Jeffery J. Morawetz

Phylogeny, taxonomic affinities, and biogeography of Penstemon (Plantaginaceae) based on ITS and cpDNA sequence data

The large and diverse genus Penstemon (ca. 271 species) is endemic to North America and has been divided into six subgenera primarily based on anther dehiscence patterns. Species of Penstemon are known to be pollinated by a variety of insects (hymenopterans, lepidopterans, dipterans) and hummingbirds. Nucleotide sequence data from ITS and two noncoding regions of chloroplast DNA were used to reconstruct the phylogeny of Penstemon. Trees generated from nuclear and chloroplast DNA sequences are incongruent, which is probably the result of hybridization, and not fully resolved, which is likely due to a rapid evolutionary radiation. Penstemon represents a recent continental radiation where speciation has resulted primarily from evolutionary adaptations to ecological niches such as pollinator specialization. The results from these analyses show that the current circumscription of subgenera and sections needs revision to reflect more closely the evolutionary relationships of species. Specifically, species in subgenera Saccanthera, Habroanthus, and Penstemon are polyphyletic. These results also confirm the independent origin of hummingbird floral morphology in 10 clades.

Phylogenetics and the evolution of major structural characters in the giant genus Euphorbia L. (Euphorbiaceae)

Euphorbia is among the largest genera of angiosperms, with about 2000 species that are renowned for their remarkably diverse growth forms. To clarify phylogenetic relationships in the genus, we used maximum likelihood, bayesian, and parsimony analyses of DNA sequence data from 10 markers representing all three plant genomes, averaging more than 16kbp for each accession. Taxon sampling included 176 representatives from Euphorbioideae (including 161 of Euphorbia). Analyses of these data robustly resolve a backbone topology of four major, subgeneric clades--Esula, Rhizanthium, Euphorbia, and Chamaesyce--that are successively sister lineages. Ancestral state reconstructions of six reproductive and growth form characters indicate that the earliest Euphorbia species were likely woody, non-succulent plants with helically arranged leaves and 5-glanded cyathia in terminal inflorescences. The highly modified growth forms and reproductive features in Euphorbia have independent origins within the subgeneric clades. Examples of extreme parallelism in trait evolution include at least 14 origins of xeromorphic growth forms and at least 13 origins of seed caruncles. The evolution of growth form and inflorescence position are significantly correlated, and a pathway of evolutionary transitions is supported that has implications for the evolution of Euphorbia xerophytes of large stature. Such xerophytes total more than 400 species and are dominants of vegetation types throughout much of arid Africa and Madagascar.

A worldwide molecular phylogeny and classification of the leafy spurges, Euphorbia subgenus Esula (Euphorbiaceae)

The leafy spurges, Euphorbia subg. Esula, make up one of four main lineages in Euphorbia. The subgenus comprises about 480 species, most of which are annual or perennial herbs, but with a small number of dendroid shrubs and nearly leafless, pencil-stemmed succulents as well. The subgenus constitutes the primary northern temperate radiation in Euphorbia. While the subgenus is most diverse from central Asia to the Mediterranean region, members of the group also occur in Africa, in the Indo-Pacific region, and in the New World. We have assembled the largest worldwide sampling of the group to date (273 spp.), representing most of the taxonomic and geographic breadth of the subgenus. We performed phylogenetic analyses of sequence data from the nuclear ribosomal ITS and plastid ndhF regions. Our individual and combined analyses produced well-resolved phylogenies that confirm many of the previously recognized clades and also establish a number of novel groupings and place- ments of previously enigmatic species. Euphorbia subg. Esula has a clear Eurasian center of diversity, and we provide evidence for four independent arrivals to the New World and three separate colonizations of tropical and southern Africa. One of the latter groups further extends to Madagascar and New Zealand, and to more isolated islands such as Reunion and Samoa. Our results confirm that the dendroid shrub and stem-succulent growth forms are derived conditions in E. subg. Esula. Stem- succulents arose twice in the subgenus and dendroid shrubs three times. Based on the molecular phylogeny, we propose a new classification for E. subg. Esula that recognizes 21 sections (four of them newly described and two elevated from subsectional rank), and we place over 95% of the accepted species in the subgenus into this new classification.

