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Stefan Porembski - One of the best experts on this subject based on the ideXlab platform.
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Islands on Islands: Habitats on Inselbergs
Inselbergs, 2020Co-Authors: Stefan Porembski, U. Becker, R. SeineAbstract:When seen from a distance, Inselbergs seem to form homogeneous landscape features which mainly consist of large expanses of bare, dark colored rock (Fig. 4.1). However, a closer look reveals that they have to be considered as an ecosystem which comprises an unexpected amount of clearly distinguished vegetational habitat types representing “islands on islands” (Ornduff 1987). In the 19th century, the unusual appearance of Inselbergs attracted the attention of famous naturalists, who provided the first descriptive accounts of their vegetation. Carl Friedrich Philipp von Martius (1842) and Alexander von Humboldt (1819) were amongst them. The latter discussed in detail the dark color of rocks in the Orinoco riverbed and of Inselbergs in the same area. Humboldt assumed that the black color of the rocks was due to a sheath of manganese oxide and carbon. Today, however, we know that the occurrence of epi- and endolithic cyanobacteria is responsible for the dark coloration of these rocks. Among the first floristic studies concentrating on tropical Inselbergs, one has to mention the work of Willis (1906) concerning vascular plants on Ceylonese rock outcrops. For a remarkably long period, the vegetation of Inselbergs was simply denoted as lithophytic without any further differentiation, or it was described as “savanes-roche” due to a certain amount of physiognomic similarity with savanna vegetation (de Granville 1978).
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The extraordinary botanical diversity of Inselbergs in Madagascar
Candollea, 2019Co-Authors: Marina Rabarimanarivo, Brigitte Ramandimbisoa, Nivo Rakotoarivelo, Peter B. Phillipson, Sylvie Andriambololonera, Martin W. Callmander, Stefan PorembskiAbstract:Rabarimanarivo, M.N., B. Ramandimbisoa, N.H. Rakotoarivelo, P.B. Phillipson, S. Andriambololonera, M.W. Callmander & S. Porembski (2019). The extraordinary botanical diversity of Inselbergs in Madagascar. Candollea 74: 65–83. In English, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2019v741a8Inselbergs are isolated mountains, mainly granitic or gneissic rock outcrops rising abruptly above surrounding plains. Malagasy Inselbergs are often dome-shaped and occur in varying degrees of isolation, but they sometimes form Inselberg landscapes, which comprise dozens of individual outcrops. Despite being typical landscape features on Madagascar's high plateau, little data are available on their detailed plant cover. Recent extensive fieldwork, which was conducted between 2010 and 2014, mainly on the central plateau, has resulted in a better knowledge about the floristic composition and habitats of Malagasy Inselbergs. The most speciose vascular plant genera were Cynorkis Thouars (18), Cyperus L. (15) and Euphorbia L. (14). Malagasy Inselbergs are centres of diversity for succulents (notably species of the genera Aloe L., Euphorbia and Kalanchoe Adans.), carnivorous plants (species of Drosera L. and Utricularia L.) and resurrection plants (notably species of Xerophyta Juss.). The most speciose habitat types were ephemeral flush vegetation and monocotyledonous mats. The latter habitat supports a large number of succulents and resurrection plants. In total 724 taxa out of 338 genera and 107 families have been recorded. Moreover, the variability in floristic composition between different regions is remarkable. Detrimental human impacts include quarrying, grazing, fire and the collection of plants for ornamental purposes (species of Pachypodium Lindl. and Orchidaceae) and as medicine (species of Aloe, Drosera madagascariensis DC., Myrothamnus moschatus (Baill.) Baill.). For the first time, recommendations are made for the conservation of Malagasy Inselbergs.
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rocks and leaves can anatomical leaf traits reflect environmental heterogeneity in Inselberg vegetation
Flora, 2019Co-Authors: Luiza F. A. De Paula, Stefan Porembski, Rosana Marta Kolb, Fernando A O Silveira, Davi Rodrigo RossattoAbstract:Abstract Inselbergs, isolated rock outcrops that rise above the surrounding landscape, harbor a highly diverse flora. Differences in slope, water availability, soil depth and sun exposure result in the creation of microhabitats characterized by distinct resource availability, where unique plant communities are found. However, there is a lack of studies examining specific traits structuring communities in each microhabitat. We investigated the leaf anatomical structure of Brazilian Inselberg species by comparing leaf anatomical traits of plants occurring in two microhabitats with contrasting resource availability: monocot mats (MM; extremely stressful) and shallow depressions (SD; less stressful). We hypothesized that species in the contrasting microhabitats would show different arrays of leaf anatomical traits. Seventeen quantitative and qualitative anatomical traits that have functional significance were analyzed. Firstly, we qualitatively evaluated leaf structural features, and then measured and compared tissues between plants in SD and in MM, using ANOVA and ordination analyses. An ANOSIM was also run to look for differences between the two groups. Our results show that most of the species growing in MM showed more conservative traits related to water retention and drought resistance, whereas species growing in SD showed more diversified resource strategies. These findings reinforce the heterogeneous aspect of Inselberg vegetation in Brazil, which is under variable degree of environmental stress.
