C. Matt Guilliams

Familial classification of the Boraginales

The Boraginales are now universally accepted as monophyletic and firmly placed in Lamiidae. However, a consensus about familial classification has remained elusive, with some advocating recognition of a single, widely variable family, and others proposing recognition of several distinct families. A consensus classification is proposed here, based on recent molecular phylogenetic studies, morphological characters, and taking nomenclatural stability into consideration. We suggest the recognition of eleven, morphologically well-defined and clearly monophyletic families, namely the Boraginaceae s.str., Codonaceae, Coldeniaceae fam. nov., Cordiaceae, Ehretiaceae, Heliotropiaceae, Hoplestigmataceae, Hydrophyllaceae, Lennoaceae, Namaceae, and Wellstediaceae. Descriptions, synonomy, a taxonomic key, and a list of genera for these eleven families are provided, including the new family Coldeniaceae (monogeneric) and Namaceae (segregated from Hydrophyllaceae and comprising Nama, Eriodictyon, Turricula, and Wigandia), the latter necessitating a revised circumscription of a more morphologically coherent Hydrophyllaceae.

Uncorrelated evolution of leaf and petal venation patterns across the angiosperm phylogeny

Early angiosperm evolution, beginning approximately 140 million years ago, saw many innovations that enabled flowering plants to alter ecosystems globally. These included the development of novel, flower-based pollinator attraction mechanisms and the development of increased water transport capacity in stems and leaves. Vein length per area (VLA) of leaves increased nearly threefold in the first 30-40 million years of angiosperm evolution, increasing the capacity for transpiration and photosynthesis. In contrast to leaves, high water transport capacities in flowers may not be an advantage because flowers do not typically contribute to plant carbon gain. Although flowers of extant basal angiosperms are hydrated by the xylem, flowers of more recently derived lineages may be hydrated predominantly by the phloem. In the present study, we measured leaf and flower VLA for a phylogenetically diverse sample of 132 species from 52 angiosperm families to ask (i) whether flowers have lower VLA than leaves, (ii) whether flowers of basal angiosperm lineages have higher VLA than more recently derived lineages because of differences between xylem and phloem hydration, and (iii) whether flower and leaf VLA evolved independently. It was found that floral structures had lower VLA than leaves, but basal angiosperm flowers did not have higher VLA than more derived lineages. Furthermore, the independent evolution of leaf and petal VLA suggested that these organs may be developmentally modular. Unlike leaves, which have experienced strong selection for increased water transport capacity, flowers may have been shielded from such selective pressures by different developmental processes controlling VLA throughout the plant bauplan.

Pleistocene radiation of the serpentine-adapted genus Hesperolinon and other divergence times in Linaceae (Malpighiales)

PREMISE OF THE STUDY Hesperolinon (western flax; Linaceae) is endemic to the western United States, where it is notable for its high and geographically concentrated species diversity on serpentine-derived soils and for its use as a model system in disease ecology. We used a phylogenetic framework to test a long-standing hypothesis that Hesperolinon is a neoendemic radiation. METHODS Five plastid and two ribosomal nuclear DNA gene regions were sampled from 105 populations of Hesperolinon, including all 13 recently recognized species across their known ranges. We used these data to generate population-level phylogenies of Hesperolinon. We also generated a robustly sampled chronogram of Linaceae using an eight-gene, 100-taxon supermatrix calibrated using fossil Linum pollen and a published chronogram of Malpighiales. KEY RESULTS Most diversification in Hesperolinon has taken place in the past 1-2 million yr, much more recently than previous estimates. Only the earliest-diverging species, H. drymarioides, was resolved as a clade. Denser taxon and gene sampling generally support previously proposed relationships within Linaceae, but with more recent diversification of key clades. CONCLUSIONS Hesperolinon is an excellent example of edaphic neoendemism, in support of Raven and Axelrods hypothesis for the genus. Dense population-level sampling reveals a complex of incipient species, with clades poorly aligned with traditional morphological circumscriptions, likely due in part to continued gene flow. The diversification of Linaceae is more recent than previously estimated, and other recent radiations (e.g., Hugonia) warrant further study.

