Papers by David Barrington
Rhodora, Dec 1, 2007
New data sets and analytic techniques provide the tools to build a new perception of changes in t... more New data sets and analytic techniques provide the tools to build a new perception of changes in the New England flora following the retreat of the last Pleistocene continental glacier. We consider a set of 13 species for which genetic data are available in the context of 1) the fossil record when available, and 2) the evidence of the distribution of appropriate habitat in the late Pleistocene and Holocene. The current New England flora is derived from a diverse set of refugia including the High Arctic, the serpentines of the American West, and the unglaciated and now submerged North Atlantic coastal plain as well as the traditional refugia to the south, both along the coastal plain and to the west in the lower Mississippi valley. This analysis demonstrates that present-day communities are in fact transient, constantly changing assemblages of species.
New Phytologist, 2018
Summary Tropical mountains are disproportionately biodiverse relative to their surface area, but ... more Summary Tropical mountains are disproportionately biodiverse relative to their surface area, but the processes underlying their exceptional diversity require further study. Here, we use comparative phylogenetic methods to examine the impact of the Andean orogeny on the diversification of Neotropical Phlegmariurus, a species‐rich lycophyte clade. We generated a time‐calibrated phylogeny of 105 species of Neotropical Phlegmariurus and estimated lineage diversification rates. We tested for correlations between lineage diversification rates and species range size, niche breadth, elevational range amplitude, and mean elevation of occurrence. A recently developed macroevolutionary model was used to incorporate geological data and test for an association between diversification rates and the Andean uplift. Diversification rates of Neotropical Phlegmariurus are negatively correlated with species range size and positively correlated with mean elevation of species occurrence. The rise of the ...
Molecular phylogenetics and evolution, Aug 17, 2018
The Neotropical clade of the lycophyte genus Phlegmariurus is comprised of an estimated 150 descr... more The Neotropical clade of the lycophyte genus Phlegmariurus is comprised of an estimated 150 described species and exhibits exceptional morphological and ecological diversity. Because of their simple morphology, frequent convergent evolution, and the recentness of the group's diversification, the delimitation of species and species groups has remained challenging. Here, we present a robustly support phylogeny of Neotropical Phlegmariurus based on six chloroplast markers and ca. 70% of known species, and use ancestral character state reconstruction to investigate morphological evolution in the clade, and define natural species groups. The Neotropical species of Phlegmariurus form a clade that also includes a small number of Afro-Madagascan species. A morphologically and ecologically variable group of species from southeastern Brazil form a monophyletic group and represent a parallel radiation to principally Andean lineages. Species groups in Neotropical Phlegmariurus that were pre...
Annals of the Missouri Botanical Garden, 1990
Contributions from the Gray Herbarium of Harvard University
American Fern Journal, 1976
Nature, 2020
New Guinea is the world's largest tropical island and has fascinated naturalists for centuries 1,... more New Guinea is the world's largest tropical island and has fascinated naturalists for centuries 1,2. Home to some of the best-preserved ecosystems on the planet 3 and to intact ecological gradients-from mangroves to tropical alpine grasslands-that are unmatched in the Asia-Pacific region 4,5 , it is a globally recognized centre of biological and cultural diversity 6,7. So far, however, there has been no attempt to critically catalogue the entire vascular plant diversity of New Guinea. Here we present the first, to our knowledge, expert-verified checklist of the vascular plants of mainland New Guinea and surrounding islands. Our publicly available checklist includes 13,634 species (68% endemic), 1,742 genera and 264 families-suggesting that New Guinea is the most floristically diverse island in the world. Expert knowledge is essential for building checklists in the digital era: reliance on online taxonomic resources alone would have inflated species counts by 22%. Species discovery shows no sign of levelling off, and we discuss steps to accelerate botanical research in the 'Last Unknown' 8. Great uncertainty remains as to the number of New Guinea plant species known to science, with conflicting estimates ranging from 9,000 to 25,000 species 9,10. To narrow this range, here we catalogue the entire known vascular flora (angiosperms, gymnosperms, ferns and lycophytes) of mainland New Guinea and its surrounding islands (hereafter 'New Guinea'; Fig. 1a, Extended Data Fig. 1). We do so through a large-scale collaborative effort in which 99 plant experts verified the identity of 23,381 taxonomic names derived from 704,724 specimens (see Methods). Overall, we find that New Guinea supports 13,634 described species, 1,742 genera and 264 families of vascular plants (Supplementary Tables 1, 2). This suggests that New Guinea is the world's most floristically diverse island, with a known vascular plant flora 19% larger than the 11,488 species recorded in Madagascar 11 and 22% larger than the 11,165 species recorded in Borneo (http://www.plantsoftheworldonline.org, accessed 27 April 2019). New Guinea contains almost three times the 4,598 spermatophyte species of Java 12 and 1.4 times the 9,432 vascular plant species of the Philippines 13-the only Malesian island regions for which Floras have been published. The vascular plant flora of New Guinea is divided between two political entities (Fig. 1a): Papua New Guinea, with 10,973 species, has 44% more species than Indonesian New Guinea (Papua Barat and Papua provinces), which has 7,616. Papua New Guinea also has more genera (1,654 versus 1,511) and families (260 versus 248). These differences partly arise from the lower collecting density in Indonesian New Guinea 1,2 (Fig. 1a). Nevertheless, the order of country rankings in plant diversity is unlikely to change with further collections because Papua New Guinea has a larger area, and surface area is the strongest predictor of island plant diversity 14. Our species total for Papua New Guinea differs markedly from the 29,756 species that were presented in an unverified list of the Global Biodiversity Information Facility 15 and our total number of genera for New Guinea is 28% lower than the 2,437 unverified genera reported in a previous macroecological study 16. Together, these differences underscore the need for expert validation in the digital era, which we discuss below.