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Transferability of microsatellite loci to Vellozia plicata (Velloziaceae), a widespread species on Brazilian Inselbergs
Brazilian Journal of Botany, 2017Co-Authors: Luiza F. A. De Paula, Stefan Porembski, Bárbara Simões Santos Leal, Juliane Rexroth, Clarisse Palma-silvaAbstract:Inselbergs are isolated, mainly granitic and gneissic rock outcrops, forming old landscape elements on crystalline continental shields on all continents. Many Velloziaceae which occur specifically as mat-formers on these rock outcrops are well adapted to harsh environmental conditions and do not occur in the surrounding matrix. Vellozia plicata Mart. is a widespread desiccation-tolerant mat-forming species on Inselbergs in southeastern Brazil, with naturally fragmented populations. Here, we tested the transferability of 53 microsatellite loci previously developed for two Vellozia species (V. gigantea N. L. Menezes & Mello-Silva and V. squamata Pohl) in two populations of V. plicata. We succeeded in the amplification of 11 loci, and six of them were polymorphic. The number of alleles per locus ranged from 2 to 17, the expected and observed heterozygosities ranged from 0.000 to 0.875 and from 0.000 to 0.895, respectively. Our results show that cross-amplification works within the genus Vellozia, but at a lower level when compared to other monocot families on Inselbergs, such as Bromeliaceae and Orchidaceae. This work might help in further studies on population genetics of V. plicata, in order to guide conservation actions in the future and also to promote further investigations about speciation processes of Inselberg specialists.
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Sugar Loaf Land in south‐eastern Brazil: a centre of diversity for mat‐forming bromeliads on Inselbergs
Botanical Journal of the Linnean Society, 2016Co-Authors: Luiza F. A. De Paula, Rafaela Campostrini Forzza, Andreza Viana Neri, Marcelo Leandro Bueno, Stefan PorembskiAbstract:Inselbergs sensu lato are isolated, mainly granitic and gneissic, rock outcrops, forming old landscape elements on crystalline continental shields on all continents. Mats consisting mainly of monocots occur on open rocky slopes, forming a conspicuous habitat on these outcrops. Brazilian lowland Inselbergs consist of species-rich mats with large numbers of endemics and Bromeliaceae standing out as characteristic elements in these communities. For the first time, we provide a checklist of mat-forming bromeliads on lowland Inselbergs in Brazil and investigate whether the regional species pool influences the species diversity of Inselberg mats. Furthermore, through modelling analysis, we looked for the potential distribution of bromeliads endemic to Inselbergs, expecting that they would show a narrower niche width than non-endemic species. Our data indicate the existence of a particular phytogeographical region in the Atlantic Forest in south-eastern Brazil, comprising Inselbergs harbouring a highly diverse flora of Bromeliaceae, which we call Sugar Loaf Land. In addition, our projections reveal smaller predicted areas for bromeliads endemic to Inselbergs compared with non-endemic species, the former apparently being mainly controlled by climatic factors. In addition to climate and regional species pools, the island-like character of Inselbergs seems to play an important role in the speciation of rupicolous Bromeliaceae.
Wilhelm Barthlott - One of the best experts on this subject based on the ideXlab platform.
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A neglected habitat of carnivorous plants: Inselbergs
Feddes Repertorium, 2008Co-Authors: R. Seine, Stefan Porembski, Wilhelm BarthlottAbstract:On the basis of extensive fieldwork, a first survey of carnivorous plants occurring on Inselbergs is provided. Inselbergs are mostly dome-shaped granitic or gneissic outcrops with scarce vegetation cover. They are important habitats for carnivorous plants in wooded tropical areas. Three families of carnivorous plants (Droseraceae, Lentibulariaceae, Nepenthaceae), including four genera and 45 species are reported from various Inselberg habitats. Carnivorous plant families and genera are represented on Inselbergs proportionally to their importance in the regional species pool. Basierend auf intensiven Feldstudien wird erstmals eine zusammenfassende Darstellung der auf Inselbergen auftretenden Karnivore gegeben. Inselberge sind meist domformige, abrupt aus der Ebene aufsteigende Felserhebungen aus Graniten oder Gneisen. In bewaldeten Tropenregionen stellen sie einen wichtigen Lebensraum fur Karnivore dar. Drei Familien (Droseraceae, Lentibulariaceae, Nepenthaceae) mit vier Gattungen und 45 Arten besiedeln Inselberge. Auf Inselbergen sind die Gattungen carnivorer Pflanzen entsprechend ihres Artenanteils an der regionalen Flora reprasentiert.
