Biodiversity hotspots are conservation priorities. We identify the North American Coastal Plain (NACP) as a global hotspot based on the classic definition, a region with > 1500 endemic plant species ...and > 70% habitat loss. This region has been bypassed in prior designations due to misconceptions and myths about its ecology and history. These fallacies include: (1) young age of the NACP, climatic instability over time and submergence during high sea-level stands; (2) climatic and environmental homogeneity; (3) closed forest as the climax vegetation; and (4) fire regimes that are mostly anthropogenic. We show that the NACP is older and more climatically stable than usually assumed, spatially heterogeneous and extremely rich in species and endemics for its range of latitude, especially within pine savannas and other mostly herbaceous and fire-dependent communities. We suspect systematic biases and misconceptions, in addition to missing information, obscure the existence of similarly biologically significant regions world-wide. Potential solutions to this problem include (1) increased field biological surveys and taxonomic determinations, especially within grassy biomes and regions with low soil fertility, which tend to have much overlooked biodiversity; (2) more research on the climatic refugium role of hotspots, given that regions of high endemism often coincide with regions with low velocity of climate change; (3) in low-lying coastal regions, consideration of the heterogeneity in land area generated by historically fluctuating sea levels, which likely enhanced opportunities for evolution of endemic species; and (4) immediate actions to establish new protected areas and implement science-based management to restore evolutionary environmental conditions in newly recognized hotspots.
Abstract
Generic delimitation in Caryophyllaceae has been challenging and has been informed most recently by use of molecular phylogenetic data. In this study, analysis of 29 samples from the small ...segregate Mononeuria using nuclear ITS and plastid rps16 data revealed it to be polyphyletic. The type species, (M. patula) and two other species (M. muscorum and M. paludicola) were shown to belong to the Sabulina clade. The remaining species formed a clade that also included the previously monotypic Geocarpon and was sister to a heterogeneous group that included the Hawaiian Schiedea and three other monotypic genera, Honckenya, Wilhelmsia and Triplateia. Although several nomenclatural options are available, we propose to place the species from this clade into a single genus, Geocarpon, which basically follows the most recent treatment after exclusion of Sabulina spp., but with the necessary new genus placements. New combinations are proposed: Sabulina muscorum; Sabulina paludicola; Geocarpon carolinianum; Geocarpon cumberlandensis; Geocarpon glabrum; Geocarpon groendlandicum; Geocarpon nuttallii and Geocarpon uniflorum. Analysis of the sequence data revealed remarkable variability among populations of Sabulina patula (formerly Mononeuria patula), Sabulina paludicola (formerly Mononeuria paludicola) and Geocarpon groenlandicum (formerly Mononeuria groenlandica), suggesting that cryptic species may be present. The data also suggested that broader sampling of Sabulina and Geocarpon could lead to increased understanding of the timing and origins of occupation of calcareous glades and rock outcrop habitats in eastern North America.
QUESTIONS: How has plant species richness changed over two decades in one of the most species‐rich savannas in North America? Is an altered disturbance regime, environmental stress, or both, driving ...these changes? In what ways can observations in this savanna inform management of other species‐rich plant communities? LOCATION: Longleaf pine savannas in southeast North Carolina, USA. METHODS: In 2011–2013, we re‐surveyed permanent plots established in the 1980s and 1990s in a longleaf pine (Pinus palustris) savanna in North Carolina to quantify changes in species richness at multiple spatial scales following 15 yr of reduced fire frequency plus periodic drought. For comparison, we re‐sampled other longleaf pine savannas in the region that had not experienced reduced fire frequency, but had experienced similar drought. In addition, we identified which types of species were lost and gained, and summarized changes in species frequency by growth form, plant height, and habitat affinity. RESULTS: We detected substantial declines in small‐scale species richness and species frequency from the 1980s to 2011, representing a loss of 33% to 41% of the flora, depending on the spatial scale. Small herbaceous species had become particularly scarce. Additional re‐sampling in the wetter years of 2012 and 2013 after consecutive years of fire revealed that species richness had increased slightly from 2011, but was still considerably lower than that in the 1980s. Other savannas did not exhibit such dramatic declines in species richness, suggesting reduced fire frequency in addition to drought contributed to species loss in Big Island Savanna over time. CONCLUSIONS: Our work suggests that nearly annual fire is necessary for the maintenance of high plant species richness in mesic longleaf pine savannas, and even a modest reduction in fire frequency can have dramatic negative impacts. This study also suggests that drought is an important factor structuring grassland ecosystems in the southeastern US, despite relatively high regional precipitation. We believe these findings can be generalized to other species‐rich grasslands that are sensitive to changes in disturbance regimes and may require frequent disturbance to maintain plant species richness.
