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Showing papers in "International Journal of Plant Sciences in 2001"


Journal ArticleDOI
TL;DR: The history of the climatic and geographic features of the Tertiary of the Northern Hemisphere agrees with many phylogenetically based phylogeographic hypotheses of living angiosperm genera but indicates that some hypotheses require reanalysis.
Abstract: Phylogeography posits that the sequence of speciation events within a clade should parallel the geographic migration and isolation of members of the clade through time. The primary historical features that govern migration and allopatry in land plants are changes in physical geography (e.g., oceans, mountains, and deserts) and in climate (e.g., moisture, temperature, and day length), features that are often interrelated. If we assume that living genera retain physiological stability through time, much as they retain the morphological features that allow their identification, then these environmental features of the geologic past may be used to test phylogeographic hypotheses of living genera based on phylogenetic analysis. The history of the climatic and geographic features of the Tertiary of the Northern Hemisphere agrees with many phylogenetically based phylogeographic hypotheses of living angiosperm genera but indicates that some hypotheses require reanalysis. While the parallel comparison of phylogene...

564 citations


Journal ArticleDOI
TL;DR: Two phylogenetic analyses on genera with intercontinentally disjunct distributions suggested an Asian origin for the genus Fagus with bidirectional migration to Europe and North America, consistent with a paraphyletic assemblage of Asian species and intercontinental exchange via the Bering Land Bridge (BLB).
Abstract: The angiosperm family Fagaceae is a central element of several distinct community types throughout the Northern Hemisphere and a prime candidate for modern biogeographic analysis. The rich fossil record for the family provides an unparalleled source to compare with modern distributions and evaluate hypotheses of origin, migration, and vicariance. We conducted separate phylogenetic analyses on genera with intercontinentally disjunct distributions using various noncoding regions of chloroplast and nuclear ribosomal DNA sequences. Analyses generally supported the (North \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} ormalfont \selectfont} \DeclareTextFontCommand{\textc...

257 citations


Journal ArticleDOI
TL;DR: This is a combination of a review and original data on floral structure, development, and biology of representatives of all families of the ANITA grade and, in addition, Chloranthaceae and Ceratophyllaceae.
Abstract: This is a combination of a review and original data on floral structure, development, and biology of representatives of all families of the ANITA grade and, in addition, Chloranthaceae and Ceratophyllaceae. Since the ANITA grade has been identified as the basalmost grade of extant angiosperms based on molecular studies by a number of authors, it has become possible to search for potential plesiomorphies among flowers of extant basal angiosperms. They may include the following traits: flowers small, pollination by small insects (dipters, thrips, moths); flowers with moderate or low number of floral organs, in spiral (or whorled) arrangement, with a tendency to form organ series in Fibonacci numbers (3, 5, 8); flowers bisexual (but easily becoming unisexual because of low level of synorganization between organs), protogynous; tepals (in spiral flowers) with gradual transitions between bractlike, sepal‐like, and petal‐like forms; stamens with short filaments, anthers with a connective tip, with more or less ...

256 citations


Journal ArticleDOI
TL;DR: Despite the existence of a variety of patterns, inferred ancestral areas and divergence times can be explained by assuming initial diversification within Asia in a number of lineages, followed by iterative trans‐Beringian dispersion and vicariance.
Abstract: Geological and climatological processes that have impacted the biota of the Northern Hemisphere during the Tertiary are expected to yield little resolution when area cladograms are compared without taking the timing of diversification into account. In an attempt to establish a set of appropriate phylogenetic comparisons, we distinguished between a Pacific track involving (minimally) China, Japan, and eastern North America but not Europe, and an Atlantic track involving China, Europe, and eastern North America but not Japan (or, in most cases, western North America). Within the two Atlantic‐track taxa considered here—Liquidambar and Cercis—European and North American species are more closely related to one another than they are to the Asian species. Within a set of five Pacific‐track taxa—Hamamelis, Weigela‐Diervilla, Triosteum, Buckleya, and Torreya—we see all possible relationships involving China, Japan, and eastern North America. Estimates of minimum divergence times between Old World and New World lin...

