Susan M. Swensen

When in doubt, put it in Flacourtiaceae: a molecular phylogenetic analysis based on plastid rbcL DNA sequences

Summary. Circumscription of Flacourtiaceae was investigated with a phylogenetic analysis of plastid rbcL DNA sequences, and the family was found to be composed of two clades that are more closely related to other families in Malpighiales than to each other. In one of these, that containing the type genus Flacourtia, Salicaceae are embedded, whereas the other clade includes the members of the peculiar and poorly known South African Achariaceae. The latter family name is conserved against all listed synonyms. Thus we propose the recognition of two families: i) Salicaceae sensu lato, including tribes Banareae, Bembicieae, Scolopieae, Samydeae (syn. Casearieae), Homalieae, Flacourtieae, Prockieae and Saliceae, as well as Abatieae (by some authors of Passifloraceae) and Scyphostegieae (Scyphostegia of the monogeneric Scyphostegiaceae); and ii) Achariaceae sensu lato, including tribes Pangieae, Lindackerieae, Erythrospermeae and Acharieae (Acharia, Ceratiosicyos and Guthriea of Achariaceae). Several genera considered by many previous authors to be members of Flacourtiaceae are excluded from Malpighiales: Berberidopsis and Aphloia fall near the base of the higher eudicots. Several tribes require different names from those used in previous systems, and we include an appendix indicating a tentative revised tribal taxonomy for both Salicaceae and Achariaceae sensu lato.

Taxonomic Affinities of Medusagyne oppositifolia (Medusagynaceae)

Medusagyne oppositifolia Baker is the sole member of Medusagynaceae Engl. & Gilg and its phylogenetic position has been unclear. Analysis of rbcL sequence data indicates a close and strongly supported relationship to Ochnaceae and Quiinaceae, but does not resolve the relationships between these taxa. Together the three families form a monophyletic group with a somewhat more distant relationship to other linalean groups including Malpighiaceae, Linaceae and phyllanthoid Euphorbiaceae.

Circumscription of the Malvales and relationships to other Rosidae: evidence from RBCL sequence data

The order Malvales remains poorly circumscribed, despite its seemingly indisputable core constituents: Bombacaceae, Malvaceae, Sterculiaceae, and Tiliaceae. We conducted a two-step parsimony analysis on 125 rbcL sequences to clarify the composition of Malvales, to determine the relationships of some controversial families, and to identify the placement of the Malvales within Rosidae. We sampled taxa that have been previously suggested to be within, or close to, Malvales (83 sequences), plus additional rosids (26 sequences) and nonrosid eudicots (16 sequences) to provide a broader framework for the analysis. The resulting trees strongly support the monophyly of the core malvalean families, listed above. In addition, these data serve to identify a broader group of taxa that are closely associated with the core families. This expanded malvalean clade is composed of four major subclades: (1) the core families (Bombacaceae, Malvaceae, Sterculiaceae, Tiliaceae); (2) Bixaceae, Cochlospermaceae, and Sphaerosepalaceae (Rhopalocarpaceae); (3) Thymelaeaceae sensu lato (s.l.); and (4) Cistaceae, Dipterocarpaceae s.l., Sarcolaenaceae (Chlaenaceae), and Muntingia. In addition, Neurada (Neuradaceae or Rosaceae) falls in the expanded malvalean clade but not clearly within any of the four major subclades. This expanded malvalean clade is sister to either the expanded capparalean clade of Rodman et al. or the sapindalean clade of Gadek et al. Members of Elaeocarpaceae, hypothesized by most authors as a sister group to the four core malvalean families, are shown to not fall close to these taxa. Also excluded as members of, or sister groups to, the expanded malvalean clade were the families Aextoxicaceae, Barbeyaceae, Cannabinaceae, Cecropiaceae, Dichapetalaceae, Elaeagnaceae, Euphorbiaceae s.l., Huaceae, Lecythidaceae, Moraceae s.l., Pandaceae, Plagiopteraceae, Rhamnaceae, Scytopetalaceae, Ulmaceae, and Urticaceae.

