Mokgatla, I have discussed cons and pros of parataxonomic sorting in the attached paper.

Frank

Article Parataxonomy vs. taxonomy in biodiversity studies - Pitfalls...

Thanks a lot Frank! 

I guess now my supervisor will have to help me with ID in order to generate more accurate data than to rely on PU data.

That would be a good outcome! Taxonomic identification always leads to much more useful results. Good luck with your project!

Mokgatla, I think the choice of (macro)invertebrate group to focus on is critical. Consider what is there, activity patterns, general behaviour, vegetation type and how much is known about the taxonomy/diversity. Using parataxonomy in some invertebrates, such as spiders, could drive you insane and may give you unreliable data. Frank's paper is useful, there are others dealing with the same subject. Interesting investigation. Good luck.

There is a difference between using PUs because you do not have the knowledge or facilities to reach correct taxonomic determination, and situations (common in many tropical invertebrate groups) where much of the fauna has never been described. There is a huge backlog of alpha taxonomy in many groups. Here, "morphospecies" are a valuable first step in quantifying the diversity of particular sites. The problem becomes more serious if you are trying to estimate similarities and differences among sites, or to estimate turnover in composition.

Having said that, Tarombera Mwabvu has highlighted an important point. In many areas, there is species turnover between sites, but the suite of traits: food, position, life cycle etc remain relatively constant, as, sometimes, does the number of taxonomic entities involved. As usual, the approach you use depends both on the practical, what am I or anybody capable of doing in the circumstances, and theoretical: what is the focus of my study? Certainly, if you interest is biogeographical, real taxonomy is needed. If it is functional, then the balance of traits may be more relevant.

One approach is to identify everything correctly, no matter how long it takes or what resources you have to get. This can become expensive and time-consuming, but it has many rewards. One gains experience in practical taxonomy, respectful relationships with expert taxonomists, and publications on new species.

Another valid approach is to allow a certain amount of time for each sample. Materials that cannot be identified during the time frame may be identified to family or genus, e.g., "Arenicola sp. 1, sp. 2, sp. 3" or "Arenicolidae indet." or even "Polychaeta indet." This method can work well if a taxonomic expert does the work. But for a beginner, it can be a disaster.

Or, you can focus on only part of the data, e.g., one taxonomic group. This may not be feasible in your case.

Perhaps there are other middle roads that you can devise.

Whatever approach you decide to use, make the procedure logical, consistent, and transparent; that is, make a point of describing your procedure as part of the finished paper.

Thanks a lot for your inputs  and brilliant advises!

I will have to spend more time behind the microscope until December.

I think using the concept of morphotypes in preliminary reports and broad overviews can be helpful and saves a lot of time. However once these are used in estimates of diversity or other statistical approaches they inevitably bring in some (sometimes huge) errors.

But there can be some useful data in these morpotypes as well. Ecomorphotypes may blow your diversity estimates to pieces but they contain some information about the environment which might get lost of these specimen are “just” identified to species (or even subspecies) level without noting these differences.

But given the grasp of genetics on the study of recent species it makes sense (in some cases or for some questions) to identify them down to a very specific level (right down to distinguishing populations by genetics). In palaeotology on the other hand we can almost exclusively use the morphospecies concept. We even knowingly use parataxonomies there for body parts of certain groups (eg. Ammonite aptychii) (even extensively in plants) and every once in a while some of these parts turn out to belong together. In these cases the Parataxonomy is often retained (for example in dimorphic species of ammonites).

I will read your paper Frank-Thorsten and maybe I can give some more advise (or change my point of view) after that.

"... i have not chosen a focal taxa. As a result i am dealing with a lot of groups and some are difficult to identify to species level."

I would say it would be less difficult if you would choose a focal taxon. A group that is easy to sample, includes species that are likely sensitive to megaherbivores (groundbeetles?) and has a comparably stable taxonomy (or you know somebody who is working with this group). After a while you will become a taxonomist, problem resolved.