The rhizomes of all species in the fern genus Lecanopteris Reinw. contain galleries (hollow chambers) that serve as domatia (homes) for ants. Some aspects of the biology of these species have been elucidated clearly, e.g., adaptations linked to the facultative, co-ecological association between Lecanopteris species and ants have been well established. Other aspects such as the evolutionary relationships between Lecanopteris and other genera of the Polypodiaceae as well as among the thirteen species in Lecanopteris remain widely debated. Diverse leaf and rhizome features have provided numerous autapomorphic characters for diagnosing species and describing subgenera, but there are few synapomorphies to establish reliable interspecific alliances. DNA sequences of the rbcL gene and the trnL-F non-coding region were obtained to test hypotheses of evolutionary history for Lecanopteris and related taxa. Data from each DNA region were considered separately and in combined analyses. The phylogeny obtained from parsimony and maximum likelihood analyses of separate and combined data sets were congruent, but the analyses of combined data sets contained more informative characters, more robust bootstrap support, and better Bremer (“decay”) values than did analyses of the individual DNA regions. Lecanopteris was solidly supported as monophyletic, subgenus Lecanopteris appeared monophyletic, but subgenus Myrmecopteris was paraphyletic. Rhizome morphology, including surface indument, branching patterns, and internal galleries, correlated with DNA-based hypotheses of evolutionary history and interspecific relationships, but aspects of leaf morphology, including blade shape and soral position, appeared homoplastic. Low levels of infrageneric sequence divergence between morphologically distinct species suggest a relaxation of selective pressure on morphology, perhaps owing to the ant/plant association. Narrowly distributed, derived species may have arisen as peripheral isolates from more geographically widespread progenitors.

An unknown plant of the Hymenophyllaceae was discovered in New Caledonia and is described as a new species, Hymenophyllum paniense. The species has unique fronds that resemble hairy caterpillars due to impressive marginal hairs. To elucidate its systematic position, the species was compared with 14 species of Hymenophyllum sensu lato using morphological and molecular approaches. Special attention was focused on the trichomes of the fronds. Molecular phylogeny using continuous sequences of approximately 3,400 bp of chloroplast DNA (including rbcL genes, accD genes and intergeneric spacers) suggested monophyly of this and other Oceanian species bearing multicellular hairs.

A phylogenetic analysis was conducted to examine the monophyly and relationships of the four broadly defined genera of Aristolochiaceae. Seventy-two morphological characters were coded from representatives of these genera and from a broad selection of potential outgroups. The data support monophyly of the Aristolochiaceae and monophyly of the broadly defined genera Aristolochia, Thottea, and Asarum. The genera are grouped into two clades within the family, Thottea Aristolochia and Asarum Saruma. Based on the results of these analyses, Asaroideae, which have been circumscribed by some authors to consist of Saruma, Asarum, and Thottea, are paraphyletic, and should be emended to exclude Thottea.

A synopsis of Veratrum, including commentary on species and character evolution within the genus, is presented. The circumscription and relationships of infrageneric taxa are evaluated using parsimony analyses of ITS (nuclear ribosomal) DNA sequence data of 26 representative taxa. Proposed new infrageneric circumscriptions, strongly supported by tree statistics and topologies, are correlated with potential morphological synapomorphies at the proper level of universality. Based on our analyses, Veratrum is circumscribed broadly (including Melanthium) and divided into two sections and two subsections (most with novel circumscription). This modified infrageneric classification involves reassignment of Veratrum subgenus Pseudoanticlea as subsection Pseudoanticlea. Although interspecific relationships are not highly resolved, the molecular data provide strong support for placing several species previously of unknown affinities and also validate several generalizations concerning character evolution within Veratrum.

