Please note that the following corrects the various errors in the
RSS Meetings Cards for March and February relating to our next two
meetings.
Next Meeting: Thursday 9 March, 4.30pm (tea 4.00pm)
Spatial Statistics of Slugs and Their Carabid Beetle Predators
David Bohan (IACR, Long Ashton)
Venue: Sheffield Hallam University, Stoddart Building, Room 7138
(Abstract given below)
Following Meeting: Thursday 30 March, 4.30pm (Tea 4.00pm)
Monitoring of Surgical Outcomes:
An Application of Cumulative Sum Procedures
Vern Farewell (University College, London)
Venue: University of Sheffield, Hicks Building, LR 1.
Details of RSS Local Group meetings and all University of Sheffield
Probability & Statistics Departmental Seminars can be found on
http://www.shef.ac.uk/~st1djl/seminars.htm
Spatial Statistics of Slugs and Their Carabid Beetle Predators
David Bohan (IACR, Long Ashton)
Abstract: Slugs are extremely damaging pests in arable situations.
The distribution of the damage, both in space and time, is very
patchy. As a preliminary study to evaluate the spatial and temporal
their dynamics, an explicitly spatial sampling strategy was used to
sample for slugs over a full agricultural year in a field of winter
wheat.
The sampling protocol used a nested series of grids of
sampling points, with inter-sample point distances of 0.25 m, 1 m, 4
m and 16 m. Slug counts at each sample point were analysed using the
SADIE algorithms and were found to be consistent with the laying of
slug eggs on the 0.25 m scale. The larger scale spatial dynamics of
slugs were species specific. The slug Arion intermedius exhibited
stable patches of individuals, of approximately 40 m in diameter,
which persisted for up to one year. Deroceras reticulatum was found
to show spatial randomness in all time periods. The reasons for these
similarities and differences in spatial structuring will be
discussed.
There are few documented predators of slugs. However, the
carabid beetle Pterostichus melanarius has been shown to eat slugs in
laboratory studies. Using a similar pattern of gridded sampling
points, adjacent to the slug sampling grids, P. melanarius was
followed over the year. All captured individuals were then taken back
to the laboratory for their stomach contents to be analysed for slug
proteins. Strong associations between the slugs and carabids were
found in June and July, the months of peak carabid abundance. Where
there were high numbers of slugs, in June, high numbers of carabids
were found, and these P. melanarius had eaten slug protein. In July,
by contrast, where there were carabids that had eaten slug protein,
there were few slug individuals. The changes in slug numbers, from
June to July, were directly related to local counts of carabids.
Thursday 9th March at 4.30 p.m. (tea 4.00p.m.)
Sheffield Hallam University, Room 7138, Stoddart Building
Further information from Marion Rout, Hon Sec (0114 258 4999)
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