Showing papers in "Plant Ecology and Evolution in 2012"

Vegetation change in response to grazing exclusion in montane grasslands, Argentina

Abstract: Fil: Loydi, Alejandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; Argentina

Analyse phytogéographique des forêts d'Afrique Centrale: le cas du massif de Ngovayang (Cameroun)

Abstract: Phytogeographical analysis of Central African forests: the Ngovayang massif (Cameroon) Background and aims – The Ngovayang massif, in southern Cameroon, is part of a group of small hills along the Atlantic coast of the Gulf of Guinea. This area is known for its floristic richness and its high level of endemism. We conducted a phytogeographical analysis of this massif and evaluated its floristic affinities with other forested sites in Central Africa. Methods – Phytogeographical analysis was based on a comparison of lists of tree species with dbh ≥ 10 cm, inventoried in 1-ha permanent plots, and established in old growth lowland forests of Central Africa. The floristic list for Ngovayang used for this analysis contained 201 species. Key results – The lowland forests of the Ngovayang massif are dominated by LeguminosaeCaesalpinioideae, followed by Olacaceae and Burseraceae, taxa characteristic of dense old-growth Atlantic moist forests. The Ngovayang flora includes a high proportion of Guineo-Congolean species (79%), particularly Lower Guinean species (30%). Phytogeographical analysis showed that forested sites of central Africa are clearly separated into continental sites and the more coastal sites of the Lower Guinean domain, including Ngovayang. Within the Lower Guinean domain, the main floristic discontinuity appears to be situated in southern Cameroon-northern Equatorial Guinea. Ngovayang and Takamanda, which are situated on opposite sides of the Cameroon volcanic line, show stronger floristic affinities with each other than either does with other Lower Guinean forest sites located to the south of the Ngovayang massif. Conclusions – Ngovayang may constitute a transition zone between Nigerian forests and those ranging from southern Cameroon to the Democratic Republic of the Congo. For tree species of the Lower Guinean domain, the climatic hinge separating boreal and austral climates appears to be a more important phytogeographic barrier than the Cameroon volcanic line or the Sanaga River.

Gynoecial anatomy and development in Cyperoideae (Cyperaceae, Poales): congenital fusion of carpels facilitates evolutionary modifications in pistil structure

Abstract: Background and aims – In Cyperaceae, the single-ovuled, usually triangular gynoecia are widely considered to have a basic number of three carpels, often reduced to two, resulting in dimerous pistils. However, laterally flattened dimerous pistils cannot be explained by any existing carpel reduction theories, because a single stigma in median position replaces the two adaxial stigmata. This paper presents a comparative study of the ontogenetic and anatomical adaptations facilitating the origin of new pistil forms in Cyperoideae, focusing on modified gynoecia. It includes a re-evaluation of Blaser’s (1941) anatomical studies in Cyperaceae. We aim to test Blaser’s hypothesis that is based on an acropetal developmental model of the floral vasculature and the general Cyperoid ontogenetic model of Vrijdaghs et al. (2009), which states that cyperoid ovaries originate from an annular primordium. Methods – SEM, dark field and phase contrast microscopy. Key Results – All cyperoid pistils studied develop according to a cyperoid floral ontogenetic pattern, in which carpel primordia are congenitally fused. In Pycreus sanguinolentus (and other species), separate procambial initiation zones were observed in both the flower receptacle and separate floral primordia, which connect (or not) at later developmental stages. Conclusions – The presence of an annular ovary primordium instead of individual carpel primordia, combined with the bidirectional development of the pistil vasculature liberate the developing gynoecium from the structural constraints proper to a typical carpellate organisation. Procambial initiation zones in the receptacular vascular plexus and in individual floral primordia constitute the basis for the formation of a flexible vascular system in cyperoid flowers. Moreover the development of the ovary and ovule are decoupled. Consequently, in Cyperoideae the acquired developmental freedom of the pistil resulted in various adaptations.

Hitch-hiking in the wild: should seeds rely on ungulates?

