Wales Biodiversity Partnership

Invertebrates

Invertebrates are generally inconspicuous but they dominate biodiversity in Wales, as elsewhere. In Welsh terrestrial and freshwater environments there are probably more than 20,000 different species of macro-invertebrates and, as an example of their abundance, it has been estimated that there are more spiders in a three-hectare field than there are sheep in Wales. Invertebrates occupy all possible habitats from crevices in inter-tidal rocks to scree on the summits of our mountain tops, from birds’ nests to saturated moss at the edge of waterfalls. This extraordinary diversity is possible because of the specialised niches that many species inhabit as a result of their adaptations to specific environmental conditions. They are also crucially important to the health of ecosystems. From the earthworms that aerate our soil, to the bees that pollinate our crops, the woodlice that break down decaying plant material, the mussels that filter our river water, and the ladybirds that eat pest aphids, we rely on invertebrates for the basic resources we depend upon.

Invertebrates pose unique problems for conservation because of a combination of factors that together make many of our species vulnerable to change. Foremost amongst these is the annual life cycle that is characteristic of the vast majority of invertebrates, requiring that suitable conditions for breeding are present at the right time and in the right place each year. Most invertebrates lack the longevity of plants and vertebrates that allows them several attempts to reproduce. The small size of most invertebrates allows them to occupy micro-habitats - entire populations can be contained within small areas. This makes them particularly vulnerable if important small-scale features are inappropriately managed. Invertebrates are often highly sensitive to micro-climate and hence vegetation structure. Different life-stages often require different developmental conditions, making the presence of ecotones and juxtaposition of habitat mosaics especially important. Many species have poor dispersal ability and hence management must ensure that breeding habitat is within colonisation range at all times. Some species, such as those of pioneer habitats, are adapted for dispersal and will colonise new patches at some distance from their natal sites, but will require frequent (usually annual) management to create new patches. Others exhibit metapopulation dynamics and require patches of suitable habitat to be distributed at landscape scale.

Shrill carder bee
Bumblebees

Southern damslefly
Dragonflies

Species
Butterflies & Moths

Ichneumon

Examples of the diversity of the Welsh invertebrate fauna
Arachnida (spiders etc.) c550 species
Crustacea (woodlice, water fleas, etc.) c250 species
Mollusca (snails, slugs, etc.) c170 species
Coleoptera (beetles) c3000 species
Diptera (flies) c4000 species
Hymenoptera [excluding parasitic wasps] (bees, wasps, sawflies) c750 species
Hemiptera (bugs, leafhoppers, aphids, etc.) c1200 species
Lepidoptera (butterflies, moths) c1800 species
Trichoptera (caddisflies) c160 species

Barred Green Colonel

Invertebrate Conservation in Wales
There are eight non-marine invertebrates included on Annex II of the EC Habitats & Species Directive that occur in Wales, represented here on 22 Special Areas of Conservation. Twelve species are given Full Protection under Schedule 5 of the Wildlife & Countryside Act and Section 7 of the Environment (Wales) Act contains 215 invertebrate species. 69 of the NERC species are registered as ‘Research Only’ to indicate that further information is required to elucidate the scale of and reason for their decline. Of the remainder, 33 (15%) are believed to be extinct in Wales and several others, including the belted beauty moth Lycia zonaria and the soldierfly Odontomyia hydroleon, are seriously endangered. Invertebrates are recognised as Qualifying Features on 158 SSSIs, represented by 88 different species across 14 Orders.
Our rarest invertebrate species may be given protection under UK and international legislation but the conservation of the vast majority of species depends on recognition of specific habitat conditions that are capable of supporting rich assemblages of species. Some of the more popular groups benefit from having dedicated societies with a presence in Wales. Butterfly Conservation Wales and the British Dragonfly Society are valuable partners in the task to conserve our invertebrate fauna and Buglife are also becoming increasingly involved. Inevitably, however, the scope and complexity of the Welsh invertebrate fauna means that no single forum is capable of providing the necessary expertise and much of our knowledge is derived from the efforts of individual specialists, many of whom will be based outside Wales.

Top image shows Cicindela maritima (dune tiger beetle) - a scarce inhabitant of foredunes in England and Wales, with several Welsh sites including Morfa Dyffryn and Whiteford supporting strong populations.

Image © Adriam Fowles

Bottom image shows Odontomyia hydroleon (Barred Green Colonel) - a rare soldier fly occurring in only two sites in the UK. The base-rich flushes at Banc y Mwldan SSSI in Ceredigion is the only location in Wales for this species.

Image © NRW /MJ Hammett)