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Juan Arroyo - One of the best experts on this subject based on the ideXlab platform.
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ecology and biogeography of plant communities associated with the post plio pleistocene relict Rhododendron Ponticum subsp baeticum in southern spain
Journal of Biogeography, 2007Co-Authors: J A Mejias, Juan Arroyo, Teodoro MaranonAbstract:Aims Rhododendron Ponticum L. is reputed to be a post Plio-Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. Ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500-m main transect in each site, along the stream or river course, in which we placed five 20-m-long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. Ponticum individuals. Results Rhododendron Ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. Ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. Ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. Ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. Ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. Ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.
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communities associated with the post plio pleistocene relict Rhododendron Ponticum subsp baeticum in southern
2007Co-Authors: Juan ArroyoAbstract:Aims Rhododendron Ponticum L. is reputed to be a post Plio-Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. Ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500-m main transect in each site, along the stream or river course, in which we placed five 20-m-long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. Ponticum individuals. Results Rhododendron Ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. Ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. Ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. Ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. Ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. Ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.
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pollination ecology and seed production of Rhododendron Ponticum in native and exotic habitats
Biodiversity and Conservation, 2006Co-Authors: Jane C Stout, Juan Arroyo, John A N Parnell, Tasman P CroweAbstract:Alien plants may be reproductively limited in exotic habitats because of a lack of mutualistic pollinators. However, if plants are adequately served by generalist pollinators, successful reproduction, naturalisation and expansion into exotic habitats may occur. Rhododendron Ponticum is very successful, ecologically damaging invasive plant in Britain and Ireland, but is in decline in its native Iberian habitat. It spreads locally by sending out lateral branches, but for longer distance dispersal it relies on sexually produced seeds. Little is known about R. Ponticum's pollination ecology and breeding biology in invaded habitats. We examined the flower-visiting communities and maternal reproductive success of R. Ponticum in native populations in southern Spain and in exotic ones in Ireland. R. Ponticum in flowers are visited by various generalist (polylectic) pollinator species in both native and exotic habitats. Although different species visited flowers in Ireland and Spain, the flower visitation rate was not significantly different. Insects foraging on R. Ponticum in Spain carried less R. Ponticum pollen than their Irish counterparts, and carried fewer pollen types. Fruit production per inflorescence varied greatly within all populations but was significantly correlated with visitation at the population level. Nectar was significantly depleted by insects in some exotic populations, suggesting that this invasive species is providing a floral resource for native insects in some parts of Ireland. The generality of the pollination system may be factor contributing to R.Ponticum's success in exotic habitats.
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reproductive ecology of Rhododendron Ponticum ericaceae in relict mediterranean populations
Botanical Journal of the Linnean Society, 2002Co-Authors: J A Mejias, Juan Arroyo, Fernando OjedaAbstract:In the southern Iberian Peninsula, Rhododendron Ponticum occurs in restricted and vulnerable populations as a Tertiary relict. Population structure and the main phases of the reproductive process were examined in order to shed light on recruitment patterns and limitations. Rhododendron Ponticum flowers are self-compatible and attract a diverse array of insects, which are responsible for a considerable number of seeds set in the populations. Nevertheless, only adults form populations, whilst seedlings are scarce and saplings virtually absent (only two juveniles out of 2489 adults sampled). Non-specialized vegetative multiplication by layering was observed. Recruitment failure seems to depend on the scarcity of safe microsites, which are free from drought, for seedling establishment. The observations contrast with R. Ponticum ’s reputation as an aggressive invader in temperate Atlantic areas. It is proposed that the species shows a variable balance between sexual reproduction and vegetative multiplication depending on environmental conditions. At present, only the latter seems to be prevailing in relict populations in the Iberian Peninsula. This flexible reproductive strategy is also discussed as a mechanism allowing persistence during geological climatic oscillations. © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 297‐311. ADDITIONAL KEYWORDS: Bombus ‐ breeding system ‐ clonal plants ‐ Macroglossum ‐ plant extinction ‐ pollination ‐ recruitment ‐ seedling survival ‐ threatened plants ‐ refugia.
J A Mejias - One of the best experts on this subject based on the ideXlab platform.
