Showing papers in "Plant Ecology and Evolution in 2015"

Inter- and intra-specific variability in seed dormancy loss and germination requirements in the Lavatera triloba aggregate (Malvaceae)

Abstract: Background and aims – The genus Lavatera is comprised of perennial and annual species that grow in different ecosystems such as coastal cliffs, plains, endorheic lagoons and ditches. In this study, we compared the seed germination ecology of three phylogenetically related taxa: L. agrigentina, L. triloba subsp. pallescens and L. triloba subsp. triloba, all of which belong to the L. triloba aggregate (section Glandulosae) and grow on chalky plains, limestone cliffs and endorheic lagoons with clayey sediments. Methods – For each taxon, the effects of seed scarification and dry after-ripening (90 days at 25°C) on seed dormancy loss and of light and temperature (constant 5 to 25°C and alternating 25/10°C) on seed germination were evaluated. Key results – Scarification allowed water imbibition and subsequent seed germination, indicating physical dormancy (PY) for all three investigated taxa. In addition, dry after-ripening positively affected seed germination in L. agrigentina, thus, seeds of this species have combinational dormancy [physical (PY) + physiological (PD)]. Light did not affect the final germination in any of the taxa. The germination response to incubation temperatures varied among the taxa, suggesting ecological adaptations, with the highest germination in the range of 10–20°C for L. agrigentina and L. triloba and 5–15°C for L. pallescens. Interpopulation variability in final germination was detected for both L. agrigentina and L. triloba subsp. triloba and in germination rate only for L. agrigentina. Conclusions – The three Lavatera taxa differed in their germination requirements, and these could be related to the habitat/ecology of each taxon. Our results suggest that seeds of the three taxa can germinate in the field from autumn to spring, when conditions are favourable for seedling establishment in the Mediterranean climate.

A synopsis of Soyauxia (Peridiscaceae, formerly Medusandraceae) with a new species from Liberia

Abstract: Background – Botanical exploration of the Sapo National Park in Liberia resulted in the discovery of a new species, which, after DNA investigation, was identified as belonging to Soyauxia of the small family Peridiscaceae. Methods – Normal practices of herbarium taxonomy and DNA sequence analysis have been applied. All the relevant herbarium material has been studied, mainly at BR, K, P, and WAG. The presented phylogenetic relationships of the new Soyauxia species is based on rbcL gene sequence comparison, inferred by a RAxML analysis including 100 replicates fast bootstrapping. The distribution maps have been produced using Map Maker Pro. Relevant collection data are stored in the NHN (Nationaal Herbarium Nederland) database. Key results – The new species Soyauxia kwewonii and an imperfectly known species are treated in the framework of a synopsis with the six other species of the genus. rbcL sequence comparison followed by RAxML analyses yielded a well-supported match of S. kwewonii with the Soyauxia clade. Its conservation status according to the IUCN red list criteria is assessed as Endangered. Its distribution as well as the distribution areas of the genus and of the remaining species are mapped. Soyauxia ledermannii is neotypified and the most common species in Gabon, S. glabrescens, is also illustrated.

New data on the recent history of the littoral forests of southern Cameroon: an insight into the role of historical human disturbances on the current forest composition

Abstract: Background and aims–Prior to European colonisation of Central Africa, human populations were dispersed through the forests, where they practiced slash-and-burn cultivation. From the 19th century they were progressively concentrated in villages along roads, leaving large areas of forest derelict. In south-western Cameroon, and elsewhere in Central Africa, forest canopy is dominated by long-lived lightdemanding tree species, suggesting a possible role of human disturbance. The aim of this study was to bring new insights into the possible effect of historical human disturbances in terms of timing and spatial extent on the current forest composition. Location–Wet evergreen littoral forest in south-western Cameroon. Methods and key results–A combined vegetation sampling and archaeobotanical survey were conducted. Potsherds, oil-palm endocarps, and charcoal were found throughout the study area, suggesting generalised human occupation and anthropogenic fire. Human occupancy occurred in two periods: between 2200 and 1500 BP, and, more recently, beginning three centuries ago. High frequency of fire and the presence of Elaeis guineensis both dated recently (between 260 and 145 BP) suggest slash-and-burn shifting cultivation practices. These human-induced disturbances may coincide with the age of the current emergent lightdemanding species, the age of which can be estimated around 200 years, or with the phases of drying climate recorded in the Central African forest in the early 18th century. Conclusions–These results support the idea that historical human disturbances are one of the major factors that shaped the current forest composition in Central Africa.

