Transcript Life history traits

Climate change impacts on the phenology of Odonata
Christopher Hassall*, David J. Thompson*, Graham C. French# and Ian F. Harvey*
*School of Biological Sciences, University of Liverpool #British Dragonfly Society
Aim: To investigate patterns in changing phenology in the Odonata, a
taxon important both in ecological networks and as an indicator of
habitat quality.
Introduction
Method
• The Odonata colonised temperate latitudes through an
array of adaptations, including flexibility in the timing of life
history transitions.
• Records from 1960-2005 were extracted for each of the 37
British species of Odonata.
• We measured the response of odonate phenology over
the past 40 years and related those changes to variations in
temperature.
• These were sub-divided into shorter time periods, the
number of which depended upon the number of records for
each species thereby achieving maximum resolution for the
study.
• The British Dragonfly Society (BDS) maintains a longterm database containing over 400,000 records which is
ideal for investigating temporal changes.
• The 1st (Q1), 2nd (Q2) and 3rd (Q3) quartile flight dates were
found for each time period and these were regressed against
temperature using Kendall’s robust line-fit method.
Impact of temperature on phenology
• No
species
exhibited
significant
relationships between temperature and
flight date after a Bonferroni correction.
However, some trends appear convincing
(e.g. Fig. 2, F=42.32, p<0.001).
• After controlling for phylogeny, samples
of slopes (Kendall’s τ, e.g. Fig 2) between
mean CET and Q1 flight date were
significantly different from zero (t=-2.65,
p=0.017; Fig 1).
Fig. 2 – Phenology of Pyrrhosoma nymphula
• Q3 flight date did not vary consistently.
Some species’ responses suggested a
extended
flight
period
at
higher
temperatures (e.g. Fig. 3 squares) and
others simply a shift in timing (Fig. 3
circles).
Fig. 1 – Variation in flight dates with (a)
time, (b) temperature and (c) temperaturetime residuals.
Fig. 3 – Change in phenology across flight period in P.
nymphula (circles) and Erythromma najas (squares).
Life history traits and phenological response
• Species which diapause during the egg
stage exhibited responses in phenology
which, when pooled, were not significantly
different from zero (Fig. 4).
Fig. 4 – Diapause and phenology
• It may be that exposure to different
temperature regimes during development
affects the way in which the species
respond throughout their ontogeny.
Pyrrhosoma nymphula
Conclusions
• Advances in phenology have been observed in a range of taxa, including
Odonata (Fig. 5). Shifts seen in aquatic organisms are of a similar magnitude to
those of terrestrial organisms.
• Differences in the responses of species within a community could result in a loss
of synchronicity with impacts on ecosystem functioning.
• The Odonata are voracious carnivores and a shift in the timing and length of the
terrestrial/aquatic life history stages could impact prey populations.
• Life history traits can influence phenology.
• Advances in phenology of adults extend the time that their offspring have to
develop, increasing the chance of a shift in voltinism.
Fig. 5 – Phenological shifts in other taxa
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