Abstract: Seed dispersal is a key process in determining plant populations and community dynamics. Particularly, long-distance dispersal events (> 100 m for plants, Cain et al. 2000), though rare, are crucial to maintaining the connectivity between isolated populations necessary for plant species to survive at the regional scale (Will & Tackenberg 2008). Longdistance dispersal by large herbivores also accounted for the plant migration rates during the Holocene (Pakeman 2001). Understanding long-distance dispersal mechanisms and their consequences is critical in a context of rapidly changing environments under the effects of global change (Shupp et al. 2010). Because plants are fixed, their mobility relies on vectors that may be abiotic like wind (anemochory) and water (hydrochory), or biotic (zoochory) (Ridley 1930). Wind and water disperse few species over long distances (Mouissie et al. 2005, Schmidt et al. 2004) and wind is ineffective inside forest stands (Howe & Smallwood 1982). Birds and mammals are therefore the main vectors for long-distance seed dispersal within and among forest areas. While birds seem to disperse specific plants according to their diet (endozoochory), large herbivores, compared to small-bodied rodents, might be able to disperse many plant species in their fur due to a larger surface available for hitching seeds. For example, the role of roe deer (Capreolus capreolus) and red deer (Cervus elaphus) in the expansion of Green Hound’s-tongue (Cynoglossum germanicum Jacq.) through external dispersal has recently been highlighted (Boulanger et al. 2011). Wild ungulates provide useful models for the study of long-distance plant dispersal and distributional dynamics under changing landscapes. First, roe deer, red deer and wild boar (Sus scrofa) populations have been increasing in Europe, and particularly in France, since the 1970s. The number of animals killed by hunting has increased ninefold over the last forty years, reaching over 500,000 individuals for both roe deer and wild boar and 50,000 for red deer in 2010 (Source: ‘Reseau Ongules sauvages ONCFS-FNC-FDC’). Second, due to their large home ranges and high travel speed, wild ungulates move over long distances and through

The genus Acacia (Fabaceae) in East Africa: Distribution, diversity and the protected area network

Abstract: Background and aims - Plants are often overlooked in conservation planning, yet they are the foundation of all terrestrial ecosystems. The East Africa region is used to investigate the effectiveness of protected areas for conserving plants. With a wide range of ecosystems and 771 protected areas covering nearly one quarter of the land area, East Africa is an ideal location to assess the effectiveness of protected areas through distribution modelling of the genus Acacia. Methods - Herbarium specimen data (2,047 records) were collated from East Africa for 65 taxa (species, subspecies, varieties) from the genus Acacia. Generalised Additive Models were used to determine climatic drivers, and thence to extrapolate climatic suitability across the region. For two Acacia taxa, we investigated the potential for climate-induced range-shifts using a downscaled regional climate model under two IPCC scenarios. Key results - Approximately two thirds of Acacia diversity hotspots had < 10% coverage by protected areas. Furthermore, the protected area network covered less of the predicted ranges of the Acacia taxa and contained fewer taxa per unit area than would be expected under randomised placement. Areas with suitable climate for high-elevation, moisture-dependent taxa such as A. abyssinica subsp. calophylla are predicted to contract their potential range by up to 80% towards mountain peaks, where protected areas are dominated by low-level protection forest reserves. Conversely, the area of suitable environment for a xerophytic low-elevation species (A. turnbulliana) is predicted to increase by up to 77%. Conclusions - East Africa's national parks may not be preserving an important component of ecosystem diversity, a situation exacerbated by climate change. Even within the genus Acacia, different species are predicted to respond differently to climate change. Priority areas for research and conservation are identified based on overlap between predicted high Acacia diversity and gaps in the collection record, with northern and eastern Kenya highlighted as particularly important. High elevation protected areas are also predicted to become increasingly important as climatic refugia in a warmer future. © 2012 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.

Additional evidence for recent divergence of Chinese Epimedium (Berberidaceae) derived from AFLP, chloroplast and nuclear data supplemented with characterisation of leaflet pubescence