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Granitic and gneissic outcrops (Inselbergs) as centers of diversity for desiccation-tolerant vascular plants
Plant Ecology, 2000Co-Authors: Stefan Porembski, Wilhelm BarthlottAbstract:Although desiccation tolerance is common in non-vascular plants, this adaptive trait is very rare in vascular plants. Desiccation-tolerant vascular plants occur particularly on rock outcrops in the tropics and to a lesser extent in temperate zones. They are found from sea level up to 2800 m. The diversity of desiccation-tolerant species as measured by number of species is highest in East Africa, Madagascar and Brazil, where granitic and gneissic outcrops, or Inselbergs, are their main habitat. Inselbergs frequently occur as isolated monoliths characterized by extreme environmental conditions (i.e., edaphic dryness, high degrees of insolation). On tropical Inselbergs, desiccation-tolerant monocotyledons (i.e., Cyperaceae and Velloziaceae) dominate in mat-like communities which cover even steep slopes. Mat-forming desiccation-tolerant species may attain considerable age (hundreds of years) and size (several m in height, for pseudostemmed species). Both homoiochlorophyllous and poikilochlorophyllous species occur. In their natural habitats, both groups survive dry periods of several months and regain their photosynthetic activity within a few days after rainfall. Other desiccation-tolerant species colonize shallow depressions, crevices and even temporarily water-filled rock pools on Inselbergs. Desiccation-tolerant vascular plants occur in 13 families and are best represented within the monocotyledons and ferns. Only a few desiccation-tolerant dicots exist, in the Gesneriaceae, Myrothamnaceae and Scrophulariaceae. In total, about 330 species of vascular desiccation-tolerant plants are known, of which nearly 90% occur on Inselbergs. With regard to morphological adaptations, the mat-forming monocotyledons are particularly remarkable due to the possession of roots with a velamen radicum, which is reported here in the genus Borya for the first time.
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Vegetation of seasonal rock pools on Inselbergs situated in the savanna zone of the Ivory Coast (West Africa)
Flora, 2000Co-Authors: Axel Krieger, Stefan Porembski, Wilhelm BarthlottAbstract:Summary Inselbergs are monolithic, old and stable landscape elements with a worldwide distribution. On Inselbergs a range of habitats can be distinguished physiognomically. The relatively old (i.e. hundreds of years old) rock pools form a unique habitat. They occur as seasonally water-filled depressions with a thin layer of soil mainly inhabited by ephemerals and cryptogams. Even during the rainy season they often fall dry if precipitation lacks for a few days. A detailed floristic description of the vegetation of rock pools located on Inselbergs in the Ivorian savanna zone is given. Two types of rock pools can be distinguished: irregular shaped natural pools and the relatively homogenous grinding holes. Mean size was 0.9m 2 . In total, 34 plant species belonging to 15 families were recorded, with Cyperaceae and Poaceae accounting for the greatest proportion of species. The number of species is low in comparison to other communities on Inselbergs. Ecological affinities exist with marshy sites and other habitats on Inselbergs. Therophytes are the predominant life-form and r-strategists comprise about three-quarters of the species found. Entomophily overrules anemophily while anemochory is the dominant dispersal syndrome. Unlike in other geographical regions (e.g. SE Africa) only a few specialists occur in seasonal rock pools. Low frequencies of the species indicate that seasonal rock pools form no favourable microsites for most of the species found.
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Vegetation of Inselbergs in Zimbabwe
Edinburgh Journal of Botany, 1998Co-Authors: R. Seine, Stefan Porembski, U. Becker, G. Follmann, Wilhelm BarthlottAbstract:Inselbergs are rounded rock outcrops, usually of Precambrian age, with sparse vegetation cover. The vegetation of Inselbergs in Zimbabwe is described for the first time, based upon data sampled from 53 localities. Inselbergs support a range of habitats whose vegetation is described. Data on species richness and floristic composition of the Inselberg flora (549 vascular plant, 25 bryophyte and 136 lichen species) are presented. Phytogeography and diversity of Inselberg vegetation are discussed. First records for Zimbabwe are reported in lichens and vascular plants.