Applications in Plant Sciences, 2020
In the ferns, cell size has been explored with spores, which are largely uniform within species, ... more In the ferns, cell size has been explored with spores, which are largely uniform within species, produced in abundance, and durable. However, spore size and shape have been variously defined, and the relationship of these traits to genome size has not been well established. Here, we explore the variation in fern spore size and shape by ploidy level and genome size. METHODS: Measurements of spore dimensions for two study sets of ferns, Polystichum and Adiantum, both including diploid and tetraploid taxa, provided the basis for computing estimates of shape and size as defined here. These traits were compared between and within ploidy levels and regressed with genome size estimates from flow cytometry analysis. RESULTS: All size traits were strongly correlated with genome size; the shape trait was weakly correlated. Tetraploids were larger than diploids as expected; the spores of some closely related diploid species were also significantly different in size. DISCUSSION: Researchers with access to a student-grade compound microscope can develop a valid estimate of relative genome size for ferns. These estimates provide enough resolution to infer ploidy level and explore the relationship between genome size, habitat, and physiological constraints for species within ploidy level.
The Plant journal : for cell and molecular biology, 2018
The large retromer complex participates in diverse endosomal trafficking pathways and is essentia... more The large retromer complex participates in diverse endosomal trafficking pathways and is essential for plant developmental programs including cell polarity, programmed cell death, and shoot gravitropism in Arabidopsis. Here we demonstrate that an evolutionarily conserved VPS26 protein (VPS26C; At1G48550) functions in a complex with VPS35A and VPS29 necessary for root hair growth in Arabidopsis. Bimolecular Fluorescence Complementation showed that VPS26C forms a complex with VPS35A in the presence of VPS29 and this is supported by genetic studies showing that vps29 and vps35a mutants exhibit altered root hair growth. Genetic analysis also demonstrated an interaction between a VPS26C trafficking pathway and one involving the SNARE VTI13. Phylogenetic analysis indicates that VPS26C, with the notable exception of grasses, has been maintained in the genomes of most major plant clades since its evolution at the base of eukaryotes. To test the model that VPS26C orthologs in animal and plan...
SUMMARYNon-random collecting practices may bias conclusions drawn from analyses of herbarium reco... more SUMMARYNon-random collecting practices may bias conclusions drawn from analyses of herbarium records. Recent efforts to fully digitize and mobilize regional floras offer a timely opportunity to assess commonalities and differences in herbarium sampling biases.We determined spatial, temporal, trait, phylogenetic, and collector biases in ∼5 million herbarium records, representing three of the most complete digitized floras of the world: Australia (AU), South Africa (SA), and New England (NE).We identified numerous shared and unique biases among these regions. Shared biases included specimens i) collected close to roads and herbaria; ii) collected more frequently during spring; iii) of threatened species collected less frequently; and iv) of close relatives collected in similar numbers. Regional differences included i) over-representation of graminoids in SA and AU and of annuals in AU; and ii) peak collection during the 1910s in NE, 1980s in SA, and 1990s in AU. Finally, in all region...
Systematic Botany, 2017
Although some polyploids in the genus Polystichum are well studied and have well-resolved evoluti... more Although some polyploids in the genus Polystichum are well studied and have well-resolved evolutionary histories, the origin of the circumboreally distributed allotetraploid Polystichum braunii remains obscure. We use the chloroplast markers rbcL, rps4-trnS, and trnL-F as well as the nuclear markers pgiC and gapCp to demonstrate that P. braunii is a single allotetraploid with a minimum of two origins. The two variants isolated from the nucleus resolve with divergent clades, one eastern Asian and one North American. However, they do not have near allies among morphologically appropriate taxa in our sample; the North American progenitor appears to be extinct. A divergence-time analysis based on the cpDNA markers yielded evidence of an older time of origin for P. braunii than for an array of well-known allotetraploids in the eupolypod ferns. Niche modeling in the light of geological and paleontological evidence leads to the conclusion that the two origins were in Beringia. Since P. braunii is genetically undifferentiated but widely distributed, we argue that it has expanded to its circumboreal range in the recent past, though it has a relatively ancient origin.
