Holocene insect pioneer colonization of post-glacial dune sands exemplified by tiger beetle burrows

Many ecosystems today in temperate zones are the result of colonization of barren substrates deposited or exposed as a result of deglaciation, around the start of the Holocene. Direct evidence of post-glacial colonization, in the form of life traces such as tracks and burrows, is typically rare and erased by later succession unless buried deeply within a short time interval, as is possible in dune sands. Tiger beetles (Coleoptera: Cicindelidae) are an example of early successional tracemaking colonists widely distributed in open habitats worldwide and are well known from coastal and inland dunes in Europe today. Coastal dunes at the Vistula Spit in Poland, dating back to the time of post-glacial stabilization of modern Baltic Sea levels, contain buried long, narrow, subfossil burrows, which are variable in shape. Some of them resemble linear or J-shaped burrows made by living cicindelids both in situ in exposed drift sands within the inland European Sand Belt and in laboratory settings after being wild-caught. A new locality for the modern Viennese tiger beetle Cylindera ( Cicindela) arenaria viennensis, Schrank, 1781, whose larval burrowing was examined for reference, is reported at Mnin in the Przedbórz Upland, Poland, where there was a suitable substrate made up of aeolian sand deposited earlier in the Holocene but opened up by mining. The subfossil burrows at the Vistula Spit, if they were made by cicindelids and other early successional species, could represent similar colonization of comparable pioneer habitats dating back millennia when those coastal dunes were young. Although the body fossil record of tiger beetles is very poor, ichnological evidence of their potential presence may be useful for inferring their biogeographical history, complementing prior knowledge from modern distributions or phylogenetic histories.