Showing papers in "International Journal of Plant Sciences in 2010"
TL;DR: The conceptual framework of population genomics is outlined, genomic patterns of variation are related to evolutionary processes, and major biological factors to be considered in studies of selection are identified.
Abstract: Natural selection shapes patterns of genetic variation among individuals, populations, and species, and it does so differentially across genomes. The field of population genomics provides a comprehensive genome-scale view of the action of selection, even beyond traditional model organisms. However, even with nearly complete genomic sequence information, our ability to detect the signature of selection on specific genomic regions depends on choosing experimental and analytical tools appropriate to the biological situation. For example, processes that occur at different timescales, such as sorting of standing genetic variation, mutation-selection balance, or fixed interspecific divergence, have different consequences for genomic patterns of variation. Inappropriate experimental or analytical approaches may fail to detect even strong selection or falsely identify a signature of selection. Here we outline the conceptual framework of population genomics, relate genomic patterns of variation to evolutionary pro...
188 citations
TL;DR: The phylogenies reveal that the closest relatives to Schiedea are a pair of widespread, largely Arctic taxa, Honckenya peploides and Wilhelmsia physodes, and are not reflective of natural groups; this study proposes abandoning this classification in favor of a new system that recognizes major lineages of the molecular phylogeny at the tribal level.
Abstract: Understanding the relationships within the Caryophyllaceae has been difficult, in part because of arbitrarily and poorly defined genera and difficulty in determining phylogenetically useful morphological characters. This study represents the most complete phylogenetic analysis of the family to date, with particular focus on the genera and relationships within the large subfamily Alsinoideae, using molecular characters to examine the monophyly of taxa and the validity of the current taxonomy as well as to resolve the obscure origins of divergent taxa such as the endemic Hawaiian Schiedea. Maximum parsimony and maximum likelihood analyses of three chloroplast gene regions (matK, trnL‐F, and rps16) from 81 newly sampled and 65 GenBank specimens reveal that several tribes and genera, especially within the Alsinoideae, are not monophyletic. Large genera such as Arenaria and Minuartia are polyphyletic, as are several smaller genera. The phylogenies reveal that the closest relatives to Schiedea are a pair of wid...
140 citations
TL;DR: It is demonstrated that pollinators can mediate selection on both traits likely to be involved in pollinator attraction and traits affecting pollination efficiency and that spatiotemporal variation in the strength of pollinator-mediated selection can contribute substantially to differences in selection between years and populations.
Abstract: Floral diversification and specialization are thought to be driven largely by interactions with pollinators, but the extent to which current selection on floral traits is mediated by pollinators has rarely been determined experimentally. We documented selection through female function on floral traits in two populations of the rewarding orchid Gymnadenia conopsea in two years and quantified pollinator-mediated selection (Δβpoll) by subtracting estimates of selection gradients for plants receiving supplemental hand pollination from estimates obtained for open-pollinated control plants. There was directional selection for taller plants, more flowers, larger corollas, and longer spurs in the study populations. Pollinator-mediated selection ranged from weak to moderately strong (Δβpoll, range −0.01–0.21, median 0.08). All observed selection on spur length could be attributed to interactions with pollinators, while the proportion of observed selection on plant height (0%–77%), number of flowers (13%–42%), and ...
94 citations
TL;DR: It is concluded that florivory is a major impediment to successful pollination and plant sexual reproduction of C. virginianum in areas where the species naturally occurs.
Abstract: Plants experience damage to both their vegetative and their reproductive parts. Loss of leaf area can affect subsequent photosynthesis and resources available for growth and reproduction; damage to flowers can result in loss of ovules and seeds by consumption, but herbivory may also disfigure flowers, interfering with their functions of attracting and rewarding pollinators. We examined natural populations of the butterfly pea, Centrosema virginianum, in pine rockland habitat in Everglades National Park (intact habitat) and a pine rockland fragment in suburban Miami‐Dade County to answer the following questions: (1) What is the breeding system of C. virginianum? (2) What are the pollinators of this species in southern Florida pine rocklands? And (3) how are flower herbivores affecting pollinator visitation and subsequent fruit set? Controlled hand‐pollination experiments revealed this species to be self‐compatible but requiring visitation/pollination for fruit set. Cross‐pollinated flowers and open‐pollina...
