The bio systematics of calylophus onagraceae

Towner, H.F.

Annals of the Missouri Botanical Garden 64(1): 48-120

1977


ISSN/ISBN: 0026-6493
Accession: 006607139

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Abstract
The genus Calylophus (Onagraceae), a segregate of Oenothera, was studied in reference to systematic relationships, breeding systems, pollination and cytology. Six species are recognized, 4 in sect. Salpingia: C. tubicula, C. hartwegii, C. toumeyi and C. lavandulifolius, and 2 in sect. Calylophus: C. berlandieri (formerly C. drummondianus) and C. serrulatus. Several changes in nomenclature and rank are made. Crosses performed among species demonstrated strong barriers to hybridization between the 2 sections of the genus and slight to moderate barriers among species within sections. Populations of Calylophus are distributed through the Great Plains, the southwestern USA and northern Mexico. The various taxa occupy distinct habitats which range from xeric sites in the Chihuahuan Desert to relatively mesic pine and pine-oak forests. In most forms of the genus, the plants are suffrutescent perennials and occupy calcareous soils. One form is restricted primarily to gypsum soils. Cytological investigations showed a remarkable degree of translocation heterozygosity in natural populations of Calylophus. Translocations were observed in all taxa, with 75% of 183 plants (excluding C. serrulatus) exhibiting heterozygosity for at least 1 translocation. Numerous plants were heterozygous for more than 1 translocation, and the mean number per plant was 1.3. C. serrulatus is a complex structural heterozygote and all individuals observed were heterozygous for at least 5 or 6 translocations. Hybridization experiments with C. berlandieri suggested that C. serrulatus maintains structural hybridity with gametophytic lethals in pollen and embryo sacs. The basic chromosome number of the genus is x = 7. Tetraploidy was observed in individuals from 5 of 62 populations of C. hartwegii that were examined. A few plants of several taxa possessed diminutive chromosomes ranging from 1-11 in number. The most frequent observation was of a single dark-staining pair in addition to the normal complement. Chromosome observations of hybrids showed profound intersectional differences in structure, primarily from translocations. Translocation differences are also marked among populations in sect. Calylophus, but are slight among the taxa of sect. Salpingia. The breeding systems of Calylophus are varied, with C. serrulatus self-compatible and highly autogamous and the other species self-sterile. C. berlandieri and C. tubicula have short floral tubes, strong UV contrast patterns, matinal anthesis, and are visited by a variety of diurnal insects. Anthesis of the remaining members of sect. Salpingia occurs in the afternoon or evening. These plants possess long floral tubes, variable UV contrast patterns, and are visited by sphingid moths and crepuscular bees in numbers that vary from locality to locality.