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Putting another dot on the ground beetle distribution map

Routine monitoring at the ECN North Wyke site reveals a new and unexpected locality for a species of carabid beetle
Putting another dot on the ground beetle distribution map

Pterostichus cristatus. Photo by John Walters

Routine monitoring of carabid (or ground) beetles at ECN terrestrial sites has enabled us to establish unique long-term records of these invertebrates, spanning over 20 years. These records have already been subject to a number of scientific papers reporting on trends and community dynamics (Morecroft, et al., 2009; Brooks, et al., 2012; Pozsgai et al., 2015; Pozsgai et al. 2016).

In the course of our routine monitoring required to detect and understand the causes of environmental change, we occasionally make unexpected discoveries worthy of publication in their own right.  The latest of these serendipitous findings, which has just been published by Corbett and Whitehead (2017), is the first detection of a ground beetle species way outside its previously understood distributional limit.

The authors report that a single male specimen of Pterostichus cristatus was found in January 2016 at the ECN site North Wyke, Devon, a farm run by Rothamsted Research. Most usually found in upland woodland in cool, oceanic regions, and considered nationally scarce, it was the only specimen of P. cristatus to be found in around 9000 pitfall traps set over a 21 year period. Before now, its known British range extended from the Scottish Highlands to north-west England.  It is considered that this population was accidentally introduced in the nineteenth century (Eversham and Arnold, 1992). North Wyke, on the northern fringe of Dartmoor, is some 450 km further south and accidental introduction is highly unlikely.

This ECN finding, therefore, establishes a stronger case for consideration of this P. cristatus as indigenous to the British Isles.

In Europe, P. cristatus is found in a narrow zone running south through France and adjacent countries into Italy. The new British location in Devon could be considered a further outpost of this distribution, perhaps representing a previously unknown relict indigenous population.

It's not the first time that ECN recording has led to a new species record: in 2010, another ground beetle, Leistus rufomarginatus, was identified for the first time at the Cairngorms ECN site.

As we continue to monitor our sites and extend our long-term records, we will remain alert for the unexpected.

 

Further information and references