To elucidate the taxonomic status of Ruppia drepanensis Tineo ex Guss. (Alismatales, Ruppiaceae), we performed morphological analysis and DNA barcoding of historical materials (including the lectotype) and fresh samples (including those from a recently discovered population near the locus classicus in Sicily, Italy). We conclude that R. drepanensis is a separate species, closely related to R. spiralis L. ex Dumort., that occurs in temporary inland waters from the western to central sectors of the Mediterranean region. We also highlight the importance of vouchers and the need to link molecular investigations to field, ecological, and morphological investigations.

This paper is the first in a projected series of publications treating the Chenopodiaceae in South America. We present here a taxonomic revision of subfamilies Betoideae, Camphorosmoideae, and Salsoloideae in South America, where all representatives of these subfamilies are introduced. Our research is based on the study of herbarium material, type specimens, digital images, original publications, and field observations. The South American Chenopodiaceae flora includes only Beta vulgaris L. from Betoideae, Bassia hyssopifolia (Pall.) Kuntze, Bassia scoparia (L.) A. J. Scott, and Maireana brevifolia (R. Br.) P. G. Wilson from Camphorosmoideae, and Salsola kali L., Salsola tragus L., and Soda inermis Fourr. from Salsoloideae. Lectotypes for Echinopsilon reuterianus Boiss., Kochia alata Bates, K. parodii Aellen, K. parodii var. elongata Aellen, K. parodii var. densa Aellen, K. parodii var. glabrescens Aellen, and Suaeda sieversiana Pall. are designated here, as well as a second-step lectotype for K. brevifolia R. Br. The distribution of all species is updated based on the revision and proper identification of many herbarium specimens and field observations. The distribution of M. brevifolia in Chile is here expanded. New synonyms for Bassia scoparia are proposed. A preliminary key to the genera of Chenopodiaceae in South America is also presented.

The subcosmopolitan genus Gentianella Moench (Gentianaceae, Swertiinae), with more than 170 currently accepted species in South America alone, is one of the emblematic examples of major and rapid radiations in the Andes. However, the taxonomy of South American Gentianella is far from being resolved. Over a century has passed since the publication of the last comprehensive treatment by Ernst Gilg in 1916. Using flow cytometry, the genome size of 115 accessions of 39 species, of which 37 were from South America, was measured, with the objective to assess the taxonomic utility of that trait. Also, the relationships of genome size with environmental factors such as mean annual temperature and precipitation, as well as the life history traits, habit, reproduction, habitat, and elevational belt were examined. The genome size values of the investigated South American accessions fell into two size classes, ranging from 2C = 7.60 pg to 11.30 pg and from 2C = 16.54 pg to 18.34 pg. The latter size class contained only accessions of G. briquetiana (Gilg) T. N. Ho & S. W. Liu. These accessions, and a further one of G. limoselloides (Kunth) Fabris with an intermediate value of 2C = 14.71 pg, were inferred to be octoploid. Genome size was not correlated with temperature, precipitation, habit, or elevational belt. By contrast, significant differences in genome size between groups were found regarding habitat and reproduction. Furthermore, genome size of one of the informal taxonomic groups of Gilg (Barbatae) differed from that of the remaining groups. However, this finding is of doubtful taxonomic relevance because of inconsistencies in the application of Gilg's defining criterion of Barbatae, i.e., the presence of trichomes inside the corolla tube. Based on the overall results, it is concluded that genome size is not a taxonomically useful trait in South American Gentianella. Still, the data offer a first view on genome size variation and evolution in this diverse but poorly studied group.

We present an annotated checklist of the 14 species of Drypetes Vahl (Putranjivaceae) that occur in Liberia, as well as distribution maps of the country for each. Three species are new records for Liberia: D. floribunda (Müll. Arg.) Hutch., D. klainei Pierre ex Pax, and D. laciniata (Pax) Hutch. In addition, we describe a new species, D. liberica Quintanar & D. J. Harris, an understory shrub or small tree that is endemic to Liberia. Based on the specimens studied, we provide types for all names, including 14 newly selected lectotypes, in order to stabilize the nomenclature of the taxa involved. We also lectotypify one species, D. leonensis Pax, that for the moment we do not cite for Liberia, but the name has been the source of confusion with a species that does occur in the country.

