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All living organisms exhibit variation and Australian orchids are no exception. Variation that occurs between different species within a genus is to be expected but the variation exhibited within a species can be very surprising when encountered for the first time. The following examples illustrate different variation within a species.
Minor Variation: Orchid species that reproduce from seed exhibit variation such that no two specimens are exactly alike. The attached image of Arachnorchis gardneri shows three flowers collected from a single locality at Broke Inlet in Western Australia. The flowers show minor variation in the colouration of the labellum and patterns of colour on the columns as well as some variation in the number and arrangement of labellum calli and marginal teeth. The second image shows minor colour variation in two specimens of Thelymitra macrophylla growing together at Lake Seppings in Western Australia.
Variation within Diuris: An excellent example is the genus Diuris where species frequently exhibit a tremendous range of variation, particularly in flower colour and floral markings. This variation is commonly exhibited by plants growing in close proximity within a population and can create confusion for people trying to identify the species involved. For this genus, identification must be based on the population as a whole, not on individual plants. The probable reason for Diuris being so variable is that they attract pollinating insects by deceit (no food reward) and the variability of floral colour and markings within a population interferes with the ability of the insects to learn to avoid particular floral patterns.
Variation within Sarcochilus falcatus: Widely distributed species often exhibit significant variation when populations are examined throughout their range. Sarcochilus falcatus is distributed from northern Queensland to eastern Victoria and this gallery of images, taken by Ron Tunstall, exhibits the sort of variation that occurs in a widespread species. Within its range, S. falcatus is distributed from the coastal lowlands to the ranges and tablelands at about 1400 m altitude and occurs in a diversity of habitats. Little variation is exhibited by the species in vegetative features and plants can be readily recognized, even when not in flower, by their leathery falcate leaves. The flowers however, exhibit considerable variation in size, width of the perianth segments, length of the labellum lateral lobes and the pattern of colours on the labellum. They also have a considerable range of floral perfumes. These variations suggest that a detailed morphological and molecular study of populations of S. falcatus throughout its range could yield some interesting results as to its genetic makeup and could also provide important information for the conservation of significant variants that may need to be recognised at some formal taxonomic rank.
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Variation within Calochilus campestris: The gallery of images of this species, taken by Ron Tunstall, shows the floral variation that occurs over its distribution within Queensland, New South Wales, Victoria and South Australia. The flowers are basically self-pollinating but also attract male scoliid wasps by sexual deceit. As well as floral variation, this species also exhibits variation in vegetative features, particularly the development of its leaf and sterile bracts. Its range extends from the coastal lowlands to montane habitats. Because of the patterns of floral and vegetative variation exhibited and the pollination system involved, several new taxa will probably be segregated from within C. campestris and recognized at species rank.
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