90 citations
TL;DR: In loculi containing many grains, the existence of mechanisms causing movement of locular fluid and pollen grains, enabling uniform nourishment of grains is postulated, enabling high percentage of viable grains in the loculus.
Abstract: Various parts of the anther (walls, tapetum, locular fluid, meiocytes, microspores) cooperate for correct pollen development. To show the different types of relationships possible between these parts, we considered the following characteristics, alone and in combination: types of tapetum, types of pollen‐dispersing unit, form of loculus, amount of locular space and fluid, number of pollen grains in transverse sections of the anther and in the loculus, and hydration status of pollen at dispersal. The different relationships between pollen, loculus, and tapetum should enable uniform nourishment of grains in the loculus and ensure a high percentage of viable grains. Two opposite modes were identified: direct and indirect nourishment of grains, the latter occurring when locular fluid is more or less abundant between the tapetum and the grains. The amount of space between developing grains determines different manners of grain nourishment and modes of pollen presentation for dispersal. Cyclosis, which is presu...
72 citations
TL;DR: Both pollinators and the seed predator exerted selection for less bright flowers, suggesting that they do not cause conflicting selection on flower color, andPollinators and herbivores are not sufficient to generate conflicting selection that could contribute to the maintenance of flower color variation in L. siphilitica.
Abstract: Conflicting selection by pollinators and herbivores is thought to be an important mechanism maintaining variation in flower color within plant populations. However, evidence for this mechanism is lacking because selection and the agents of selection on flower color have rarely been estimated. We estimated selection by pollinators and a predispersal seed predator on the three fundamental components of color (brightness, chroma, and hue) of Lobelia siphilitica flowers. We compared phenotypic selection on flowers of supplemental hand- versus open-pollinated plants to infer whether pollinators were an agent of selection on color. We compared attacked and unattacked plants to infer whether the seed predator was an agent of selection on color. Selection on brightness, but not chroma or hue, differed significantly between both pollination treatments and predation categories. Both pollinators and the seed predator exerted selection for less bright flowers, suggesting that they do not cause conflicting selection o...
63 citations
TL;DR: Levels of FA were more correlated with the proportion of genetic ancestry of each individual than with leaf morphology or altitude, supporting the hypothesis that hybridization is associated with development instability potentially caused by disruption of coadapted gene complexes characteristic of each species.
Abstract: We tested the effects of hybridization and introgression on the levels of leaf fluctuating asymmetry (FA) in a hybrid zone between Quercus magnoliifolia and Quercus resinosa at the Tequila volcano, Jalisco state, Mexico, in which the species are distributed along an altitudinal gradient ranging from 1400 to 2100 m. Bayesian clustering analysis was performed with STRUCTURE on data for eight nuclear microsatellite loci to assign individuals from reference populations and from the hybrid zone to pure or hybrid genotypic classes. To test the performance of the assignment procedure and to determine optimal thresholds for genetic assignment pure, hybrid and backcrossed genotypes were simulated (from the allelic frequencies found in real pure populations of the two species) and reanalyzed with STRUCTURE. Leaf FA and morphological identification of parental and hybrid individuals were obtained using geometric morphometric techniques. We found genetic and morphological evidence of a hybrid zone by secondary contac...
62 citations
TL;DR: It is found that, by contrast with conventional wisdom, corolla shape shows great variation even between co-occurring individuals, and this variation can have strong fitness consequences, with reproductive success being associated with specific corolla shapes.