Since the founding of the Missouri Botanical Garden (MBG) in 1859, the emphasis on research and the distribution of research findings in botany has been, and will remain, one of the central components of the garden's mission. Likewise, Washington University in St. Louis (WUSTL), the MBG's partner in graduate programs since 1885, has had a continuous and similarly strong emphasis on research and the dissemination of research findings in plant science through publications. Since the beginning of this partnership, the ongoing extension of common research themes has been critical, through the early focus on traditional botanical studies (1885–1930) at the MBG, the move toward a focus on physiology and the emerging field of ecology (1930–1960), and eventually the shift to the study of biochemistry, molecular biology, and genomic studies in plant science (1960–present), primarily at WUSTL. For more than 135 years (1885–2020), this St. Louis–based collaboration has had a prominent place in the region's rich history in plant science. In recent years, collaboration with and contributions from other St. Louis–area degree-granting institutions in the field (such as Saint Louis University [SLU] and the University of Missouri–St. Louis [UMSL]) have steadily increased. Couple this with the addition of the Donald Danforth Plant Science Center (Danforth Center) in 2000, which, like the MBG, has undertaken research and training in plant science, and you now have impressive depth and diversity within St. Louis's plant science offerings. As a result, both organizations train students and carry out peer-reviewed research funded by the same agencies (i.e., National Institutes of Health, National Science Foundation, U.S. Department of Agriculture) as the region's degree-granting institutions. Every year, a significant number of master's degree and Ph.D. graduates in this consortium comprise an impressive pool of talent available for postdoctoral training, research, and teaching positions, as well as employment in government entities and private and public life science corporations. To this end, St. Louis has one of the largest concentrations of plant science Ph.D.'s in the world (with more than 1,000 such individuals residing in the region [BioSTL, 2018]), as well as a broad diversity of disciplines represented. In addition, the faculties at both the Danforth Center and MBG frequently serve as adjunct members of university departments and as advisors to graduate students, and greatly increase the breadth of topics offered in the St. Louis plant science community, particularly in areas not directly supported by the universities. Both organizations contribute to an increasingly important part of this ecosystem. Below is a short history of the relationship between the MBG and WUSTL, and how this collaboration, primarily through graduate research education, has been foundational for the St. Louis area's impressive plant science ecosystem. This is not a detailed review of the science generated by these organizations, but rather an account of the initial events and leaders that led to the region becoming the present-day hub for plant science.

A recent molecular phylogenetic study revealed that Diospyros L. sect. Forbesia F. White, originally circumscribed to encompass two species from Africa and several from the Mascarene Islands (White, 1980), also includes a group of species endemic to Madagascar. The taxonomy of the Malagasy members of the section has not been examined since Perrier de la Bâthie's 1952 treatment in the Flore de Madagascar et des Comores, and in the intervening seven decades, numerous specimens have been collected that cannot be identified based on the key provided. This revision presents a significantly updated taxonomy of Diospyros sect. Forbesia in the Malagasy region in which 18 species are recognized, 14 of which are newly described and illustrated, including one new species restricted to Mayotte Island in the Comoro archipelago. An identification key is provided as well as IUCN risk of extinction assessments, which indicate that two species are Critically Endangered, four are Endangered, and seven are Vulnerable, while one is Near Threatened and four are Least Concern. A full description is provided for each species, along with color photos; each of the new species is also illustrated with a line drawing.

A revised assessment of Croton L. sect. Geiseleria (A. Gray) Baill. is provided. The section as now circumscribed includes 84 species ranging across warm areas of the Americas. A nuclear ITS phylogeny of 150 accessions from 83 species and a chloroplast trnL-F phylogeny of 89 accessions from 65 species were generated to confirm correct phylogenetic placement of the species and to determine if any species previously included in the section should now be excluded. Seven new species are described, and we present a taxonomic synopsis that lists all currently accepted species along with their synonyms, distributions, and pertinent comments. We also recognize four subsections within Croton sect. Geiseleria and list their corresponding species. Based on both morphological and molecular criteria, we now recognize C. lagunillae Croizat as a distinct species, rather than as a variety of C. guildingii Griseb. (now treated as C. suavis Kunth), and we treat C. ramillatus Croizat var. magniglandulifer V. W. Steinm. as a species, C. magniglandulifer (V. W. Steinm.) B. W. van Ee. We also exclude C. tetradenius Baill. from Croton sect. Geiseleria (A. Gray) Baill. along with related species such as C. pulegiodorus Baill. and C. leptobotryus Müll. Arg., which are either members of Croton sect. Adenophylli Griseb. or else may merit new sectional status. We also exclude C. waltherioides Urb., although it is not clear to which section of Croton it belongs.