Abstract: Background - The genus Epimedium is well known for its ornamental representatives. However, species boundaries and evolutionary relationships within the genus remain uncertain due to several difficulties. First, potentially diagnostic characters are generally not described with enough detail, hampering linkage of specimens to recognized taxa. Second, previous molecular studies failed to gain resolution, especially within the Chinese distribution area of the genus. Nevertheless, growing scientific interest in the medicinal properties of Epimedium has prompted the need for reliable identification of species. Aims and methods - This study aims at: (1) assessing genetic diversity within Epimedium, using nuclear and chloroplast DNA sequences in combination with AFLP fingerprinting, (2) delivering a detailed description for one potentially diagnostic character, pubescence of leaflets. Key results - The DNA sequences and AFLP fingerprints resulted in an unresolved polytomy for the Chinese representatives of Epimedium. Furthermore, this study provided detailed scanning electron microscope images of four clearly distinguishable types of leaflet pubescence. Conclusions - As AFLP is considered capable of detecting rare genetic differences in groups with low sequence variation, we suggest the lack of resolution in the Chinese clade to represent a hard polytomy. This is interpreted as additional evidence for the hypothesis of a recent origin for these taxa. As this implies that several recognized species are still in the process of differentiation, these difficulties in resolving evolutionary relationships are linked to difficulties in species delimitation. Furthermore, the lack of details in some species descriptions has led to the description of new taxa based on small variations. To tackle these problems, we propose a change in view on Epimedium taxonomy. In this view, broader taxonomic entities are recognized, characterized by clearly defined characters. The four types of pubescence described in this study can serve as a first step towards this new interpretation of Epimedium taxonomy.

Phytogeographical analysis and checklist of the vascular plants of Loango National Park, Gabon

Abstract: Background and aims – Floristic inventories are the primary means by which the plant diversity of an area can be understood and are important in underpinning management plans for conservation. One of the priorities set out for Loango National Park (LNP) in an IUCN assessment of Gabon's protected areas was to produce a vascular plant checklist. Therefore, the primary goal of this research was to significantly increase the number of specimens for the park and make a concentrated effort to increase knowledge of plant diversity in the area. The secondary goal of this study was to analyse the flora of LNP in terms of phytogeography and endemism. Methods – A specimen-based botanical inventory was carried out in LNP (1005 herbarium specimens collected for this study were added to 752 existing records) and vegetation observations were made. Phytogeographical analyses were also performed using two different methods and datasets for comparison. Key results – A preliminary checklist of 686 species of vascular plants of LNP is presented, making a significant contribution to our knowledge of the flora of Gabon with more than twenty new country records. Conclusions –There is a surprisingly high proportion (15%) of the overall Gabonese flora recorded from within the park in this preliminary checklist. Further inventory within the park will undoubtedly produce a much higher percentage of the flora of the whole country. This high proportion is explained in part by the combination of restricted coastal endemics, diversity of habitats, and dynamic biological and physical processes. Phytogeographical analyses reveal different floristic relationships between the forest and savanna components of the flora suggesting different origins of these two biomes in coastal Gabon. The forest species are typically Guineo-Congolian in distribution and the savanna species are Sudano- Zambezian or widespread in distribution. Together, the faunal elements and the high diversity of the flora of Loango National Park make it a globally important site for conservation

A commented checklist of woody plants in the Northern Republic of Congo

Abstract: Aim – This paper aims to provide the first exhaustive list of woody species present in the northern part of the Republic of Congo, describing the vegetation types, characterizing the ligneous forest stands and explaining the distribution range of characteristic species. Location – The 1.23 million ha of the logging concession of ‘Congolaise Industrielle des Bois’, situated in the North of the Republic of Congo (1.41°N 16.32°E), were prospected during six years. The study area is bordered by the Sangha River to the west and by the Likwala-aux-Herbes swamps to the east. Methods – The checklist, given as an electronic appendix, documents 702 woody species. Each species is annotated with the following headings when the information is known: scientific, pilot and local names, lifeform, preferential habitat, distribution, seed dispersal type, human use, abundance and foliage phenology. Field observations have been augmented with existing bibliography. Results – A total of 392 genera and 79 families are presented. Ficus is the largest genus with seventeen species. 73% of taxa are endemic to the Guineo-Congolian Region centre. The sarcochorous functional diaspore type represents 71%. Eleven percent of the species are anemochorous and are mostly emergent trees. Forty-four species newly recorded for the Republic of Congo are especially commented. Main conclusions – Terra firma forests are characterized by deciduous, light-demanding and winddispersed emergent tree species. Evergreen stands are mainly found at the confluence of the Sangha River and Likwala-aux-Herbes swamps. This forest could be regarded as equivalent to the other interfluvial forest blocks of the Major Fluvial Refuge in the Congo basin.