CALYPTRIDIUM PARRYI VAR. MARTIRENSE (MONTIACEAE), A NEW TAXON ENDEMIC TO THE SIERRA DE SAN PEDRO MARTIR, BAJA CALIFORNIA, MEXICO

Abstract Calyptridium parryi var. martirense is described as new. Here we present quantitative measurements and statistical analyses of a number of morphological features that demonstrate the distinctiveness of this new taxon. The new variety differs from the others in having shorter fruits (3.1–4.1 mm) and a correspondingly smaller fruit length to sepal length ratio (1.0–1.4). The capsule is also the widest (1.4–2.2 mm) and the sepals the longest (2.4–3.9 mm) of any other C. parryi variety. Calyptridium parryi var. martirense is currently known only from high elevation locations (1900–2630 m) in the Sierra de San Pedro Mártir, Baja California, Mexico.

Memoirs of a frequent flier: Phylogenomics reveals 18 long-distance dispersals between North America and South America in the popcorn flowers (Amsinckiinae)

PREMISE OF THE STUDY American amphitropical disjunction (AAD) is an important but understudied New World biogeographic pattern in which related plants occur in extratropical North America and South America, but are absent in the intervening tropics. Subtribe Amsinckiinae (Boraginaceae) is one of the richest groups of plants displaying the AAD pattern. Here, we infer a time-calibrated molecular phylogeny of the group to evaluate the number, timing, and directionality of AAD events, which yields generalizable insights into the mechanism of AAD. METHODS We perform a phylogenomic analysis of 139 samples of subtribe Amsinckiinae and infer divergence times using two calibration schemes: with only fossil calibrations and with fossils plus a secondary calibration from a recent family level analysis. Biogeographic analysis was performed in the R package BioGeoBEARS. KEY RESULTS We document 18 examples of AAD in the Amsinckiinae. Inferred divergence times of these AAD examples were strongly asynchronous, ranging from Miocene (17.1 million years ago [Ma]) to Pleistocene (0.33 Ma), with most (12) occurring <5 Ma. Four events occurred 10-5 Ma, during the second rise of the Andes. All AAD examples had a North America to South America directionality. CONCLUSIONS Second only to the hyperdiverse Poaceae in number of documented AAD examples, the Amsinckiinae is an ideal system for the study of AAD. Asynchronous divergence times support the hypothesis of long-distance dispersal by birds as the mechanism of AAD in the subtribe and more generally. Further comparative phylogenomic studies may permit biogeographic hypothesis testing and examination of the relationship between AAD and fruit morphology, reproductive biology, and ploidy.

Cryptantha wigginsii (Boraginaceae): A Presumed Extinct Species Rediscovered

Abstract Cryptantha wigginsii I.M. Johnston (Boraginaceae) had previously been known from a single collection made in April 1931, at a locality 18 miles south of Tijuana, Baja California, Mexico. This species is distinctive and unique in the genus in having nutlets with a surface that is smooth and glossy near the base and densely tuberculate at the apex. Because of the absence of subsequent collections, the species was presumed extinct. However, a population of C. wigginsii was recently discovered in Carlsbad, San Diego Co., California, constituting a new county, state, and country plant species record. Subsequent field investigations and study of (mis-identified) Cryptantha specimens at several California herbaria has turned up additional documented populations of this species in the USA and coastal northwestern Baja California, Mexico. In addition to the three adjacent Carlsbad populations and the type locality in Baja California, populations known to date include: 1) five from Santa Catalina Island, L...

Taxonomy of Calyptridium parryi (Montiaceae)

Abstract Calyptridium parryi (Montiaceae, formerly Portulacaceae) putatively comprises four varieties: arizonicum, hesseae, nevadense, and parryi. We performed a detailed phenetic analysis of seed, fruit, and sepal morphology in order to assess the distinction and rank of these varieties. We treated the San Pedro Martir Mountains, Baja California populations of C. parryi as a separate taxonomic unit in these studies, given their great disjunct distribution. In addition, we included the very similar and largely sympatric C. monandrum in these analyses. Results from ANOVA and principal components analysis indicate that the six entities examined are, to various degrees, morphologically diagnosable. Calyptridium parryi varieties hesseae, nevadense, and parryi show some overlap in features, and we propose keeping these as varieties. Populations from the San Pedro Martir Mountains are distinct from other varieties of C. parryi, possibly warranting varietal status, but further studies with more samples are needed to confirm this. However, we conclude that C. parryi variety arizonicum is different enough in several features and geographic range to warrant species status, by a taxonomic/morphologic species concept. Calyptridium monandrum should be retained as a separate species.