An Orchidist's Miscellany

 ORCHID DISTRIBUTION

 Orchids of one type or another are found near the limits of vegetation. They are found from northern Sweden and Alaska, and south to Tierra del Fuego and Macquarrie Island. Very few vascular plants are found further north or south. The terrestrials have the widest distribution, being mainly limited to the tropical and subtropical environments. The only median area where they are absent is the extreme desert environments, although even here some can be found in sheltered desert canyons and oases, and in cactus thorn scrub habitats.

Like some other plant groups, orchids are more diverse in the tropical belt than at the higher latitudes. Studies reported by Dresler have shown that orchids are most abundant and diverse in habitats receiving over 2500 mm of rainfall ( 1 00 inches) per annum, where no month receives less than 50 - 75 mm (2 - 3 inches). Extremely wet or dry habitats contain few species. Dew or cloud condensation is important in some otherwise 'dry' habitats.

In Central America, the greatest abundance and diversity of orchids is found in the wet montane forest or cloud forest from 1000 - 2000 metres in elevation (3300 - 6600 feet). A similar situation exists in the South American Andes, although the orchid-rich zone is somewhat higher.

One striking aspect of orchid distribution is that the different continents have distinctive orchid flora .suggesting that a large part of orchid evolution occurred since the continents became well separated. It is interesting to see the total number of genera and species of the world's main geographic regions, as assessed by Robert Dresler:

AREA GENERA SPECIES
North America 26 153
Tropical America . 306 8266
Tropical Africa 134 3131
Eurasia 49 664
Tropical Asia 250 6800
Australasia 68 602

If you wish to see different species of orchids, there are obvious areas where you should go to see the greatest number!


Site established 9th May 1998