HOLT, KATHERINE1*, LEIGH A. JOHNSON1, J. MARK PORTER2, and JOHN S. GARDNER1. 1Department of Botany and Range Science, Brigham Young University, Provo, UT 84602; 2Rancho Santa Ana Botanic Garden, 1500 North College Avenue, Claremont, CA 91711. - External seed coat morphology of Gilia (Polemoniaceae) and segregate genera: comparison and correspondence with phylogenetic relationships.
Pollen exine morphology has been widely surveyed in the phlox family
with considerable discussion regarding its taxonomic utility. However,
with the exception of thorough SEM sampling of Collomia, work
in Cobaea, and description of general classes of mucilage
production and cell-separation characteristics, seed coat
micromorphology has been largely neglected in Polemoniaceae. A broad
SEM survey of mature, dry seeds throughout this family reveals
diversity in characteristics of cell wall boundaries, presence,
absence, size, shape, and distribution of verrucae, and features of
the hilum. Similar to the general uniformity in seed coats reported
for Collomia, the seeds of Gilia sensu sticto show
little variation: verrucae are either absent or minutely developed in
the earliest branching species. Segregate genera Lathrocasis
and Saltugilia, also members of Gilieae, are characterized by
substantially larger verrucae and cell wall boundaries obscurely
apparent as low ridges, but differ in finer levels of verrucae
appearance. Two markedly different patterns distinguish the testa of
former Gilia species removed to Linanthus, with both
types represented in other members of Phlocideae. In Loeselieae,
Aliciella, Giliastrum, Bryantiella, and
Dayia possess distinctive testa and three readily
distinguishable patterns are found in Aliciella alone. Although
the several classes of external morphology noted in this study
correspond well to lineages of Polemoniaceae identified in DNA-based
phylogenetic analyses of this family, the greater value of this work
is the description of characters for morphology-based phylogenetics
and further investigation into seed evolution in this family.
Key words: Gilia, phylogeny, Polemoniaceae, seed morphology, systematics