Diversity and conservation value of Gabon's savanna and inselberg open vegetation: An initial gap analysis

Abstract: Background and aims – Eighty per cent of Gabon's territory is covered by forest with most species inventory work focused on these areas. However, herbaceous open vegetation types are abundant in this country and can be found in savannas on the coast, in the centre and in the south, and on inselbergs. The species diversity patterns of these habitats remain largely unexplored yet are targeted for both conservation and development. Here, we evaluate the floristic diversity of savannas in Gabon, their affinities with the inselberg open vegetation, and their contribution to the national park system in Gabon, which is currently undergoing a gap analysis. We then use a case study from the Bateke Plateaux to demonstrate species rarity in a single savanna. Materials and methods – Species presence in the grassy formations of the savannas in Loango, Lope, Pongara, and Plateaux Bateke national parks and in Kum inselberg is compared using ordination and clustering based on a similarity matrix (Sorensen index). For the Bateke Plateaux savannas, the species rarity and distributions are assessed using Star ratings. Key results – The species in the open herbaceous vegetation in Gabon account for at least 11% of the total flora of the country (508 species out of 4,710). Except for the coastal savannas, all sites are highly dissimilar in floristic composition (Sorensen index 0.065–0.26) and no dominant savanna type occurs within the dataset. The inselberg site is the most dissimilar and constitutes a separate vegetation unit. Most savanna species of the Bateke Plateaux area are widely distributed, but not weedy. A few are extremely rare and are linked with moist habitats, substrate, and fire occurrence. Our results show the diversity and the conservation value of open, herbaceous habitats. Currently, the Gabonese National Park network is partly protecting the savanna and inselberg vegetation. However, several areas remain un-assessed and merit further exploration.

A taxonomic revision of the reinstated genus Leplaea and the newly recognized genus Neoguarea (Meliaceae, Sapindales): the exclusion of Guarea from Africa

Abstract: Background and aims - The taxonomy of the African representatives of the genus Guarea, among them a number of timber species, is badly understood. The group is revised. Methods - Standard herbarium taxonomy practices were used. Specimens from fifteen different herbaria were studied. Using a GIS application and geo-referenced herbarium specimens, IUCN Red List categories are assessed for each species. Key results - Morphological studies show that the group is distinct from the South-American members of Guarea and deserves generic status. This is supported by molecular data. Therefore the genus Leplaea is reinstated to accommodate five of the species formerly placed in Guarea and the new combinations are presented. Furthermore, two new species, L. adenopunctata E.J.M.Koenen & J.J.de Wilde and L. cauliflora E.J.M.Koenen & J.J.de Wilde are formally described. In addition to de Wilde's (2007) revision of Heckeldora, one more species, G. leonensis, is transferred to this genus and the new combination made. G. glomerulata is shown to be morphologically distinct and to deserve generic status as well. This is endorsed by molecular data. As a consequence, Guarea sect. Neoguarea Harms is granted generic rank to accommodate this species; the new genus is described and the new combination made. A generic key to the African Guareeae is provided, as well as a key to the species of Leplaea; botanical drawings, distribution maps and IUCN Red List categories are presented.

How do plant community ecologists consider the complementarity of observational, experimental and theoretical modelling approaches?

Abstract: Background and aims - A large variety of methods are used by ecologists for studies at plant community level. While early works were mainly descriptive, more manipulative experiments are now being undertaken because they provide a better functional understanding and a greater insight into underlying mechanisms. Mathematical models are also being increasingly used, in particular for predicting biodiversity under global change. The aim of this study is to highlight the strengths, limitations, and advantages of these three approaches, namely observational, experimental and theoretical modelling.

Growth discrepancy between filament and style facilitates autonomous self-fertilization in Hedychium yunnanense (Zingiberaceae)

Abstract: Background and aims - Reproductive success through autonomous self-fertilization is thought to be one of the main advantages in plants when effective pollinators are limited. The present study examined an autonomous self-fertilization mechanism in a perennial ginger, Hedychium yunnanense.