The chloroplast-encoded gene rbcL was sequenced in 30 genera of Commelinaceae to evaluate intergeneric relationships within the family. The Australian Cartonema was consistently placed as sister to the rest of the family. The Commelineae is monophyletic, while the monophyly of Tradescantieae is in question, due to the position of Palisota as sister to all other Tradescantieae plus Commelineae. The phylogeny supports the most recent classification of the family with monophyletic tribes Tradescantieae (minus Palisota) and Commelineae, but is highly incongruent with a morphology-based phylogeny. This incongruence is attributed to convergent evolution of morphological characters associated with pollination strategies, especially those of the androecium and inflorescence. Analysis of the combined data sets produced a phylogeny similar to the rbcL phylogeny. The combined analysis differed from the molecular one, however, in supporting the monophyly of Dichorisandrinae. The family appears to have arisen in the Old World, with one or possibly two movements to the New World in the Tradescantieae, and two (or possibly one) subsequent movements back to the Old World; the latter are required to account for the Old World distribution of Coleotrypinae and Cyanotinae, which are nested within a New World clade.

All diploid species of Hordeum have been included in phylogenetic analyses of four molecular data sets supposedly from three different linkage groups. Two data sets stem from the nuclear genome: partial DMC1 (disrupted meiotic cDNA1) sequences (chromosome 3 in H. vulgare) and partial EF-G (elongation factor G) sequences (chromosome 2 in H. vulgare). The other two data sets are RFLP data and sequence data, rbcL (ribulose-1,5-bisphosphate carboxylase/oxygenase), from the plastid genome. Incongruence length difference tests show that the two nuclear and the two plastid data sets, respectively, are congruent, whereas the nuclear data and the plastid data are incongruent. The greatest incongruence is caused by the two Eurasian subspecies of H. marinum. The nuclear data support monophyly of the species, but the plastid data group one of the subspecies among the American taxa. The explanation is most likely lineage sorting. Based on a combined analysis of all data sets a new infrageneric classification of Hordeum including only monophyletic groups is presented. One new taxon, Hordeum L. sect. Sibirica (Nevski) G. Petersen & Seberg, stat. nov., is proposed. The distribution of selected morphological characters is discussed.

During preparation for a revision of the genus Paspalum for America, two new taxa from Brazil were recognized as previously undescribed species. Paspalum plowmanii from Bahia, Goiás, and Mato Grosso is related to P. macranthecium. from which it differs by its non-stipitate spikelets, with upper glume 3/4 the length of the spikelet, and by having a membranous upper glume and lower lemma. Paspalum filgueirasii from Goiás, Brazil, is related to P. proximum Mez, from which it differs by having a single and erect raceme. Both species are described, illustrated, and compared with putatively related species. A key to the new species and related taxa of Paspalum is also presented.

A new species of Poaceae from Brazil, Tridens riograndensis Acedo & Llamas, is described and illustrated. Complete morphological and anatomical descriptions are made. The new species can be distinguished from other species of Tridens by possessing glumes with obtuse apices, paleas that are shorter than the lemma, and spiciform panicles. A key to morphologically similar species is offered.

In recent DNA-based cladograms of dicotyledons, Aextoxicaceae (one sp., Chile) and Berberidopsidaceae (three spp., Chile and Australia) form an isolated clade, Berberidopsidales, basal to rosids and asterids. Until recently, Aextoxicaceae had been placed in Euphorbiales, Berberidopsidaceae in Violales. Light microscopy and scanning electron microscopy (SEM) studies of wood of the two families show numerous shared primitive features: perforation plates with numerous bars and extensive pit-membrane remnants, lateral wall pitting of vessels scalariform to transitional, tracheids present; long vessel elements and tracheids, low F/V ratio; diffuse axial parenchyma; and Heterogeneous Type I rays. Features reported for the first time include crystals with various degrees of encapsulation in ray cells (Aextoxicon), pit membrane remnants in perforations (Berberidopsis, previously reported in Aextoxicon), and presence of narrow latewood vessels the perforation plates of which can bear pit membranes (Berberidopsis). Probable synapomorphies of the two families include marked difference between multiseriate parts (cells procumbent only) and uniseriate parts (cells square to upright), and presence of dark-staining deposits in axial parenchyma and rays. Cladistics does not use symplesiomorphies, which are numerous between the two families, to group closely-related families at clade tips. Ecological and habital adaptations of woods of the two families are briefly considered.