249 citations


Journal ArticleDOI
TL;DR: Combined analysis provided some evidence for a relationship of Quercus to Lithocarpus and Chrysolepis, taxa with dichasially arranged pistillate flowers, where each flower is surrounded by cupular tissue, which indicates that a more broadly defined flower cupule may have a single origin.
Abstract: The family Fagaceae includes nine currently recognized genera and ca. 1000 species, making it one of the largest and most economically important groups within the order Fagales. In addition to wide variation in cupule and fruit morphology, polymorphism in pollination syndrome (wind vs. generalistic insect) also contributes to the uniqueness of the family. Phylogenetic relationships were examined using 179 accessions spanning the taxonomic breadth of the family, emphasizing tropical, subtropical, and relictual taxa. Nuclear ribosomal DNA sequences encoding the 5.8S rRNA gene and two flanking internal transcribed spacers (ITS) were used to evaluate phylogenetic hypotheses based on previous morphological cladistic analysis and intuitive schemes. Parsimony analyses rooted with Fagus supported two clades within the family, Trigonobalanus sensu lato and a large clade comprising Quercus and the castaneoid genera ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{b...

240 citations


Journal ArticleDOI
TL;DR: The chloroplast atpB‐rbcL noncoding spacer region was used to derive a phylogeny for seven outgroup genera and 11 species of Capsicum to resolve further questions of species delimitation and phylogenetic relationships of species within Capsicum.
Abstract: This study focuses on three phylogenetic problems related to Capsicum (Solanaceae): (1) the monophyly of the genus, (2) species delimitation within the genus, and (3) phylogenetic relationships of species within Capsicum. The chloroplast atpB‐rbcL noncoding spacer region was used to derive a phylogeny for seven outgroup genera and 11 species of Capsicum. Data derived from five introns within the nuclear gene waxy were used, both separately and in combination with the atpB‐rbcL spacer data, to resolve further questions of species delimitation and phylogenetic relationships within Capsicum. Capsicum is monophyletic, with moderate support. Capsicum ciliatum, which is both molecularly and morphologically distinctive, is sister to a highly supported clade consisting of all other Capsicum species studied. Capsicum cardenasii and C. eximium are sister species and are, in turn, sisters to a moderately supported clade consisting of C. tovarii, C. pubescens, C. chacoense, C. baccatum, C. galapagoense, C. chinense, ...

210 citations


Journal ArticleDOI
TL;DR: Exotic species capable of successfully invading tallgrass prairie did not differ considerably from native species in most traits related to resource utilization and carbon gain, and invasive exotic species, those capable of displacing native species and dominating a community, were not distinct for the observed traits from their native counterparts.
Abstract: We compared 13 traits of invasive exotic, noninvasive exotic, and ecologically similar native species to determine if there are generalizable differences among these groups that relate to persistence and spread of exotic species in tallgrass prairie plant communities. When species were grouped as invasive (two species), noninvasive (five species), and native (six species), no differences were found for the suite of traits examined, likely because of the high variability within and between groups. However, when exotic species, regardless of invasiveness, were compared with the native species, specific leaf area was ca. 40% higher for the exotic species, a result that is consistent with that of other studies. This pattern was also observed for five of seven pairwise comparisons of exotic and native species with similar life history traits. In contrast, total end‐of‐season biomass was as much as three times higher for the native species in five of seven of the native‐exotic species pairs. For other traits, d...

172 citations


Journal ArticleDOI
TL;DR: Molecular and phylogenetic results support the importance of the Middle to Late Tertiary in the formation of the disjunct pattern for many temperate taxa.
Abstract: The reality of the eastern Asian–eastern North American disjunct biogeographic pattern is supported by (1) the occurrence of closely related species in many plant genera in these two widely distributed areas, (2) the high level of morphological similarities of species within these disjunct genera, and (3) the degree of morphological similarity between some corresponding species in more widely distributed genera of the Northern Hemisphere. Most disjunct genera are supported to be monophyletic, although some are found to be paraphyletic and, less commonly, polyphyletic. The disjunct pattern shown by many genera largely represents relict distributions of the Tertiary and is the product of complex processes such as migration/dispersal, extinction, speciation, vicariance, and stasis. The retention of morphological similarities among the many corresponding disjunct taxa may have arisen by morphological stasis and/or low rates of morphological evolution. Furthermore, accelerated rates of morphological evolution ...