Abstract: The evolution of flower shape has attracted the attention of biologists for at least two hundred years. Although much information is accumulating on the genetic architecture of flower shape, information on its adaptive significance is much scarcer. Using geometric morphometrics, we have explored the microevolution of corolla shape in Erysimum mediohispanicum during the past decade. We have found that, by contrast with conventional wisdom, corolla shape shows great variation even between co-occurring individuals. This variation can have strong fitness consequences, with reproductive success being associated with specific corolla shapes. Corolla shape seems to act in E. mediohispanicum as an honest signal, since it is associated with reward (nectar and pollen) and determines the preference pattern of important pollinators. Finally, since pollinator fauna varies geographically in this generalist plant species, we have detected a geographic mosaic of selection on E. mediohispanicum corolla shape in southeaste...
58 citations
TL;DR: A study of the species’ breeding system and associations with flower‐visiting insects, along with an analysis of its floral scent composition, suggests a local reproductive dependence of the plant to this scarab beetle species.
Abstract: Philodendron acutatum (Araceae) is a hemiepiphyte common to the Atlantic Forest of northeastern Brazil In two localities, we studied the species’ breeding system and associations with flower‐visiting insects, along with an analysis of its floral scent composition The fruit set of self‐incompatible P acutatum was high, more than 90%, and inflorescences were exclusively pollinated by one species of scarab beetle, Cyclocephala celata (Scarabaeidae, Dynastinae) Pollinators are drawn toward the inflorescences at dusk by strong floral fragrances given off during the female phase of anthesis, along with endogenous heating of the spadix, whose temperatures were recorded at more than 11°C above ambient air Two other species of flower‐visiting Cyclocephala were also consistently recovered in blacklight trappings during the flowering period of P acutatum The fact that only C celata was found in association with P acutatum suggests a local reproductive dependence of the plant to this scarab beetle species D
58 citations
TL;DR: The results of a field study of physiological and fitness-related traits in geographically proximate sister taxa in the annual wildflower genus Clarkia (Onagraceae) are reported and the differences between them are interpreted in light of their ecological and reproductive differences.
Abstract: Consistent differences in the physiological performance of wild populations of closely related plant taxa may be the result of environmentally induced phenotypic plasticity or adaptive evolution (or a combination of the two). Here we report the results of a field study of physiological and fitness-related traits in geographically proximate sister taxa in the annual wildflower genus Clarkia (Onagraceae) and interpret the differences between them in light of their ecological and reproductive differences. Within two pairs of taxa, the predominantly autogamous (self-fertilizing) taxon flowers and completes its life cycle before its pollinator-dependent (predominantly outcrossing) counterpart growing in sympatry or at similar elevations in the southern Sierra Nevada. Selfers generally exhibited higher rates of photosynthesis and transpiration than their outcrossing sister taxa, and, except for the earliest-flowering (autogamous) taxon, both photosynthetic and transpiration rates tended to decline as the season...
56 citations
TL;DR: The results supported the monophyly of bolbitidoid ferns and of Arthrobotrya, Elaphoglossum, Lomagramma, and Teratophyllum; however, Bolbitis was resolved as polyphyletic.
Abstract: We performed a phylogenetic analysis of the traditionally recognized genera of bolbitidoid ferns (i.e., Arthrobotrya, Bolbitis, Elaphoglossum, Lomagramma, and Teratophyllum) using two noncoding chloroplast spacers: trnL‐trnF and rps4‐trnS. The sampling included 57 species, of which 55 had not been sequenced previously. The results supported the monophyly of bolbitidoid ferns and of Arthrobotrya, Elaphoglossum, Lomagramma, and Teratophyllum; however, Bolbitis was resolved as polyphyletic. A clade of eight Neotropical species currently placed in Bolbitis is sister to Elaphoglossum, not the other species of Bolbitis. We refer to this group of species as the Bolbitis nicotianifolia clade. Lomagramma (or Bolbitis) guianensis, whose generic placement has been uncertain, was found to belong to the B. nicotianifolia clade. Bolbitis s.s. was resolved sister to the rest of the bolbitidoid ferns, which are in turn divided into two clades, one consisting of Elaphoglossum and the B. nicotianifolia clade and the other ...
TL;DR: It is concluded that specialized pollination requirements do not present a barrier to invasions when plants are specialized to pollinators or pollinator functional groups with very wide distributions.
