Look Again

Euphorbaceae and Cactaceae

let’s think about two plant families
Euphorbaceae
and Cactaceae
there are some plants in these groups
that would be tough to place in either family just by looking at them
to the trained observer
a cactus is a cactus
but to an unsuspecting passerby
what they think is a cactus may actually belong in Euphorbaceae
both euphorbes and cacti are generally fleshy
drought resistant
occasionally spiky
but cacti are found in North and South America
while many cactus like Euphorbes are found in Africa

*This is a cactus (Photo by Jeff Gauld)*

how did this happen?
why do these two geographically disjunct plant groups look so similar?
it’s because of convergent evolution
if a plant population sprouted up in Chile
and one in Algeria
and then millions of years of evolution happened
you would get some similarities between the two populations because of climate
both the Sahara and Atacama deserts are pretty dry places
they have a very low average rainfall
and are not conducive to a large amount of plant growth
the plant populations in those areas were subject to similar climatic conditions
over a very long period of time
and through a variety of evolutionary processes
the plant populations came to consist of organisms that had similar adaptations as a result of the similar climates

There you have it. The lack of water and soil nutrients put selective pressure on these plant populations, pushing them toward the same end and here we are today, with two very similar looking clades. It seems like an obvious phenomenon, doesn’t it? But perhaps that’s because we’re not the ones who had to do years and years of specimen collection, geological analysis, and evolutionary comparison research to determine that Cactaceae and Euphorbaceae are in fact not related linneages.

Hindsight is 20/20.