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ecology and biogeography of plant communities associated with the post plio pleistocene relict Rhododendron Ponticum subsp baeticum in southern spain
Journal of Biogeography, 2007Co-Authors: J A Mejias, Juan Arroyo, Teodoro MaranonAbstract:Aims Rhododendron Ponticum L. is reputed to be a post Plio-Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. Ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500-m main transect in each site, along the stream or river course, in which we placed five 20-m-long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. Ponticum individuals. Results Rhododendron Ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. Ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. Ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. Ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. Ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. Ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.
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reproductive ecology of Rhododendron Ponticum ericaceae in relict mediterranean populations
Botanical Journal of the Linnean Society, 2002Co-Authors: J A Mejias, Juan Arroyo, Fernando OjedaAbstract:In the southern Iberian Peninsula, Rhododendron Ponticum occurs in restricted and vulnerable populations as a Tertiary relict. Population structure and the main phases of the reproductive process were examined in order to shed light on recruitment patterns and limitations. Rhododendron Ponticum flowers are self-compatible and attract a diverse array of insects, which are responsible for a considerable number of seeds set in the populations. Nevertheless, only adults form populations, whilst seedlings are scarce and saplings virtually absent (only two juveniles out of 2489 adults sampled). Non-specialized vegetative multiplication by layering was observed. Recruitment failure seems to depend on the scarcity of safe microsites, which are free from drought, for seedling establishment. The observations contrast with R. Ponticum ’s reputation as an aggressive invader in temperate Atlantic areas. It is proposed that the species shows a variable balance between sexual reproduction and vegetative multiplication depending on environmental conditions. At present, only the latter seems to be prevailing in relict populations in the Iberian Peninsula. This flexible reproductive strategy is also discussed as a mechanism allowing persistence during geological climatic oscillations. © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 297‐311. ADDITIONAL KEYWORDS: Bombus ‐ breeding system ‐ clonal plants ‐ Macroglossum ‐ plant extinction ‐ pollination ‐ recruitment ‐ seedling survival ‐ threatened plants ‐ refugia.
Jane C Stout - One of the best experts on this subject based on the ideXlab platform.
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insect flower interaction network structure is resilient to a temporary pulse of floral resources from invasive Rhododendron Ponticum
PLOS ONE, 2015Co-Authors: Erin Jo Tiedeken, Jane C StoutAbstract:Invasive alien plants can compete with native plants for resources, and may ultimately decrease native plant diversity and/or abundance in invaded sites. This could have consequences for native mutualistic interactions, such as pollination. Although invasive plants often become highly connected in plant-pollinator interaction networks, in temperate climates they usually only flower for part of the season. Unless sufficient alternative plants flower outside this period, whole-season floral resources may be reduced by invasion. We hypothesized that the cessation of flowering of a dominant invasive plant would lead to dramatic, seasonal compositional changes in plant-pollinator communities, and subsequent changes in network structure. We investigated variation in floral resources, flower-visiting insect communities, and interaction networks during and after the flowering of invasive Rhododendron Ponticum in four invaded Irish woodland sites. Floral resources decreased significantly after R. Ponticum flowering, but the magnitude of the decrease varied among sites. Neither insect abundance nor richness varied between the two periods (during and after R. Ponticum flowering), yet insect community composition was distinct, mostly due to a significant reduction in Bombus abundance after flowering. During flowering R. Ponticum was frequently visited by Bombus; after flowering, these highly mobile pollinators presumably left to find alternative floral resources. Despite compositional changes, however, network structural properties remained stable after R. Ponticum flowering ceased: generality increased, but quantitative connectance, interaction evenness, vulnerability, H’2 and network size did not change. This is likely because after R. Ponticum flowering, two to three alternative plant species became prominent in networks and insects increased their diet breadth, as indicated by the increase in network-level generality. We conclude that network structure is robust to seasonal changes in floral abundance at sites invaded by alien, mass-flowering plant species, as long as alternative floral resources remain throughout the season to support the flower-visiting community.
