Why are ground beetles good as ecological indicators?? Help!!!!

[zoologist123]

Hi, Im doing my project on ground beetles and how they can be used as indicators for habitats, but am a bit stuck about why! Can anyone help?

[Dogghound]

Ground beetles (carabidae) make good ecological indicators due to their biology being sensitive to disturbance. This would mean that in poor environments you would get less species diversity and less abundance and visa versa. They are also moderately easy to identify and collect which makes them better than say Diptera species etc. They are very interesting once you study them with certain species having set habitats, and some have evolved to these habitats. So in some cases their presence can infact show roughly how old the habitat is or what it was in the past or its connection with surrounding habitats. Also they are relatively low on the food chain so if theres lots of ground beetles likely to be lots of shrews and other predators, so you can build a picture of the habitat as a whole.

[Heart-shaped World]

My guess would be that: Coleoptera is the largest of orders (~25% of all animals) so should be most able to demonstrate evolutionary theory and habitat/biodiversity relationships. Ground Beetles (~350 species in the British Isles) would then be an obvious choice as

i) their surface activity allow the relatively modest technique of pitfall trapping to achieve a good representative sample of abundance and diversity.

ii) Ground Beetles are thought to be well developed within the order, by and large have an annual life cycle, are often predatory and largely tied to limited ranges of soil moisture levels.

Don't forget to get out marvel at their beauty too, I mean Carabus monilis should bring out a spontaneous round of applause!

[Paul mabbott]

If they are .... I'm sure you'll look at some of the work of Luff and colleagues (Rushton, Eyre &c).

My personal view (and I've done a lot of work on this) and my advice is conditional! They're not necessarily good indicators for all habitats and perhaps only indicators of a few aspects of any broad habitat type.

I have my doubts about the value of any animal group in defining the habitat so I think what you're talking about is assessing the quality of any particular habitat. [Habitats are primarily defined by their flora and it's the flora that determines most of the animal composition.]

Carabids are often described as secondary consumers, primary predators but this is not really true: they are polyphagous omnivores and, in some genera (e.g. Amara, Harpalus) are largely or partly phytophagous - herbivores.
However they are neither at the top of the food chain (especially vertebrates) which is a precarious, variable and difficult to measure position; nor are they at the bottom - numbers and proportions of herbivorous species (moths, weevils, leaf beetles &c) are neither easy to determine, identify or particularly useful: many phytophagous insect species are limited to a few species/genera/families of plants therefore the greater variety of plants you have, the more phytophages you will have. It is easier to count the plants than the insects!

[zoologist123]

Thank you everybody, its all really helpful!!

[JonSadler]

Paul has it spot on here. It is horses for courses. If you are interested in vegetation, woodland, deadwood then use a wider brush (look for other indicators). But they are good indicator family (in addition to other posters comments) because their taxonomy is pretty stable, easy to sample in a systematic manner (as far as any sampling can be systematic) and relatively easy to identify, especially with Martin Luff's new key. They are also great to look at and have a varied and interesting range of life cycles.

Regards
Jon

[Paul mabbott]

Sorry, got called away the other day - minor emergency!

A couple of other comments which I was going to make.

As someone else has mentioned, the suitability of a habitat for various species is determined largely by moisture and temperature in both spring and autumn. In a uniformly wet habitat then there will be a fairly constant suite of species usually varying in size from small Bembidion, Trechus etc to large Carabus &c. On a site (e.g. a wood) with a variety of habitats (dry, damp patches, ponds &c) then there will be variation from one part of the site to another. Forsythe ("Ground Beetles", Richmond) quotes Dibb (1948) who coded most common species for their habitat requirements.

Other factors influencing species composition will be "texture" - you get different species in dense grass, tall grass etc. Area, degree of isolation and disturbance will also affect which species are found: a small wood with a lot of human activity will have a far smaller number of tolerant carabids (especially Nebria brevicollis and Pterostichus madidus) than a large undisturbed one.

Another thing to bear in mind is that what is a good indicator in one part of the world may have a different meaning elsewhere - mainly because of the climate. For instance, in SE England, Abax parallelepipedus is seldom found outside of woodland whereas up here, I find it in the garden!

Only spiders and rove beetles (Staphylinidae) make better indicators than carabids and the latter are far too tricky (identification) to use for routine monitoring.

Good luck.

[zoologist123]

Thanks for all the comments everybody, they are very helpful!

To Paul Mabbott, I am studying in Reading, if that makes any difference to the types of beetles I would expect? I am comparing native woodland habitats and non-native woodland and riparian woodland. Any suggestions on what I might expect? I have found Abax parallelepipedus in all these habitats and mostly Pterostichus madidus, with things like Trechus, Bembidion, Asaphidion, Calathus in the native/ancient wood. I also keyed Trechus subnotatus, which is rare, but unsure if it occurs in this region?

[Paul mabbott]

Originally Posted by zoologist123

......... I also keyed Trechus subnotatus, which is rare, but unsure if it occurs in this region?

I quote Martin Luff re Trechus subnotatus: "In man-made habitats including compost, rubble and litter. ..... A recent immigrant to Britain ..... known only from Yorkshire, Devon and near Dublin; very scarce."

Quite possibly this is an adventive species which is spreading through the country but I would advise getting it verified by an expert and also reporting it ...

[Paul mabbott]

Originally Posted by zoologist123

........ I am studying in Reading, if that makes any difference to the types of beetles I would expect? I am comparing native woodland habitats and non-native woodland and riparian woodland. Any suggestions on what I might expect? I have found Abax parallelepipedus in all these habitats and mostly Pterostichus madidus, with things like Trechus, Bembidion, Asaphidion, Calathus in the native/ancient wood. I also keyed Trechus subnotatus, which is rare, but unsure if it occurs in this region?

I would expect your findings to be much like mine in London/Essex and little difference in species composition between native/non-native if the non-native woods are old enough to have developed good litter. The riparian areas will, of course, have a much different species composition.

For what it's worth, I would expect Abax in all serious woods! Pt madidus & Nebria brevicollis in disturbed, restricted, artificial woods with the latter being predominant in wet areas. Calathus piceus is a true woodland species but of light, scrubby woods. Trechus quadristriatus & T. obtusus are similar although they seem to have slightly different preferences which I really wouldn't want to define! Asaphidion curtum is quite common in moist areas whereas A. stierlini tends to be confined to clay soils; the other Asaphidion spp are really quite rare.

Bembidion spp are quite numerous and very interesting - they like different types of soil as well as varying degrees of humidity.

In smaller numbers I would expect you to fiind various Carabus (esp. C. violaceus/problematicus and Cychrus caraboides in wet, mollusc-rich areas. I would also expect a variety of Notiophilus spp (esp. N. rufipes in woodland)...... and more!