Phylogenetic relationships within Polygonaceae, with an emphasis on Polygonum and segregate genera (e.g., Emex, Persicaria, Polygonella), are investigated using sequence data from the chloroplast gene rbcL. The results show the currently recognized subfamilies are likely not monophyletic. Polygonum as currently recognized is paraphyletic. Three strongly supported clades of Polygonum s.l. were found. Contained within these three clades of Polygonum s.l. are representatives of Atraphaxis, Bistorta, Koenigia and Persicaria. Other strongly supported clades found are Coccoloba, Eriogonum, Fagopyrum, Rumex and Triplaris. Patterns of character evolution were studied by mapping characters onto the phylogeny. A woody habit likely evolved multiple times within the family (in Atraphaxis, Koenigia, Muehlenbeckia, Polygonella and in the ancestor to the Eriogonum–Brunnichia clade). Quincuncial aestivation likely evolved early in the history of the family with four subsequent losses in the Rumex–Oxyria clade, Muehlenbeckia, the Eriogonum clade, and the Triplaris clade.

Malesherbiaceae are an angiosperm family allied with Turneraceae and Passifloraceae. The family contains 24 species in the single genus, Malesherbia, and is distributed in the arid Andes and coastal deserts of Chile, Peru, and Argentina. Although there are several morphologically cohesive groups of species in the genus, no subgenera or sections have been recognized. A phylogeny for the family was reconstructed from ITS sequence data using parsimony, implied weights, successive approximations, and maximum likelihood analyses. Parsimony, implied weights, and successive approximations yielded almost identical topologies having four strongly supported clades and one weakly supported clade. Maximum likelihood analysis using model TrNef G resulted in a topology showing the same four well supported clades, but the root moved to break the monophyly of the fifth clade. The four well-supported clades each contain morphologically similar species, and the fifth clade also shows some morphological cohesion. The five clades are morphologically divergent and may be recognized taxonomically at the level of section. Five sections, Albitomenta, Cyanpetala, Malesherbia, Parvistella, and Xeromontana, are described. A key to the sections is provided.

A new genus of arborescent violet, Hekkingia, is described from Neotropical lowland rainforest near Cayenne in northeastern French Guiana. Racemose inflorescences, fully fused filaments and rudimentary dorsal connective appendages place the only known species, Hekkingia bordenavei, near the genus Paypayrola, while strongly tuberculate capsules ally it also to Amphirrhox, the two genera comprising the Subtribe Paypayrolinae to which the new genus is tentatively assigned. Hekkingia shares scarcely differentiated corollas with quincuncial aestivation, very large obovate sepals, red to pink capsules and carunculate seeds with few other genera (but not in this combination), whereas its basally cauliflorous habit, very large bracts and pedicel bractlets are unique in the family. A key to genera of the Violaceae provides a context for this French Guianan novelty.

Phylogenetic relationships among members of the subtribe Abutilinae and particularly the taxa in the Sida generic alliance are currently poorly understood. The internal transcribed spacers of nuclear ribosomal DNA (ITS1 ITS2) from 58 species (51 new sequences) of Malvaceae were sequenced. The ITS data show that species from sects. Cordifoliae, Ellipticifoliae, Muticae, Sida, Spinosae, and Stenidae fall within a well-supported Sida core clade. This clade, which also includes the genus Dendrosida, groups species with a basic chromosome number of seven. Several species are placed outside of the Sida core, confirming preliminary suggestions of the paraphyly of this group based on morphological and cytogenetic evidence. Other sections, such as sect. Nelavagae, are monophyletic and sister to the Sida core, whereas sect. Malachroideae is placed outside of the Sida core in an unresolved position. Meximalva and Sidastrum as well as an Australian group of Sida species form a well-supported clade. Sida hookeriana and S. hermaphrodita are placed in a clade and associated with Sidasodes, removed from the Sida core, indicating a position much closer to subtribe Malvineae than previously suggested. Molecular evidence does not provide clear limits to the Sida generic alliance as currently circumscribed.