Phylogenetics, morphological evolution, and classification of Euphorbia subgenus Euphorbia

Euphorbia subg. Euphorbia is the largest and most diverse of four recently recognized subgenera within Euphorbia and is distributed across the tropics and subtropics. Relationships within this group have been difficult to discern due mainly to homoplasious morphological characters and inadequate taxon sampling in previous phylogenetic studies. Here we present a phylogenetic analysis of E. subg. Euphorbia, using one nuclear and two plastid regions, for the most complete sampling of molecular sequence data to date. We assign 661 species to the subgenus and show that it is comprised of four highly supported clades, including a single New World clade and multiple independent lineages on Madagascar. Using this phylogenetic framework we discuss patterns of homoplasy in morphological evolution and general patterns of biogeography. Finally, we present a new sectional classification of E. subg. Euphorbia comprising 21 sections, nine of them newly described here.

Assessing the Monophyly of Alectra and Its Relationship to Melasma (Orobanchaceae)

Abstract Alectra (Orobanchaceae) consists of primarily hemiparasitic herbaceous species distributed mainly in sub-Saharan Africa, with two species native to tropical America, and two widespread species extending out of Africa into India and China. Despite containing an economically important noxious agricultural weed, Alectra has never been the subject of a phylogenetic analysis. The monophyly of Alectra was assessed using DNA sequences from the nuclear (internal transcribed spacer) and chloroplast (rpl16, trnT-L) genomes, including 11 of 12 species. One of two holoparasitic species, Alectra alba, was placed outside of Alectra, supported as sister to a lineage containing the Asian holoparasitic genera Aeginetia + Christisonia. Two highly supported lineages of Melasma were revealed: one containing the two included African species, and the other comprising the tropical American Melasma rhinanthoides and the single accession of the tropical American Escobedia. The placement of the Madagascan endemic Alectra fmticosa was shown to be unresolved in relationship to the remaining Alectra species and the two lineages containing Melasma. The monophyly of the remaining species of Alectra was highly supported.

The status of Harveya alba (Orobanchaceae)

SummaryOriginally described within Harveya, H. alba Hepper was transferred to Alectra, and nearly accommodated in its own monotypic genus. Recently published phylogenetic analyses support the placement of this species within Harveya as originally suggested by Hepper. The transfer is made here, and Harveya wysockiana is synonymised with H. alba.

Taxonomic Revision of the Alectra sessiliflora Complex (Orobanchaceae)

Abstract Alectra sessiliflora (Orobanchaceae) is the most widespread species within the genus, occurring throughout sub-Saharan Africa, and into India, China and the Philippines. Three varieties are currently recognized (A. sessiliflora var. monticola, A. sessiliflora var. senegalensis, and A. sessiliflora var. sessiliflora) and are distinguished by geographic range, calyx pubescence and stamen filament pubescence. Due to the overlapping nature of the characters used to distinguish among these varieties, accurate assignment of a specimen to a single variety is nearly impossible. We undertook a phenetic study of morphological characters to assess the validity of these varieties. Principal coordinate analysis and the unweighted pair-group method using arithmetic averages were used to explore whether specimens would cluster into the currently recognized varieties. Our analyses revealed no clustering based exclusively on geographic distribution. A small cluster of seven specimens was seen in the principal coordinate analysis using Gowers coefficient of similarity as input values, but this cluster was not diagnosable by unique characters. Based on these results we recommend that Alectra sessiliflora be recognized without infraspecific taxa. Finally, additional names are included as synonyms under Alectra sessiliflora based on extensive study of field-collected and herbarium specimens.