Boechera californica (Rollins) Windham & Al-Shehbaz

Genus Classification and Common Name

The genus Boechera, commonly called rockcress, belongs to the plant family Brassicaceae.

Etymology and Namesake

It was named for Danish botanist Tyge W. Böcher (1909–1983), who specialized in research on alpine plants, including the mustards Draba and Boechera holboellii.

Taxonomic Relationship to Arabidopsis

Recent molecular studies confirm that Boechera is closely related to the genus Arabidopsis, which contains the widely studied model plant Arabidopsis thaliana.

Historical Classification and Generic Separation

Until recently, all members of Boechera were classified within the genus Arabis, but genetic and cytological data have supported separating the two genera.

Chromosome Number Comparison

Unlike Arabis, which has a base chromosome number of x=8, Boechera has a base chromosome number of x=7, and many of its taxa are triploid.

North American Distribution and Diversity

Boechera is a primarily North American genus, with the highest species diversity in the western United States.

Extra-North American Range

Its distribution also extends to Greenland and the Russian Far East.

Taxonomic Identification Challenges

The genus remains understudied, and most species are hard to distinguish from one another using morphological traits, though a number of clearly distinct species have been identified.

Growth Form

Most members of the genus are perennials.

Morphological Traits

They typically have pubescent leaves with stellate trichomes, narrow curving fruits, and small white to purple flowers arranged in elongated racemes.

Unresolved Evolutionary Relationships

Evolutionary relationships within the genus are not yet resolved, and some eastern North American species, such as Boechera laevigata, may belong to a clade that is separate from the rest of the genus.

Asexual Reproduction Trait

A notable trait of many Boechera species is asexual reproduction through the process of apomixis.

Apomictic Lineage Origin

Microsatellite data shows that some apomictic lineages are hybrids formed from two or more sexually reproducing parent species.

Ecological Role

Ecologically, Boechera species are one of the main food sources for caterpillars of the butterfly Pieris oleracea.