Monophyly of the neotropical plant genus Alloplectus (Gesneriaceae) was tested using maximum parsimony and maximum likelihood phylogenetic analyses of molecular sequence data from the nuclear ribosomal (nrDNA) internal transcribed spacer region (ITS). As currently circumscribed, Alloplectus is polyphyletic and includes taxa in three different clades. The clade that contains the type species is described as Alloplectus sensu stricto and is characterized by the presence of resupinate flowers. The Alloplectus s.s. clade is weakly supported as the sister-group to Columnea. A separate clade of non-resupinate “Alloplectus” species nests within a paraphyletic Drymonia. A third taxon, Alloplectus cristatus, endemic to the Lesser Antilles and northwestern South America, is also resupinate and unresolved in a basal polytomy, removed from the other species of Alloplectus. The fourth taxon, Alloplectus peruvianus, which was originally described as Columnea peruviana, is strongly supported as nesting within Columnea. Resupination of flowers is an important feature that has not been previously reported and should be recognized as a morphological synapomorphy for Alloplectus s.s. Within the tribe Episcieae, flower resupination is a convergent feature that is independently derived in the Alloplectus s.s. clade, Alloplectus cristatus, and a clade comprising some Nematanthus species.

Recent advances in understanding the tectonic and paleoenvironmental history of the Caribbean region allow formulation of biogeographic and evolution/speciation models within an improved physical context. Support is developing for a new ‘maximist’ model of geological history suggesting that the Greater Antilles originated as a submerged volcanic island arc in the present Isthmian region during the Early Cretaceous [Valanginian; ∼130 m.y. (million years ago)] and moved more than 1000 km to their present location. Geologic investigations are not always concerned with whether an arc is submerged or emergent, but the proto-Greater Antillean arc began colliding with the Bahamas Platform in the Paleocene/earliest Eocene (∼56 m.y.), and the principal period of emergence allowing terrestrial flora and fauna to colonize was in the middle Eocene (∼49 m.y.). Early emergence was during the later phases of the hothouse interval of the Late Cretaceous through the early Eocene, which was followed by an intermediate period when climates fluctuated between non-glacial and (marginally) glacial conditions (middle Eocene through the early Miocene), and culminated in the icehouse interval of the late Tertiary and Quaternary Periods. The recent geological/paleoenvironmental models still constitute, however, a broad spectrum of possibilities for biogeographic-evolutionary-speciation events within which specialists must formulate the most probable pathway(s) for individual taxa.

Morphological data and sequences from the nuclear ribosomal ITS region, and the chloroplast trnL intron and matK locus were sampled from robinioid legumes to infer phylogenetic relationships. The monophyletic robinioid clade includes 11 genetically and often morphologically distinct subclades ranked as genera with the following well supported higher level relationships: ((Hebestigma, Lennea), ((Gliricidia, Poitea), (Olneya, Robinia, Poissonia, Coursetia, Peteria, Genistidium, and Sphinctospermum))). In order to render all 11 robinioid genera monophyletic, the genus Hybosema is synonymized with Gliricidia, and the genus Poissonia is resurrected to accommodate four morphologically disparate species previously classified in Coursetia. Three new combinations are required to accommodate these two generic recircumscriptions: Gliricidia robustum, Poissonia heterantha, and Poissonia weberbaueri. Ages of clades and evolutionary substitution rates are derived from a rate-smoothed Bayesian likelihood approach on sequences from the ITS region and the matK locus. Time constraints are derived from the Tertiary fossil wood species Robinia zirkelii, which shares apomorphic wood characters with the Robinia stem clade. The Cuban endemic Hebestigma is estimated to have diverged at least 38 Ma from its Mesoamerican sister genus Lennea, whereas the Greater Antillean Poitea is estimated to have diverged at least 16 Ma from its continental sister Gliricidia. This study reveals that sequences from the ITS region are amenable to exhaustive taxon sampling because of the high levels of variation at and below the species level. The evolutionary substitution rate for the ITS region is estimated at 3.1–3.5 x 10^–9 substitutions/site/year, approximately an order of magnitude faster than that estimated for the matK locus.

