The ecology and conservation of beetles (coleoptera) living on exposed riverine sediments
Situated at the very juncture of the aquatic and terrestrial, exposed riverine sediments (ERS) are poorly vegetated alluvial deposits of silts, sands and gravels, which are habitat for a wide range of rare and highly specialised beetles. The thesis aimed to assess: (1) the conservation value of ERS beetles; (2) their changing habitat requirements and spatial population structure over a range of spatio-temporal scales; and (3) their vulnerability to anthropogenic threats, in particular, trampling by livestock. A database of British occurrence records was used to assess the conservation value of ERS specialist beetles. Beetle sampling implemented quadrat hand searches and modified dry pitfall traps, and spatial distribution and population structure in relation to a suite of environmental variables was analysed using correlation, SADIE analysis, and mark recapture methods. ERS beetles were found to have considerable conservation importance and their spatial distribution was related to habitat characteristics at the within-patch, patch, reach, and stream segment scales. These distributions varied temporally in response to flow level and trampling intensity, and trampling intensity was shown to reduce the conservation value of beetle assemblages. The likely responses to a variety of threats, such as regulation and channelization, mediated by varying inter-patch spatial population structure were evaluated.