The effects of climate and habitat on Butterfly
University of Southampton, School of Biological Sciences,
Biodiveristy is threatened globally and there is a need to monitor and understand
future changes. Rigourous assessment of trends in insect populations is difficult
because they are a species-rich, yet little known taxa. Butterflies are among the most
practical insect group to study, given their extensive long-term, large-scale datasets.
The effects of climate and habitat of butterfly populations are examined to
understand the implications of environmental change for these, and other, insect taxa.
It is found that first appearance (phenology) of most British butterflies has advanced
in the last two decades and is strongly related to climate. Further warming is
predicted to advance appearance by 2 to 6 days per 1°C temperature increase. Despite
this strong relationship between appearance dates and temperature over time, a
comparable geographical relationship between temperature and timing was not
detected for over a third of species analysed, suggesting their populations may be
adapted to their local climates.
A seasonal switch in egg-laying requirements of the butterfly, Polyommatus
bellargus, demonstrates an interaction between niche requirements and climate
determine fluctuations in populations. The effect of climate on populations of other
butterflies was studied using national weather records and indices of population
change since 1976. Strong associations between weather and population fluctuations
were found in 28 out of 31 species studied. Models derived from these associations
predict that most species will increase in abundance under warmer climates.
Large scale habitat modification is known to have profoundly affected butterfly
populations over the last century. Data from a farm scale evaluation ofthe effects of
management for genetically modified herbicide-tolerant (GMHT) crops showed that
effects on vegetation cover and flowering at this scale has marked knock-on effects
for butterflies and other mobile, nectar feeding insects.
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