169 citations


Journal ArticleDOI
TL;DR: Ten North Temperate taxa representing diverse angiosperm lineages were analyzed for biogeographic histories using the dispersal‐vicariance analysis method to gain insights into the origin and evolution of disjunct distributions in the Northern Hemisphere and suggest pseudocongruence among lineages in phylogenetic relationships and distributional patterns.
Abstract: Ten North Temperate taxa representing diverse angiosperm lineages were analyzed for biogeographic histories using the dispersal‐vicariance analysis method to gain insights into the origin and evolution of disjunct distributions in the Northern Hemisphere. Results indicate four general biogeographic patterns: (1) origin and speciation in eastern Asia with subsequent expansion into North America and/or Europe (e.g., Aralia sect. Aralia, Symplocarpus, and possibly Asarum, Aesculus, and Chrysosplenium); (2) origin in eastern Asia and western North America with subsequent spread into eastern North America (e.g., Calycanthus and Boykinia); (3) a disjunct origin in eastern Asia and eastern North America with subsequent dispersal from eastern Asia into eastern North America (e.g., Panax); and (4) a widespread origin in the Northern Hemisphere with subsequent fragmentation by intercontinental vicariance (e.g., Cornus and Trautvetteria). Although there are caveats, the results indicate that the disjunct distributio...

165 citations


Journal ArticleDOI
TL;DR: The homology of involute leaf vernation in Primula is reconsidered in light of its two independent origins, and it is come to the conclusion that vernations in subgenus Sphondylia is better characterized as conduplicate.
Abstract: We sequenced the trnL and rpl16 introns of the chloroplast DNA from 95 of the ca. 425 species (30 of 37 sections, seven of eight subgenera) of Primula L. in order to reconstruct the phylogenetic history of the group. Among the 24 additional taxa sampled are representatives of all genera that are likely to be embedded in Primula, as well as outgroups from the Maesaceae, Theophrastaceae, and Myrsinaceae. In the strict consensus of the most parsimonious trees, Primula and the genera embedded in it (Dionysia Fenzl., Sredinskya [Stein] Fedorov, Dodecatheon L., and Cortusa L.) are sister to a clade of several genera previously suspected to be embedded in Primula (Hottonia L., Omphalogramma [Franchet] Franch., and Soldanella L.). In recognition of this, two new rankless names are defined for these clades (/Primula and /Soldanella). Close relationships are inferred between Dionysia and Primula subgenus Sphondylia (Duby) Rupr., Sredinskya and Primula subgenus Primula, Dodecatheon and Primula subgenus Auriculastrum...

116 citations


Journal ArticleDOI
TL;DR: The data indicate that several North American populations, including those from Ohio, West Virginia, New York, and Kentucky, may have originated from plants from the British Isles, although it is possible that multiple introductions of A. petiolata from Europe have occurred.
Abstract: A study was conducted using molecular‐based population genetic data to interpret biogeographic relationships and survey genetic similarity within and among populations of Alliaria petiolata from its native and introduced ranges. Three of the populations examined were from Europe, the native range of A. petiolata, whereas eight populations were from North America, where A. petiolata was introduced over 125 yr ago and where it has since become an invasive pest. Inter–simple sequence repeat (ISSR) analysis using two different primers revealed 56 unique fragments. Genetic variation was greater in some native populations (Scottish and Dutch) compared with introduced populations. Estimates of the Shannon phenotypic diversity index among populations ranged from 0.917 to 0.996. Analysis of molecular variance indicated that there was strong population structuring, with the greatest variance among populations (61.0%) and with much less variance both between continents (16.3%) and within populations (22.7%). Signifi...

Journal ArticleDOI
TL;DR: The presence of anthocyanins in the mesophyll of so many species is inconsistent with the hypothesis of protection against UV damage or fungal pathogens, and the differing tissue distributions indicate that the pigments may function in different ways, as in photoprotection and free‐radical scavenging.
Abstract: We examined the anatomy of expanding, mature, and senescing leaves of tropical plants for the presence of red pigments: anthocyanins and betacyanins. We studied 463 species in total, 370 genera, belonging to 94 families. This included 21 species from five families in the Caryophyllales, where betacyanins are the basis for red color. We also included 14 species of ferns and gymnosperms in seven families and 29 species with undersurface coloration at maturity. We analyzed 399 angiosperm species (74 families) for factors (especially developmental and evolutionary) influencing anthocyanin production during expansion and senescence. During expansion, 44.9% produced anthocyanins and only 13.5% during senescence. At both stages, relatively few patterns of tissue distributions developed, primarily in the mesophyll, and very few taxa produced anthocyanins in dermal and ground tissue simultaneously. Of the 35 species producing anthocyanins both in development and senescence, most had similar cellular distributions....