Citharexylum L. belongs to the recently circumscribed tribe Citharexyleae of the Verbenaceae, along with Rehdera Moldenke. It comprises around 50 to 60 species of trees and shrubs growing in the Neotropics. A complete taxonomic revision of Citharexylum in South America is here provided for the first time. Thirty taxa are present in South America, 27 of these are endemic, and three of them also grow in Central America. Detailed morphological descriptions are given for each taxon, as well as a key for their identification; illustrations, photographs, or iconography; updated synonymy; geographic distribution maps and ecological notes; list of selected specimens; and discussion about the relationship among closely related taxa. A new status, C. poeppigii Walp. var. anomalum (Moldenke) N. O'Leary, and a new combination, C. dentatum D. Don var. canescens (Moldenke) N. O'Leary, are proposed. Thirty-five new synonyms are suggested, and lectotypes are designated for C. fruticosum L. var. brittonii (Moldenke) I. E. Méndez, C. laurifolium Hayek, and Rauvolfia spinosa Cav.

Chromosome numbers and ploidy levels of 24 accessions of 17 species of tribe Panicoideae from Argentina, Cuba, and Brazil are given. Most of the studied species are endemics. The studied taxa are: Axonopus aureus P. Beauv., Dichanthelium aequivaginatum (Swallen) Zuloaga, D. stipiflorum (Renvoize) Zuloaga, D. surrectum (Chase ex Zuloaga & Morrone) Zuloaga, Homolepis isocalycia (G. Mey.) Chase, Paspalum arenarium Schrad., P. blodgettii Chapm., P. capillifolium Nash, P. coryphaeum Trin., P. distortum Chase, P. durifolium Mez, P. lindenianum A. Rich., P. oligostachyum Salzm. ex Steud., P. pumilum Nees, P. scutatum Nees ex Trin., P. strigosum Döll ex Chase, and Plagiantha tenella Renvoize; of these, the chromosome numbers of D. aequivaginatum, D. stipiflorum, D. surrectum (n = 9), Homolepis isocalycia (n = 20), Paspalum capillifolium, P. distortum, P. lindenianum, P. oligostachyum, and P. strigosum (n = 10) are presented for the first time. A new diploid cytotype (n = 10) for Paspalum blodgettii was found.

A taxonomic revision of the genus Podagrostis (Griseb.) Scribn. & Merr. is presented, including two new combinations: P. meridensis (Luces) A. M. Molina & Rúgolo and P. novogaliciana (McVaugh) A. M. Molina & Rúgolo. Podagrostis bacillata (Hack.) Sylvester & Soreng constitutes a new report for Colombia. Information regarding synonymy, geographical distribution, habitat, iconography, and vernacular names is provided along with complete illustrations and a list of additional specimens examined. A key for the identification of the species is included as well as a comparative table based on macro- and micromorphological data. The anatomical character of Trichodium net on lemma epidermis, as well as its diagnostic value, is discussed in species of Podagrostis and most related genera (e.g., Agrostis L., Chaetotropis Kunth, and Polypogon Desf., among others).

The genus Mimosa L. is well known for its high morphological variability and the presence of taxonomic complexes—groups of taxa that are not adequately circumscribed and are therefore in continuous revision. For this study, we analyzed flowers from 28 different taxa in Mimosa sect. Calothamnos Barneby and five vegetatively similar taxa from Mimosa sect. Mimosa. We observed three calyx shapes and four (glabrous or pubescent) calyx border types, as well as describe glandular trichomes on the calyx border for the first time in section Calothamnos. While the corolla exhibits only two shape types, trichomes on the corolla are much more diverse, as we found one simple and 11 branched trichome types in diverse orientations and dispositions. Given the taxonomic value of trichomes and profuse terminology in different families, we focused on the detailed description of their micromorphology, type, and shape, finding morphological differences between trichome types, which is an easy way to adequately compare them between even unrelated taxa. Our results using trichome types on the corolla are consistent with the original differentiation of sections Calothamnos and Mimosa. Flower micromorphology also provides characters to distinguish species, groups of species, and varieties within section Calothamnos and could be useful in a future taxonomic treatment of the section. We also found that some floral features, such as inflorescence color and stamen fusion, are associated with the characters used in this study.