The Lythraceae contribute eight genera and 41 species to the flora of the Antilles. Two genera, Ginoria and Haitia, and twenty-two species are endemic to the region. A summary of the distribution of each genus among the islands of the Greater Antilles is presented, together with an estimate of center of origin and mode and direction of introduction. Cuphea (15 species) and Ginoria (13 species) are best represented. Results of phylogenetic analyses for Rotala, Cuphea, and Ginoria aid in understanding the nearest relationships and geographic sources of the Antillean members of these genera. They suggest that Rotala was introduced twice from different directions and Cuphea was introduced from eastern South America a minimum of five to eight times into the Greater Antilles and at least three times into the Lesser Antilles. A paraphyletic Ginoria and Haitia, which is nested within the most derived species of Ginoria, are the result of adaptive radiation in situ in Cuba and Hispaniola from an undetermined ancestor. The biogeographic patterns of the Lythraceae in the Caribbean primarily have been established following chance, multiple, long-distance dispersal events from multiple directions. Highly vagile seeds and self-compatibility most likely enhanced their successful dispersion and establishment. Vicariance is not required to explain the distribution of Lythraceae in the Antilles.

The phylogenetic relationships within Styrax series Valvatae were estimated with DNA sequence data from the internal transcribed spacer region of nuclear ribosomal DNA to test hypotheses bearing on the historical biogeography of the Antilles. The results provide evidence for three dispersal events within Styrax to the Antilles, one from southern North America, the other two from South America. The data do not support a strict Greater Antillean vicariance scenario for Styrax. Vicariance between the Greater Antilles and southern North America without immediate prior dispersal would require a more basal position of Styrax ochraceus than that recovered, although low branch support values in the relevant portion of the tree do not preclude this possibility. Dispersal of Styrax from South America to the Greater Antilles could have proceeded across oceanic barriers, or more likely through GAARlandia. Styrax obtusifolius in Cuba and Hispaniola and the strictly South American Foveolaria clade have evolved small flowers and the gynodioecious condition independently. The predominance of microscopic pollinators in the Cuban fauna may have impelled the evolution of small flowers in Styrax obtusifolius. The data suggest that the Antilles have played little if any role in the intercontinental dispersal of Styrax.

Exostema (Rubiaceae) comprises 25 neotropical woody species, ranging from western South America and Mesoamerica to the West Indies, with 19 species occurring in Cuba and Hispaniola. Biogeographical hypotheses based upon a phylogenetic analysis of morphological data depict a South American origin for the group, with species radiations in the Greater Antilles. Molecular phylogenetic analyses were conducted using ITS and rbcL sequence data for a sample of 14 species of Exostema and nine species from eight closely related genera. Results indicate that Exostema is paraphyletic with respect to Coutarea, Erithalis, and Chiococca. Hypotheses invoking independent South American origins for subclades of Exostema are not supported. Coutarea and the South American Exostema species form a clade sister to the Caribbean Exostema species with terminal inflorescences. Relationships among axillary flowered Exostema species are not well resolved. Distribution, ecology, and seed traits indicate over-water dispersal is important for wide-spread species (e.g., E. caribaeum). Sister species relationships between the Cuban and Hispaniolan endemics E. salicifolium and E. acuminatum are strongly supported. Disjunctions between various regions of Cuba and Hispaniola are consistent with geohistorical connections between these composite islands. Biogeographical patterns found in Exostema are similar to those reported for other Caribbean plant groups, with vicariance detected in certain cases, and dispersal often indicated by distribution, ecology and phylogeny for many taxa.

