Prahlada Papper (Ph.D.)

Broccoli ain't a tree!
Prahlada’s CV

I wonder about oaks.

In California, the white oak section (Quercus sensu stricto) seems to do a whole lot of pretty crazy stuff. For example: the California scrub oaks complex (Q. berberidifolia and friends, about 6 species in total), which are apparently very closely related to blue oak (Q. douglasii), are a chaparrally kind of bunch of shrubs that you can find most places in California from the coast to the desert up to mid-elevations, including spots with serpentine and other tough soils. Similarly, there’s two shrubby subspecies of Oregon white oak (Q. garryana ssp. breweri and ssp. semota) that are found across far Northern California and scattered through the Sierra Nevada in chaparral communities at mid- and high-elevations, often on sites with poor soil. Black oaks (Q. kelloggii), canyon oak (Q. chrysolepis) and the California live oaks (at least Q. wislizeni and Q. parvula) are also all noted for having shrub forms. Why do all these California oaks seem to be so good at getting shrubby? Is it multiple convergent mutations? Or is there pre-existing diversity under convergent selection in all these cases?

These oaks are also certainly pretty good at being trees, though. Like the blue oak trees (Q. douglasii) that thrive all over California’s driest, most drought-prone hills. Or Oregon white oaks (Q. garryana) that battle it out with conifers in the Pacific Northwest, carving out islands of oak woodland in that riot of forest vegetation. So let’s just say that oaks can do a whole lot of cool things pretty well and they do it in a whole bunch of different environments.

Q. garryana woodlandNow here’s the really cool part: the whole group of white oaks in California are probably able to hybridize with one another pretty easily wherever the co-occur. So it makes me wonder if they’re passing around these brilliant adaptations from population to population, species to species, as one great big and highly diverse multispecies complex? That’d be a pretty smart way of surviving in this wild and crazy world of ours, wouldn’t it?

But who knows.