Biologists use model organisms in their studies with the hope that new discoveries will provide insight in the features of the same species but also of other species that they are supposed to represent. This generalization helps to simplify their research. Such model organisms usually possess a specific trait that makes them easier to use in experimental set-ups. They may be easy to cultivate, such as in maize (Zea mays) or mice (Mus musculus), they may regenerate easily, such as shown by species in the genus Hydra, or they show a short life span, such as fruitflies (Drosophila melanogaster).
Model species groups or so-called exemplar taxa can be used in ecological studies to clarify the structure of biodiversity by combining taxonomic, phylogenetic, and functional data as expressed locally in an ecosystem (α-diversity), among nearby ecosystems along environmental gradients (β-diversity) and in an area at a much larger, biogeographical scale (γ-diversity). The question is what properties would make a species group ideal as a representative subsample in biodiversity research. Should the model group be monophyletic? Should it represent 5, 10 or more % of the total number of species. Should it consist of generalists, specialists, or both? Should its species be easy to find and easy to identify for fast and clear results, or should they be obscure in order to be less affected by anthropogenic factors? The best answers may depend on the specific question, but maybe there are general features that define an ideal model group. Or is there not such a thing and should ecologists select species groups that they themselves are most familiar with? What is your favorite model species group and why?
Your question reminds me the problem of finding good bioindicators (biomonitors)…
I would try to select species with (i) relatively well-known biology/ecology, (ii) easy to sample and (iii) highly sensitive to environmental changes.
In my opinion, general traits that define an ideal species group as model in ecological studies depends of the scale you consider to build your model and this is variable between regions.
Some ideas :
- Habitats can be considered at regions scales or micro environnement scale, and it will change the taxonomic level you have to consider.
- It is ofen helpfully to consider fonctionnal groups (and not only monophylétic groups) that have comparable biomass influences in a well define context.
- Time is another scale which can inluence your model, and it is very difficult to consider in the same model seasonnals species and species who grow very slowly for exemple.
However, some works are now in progress about marine keystones species in desvotes project http://www.devotes-project.eu/ : perhaps the delirevable (available soon) could help you to find more precise ideas?
Some of the traits which can be helpful are:
- a group with well resolved phylogeny (when doing a comparative study on a number of species, phylogenetic correction can be useful).
- a diverse group which went through adaptive radiation, and has multiple recognizable ecomorphs.
- species group which is geographically localized.
- well studied group, with readily available published data on biology and ecology. Already available data can help researcher focus the study on a specific problem and take all possible factors (diet, habitat preference, life history data, behavior...) into account.
A good example are Anolis lizards. Diverse group with well resolved phylogeny, large number of species, multiple specialized ecomorphs and readily available data. Usually, a number of different species belonging to the different ecomorphs can be present on a single small island.
As you said, the best answer depend on the specific question.
For example, some of the widely used indicator taxa, e.g., passerine birds or butterflies, can represent a good biodiversity subsample with regard to their wide diversity in species' ecology, behaviour, specialization and relation with habitat and landscape features. Higher diversity values in these taxa would generally indicate higher habitat diversity - thus usually meaning higher overall biodiversity.
Other taxa, e.g., amphibians or grasshoppers, that are more strictly linked to a habitat type, would be more profitably used for studies of "within habitat" diversity.
In any case, well known and easily recordable taxa would surely make the work easier.
I don't think your question is resolvable (1) at all, and (2) particularly not in a forum like this. There are more than 10,000 publications that address just the issue of the use of surrogates for biodiversity, natural resources, and ecological systems. A very good place to begin is Tim Caro's book "Conservation by proxy". It's not too difficult to identify traits of surrogates that would appear to make them suitable for a particular purpose (e.g., selecting biodiversity conservation areas, tracking ecological trends in another species or attribute), but there are woefully few tests of whether this actually works (and even fewer well-designed and executed tests), and even more disturbing, the results of these tests are highly variable. Surrogates will be with us for the foreseeable future so this is a very important topic, but also with an enormous and complex literature base that makes it very difficult to address such broad questions. I suggest you break your very broad question into a much larger number of very specific ones.
I agree fully with you John.
That said, I'd like to draw attention to the potential of the genus Hydra in understanding freshwater ecosystems. Not only is there a huge wealth of relevant data on Hydra and its ecology, but also on its associated ciliates Kerona and Trichodina, associated giant amoeba (Hydramoeba hydroxena) and associated cladoceran (Anchistropus emarginatus).
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