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invasive plant integration into native plant pollinator networks across europe
Proceedings of The Royal Society B: Biological Sciences, 2009Co-Authors: Montserrat Vila, Jane C Stout, Ignasi Bartomeus, Anke C Dietzsch, Theodora Petanidou, Ingolf Steffandewenter, Thomas TscheulinAbstract:The structure of plant–pollinator networks has been claimed to be resilient to changes in species composition due to the weak degree of dependence among mutualistic partners. However, detailed empirical investigations of the consequences of introducing an alien plant species into mutualistic networks are lacking. We present the first cross-European analysis by using a standardized protocol to assess the degree to which a particular alien plant species (i.e. Carpobrotus affine acinaciformis , Impatiens glandulifera , Opuntia stricta , Rhododendron Ponticum and Solanum elaeagnifolium ) becomes integrated into existing native plant–pollinator networks, and how this translates to changes in network structure. Alien species were visited by almost half of the pollinator species present, accounting on average for 42 per cent of the visits and 24 per cent of the network interactions. Furthermore, in general, pollinators depended upon alien plants more than on native plants. However, despite the fact that invaded communities received more visits than uninvaded communities, the dominant role of alien species over natives did not translate into overall changes in network connectance, plant linkage level and nestedness. Our results imply that although supergeneralist alien plants can play a central role in the networks, the structure of the networks appears to be very permeable and robust to the introduction of invasive alien species into the network.
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reproductive biology of the invasive exotic shrub Rhododendron Ponticum l ericaceae
Botanical Journal of the Linnean Society, 2007Co-Authors: Jane C StoutAbstract:The reproductive biology of an exotic species will affect its ability to become naturalized and invasive in non-native habitats. Rhododendron Ponticum is an ecologically damaging exotic weed in the British Isles, which spreads predominantly by seed. I investigated how inbreeding and outcrossing affect seed production and germination in a wild population of this species in Ireland. Experimental manipulations revealed low fruit and seed set when insects were excluded from flowers, suggesting that this species has limited capability for spontaneous autogamy. Hand-pollination treatments showed that, although flowers are self-compatible (with self and same plant pollen), higher levels of seed set occur following outcrossing (xenogamy). There was no significant difference in rate of germination of seeds from inbred or outcrossed treatments. The addition of xenogamous pollen to open flowers did not increase fruit or seed set, suggesting that flowers in this population are not pollen limited: native generalist pollinators, mainly bumblebees (Bombus spp.), are providing an adequate pollinator service. This work demonstrates that outcrossing increases seed set and pollinators are required to facilitate this. Hence, generalist native pollinators can promote invasion by exotic plants. Native pollinators can clearly play an important part in alien species invasion. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 373–381.
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pollination of invasive Rhododendron Ponticum ericaceae in ireland
Apidologie, 2007Co-Authors: Jane C StoutAbstract:Several insect species visited exotic Rhododendron Ponticum flowers, but bumblebees were most common. Only bumblebees (and one Vespula) contacted the flower stigma whilst foraging and are probably the main pollinators. One-third of insect visits resulted in stigma contact and visitation rates were high. This explains the high seed set reported elsewhere. There were significant differences according to the body size of visitors, with large queen bees contacting stigmas more often than smaller workers. There were no significant differences in behaviour of three species (Bombus jonellus, B. lucorum and B. monticola) and all bees tended to move short distances between flowers on a single plant. Longer flights and movements among plants were rare. Pollen carryover was estimated to be high: there was no decline in the amount of pollen deposited on stigmas from the first to fifth flower visited. The impact of bee behaviour on reproduction and invasion by exotic R. Ponticum is discussed.
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pollination ecology and seed production of Rhododendron Ponticum in native and exotic habitats
Biodiversity and Conservation, 2006Co-Authors: Jane C Stout, Juan Arroyo, John A N Parnell, Tasman P CroweAbstract:Alien plants may be reproductively limited in exotic habitats because of a lack of mutualistic pollinators. However, if plants are adequately served by generalist pollinators, successful reproduction, naturalisation and expansion into exotic habitats may occur. Rhododendron Ponticum is very successful, ecologically damaging invasive plant in Britain and Ireland, but is in decline in its native Iberian habitat. It spreads locally by sending out lateral branches, but for longer distance dispersal it relies on sexually produced seeds. Little is known about R. Ponticum's pollination ecology and breeding biology in invaded habitats. We examined the flower-visiting communities and maternal reproductive success of R. Ponticum in native populations in southern Spain and in exotic ones in Ireland. R. Ponticum in flowers are visited by various generalist (polylectic) pollinator species in both native and exotic habitats. Although different species visited flowers in Ireland and Spain, the flower visitation rate was not significantly different. Insects foraging on R. Ponticum in Spain carried less R. Ponticum pollen than their Irish counterparts, and carried fewer pollen types. Fruit production per inflorescence varied greatly within all populations but was significantly correlated with visitation at the population level. Nectar was significantly depleted by insects in some exotic populations, suggesting that this invasive species is providing a floral resource for native insects in some parts of Ireland. The generality of the pollination system may be factor contributing to R.Ponticum's success in exotic habitats.
