| Systematics, character evolution, biogeography, and diversification of the angiosperm family Hydrophyllaceae are explored using molecular and morphological phylogenetic techniques. Three independent yet statistically congruent data sets were combined and used to reconstruct relationships, including DNA sequence data from the chloroplast gene ndhF and from the internal transcribed spacer (ITS) region of the nuclear rDNA and morphological data. Several observations were made about relationships: (1) Hydrophyllaceae, as traditionally circumscribed, are not monophyletic because the genera Codon and Hydrolea are excluded, (2) the remaining "core" Hydrophyllaceae are entirely New World in distribution, (3) the "core" Hydrophyllaceae are nested in a paraphyletic Boraginaceae s.l. and are most closely related to the tropical, woody members of that group, (4) the parasitic family Lennoaceae is more closely related to Boraginaceae subf. Ehretioideae than to Hydrophyllaceae, and (5) The "core" Hydrophyllaceae are divided into two clades, a mostly herbaceous Clade I with no formal taxonomic designation and Clade II corresponding to the tribe Nameae. Clade I includes both the tribes Phacelieae (paraphyletic) and Hydrophylleae (monophyletic). The largest genus in the family, Phacelia, is monophyletic and its sister taxon is Romanzoffia. Nama, the second largest genus, is not monophyletic because N. lobbii and N. rothrockii are more closely related to Eriodictyon and relatives.;The combined data phylogeny showed that Hydrophyllaceae and Boraginaceae fit a trend in angiosperm evolution called the tropical/temperate family-pairs hypothesis. The origination of the "core" Hydrophyllaceae coincided with a migration event to the temperate zone, primarily into the California Floristic Province where about half of the species are native. Hydrophyllaceae are often noted to be one of the most species rich groups in western North America; however, their origination does not coincide with an increase in diversification rate relative to their nearest outgroups. It is equally parsimonious for the common ancestor to be either herbaceous or woody, but only a loss of woodiness would corroborate the family pairs hypothesis. Trends in evolution of particular growth forms, such as xerophytic perennial herbs and annual herbs, indicate extreme lability in evolution of habit. |