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Diversity and ecology of saxicolous vegetation mats on Inselbergs in the Brazilian Atlantic rainforest
Diversity and Distributions, 1998Co-Authors: Stefan Porembski, Gustavo Martinelli, Ralf Ohlemuller, Wilhelm BarthlottAbstract:Inselbergs occur as mostly dome-shaped rock outcrops in all climatic and vegetational zones of the tropics. Consisting of Precambrian granites and gneisses, they form ancient and stable landscape elements. Due to harsh edaphic and microclimatic conditions, the vegetation of Inselbergs differs markedly from those of the surroundings. Monocotyledonous mats form one of the most characteristic communities of this ecosystem. The floristic composition of this community was studied on six Inselbergs located in the Brazilian Atlantic rainforest. Dominating are Bromeliaceae (Alcantarea, Encholirium), Velloziaceae (Vellozia), Cactaceae (Coleocephalocereus) and the Cyperaceae Trilepis. The alpha diversity of the mats was relatively uniform among the six outcrops. However, beta diversity varied considerably between the different sites. Beta diversity was highest at the most speciose locality indicating a high degree of stochasticity in colonization. In contrast to the low diversity mats on West African Inselbergs, the Brazilian rock outcrops bear a floristically more diverse mat community rich in endemics. Thus the edaphically controlled Inselberg vegetation reflects the outstanding diversity of the Mata Atlantica. Possibly the high species richness of mats on East Brazilian Inselbergs is a consequence of a large species-pool. The processes that regulate regional and local diversity in the Mata Atlantica are not fully clear. It is assumed that historical (i.e. long-term stability) and biotic (i.e. evolutionary interchange of taxa between canopies and rock outcrops followed by differentiation of local populations) conditions have promoted high rates of speciation and their coexistence in isolated habitats. A danger to the unique vegetation of East Brazilian Inselbergs is the establishment of invasive weeds.
Jeanfrancois Ponge - One of the best experts on this subject based on the ideXlab platform.
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from Inselberg to Inselberg floristic patterns across scales in french guiana south america
Flora, 2017Co-Authors: Corinne Sarthou, Sandrine Pavoine, Jeanpierre Gasc, Jeanchristophe De Massary, Jeanfrancois PongeAbstract:Granitic outcrop vegetation was compared in 22 Inselbergs of French Guiana, South America, using RLQ and fourth-corner analyses to identify the main relationships between environmental gradients and plant traits. At the scale of the whole territory the distribution of species and species traits was mostly driven by a spatially-structured gradient embracing regional climate (annual rainfall), forest matrix (canopy openness), and Inselberg features (altitude, shape, habitats, summit forest, degree of epiphytism, fire events). Biogeographic, environmental and past historical factors contribute to explain the variation observed at coarse scale and two groups of Inselbergs are identified. A first group occupies the southern peneplain in a semi-open forest matrix and exhibits a higher representation of suffrutescent species and climbers, a lower representation of upright shrubs, a lower degree of Guiana Shield endemism, and a higher incidence of human use and autochory. All these features suggest an adaptation to more disturbed environments linked to past climate changes and savannization and to human influences. A second group, characterized by opposite plant traits, occupies the northern part of French Guiana and the far south within a closed forest matrix. Within archipelagos (Inselbergs at less than 7 km distance), C-score and Mantel tests revealed a random co-occurrence of plant species and an increase of floristic dissimilarity with distance without any concomitant change in plant traits, respectively, suggesting that spatially-structured stochastic factors (limitation by dispersal) were the driving force of vegetation change at fine scale.
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a 10 year decrease in plant species richness on a neotropical Inselberg detrimental effects of global warming
Global Change Biology, 2009Co-Authors: Emile Fonty, Denis Larpin, Corinne Sarthou, Jeanfrancois PongeAbstract:The census of vascular plants across a 10-year interval (1995-2005) at the fringe of a neotropical rainforest (Nouragues Inselberg, French Guiana, South America) revealed that species richness decreased, both at quadrat scale (2m 2 ) and at the scale of the Inselberg (three transects, embracing the whole variation in community composition). Juvenile stages of all tree and shrub species were most severely affected, without any discrimination between life and growth forms, fruit and dispersion types, or seed sizes. Species turnover in time resulted in a net loss of biodiversity, which was inversely related to species occurrence. The most probable cause of the observed species disappearance is global warming, which severely affected northern South America during the last 50 years ( + 2°C), with a concomitant increase in the occurrence of aridity.