Phylogenetic position and biogeography of Hillebrandia sandwicensis (Begoniaceae): a rare Hawaiian relict

The Begoniaceae consist of two genera, Begonia, with approximately 1400 species that are widely distributed in the tropics, and Hillebrandia, with one species that is endemic to the Hawaiian Islands and the only member of the family native to those islands. To help explain the history of Hillebrandia on the Hawaiian Archipelago, phylogenetic relationships of the Begoniaceae and the Cucurbitales were inferred using sequence data from 18S, rbcL, and ITS, and the minimal age of both Begonia and the Begoniaceae were indirectly estimated. The analyses strongly support the placement of Hillebrandia as the sister group to the rest of the Begoniaceae and indicate that the Hillebrandia lineage is at least 51-65 million years old, an age that predates the current Hawaiian Islands by about 20 million years. Evidence that Hillebrandia sandwicensis has survived on the Hawaiian Archipelago by island hopping from older, now denuded islands to younger, more mountainous islands is presented. Various scenarios for the origin of ancestor to Hillebrandia are considered. The geographic origin of source populations unfortunately remains obscure; however, we suggest a boreotropic or a Malesian-Pacific origin is most likely. Hillebrandia represents the first example in the well-studied Hawaiian flora of a relict genus.

Hidden Neotropical Diversity: Greater Than the Sum of Its Parts

The diversity of tropical herbivorous insects has been explained as a direct function of plant species diversity. Testing that explanation, we reared 2857 flies from flowers and seeds of 24 species of plants from 34 neotropical sites. Samples yielded 52 morphologically similar species of flies and documented highly conserved patterns of specificity to host taxa and host parts. Widespread species of plants can support 13 species of flies. Within single populations of plants, we typically found one or more fly species specific to female flowers and multiple specialists on male flowers. We suggest that neotropical herbivorous insect diversity is not simply a function of plant taxonomic and architectural diversity, but also reflects the geographic distribution of hosts and the age and area of the neotropics.

Datiscaceae revisited: monophyly and the sequence of breeding system evolution

Previous studies of the small angiosperm family Datiscaceae have drawn contradictory con- clusions regarding its monophyly. Clarification of the relationships among the family components is critical to the interpretation of breeding system evolution within this family. Datisca glomerata is the only androdioe- cious member of the otherwise dioecious family and an initial phylogenetic study suggested that this rare breeding system was derived from dioecy in this family. A subsequent, broader scope phylogenetic analysis of Datiscaceae and related families has since suggested that Datiscaceae are not monophyletic, calling into question earlier conclusions regarding the evolution of androdioecy in Datiscaceae. In the present study, the phylogenetic relationships of Datiscaceae and the sequence of breeding system evolution are reexamined. DNA sequences from three sources including nuclear 18S ribosomal DNA, the internal transcribed spacer (ITS) region of nuclear ribosomal DNA, and the chloroplast-encoded rbcL gene were analyzed phylogeneti- cally using parsimony. Results from analysis of rbcL, 18S, and a combined data set all agree that Datiscaceae do not form a monophyletic assemblage. Datisca appears as a sister group to Begoniaceae in all analyses, but the position of sister taxa Octomeles and Tetrameles relative to Datisca and other members of the Cucurbitales is unresolved. The two species of Datisca form separate monophyletic lineages according to ITS analysis, pro- viding no evidence for a progenitor-derivative relationship for the two species. Phylogenetic trees from analy- ses of rbcL and 18S disagree as to whether dioecy or monoecy is ancestral to Datisca, and thus provide no evi- dence as to which sexual system gave rise to androdioecy in D. glomerata, however, there is no evidence for

Phylogenetic Affinities of Datiscaceae Based on an Analysis of Nucleotide Sequences from the Plastid rbcL Gene

Nucleotide sequence data from the large subunit of plastid ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) were used to infer the phylogenetic affinities of Datiscaceae relative to other dicotyledonous angiosperms and to assess whether the family is monophyletic. New rbcL sequence data from members of Datiscaceae and Cucurbitaceae were generated and analyzed with other previously available rbcL sequences. Phylogenetic reconstructions based on parsimony place Datisca closer to representatives of Cucurbitaceae and Begoniaceae than to the other two genera within Datiscaceae. Our results do not support the monophyly of Datiscaceae and suggest that a previous separation of the group at the family level may be warranted. The relationships of the Datiscaceae-Curcurbitaceae-Begoniaceae clade to other groups included in the analysis are unresolved, but analyses with smaller data sets suggest affinities with higher Hamamelidae, among which are several actinorhizal groups. Actinorhizal plants, as a group, may thus be more closely related than has been indicated by recent classification schemes.

