Journal Number 98
February 2006

ORIGINAL PAPERS

Plant Names
By Graeme Jane

During my recent visit to Nelson I had some rigorous discussions with Mark Moorhouse over
the lack of stability in plant names, the concepts of species and genera. Then, when I arrived
home, I was confronted by an article by the Column impugning the names and abilities of early taxonomists in his article on C. alata.

There are perhaps two issues: the concept of species and genera, and the rules governing
acceptance of names. The second is the most straightforward and easiest to deal with.

Internationally recognised rules were established in 1935 as the International Code of Botanical
Nomenclature. This sets out the requirements for defining a name, including the identification
of a type, requirement for a Latin description and rules for deciding publication dates.

The basic unit of taxonomy is the species. Lower ranks tend to be used sparingly. Subspecies is used for taxa which are usually geographically separated and often have a different chromosome number. They are regarded as incipient species. Varieties are less commonly used and are regarded as minor variations which can readily interbreed with the main population. Forms are even less distinct and often represent only a single morphological difference.

At a higher level genera are regarded as groups of species which can be linked to a single ancestor (monophyletic). Some recent generic changes hinge on the point at which the common ancestor is recognised (often as represented in "tree form"). The question is sometimes whether one large genus is recognised or many smaller ones. The difficulty is usually that there is a core of very similar species and then a large number of smaller groups. Caladenia (in the broad sense) has over 250 species which can be subdivided into 13 genera, one of 150 species, one of 40, one of 20 and the largest of the rest is 9; or into 6 genera with 6 subgenera but still leaving several small genera.

The role of a flora, or a monograph on a genus or family, is to summarise the state of knowledge and to provide a uniform brush over disparate treatments within genera or families. The Index Kewensis or the Land-care plant names database (http://nzflora.landcareresearch.co.nz) also provide similar regularly updated, authoritative references. The orchid list published regularly in this journal and similar items also help to keep in touch with name changes arising from recent papers.
 

The Rule Book

The International Code of Botanical Nomenclature states:

The only proper reasons for changing a name are either a more profound knowledge of the facts resulting from adequate taxonomic study or the necessity of giving up a nomenclature that is contrary to the rules.

Some recent name changes have arisen because it was found that the name had been previously
used for another species (so a new name was needed) or the species was described earlier under
another name (Polystichum richardii now P. neozelandicum). This normally arises because of
accessibility of original descriptions (few copies printed or in languages other than English), the
way in which regional floras were compiled (some early NZ explorers were French or German),
and difficulties of communication and transport in the past.

Another key issue is that people such as Hooker and Cheeseman often did not identify a single
type specimen and frequently provided several sheets which illustrated their concepts of the
species by showing the range of variation. This becomes a significant issue when the concept
of the species is changed and narrowed.

In these cases a type may need to be chosen from several specimens to best represent what the original author of the name intended in his description eg. the type sheets of Coprosma parviflora var dumosa contain material of three species recognised today.

Occasionally the specimen identified as the type is shown to be a hybrid and so a long used name
is replaced by a new one (Olearia capillaris now O. quinquevulnera). All these circumstances are covered by the rules.  

Species Concept

What constitutes as species? When do we know we have a different genus, species, sub-species, variety or forma? Some of these questions were explored by Ian St George and Oliver Sparrow (courtesy of David McConachie) in issue 93 of the Journal. Ian set out the techniques used to investigate plant populations and explore variation while Sparrow explained some of the analytical processes involved building the concept of a species / taxon.

Another recent source of material for the discussion is that of Hopper and Brown (2001).
They make several key statements:

Thus taxonomic works should aim for stability, using validly published names consistent with scientific understanding wherever possible. To do otherwise is to indulge in the `useless creation of names', which the ICBN specifically seeks to avoid.

In relation to the Caladenia debate they state:

With independent agreement reached on pertinent phylogenetic relationships by leading
contemporary workers, this issue of rank is no longer a scientific question. Rather, it is one
for informed choice after careful assessment of relevant evidence and argument

and

Indeed, arguably the plethora of new generic names would obscure relationships, leading to a
less predictive classification in the hands of most non specialists. In such circumstances, in
our view, nomenclatural stability emerges as a most important consideration

and

history will be the final arbiter on such vexing questions of rank.... The acid test of acceptability
to the wider botanical community has not occurred.

What they are saying in effect is that no matter what the science involved shows, the ultimate test of changes to generic or specific names is what the wider community is willing to accept and adopt and this can change over time as techniques change and methods of investigation evolve.
 

Caladenia alata

Getting back to Caladenia alata, many of Scanlen's assumptions are at best provocative. There is
a wide difference in species concept between Colenso, who regarded minor plant variations as species, and contemporaries such as Hooker and Cheeseman who often adopted broader concepts of species. In his lifetime, Colenso described a large number of species many of which were not accepted by later authors, not even today. On the other hand recent authors have examined some Hooker or Cheeseman species and defined several new species. One of these is C. minor.

