Journal Number 98
February 2006

ORIGINAL PAPERS

Observations on the Nelson Corybas alliance
By Mark Moorhouse

Corybas (Nematoceras) trilobus

Something that has interested me for a number of years is the variation one can observe in colonies of Corybas trilobus. It's not surprising to find variation, after all it has long been known as "a variable species" with various textbooks commenting on "different forms", or "containing several taxa".

What has been more enigmatic, at least to me, is why? Recent observations and some enlightening discussions with Dr Graeme Jane, have shed some light on this matter.

To understand the Why? one must look carefully at the How? That is, how the plant reproduces itself. A high percentage of C. trilobus colonies that one observes have sourced from a single seed striking favorable ground, in some cases centuries back. After the original seed grew the chief form of reproduction became vegetative propagation, through its tubers, effectively producing perfect clones of its original genetic makeup. So, zero variation within a single colony would be what one could expect to find and usually this is the case. Because each colony sources from a single seed strike, often decades or even centuries apart and thus likely from varying parent colonies, variation could be expected from colony to colony, but this is not always the case. Often flowers are self pollinating or a pollinator enters one clone plant and fertilises another in the same colony. The result of a clone "selfing" or crossing with a clone has still got to be the same clone as no new genetic material has been introduced.

Things become interesting, however, when one locates a patch of favorable ground harbouring two intermingled, but separate, clone colonies. This season, in company with Georgina Upson and Dr Jane, I was fortunate enough to spend a little time observing a classic example of this, in the Clarke Valley. Here were two colonies, one with the so called subalpine green form of C. trilobus, the other with a dark red-black flower very closely approaching C. "darkie" of Dip Flat, both colonies flowering simultaneously and quite intermixed. No obvious differences in the leaves presented themselves, though both demonstrated the straight-side leaf syndrome on flowering plants.

After a careful search of the entire patch, during which we discussed the likelihood of "halfway
house" flowers, we came up empty handed. There were none, but it was mooted that we should
be likely to find such a colony in the near vicinity and sure enough, less than 80 metres away,
Dr Jane located just such a colony. These plants showed some characteristics of both the original colonies, and had flowers approaching what I understand to be C. "Trotters" in colouration. Other colonies in the near vicinity will no doubt show other variations we have become accustomed to seeing because each sources from a separate seed, either from inter-colony crosses or intra-colony clones. The argument was beginning to gain some credibility. Nearby the stream banks abound with C. "whiskers", and C. acuminatus also still in flower.

Further extrapolation of this concept raises some other interesting possibilities. If one could somehow produce a figure which represents the rate of vegetative cloning, one might be able to calculate the age of a colony within a decade or two by doing a head count over a few seasons.

Do huge colonies actually represent a single seed that struck, say, one century ago? 500 yrs
ago? 1 or 2 thousand years ago? Still a perfect clone of the original, whilst on a ridge a few
hundred metres away where fungus gnats abound, a colony of just five plants might represent
the result of 50 cross pollinations during the same time period. Two colonies close together,
one with unchanged genetics for 2 millennia, the other modified every couple of decades, both
C. trilobus.

This raises a new concept.
 

A 2000 yr old Corybas - Is it possible?

The simple answer is yes, and probably not too uncommon. But you might argue, they grow, flower and die each year, how can you suggest they are actually 2000 years old, only a few trees like our Kauri live to this sort of age.

Briefly consider a deciduous tree, an oak for example, would you say it dies each year when the leaves fall off in winter? Of course not, it's just dormant. So too is the Corybas when it dies down. It is quite alive down in the ground in the form of a dormant tuber. But the new tuber is a new plant you may argue. Is it? The genetic makeup has not altered. Reconsider the oak. Are you suggesting that if we cut off all the limbs whilst it is dormant, the new sprout it grows from the trunk in spring is a new plant? No-one would argue this way.

So having established that Corybas do not die each year consider this. It should be possible to walk out into the forest and locate a colony of say Corybas trilobus perhaps a large one, and quite correctly conclude that you are looking at a plant which through vegetative propagation has remained alive and genetically unchanged for maybe 2000 years.

It would be true to say that likely, the colony's flowers have been pollinated, cross-pollinated and/or selfed almost every season, and literally billions of seeds have been dispersed from the resulting capsules, but this did not affect the genetic makeup of the original plant, did it? It only affected the offspring that grew from its seeds when they found favourable ground.

In light of this, it is not difficult to perceive how the observer might be persuaded to conclude that two colonies, looking a bit different from each other, are two separate species, or at least vars, and no doubt, given enough points of difference, it might convince the taxonomists too, and yet they are in fact the same species. A variable one. After all a five year old child and a centenarian probably demonstrate enough points of difference to warrant being called different species to the not so astute observer don't you think?
 

Corybas "Trotters"

Something which I have personally observed in connection with C. "Trotters" in the Nelson area
is that it only occurs locally where one of the C. rivularis alliance is present in company with
C. trilobus. Almost always, it is C. "Whiskers" and I can cite a number of instances where I have found C. "Trotters" and C. trilobus in an area and later discovered, or purposely searched successfully for, C. "Whiskers", or conversely, found both C. trilobus and C. "Whiskers" and successfully searched to find C. "Trotters".

In the light of recent articles published on the hybridising habits of various Corybas species and clear documentation of hybrid Corybas swarms by Bruce Irwin, and Dr Graeme Jane [pers. com.] the above association of species may suggest parents for C. "Trotters".

The writer would very much appreciate feed back on this observation, preferably printed in the pages of this magazine so that all can share it. Perhaps it is only a local phenomenon.
 

Corybas cheesemanii

On 22 October, my daughter Kendyll Levy emailed me saying she had C. cheesemanii in flower. Of course I raised my eyebrows, it was two months out of season, and I requested a photo. She sent several showing a normal looking flower, but I noted that it showed no signs of the vestigial tepals above the horns a variation worth jotting down. It also demonstrated to me the need to check those seed heads when identifying C. cheesemanii from the scarcer Molloybas cryptanthus, especially when using the time of seeding as the identifying factor. I confess to having been caught out myself.
 

Molloybas cryptanthus

Thanks to just such careful observation alluded to above, and subsequent vigilant inspections by Georgina Upson, she was able to show Dr Jane and myself some Molloybas in flower on 22 October on her property in the Baton Valley, Nelson. A first record for the E.R. [46.07] I believe. Interestingly, although the plants were clearly M cryptanthus some aspects were notably at variance with written descriptions, particularly the length of the dorsal sepal, which was linear [parallel sided] and acute, exceeding the fimbriate labellum in length by almost 10 mm on one plant. The colony was in pure Nothofagus leaf litter only a few metres from the forest fringe.

This discovery and the new additions of Stegostyla atradenia, Caladenia bartlettii, and Corybas macranthus now brings the total species found on the Upson's property to over 40, a veritable orchid lover's paradise.