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successional patterns on tropical Inselbergs a case study on the nouragues Inselberg french guiana
Flora, 2009Co-Authors: Corinne Sarthou, Charlotte Koundakiki, Anne Vaculik, Philippe Mora, Jeanfrancois PongeAbstract:A number of plant communities have been described on tropical Inselbergs, known as hot spots of plant and animal biodiversity. However, few studies tried to question what drives seral processes in these harsh environments, submitted to natural hazards (violent storms, intense runoff and lightning strikes) which may destroy the vegetation cover and its accumulated organic matter. We analysed quantitative data from the granitic Nouragues Inselberg (French Guiana) in order to discern how successional processes featured their variety. We showed that the transition from herbaceous carpets (bromeliaceous mats and grassy meadows) to woody vegetation (shrub thickets) was not conditioned by slope, but was truly successional. We also showed that there was a cycle of change in shrub thickets, reinitiated by the destruction of scrub vegetation by fire (lightnings), wood-destroying fungi and termites.
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Soil invertebrate activity in biological crusts on tropical Inselbergs
European Journal of Soil Science, 2004Co-Authors: Anne Vaculik, Corinne Sarthou, Charlotte Kounda-kiki, Jeanfrancois PongeAbstract:Summary Granite Inselbergs protrude from forest and savanna in the tropics. They are exposed to harsh climates (alternation of heavy rain and severe drought) and provide little nutrient for plants. Soil animals and humus components were investigated in cyanobacterial crusts close to patches of epilithic vegetation on the surface of the Nouragues Inselberg (French Guiana). Three biological crust samples, corresponding to bromeliacean carpets of increasing size (supposed of increasing age), were sampled for faunal and micromorphological studies. Arthropods (mainly mites and insects) were abundant and highly diversified, the more so after enchytraeid worms ate and transformed the cyanobacterialmass. Bel ow the superficial cyanobacterial crust, humus was made of a loose assemblage of enchytraeid faeces where these animals were present, or of a compact assemblage of cyanobacteria and amorphous organic matter where mites were the dominant animalgroup. Roots abounded in the humified part of the crust. We concl ude that soil invertebrates, in particular enchytraeid worms, are important for the accumulation of organic matter on granite outcrops, and so therefore for the encroachment of plant succession.
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soil arthropods in a developmental succession on the nouragues Inselberg french guiana
Biology and Fertility of Soils, 2004Co-Authors: Charlotte Koundakiki, Jeanfrancois Ponge, Anne Vaculik, Corinne SarthouAbstract:Tropical Inselbergs are isolated rock outcrops with a special type of vegetation surrounded by rain forest. They are exposed to a harsh climate (alternation of heavy rain and severe drought) and provide few nutrients for plant growth. The aim of our study was to investigate a possible correlation between primary plant succession, size and diversity of soil arthropods. The study site was the Nouragues Inselberg, in French Guiana (South America). Nine soil samples (three samples in each vegetation type) were taken for the study of soil arthropod communities and their food habits in three habitat types: Pitcairnia geyskesi (Bromeliaceae), Clusia minor (Clusiaceae) and Myrcia saxatilis (Myrtaceae), which represent three stages in a primary plant succession on this Inselberg. Soil arthropods were classified into morphospecies under the dissecting microscope and their food habits were characterized by examining their gut contents under the light microscope. A variation in food habits was observed, cyanobacteria being found in arthropod guts only during the Pitcairnia stage, and were replaced by plant material at the Myrcia stage. Carnivory was prominent in oribatid mites, contrary to temperate records. All our samples contained large numbers of microarthropods, principally mites and collembolans. At the Myrcia stage arthropod density was significantly higher than at the two other stages. Macroinvertebrates are present only at late and intermediate successional stages. The number of macropredators increased by a factor of 10 in species richness and 100 in abundance along the succession. These results suggest that abundance and diversity of soil arthropods increased throughout the plant succession and show the importance of organic matter as a factor which can explain the observed phenomenon.
Antje Burke - One of the best experts on this subject based on the ideXlab platform.