Journal ArticleDOI
TL;DR: By 6 h after flower closure, nectar volume and sugar concentration had decreased drastically, especially in female flowers, suggesting that Cucurbita pepo has the ability to reabsorb most or all unconsumed nectar.
Abstract: Nectar volume and sugar composition of male and female flowers of Cucurbita pepo L. (squash), a vine native to tropical Mexico, were studied in an Italian botanical garden. Flowers opened at dawn and closed at noon. Both sexes were extremely rewarding compared with most bee‐pollinated flowers, producing 22–40 mg sugar/flower in 6 h. Female flowers produced significantly more nectar sugar than did males, mainly because of a higher concentration of sugars in nectar (440 vs. 325 mg/mL). The temporal pattern of secretion was similar in the two sexes, and both nectars were sucrose rich. Sugar composition did not vary during anthesis. By 6 h after flower closure, nectar volume and sugar concentration had decreased drastically, especially in female flowers. Cucurbita pepo has the ability to reabsorb most or all unconsumed nectar.

Journal ArticleDOI
TL;DR: The basic organization of vascular plants is reviewed and the relationship of anatomy to morphology in interpreting gene expression is reviewed, demonstrating that these two levels of organization are relatively independent of one another and that anatomy cannot be substituted for morphology in analyzing the effects of genes on leaf development.
Abstract: As an older and more established discipline, plant morphology is an important but relatively underutilized resource for the interpretation of mutants. Plant morphology has the potential to provide the context for molecular genetic investigations, especially those concerned with leaf morphogenesis. This article first reviews the basic organization of vascular plants and the relationship of anatomy to morphology in interpreting gene expression. It demonstrates that these two levels of organization are relatively independent of one another and that anatomy cannot be substituted for morphology in analyzing the effects of genes on leaf development. Morphological principles are then applied to two aspects of leaf development, transectional symmetry and leaf dissection. According to this perspective, so‐called organs in plants are simply regional expansions that carry specific cell and tissue types in a particular orientation in space. Rather than considering specific genes as determining particular organ types,...

Journal ArticleDOI
TL;DR: This brief review article provides a general framework for the study of leaf morphogenesis and identifies areas where it is believed that important issues remain unresolved.
Abstract: The last decade of the twentieth century has witnessed a period of renewed interest, redefinition of questions, and some dramatic advances toward resolving some of the long‐standing issues related to the developmental regulation of leaf morphogenesis. New interest has been sparked by the application of developmental genetics, molecular biology, and mosaic analysis to the study of genetic model species. The integration of knowledge gained from these newer approaches with that derived from more than a century of comparative developmental morphology is crucial for advancing understanding of leaf morphogenesis. This link is particularly important for the interpretation of mutant phenotypes and gene expression patterns. In this brief review article, we provide a general framework for the study of leaf morphogenesis and identify areas where we believe that important issues remain unresolved.

Journal ArticleDOI
TL;DR: Thucydia is the only conifer with ovuliferous fertile zones, compound pollen cones, and dissimilar stomatal distributions on vegetative and fertile leaves and provides a benchmark for developing sound taxonomic concepts and useful criteria for identifying specimens of walchian species and for resolving phylogenetic relationships among fossil and living conifers.
Abstract: Abundant fossils of a single conifer species occur in a Pennsylvanian‐age deposit of eastern North America, providing the opportunity to describe a biological taxon of primitive conifers as well as to clarify the uncertain taxonomy and systematics of walchian conifers. Thucydia mahoningensis gen. et sp. nov. is represented by up to three orders of interconnected vegetative and fertile shoots that are preserved as coalified compressions with cuticles; some also display internal anatomy. The plant has an orthotropic stem, with two orders of plagiotropic lateral branches that all bear helically arranged simple leaves. Ovulate fructifications consist of compact zones of bracts with axillary ovuliferous dwarf shoots on otherwise vegetative branches. Pollen cones are compound shoots comprising helically arranged dwarf shoots in the axils of bracts on a main axis. Polliniferous dwarf shoots produce sterile scales, sporophylls with a terminal pollen sac, and in situ Potonieisporites grains. Stems have an endarch ...

