Rhynchosporamesoatlantica (Cyperaceae), an imperiled new species of beaksedge from eastern U.S.A.

Rhynchosporamesoatlanticasp. nov. (Cyperaceae) is described, illustrated, and compared with morphologically similar species. Rhynchosporamesoatlantica is known only from southern Delaware, southeastern Maryland, and southern New Jersey, all within the Mid-Atlantic region of the U.S.A. It inhabits sunny, wet margins of natural, shallow, nutrient-poor, seasonal ponds of the Coastal Plain. Narrow leaf blades; fruits obpyriform in outline; faces of mature fruits possessing a central, pale, well-demarcated disk; and fruit tubercle margins denticulate for most of their lengths indicate R.mesoatlantica is most similar to R.filifolia and R.harperi. Rhynchosporamesoatlantica is unique in its fruit dimensions, scales intermediate in length between R.filifolia and R.harperi, and relatively long fruit stipe. The NatureServe rank of Critically Imperiled and the IUCN rank of Endangered appear warranted for R.mesoatlantica because only six populations are known to be extant, most quite small and isolated; all populations occur within a small geographic area; populations have declined; and serious threats confront the survival of the species.

Vascular plant extinction in the continental United States and Canada.

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.

Extinción de las Plantas Vasculares en Canadá y los Estados Unidos Continentales Resumen Se espera que las tasas de extinción aumenten durante el Antropoceno. Todavía desconocemos las tasas de extinción actuales de las plantas y muchos animales. Cuantificamos las tasas de extinción de la flora vascular de los Estados Unidos Continentales y Canadá a partir del asentamiento de los europeos. Recopilamos datos sobre especies aparentemente extintas mediante la consulta de bases de datos sobre conservación, búsquedas en la literatura y el escrutinio de la lista resultante con botánicos expertos. Ya que la opinión taxonómica varía ampliamente, desarrollamos un índice de incertidumbre taxonómica (ITU). La ITU abarca desde la A hasta la F, en donde la A indica un reconocimiento taxonómico unánime y la F indica el reconocimiento taxonómico por un sólo autor. La ITU nos permitió evaluar rigurosamente las tasas de extinción. Nuestros datos sugieren que 51 especies y 14 taxones infraespecíficos, que en conjunto representan a 33 familias y a 49 géneros de plantas vasculares, se han extinguido en nuestra área de estudio desde el asentamiento de los europeos. Siete de estos taxones existen en cultivos, pero se encuentran extintos en vida libre. La mayoría de las extinciones ocurrieron en la parte oeste del área de estudio, aunque este resultado puede reflejar el momento de la exploración botánica en relación con el asentamiento europeo. El 64% de las plantas extintas eran endémicas de un sitio único y muchas tuvieron presencia fuera de los puntos calientes de biodiversidad. Dada la escasez de los censos botánicos en muchas áreas, particularmente previo al asentamiento europeo, la tasa actual de extinción de las plantas vasculares es sin duda mucho más alta de lo que se indica en este estudio.

Phylogeny and biogeography of the carnivorous plant family Sarraceniaceae.

The carnivorous plant family Sarraceniaceae comprises three genera of wetland-inhabiting pitcher plants: Darlingtonia in the northwestern United States, Sarracenia in eastern North America, and Heliamphora in northern South America. Hypotheses concerning the biogeographic history leading to this unusual disjunct distribution are controversial, in part because genus- and species-level phylogenies have not been clearly resolved. Here, we present a robust, species-rich phylogeny of Sarraceniaceae based on seven mitochondrial, nuclear, and plastid loci, which we use to illuminate this family's phylogenetic and biogeographic history. The family and genera are monophyletic: Darlingtonia is sister to a clade consisting of Heliamphora+Sarracenia. Within Sarracenia, two clades were strongly supported: one consisting of S. purpurea, its subspecies, and S. rosea; the other consisting of nine species endemic to the southeastern United States. Divergence time estimates revealed that stem group Sarraceniaceae likely originated in South America 44-53 million years ago (Mya) (highest posterior density [HPD] estimate = 47 Mya). By 25-44 (HPD = 35) Mya, crown-group Sarraceniaceae appears to have been widespread across North and South America, and Darlingtonia (western North America) had diverged from Heliamphora+Sarracenia (eastern North America+South America). This disjunction and apparent range contraction is consistent with late Eocene cooling and aridification, which may have severed the continuity of Sarraceniaceae across much of North America. Sarracenia and Heliamphora subsequently diverged in the late Oligocene, 14-32 (HPD = 23) Mya, perhaps when direct overland continuity between North and South America became reduced. Initial diversification of South American Heliamphora began at least 8 Mya, but diversification of Sarracenia was more recent (2-7, HPD = 4 Mya); the bulk of southeastern United States Sarracenia originated co-incident with Pleistocene glaciation, <3 Mya. Overall, these results suggest climatic change at different temporal and spatial scales in part shaped the distribution and diversity of this carnivorous plant clade.

Plant DNA barcodes and species resolution in sedges (Carex, Cyperaceae).

We investigate the species discriminatory power of a subset of the proposed plant barcoding loci (matK, rbcL, rpoC1, rpoB, trnH-psbA) in Carex, a cosmopolitan genus that represents one of the three largest plant genera on earth (c. 2000 species). To assess the ability of barcoding loci to resolve Carex species, we focused our sampling on three of the taxonomically best-known groups in the genus, sections Deweyanae (6/8 species sampled), Griseae (18/21 species sampled), and Phyllostachyae (10/10 species sampled). Each group represents one of three major phylogenetic lineages previously identified in Carex and its tribe Cariceae, thus permitting us to evaluate the potential of DNA barcodes to broadly identify species across the tribe and to differentiate closely related sister species. Unlike some previous studies that have suggested that plant barcoding could achieve species identification rates around 90%, our results suggest that no single locus or multilocus barcode examined will resolve much greater than 60% of Carex species. In fact, no multilocus combination can significantly increase the resolution and statistical support (i.e., ≥ 70% bootstrap) for species than matK alone, even combinations involving the second most variable region, trnH-psbA. Results suggest that a matK barcode could help with species discovery as 47% of Carex taxa recently named or resolved within cryptic complexes in the past 25 years also formed unique species clusters in upgma trees. Comparisons between the nrDNA internal transcribed spacer region (ITS) and matK in sect. Phyllostachyae suggest that matK not only discriminates more species (50-60% vs. 25%), but it provides more resolved phylogenies than ITS. Given the low levels of species resolution in rpoC1 and rpoB (0-13%), and difficulties with polymerase chain reaction amplification and DNA sequencing in rbcL and trnH-psbA (alignment included), we strongly advocate that matK should be part of a universal plant barcoding system. Although identification rates in this study are low, they can be significantly improved by a regional approach to barcoding.