Abstract: Generalized pollination systems and autonomous self‐fertilization are traits that have been linked with plant invasiveness. However, whether specialized pollination requirements pose a significant barrier to plant invasions is not yet clear. Likewise, the contribution of pollinators to the fecundity of facultatively self‐pollinating invasive plant species is poorly understood. We addressed these issues using the self‐compatible and autonomously self‐pollinating Lilium formosanum, which also has large, showy flowers that are adapted for pollination by hawk moths. We investigated the pollination of this lily—which is indigenous to Taiwan—in KwaZulu‐Natal, South Africa, where it is invasive. The long‐tongued hawk moth Agrius convolvuli was identified as the primary pollinator on the basis of field observations, pollen load analysis, presence of lepidopteran scales on stigmas, and higher seed production in emasculated flowers exposed at night than in those exposed during the day. Remarkably, this moth is nati...
TL;DR: This work compares several multivariate methods that calculate genetic constraint using a quantitative genetic field study in the ivyleaf morning glory, Ipomoea hederacea, and finds high levels of inferred constraint and discordance between methods that consider the geometric orientation of G and β and those that evaluate how covariances affect the short-term rate of adaptation.
Abstract: The ability of a population to respond to natural selection will be determined by the patterns of genetic variation and covariation in traits under selection. In the quantitative genetic framework, these patterns of genetic variation and covariation are described by the G matrix, which for a given pattern of selection will determine the size and direction of evolutionary responses. Several methods have been developed to evaluate the nature of evolutionary constraints imposed by G, although this multitude of methods has never been applied to a common data set to compare their strengths and weaknesses, or the similarity of evolutionary inferences they produce. Here we compare several multivariate methods that calculate genetic constraint using a quantitative genetic field study in the ivyleaf morning glory, Ipomoea hederacea. We focus on a tractable number of traits (size at flowering, final size, and flowering time), which allows us to pair multivariate quantitative methods with qualitative interpretations...
TL;DR: The results demonstrate the value of using a priori models of natural selection to guide hypothesis testing and support the prediction that fitness trade-offs can constrain adaptive evolution in invasive species.
Abstract: Theory suggests that the contemporary evolution of local adaptation may increase the rate of biological invasion, yet natural selection has rarely been measured in invasive species. A recently published model predicted that latitudinal variation in the strength of stabilizing selection on two correlated traits—flowering time and size—can result in local adaptation during plant invasion but implicitly assumed that population × environment interactions are weak. We tested for stabilizing selection and the effect of growing environment on 13 populations of the invasive plant Lythrum salicaria sampled along a latitudinal gradient. Plants were grown under uniform glasshouse conditions and in a 3-year common garden field experiment at midlatitude. Consistent with model assumptions, the ranking of population means was highly correlated across the 3 years, and with glasshouse measurements, despite significant interannual differences in flowering time and vegetative size. As predicted, the first principal componen...
TL;DR: There was no evidence that SC increased toward the northern range limit as a result of the invasion process, and there was a significant effect of style morph on variation in SC, with the mid‐styled morph most compatible.
Abstract: Colonization may favor self‐compatibility (SC) in invasive plants, a process consistent with Baker’s law. We investigated this hypothesis in invasive eastern North American populations of tristylous Lythrum salicaria L. (purple loosestrife) by controlled self‐ and cross‐pollinations of 124 plants sampled from 12 populations grown under uniform glasshouse conditions. We evaluated whether populations at the northern front of the invasion exhibited higher levels of SC than southern populations, which are closer to source populations for the North American invasion. We also sought evidence for morph‐specific differences in the strength of trimorphic incompatibility. We used the ASTER statistical program to jointly model three measures of SC: (1) the probability of producing at least one seed following self‐pollination, (2) the number of fruits produced by self‐pollination, and (3) the average number of seeds per fruit resulting from self‐pollination. Just over one‐quarter of plants set at least one fruit afte...