Journal ArticleDOI
TL;DR: The distribution of tapetal types in basal angiosperms is reviewed both from the literature and new observations in the context of recent phylogenetic analyses, finding apparent plasticity for a relatively brief but critical time in angiosperm evolution.
Abstract: The distribution of tapetal types in basal angiosperms is reviewed both from the literature and new observations in the context of recent phylogenetic analyses. Secretory tapeta predominate among land plants. The majority of basal angiosperms share a secretory tapetum with their anthophyte ancestors. Plasmodial and invasive tapeta are relatively rare in eudicots but have evolved several times among early‐branching angiosperms, especially in monocotyledons, in which they have evolved three or more times. The invasive tapetum has evolved at least four other times independently in basal angiosperms: in Nymphaeaceae, Annonaceae, Monimiaceae, and Winteraceae. Plasmodial tapeta are mostly found in monocotyledons but have evolved at least twice in basal angiosperms, in Annonaceae, and in Hernandiaceae/Lauraceae. This apparent plasticity for a relatively brief but critical time in angiosperm evolution may reflect the early evolution of highly specific pollination syndromes.

Journal ArticleDOI
TL;DR: This study indicated that both Cycadothrips chadwicki Mound and Tranes lyterioides (Pascoe) (Coleoptera, Curculionidae) affect pollination of cycads, the first demonstration that specialist pollinators of two different insect orders pollinate a cycad.
Abstract: Specialist beetles (Insecta, Coleoptera) have generally been considered to be the sole pollinators of cycads that have been studied. The possible pollination role of members of the thrips genus Cycadothrips (Thysanoptera, Aeolothripidae) found on male and female cones of some species of the Australian cycad genus Macrozamia (Zamiaceae), however, has never been experimentally investigated. This study, which included behavioral observations, visitation rates, pollen loads and exclusion experiments of insect visitors to Macrozamia communis cones in New South Wales, indicated that both Cycadothrips chadwicki Mound and Tranes lyterioides (Pascoe) (Coleoptera, Curculionidae) affect pollination. This is the first demonstration that specialist pollinators of two different insect orders pollinate a cycad. Cycadothrips adults and larvae fed on pollen, and Tranes weevil adults fed mainly on male sporophyll tissue and some pollen. Larvae of both insects developed in male cones; thrips larvae fed on pollen and weevil ...

Journal ArticleDOI
TL;DR: It is concluded that Cycadothrips albrechti is the sole pollinator of M. macdonnellii, and the possibility is considered that thrips were involved in pollen transfer before the radiation of flowering plants.
Abstract: Macrozamia macdonnellii (Zamiaceae) grows at a few isolated sites in central Australia. Male cones support large populations of a host‐specific thrips, Cycadothrips albrechti n.sp. (Thysanoptera, Aeolothripidae). This insect breeds only in these male cones, from which the adults swarm in late afternoon as the temperature falls and humidity rises. A small sticky trap at one female cone caught 3844 adults on a single afternoon; large numbers of thrips were observed entering this cone. Each thrips carried an average of 15 pollen grains, and pollen delivery into the cone was thus estimated to average more than 5500 grains per ovule. No other potential pollinators were found on these cycads, and it is concluded that C. albrechti is the sole pollinator of M. macdonnellii. Since Cycadothrips constitutes a basal clade within the Thysanoptera, the possibility is considered that thrips were involved in pollen transfer before the radiation of flowering plants.

Journal ArticleDOI
TL;DR: The study supports the view that Apostasia and Neuwiedia are closely related and that Apostasioideae are at the base of the orchid clade, sharing characters with orchids and lower Asparagales.
Abstract: Floral development, structure, and pollination biology of species of Apostasia and Neuwiedia constituting the basalmost orchid subfamily Apostasioideae were studied. The perianth organs arise from a ring primordium. The two adaxial sepals appear first, followed by the petal primordia. This contrasts with monandrous orchids, in which the median petal primordium is the first organ of the inner perianth whorl to develop. Stamens are only formed on the abaxial side of the flower. However, in Neuwiedia veratrifolia and Apostasia nuda, vestiges of stamen primordia are present on the adaxial side of the flower. In Apostasia only, the lateral stamens are fully developed, whereas the median organ is a staminode; in A. nuda the staminode is suppressed. At anthesis the anthers are free in Neuwiedia, but they are postgenitally connected in Apostasia. In both genera, stamens and style are congenitally fused at the base. The inferior ovary is at first unilocular and then becomes trilocular by postgenital fusion of the ...

