Thursday, August 19, 2021

The Amazing Evolution of the Monkey Tail Cactus

These pictures show a plant known as the Monkey Tail Cactus, Cleistocactus colademononis. It lives on cliffs in Peru and Bolivia and has become highly adapted to the cliff habitat.

The most notable thing you can see about the Monkey Tail Cactus is that it hangs down. It actually grows downwards. This is odd because most plants exhibit positive phototropism and negative gravitropism, meaning they grow towards light and against gravity.  These are fundamental factors for the survival of most plants as they seek to grow upwards towards their only source of energy, the sun.

So think of the evolution of plant growth regulation that was needed to make a plant grow away from the light and following gravity. The genus Cleistocactus are generally tall, thin, upright growing cactuses. However, it must have been a terrible disadvantage for a tall thin cactus to grow upwards on a cliff with only small root space and poor footing. Such a disadvantage in fact, that most early cactus colonizers of cliffs fell over and did not succeed in this new habitat.  Over time however a few plants were less inclined to grow upwards and so natural selection was towards plants that grew downwards. 

Eventually however, if they kept growing downwards, they would all end up at the bottom of the cliff. So they developed flowers, fruits, and seeds favored by birds, so the birds would carry their seeds upwards and start new generations of the cactus further up the cliff.

- Dave


A new acquisition at the botanic garden, the Tassel Fern, Huperzia squarrosa

A new acquisition at the botanic garden, the Tassel Fern, Huperzia squarrosa (aka Phlegmariurus squarrosus, Lycopodium squarrosum). It doesn't look anything like the fronds of a fern. In fact it's a living fossil that sits somewhere between a moss and a fern, and first appeared on Earth about 380 million years ago during the Devonian period. This was a time long before the dinosaurs, known as the Age of Fishes, when the sea was dominated by jawless and armored fishes, when the first primitive sharks evolved, and the first lobe-finned fishes began to haul themselves onto tidal flats to become the first land vertebrates. This was a time that marked the first extensive colonization of the land by plants, and without any large land-dwelling herbivores, they thrived.

Don't ask me how much this thing cost, or how long it took me to find one, too much and too long, but I think it's a worthy addition to the botanic garden.

- Dave