TL;DR: Comparing Telemachus with the permineralized Middle Triassic conifer seed cone Parasciadopitys from the Central Transantarctic Mountains makes it possible to relate organs in different preservational modes and to develop a more complete concept for this widely distributed Gondwana conifer.
Abstract: The seed cone Telemachus is known from several Triassic localities in Gondwana. New specimens from two localities in Antarctica provide additional information about the type species, Telemachus elongatus, based on details of morphology and anatomy revealed by using a modified transfer technique on the compressed plants. Seed cones of T. elongatus are up to 6.0 cm long and characterized by conspicuous, elongate bracts. A second Antarctic species, described here as Telemachus antarcticus, is segregated, based on a shorter bract and differences in cone size. Newly recognized features of the genus include the shape, size, and disposition of the ovules; vascularization of the ovuliferous complex; and scale and bract histology. As a result of this new information, it is now possible to compare Telemachus with the permineralized Middle Triassic conifer seed cone Parasciadopitys from the Central Transantarctic Mountains. The similarities between the two genera make it possible to relate organs in different preser...
TL;DR: Pulse amplitude modulation (PAM) fluorometer techniques provide unique information on photosynthetic activity of CAM plants such as the orchid Dendrobium spp.
Abstract: Pulse amplitude modulation (PAM) fluorometer techniques provide unique information on photosynthetic activity of CAM (crassulacean acid metabolism) plants such as the orchid Dendrobium spp. (cv. Viravuth Pink). CAM plants close their stomata for at least part of the day, creating a sealed compartment in the stems and leaves that precludes measurement of the light reactions of photosynthesis by any gas exchange–based method. PAM machines calculate photosynthesis as the electron transport rate (ETR) through PSII (four electrons per O2 produced) as mol m−2 s−1. Photosynthesis‐versus‐irradiance (P‐vs.‐E) curves fitted the waiting‐in‐line function ( \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} \renewcomma...
TL;DR: This work quantified pollinator visitation, pollen deposition, and pollen limitation of reproduction in the invasive shrub Lonicera maackii in adjacent forest edge and forest interior habitats to identify different mechanisms of pollen limitation characterize these habitats.
Abstract: Many nonnative plants require pollinators to produce the seed needed to establish beyond their native range. Local variation in pollination can cause variation in mating patterns, reproductive output, genetic diversity, and selection, which can influence invasion dynamics. We quantified pollinator visitation, pollen deposition, and pollen limitation of reproduction in the invasive shrub Lonicera maackii in adjacent forest edge and forest interior habitats. Flowers in edge habitats received as many or more pollinator visits than those in interior habitats, resulting in twofold greater pollen deposition and nearly twice as many seeds produced per flower. Supplemental pollination increased seed production over open pollination by 37%–145% in both edge and interior habitats. Edge flowers produced more seed than interior flowers. Despite greater pollen deposition in edge habitats, the magnitude of pollen limitation was similar to interior plants. Thus, different mechanisms of pollen limitation characterize the...
TL;DR: An emended diagnosis including apomorphic characters is given for the genus, as well as a lectotypification of the genus and the type‐species, and the growth habit of Cooksonia is discussed.
Abstract: The genus Cooksonia Lang 1937 includes some of the earliest land plants. Specimens of Cooksonia pertoni Lang 1937 are considered the earliest Eutracheophytes. The definition of the genus is thus central to the delineation of the clade. However, the generic diagnosis is problematic. It is not restrictive enough, and most of the few diagnostic characters are plesiomorphic. Observations on new specimens of Cooksonia paranensis Gerrienne et al. 2001, a species very close to C. pertoni, considered along with a compilation of the Cooksonia literature, allow us to propose more precise diagnostic characters. An allometric study was performed on more than 100 specimens of C. paranensis. This study allows discrimination of true morphological variations from growth stages. The growth habit of Cooksonia is discussed. An emended diagnosis including apomorphic characters is given for the genus, as well as a lectotypification of the genus and the type‐species.