Journal ArticleDOI
TL;DR: A Eurasian origin of the Styracaceae is supported, with subsequent dispersion to the Americas, and the eastern Asian–eastern North American disjunct genus Halesia is not supported as monophyletic.
Abstract: The dicotyledonous family Styracaceae is distributed among all the major Tertiary mixed‐mesophytic forest refugia of the Northern Hemisphere. To infer the biogeographical history of the family and its significance for models of Northern Hemisphere historical biogeography, the phylogeny of the Styracaceae was estimated from separate and combined analyses of three DNA sequence data sets (chloroplast trnL intron/trnL‐trnF spacer, chloroplast rbcL gene, ITS region of nuclear ribosomal DNA) and a morphological data set of 47 characters. Up to 15 samples of other families of Ericales sensu the Angiosperm Phylogeny Group were employed as outgroups. The results strongly support the monophyly of the family. Dispersal‐vicariance analysis and Fitch parsimony optimization support a Eurasian origin of the Styracaceae, with subsequent dispersion to the Americas. This scenario is consistent with a hypothesized European origin for the family based on the fossil record. The eastern Asian–eastern North American disjunct ge...

Journal ArticleDOI
TL;DR: Taiwan lily (Lilium longiflorum Thunb. var. formosanum Baker) is distributed from lowlands to high mountains in Taiwan with large morphological variation and there is a need for immediate measures to conserve the germplasms of lower altitude populations.
Abstract: Taiwan lily (Lilium longiflorum Thunb. var. formosanum Baker) is distributed from lowlands to high mountains in Taiwan with large morphological variation. The genetic differentiation of seven populations from low, middle, and high altitudes was studied by evaluating seven morphological traits and 64 RAPD markers. Morphological data defined two groups of low‐middle and high altitudes. RAPD analysis employing nine primers also revealed that the populations were differentiated according to the altitudinal differences. When populations were treated as consisting of three groups of low, middle, and high altitudes, the result of analysis of molecular variance (AMOVA) indicated that the variance components among groups, among populations within groups, and among individuals within populations were 5.09%, 2.82%, and 92.09% of the total variance, respectively. A two‐level AMOVA on three populations of low altitudes revealed that the diversities among populations and among individuals within populations accounted f...

Journal ArticleDOI
TL;DR: In this paper, the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA was employed to examine the monophyly of Rhus s.str. and to provide insight into the phylogenetic and biogeographic history of the genus.
Abstract: Rhus L. (sensu lato) has been considered the largest and most widespread genus in the Anacardiaceae. Controversy has surrounded the delimitation of the genus. Historically, seven segregate genera have been recognized: Actinocheita, Cotinus, Malosma, Melanococca, Metopium, Searsia, and Toxicodendron. These genera, together with Rhus s.str., are commonly referred to as the Rhus complex. Rhus s.str. includes two subgenera, Lobadium (ca. 25 spp.) and Rhus (ca. 10 spp.). Sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA were employed to examine the monophyly of Rhus s.str. and to provide insight into the phylogenetic and biogeographic history of the genus. The ITS data set indicates that Rhus s.str. is monophyletic. Actinocheita, Cotinus, Malosma, Searsia, and Toxicodendron are distinct from Rhus s.str., although the relationships among these genera of the Rhus complex are not well resolved. Rhus subgenus Rhus is paraphyletic; the monophyletic subgenus Lobadium is nested wi...