Questions: What are the alluvial vegetation types of the North Carolina Piedmont? How is species composition related to site conditions? Location: Catawba, Yadkin-PeeDee, Cape Fear, Neuse and ...Tar-Pamlico River Basins, North Carolina Piedmont region, southeast USA. Methods: We recorded 194 alluvial vegetation plots. Vegetation types were derived using flexible beta-hierarchical cluster analysis and random forests classifiers to reassign misclassified plots. We used canonical correspondence analysis to show the relationship between species composition and key environmental variables. Results: Twelve forested vegetation types and two herbaceous types were distinguished, nested within a hierarchical classification structure ive higher-level groups. The five mega groups describe broad geomorphic-floristic conditions, whereas the narrower vegetation types characterize finer-scale floristic variation. Floristic variation is related to stream order and soil chemistry (pH and Ca:Mg ratio), as well as soil texture variables (percentage sand and percentage clay). We present a summary of floristic composition and structure, environmental setting and geographic distribution for each of the 14 vegetation types. Conclusions: We suggest recognition of 14 alluvial vegetation types in the North Carolina Piedmont. In comparing our vegetation types with the community concepts currently recognized in the US National Vegetation Classification, some of our types fit well within recognized NVC associations, whereas others deviate sharply from established types, suggesting the need for reworking the currently recognized NVC alluvial type concepts.
Persea borbonia and Persea palustris are two species in the Lauraceae family, native to the southeastern USA. Because of their similar morphologies, many authorities treat these two species as ...varieties of a more broadly defined group, Persea borbonia. Consequently, the species and communities associated with P. borbonia and P. palustris are not well defined. Extensive mortality has occurred in both species because of laurel wilt disease. Our objectives were to (a) determine whether P. borbonia and P. palustris are associated with different communities, (b) describe the communities and associated species in which P. borbonia and P. palustris occur, and (c) determine which communities support larger individuals of Persea spp. We analyzed data collected from 1988 through 2012 by the Carolina Vegetation Survey. To test differences among plant communities with natural growth of P. borbonia and P. palustris, we used ordination and analysis of similarities. We used cluster analyses and species-indicator analyses to group 388 plots into distinct communities. Results were verified by random forest analyses. We compared basal area of Persea spp. in each community with Kruskal-Wallis multiple comparisons. Persea borbonia and P. palustris communities were significantly different in species composition. Persea borbonia was limited almost exclusively to maritime coastal forests, whereas P. palustris had a larger geographical range, extending from near-coastal settings inland through the fall-line of the sandhills. The cluster and indicator species analyses identified eight unique groups, one for P. borbonia, and seven for P. palustris.
Two species of Trichostema L. (Ajugoideae, Lamiaceae) from western states need nomenclatural clarification. Trichostema simulatum Jeps. occurs throughout northern California and southern Oregon. It ...was published by Willis Linn Jepson in his 1925 flora of California citing the type collection as “Klamathon, Copeland 3534, Type”. This is a conflation of the collector's name and the specimen number of the exsiccata West American Plants, in which the type specimen was distributed by C. F. Baker in 1903. Furthermore, an herbarium name, “Trichostema laetum Greene,” appears on most T. simulatum type material. This designation was never published and is a nomen nudum. Trichostema austromontanum F.H.Lewis occurs throughout the mountain ranges of southern California and Baja California. Originally published with two subspecies by Harlan Lewis in 1945, the three taxa have since been determined to be invalidly published because Lewis did not provide a species description, only subspecies descriptions. Herein, we provide a clarification on the type specimens of T. simulatum Jeps. as well as a valid publication of the species name T. austromontanum.
Twenty-seven species, new to the flora of Georgia, are reported here and validated by cited voucher specimens at the University of Georgia (GA) and Valdosta State University (VSC) herbaria, the two ...largest herbaria in the state. Reassessment and comparison of these collections data have been greatly facilitated by specimen digitization efforts, especially those fostered among herbaria by the GA–VSC Herbaria Collaborative and by the Southeast Regional Network of Expertise and Collections (SERNEC). Four species (Chelone lyonii, Prunus hortulana, Sporobolus arcuatus, and Symphyotrichum simmondsii) are likely native to Georgia and represent range extensions from nearby states. Chelone lyonii and Sporobolus arcuatus are rare and state-ranked critically imperiled (S1) by the Georgia Department of Natural Resources. The 23 exotic species are more or less naturalized or have potential to naturalize in the state. These nonnatives are escapes from cultivation (15 species) or weedy plants (eight species) that are widespread elsewhere and not typically cultivated. Four species (Cleome monophylla, Lobelia pedunculata, Quercus myrsinifolia, and Sedum emarginatum) are putative first records for the flora of North America, at least as occasional escapes.
Philadelphus (Hydrangeaceae) comprises 60 or fewer species distributed disjunctly in eastern Asia, eastern and western North America to Central America, and southeastern Europe and western Asia. The ...genus is highly valued in horticulture, but poorly understood regarding taxonomy, species relationships, and biogeographic history. The present study was the first phylogenetic and biogeographic analysis of Philadelphus using both nuclear and chloroplast DNA markers to evaluate classification schemes and to elucidate the biogeographic origin. Our results suggest that Philadelphus is a paraphyletic group with the monotypic genus Carpenteria nested within. Three major lineages were identified in the Philadelphus–Carpenteria clade, each strongly supported by the molecular data. Biogeographic analysis using the Bayes‐DIVA method (implemented in the newly developed RASP) and divergence time dating with BEAST resolved the origin and early diversification of Philadelphus s.l. (including Carpenteria) in western North America (including Mexico) in the Eocene. The lineage diversified and subsequently spread into Asia and other areas in the late Tertiary or Neogene to obtain a worldwide distribution. The study adds an additional example of an “out of western North America” migration in the phylogeographic history of the northern hemisphere.
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