TL;DR: Paleobotanical data confirm that the megaphyllous leaf evolved independently several times from the Middle Devonian to the Early Carboniferous, and fundamental differences in their petiole anatomy support the early divergence of the two groups.
Abstract: Paleobotanical data, with emphasis on anatomical characters in ferns and seed plants, confirm that the megaphyllous leaf evolved independently several times from the Middle Devonian to the Early Carboniferous. Fernlike cladoxylaleans and aneurophytalean progymnosperms possessed only megaphyll precursors homologous with the small megaphylls of archaeopteridalean progymnosperms. Different trends toward developing a large megaphyll, from the modification of lateral branch systems of some basal euphyllophytes, are shown by the fernlike rhacophytaleans and by the zygopterid and tedelean ferns. Zygopterids, with their tridimensional frond, petiole of the phyllophore type, and annulate sporangia, must be considered as the earliest undisputable ferns while the probably derived tedeleans have evolved toward a convergent filicalean‐type of frond. The leaf of other early ferns certainly derived through a minimal change in anatomy from other Devonian euphyllophytes. Early seed plant leaves probably evolved through th...
TL;DR: Seeds of two palm species conforming to the extant genus Sabal have been recovered from the Aguja Formation of Big Bend National Park, Texas, and the co‐occurrence of palm seeds with numerous juvenile hadrosaur and ceratopsian bones indicates that palms closely related to modern cabbage palms may have provided fodder and shelter for young herbivorous dinosaurs.
Abstract: Seeds of two palm species conforming to the extant genus Sabal have been recovered from the Campanian (Upper Cretaceous) Aguja Formation of Big Bend National Park, Texas: Sabal bigbendense sp. nov. and Sabal bracknellense (Chandler) Mai. These remains, found together with anatomically preserved palm stems, augment previous reports of Sabalites ungeri (Lesq.) Dorf leaves from the same formation. The co‐occurrence of palm seeds with numerous juvenile hadrosaur and ceratopsian bones indicates that palms closely related to modern cabbage palms may have provided fodder and shelter for young herbivorous dinosaurs. The distribution of these and other Late Cretaceous palm fossils is reviewed.
TL;DR: Control pollinations showed evidence for inbreeding depression in progeny of hermaphrodites and gynomonoecious individuals, affecting both pre‐ and postdispersal traits; this could provide a selective advantage for females.
Abstract: Gynodioecy involves the stable co‐occurrence of females and hermaphrodites. Its maintenance theoretically depends on differences in female and male reproductive success among gender morphs. Although many gynodioecious species also include gynomonoecious individuals that carry a mixture of female and perfect flowers, little is known about the male and female fitness of this third morph. Here, we present the first study of the reproductive system of Silene nutans, including females, gynomonoecious plants, and hermaphrodites. By measuring 10 floral traits in controlled conditions, we showed that females bear smaller and lighter flowers than hermaphrodites, with female and perfect flowers of gynomonoecious plants being intermediates. By measuring pollen quantity and quality, we showed that gynomonoecious plants had a lower potential male fitness than hermaphrodites at the level of both flowers and individuals. In addition, gynomonoecious plants were shown to widely vary their proportion of female flowers (0.0...
TL;DR: The timing of specific key events and a morphological and anatomical description of important features of S. apoda such as habit, stem, rhizophores, roots, leaves, ligules, strobili, sporangia, spores, and gametophytes are presented.
Abstract: Selaginella apoda is an appropriate model species because of its short life cycle and ease of cultivation. To work effectively with a model species, it is important to understand its morphology, anatomy, and life cycle in detail. We present the timing of specific key events (e.g., opening of the megaspore, development of the archegonium, fertilization, first branching) and a morphological and anatomical description of important features of S. apoda such as habit, stem, rhizophores, roots, leaves, ligules, strobili, sporangia, spores, and gametophytes, with many features newly described for Selaginella in general and for S. apoda in particular. Development and growth patterns indicate that each segment is an independent module consisting of a section of the stem, leaves, rhizophores, and roots. A comparison of different leaf types (dorsal and ventral leaves, dorsal and ventral sporophylls) shows similar stomata and papillae distributions but type‐specific forms and sizes. In the transition from vegetative ...