Journal ArticleDOI
TL;DR: A phylogenetic and biogeographic analysis of two legume groups, the Ormocarpum and Robinia clades, suggest that both Pictetia and Poitea stem from Tertiary North American boreotropical groups, and A. Wolfe’s hypothesis that the Greater Antilles harbor boreotropic relicts is supported.
Abstract: The fossil record shows that the legume family was abundant and taxonomically diverse in Early Tertiary tropical deciduous forests of North America. Today, woody members of this family are almost nonexistent in temperate deciduous forests. This former North American legume diversity now lies in the Tropics, including the Greater Antilles. To show the Antillean refugia, we detail a phylogenetic and biogeographic analysis of two legume groups, the Ormocarpum and Robinia clades, which have either a Tertiary fossil record in North America or a sister clade with such a fossil record. A combined analysis of molecular and nonmolecular data is used for the cladistic vicariance approaches, while an exhaustively sampled data set of nrDNA ITS/5.8S sequences is used for the molecular biogeographic analysis. Results from component, three‐area‐statements, and Brooks parsimony analysis are equivocal in suggesting an influence of Tertiary history on the distribution of the woody genera Pictetia (Ormocarpum clade) and Poi...

Journal ArticleDOI
TL;DR: Cedrelospermum (Tertiary of southern Mexico through midlatitude North America and Europe) is resolved as a link, both phylogenetically and geographically, between the Central and South American taxa Ampelocera and Phyllostylon and the genera of North America, Europe, and Asia.
Abstract: Attempts to reconstruct phytogeographic history based exclusively on either modern or fossil distribution patterns may give misleading results. Local extinction within a widespread clade can undermine phylogeographic hypotheses based on modern‐day distribution patterns; e.g., within the Aceroideae, Dipteronia is the sister group to Acer and is presently known only from Asia; the discovery of Dipteronia in the North American Tertiary requires a rethinking of hypotheses based solely on the modern distribution of the two genera. Conversely, the fossil record alone cannot provide a well‐resolved phytogeographic history because the availability of well‐preserved fossils for a particular time interval differs among regions. The most informative method for deducing the phytogeographic history of a given clade is to conduct phylogenetic analyses that include both fossil and extant representatives to deduce the sequence of dispersal and/or vicariance events indicated by the most parsimonious trees. The choice of t...

Journal ArticleDOI
TL;DR: Comparisons of the reproductive biology of a declining native grass and its invasive alien competitor in Hawai'i help explain the current distribution of remnant H. contortus populations in the driest, most nutrient‐poor habitats of the Hawaiian Islands.
Abstract: We compared the reproductive biology of a declining native grass, Heteropogon contortus, and its invasive alien competitor, Pennisetum setaceum, in Hawai'i to identify differences that could explain why the alien has spread so successfully while the native has declined. Both species are drought‐tolerant, perennial, C4 bunchgrasses that rely on apomictic seeds for reproduction. In a series of field observations and greenhouse experiments, we compared the phenology, ovule production, seed production, and seed germination in H. contortus and P. setaceum. In the field, the alien produced two to nine times more seeds per plant than the native. Furthermore, the germination rate for fresh seeds was significantly greater for P. setaceum (45%) than for H. contortus (13%), giving the alien the ability to quickly spread after setting seed. In greenhouse experiments, clipping, burning, and pollen addition did not affect final reproductive output or seed‐set rate in either species. However, P. setaceum recovered from ...

Journal ArticleDOI
TL;DR: The goal was to provide a focal point for investigators working from various perspectives on reconstructing relationships among the major areas of endemism and to identify key events that might be responsible for observed patterns of diversity and disjunction.
Abstract: The problem of Northern Hemisphere plant geography was framed long ago by the observation of striking floristic similarities between eastern North America and eastern Asia. Of primary importance was the work of Asa Gray, who produced a series of detailed comparisons of these floras (see Li 1952; Boufford and Spongberg 1983; Wen 1999). During the past several decades, two major symposia, “Floristics and Paleofloristics of Asia and Eastern North America” (Graham 1972) and “Biogeographical Relationships between Temperate Eastern Asia and Temperate Eastern North America” (Davidse 1983), served to highlight both the nature of the problem and the variety of approaches used to examine intercontinental discontinuities in plants. Not long afterward, two landmark papers by Tiffney (1985a, 1985b) provided a synthesis of paleobotanical and neobotanical data in the context of a dynamic view of Earth history and emphasized floristic exchange via both the North Atlantic and the Bering Land Bridges. In this context, Tiffney (1985b, p. 73) noted that “three-area tests of the variety suggested by cladistic biogeographers need to be made and analyzed to determine whether the eastern Asia–eastern North American similarity is a unique pattern or simply a distinctive subset of a larger pattern.” Over the last two decades we have witnessed remarkable progress in elucidating phylogenetic relationships at all levels, and the number of phylogenies of Northern Hemisphere plant clades has grown to the point that meaningful comparisons are now feasible. Furthermore, there have been major developments in the theory of biogeography as well as in our knowledge of relevant fossils and Earth-history events. The symposium from which the articles in this volume emerged was part of the Botany 2000 meetings in Portland, Oregon. It was designed to create a forum for new analyses of the Northern Hemisphere problem, bringing together a set of paleobotanists and phylogeneticists who have concentrated on relevant areas and plant groups. The goal was to provide a focal point for investigators working from various perspectives on reconstructing relationships among the major areas of endemism and to identify key events that might be responsible for observed patterns of diversity and disjunction. The analyses presented here represent the initial steps toward assembling a modern synthesis based on phylogenetic knowledge, fossil distributions, estimates of sequence diver

