Hosta
systematics

Introduction to systematics

I'm by no means an expert on systematics, not even a well informed amateur, but for people like me, with a deep interest in the species, some base knowledge on plant systematics is essential.

So, here it is ...

Some basic terminology

Nomenclature

All species of plants are given an official name by man.
This name allows us to communicate on an plant species, and gives us certainty we're talking about the same plant.

The founder of the nomenclature as we know it today is Linnaeus.  He introduced the binominal nomenclature (genus name + species name).

Classification

Besides an accepted way to identify a plant by its unique name, it is of great importance to have a classification system, in which a species is a member of a group, and the group tells us (or predicts) something on what the species will look like. This makes it possible to identify e.g. a new hosta species as a hosta, even if it hasn't been given a name yet.  It also provides a way to keep the description of individual species short, since there is no need to repeat the group characteristics with every species.

In this field, Linnaeus also was the pioneer, but we've left the Linnaean systematics behind us since.  He thought all occurring species are created as they are now.  It's only since the days of Charles Darwin and his evolution theory the idea was born that species are the result of a continuous evolution.  Ever since, mankind has tried to order species according to the extend of their relationship.

Taxonomy

In a strict sense, taxonomy is the occupation (and the result) of describing, naming en classifying of taxa (species, genera en higher ranking groups)

Systematics

Systematics covers a broader field than taxonomy and is not only about classification, but also involves the study of relationships between populations, species and higher ranked taxa. The study of biodiversity also is part of systematics.

Phylogenetic systematics

Phylogenetic systematics' goal is to generate, through the study of relationships, a tree (phylogeny) that shows the evolutionary relationships, based on a number of plant characteristics.  The type of plant characteristics that are studied in order to define relationships also evolves, because more new research techniques are being developed all the time.  Where research used to be solely based on morphology, researchers nowadays often use genetic characteristics.

Hostas, systematics and taxonomy

Taxonomy and systematics are human activities, by different people with different views.  They aren't exact sciences, no matter how hard scientists try to tell us the opposite.  And hostas in particular make matters only more complicated through their genetic instability.  They don't worry about systematics en taxonomy: they just grow, and often are very hard to fit into any human classification system.

Therefore it's quite normal, and to be expected, that different researchers come to different conclusions based on the same data, the same plants.  Why ?

  • Not all data are known, and researchers have to make suppositions. 
    An example: about some plants is said they are presumably of garden origin.  On the other hand, it's possible they originated in the wild and were introduced in garden culture a long time ago.

  • Results of research need to be interpreted.  Different people tend to interpret the same results differently, leading to different conclusions.

  • A different view on systematics. 
    Example: one researcher prefers the number of species as limited as possible, and applies a rigorous definition of the notion "species".  Purely theoretical this could, as far as the genus is concerned, lead to the conclusion there is only one species.  
    Other researchers apply a less restrictive definition of what a species is, but still their definition doesn't have to be the same. 
    In this context it is impossible to define which solution is 'right' or 'wrong'.  They are just different solutions.  The scientific world can come to a consensus of what is adopted as the preferable solution.

  • Human pride:  researchers are only human, with their human shortcomings.  When, after years of studying hostas, a researcher comes to his own taxonomic conclusions, it's only normal that he would like the international community to accept his conclusions as 'the truth', and see his name attached to the plants he studied forever. 

Which systematics view is the best ?

With my limited knowledge of taxonomy and systematics it would be rather presumptuous for me to be the judge of this.

All I need is that information on a systematics solution is freely available on the internet and generally accepted.
For those reasons alone, I stick to the system by Georg W. Schmid, which is a bit outdated (but it's being revised as I write this).

The systematics by B. Zonneveld et al probably are scientifically more up to date, but it's harder to find generally available information on the web, and it isn't broadly accepted. 

Furthermore, Mr. Zonneveld is what I call a lumper, banning a lot of the old names into synonymy, as where Mr. Schmid is more a splitter, retaining more species, varieties and forms in his system.
From a horticultural point of view, I consider the splitter view more interesting.

As my interests in hosta are primarily horticultural, I want to be able to make a distinction between plants from different populations in the wild, regardless whether they belong to the same species or not.