Botanical Journal of the Linnean Society, 2016
We present a dated phylogenetic tree for the Neotropical genus Attalea (Arecaceae). We used six o... more We present a dated phylogenetic tree for the Neotropical genus Attalea (Arecaceae). We used six orthologues from the nuclear WRKY gene family across 98 accessions to address relationships among species and biogeographical hypotheses. We found that the formerly recognized groups within Attalea are not monophyletic and therefore there is no support for multiple genera as previously thought. Species of Attalea-like palms from the Atlantic forest form a well-supported clade sister to the Attalea species from Amazonia, the Andean valleys and Mesoamerica. Dates for the main divergence events suggest a relationship with the development of the dry forests that now span eastern South America and the now-lost Pebas Lake region in the western Amazon. Attalea crassispatha possibly colonized Hispaniola by a long-distance dispersal event, not via the land bridge Great Antilles Avian Ridge (GAAR), before the Panama channel closed. The common ancestor of Attalea appears to have been an Atlantic forest clade c. 30 Mya. The early split between the Atlantic-forest clade and the two Amazoniannorthern Andean clades was probably the result of climatic changes that caused an increase in aridity in South America.
PhytoKeys, 2016
Polystichum Roth is one of the largest and most taxonomically challenging fern genera. South Amer... more Polystichum Roth is one of the largest and most taxonomically challenging fern genera. South American species have a rich and complex nomenclatural history; many of the early names are inadequately typified. Based on extensive examination of original type material, we designate eleven lectotypes (including Aspidium mohrioides, A. montevidense f. imbricata, A. montevidense f. squamulosa, A. plicatum, A. pycnolepis, Dicksonia andina, Polystichum elegans, P. mohrioides f. latifolia, P. multifidum var. autranii, P. platyphyllum var. kurtziana, and Polypodium polystichoides), and one neotype (P. brongniartianum) for Polystichum taxa. Furthermore, three new synonyms are proposed. Resumen Polystichum Roth es uno de los géneros de helechos más grandes y de mayor complejidad taxonómica. Las especies sudamericanas tienen una rica y compleja historia nomenclatural, con muchos de los nombres inadecuadamente tipificados. En base a un minucioso examen del material tipo original, designamos lectotipos para once taxones de Polystichum (que incluyen Aspidium mohrioides, A. montevidense f. imbricata, A. montevidense f. squamulosa, A. plicatum, A. pycnolepis, Dicksonia andina, Polystichum elegans, P. mohrioides f. latifolia, P. multifidum var. autranii, P. platyphyllum var. kurtziana y Polypodium polystichoides) y un neotipo (P. brongniartianum). Además, se proponen 3 nuevos sinónimos.
Rhodora, 2013
We used the geographic distribution of genetic diversity in the beach pea, Lathyrus japonicus (Le... more We used the geographic distribution of genetic diversity in the beach pea, Lathyrus japonicus (Leguminosae) to reconstruct the location of a Pleistocene refugium and Holocene range expansion. DNA sequence data for the chloroplast ndhF-trnH spacer from a global sample of 22 populations in Asia, North America, and Europe were used to assess broad-scale, circumpolar patterns. The cpDNA data revealed five haplotypes including two largely allopatric, widespread haplotypes (one Pacific, the other Atlantic and inland in the Great Lakes). Three geographically restricted haplotypes were also recovered: one each in New Jersey, Lake Champlain, and the Pacific Northwest. The distribution of isozyme variation at 14 loci for 38 populations of beach peas from the Atlantic and Pacific coasts of North America, Lake Champlain, and the Great Lakes was used to reconstruct a North American history. One subset of allozymes was found on the Atlantic Coast and in the Great Lakes; a second subset was widespread from northwestern North America to Newfoundland. There was a nested pattern to the localization of allozymes along the Atlantic Coast; Cape Cod had the greatest number of allozymes. Pacific and Atlantic isozymes and cpDNA haplotypes occurred together along the coast of Newfoundland and adjacent Labrador. The pattern of genetic variation as assessed from isozymes and cpDNA allow the inferences that: 1) an early divergence yielded Atlantic and Pacific lineages and 2) the Atlantic lineage occupied a Wisconsinan refugium on the nowsubmerged coast of northeastern North America. Our evidence is consistent with there being Holocene secondary contact between the Atlantic and Pacific lineages in the area where they now overlap. We also suggest that an early post-glacial vicariance event is implicated in the history of the Lake Champlain populations.
