections
as a source of long-term phenological data and, using these data, investigates the
phenological responses to temperature of flowering in British orchids and flight in
their pollinators.
Herbarium specimens of O. sphegodes collected in the UK between 1848 and 1958
were compared to direct observation of peak flowering time in one population located
in Southern England between 1975 and 2006. The response of flowering time to
variation in mean spring temperature was statistically identical in both sets of data,
providing the first direct validation of the use of herbarium collections to examine the
relationships between phenology and climate. Using three important pollinator models:
the solitary bee Andrena nigroaenea the digger wasp Argogorytes mystaceus, and the
moth Euclidia glyphica, museum specimens and field observation gave statistically
identical results, confirming the value of museum collections as a source of long-term
phenological data for insects.
For twelve of the fifteen orchid species studied, flowering advanced between 4.2 and
8.6 days for each 1°C increase in mean spring temperature, establishing phenological
signals of flowering response to temperature. For all species mean monthly
temperature in March, April or May was identified as a key temperature variable.
For the sexually deceptive orchid O. sphegodes there is considerable potential for a
loss of synchrony between peak flowering time and peak flight of the primary
pollinator, males of A. nigroaenea with further rises in spring temperature. The
advancement in peak flight of the female bee with climate warming exacerbates the
potential for disruption of pollination success.
Findings of this research reaffirm the need for detailed knowledge at species level in
understanding the consequences of climate-driven phenological shifts for plants and
their pollinators.
Key words: Central England Temperature (CET), climate change, flight time,
flowering time, herbarium specimens, Hymenoptera, Lepidoptera, museum records,
natural history collections, Orchidaceae, phenolog
