you don't dump pen and paper just because you can create text documents on your smartphone. Neither molecular techniques or morphologic studies alone can fully resolve the issues with species assignment, kinship and evolution (specially because so far we cannot carry a molecular biology lab on our back when in field). Each technique has value, and they need to work together, instead of pitching one against the other.

Dear Asif,

Your question needs to be answered in two parts:

First about morphological assessment: Biodiversity assessment solely based on morphology is challenging, especially with microscopic species. Some species are known to have several cryptic species hidden among themselves. Identification based on morphology cannot reveal this diversity. Here we use the molecular tools to differentiate these species diversity. But this type of analysis cannot be done for each species, hence, we use the high throughput sequencing for diversity analysis. The next part includes the assessment of this data i.e. molecular based approach vs morphology: As you state Molecular-based approaches have eased the way in both cost and time to quickly identify a species. But when we mention about monitoring program, molecular tools reveal huge diversity, but most of the diversity is taxonomically undefined. In order to identify the species appropriately in the monitoring program, you always need a reference for each species. This reference needs to be procured using morphological and molecular approach.

The next part includes the assessment of this data i.e. molecular based approach vs morphology: As you state Molecular-based approaches have eased the way in both cost and time to quickly identify a species. But when we mention about monitoring program, molecular tools reveal huge diversity, but most of the diversity is taxonomically undefined. In order to identify the species appropriately in the monitoring program, you always need a reference for each species. This reference needs to be procured using morphological and molecular approach.

So to conclude, at least we need some time to setup this benchmark sequences to identify species, till then we still need morphological studies to assess species diversity. I hope this was helpful.

Chetan

Chetan,

Thank you for your very informative response. 

You will find many papers emphasizing the importance of both techniques.  Natural selection can result in morphological divergence with little impact on genetic divergence.  As a good start, look for literature on the silverswords of Hawai'i:  Dubautia, Wilkesia, etc. 

Sorry, what is "species assignment"? Strictly this means deciding to which genus the species belongs. But the commoner problem is whether two populations belong to one species or two. Morphology remains relevant because (1) Often there are no molecular data (fossils, museum specimens). (2) Usually one can examine only a small fraction of the genome, jumping to conclusions about the unknown majority. (3) Sometimes morphology shows that the two populations simply cannot interbreed (organs or signals don't fit). But really, this is not a question where it's reasonable to replace "literature" with an "answer". Happy 2016, Yehudah

I mostly agree with Sir Yehudah Werner.

In my opinion, species is SUCCESSFUL result of interaction between GENOTYPE & ENVIRONMENT.

Morphological approach mainly deals with final product of the interaction between these two. But the Molecular approach deals with genetic materials only.

Both approaches are good.

Science doesn't have limitations, only human have limitation in ability to interpret Science.

For example, try to trace the development of morphological approach with development of more advanced and accurate microscopes and other accessories. You will find the inclusion of more characters for species determination through morphological approach. So it is human limitation and not the approach limitation.

I am working with Ground beetles and during study of papers of Dr. G. E. Ball of Canada, I realized the above mentioned development of Morphological approach.

So, the more characters like behavioural data, life history data and others, we include in Morphological approach, more will be explained for species validation and existence.

Molecular approach can add to Morphological approach but can not replace it.

Thank you,

Dear Asif,

firstly I would like to point out that in molecular studies, you study only fragments of DNA sequences (Locus) and not the whole genome.

Secondly, conclusion or results of molecular studies vary with numbers of loci one has studied. for example, the phylogenetic tree you construct using two molecular markers (say ITS and rbcl) will be entirely different from a tree constructed using 5 or more markers/loci.

Morphological characters are not manifestation of genes only.... environment also plays an important role... so molecular studies may be used to complement morphological studies. Therefore, morphological studies will always remain necessary.

At last, you can't publish new plant species solely based on molecular study.

Dear Danish,

You have stated: At last, you can't publish new plant species solely based on molecular study.

This is probably not correct. Kindly see the attached paper.

Best wishes,

Subir

Dr Subir Bandyopadhyay..

Thank  you for updating my concepts.

and your contributions to the Taxonomy, especially  Code (ICN) are admired and inspire me.

Hope we'll meet someday.

Regards.

