The Code does not give any ruling on individual's taxonomic judgement

Taxonomy in general is approached to facilitate scientific discourse. Taxonomy by morphology is inherently uncertain due to the variation normally expressed by organisms. This is the case when trying to delimit organisms with very similar characteristics, such as on species-level. This is especially difficult when trying to perform the same assessment on similar species that hybridize. Alternatives to this practice is to instead utilize taxonomy by genomic typing. This would allow for a different way of asserting evolutionary relationships between species.

Code never deals with taxonomy, it is for nomenclature, typification and other related issues. The question is out of the purview of ICN. I was concerned about the inconsistency prevailing in assigning generic ranks or merging/ splitting of genera. It is agreeable that morphology alone may be insufficient in many cases to pass a judgement. But where is the end??? Every day there are merger and splitting of genera with a bunch full of new combinations. The same people contradicting their own earlier concept and this goes on....

It is unclear if it will ever be possible to calibrate the "taxonomic distance" corresponding to variety, subspecies, species, genus, etc. I would think it depends on the group you are working with. In some genera, different species (or evolutionary units accepted as species by specialists) show very subtle morphological and genetic divergence, while in other groups, extensive within species variation is the rule, and, accordingly, much larger divergence is required for different groups to be accepted as different species... I would think that it is the most important part of the taxonomist's job, i.e. to calibrate the scale of divergence corresponding to different species in his/her study group...

This is a very old question. Only an experienced taxonomist expertising on a particular group can give a sound judgement on delimitation! From numerical taxonomy, through cladistics we are now in the era of molecular phylogenetics. Therefore, the conclusions on morphological (both external and internal) should now be corroborated with molecular studies. As you say, the delimiting characters vary from group to group, e.g. a single inflorescence type delimits the family Compositae but a combination of characters determine some others. As I said, only an expert/monographer rather than a random taxonomist/floristics worker can give a sound judgement. Moreover, you cannot standardize the taxonomic characters through mathematical formulae and statistical analysis and apply them for delimitation for stabilizing the nomenclature. You must depend on expert opinion only for delimitation of genera and infrageneric taxa.

Observation of detailed morphology and the variation with in the population for a considerable time period, taxonomists delineate the species, varities or subspecies. To Deliniate the species with in the genus the literature pertaining the identifying keys, and diagnostic characters of all the species with in the genus are required.With the literature thoroughness, comparison of diagnostic characters helps to delineate the species.

Taxonomy is a science that will always be under construction. The genus groups the species related to each other. But here are two problems: 1. The concept of species. Concept yet to be reached unanimity among scientists. 2.- To what extent can the proximity or relationship between species be quantified? All are doubts but taxonomy science should not stop.

A new definition of a genus may be had empirically. If an evolutionary diagram shows that there are two or more descendant species from a single progenitor species, then it is an evolution-based genus. Check out the "dissilient genus" concept in my recent papers on macroevolutionary systematics.

For this problem to be solved, it is required to conduct future revisionary or monographic project by forming group of experts (Eg. Globar Carex Group). Because individual perception always tends to be biased, and many times emotional sentiments of the worker is attached with that plant group, which leads to creation of his own perception. When worked on collective and larger scale there may be chances to reduce this individual perceptional error.

In my perception, there is no such threshold level for delimitation of plant taxa, however it depends on keen observation of particular plant group by a true experienced taxonomist in that plant group.

It is not based on individual perception, there are rules for that based on shared ancestry, looking at the morphology and molecular data

There are large number of tools for identification of plants such morphology, cytology, palynology, phytochemistry, molecular biology etc.

If we sure at morphological level of identification of species then we failure at chromosome number or pollen morphology.

If we differentiate two plants based chromosome number, but these plants are not a two species, they are two cytotype of one species.

Molecular tool is successful in microorganisms, but it totally change the traditional set of nemenclature of all plant groups.

Some new families, generas are developed. Some plants considered under new family etc.

For example previously, botanical name of Amla was Emblica officinarum belongs to family Euphorbiaceae. But now it considered as Phyllanthus Emblica under Phyllanthaceae family acc. to molecular taxonomy.

Origin of angiosperms are abominable mystery.

So every tool have it's own importance.

Thank u.

The threshold level for delimitation of taxa is purely based on the character weight and it may vary in accordance with the groups. So we cant assign a stipulated range for the delimitation. only the experts can be done it.

To affirm standards to the limits of genera of plant species is not possible. There are several reasons for the such as follows,

•Every species (genetically supported) differs from its close allies with some or great morphological distance.

•If we standardise generic threshold, it should certainly imbalance whole scenario.

•As different taxa have different evolutionary response and origin their generic limits are constantly changing on a minute scale.

To determine a criteria for a generic limit is not at all useful. We do not even know what are species forget about the genus. What is certain is that we have individuals exhibiting varying degrees of evolutionary changes in the form of characters.

Precarious observation only matters and there are no such threshold for delimiting plant genus because each species are having some distinguished morphology.

Sure. There is an empriically defined higher category than species. It is the monothetic genus. This is a set of species are of which possess all the traits that the ancestor of them obtained as new, plus some new traits based on old ancestral traits. My recent papers call this a "dissilient" genus because it explodes from the ancestral species with new adaptations.