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Succulent plants on arid Inselbergs
Flora, 2013Co-Authors: Antje BurkeAbstract:Abstract Succulent plants in arid areas are believed to be often associated with high altitudes, except where they form the dominant, zonal vegetation such as in the Succulent Karoo Biome of southern Africa. To test this hypothesis the contribution of perennial succulents to Inselberg floras was investigated on twenty-two isolated mountains (Inselbergs) at four study sites (Etendeka–Barab: 19°34′ S/13°42′ E; Spitzkoppe: 21°49′ S/15°09′ E; Namibrand: 25°17′ S/15°47′ E; and Sperrgebiet: 27°43′ S/16°04′ E) along a nearly 1000 km bioclimatic gradient in the Namib Desert and adjacent areas, from the Succulent Karoo in the south to the northern Namib, and along altitude gradients. The contribution of succulents to the flora clearly increased with altitude at the two central study sites, thus showing a hump-shaped trend along the bioclimatic gradient. No such correlation was found at the northern and southern end of the bioclimatic gradient. The surrounding (rocky) lowlands likely resulted in a more even distribution of succulents throughout the landscape in the north, while the position in the heartland of the succulent flora in southern Africa at the southern-most site, levelled out potential patterns related to altitude. Nevertheless, even here, a fair number of succulents restricted to mountain habitats occur. This is the case in all other study sites, where succulents restricted to mountain habitats are always present. Some perennial succulents, such as Aridaria noctiflora , Euphorbia gummifera and Tetragonia reduplicata indicate an upward movement with increasing distance from the Succulent Karoo, by growing on plains and lowlands in the Succulent Karoo, but only on Inselbergs at study sites north of the Succulent Karoo. Many of the mountain specialist succulents are sought after by plant collectors, such as species of Conophytum , Crassula and Lithops . Protecting and monitoring vulnerable populations as well as growing these in horticulture may help to alleviate the pressure on some of these rare species in nature. Preserving genetic material of isolated populations from mountain tops ex situ is another important conservation measure, and particularly important in the view of anticipated climatic change.
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From plains to Inselbergs: species in special habitats as indicators for climate change?
Journal of Biogeography, 2004Co-Authors: Antje BurkeAbstract:Aim This study proposes a process to select plant species that would provide suitable candidates for monitoring climate change impacts in areas where complete biological inventories are lacking. Location Inselberg floras of nine Inselberg landscapes (i.e. isolated mountains) in the arid Desert and Nama Karoo biome in Namibia were analysed to develop a selection process. Methods Data from detailed field surveys were summarized to determine species only occurring on Inselberg habitats (i.e. Inselberg specialists). Detrended correspondence analysis and a step-by-step selection process based on species distribution patterns were used to determine species occurring on Inselbergs beyond their zonal distribution ranges. Results The systematic selection process initially identified 88 plant species. Based on field observations and published sources eliminating species (1) with a wide distribution elsewhere, (2) distribution influenced by local effects and (3) for which their status of knowledge of distribution was clearly inadequate, this list was further reduced to 25 species. This included southern species occurring on Inselbergs likely beyond their zonal distribution, such as Adenolobus garipensis, Aloe dichotoma and Euphorbia gummifera, as well as savanna and escarpment species at their western zonal distribution edge (e.g. Cordia sinensis, Commiphora glaucescens and Moringa ovalifolia). Main conclusions The step-by-step selection process proposed in this study to assist with the selection of indicators for climate change provides an objective tool in areas where biodiversity coverage is not adequate and little is known about physiology, growth and reproductive patterns of individual species. As such it introduces a method for preliminary screening of species, but will require further input based on field observations and expert knowledge.
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Inselbergs in a changing world: global trends
Diversity and Distributions, 2003Co-Authors: Antje BurkeAbstract:. Based on a review of recent literature, this paper puts forward hypotheses for global trends of Inselbergs (isolated mountains) with regard to: (a) their bioclimatic position in relation to the surroundings; (b) their potential for providing habitat niches; and (c) human impacts that may influence ecological processes. This review takes a landscape-level perspective and highlights the challenges ahead in view of changing environmental conditions. Recognizing that Inselbergs per se are composed of different microhabitats relative to their surroundings, Inselbergs are hypothesized to be bioclimatic ‘islands’ of xeric conditions in a humid matrix in tropical and temperate regions, and ‘islands’ of mesic conditions in arid regions. The bioclimatic status of intermediate positions along this global axis (e.g. semiarid and subtropical savanna regions) is less clear. Here, other environmental variables may be of greater importance (microhabitat composition, size of Inselberg, distance to other mountain habitats and biogeographical influences). Whether or not biotic communities match these hypothesized physical and bioclimatic trends warrants investigation and could contribute to explaining global species diversity patterns. Invasion of alien species in tropical and Mediterranean-climate regions, and altered fire regimes and resource use pose threats to Inselberg communities. Their role as sources of native species to recolonize disturbed surroundings is important in degraded semiarid and arid regions. A generalized model is proposed hypothesizing possible processes between Inselberg habitats and disturbed areas in their surroundings in different climatic regions. This model may help to direct further research towards substantiating these perceived trends.
