The use of percentile-percentile plots to compare differences in seasonal dynamics, illustrated by the case of ground beetles (Coleoptera, Carabidae) reacting to urbanisation

Abstract

We suggest the use of a graphical method, involving a standardisation of the seasonal activity curves and their subsequent comparison by a percentile-percentile graph as an easy way to compare seasonal activities in arthropods. To test the suitability of the suggested method, the seasonal dynamics of three common carabid beetles, Pterostichus melanarius, Nebria brevicollis and Carabus nemoralis were compared in three habitats (rural forest, suburban and urban forest fragments) along an urbanisation gradient near Sorø, Denmark, in 2004 and 2005. Activity in urban habitats often started earlier, possibly caused by the warmer microclimate in the city centre. The comparative graphs indicated the unsuitability of the suburban habitat for N. brevicollis, and the differential suitability as overwintering habitat of the three urbanisation stages for C. nemoralis. The method seems suitable to analyse differences in seasonal activity while being more sensitive than traditional seasonal-activity graphs.