Australian Journal of Botany, 2015
Polystichum is one of the most diverse genera of ferns, with 360–400 species distributed worldwid... more Polystichum is one of the most diverse genera of ferns, with 360–400 species distributed worldwide. South America harbors ~40 species, clustered in three centres of diversity, namely, the Northern and Central Andes Center (NCC), the Brazilian Center (BC) and the Southern South America Center (SSC). To increase our understanding of the systematic relationships within Polystichum, mitotic chromosomes and spore features were studied in nine species from Argentina and Chile. All species presented the basic number x = 41, with different ploidy levels (2x, 4x and 8x). In general, chromosomes were homogeneous in size (average length 2.50–5.75 µm) and mostly subtelocentric; centromeres were inconspicuous and secondary constrictions were frequently observed. All species presented 64 spores per sporangium, suggesting normal sexual reproduction. Significant differences in spore size were found among species and it was positively correlated with ploidy level. A relationship between sum total ch...
The New phytologist, 2014
Hybridization is an important evolutionary force in plants, but the mechanisms underlying it have... more Hybridization is an important evolutionary force in plants, but the mechanisms underlying it have not been well studied for many groups. In particular, the drivers of non-random patterns of interspecific gene flow (asymmetrical hybridization) remain poorly understood, especially in the seed-free vascular plants. Here, we examine patterns of asymmetrical hybridization in two widespread fern hybrids from eastern North America and study the role of gametophyte ecology in the determination of hybridization bias. We characterized the maternal parentage of > 140 hybrid sporophytes by sequencing a c. 350-bp region of chloroplast DNA (cpDNA). To identify factors contributing to patterns of asymmetrical hybridization, we cultured gametophytes of the parental species and evaluated critical aspects of their reproductive biology. We found that asymmetrical hybridization was prevalent across the populations of both hybrids. Reproductive traits varied across species and suggest that selfing po...
The Journal of the Torrey Botanical Society, 2014
Beyond antheridiogens: chemical competition between gametophytes of Polypodium appalachianum and ... more Beyond antheridiogens: chemical competition between gametophytes of Polypodium appalachianum and Polypodium virginianum. J. Torrey Bot. Soc. 141: 302-312. 2014.-To understand the mechanisms by which fern gametophytes compete and the consequences of their interactions, we studied the effects of intraspecific and interspecific chemical competition on spore germination, sexual development, and gametophyte size in two closely related and cooccurring species of Polypodium from eastern North America. We cultured gametophytes of diploid Polypodium appalachianum Haufler & Windham and tetraploid Polypodium virginianum L. and recorded spore germination, sexual development, and gametophyte size and growth rates in a series of treatments representing different levels of competition within and between the two species. We found that mature gametophytes of both species reciprocally inhibit spore germination, sexual development, and growth of neighboring plants; we show that these effects are due to chemical interactions and not competition for resources. Competitive effects on spore germination and sexual development are similar for within-and between-species interactions, but repression of growth and gametophyte size is greater when competing gametophytes are heterospecific. An additional mechanism of intergametophytic competition via proliferous vegetative growth is also reported. We conclude that gametophytes of these species interact through a novel context-dependent chemical system that is independent from sex expression-regulating pheromones (antheridiogens). Our findings indicate that inhibition of growth and development among fern gametophytes is not solely a side effect of antheridiogens, as is generally thought.
Journal of Plant Research, 2007
Polystichum is one of the largest and most taxonomically complex fern genera in China. The evolut... more Polystichum is one of the largest and most taxonomically complex fern genera in China. The evolutionary relationships of Chinese Polystichum and related genera, and the relationship between our Polystichum phylogeny and ecogeographic distribution, were tested by the use of DNA sequence data. Fifty-one species of Polystichum and 21 species in allied genera were sequenced for the plastid intergenic spacers rps4-trnS and trnL-F. Maximum parsimony and Bayesian phylogenetic analyses of both individual and combined data sets showed that Chinese Polystichum as commonly recognized was paraphyletic: one clade (the CCPC clade) included Cyrtomidictyum lepidocaulon, two Cyrtogonellum species, three Cyrtomium species, and a small number of Polystichum species usually occurring on limestone. A second clade, Polystichum sensu stricto, included the remainder of the Polystichum species; these often occur on non-limestone substrates. The remaining Cyrtomium species formed the third clade. Three subclades resolved within Polystichum sensu stricto (s.s.) clade do not correspond with recent sectional classifications, and we outline the issues relevant to a new classification for the genus.
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Papers by David Barrington