This paper is the second in a series treating the Amaranthaceae s.l. in South America. We present here a taxonomic revision of tribes Salicornieae and Suaedeae (subfamily Salicornioideae) based on the study of herbarium material, type specimens, digital images, original publications, and field observations. The South American Amaranthaceae s.l. flora includes Allenrolfea Kuntze, Heterostachys Ung.-Sternb., Mangleticornia P. W. Ball, G. Kadereit & Cornejo, and Salicornia L. from Salicornieae, and Suaeda Forssk. ex J. F. Gmel. from Suaedeae. Lectotypes for seven names are here designated. The distribution of all species is updated based on the revision and proper identification of many herbarium specimens and field observations. A new synonym for Salicornia neei Lag. is here proposed.

Crenea Aubl. (Lythraceae) is a ditypic genus of subshrubs occurring in mangrove vegetation on the coasts of northern South America. Phylogenetic analyses based on morphology have offered unresolved and conflicting phylogenetic positions for the genus in the family. This study presents the first molecular sequences for Crenea, from nrITS, rbcL, trnL, trnL-F, and matK regions. Molecular phylogenetic analyses find full support for Crenea within Ammannia L., a relationship not previously recognized. Ammannia is a globally distributed genus of terrestrial to amphibious herbs mostly occurring in freshwater marshes and wetlands. It was recently reconfigured based on phylogenetic evidence to include the genera Nesaea Comm. ex Kunth and Hionanthera A. Fern. & Diniz. The transfer of Crenea to Ammannia further extends the morphological, ecological, and biogeographical diversity of Ammannia and provides the final evidence defining Ammannia as a monophyletic lineage of the Lythraceae. A revised circumscription of Ammannia s.l. adds several new morphological character states and the first species in the genus restricted to mangrove vegetation. Two changes in taxonomic status are made: Ammannia maritima (Aubl.) S. A. Graham, P. W. Inglis, & T. B. Cavalc., comb. nov., and Ammannia patentinervius (Koehne) S. A. Graham, P. W. Inglis, & T. B. Cavalc., comb. nov. The new combinations are described, a list of exsiccatae examined is provided, and the effects of the reconfiguration to the morphology and biogeography of the genus are detailed.

The Neotropical genus Pentacalia Cass. (Compositae, Senecioneae) is distributed from southern Mexico to northwestern Argentina, plus two disjunct species that thrive in Brazil. Most species diversity occurs in the montane forests of Colombia, Ecuador, and Peru. It comprises scandent woody plants characterized by displaying alternate leaves (opposite in three species), involucres with supplementary bracts, usually yellow ray florets (when present), sagittate to caudate anther bases, and truncate to obtuse style branches with a crown of sweeping trichomes (sometimes with a tuft of longer trichomes, but not strictly penicillate). The Bolivian species were revised for the first time by Cabrera (1985), who treated the group under Senecio L. sect. Streptothamni Greenm. Because of the subsequent addition of new species and the need of taxonomic arrangements, an updated synopsis of the genus recognizing 18 species is presented. The names P. brittoniana (Hieron.) Cuatrec. and P. miguelii (Cuatrec.) Cuatrec. are synonymized with P. psidiifolia (Rusby) Cuatrec., as well as P. inquisiviensis H. Rob. & Cuatrec. with P. cardenasii (Cuatrec.) Cuatrec. and P. sailapatensis (Cuatrec.) Cuatrec. with P. urubambensis (Cabrera) Cuatrec. Seven names are lectotypified and an epitype is designated for the name P. zongoensis (Cabrera) J. Calvo. The new species P. viburnifolia J. Calvo & A. Fuentes is described. Revised nomenclature, succinct descriptions, taxonomic discussions, lists of specimens examined, and distribution maps are provided for all accepted species, in addition to an identification key. Pictures of living plants are also presented for eight species.

