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Boechera
Family: Brassicaceae
Boechera image
Matt Lavin from Bozeman, Montana, USA  
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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

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Show all taxa || << 1 - 50 taxa >>
Boechera acutina
Image of Boechera acutina
Boechera arcuata
Image of Boechera arcuata
Boechera atrorubens
Image of Boechera atrorubens
Boechera beckwithii
Image of Boechera beckwithii
Boechera bodiensis
Image of Boechera bodiensis
Boechera breweri
Image of Boechera breweri
Boechera calderi
Image of Boechera calderi
Boechera californica
Image of Boechera californica
Boechera carrizozoensis
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not available
Boechera cascadensis
Image of Boechera cascadensis
Boechera centrifendleri
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not available
Boechera cobrensis
Image of Boechera cobrensis
Boechera collinsii
Image of Boechera collinsii
Boechera consanguinea
Image of Boechera consanguinea
Boechera constancei
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not available
Boechera covillei
Image of Boechera covillei
Boechera crandallii
Image of Boechera crandallii
Boechera cusickii
Image of Boechera cusickii
Boechera davidsonii
Image of Boechera davidsonii
Boechera demissa
Image of Boechera demissa
Boechera depauperata
Image of Boechera depauperata
Boechera dispar
Image of Boechera dispar
Boechera divaricarpa
Image of Boechera divaricarpa
Boechera drepanoloba
Image of Boechera drepanoloba
Boechera duchesnensis
Image of Boechera duchesnensis
Boechera elkoensis
Image of Boechera elkoensis
Boechera evadens
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not available
Boechera falcatoria
Image of Boechera falcatoria
Boechera falcifructa
Image of Boechera falcifructa
Boechera fecunda
Image of Boechera fecunda
Boechera fendleri
Image of Boechera fendleri
Boechera fernaldiana
Image of Boechera fernaldiana
Boechera formosa
Image of Boechera formosa
Boechera fructicosa
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not available
Boechera fruticosa
Image of Boechera fruticosa
Boechera glareosa
Image of Boechera glareosa
Boechera glaucovalvula
Image of Boechera glaucovalvula
Boechera goodrichii
Image of Boechera goodrichii
Boechera gracilenta
Image of Boechera gracilenta
Boechera gracilipes
Image of Boechera gracilipes
Boechera grahamii
Image of Boechera grahamii
Boechera gunnisoniana
Image of Boechera gunnisoniana
Boechera harrisonii
Image of Boechera harrisonii
Boechera hastatula
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not available
Boechera hirshbergiae
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not available
Boechera hoffmannii
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not available
Boechera holboellii
Image of Boechera holboellii
Boechera horizontalis
Image of Boechera horizontalis
Boechera howellii
Image of Boechera howellii
Boechera inyoensis
Image of Boechera inyoensis
The National Science Foundation
Developments of SEINet, Symbiota, and associated specimen databases have been supported by National Science Foundation Grants (DBI 9983132, BRC 0237418, DBI 0743827, DBI 0847966)