TL;DR: In Ranunculus, the origin of the open arctic biome primarily favored range expansions of taxa/species already adapted to wet habitats in cold areas and depending on rapid dispersal, without development of obvious special traits in the adaptation to arctic environments.
Abstract: The arctic biome is a relatively young ecosystem with ∼2300 species of vascular plants. We studied the genus Ranunculus as an example of the origin and evolution of the arctic flora. For this purpose we used molecular phylogenetic and clock analyses based on evaluation of nuclear ITS and chloroplast matK‐trnK DNA sequences in 194 taxa of Ranunculus and closely related genera. Taxa occurring in the Arctic arose from seven phylogenetic lineages of Ranunculus and also in the genera Coptidium and Halerpestes. Two clades of Ranunculus are species‐rich in the Arctic, i.e., Ranunculus sect. Ranunculus and R. sect. Auricomus (both from R. subg. Ranunculus), but this is due to a number of arctic “microtaxa” morphologically barely separate from R. acris in the former clade and the widely agamospermic species complex of R. auricomus in the latter. Lineages with species adapted to wetlands or aquatic habitats are significant groups represented in the arctic flora (R. subg. Ranunculus sectt. Flammula and Hecatonia/Xan...
TL;DR: It is suggested that selection on floral spur length can differ between genders and that this gender bias may be affected by the pollinator context, and interpretation of selection through male function based only on pollen removal can lead to erroneous conclusions.
Abstract: Selection on floral traits in hermaphrodite plants can operate through either male or female sex function. However, selection is typically measured for the female component only, and when selection through male function is measured, it is usually done only in terms of pollen removal from flowers. We tested whether selection on floral spur length might differ between genders in the orchid Satyrium longicauda by measuring the effect of spur length manipulations on pollen receipt and export of color-labeled pollen to conspecific stigmas. This was done in two populations with different pollinator faunas to determine whether pollinator context influenced the relationship between spur length and gender-specific fitness components. In one population, spur length manipulation had opposite effects on sex functions, while in the other, both pollen export and receipt were reduced by spur shortening. Furthermore, measures of male function through pollen removal and pollen export did not always correspond. These resul...
TL;DR: The Cenozoic fossil record of Humiriaceae in South and Central America, together with discreditation of former reports from Europe, strongly supports a Neotropical origin for this family.
Abstract: To place a new fossil occurrence of Sacoglottis in a broader context, we surveyed the fruit morphology of all extant genera of the Humiriaceae, conducted a cladistic analysis, and critically reviewed the fossil record for this family. Living and fossil fruits of Humiriaceae are recognized by a woody endocarp, germination valves, and, in some genera, wall cavities. The phylogenetic analysis based on 40 morphological characters yielded two most parsimonious trees indicating Vantanea as sister taxon to all genera among Humiriaceae. Schistostemon is indistinguishable from Sacoglottis in fruit morphology and is recovered as sister to Sacoglottis in the topology; we recommend restoring Schistostemon to the rank of subgenus within Sacoglottis. A review of prior published reports of fossil fruits attributed to Humiriaceae led to the rejection and/or reattribution of some records but supports recognition of Vantanea, Humiria, Humiriastrum, and Sacoglottis. The available characters do not support recognition of mul...
TL;DR: The gene expression patterns observed suggest that the innermost petals of Nymphaea originated from petaloid staminodes, and it is inferred that either the “out‐of‐male” hypothesis or the ‘mostly male’ hypothesis, both of which specify derivation of floral parts from male structures, might apply to the ancestors ofNymphaeales.
