Neotropical Koeberliniaceae

Victor W. Steinmann

Instituto de Ecología, A.C., Centro Regional del Bajío, Pátzcuaro, Mexico.
 

Description

Shrubs or small trees, strongly xerophytic, glabrous or puberulent with unicellular, unbranched trichomes; stems greenish and photosynthetic, divaricately and intricately branched, spinescent at the tips. Leaves alternate, caducous, estipulate; lamina simple, entire, scale-like. Flowers in umbel-like axillary racemes, actinomorphic, hermaphroditic, disk absent; sepals 4, imbricate, free; petals 4, imbricate, free; stamens twice as many as the sepals, free, equal, introrse, with longitudinal dehiscence, pollen tricolporate; ovary superior, shortly stipitate, 2(3)-locular, locules connate, each with numerous ovules, anatropous, placentation axillarystyle 1, apical, persistent, stigma 2-4 lobed. Fruit a subglobose berry. Seeds 2-4, exarillate, with scanty endosperm, embryo curved. X=11.

Notes on delimitation

  • The Koeberliniaceae contains a single genus with two species: Koeberlinia spinosa Zucc. of northern Mexico and the southwest United States and K. holacantha W.C. Holmes, K.L. Yip & Rushing, an endemic to Bolivia.
  • The family has generally been recognized as distinct in modern times, although it has also been included in the Capparaceae.  Molecular phylogenetic studies support it being treated as an independent taxon.  It belongs to the order Brassicales in a clade sister to the families Bataceae and Salvadoraceae.

Distribution in the Neotropics

  • Widely distributed in arid scrub vegetation across the southwest United States (Texas to California) and through northern Mexico to the states of Querétaro and Hidalgo; it is disjunct in deserts of central Bolivia.

Distinguishing characters (always present)

Key differences from similar families

  • Although closely related to the families Bataceae and Salvadoraceae, the Koeberliniaceae is readily distinguished from both of these by possessing alternate, highly reduced (vs. opposite, well-developed) leaves. 
  • It is more easily confused with other arid-adapted spiny shrubs with highly reduced leaves, such as Canotia (Celastraceae), Adolphia (Rhamnaceae), Condalia (Rhamnaceae), Holacantha (Simaroubaceae), and Castela (Simaroubaceae).  From Canotia, Adolphia, and Condalia it can be separated by having 4-merous flowers with eight stamens (vs. 5-merous flowers with 5 stamens) and berries (vs. capsules).  From Holacantha and Castela it is recognized by having bisexual flowers with a single ovary (vs. unisexual flowers, the plants dioecious, the pistillate with separate ovaries).

Number of genera

  • One: Koeberlinia Zucc.

Status

  • Native to the Neotropics.

General notes

  • The highly reduced leaves are quickly shed, and photosynthesis occurs primarily in the green branches.
  • Plants from Bolivia were long considered conspecific with those from Mexico and the southwestern United States, and only recently were they proposed as a distinct species (Holmes et al., 2008).
  • The family is of no known economic value.

Important literature

Hall, J.C., H. H. Iltis, and K. J. Sytsma. 2004. Molecular phylogenetics of core Brassicales, placement of orphan genera Emblingia, Forchhammeria, Tirania, and character evolution. Syst. Bot. 29: 654-669.

Holmes, W. C., K. L. Yip, and A. E. Rushing. 2008. Taxonomy of Koeberlinia (Koeberliniaceae). Brittonia 60:171-184.

Kubitzki, K. 2003. Koeberliniaceae. Pp. 218-219. In: K. Kubitzki and C. Bayer (eds.). The families and genera of vascular plants. Volume 6. Flowering plants. Dicotyledons: Malvales, Capparales, and non-betalain Caryophyllales. Springer-Verlag, Berlin.

Mehta, I. J. & M. F. Moseley, Jr. 1981. The floral anatomy of Koeberlinia Zucc.: systematic implications. Amer. J. Bot. 68: 482-497.

Tobe, H. and P.H. Raven. 2008. Embryology of Koeberlinia (Koeberliniaceae): Evidence for core-Brassicalean affinities. Amer. J. Bot. 95: 1475-1486.

How to cite

Steinmann, V.W. (2009). Neotropical Koeberliniaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Koeberliniaceae.htm.