Genus Rhinotropis in Family Polygalaceae
In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.
Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.
Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).
Do you wish to read more about plant taxonomy? Click here!
Genus Description
Suggest a correction!Rhinotropis (authority (S.F. Blake) J.R. Abbott) is a North American genus in the milkwort family Polygalaceae. POWO currently treats approximately twelve species, and WFO lists about the same number (POWO, 2024; WFO, 2024). The genus is most diverse in the southwestern United States and northern Mexico, with additional representations in California and western Texas. The type species for Rhinotropis is R. cornuta (WFO, 2024).
Rhinotropis is diagnosed by a combination of shrubby habit, primarily opposite leaves lacking true stipules, a cymose or racemose inflorescence with two conspicuous lateral bracts that persist at fruit, and a two-lobed keel reduced to a crest or obsolete. The fruits are compressed loculicidal capsules with apically winged seeds bearing a pair of long, reflexed hairs at the base, a trait not consistently found in Polygala. The calyx is five-lobed with two lateral sepals that are usually enlarged.
Centers of diversity lie in the Arizona–New Mexico plateau, the southern Great Basin and Mojave Desert, and the California chaparral; several species are regional endemics (Abbott, 2011). Typical habitats include scrub, chaparral, open pine–oak woodland, desert foothills, and rocky or sandy slopes at moderate elevations.
Pollination and dispersal are documented only fragmentarily. Flowers appear to be visited by various bees and butterflies, although species-specific syndromes remain little studied; fruits dehisce to expose elaiosome-bearing seeds that are likely ant-dispersed (Abbott, 2011). Base chromosome numbers are not securely established across the genus and are therefore omitted here.
Taxonomically, Rhinotropis was segregated from Polygala based on morphology and subsequent phylogenetics (Abbott, 2011), which support monophyly of Rhinotropis relative to North American Polygala; comparative analyses by Eriksen and Ståhls (2011) corroborate the distinction. Alternative treatments placing the same taxa under Polygala persist in regional floras. Within Rhinotropis, modern sectional or subgeneric treatments have not been standardized; most authors recognize morphogroups without formal rank.
Several species are used in native landscaping in the southwestern United States, and a few are cultivated as ornamentals for drought-tolerant plantings; no species are major crops or timber sources (Turner, 1999; Abbott, 2011). The genus includes no widely recognized invasive taxa. Some narrow endemics face localized habitat loss and are incompletely assessed; updated threat assessments and range-wide surveys remain research priorities (POWO, 2024; WFO, 2024).
-
Rhinotropis acanthoclada ((A.Gray) J.R.Abbott)
-
Rhinotropis californica ((Nutt.) J.R.Abbott)
-
Rhinotropis cornuta ((Kellogg) J.R.Abbott)
-
Rhinotropis desertorum ((Brandegee) J.R.Abbott)
-
Rhinotropis heterorhyncha ((Barneby) J.R.Abbott)
-
Rhinotropis intermontana ((T.Wendt) J.R.Abbott)
-
Rhinotropis lindheimeri ((A.Gray) J.R.Abbott)
2 -
Rhinotropis madrensis ((T.Wendt) J.R.Abbott)
-
Rhinotropis maravillasensis ((Correll) J.R.Abbott)
-
Rhinotropis minutifolia ((Rose) J.R.Abbott)
-
Rhinotropis nitida ((Brandegee) J.R.Abbott)
3 -
Rhinotropis nudata ((Brandegee) J.R.Abbott)
-
Rhinotropis parryi ((A.W.Benn.) J.R.Abbott)
-
Rhinotropis purpusii ((Brandegee) J.R.Abbott)
-
Rhinotropis rimulicola ((Steyerm.) J.R.Abbott)
1 -
Rhinotropis rusbyi ((Greene) J.R.Abbott)
-
Rhinotropis subspinosa ((S.Watson) J.R.Abbott)