Biomass, phorophyte specificity and distribution of Tillandsia recurvata in a tropical semi-desert environment (Chihuahuan Desert, Mexico)

Abstract: Background and aims In low-precipitation environments, vascular epiphytes are expected to present low abundance and species richness, and could be restricted to inhabit a small number of phorophyte s

Relationships among floral VOC emissions, floral rewards and visits of pollinators in five plant species of a Mediterranean shrubland

Abstract: Background and aims – In plant-pollinator communities seasonal changes in the abundance of pollinators lead to seasonal changes in competition among flowering plants for their services. Here we address the following question: Do flowers of a given species produce more olfactory signals (emissions of volatile compounds) and rewards (nectar and pollen) during the phase(s) of the flowering period within which they have to maximally compete with the signals and rewards of other co-flowering species in the community, compared to the amount of signals and rewards produced during the period(s) with less floral competition? Methods – We analysed the floral emission rates of biogenic volatile organic compounds by gas chromatography and proton transfer reaction mass spectrometry, the visitation rates of pollinators, and the availability of nectar and pollen during the flowering periods of five species to test whether floral rewards and signals would decrease with an increase in pollinator visitation rates during late spring and early summer, i.e. coinciding with decreasing competitive pressure for the services of pollinators. Key results – The results indicate that phenological patterns in the production of rewards are only present at the species level in those species with long flowering periods or with matching periods of changes in pollinator populations. The capacity of emitting isoprenoids and oxidised volatile organic compounds, however, did not present significant patterns during the flowering period in any of the five species studied. Conclusions – The results support the hypothesis of a decreasing competitive pressure for the attraction of pollinators that may drive a decrease in floral investment in rewards but not an accompanying decrease of the capacity of emitting volatile olfactory signals in a species with long flowering period. However, the negative correlation between nectar production and visitation rates may be reinforced by the opposite responses of these variables to climatic conditions. This fact makes difficult to discern possible evolutionary forces tending to decrease rewards from plastic responses to changing environmental conditions in that part of the flowering period in which pollinator visitation rates are higher .

Reproductive morphology in the Gnetum cuspidatum group (Gnetales) and its implications for pollination biology in the Gnetales

Abstract: Background and aims - The Gnetales include the extant genera Gnetum, Ephedra and Welwitschia. They are usually functionally dioecious, but male cones often have sterile (but pollination drop-producing) ovules in addition to male units. There are, however, exceptions, i.e. most species of Ephedra and African species of Gnetum. Furthermore, the literature contains conflicting information on the Asian Gnetum cuspidatum. One study states that sterile ovules are present in this species; another that they are absent. The latter also claims that male cones secrete nectar instead, which is interesting because nectar has only been suggested to be present in four gymnosperm species. Here we aim to elucidate whether or not sterile ovules are present in male cones of G. cuspidatum and related taxa, evaluate evidence for nectar being present in gymnosperms and discuss implications for pollination biology. Methods - Male cones from relevant taxa were examined using a dissecting microscope and scanning electron microscopy. Key results - Sterile ovules are present in G. cuspidatum and the related G. macrostachyum, G. microcarpum, G. diminutum and G. loerzingii, but they are minute, hidden among hairs, and easily overlooked. No indications of nectar or nectaries were found and their presence in Asian species of Gnetum is questioned. Conclusions - Insect pollination is probably ancestral in the Gnetales. Like most species of Gnetum, members of the G. cuspidatum group have sterile ovules in male cones, and they can thus attract pollinators to both male and female plants using sweet pollination drops. Although it is possible that these species, in addition, produce extraovular reward for pollinators, we find no such evidence. Instead, it seems plausible that pollination drops have been mistaken for (extraovular) nectar. However, African species of Gnetum have unisexual male cones. Have they developed another means of pollinator reward in male plants or are they wind-pollinated as are their ephedran analogues?

Reduced fecundity and genetic diversity in small populations of rewarding versus deceptive orchid species: a meta-analysis

Abstract: Background and aims Understanding how plant traits mediate the relationship between plant population size, fitness and genetic diversity is fundamental to conservation. Many orchid species are threat

An illustrated and annotated checklist of freshwater diatoms (Bacillariophyta) from Livingston, Signy and Beak Island (Maritime Antarctic Region)

