Ruby Cruster

The ruby cruster split from the tundra gemshrub line with a double sap gene mutation. The original progenitor of the ruby cruster developed a freak mutation causing it to shed particles of calcite along with its sap. Over the course of the cruster's life, the calcite continues to accrue, forming hard slopes around the stem. Whilst the crown of the flora is still edible by predators, the stem and root structure remain protected by the calcite mound. In the tundra, where the soil is red, contamination will often give the calcite a rusty colouration as well.

As the stem/root structure are not consumed, it is not uncommon for a single cruster to 'fruit' many times with edible spore bodies. The problem comes when it finally dies, as the calcite shell will remain until it is crushed by passing fauna to a fine enough degree to be consumed by microbes. As the secondary method of reproduction involves new crusters sprouting from an extended root network, this can lead ultimately to rings of living crusters around a circle of dead shells, waiting for large polar fauna to crush them and return the calcium to the soil.

Biochemestry
Duplications are one of the more common genetic mutations, along with deletions and substitutions. Normally this happens on the level of single base pairs in the DNA code, but sometimes agents such as transposons can duplicate entire sequences at once. This may have no effect, may destroy the function of the gene being coded for, may result in overproduction of a gene product, or in the case of certain signalling chemicals may cause duplication of an entire body segment (additional legs, for example). The latter case is very rare indeed, as not only do genes code for chemistry rather than design, but if they aren't killed by their parent at birth such additional body parts are almost always a terrible hardship and will probably select against their line.

In the case of the progenitor of P. calcifurm, a duplicated sequence for sap generation caused sap overproduction in the line. This mostly led to additional sap seeping out of the tundra gemshrub's skin and collecting at the base. The sap would eventually dry out and flake away in the cold. This would have been the end of the story of another, somewhat ordinary subspecies of P. polarus, had there not been a second mutation.

Into the secondary sap gene sequence was transposed an initially random and ineffective sequence, giving rise to a non-viable protein. Over time and generations, the non-viable protein changed until it was able to catalyse the production of calcite from calcium ions and carbon in its body. Small particles of calcite were secreted with the sap from the first P. calcifurm, accreting at the base of the organism's stem until eventually building up into a dirt-laced calcite cone.

Because the secondary sap gene sequence was modified, the original antifreeze function was preserved - a modification which would otherwise have spelled an end to this fledgeling species.