Morphological boundaries between South American species of Euphrasia L. are controversial, rendering determination of specimens an arduous task. In this context, a comprehensive taxonomic revision of Euphrasia in South America is here provided for the first time. This study, based upon a classical morphological study of ca. 400 herbarium specimens, supports the recognition of eight species and one subspecies distributed in the Andean regions of Argentina, Bolivia, and Chile. From among native species, six belong to section Trifidae Benth. and one to the monotypic section Paradoxae Pugsley, endemic to Juan Fernández Islands; one adventive species, E. officinalis L., belongs to the section Euphrasia. The previously misunderstood presence of E. cockayniana Petrie is here untangled, and, consequently, the species is excluded from South America. A key to all Euphrasia taxa in South America, plus morphological descriptions, nomenclature items, geographical distribution and maps, habitat notes, illustrations, photographs, and discussion notes are included for the nine taxa. Eleven names are here synonymized, and lectotypes are designated for E. andicola Benth., E. debilis Wettst., E. flavicans Phil., E. intricata Phil., and E. philippii Wettst. Euphrasia andicola is reported for the first time for Argentina. This collaborative effort will represent a baseline for further investigations on Euphrasia in South America.

Floral colors and odors are evolutionary strategies used by plants to attract pollinating animals and may be absent in mostly anemophilous groups, such as Cyperaceae. However, considering that insects are floral visitors of some Rhynchospora Vahl species, the objective of this study was to characterize the floral traits and pollination systems within this genus. We analyzed 16 Rhynchospora species with regard to flower morphology, colors of floral structures, floral scents, pollen vectors, and pollination systems. We verified factors that can favor abiotic or biotic pollination in a continuum of floral traits in Rhynchospora. The flower morphology of R. dissitispicula T. Koyama, with inconspicuous brown spikelets in open panicles, is interpreted as a complete adaptation to anemophily. Conspicuous floral traits in Rhynchospora were distinguished from the background by bees. Some species also emit floral volatiles, and we made the first record of floral scent chemistry within the genus. Most of the compounds emitted by these species are known as attractants to many floral-visiting insects. Bees, beetles, and flies visited species with conspicuous floral traits and contributed to fruit set. The investigated floral traits form a continuum across the different pollination systems in Rhynchospora, from anemophilous to ambophilous and then to entomophilous representatives.

An assessment of the extinction risk of the endemic plants from the Yucatán Peninsula Biotic Province (YPBP) was performed based on distributional data (B criteria of the IUCN) using the GeoCAT tool. The YPBP is located in southeastern Mexico and comprises the Mexican states of Campeche, Quintana Roo, and Yucatán, and the northernmost portion of Belize (districts of Belize, Corozal, and Orange Walk), as well as a portion of northern Guatemala (most of the department of Petén). An analysis of the YPBP flora identified 167 endemic taxa, 154 of which grow in at least one of the three Mexican states (Campeche, Quintana Roo, and/or Yucatán), whereas another 13 occur exclusively in Belize and/or Guatemala. Eighty-five are in some category of risk (50.9%): 17 taxa (10.18%) are categorized as Critically Endangered (CR), 40 (23.95%) as Endangered (EN), and 28 (16.77%) as Vulnerable (VU). Eighty-one (48.5%) species are not threatened: 12 (7.19%) as Near Threatened (NT) and 69 (41.32%) as Least Concern. A single species (0.6%) is considered Data Deficient (DD). The greatest number of endemic species and endemic threatened species inhabit dry and subhumid forests, and some inhabit semi-evergreen forests. The habits of endemic species and threatened endemic species are diverse, but trees, grasses, and shrubs predominate. The official system of protected natural areas (PNA) does not guarantee the conservation of all endemic species in the region. Ninety-eight (58.68%) of the endemic taxa have more than one population (record) within a PNA.

Ozobryum G. L. Merr., once synonymized with Molendoa Lindb., is recognized as a good genus of Pottiaceae based on evaluation of it as a distinctive dissilient genus. Populations from Mexico are described as a new species, O. mexicanum R. H. Zander. The species Anoectangium warburgii Crundw. & M. O. Hill is transferred to Ozobryum. The genus is synthetically evaluated as integral in respect to other genera of the Pleuroweisieae through combination of critical methods of probabilism, including scientific theory, Granger causation, and verificationism, and of evidentialism, including constructivism, likelihoodism, Bayesianism, and analytic methods of classical taxonomy.