Journal ArticleDOI
TL;DR: The phylogenetic and physiological data in the Portulacaceae indicate a scheme for the evolution of CAM, possibly starting with changes in leaf anatomy, then progressing to increased enzyme activity with increased acid fluctuations, and finally ending with the development of the full CAM pathway.
Abstract: The plant family Portulacaceae is a relatively small family (∼19 genera and ∼425 species) with a widespread distribution. Species of the Portulacaceae range in size from small herbaceous plants to shrubs that measure up to 4 m in height. Most members of the family have leaves that range from fleshy to fully succulent and live in very diverse habitats ranging from shady understory plants to plants exposed to full sunlight. The Portulacaceae have members that utilize different photosynthetic pathways ranging from C3 to C4 to Crassulacean acid metabolism (CAM) to CAM‐cycling plants. We are interested in the prevalence of the CAM photosynthetic pathway in this family. We studied the nocturnal CO2 uptake, diurnal acid fluctuation, and phosphoenolpyruvate (PEP) carboxylase activity of different members of the Portulacaceae. Our results indicate the highest levels of CAM activity in the genera of Anacampseros, Portulacaria, Ceraria, and Talinopsis. Intermediate in their CAM activity were the genera Talinum, Port...

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TL;DR: Although the endoliths all have access to light, there was no significant correlation between the limit of their depth penetration and threshold quantum flux densities, indicating that the mechanisms controlling distribution and abundance of endolithic photoautotrophs are as complicated as those found for aquatic algae and cyanobacteria.
Abstract: To understand how light attenuation in limestone rock constrains the distribution and abundance of endolithic photoautotrophic organisms, we examined light‐level profiles in 25 rock samples containing endolithic algae and cyanobacteria. We collected samples from three representative cliff sites along the Niagara Escarpment, Canada, using methods that allowed us to make comparisons among as well as within sites. Photosynthetically active radiation profiles were generated by manufacturing cavities in the bottom of thick slabs of surface rock and enclosing radiation sensors in the cavities. The thickness of the flat layer of limestone between the sensor and a light source was then abraded in steps of ca. 0.5 mm. An exponential curve was fitted to the measurements for each sample to allow statistical comparisons of the light levels at different depths. We examined the correlations between physical characteristics of the rock and light attenuation and between light attenuation and the maximum depth, relative b...

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TL;DR: Differences in diversity of endemic genera between the two continents have resulted from different rates of speciation, immigration, and extinction, which have been primarily influenced by land connection, continental drift, geological history, geomorphologic configuration, and climate in the past.
Abstract: Biogeographic interpretations sometimes depend on endemism. The diversity of endemic genera of vascular plants in different phylogenetic groups was compared between East Asia and North America. North America has a significantly higher diversity of endemic genera of vascular plants than East Asia (987 vs. 754 genera). However, East Asia holds greater diversity of endemic genera than North America in pteridophytes, gymnosperms, and ranunculids, which are in general evolutionarily old taxa. The two areas do not significantly differ in the numbers of endemic genera in magnoliids and monocots. The overall diversity bias of endemic genera in favor of North America primarily results from caryophyllids, rosids, and asterids, which are relatively advanced lineages. As a result, numbers of endemic genera within phylogenetic groups do not vary in parallel between East Asia and North America. Compared with the world total flora with respect to proportions of numbers of taxa among phylogenetic groups, East Asia and No...