Abstract: Background and aims – Non-marine diatom communities in the Antarctic Region are characterized by a typical species composition, dominated by a large number of Antarctic endemic species. Despite recent advances in our knowledge about the diversity and biogeography of non-marine Antarctic diatoms, the flora of many Antarctic localities is still only poorly known, which can result in incorrect conceptions of species' distributions. The present paper provides a taxonomically consistent illustrated checklist of the diatom flora observed in recent and (sub)fossil non-marine sediments of three islands in the proximity of the northern Antarctic Peninsula, namely; Signy Island (South Orkneys), Livingston Island (South Shetlands) and Beak Island (James Ross Island group). Methods – The diatom flora of 66 samples collected from a wide variety of lakes and localities on the three above-mentioned islands has been studied using light and scanning electron microscopy. The biogeographical distribution of the composing taxa has been assessed on the basis of quality-checked distribution data from the recent literature. Key results – One hundred and two diatom taxa, belonging to thirty-four genera, were observed. Pinnularia (twelve taxa), Chamaepinnularia, Luticola, Planothidium, Psammothidium and Stauroneis (seven taxa each), Nitzschia (six taxa), Humidophila and Navicula (five taxa each) proved to be the most species-rich genera. Original morphometric data (including length, width and stria density) and illustrations are presented for all taxa observed. Forty-one species are hitherto only known from the Antarctic region. The exact taxonomic identity of twenty species remains uncertain and requires further study. It is suspected that many of these will also turn out to be restricted to the Antarctic region, suggesting that about half of all taxa observed are probably endemic to the Antarctic. Conclusions – The diatom flora of the three investigated localities comprises a large proportion of typical Antarctic taxa, many of which have only recently been split off from their presumably cosmopolitan relatives.

Structure and composition of the liana assemblage of a mixed rain forest in the Congo Basin

Abstract: Background and aims – The Congo Basin lowland forest represents one of the largest tropical forest blocks in the world, but its liana assemblage has never been characterized. We evaluate liana floristics, diversity, and structure in the Ituri Forest, and determine the effects of forest structure and edaphic variation on liana species composition. Methods – Two permanent 10-ha plots (200 × 500 m), 500 m apart, were established in mixed forest. All liana individuals = 2 cm dbh were identified, measured, mapped, and marked. For 20 × 20 m subplots we distinguished terra firme and swamp, and we estimated canopy openness. Key results – The combined 20-ha area contains 15,008 lianas (dbh = 2 cm) representing 195 species, 83 genera, and 34 families. Per hectare, species number averaged 64, mean basal area was 0.71 m2 and mean Fisher's alpha, Shannon index, and Simpson diversity index values were 17.9, 3.1 and 11.4, respectively. Ten dominant plant families represented 69% of total species richness, 92% of liana abundance and 92% of basal area, while ten dominant species accounted for 63% of abundance and 59% of basal area. A single species, Manniophyton fulvum, dominated the liana community (22% of all individuals). Forty-one species (21%) had one individual only. Twiners, zoochorous, light-demanding, and meso- or microphyllous species dominated. Liana abundance increased with abundance of medium-sized and large trees but was, surprisingly, independent of small-tree abundance. Canopy openness, habitat type, and tree size were the most important factors influencing abundance and distribution of liana individuals. Conclusions – The Ituri liana assemblage stands out by showing an extreme one-species dominance. Species floristic composition is, however, generally similar to that in other tropical African forests.

Reproductive biology of Pentadesma butyracea (Clusiaceae), source of a valuable non timber forest product in Benin.

Abstract: Background and aims – The main reproductive traits of the native African food tree species, Pentadesma butyracea Sabine (Clusiaceae), which is threatened in Benin and Togo, were examined in Benin to gather basic data necessary to develop conservation strategies in these countries. Methodology – Data were collected on phenological pattern, floral morphology, pollinator assemblage, seed production and germination conditions on 77 adult individuals from three natural populations occurring in the Sudanian phytogeographical zone. Key results – In Benin, Pentadesma butyracea flowers once a year during the dry season from September to December. Flowering entry displayed less variation among populations than among individuals within populations. However, a high synchrony of different floral stages between trees due to a long flowering period (c. 2 months per tree), might still facilitate pollen exchange. Pollen-ovule ratio was 577 ± 213 suggesting facultative xenogamy. The apical position of inflorescences, the yellowish to white greenish flowers and the high quantity of pollen and nectar per flower (1042 ± 117 μL) represent floral attractants that predispose the species to animal-pollination. The main pollinators were two sunbirds (Cyanomitra verticalis, Cinnyris coccinigastrus) and three Hymenoptera (Apis mellifera, Meliponula togoensis, Hypotrigona sp.). Mean fruit set reached 49%, and absolute fruit production increased with tree size. Seeds were desiccation-sensitive (i.e. recalcitrant) with a maximum duration of hydrated storage of three months. Germination of seeds was most successful and rapid at 30°C (50% after nine days). Conclusions – Our results indicate that the natural reproduction of P. butyracea is not limited by its ecology so that we hypothesize anthropogenic activities to be the reason for the threatened status of P. butyracea in Benin and Togo. However, due to its recalcitrant seeds, the conservation of its genetic resources is not feasible through ex situ conservation of seed banks but in situ strategies and/or ex situ conservation in orchards should be successful.

