Flora of North America species comparison

Species 7 (7 in the flora).

Keckiella is nearly endemic to the California Floristic Province (P. H. Raven and D. I. Axelrod 1978). In the flora area, taxa range beyond California into Arizona and Nevada; two occur in Mexico (Baja California Peninsula).

All taxa of Keckiella were first described in Penstemon, where they were long recognized as related to each other and anomalous within Penstemon. Keckiella taxa were treated as Keckia Straw before the prior use of that name for a fossil alga was noticed. The relationship of Keckiella and Penstemon with the rest of Cheloneae was clarified by A. D. Wolfe et al. (2002). This confirmed the classification implied by D. D. Keck (1936) and proposed by R. M. Straw (1966). The two genera are now recognized as distinct evolutionary lineages based on morphology, rust fungi relationships, phytochemistry, and DNA evidence (D. B. O. Savile 1968b, 1979; D. C. Michener 1982; O. Mistretta and R. Scogin 1989; Wolfe et al.; C. E. Freeman et al. 2003).

Among Keckiella species, gross morphological and anatomical characteristics of leaf and wood correlate with habitat; floral characters, other than the distinctive nectary structure that helps define Keckiella, reflect the pollination syndrome (D. C. Michener 1981, 1982). Leaf morphology is typical of drought-deciduous plants (Michener 1981). Varieties are recognized in part on foliage and calyx indument. Leaf primordia of all species are (weakly) pubescent with glandular and non-glandular hairs, making indument a challenging character for interpretation.

Pollination biology and habitat tolerances appear to have been important in species diversification. Bee pollination is fundamental in Keckiella, with floral size among the species scaled to a range of native bees; hummingbird pollination is polyphyletic in parallel with Penstemon (D. C. Michener 1982; C. E. Freeman et al. 2003; Paul Wilson et al. 2007). Natural hybrids have been found repeatedly for two species pairs (K. antirrhinoides var. antirrhinoides and K. cordifolia; K. breviflora var. glabrisepala and K. lemmonii) where the ranges overlap. The pollination syndromes are not effective barriers to extraneous cross pollination: even the hummingbird-pollinated species are visited by small pollen-foraging bees that may promote some pollination or hybridization separate from the hummingbirds (Michener). Leaf flavonoids do not support the hummingbird-pollinated species being each other’s closest relatives (O. Mistretta and R. Scogin 1989).

Species of Keckiella are widespread but only locally common in their habitat. They usually occur in unstable sites such as slopes, scree, and crevices in rocky faces from near sea level to 3000 m. These local micro-sites may be less fire prone than the immediately surrounding communities. Fire ecology may be important in the evolution of the species; root gnarls found only in K. antirrhinoides var. antirrhinoides and K. cordifolia may help these species resprout following the fires typical of their low-elevation habitats (D. C. Michener 1981).

The eco-evolutionary segregation of Keckiella from its relatives may have been centered on the Klamath region during the Tertiary (A. D. Wolfe et al. 2002). C. E. Freeman et al. (2003) recognized three clades within Keckiella: the basal-most K. rothrockii lineage, a northern clade (K. breviflora, K. corymbosa, K. lemmonii, and K. ternata), ranging from southern to northern California and through almost the entire 3000 m elevational range of the genus, and a southern clade (K. antirrhinoides and K. cordifolia) nearly restricted to lower elevations in southern California and Baja California, Mexico. They argued that speciation in these clades likely reflects repeated regional and elevational migration during the Pleistocene, presumably including the ecological scenarios that led to the modern species in fire-dominated vegetation types.

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

Varieties 2 (2 in the flora).

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