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The role of Namibian Inselbergs in contributing to local and regional plant species richness
Biodiversity and Conservation, 2003Co-Authors: Antje BurkeAbstract:This study investigated four Inselberg landscapes in Namibia's aridNama Karoo. Inselbergs of different size and geology were investigated (a) todetermine environmental variables influencing the number of Inselberg restrictedplant species and (b) to investigate seed dispersal spectra as one parameterdescribing functional properties of Inselberg specialists. With regard to therole of Inselbergs in contributing to local and regional species richness, manyspecies restricted to Inselberg habitats occurred (up to 79 species recorded inthis survey) and so contribute to local and regional species richness. As nospecies endemic to an Inselberg were recorded in this study, Inselbergspecialists may provide an indicator for conservation value of these mountains.Elevation rather than surface area provided a measure for predicting the numberof Inselberg specialists. Besides elevation, underlying geology, and resultinglandforms and edaphic conditions, as well as distance to potential mainland alsoinfluenced the number of Inselberg specialists. Functional relationships betweenInselbergs based on seed dispersal spectra of Inselberg specialists were notconclusive.
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Are Namibian Inselbergs conservation islands? A floral perspective : research in action
South African Journal of Science, 2002Co-Authors: Antje BurkeAbstract:Plant communities and plant species diversity of four Namibian Inselberg landscapes were investigated across the Nama Karoo biome to elucidate biogeographical patterns, the role of Inselbergs as refugia of plant species, and environmental variables determining local and regional species patterns in Inselberg landscapes. The Inselbergs investigated are conservation islands with a high 're-colonization potential' and biodiversity value and contribute to regional and landscape-level species pools. Linkages between Inselbergs and their surroundings existed in the form of gene flow and nutrient flow from Inselbergs to lowlands. Exchange of species with similar habitats in the surrounding areas was important in the formation and maintenance of distinct Inselberg plant communities. Stable communities with longer-lived species grew on granite Inselbergs, whereas dolerite Inselbergs supported transient communities comprised of short-lived species. At a regional level, climatic parameters influenced Inselberg- matrix relationships. Floristic relationships between Inselbergs were largely determined by geographical position and geology. Landscape-level variables were more important in governing functional relationships, and highlighted the importance of altitude as an environmental variable. There was also a link between the overall species pool and that of Inselberg specialists. Linkages with potential mainland habitats differed depending on lithology and landform. Granite Inselbergs showed closer links to potential mainland habitats than dolerite Inselbergs. The conservation of groups of Inselbergs rather than isolated mountains may be critical where Inselbergs are a long way from potential mainland sources. Linkage corridors or 'stepping stones' from Inselbergs to potential mainland sources are important, particularly for the conservation of taxa with short dispersal ranges.
Corinne Sarthou - One of the best experts on this subject based on the ideXlab platform.
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from Inselberg to Inselberg floristic patterns across scales in french guiana south america
Flora, 2017Co-Authors: Corinne Sarthou, Sandrine Pavoine, Jeanpierre Gasc, Jeanchristophe De Massary, Jeanfrancois PongeAbstract:Granitic outcrop vegetation was compared in 22 Inselbergs of French Guiana, South America, using RLQ and fourth-corner analyses to identify the main relationships between environmental gradients and plant traits. At the scale of the whole territory the distribution of species and species traits was mostly driven by a spatially-structured gradient embracing regional climate (annual rainfall), forest matrix (canopy openness), and Inselberg features (altitude, shape, habitats, summit forest, degree of epiphytism, fire events). Biogeographic, environmental and past historical factors contribute to explain the variation observed at coarse scale and two groups of Inselbergs are identified. A first group occupies the southern peneplain in a semi-open forest matrix and exhibits a higher representation of suffrutescent species and climbers, a lower representation of upright shrubs, a lower degree of Guiana Shield endemism, and a higher incidence of human use and autochory. All these features suggest an adaptation to more disturbed environments linked to past climate changes and savannization and to human influences. A second group, characterized by opposite plant traits, occupies the northern part of French Guiana and the far south within a closed forest matrix. Within archipelagos (Inselbergs at less than 7 km distance), C-score and Mantel tests revealed a random co-occurrence of plant species and an increase of floristic dissimilarity with distance without any concomitant change in plant traits, respectively, suggesting that spatially-structured stochastic factors (limitation by dispersal) were the driving force of vegetation change at fine scale.