Anabela Romano - One of the best experts on this subject based on the ideXlab platform.
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chlorophyll fluorescence in micropropagated Rhododendron Ponticum subsp baeticum plants in response to different irradiances
Biologia Plantarum, 2010Co-Authors: Maria Leonor Osorio, Jose Carlos Da Silveira Osorio, Anabela RomanoAbstract:The aim of this study was to investigate acclimation of micropropagated plants of Rhododendron Ponticum subsp. baeticum to different irradiances and recovery after exposure to high irradiance. Plants grown under high (HL) or intermediate (IL) irradiances displayed higher values of maximum electron transport rate (ETRmax) and light saturation coefficient (Ek) than plants grown under low irradiance (LL). The capacity of tolerance to photoinhibition (as assessed by the response of photochemical quenching, qp) varied as follows: HL > IL > LL. Thermal energy dissipation (qN) was also affected by growth irradiance, with higher saturating values being observed in HL plants. Light-response curves suggested a gradual replacement of qp by qN with increasing irradiance. Following exposure to irradiance higher than 1500 μmol m−2 s−1, a prolonged reduction of the maximal photochemical efficiency of PS 2 (Fv/Fm) was observed in LL plants, indicating the occurrence of chronic photoinhibition. In contrary, the decrease in Fv/Fm was quickly reverted in HL plants, pointing to a reversible photoinhibition.
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in vitro micropropagation of endangered Rhododendron Ponticum l subsp baeticum boissier reuter handel mazzetti
Biodiversity and Conservation, 2005Co-Authors: R Almeida, Sandra Goncalves, Anabela RomanoAbstract:In vitro propagation of Rhododendron Ponticum L. subsp. baeticum, an endangered species present in limited and vulnerable populations as a Tertiary relict in the southern Iberian Peninsula, was attained. Several cytokinin:IAA ratios and a range of zeatin concentrations were evaluated for their effect on shoot multiplication from apical shoots and nodal segments. The type of cytokinin and the origin of the explant were the most important factors affecting shoot multiplication. The highest shoot multiplication rate was obtained from single-nodal explants on medium supplemented with zeatin. Increasing zeatin concentration promotes shoot multiplication independently of explant type, although this effect tends to decrease with higher zeatin concentration. Shoot growth was higher in apical shoots and it was not stimulated by the presence of auxin. A number of experiments were conducted to identify suitable procedures for rooting of in vitro produced shoots. The best results in terms of in vitro rooting were obtained with Anderson’s modified medium with macrosalts reduced to one-half, regardless of the auxin or its concentration in the medium. Although rooting frequency rose to 97% by basal immersion of shoots in auxin concentrated solution followed by in vitro culture on an auxin-free medium, the survival of the plants after 6 months of acclimatization was poor (50%). Best results (100% rooting and survival) were observed for ex vitro rooting. The micropropagated plants from this study were successfully reintroduced into their natural habitat (87% of survival after 8 months).
Teodoro Maranon - One of the best experts on this subject based on the ideXlab platform.
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ecology and biogeography of plant communities associated with the post plio pleistocene relict Rhododendron Ponticum subsp baeticum in southern spain
Journal of Biogeography, 2007Co-Authors: J A Mejias, Juan Arroyo, Teodoro MaranonAbstract:Aims Rhododendron Ponticum L. is reputed to be a post Plio-Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. Ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500-m main transect in each site, along the stream or river course, in which we placed five 20-m-long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. Ponticum individuals. Results Rhododendron Ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. Ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. Ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. Ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. Ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. Ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.