Reproductive biology of Primula beesiana (Primulaceae), an alpine species endemic to Southwest China.

Abstract: Background and aims - Primula beesiana Forrest is a perennial alpine species endemic to southwest China, which is narrowly distributed in the eastern Himalaya and the Hengduan Mountains. The aim of this study is to elucidate the reproductive strategies of this heterostylous species in an alpine environment

Patterns of pollen stainability in polyploids of the genus Onosma (Boraginaceae)

Abstract: Background and aims The genus Onosma (Boraginaceae) is a taxonomically and phylogenetically very complex plant group, with several taxa of hybrid or polyploid origin. An extensive pollen viability su

Intraspecific variation in flowering phenology affects seed germinability in the forest herb Primula elatior

Abstract: Background and aims - Phenological responses to environmental cues are known to be phylogenetically conserved across species, but the adaptive nature of phenological responses to the local environment within the populations of individual species needs further exploration. In temperate forests, the canopy green up timing is expected to act selectively upon the growth and flowering phenology of understorey plants. Methods - Here we quantified the variation in the flowering phenology of a forest herb growing in the understorey of early versus late leafing tree species and explored the effect of this variation on the germinability of its seeds. The flowering of individual plants was recorded in six populations at twelve time points in early spring. Germinability was tested in a lab germination experiment. The individual plants were visited again in a second growing season to quantify the variation in phenology between years. Key results - Variability between plants was found within populations rather than between populations or forest stands. Phenology was consistent across growing seasons with individuals flowering either early or late in both studied years (which was not simply due to differences in plant size). Early flowering individuals had a fitness advantage in the sense that they produced higher proportions of germinable seeds. Conclusions - We quantified phenological variation between the individuals of an understorey plant species relative to the canopy phenology and related this variation to fitness. While some interesting patterns emerged, fitness components other than seed germinability and the plant life stages following germination should be studied as well to understand the evolutionary significance of phenology in forest understorey plants.

Specialist plant species harbour higher reproductive performances in recently restored calcareous grasslands than in reference habitats

Abstract: Background and aims Calcareous grasslands are local biodiversity hotspots in temperate regions that suffered intensive fragmentation. Ecological restoration projects took place all over Europe. Their

Effects of fragmentation and population size on the genetic diversity of Centaurea cyanus (Asteraceae) populations

Abstract: Aims Centaurea cyanus L. is a patrimonial species emblematic of the flora associated with cereal crops, but it is currently declining in Western Europe because of agricultural intensification. The de

A comparative study of leaf trait relationships in coastal dunes in southern Spain

Abstract: Background and aims–Coastal dunes of southern Spain are an original Mediterranean ecosystem, hotspot of biodiversity, insufficiently studied under the functional ecology. We explore co-variation patterns among leaf traits (size, specific leaf area (SLA), nutrient concentrations (N, P, K…), deciduousness and leaf consistence), and growth form in 78 native coastal dune species. Methods–Three coastal dunes of contrasting climatic conditions were sampled and differentiated between fixed and mobile dunes. Species were classified based on growth form, deciduousness and leaf consistence. Leaf samples were collected following Cornelissen et al. (2003) and soil samples were also analysed by ICP-OES and elemental analysis. Key results–Positive co-variation patterns of SLA and leaf [N], and of leaf [N] and leaf [P], were found in two of three sites. Fixed dunes, with a higher proportion of large shrubs, evergreens, and sclerophyllous species, had lower values of SLA and foliar nutrients, and higher values of [C] than mobile dunes. The topsoil of fixed dunes had less [Ca] than in mobile dunes and this was reflected in foliar concentrations. The Mediterranean-subdesert dunes, had a distinct pattern of trait variation. Conclusion–Mediterranean-subdesert coastal dunes are characterized by lower values of leaf [N] and higher values of leaf [Ca] and [Fe] than in other Mediterranean ecosystems and by a broad correlation among SLA, leaf [N], [P] and [K]. Mediterranean-subdesert dunes showed a predominance of xerophytic malacophyllous strategy, whereas Mediterranean -oceanic dunes are dominated by stress tolerant species. Mobile dunes showed a leaf strategy closer to the observed on Mediterranean -subdesert dunes but with a relevantly higher leaf [Ca].

