Fossil insects and ecosystem dynamics in wetlands: implications for biodiversity and conservation

Abstract

We review the uses of fossil insects, particularly Coleoptera (beetles) and Chironomidae (non-biting midges) from ancient deposits to inform the study of wetland ecosystems and their ecological and restoration processes. In particular, we focus on two contrasting ecosystems, drawing upon research undertaken by us on British raised mire peats and shallow lake systems, one an essentially terrestrial ecosystem, the other aquatic, but in which wetland insects play an important and integral part. The study of raised mire peats suggests that faunal stability is a characteristic of these wetland systems, over what appear to be extensive periods of time (up to several millennia), whilst studies of shallow lake ecosystems over recent timescales indicates that faunal instability appears to be more common, usually driven by increasing eutrophication. Drawing upon a series of fossil Coleoptera records spanning several thousand years from HatWeld Moors, south Yorkshire, we reconstruct in some detail the mire's ontogeny and Xuctuations in site hydrology and vegetation cover, illustrating the intimate association between substrate, topography and peat development. A comparison between fossil and modern beetle populations indicates that the faunal characteristics of this mire and its adjacent neighbour, Thorne Moors, become established during the early phases of peat development, including its rare endemics, and that the faunal biodiversity on the sites today is dictated by complex site histories. The over-riding characteristic of these faunas is of stability over several thousand years, which has important implications for the restoration of degraded sites, especially those where refugial areas are limited. In contrast, analyses of fossil Chironomidae from shallow 1 C lakes allow researchers to track changes in limnological status and while attempts have been made to reconstruct changes in nutrient levels quantitatively, the chironomids respond indirectly to such changes, typically mediated through complex ecosystem dynamics such as changes in Wsh and/or macrophyte communities. These changes are illustrated via historic chironomid stratigraphies and diversity indices from a range of shallow lakes located across Britain: Slapton Ley, Frensham Great Pond, Fleet Pond, Kyre Pool and Barnes Loch. These sites have shown varying degrees of eutrophication over recent timescales which tends to be associated with a decline in chironomid diversity. While complex functional processes exist within these ecosystems, our evidence suggests that one of the key drivers in the loss of shallow lake chironomid diversity appears to be the loss of aquatic macrophytes. Overall, while chironomids do show a clear response to altered nutrient regimes, multi-proxy reconstructions are recommended for a clear interpretation of past change. We conclude that if we are to have a better understanding of biota at the ecosystem level we need to know more of the complex interactions between diVerent insect groups as well as with other animal and plant communities....

Harnessing the potential of the multi‐indicator palaeoecological approach: an assessment of the nature and causes of ecological change in a eutrophic shallow lake

“…C. scutellata , Cricotopus spp., P. sordidellus ). Submerged plants can provide protection and a food source for phytophagous chironomids and act as a stabiliser for sediment dwelling taxa (Pinder, ; Whitehouse et al ., ).…”

The butterfly fauna of Wisconsin bogs: lessons for conservation

“…Instead, appropriate, consistent long-term landscape conditions cause both the plants and the associated insects. Just as plants and insects got ''sunk and dunked'' together in temperate-zone bogs as relicts due to climatic oscillations (Dapkus 2004a;Spitzer and Danks 2006;Whitehouse et al 2008), so too only insects finding consistent resources in the surrounding landscape exist to benefit when native plants are restored to a garden or reserve. Whatever shortfalls of such resource consistency determine what insects do not benefit from such plantings.…”

“…Whatever shortfalls of such resource consistency determine what insects do not benefit from such plantings. A focus on plants can lead to restoration that destroys the continuity of required resources in the process, and loses the associated insects (Kirby 1992), usually the ones most restricted to that site in the first place (such as described in Whitehouse et al 2008). An alternate approach focuses on what's ''right'' about those plants and conditions now (what's been adequately consistent, however minimally, in resources to maintain such insect faunas), and maintaining that consistency, even if there are ''wrong'' things too.…”

“…Although often viewed as a long-lived successional stage between open water and forest in glaciated landscapes, peatlands can get reset to an earlier successional stage (Curtis 1959). Since bogs are well known for their relatively stable vegetations and insect faunas over the long term, they can also be viewed as a climax community (Spitzer et al 1999;Spitzer and Danks 2006;Whitehouse 2006;Whitehouse et al 2008). While often considered relatively uniform floristically both within and among sites, bogs actually contain many microhabitats (Väisänen 1992;Spitzer and Danks 2006;Turlure et al 2009).…”

Assessing abundance patterns of specialized bog butterflies over 12 years in northern Wisconsin USA

“…In temperate areas of North America and Europe, bog (peatland) vegetation is naturally rare and isolated, forming a low proportion of the natural landscape (Spitzer et al 1999;Spitzer and Danks 2006;Whitehouse 2006;Whitehouse et al 2008). In Wisconsin, peatlands occur primarily in central and northern areas (Curtis 1959).…”