Mohd. Danish Husain

Dear Asif,

morphology has played the main role in species identification just because vision is the main sense of our (human) species. Well, recognition of some species by their sound signals (as for birds and some insects) is still ok for us. If evolutionary history of humans would lead to a better development of our chemical sense, then maybe smell of urina for vertebrates or composition of epicuticular hydrocarbons for arthropods would be as important for species recognition as how the species looks like :)

We need to differentiate the variety of species in the nature conservation and monitoring because of differences in their roles and functions in our Biosphere and in particular ecosystem. Therefore, separation of species by their econiche would be probably an optimal solution. However, some knowledge about the econiche differentiation among related and similar species usually comes at the latest steps of their study. Stochastic neutral mutations in non-coding parts of genome (e.g. 3rd position of codons in the mtDNA or introns in the nDNA) provide us a proxy for early stages of species evolutionary differentiation, when ecosystem role of a "young" species has already changed but visual (morphological) differences have not yet appeared.

There are so many taxa, which representatives use chemical sense for recognition of mate and as well as for finding and using their specific econiche resources. In such cases, the morphology is naturally useless, and we deal with complexes of "cryptic" or "sibling" species, recognisable only by e.g. behavioural characters, like their smell, sound signals etc., which cannot be used for museum specimens. For such specimens, the molecular markers may be the only chance to be correctly identified.

Nevertheless, the morphology works well in animal taxa, which representatives use visual and tactile senses in recognition of mating partners (sexual selection on "visible" characters is working), or adaptation to their econiche requires some changes in species morphology. And if morphology works, it is still easier than sequencing - at least before a field micro-pocket-sequencer would appear in the market :)

Thank you for your responses, I hope this has been a good platform for discussion for all involved. 

Cheers

The shortest answer is yes, most biodiv monitoring is done based on morphology. If the work isn't basic taxonomic 'species discovery' (taxon definition and classification or systematics) then the ID work is largely morphological. But its highly taxon dependent. For fossils there is nothing besides morphology, and bacteria its the inverse. If there is an opportunity for molecular work, there needs to be a context to put it in, so there needs to have been a recent revision using molecular characters by a taxonomist doing basic research before it makes sense for an applied user (biodiv monitor) to consider generating molecular data.

In the end, molecular data is just another character set - sometimes its a magic bullet and sometimes it doesn't help much. But its still a lot more expensive to generate and analyse sequence data than to flip through a key, so morphology is usually the first approach.

 Is a molecular approach going to be the standard in the long term once we have access to larger fragments of the genome for comparison? I'm thinking a key advantage would be in cases of morphological mimicry? It also seems that at times morphological identification is not always objective with differing opinions between researchers as recently evidenced with quagga and zebra mussels. 

 In the  topic title  "species assignment' = a classification procedure of unidentified organism. It start with morphology tech (recognition in nature), and documented in the National collection or museum based on morphology structure.  Thus you cannot ignore morphology.

Both approaches are linked and dependent in an object (natural classification of organisms) but they are independent methodically, in a procedure. These two techniques veryfy each other as two independent morrors of the same beauty.

They filter each other, and suddenly old underestimated morphological  characters may float up as very important in phylogenetic modeling, or new genes may be unpredictably considered as "phylogenetically significant'.

In addition, genes do not stop changing and even in proteins the relatively stable 3D structure may have different gene and aminoacid base, thus demonstrating of the comparative stability of morphology in evolution.

 My answer to this would be  - Yes. Morphology is still the most important data available in the field to confirm your identification. Molecular data could be used as a confirmatory test to a certain your results from Morphology. It is practically nor possible to move with the molecular kits in the field and identify plants in the field.  

Dear Asif Laldin,

An example which could be interesting: according to the most up-to-date handbook of European Geometridae there are five species-complexes in which the members are barcode-sharing (e.g. Epirrhoe galiata-E. timozzaria) and species in further five complexes share barcodes occasionally, partially or regionally (e.g. Epirrita filigrammaria with E. autumnata). Furthermore, differential morphologic characters are clear and unambiguous.

With my best wishes,

Balázs Tóth 

Dear Asif,

It is always depends on subject you have taken for study. I personally feel Morphology remain to stay here, an expert can identify common species within no time, compare to time and money spent on molecular work.

However, molecular tools are helping in understanding many cryptic species in Insects which are difficult to identify using only morphological characters.

However, science is evolving we have to take what ever makes things simple.

With regards 

I suppose there would two schools of thought regarding that example you put forward Balazs?  You could argue that based on this that it is one species that has phenotypic plasticity? Is this where interpretation and bias comes into play?