Title : Modern taxonomic assessments should be based on poly-trait diagnostic approach, rather than only on molecular investigations
Abstract:
Since the time of Carolus Linnaeus, the concepts of identification of a species appear to have changed drastically on account of enormous progress in modern DNA based technological advancements. Most modern research workers are mainly dependent on comparative phylogenetics, chiefly elucidating resemblances and differences among chloroplast genes or plastomes among plants belonging to same and different genera and they have reshuffled old concept of classification and identification. This is indisputably accepted that plastomes or chloroplast genes (so also mitochondrial genes) are the most deeply conserved DNA sequences in the evolutionary journey and have been too less amenable for mutational changes. This is because chloroplasts did evolve from an ancient cyanobacterial endosymbiont more than 1.5 billion years ago. During subsequent evolutionary phases with the evolving nuclear genome, the chloroplast genome has remained independent, strongly reduced, with its own transcriptional machinery and distinct features, such as chloroplast-specific innovations in gene expression etc (eg.post-transcriptional processing). Most research publications these days are exclusively based on rbcL gene-complex comparative assessments and are revising the identifications of species and regrouping various taxa.
The present author however, has been advocating “Poly trait diagnostic Approach (Ptda)”. Significant point here is that any one approach cannot decide the exactness within the biological system. We must have polygenic system investigation procedure and that too must be of different loci; for this we will have to simultaneously work on morphological, anatomical and chromosomal variations along with plastome genes. Morphological studies have included external and internal details of plant parts as well as specific efforts concentrated on light microscopic and SEM studies on spore morphology. Chromosome variations in shape and size along with their movement in cell divisions and pairing behaviour during meiosis have been very informative. All these features are under control of many genes. On the basis of above multidisciplinary approaches (including assay of many rbcL genes) we have discovered twelve new taxa among pteridophytes. All five species of Ophioglossu L, five species of Isoetes L discovered during 1968-2023 are those whose specific individual traits are unique and unknown among related genera and species. Among all discoveries, the taxon Isoetes pantii Goswami & Arya is a classic taxon in the plant kingdom; this species has X-Y chromosome mechanism, possesses heterosporangia (male and female spores within a sporangium), and explicitly demonstrates DNA sequences resembling some sequences of human Y chromosome. Southern blot and DNA blasting studies have confirmed the present author’s earlier hypothesis that, ceaseless multiplications of DNA sequences since the time of origin of the cell, have been responsible for identical as well as random distribution of genes among trillions of cells before bisecting in to plant and animal cells sometime in the Early Cambrian. Identical to human Y chromosome MSY- DNA sequences have also been now known in the bryophyte Marchantia polymorpha.
Briefly, this presentation will also advise classical taxonomists and also molecular taxonomists that depending exclusively on one kind of investigation cannot be fully reliable for taxonomic inferences.
Audience Take Away:
Young research students must understand that there is nothing absolutely 100% correct in Biology. Variation is a rule rather than exception. The same species may have different cytotypes or different species may have the same chromosome number. Therefore this presentation will help them to get trained in “poly trait diagnostic approach (Ptda). This includes that an investigator must identify a species not only by morphological similarities abut also care for anatomical, chromosomal behavior during cell divisions, chromosome types and numbers and electron and light microscopic studies on spores or pollen structural details of wall layers. As and when possible, phylogenetic relationships by the comparative assessments of rbcL genes (chloroplast genes/plastomes) should also be attempted.
Following academic achievements are possible:
- Young students should get proper training on atleast three specialized areas
- Chances of getting a job as research scholars and or faculty at any institute will increase for those who practice on several disciplines in order to investigate on any plant species
- Outcome of Ptda investigations will be more authentic
- Not only publications but recognition of the published work as well as of investigators is equally important in science.