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Genetic structure of the xerophilous bromeliad Pitcairnia geyskesii on Inselbergs in French Guiana – a test of the forest refuge hypothesis
Ecography, 2010Co-Authors: Marie‐catherine Boisselier‐dubayle, Sarah Samadi, Raphaël Leblois, Josie Lambourdière, Corinne SarthouAbstract:Inselbergs are isolated granitic rock outcrops that provide distinctive ecological conditions. In northern South America they rise above the surrounding rainforest. Among Inselberg specialists, Pitcairnia geyskesii (Bromeliaceae) is restricted to these habitats in French Guiana. We studied populations from 12 Inselbergs using 7 microsatellite loci to give a "reverse image" of the reduction-expansion of the rainforest in the context of the refuge hypothesis. Our analyses showed that populations are fragmented with dispersal occurring only over very short distances. Genetic diversity was higher in northern French Guiana, whereas specific alleles were observed in the south. The results point to the occurrence of a dry corridor in the north, as hypothesized by Tardy (1998) based on charcoal analyses, whereas de Granville's (1982) hypothesis of a unique past refuge is not confirmed. Moreover, our data suggests the importance of Oyapock River as a pathway for range expansion, arguing against the potential role of the Inini-Camopi Mountains as a physical barrier. Finally, in spite of a strongly argued scenario in favour of a north-to-south migration history, a clear genetic isolation of P. geyskesii populations living on Inselbergs of the Mitaraka archipelago suggests a distinct ancestry of the most southern populations.
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a 10 year decrease in plant species richness on a neotropical Inselberg detrimental effects of global warming
Global Change Biology, 2009Co-Authors: Emile Fonty, Denis Larpin, Corinne Sarthou, Jeanfrancois PongeAbstract:The census of vascular plants across a 10-year interval (1995-2005) at the fringe of a neotropical rainforest (Nouragues Inselberg, French Guiana, South America) revealed that species richness decreased, both at quadrat scale (2m 2 ) and at the scale of the Inselberg (three transects, embracing the whole variation in community composition). Juvenile stages of all tree and shrub species were most severely affected, without any discrimination between life and growth forms, fruit and dispersion types, or seed sizes. Species turnover in time resulted in a net loss of biodiversity, which was inversely related to species occurrence. The most probable cause of the observed species disappearance is global warming, which severely affected northern South America during the last 50 years ( + 2°C), with a concomitant increase in the occurrence of aridity.
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successional patterns on tropical Inselbergs a case study on the nouragues Inselberg french guiana
Flora, 2009Co-Authors: Corinne Sarthou, Charlotte Koundakiki, Anne Vaculik, Philippe Mora, Jeanfrancois PongeAbstract:A number of plant communities have been described on tropical Inselbergs, known as hot spots of plant and animal biodiversity. However, few studies tried to question what drives seral processes in these harsh environments, submitted to natural hazards (violent storms, intense runoff and lightning strikes) which may destroy the vegetation cover and its accumulated organic matter. We analysed quantitative data from the granitic Nouragues Inselberg (French Guiana) in order to discern how successional processes featured their variety. We showed that the transition from herbaceous carpets (bromeliaceous mats and grassy meadows) to woody vegetation (shrub thickets) was not conditioned by slope, but was truly successional. We also showed that there was a cycle of change in shrub thickets, reinitiated by the destruction of scrub vegetation by fire (lightnings), wood-destroying fungi and termites.
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Soil invertebrate activity in biological crusts on tropical Inselbergs
European Journal of Soil Science, 2004Co-Authors: Anne Vaculik, Corinne Sarthou, Charlotte Kounda-kiki, Jeanfrancois PongeAbstract:Summary Granite Inselbergs protrude from forest and savanna in the tropics. They are exposed to harsh climates (alternation of heavy rain and severe drought) and provide little nutrient for plants. Soil animals and humus components were investigated in cyanobacterial crusts close to patches of epilithic vegetation on the surface of the Nouragues Inselberg (French Guiana). Three biological crust samples, corresponding to bromeliacean carpets of increasing size (supposed of increasing age), were sampled for faunal and micromorphological studies. Arthropods (mainly mites and insects) were abundant and highly diversified, the more so after enchytraeid worms ate and transformed the cyanobacterialmass. Bel ow the superficial cyanobacterial crust, humus was made of a loose assemblage of enchytraeid faeces where these animals were present, or of a compact assemblage of cyanobacteria and amorphous organic matter where mites were the dominant animalgroup. Roots abounded in the humified part of the crust. We concl ude that soil invertebrates, in particular enchytraeid worms, are important for the accumulation of organic matter on granite outcrops, and so therefore for the encroachment of plant succession.