Synopsis of the genus Chlorophytum (Asparagaceae) in Central Africa (Democratic Republic of the Congo, Rwanda, Burundi)

Abstract: Background and aims - The genus Chlorophytum is revised for the Democratic Republic of the Congo, Rwanda and Burundi, in order to prepare the treatment of the genus for the Flore d'Afrique Centrale. Methods - Herbarium taxonomy and SE micrographs of seeds. All the material kept in BR, BRLU, BRVU, FT, K, B and KIP has been examined, supplemented with recent field observations in S Katanga. Nuclear and chloroplast DNA markers have been used to clarify the taxonomic position of some species. Key results - A total of 65 taxa (D.R.Congo: 62, Burundi: 19, Rwanda: 8) are reported for the study area, i.e. fifty species, two subspecies, twelve varieties and one form. A total of 27 taxa are new to the D.R.Congo, five to Burundi and two to Rwanda. Three taxa are endemic to the D.R.Congo. Three new varieties are described (Chlorophytum africanum var. nordalianum, C. colubrinum var. upembense, C. cameronii var. ruziziense). Twelve new combinations, 16 new synonyms and one new name (Chlorophytum sphagnicolum) are proposed. An identification key is included. SEM pictures of seeds are included for fifteen taxa and colour photographs of living plants for fourteen taxa. A brief phytogeographic outline is provided. Upper Katanga, with 47 taxa, appears as a prominent center of diversity of the genus. © 2012 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.

Natural hybridization and potential seed set of sympatric Populus nigra and Populus × canadensis along the river IJzer in Flanders (Belgium).

Abstract: Background In Europe, Populus nigra generally grows sympatric with the exotic related taxon Populus x canadensis. Natural hybridization followed by introgression and genetic swamping is often mentioned as a potential threat for the conservation of P. nigra. However, as evidence for natural hybridization with P. x canadensis is scarce, the significance of this threat is unclear. Methods After first determining the genotypic diversity within 209 trees of P. nigra collected in western Flanders (northwest Belgium), we assessed natural hybridization events between P. nigra females and P. x canadensis males with diagnostic microsatellite markers. We also studied the possible paternity of the frequently planted P. nigra cv. Italica. Furthermore, we compared the potential seed set of P. x canadensis and P. nigra by counting the number of unfertilized ovules per ovary and the number of ovaries per pistillate inflorescences. Results and conclusions Only two different multilocus microsatellite genotypes were detected within the 209 black poplar trees sampled in western Flanders. In 57 % of the seedlings from the open pollinated black poplar trees, at least one species-specific allele of P. deltoides was detected. P. nigra cv. Italica could not be excluded as a father of one seedling. The potential for seed set and the number of ovules per ovary was significantly higher for P. x canadensis compared to P. nigra. Conclusions The extreme low number of P. nigra genotypes in western Flanders suggests a strong human influence on the species’ genetic diversity. The findings further indicate that natural hybridization events between female P. nigra and male P. x canadensis frequently occur in our study area. Furthermore, P. x canadensis has a higher seed set potential compared to P. nigra. Restoration projects of P. nigra in the valley of the IJzer river should initially aim reforestation measures with a mixture of different black poplar genotypes from neighbouring regions.

Pollination ecology and its implication for conservation of an endangered perennial herb native to the East-Himalaya, Megacodon stylophorus (Gentianaceae)

Abstract: Background and aims - Megacodon stylophorus (C.B.Clarke) Harry Sm. is an endangered herb native to the East-Himalaya and the Hengduan Mountains, south-west China. We studied reproductive ecology of this species to explore the factors that are critical for its survival and conservation.

Studies in Perenniporia (Basidiomycota). African taxa VI. A new species and a new record of Perenniporia from the Ethiopian Afromontane forests

Abstract: Background and aims - This study is a part of an ongoing survey of the genus Perenniporia (Basidiomycota, Polyporales) in sub-Saharan Africa, and reports on several species collected in Central and Southwestern Ethiopia. Methods - Species are described using morphology-based methods. Key Results -Perenniporia abyssinica is proposed as new species. Perenniporia globispora is reported for the first time in Ethiopia. Conclusion - Perenniporia abyssinica and P. globispora are reported from Central and Southwestern Ethiopia. The report of P. globispora constitutes the second report of the species and the first record for Ethiopia. © 2012 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.