Journal Number 99
May 2006

EDITORIAL

Various Contrivances by which New Zealand orchids are
fertilised by themselves
By Ian St George

Charles Darwin's Origin of species was published in 1859, and the first edition of his book on orchid fertilisation appeared in 1862. A second edition renamed The Various Contrivances by which Orchids are Fertilised by Insects appeared in 1904.

Darwin introduced the evolutionary concept of natural selection, the struggle of species against each other for survival.

He was a man of his times of course, as the great Darwin scholar Stephen Jay Gould pointed out: "[Darwin] imbibed the basic belief of the Scottish economists that theories of overall social structure must begin by analyzing the unconstrained actions of individuals."

Gould continued, "The theory of natural selection is a creative transfer to biology of Adam Smith's basic argument for a rational economy: the balance and order of nature does not arise from a higher, external (divine) control, or from the existence of laws operating directly upon the whole, but from struggle among individuals for their own benefits".

Adam Smith (1723-1790) was the great Scottish philosopher and economist who is best known for his book "The wealth of nations", which depicted economics as a struggle for existence - nature red in tooth and claw.
(Those were neither Smith's nor Darwin's words, but those of Alfred, Lord Tennyson, from his long 1850 poem In memoriam: "Who trusted God was love indeed / And love Creation's final law - / Tho' nature, red in tooth and claw / With ravine, shriek'd against his creed....").

Darwin hated the idea of self pollination. He wrote in the first edition of his orchid book, "It is hardly an exaggeration to say that Nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation." Despite observations that the British Bee orchid always self pollinated, he wrote in 1860, "...in other districts, or during particular seasons, it may be visited by insects...(and) would almost certainly receive the benefit of an occasional cross pollination".

He would not accept the evidence of his eyes.

You can trace a gradual softening of Darwin's stance on the subject, from incredulity bordering on disgust in the early 1860s that self pollination was even possible, through to acceptance fifteen years later that it happened, though obviously only when normal, healthy cross pollination by insects had somehow failed, and then only temporarily.

In the early seventies he would list the orchid species in which "self-fertilisation habitually occurs" but would add, "I believe that the few orchids which do not now intercross, either did formerly intercross, or that they will do so at some future period under different conditions, unless, indeed, they become extinct from the evil effects of long-continued close interbreeding."

I think he was again showing that he was a man of his times. Contemporary medical tomes use remarkably similar language to rail against masturbation - the habit of "self-pollution" or (tellingly) "the solitary vice" as it was called. JH Kellogg (yes, he of the cornflakes) published his Man the masterpiece in 1885, and in it listed 22 signs of "self abuse", and went on to say, "The human being who gives himself up to this sort of sinful indulgence, and abandons himself to the gratification of beastly lusts by this means, is likely to become, sooner or later, a complete wreck physically, mentally, and morally.... Undoubtedly the indulgence of this vile practice affords an ample explanation for the great number of puny, scrawny, weak-backed, lank-limbed, hollow-eyed, pale, sallow-faced boys who may always be seen upon the streets of any city".

With few exceptions, if pollination is to take place, the pollen from the male anther must come into contact with the female stigma. As with other flowers, insects may help orchids in this. Perhaps 97 percent of the world's orchids are indeed insect pollinated. But in New Zealand the position appears to be quite different. Many of our orchids are predominantly self pollinating, to some extent perhaps because of the few pollinating insects here.

Captain James Cook wrote in 1776, after his third visit to New Zealand, "Insects are very rare. Of these, we only saw two sorts of dragon-flies, some butterflies, small grass-hoppers, several sorts of spiders, some small black ants, and vast numbers of scorpion-flies (cicadas), with whose chirping the woods resound."

Brian Molloy compared the reported insect faunas of Australia and New Zealand and reached the same conclusion: paucity of insects is, at least to some extent, associated with self pollination.

By the Eocene epoch (54-38 million years ago) flowering plants and insects were diversifying rapidly. In Australia they formed the unique plant/insect pollination partnerships seen today, but even in insect-rich Australia many orchids retained or developed a fall-back position: they could self pollinate if no apt insect visited. Later dust-like orchid seed from Australia and SE Asia made effective landfall here, borne on the prevailing westerlies, sometimes accompanied by the necessary pollinating insects, and often showing structures or functions that had attracted insect pollinators in their homeland-scent, edible calli, nectar, or colour (see Table 1).

What really is special about the New Zealand orchids is the ability of the majority of them to self pollinate. Molloy estimated that in fact 60 percent of our orchids are predominantly self pollinating.

Some of our self pollinating species have been derived from insect pollinated ancestors, and they continue to inherit some of the characteristics that suggest insect pollination. These characteristics include many that Darwin observed (see Table 2).

We have often, in New Zealand, rather shamefacedly talked of the pale and "delicate beauty" of our orchids, which others have been cruel enough to call "inconspicuous". We don't have the masses of colour of a Swiss alpine meadow - but we do have masses of wild orchids, and we don't have to wear leather pants to keep the stinging insects at bay.

The disadvantages of self pollination may have been exaggerated, just as the evils of that other solitary activity were exaggerated. Neither now seems "abhorrent" or "unnatural". A dominant advantageous mutation is spread rapidly by cross fertilisation, but the self pollinator may be more likely to pass, for example, a new recessive character on to its offspring.

The uniformity of structure in self pollinating orchids in contemporary populations (exemplified, for instance, by their retention of rarely useful insect attracting characteristics) might suggest that such genetic change is uncommon.

Eventually Darwin did allow that self pollination may be a fallback position adopted by species that are normally insect pollinated. Even he admitted that self pollination was better than extinction.

This editorial covers some old ground, but signals a new department in the journal, where we will deal with how New Zealand orchid genera use cunning and ingenious means, less obtrusive perhaps, but no less marvellous, than those adopted by insect pollinated species, to achieve self pollination.
 

Table 1: The origins of the self pollinating New Zealand orchids

Table 2: Signs suggesting insect pollination and self pollination