Cobaea

Cobaea scandens

Cobaea scandens

Cobaea is a poorly known genus of 18 species of lianas native to tropical South and Central America.  The genus is pollinated by a diversity of animals including hawkmoths and hummingbirds. However, the most charismatic and well known pollinator are bats, as first suggested when claw marks were noticed on the outside of the corolla.  Cobaea scandens,one such bat-pollinated species, is sometimes cultivated.

Biogeography

Cobaea in endemic to Central America and northern South America.  Cobaea scandens is sometimes cultivated and may escape in many tropical areas.

worldwide distribution of  Cobaea

worldwide distribution of Cobaea

Phylogeny

The flowers of Cobaea are strikingly convergent with Bignoniaceae, and the genus was indeed originally placed in this family.  Cobaea is so morphologically dissimilar from other Polemoniaceae that it was long placed in its own family, Cobaeaceae. It is closely related to the similarly tropical and hummingbird-pollinated genus Cantua. However, molecular evidence indicates that Cobaea is most closely related to the bee-pollinated Mexican genus Bonplandia.

The only comprehensive phylogeny of Cobaea has been that of Prather (1998) using ITS sequences.  Prather recovered C. minor as sister to the rest of the genus.  Coabea pringlei, C. stipularis, C. biurita, and C. scandens form a clade sister to a polytomy of the rest of the genus.  Within this polytomy there is a well-supported clade of C. aequatoriensis, C. campanulata, and C. flava, a clade of C. lutea and C. rotundiflora, and a clade of C. aschersoniana, C. gracilis, and C. penudliflora. All species are recovered as monophyletic except for C. biaurita and C. lutea, although the limited scope of this dataset requires that species monophyly (or lack thereof) be investigated more fully.  These results do not confirm traditional subgeneric classification schemes.

As subgeneric levels in Cobaea relied on floral traits such as corolla lobe shape, inflorescence position, and stamen length are not monophyletic Prather and Jansen (1998) suggest that floral traits in Cobaea are highly liable.  Further investigation by Prather (1999a) suggested that these floral characters (as well as many vegetative characters) are highly homoplasious.

Biogeography

Cobaea is restricted to Mexico and northern South America. One species, C. pringlei, nearly reaches southern Texas.  Prather (1999b) suggested an origin for the genus in the Mexican Highlands with two independent migrations to South America

Taxonomy

  1. Cobaea aequatoriensis Asplund
  2. Cobaea aschersoniana Brand
  3. Cobaea biaurita Standley
  4. Cobaea campanulata Hemsl.
  5. Cobaea flava Prather
  6. Cobaea gracilis (Oersted) Hemsl.
  7. Cobaea lutea D. Don
  8. Cobaea minor M. Martens & Galeotti
  9. Cobaea pachysepala Standley
  10. Cobaea paneroi Prather
  11. Cobaea penduliflora (Karst.) Hook. f.
  12. Cobaea pringlei (House) Standley
  13. Cobaea rotundiflora Prather
  14. Cobaea scandens Cav.
  15. Cobaea skutchii I.M. Johnst.
  16. Cobaea stipularis Benth.
  17. Cobaea trianae Hemsl.
  18. Cobaea triflora Donnell Smith

KEY TO COBAEA (modified from Prather 1999b)

1. Style branches not twisted, papillae large, on adaxial surface only
2. Corolla tube 15-23 mm long…C. minor
2′. Corolla tube 29-65 mm long
3. Filaments villous 1-2 cm below the apex; calyx coriaceous; corolla lobes sharply acute to acuminate…C. pachysepala
3′. Filaments glabrous below the apex; calyx chartaceous; corolla lobes rounded or broadly acute
4. Corolla white, rarely suffused with purple…C. pringlei
4′. Corolla greenish or purple, suffused with purple
5. Lowermost leaflet pair < 0.5X length of the upper pairs…C. stipularis
5′. Lowermost leaflet pair + equal in length to the upper pairs
6. Calyx lobes rounded to emarginate, rarely broadly acute; calyx (16-) 19-32 mm wide…C. scandens
6′. Calyx lobes attenuate to long-acuminate; calyx 7-18 mm wide
7. Style 40-45 mm long; filaments adnate at base for 3-5 mm…C. paneroi
7′. Style 47-80 mm long; filaments adnate at base for (3-) 5-10 mm
8. Base of lowermost leaflet pair cordate to truncate; style branches 2-3 mm long…C. trianae
8′. Base of lowermost leaflet pair auriculate; style branches 3-6 mm long…C. biaurita
1′. Style branches usually twisted, papillae short, distributed all over the surface
9. Corolla lobes < 2X as long as the tube
10. Apex of corolla lobes rounded to acute; stamens < 55 mm long
11. Calyx margin undulate…C. skutchii
11′. Calyx margin plane
12. Calyx segments 8-12 mm wide; corolla lobe acute…C. rotundiflora
12′. Calyx segments 4-7 mm wide; corolla lobes rounded
13. Pedicels 10.5-16.0 cm long, filaments adnate at base for 8-14 mm…C. flava
13′. Pedicels 19-28 cm long, filaments adnate at base for 3-7 mm
14. Stems glabrous; corolla lobes 11-19 mm long…C. campanulata
14′. Stems pubescent (at least at nodes); corolla lobes 8-11 mm long…C. triflora
10′. Apex of corolla lobes acuminate or linear; stamens > 58 mm long
15. Stems, pedicels, and calyx villous; corolla lobes (27-) 38-59 mm long…C. aschersoniana
15′. Stems, pedicels, and calyx glabrous to pubescent; corolla lobes 13-30 mm long…C. lutea
9′. Corolla lobes > 2X the tube
16. Pedicel villous; calyx densely long-ciliate…C. aequatoriensis
16′. Pedicel glabrous to puberulent; calyx glabrous or sparsely ciliate
17. Lowermost leaflet pair not ciliate basally; anthers 8-11 mm long…C. gracilis
17′. Lowermost leaflet pair ciliate basally; anthers 11-15 mm long…C. penduliflora

References

Prather, L. A. and R. K. Jansen. 1998. The phylogeny of Cobaea (Polemoniaceae) based on sequence data from the ITS region of nuclear ribosomal DNA. Systematic Botany 23: 55-70.

Prather, L. A. 1999a. The relative lability of floral vs non-floral characters and a morphological phylogenetic analysis of Cobaea (Polemoniaceae). Botanical Journal of the Linnean Society. 131: 433-450.

Prather, L. A. 1999b. Systematics of Cobaea (Polemoniaceae). Systematic Botany Monographs 57: 1-81.

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