Phylogenetic Relationships of Asian Begonia, with an Emphasis on the Evolution of Rain-ballist and Animal Dispersal Mechanisms in Sections Platycentrum, Sphenanthera and Leprosae

Abstract While most Begonia species have a similar fruit morphology that shows adaptations to wind dispersal, a few species have atypical fruits and are adapted to either animal or rain dispersal. Such differences in fruit morphology have traditionally been emphasized in sectional classifications of Begonia and some of the currently recognized sections can only be distinguished using ovary and fruit characteristics. We evaluated the monophyly and evolution of three Asian sections with atypical fruit morphologies: Platycentrum, Sphenanthera, and Leprosae, along with members of nine other Asian sections with fruit morphologies typical of wind dispersed Begonia. A parsimony analysis of nrDNA ITS/ 5.8S sequence data of 46 Asian Begonia species suggests that the members of section Platycentrum, which have fruit morphologies indicative of rain dispersal, evolved from wind dispersed Asian taxa following the colonization of wetter habitats. From within this rain dispersed group, species of section Sphenanthera with fleshy, animal dispersed fruits subsequently evolved on multiple occasions. Members of section Leprosae, which have fleshy fruit, evolved on two separate occasions, in one case independently of the members of the sections Platycentrum and Sphenanthera. As currently recognized, sections Platycentrum, Sphenanthera and Leprosae are polyphyletic.

Distinct Patterns of Symbiosis-Related Gene Expression in Actinorhizal Nodules from Different Plant Families

Phylogenetic analyses suggest that, among the members of the Eurosid I clade, nitrogen-fixing root nodule symbioses developed multiple times independently, four times with rhizobia and four times with the genus Frankia. In order to understand the degree of similarity between symbiotic systems of different phylogenetic subgroups, gene expression patterns were analyzed in root nodules of Datisca glomerata and compared with those in nodules of another actinorhizal plant, Alnus glutinosa, and with the expression patterns of homologous genes in legumes. In parallel, the phylogeny of actinorhizal plants was examined more closely. The results suggest that, although relationships between major groups are difficult to resolve using molecular phylogenetic analysis, the comparison of gene expression patterns can be used to inform evolutionary relationships. In this case, stronger similarities were found between legumes and intracellularly infected actinorhizal plants (Alnus) than between actinorhizal plants of two different phylogenetic subgroups (Alnus/Datisca).

Novel Expression Pattern of Cytosolic Gln Synthetase in Nitrogen-Fixing Root Nodules of the Actinorhizal Host, Datisca glomerata

Gln synthetase (GS) is the key enzyme of primary ammonia assimilation in nitrogen-fixing root nodules of legumes and actinorhizal (Frankia-nodulated) plants. In root nodules of Datisca glomerata (Datiscaceae), transcripts hybridizing to a conserved coding region of the abundant nodule isoform, DgGS1-1, are abundant in uninfected nodule cortical tissue, but expression was not detectable in the infected zone or in the nodule meristem. Similarly, the GS holoprotein is immunolocalized exclusively to the uninfected nodule tissue. Phylogenetic analysis of the full-length cDNA of DgGS1-1 indicates affinities with cytosolic GS genes from legumes, the actinorhizal species Alnus glutinosa, and nonnodulating species, Vitis vinifera and Hevea brasilensis. The D. glomerata nodule GS expression pattern is a new variant among reported root nodule symbioses and may reflect an unusual nitrogen transfer pathway from the Frankia nodule microsymbiont to the plant infected tissue, coupled to a distinctive nitrogen cycle in the uninfected cortical tissue. Arg, Gln, and Glu are the major amino acids present in D. glomerata nodules, but Arg was not detected at high levels in leaves or roots. Arg as a major nodule nitrogen storage form is not found in other root nodule types except in the phylogenetically related Coriaria. Catabolism of Arg through the urea cycle could generate free ammonium in the uninfected tissue where GS is expressed.