Ernodea Swartz (Tribe Spermacoceae) and Erithalis P. Browne (Tribe Chiococceae) are two genera of Rubiaceae that are endemic to the Caribbean, composed of four and nine species, respectively. Molecular phylogenies were analyzed in a biogeographic context using Brooks Parsimony Analysis (BPA) and Fitch Parsimony methods. A geographic association of Cuba and Dominican Republic was supported by area cladograms generated by BPA for Erithalis and by the combined data matrix. Additionally, the two parts of Hispaniola (Dominican Republic and Haiti) appear in two different places on the cladogram suggesting that Hispaniola represents a composite of geological areas. Fitch analyses support a Greater Antillean origin for Erithalis, however, it was ambiguously resolved for Ernodea. Overall, biogeographic analyses explain the present-day distribution of Ernodea as a product of dispersal, whereas a combination of vicariance and dispersal events appears to be involved in Erithalis biogeographical history. In general, the study implies that trans-oceanic seed dispersal plays an important role in the distribution of these genera, in addition to Tertiary vicariance events for Erithalis.

Coeloneurum, Espadaea, Henoonia, and Goetzea are shrubs and trees that are endemic to the islands of Cuba, Hispaniola, and Puerto Rico in the Greater Antilles. A phylogenetic analysis was conducted to elucidate the evolutionary relationships among them and with other major lineages of the Solanaceae. DNA sequences of the chloroplast genes ndhF, rbcL, and trnL-trnF intron and intergenic spacer were obtained for twenty two taxa and sequences of the nuclear rDNA ITS region were obtained for eight taxa comprising a data set of over 5,000 bp. The inferred phylogeny groups the Antillean genera together with the South American Metternichia and Duckeodendron in a clade within the Solanaceae, pointing to a broader circumscription of the Goetzeoideae. Both chloroplast and nuclear datasets find the following relationships among the Antillean taxa: (Coeloneurum (Henoonia (Espadaea, Goetzea))). The South American genera Metternichia and Duckeodendron are the first and second sister groups, respectively, to the Antillean genera. The close relationship of Metternichia to the Antillean genera also is supported by pollen morphology. Phylogenetic inference suggests that the Antillean taxa first occuppied xeric environments and evolved into more mesic habitats. Floral characteristics indicate evolution of pollination systems from nocturnal, insect-pollination in Duckeodendron and Metternichia to diurnal, bird-pollination in the Antillean genera. Duckeodendron and the Antillean genera produce drupes, but their contrasting morphology and anatomy suggest that these fruit types originated from separate evolutionary events.

Increased attention is being given to the preservation of paleontological sites, collections, and other archival resources that record stages in the history of the Earth's biota. The success of these efforts will be enhanced with greater recognition that the extant biota and its immediate past stages are part of a continuum (e.g., deep-time floras). An expected consequence of this view would be to bring identification of the fossil representatives under closer scrutiny by specialists in the extant lineages. Improvement in the quality and reliability of the paleontological database benefits the use of the information both in its biological applications (e.g., historical biogeography, calibration of molecular clocks, construction of area cladograms) and in geological investigations (e.g., paleoenvironmental reconstructions). Inherent in the increasing recognition of time as important in these considerations is continued access to the remarkably few fossil-bearing sites, especially in tropical America, that have provided virtually all of the existing museum specimens used in investigations for anchoring lineages in time and place. The destruction of these sites before additional collections can be made, and before they can be studied by modern methods of identification and interpretation, is an impediment to understanding the modern biota much like the destruction of sites with high concentrations of extant endemic taxa (hotspots). The relatively rare sites providing archival material for revealing the history of the Earth's vegetation should be relocated, studied more collaboratively by paleobotanists and taxonomists, and preserved. Preliminary efforts are underway to conserve three collection sites (San Sebastian flora, Puerto Rico; Sanchez flora, Dominican Republic; Yumarí flora, Cuba), and to develop a project whereby paleobotanists and taxonomists will work collaboratively to establish a reliable database of fossil material.