In the 19th century there were no firm rules on names, or procedures for describing species. Acceptance of names depended on reputation and ability to communicate through dispersal of journals and personal contacts. A name is often cited with a name (or initials) following and sometimes a date to signify whose concept is being followed. Hence C. alata Hook. f. 1853 is different from C. alata R.Br 1810. The first is that described by Hooker in the Flora of Tasmania, the latter that described by Robert Brown in his Prodromus. The first is illegitimate as the latter has precedence but can still be used when talking about the two descriptions. In these cases "C. alata Hook.f. 1853 non R.Br. 1810" may be used to identify what Hooker described from Tasmania.

Caladenia minor is based on 22 specimens and a drawing, possibly derived from a spirit specimen that was dissected. The earliest compiled sheet has 4 specimens three of which are C. alata. Hooker in his type description emphasises that C. minor is pink. Examination of the type specimens by Clements in 1987 showed that the open flowers are assignable to C. alata, the remaining buds are probably indeterminate. No specimens matched the Fitch drawing. No widespread plants have a pink flower like that of Fitch's drawing although Colenso's C. variegata may approach it. As Ian St George in 2002 states, C. minor may merely be a later name for C. alata (or an earlier one for C. exigua?).

Caladenia alata is based on plants collected in Sydney. The type description makes no reference to colour, although it emphasises the pointed tepals and few lateral calli. Hooker in preparing his flora of Tasmania (1855) used the name C. alata but was unsure whether it sufficiently fitted Brown's description. Fitch's drawing was not of C. alata as we now know it. By 1902 Curtis, in revising the Tasmania Flora, had assigned C. alata to C. carnea. Until 1987 (and even now) C. carnea was regarded as a very variable species encompassing many varieties with var. alata as but one.

The key to the long history in establishing the name C. alata was identifying the specimen that Brown had used to describe his C. alata and describing it in detail. Until 1935 there was no requirement to define or identify a single type specimen. It was only detailed detective work by Jones and Clements in 1984-87 that identified and typified C. alata and C. minor. With this in mind Scanlen's observations provoke comment.

Hooker obviously adopted a broad definition for his Caladenia minor such that it included C. alata. Hence Hooker's description of C. minor was not "erroneous" but reflected a different, broader species concept as applied to New Zealand specimens.

Cheeseman did not "miss the Robert Brown connection". He was describing plants, from New
Zealand, as C. minor var. exigua that fitted Hooker's pink C. minor but had acute tepals. The
Australians had already subsumed C. alata into C. carnea. Also, Brown's description of C. alata
was inadequate to distinguish the species from similar small Caladenias in Australia, such as
C. aurantiaca and, the types were lost in the vast collections at the British Museum (as they often are at Kew) at a time when travel was difficult. And perhaps thirdly he may have assumed that the Tasman sea was a barrier to species dispersal, as many later authors did till the 1940's.

Domin's 1915 inclusion of C. alata in C. carnea was not "a misclassification" - it again was application of a particular species concept to the two taxa, following earlier authors. He did not "miss the C. alata connection" he chose to follow earlier authors and adopt a broad species concept.

Hatch 1945 was not uneasy with the Rupp/ Domin arrangement he was merely stating that the
current state of knowledge was inadequate to assign the varieties in C. carnea into separate
species. Brown did not "at least get into the citation"; Hatch was using the proper attribution of
the name C. carnea.

Rupp's description of C. holmesii merely reflected the poor understanding of C. alata at the time not a mistake on Hooker's part. He was not classifying C. alata as C. holmseii, he was describing plants from Wyong (near Sydney).

Moore and Edgar 1970 followed Rupp and adopted a wider definition but acknowledged the state of knowledge at the time, specifically by stating (as the floras often do) "no critical description of the type of the species (C. carnea) has been seen". It was not "mis-classified," as C. carnea, the authors merely provided the best knowledge available at the time.

Curtis (1979) did not just 'state a "comb nov.",' she had a different concept of the Caladenias

in Australia and transferred the New Zealand species (as varieties) to C. catenata. Brown was not
cut out of the game - the name, C. alata R.Br. was not being affected here. It was the New Zealand
C. exigua that was relegated to variety, consistent with the state of knowledge at the time.

The specific name to which the variety exigua, was attached (C. catenata) was established by Smith in 1804 under a different genus (Arethusa) which was later transferred to Caladenia by Druce - hence C. catenata (Sm) Druce (ie the definition of the species to be used is that of Smith,1804 and his type specimen applies).

C. exigua has not been dumped. At present the type specimen as identified and typified by
Clements is regarded as being similar to that of C. alata R.Br 1910. non Hook.f. 1854, and since
C. alata is an earlier name that takes precedence. If at some later date someone decides the differences are sufficient, the name C. exigua Hook.f, could be available for that taxon at a species, subspecies, variety or form level. However C. minor may also take precedence (St George 2002).

In summary we have two parallel paths, one in Australia for C. alata and, one in New Zealand for
C. minor (that is well set out by Ian St George in 2002) that later become joined: