Thursday, August 11, 2016: 9:00 AM
Grand Floridian Blrm D, Ft Lauderdale Convention Center
Background/Question/Methods
Much of the spatial synchrony in ecological variables is thought to result from Moran effects: spatially synchronised environmental drivers, acting both directly and through trophic and other ecological interactions. Fluctuations in these drivers produce synchronised ecological fluctuations, with their own characteristic timescales of action, which may be hard to identify. Climate change may result in modifications to the strength of these drivers and their effects.
In order to dis-aggregate fluctuations by timescale, we build statistical models using wavelets, connecting drivers of synchrony with their local effects. Using these models we can quantify the ecological synchrony explained by the observed dependence on a given synchronising factor. The temporal resolution of the wavelet transform also allows us to track changes in the strength of the Moran effect over time.
We applied these methods to explain fluctuations in phenology (first flight times) of 20 aphid species in the UK recorded by the Rothamsted Insect Survey, including important crop pests. We also examined fluctuations in the Plankton Colour Index (PCI), an annualised measure of green phytoplankton abundance in UK seas taken from the Continuous Plankton Recorder project. Phytoplankton abundance is related to primary productivity of the oceans.
Results/Conclusions
A strong relationship between first flight times and winter temperatures is found for 18 of the aphid species, with those most strongly related to temperature (mostly active over-winterers, vulnerable to frost) being most strongly spatially synchronised as a result. An average 80 percent of spatial synchrony in their long timescale (>4 years) phenological fluctuations could be explained in this way. The spatial synchrony of slow temperature fluctuations fell over the period of measurement (1976 to 2010), and the corresponding phenological synchrony fell in all 18 species. This drop in synchrony was associated with changes in the North Atlantic Oscillation climate index.
Extending the wavelet Moran approach to multiple drivers of synchrony in plankton enables us to explain 60 percent of the low frequency synchrony in PCI fluctuations, in terms of the combined effects of sea surface temperatures and predation by Calanus finmarchicus. The environmental and trophic effects in the model reinforce each other. Climate change will thus affect spatial synchrony in phytoplankton both directly, via a temperature-mediated Moran effect, and indirectly via the observed changes in Cal. Fin. abundance as its range moves north. Changes in both the strength of Moran effects and their interactions are likely to be a general feature of climate change.