In Tasmanian botany I was taught the concept of a cline, where a plant species seems to metamorphose into another species along an environmental gradient. In other words, what is considered a plant species at one end of a environmental continuum (eg, the base of a mountain) shows continuous morphological variation and seems to become another species as one goes up a mountain.
The most quoted and classical example of this would be that of the eucalypts, where you might see the Yellow Gum (Eucalyptus johnstonii) grading into the Alpine Yellow Gum (Eucalyptus subcrenulata), which grades into the Varnished Gum (Eucalyptus vernicosa) along some mountains in Tasmania.
I have often wondered how the concept of clinal variation might apply to other Tasmanian plants.
An example I had in mind was of the Tasmanian Everlastingbushes (Ozothamnus spp.).
In particular, the high altitude Sticky everlastingbush (Ozothamnus antennaria), Alpine everlastingbush (O. rodwayi) and Mountain everlastingbush (O. ledifolius) seem to exhibit morphological features that makes it easy to imagine that these species somehow evolved from one to the other or graded from one to the other along some sort of a environmental gradient.
It is easy to imagine the leaves of O. antennaria (which grows at slightly lower altitudes from it’s two relatives) becoming smaller and the flower heads getting more compact until it becomes something like O. ledifolius, the morphology of O. rodwayi being intermediate.
Not sure if this betrays any relationships: O. ledifolius smells vaguely of cinnamon spice and O. rodwayi seems to have a similar, albeit fainter smell. O. antennaria has the faintest smell last I took a sniff.
In any case, the idea of a cline in the everlastingbushes could be fallacious. But afterall, all good science starts with a conjecture, insane as it may seem. It would really be an interesting hypothesis to test using molecular methods, wouldn’t it.