Abstract: To provide insights into the floral developmental genetics of Nymphaeales (water lilies), we investigated the expression patterns of floral organ identity genes in three genera: Cabomba, Nuphar, and Nymphaea. Additionally, because of the superficial floral similarity between Nymphaea and the early‐diverging eudicot Nelumbo, we conducted the same experiments in the latter taxon. We focused on gene expression associated with (1) perianth differentiation in Nymphaeales, (2) the transition of petaloid staminodes to stamens in Nymphaea, and (3) organ identity in Nymphaea and Nelumbo. In Cabomba, the expression patterns of B‐class gene homologues fit the “sliding boundaries” model, with B‐class gene expression in sepals and petals. In contrast, Nuphar and Nymphaea exhibit broad B‐class gene expression that extends across all floral organs (i.e., “fading borders” model). The gene expression patterns observed suggest that the innermost petals of Nymphaea originated from petaloid staminodes. Also, despite the morp...
TL;DR: Among populations, plant size and fruit production increased with water potential, though seedling‐to‐adult mortality was independent, and plant water status was inferior on shallow slopes with hard, fine soils.
Abstract: Low precipitation can limit plant distributions. Soil variation might interact with precipitation gradients to define species borders. Analyzing the eastern species border of the California annual Clarkia xantiana ssp. xantiana, we assessed the following: (1) the geography of plant water status, precipitation, and soil; (2) soil control of plant water status; and (3) water status control of plant performance. Plant water potential declined toward the border in consecutive years. Precipitation declined in parallel and was lower in the year of lower water potential. Many border soils are derived from metasedimentary rock, while igneous rock dominates the species range to the west and unoccupied areas to the east. Compared with igneous soils, metasedimentary soils were found to have greater penetration resistance and finer texture, and they exhibited greater water storage capacity but also stronger restrictions on water release. Within populations, plant water status was inferior on shallow slopes with hard,...
TL;DR: Overall, the strong similarity of RAPD and allelic phenotypes throughout Argentina suggests a limited number of introduction events, that the species spread through human transport, and that the few genetic phenotypes present in the species were conserved largely unaltered as a result of mainly asexual reproduction.
Abstract: Rosa rubiginosa (Rosaceae) populations introduced to Argentina successfully invade various habitats, forming extensive impenetrable thickets. To investigate the consequences of founder events and to track the native origin of Argentinean populations, the genetic diversity of invasive R. rubiginosa populations was compared with that of native populations in Europe, and genetic similarity was assessed between groups. We sampled 13 Argentinean populations and 20 native populations in Germany and Spain, and we applied two molecular marker techniques (simple sequence repeats and random amplification of polymorphic DNA [RAPD]). Genetic diversity within the invasive range was clearly lower than it was in the native range. Principle coordinate analysis and between-class analysis did not reveal the exact European origin of the invasive populations, but our data suggest that at least one Argentinean population originated in Germany. Overall, the strong similarity of RAPD and allelic phenotypes throughout Argentina suggests a limited number of introduction events, that the species spread through human transport, and that the few genetic phenotypes present in the species were conserved largely unaltered as a result of mainly asexual reproduction.
TL;DR: It is suggested that, under conditions of global climate change, water stress may have a stronger effect on plant performance than UVB radiation.
Abstract: Relatively few studies have investigated plant responses to the combined effects of multiple environmental factors. We studied the responses of canola (Brassica napus) seedlings to combinations of temperatures (22°/18°C and 28°/24°C), ultraviolet‐B (UVB) radiation levels (5 [ambient] and 10 [enhanced] kJ m−2 d−1), and watering regimes (well watered and water stressed). The higher temperature decreased stem diameter, leaf area, individual organ and total‐plant dry mass (DM), net CO2 assimilation (AN), water use efficiency (WUE), the chlorophyll (Chl) a–Chl b ratio, and UV‐absorbing compounds but increased specific leaf mass (SLM), leaf mass ratio (LMR), shoot‐root ratio (SRR), and Chl b. Enhanced UVB reduced leaf number and area, DM accumulation, SLM, LMR, AN, WUE, carotenoids, and Chl a:Chl b but increased leaf area ratio, SRR, and ethylene evolution. Water stress decreased plant growth, leaf moisture, leaf, stem, and total DM, LMR, SRR, and gas exchange but increased photosynthetic pigments, UV‐absorbing...