Morphology, molecular phylogenetics and biogeography of Impatiens Akomensis (Balsaminaceae), a new species from cameroon

Abstract: Background and aims - A recent field expedition in the Campo-Ma’an/Akom II region in Cameroon resulted in the collection of a previously unknown Impatiens species, which resembles Impatiens macroptera and Impatiens pseudomacroptera. This study aims to describe and infer the evolutionary history of this novelty by using phylogenetics, biogeographic inference and dating estimation analyses. Methods - The new species was subject to a palynological, molecular phylogenetic and biogeographical analysis. In addition, a thorough morphological comparison with its closely related species was conducted. Key results - Morphological comparison and molecular phylogenetics corroborate its status as a new species, which is given the name Impatiens akomensis. Molecular data, based on ImpDEF1, ImpDEF2 and ITS indicate that Impatiens akomensis is most closely related to the Cameroonian I. macroptera, whereas the lineage towards I. macroptera and the novelty is sister to the Gabonese I. pseudomacroptera. Impatiens akomensis differs from I. macroptera and I. pseudomacroptera in having very strongly asymmetric white flowers, much thicker leaves, a narrowly elliptic leaf shape and a serrulate leaf margin, smaller lateral united petals (23.1-24.2 mm) and larger bracts (12-20 mm). The new species qualifies for endangered status under IUCN criteria B2 and probably B1. Conclusions - Dating analyses in combination with biogeographic inference, and ecological and environmental interpretation of the novelty and its closely related species allows us to infer the putative evolutionary history of Impatiens akomensis.

What influences pollen dispersal in the clonal distylous Menyanthes trifoliata (Menyanthaceae)

Abstract: Background and aims – Habitat fragmentation may compromise population survival and decrease the ability to face environmental changes. Small and isolated populations in particular may suffer from disrupted pollination processes. However, a species’ response to fragmentation may vary according to life history traits. Understanding how pollen dispersal is shaped by population and life history traits such as mating system and clonal growth is therefore essential for assessing species’ response to fragmentation. Methods – We investigated pollen dispersal using fluorescent dyes in nine Belgian populations in two regions of the distylous insect-pollinated clonal herb Menyanthes trifoliata. We examined whether overall and legitimate (i.e. between-morph) dye dispersal patterns differed between morphs and regions, and whether they were influenced by population traits (size, area, plant density, morph ratio, co-flowering species) and individual plant traits (number of flowers). Key Results – No evidence of dye transfer between adjacent populations (distant from 1.3 to 11.8 km) was found, suggesting no or very restricted between-population pollen flow. Within-population dye dispersal followed a decaying, usually leptokurtic, distribution, with most dye deposition at short distances (80% at less than 1.9–49.1 m), and a maximum distance of 336.6 m. Pins and thrums as recipients or donors did not differ in dye dispersal. Legitimate dye dispersal was not less successful than overall dispersal despite spatial clumping of the morphs. The distribution was similar or simply shifted to longer distances. The proportion of dyed stigmas was positively related to flowering population size and within-population heterospecific floristic richness, and to the number of flowers when considering legitimate dye deposition at distances < 32 m. Conclusions – Our study highlights the effects of the spatial distance to dye source, population size and coflowering floral resources, i.e. population traits related to attractiveness to pollinators, on pollen dispersal patterns.

Using legacy botanical literature as a source of phytogeographical data.

Abstract: Aim Paper-based publications were the main repository for phytogeographical information until the end of the 20th century. These texts are still an important reference source for phytogeography and p

First record on secondary pollen presentation in the Cucurbitaceae family

Abstract: Aim – Secondary pollen presentation in flowers has been described only in a few species across about 25 plant families. The first report of secondary pollen presentation in the Cucurbitaceae family is given here. Key result – Sechium talamancensis, endemic to high elevations in Costa Rica, presents nearly 39% of its pollen second arily on the distal ends of its petals. The remaining pollen is presented on the anthers, the primary pollen presenters. Significance – Closely related and commercially important congeners of S. talamancensis do not show secondary pollen presentation. Potential selective advantages of the phenomenon that differentiates S. talamancensis from its lower elevation congeners are discussed.

Predicting the effects of sea level rise on salt marsh plant communities: does vegetation age matter more than sea level?

Abstract: Background and aims Salt marsh plant communities will be among the first to be exposed to the predicted increase in sea level and to the associated environmental changes. The objectives of this study