Boechera
Family: Brassicaceae
Boechera image
Tony Frates
  • FNA
  • Resources
Ihsan A. Al-Shehbaz, Michael D. Windham in Flora of North America (vol. 7)
Perennials or, rarely, biennials; (sexual or apomictic, caudex usually present, rarely absent); not scapose; usually glabrous or pubescent, rarely hirsute or hispid, trichomes simple or branched, 2-14-rayed, sometimes dendritic, not stellate. Stems erect, ascending, or decumbent, unbranched or branched distally. Leaves basal and cauline; petiolate or sessile; basal rosulate or not, petiolate, blade margins usually entire or dentate, rarely lyrate-pinnatifid; cauline usually sessile, rarely shortly petiolate, blade (base sometimes auriculate or sagittate), margins entire or dentate. Racemes (sometimes paniculate), often elongated in fruit. Fruiting pedicels erect, ascending, divaricate, or reflexed (secund or not), slender. Flowers: sepals ovate or oblong, (lateral pair slightly saccate or not basally, margins membranous); petals usually white, pink, lavender, or purple, rarely yellowish, red, or magenta, spatulate or oblanceolate, (claw shorter than sepals or undifferentiated from blade, apex obtuse); stamens tetradynamous; filaments not dilated basally; anthers ovate or oblong, (apex obtuse), [pollen ellipsoid (sexual plants) or spheroid (apomictic)]; nectar glands confluent, subtending bases of stamens, lateral glands semi-annular or annular. Fruits usually sessile, rarely shortly stipitate, usually linear, rarely oblong or lanceolate, straight or falcate, smooth or torulose; valves (papery), each with obscure or prominent midvein, usually glabrous, rarely pubescent; replum (visible), rounded; septum complete, (membranous, veinless); ovules 8-250 per ovary; (style sometimes obsolete); stigma capitate. Seeds usually uniseriate or sub-biseriate, rarely biseriate, flattened, winged, not winged, or margined, oblong or orbicular; seed coat (usually smooth or minutely reticulate, rarely papillate), not mucilaginous when wetted; cotyledons accumbent. Boechera falcata (Turczaninow) Al-Shehbaz is known from eastern Asia (Russian Far East).

Boechera often is treated as a synonym of Arabis (e.g., R. C. Rollins 1993; S. L. Welsh et al. 2003) but it has become clear that morphological similarities between these groups are due to evolutionary convergence, not shared ancestry. Molecular analyses by M. Koch et al. (2001) and T. Mitchell-Olds et al. (2005) revealed that Arabis and Boechera belong to distantly related clades of Brassicaceae that diverged some 19-25 million years ago. A new tribal classification of the family (I. A. Al-Shehbaz et al. 2006) places them in different tribes (Arabideae and Boechereae, respectively), reflecting their substantial molecular divergence.

The taxonomic complexity of Arabis, in the broad sense, is legendary (R. C. Rollins 1941, 1993; G. A. Mulligan 1996). When the genus is split, most of the problematic taxa come to reside in Boechera. A rare confluence of hybridization, apomixis, and polyploidy makes this one of the most difficult genera in the North American flora. The sexual diploid species are relatively distinct from one another, but they hybridize wherever they come into contact. Through apomixis and polyploidy, the hybrids become stable, self-propagating lineages. Most of the hybrid derivatives in Boechera are triploids, but apomictic diploids are known as well. Thus, for any pair of sexual diploid species (e.g., AA and BB), this process can yield different intermediates, including AB apomicts and both possible apomictic triploids (AAB and ABB). The situation becomes even more challenging when a third sexual diploid enters the picture. To date, we have identified three taxa (B. divaricarpa, B. pinetorum, B. tularensis) that appear to be trigenomic triploids. Under these circumstances, even the most distinctive sexual diploid progenitors can become lost in a seemingly continuous range of morphological variability.

In a genus characterized by the presence of polyploids and apomicts, it is essential to know which taxa represent the products of primary, divergent evolution (i.e., sexual diploids) and which are the result of secondary, reticulate evolution. Fortunately, a strong correlation between pollen morphology and ploidy level/reproductive mode facilitates the separation of sexual diploids from polyploids and apomicts in Boechera. Because of differences in meiosis, sexual diploids pr

Species within checklist: Cedar Breaks National Monument || << 51 - 100 taxa >>
Boechera howellii
Image of Boechera howellii
Boechera inyoensis
Image of Boechera inyoensis
Boechera johnstonii
Image of Boechera johnstonii
Boechera kelseyana
Image of Boechera kelseyana
Boechera koehleri
Image of Boechera koehleri
Boechera languida
Image of Boechera languida
Boechera lasiocarpa
Image of Boechera lasiocarpa
Boechera lemmonii
Image of Boechera lemmonii
Boechera lignifera
Image of Boechera lignifera
Boechera lincolnensis
Image of Boechera lincolnensis
Boechera lyallii
Image of Boechera lyallii
Boechera macounii
Image of Boechera macounii
Boechera microphylla
Image of Boechera microphylla
Boechera nevadensis
Image of Boechera nevadensis
Boechera nuttallii
Image of Boechera nuttallii
Boechera ophira
Image of Boechera ophira
Boechera oxylobula
Image of Boechera oxylobula
Boechera paddoensis
Image of Boechera paddoensis
Boechera pallidifolia
Image of Boechera pallidifolia
Boechera parishii
Image of Boechera parishii
Boechera patens
Image of Boechera patens
Boechera pauciflora
Image of Boechera pauciflora
Boechera paupercula
Image of Boechera paupercula
Boechera peirsonii
Image of Boechera peirsonii
Boechera pendulina
Image of Boechera pendulina
Boechera pendulocarpa
Image of Boechera pendulocarpa
Boechera perennans
Image of Boechera perennans
Boechera pinetorum
Image of Boechera pinetorum
Boechera pinzlae
Images
not available
Boechera pinzliae
Image of Boechera pinzliae
Boechera platysperma
Image of Boechera platysperma
Boechera polyantha
Image of Boechera polyantha
Boechera porphyrea
Image of Boechera porphyrea
Boechera pratincola
Image of Boechera pratincola
Boechera puberula
Image of Boechera puberula
Boechera pulchra
Image of Boechera pulchra
Boechera pusilla
Image of Boechera pusilla
Boechera pygmaea
Image of Boechera pygmaea
Boechera quadrangulensis
Image of Boechera quadrangulensis
Boechera quebecensis
Image of Boechera quebecensis
Boechera rectissima
Image of Boechera rectissima
Boechera repanda
Image of Boechera repanda
Boechera retrofracta
Image of Boechera retrofracta
Boechera rigidissima
Image of Boechera rigidissima
Boechera rollei
Images
not available
Boechera rollinsiorum
Image of Boechera rollinsiorum
Boechera rubicundula
Image of Boechera rubicundula
Boechera sanluisensis
Image of Boechera sanluisensis
Boechera saximontana
Image of Boechera saximontana
Boechera schistacea
Image of Boechera schistacea