Flora of North America species comparison

Passiflora caerulea is cultivated widely in the flora area but naturalized only in the Los Angeles metropolitan area (see F. Hrusa et al. 2002). It is possibly introduced in the Mule Mountains of southeastern Arizona (J. Koweek, pers. comm.), although this has not been confirmed. It was reported also from Utah by S. L. Welsh et al. (2003), although as “cultivated...long-persisting,” suggesting that it is not actually naturalized there. This species is cold-hardy and can be cultivated in gardens in relatively cold regions (at least USDA plant hardiness zone 6), but it is unlikely to flower in such areas because of relatively short growing seasons, although it still makes an interesting foliage plant. Even in the absence of sexual reproduction, this species can persist and even spread locally by root suckering.

The artificial hybrid Passiflora ×belotii will key to P. caerulea in this treatment. However, the leaves of P. ×belotii are consistently three-lobed, unlike the primarily five- to seven-lobed leaves of P. caerulea.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera 17, species ca. 750 (1 genus, 18 species in the flora).

Passifloraceae have been historically assumed to be closely related to Achariaceae, Caricaceae, Cucurbitaceae, Flacourtiaceae, Malesherbiaceae, and Turneraceae (A. Cronquist 1981); they are currently considered to be most closely related to the latter two families, seated within Malpighiales (D. E. Soltis et al. 2000; M. W. Chase et al. 2002; Angiosperm Phylogeny Group 2003; N. Korotkova et al. 2009). All three families have cyanogenic compounds, flowers with a hypanthium often not bearing the stamens, a floral corona (although uncommon in Turneraceae), tricarpellate ovaries with three elongate styles, parietal placentation, and five stamens (Cronquist; Angiosperm Phylogeny Group). Because of the close relationship of these three families, they have recently been treated as an expanded Passifloraceae (Chase et al.; Angiosperm Phylogeny Group). Passifloraceae are still considered relatively closely related

to members of the now ex-Flacourtiaceae, particularly Salicaceae in the broad sense (Chase et al.), which includes the apparently corona-bearing Abatia Ruiz & Pavón (coronal filaments in Abatia, unlike those in Passifloraceae, are clearly staminal appendages; see A. Bernhard 1999), although the members of Flacourtiaceae that have cyanogenic compounds are possibly more distantly related to Passifloraceae and are now placed in a greatly expanded Achariaceae (Chase et al.). The family description provided above represents Passifloraceae in the narrow sense; Malesherbiaceae and Turneraceae are not included.

Passifloraceae are divided into two tribes: Passifloreae de Candolle, containing genera with tendril-bearing vines and scandent shrubs (or rarely small trees without tendrils), and Paropsieae de Candolle, containing genera without tendrils that are shrubby or arborescent (W. J. J. O. de Wilde 1971). Paropsieae have been assigned to Flacourtiaceae or are seen as transitional between Flacourtiaceae and Passifloraceae (de Wilde). Morphological evidence supports the inclusion of Paropsieae within Passifloraceae (E. S. Ayensu and W. L. Stern 1964), further supported by recent molecular phylogenetic evidence (D. E. Soltis et al. 2000; M. W. Chase et al. 2002). Beyond this, intergeneric relationships are largely unknown within Passifloraceae. The tribes may not be distinct as currently defined and some genera are probably derived from within Passiflora (that is, Hollrungia K. Schumann and Tetrapathaea (de Candolle) Reichenbach; S. E. Krosnick and J. V. Freudenstein 2005).

The floral corona of Passifloraceae is of uncertain origin, considered derived from the perianth (V. Puri 1948) or consisting of staminodes (P. K. Endress 1996). It has an unusual pattern of development, inward from the outer and inner margins of a ringlike primordium; its development is delayed until well after the fertile stamens begin to form; and the arrangement and number of coronal filaments is not consistent with that of the fertile stamens. There is little support for the corona being derived from perianths or staminodes (A. Bernhard 1999).

(Discussion copyrighted by Flora of North America; reprinted with permission.)