473 research outputs found
The Ecological Importance of Allelopathy
No full textAllelopathy (i.e., chemical interaction among species) was originally conceived as inclusive of positive and negative effects of plants on other plants, and we adopt this view. Most studies of allelopathy have been phenomenological, but we focus on studies that have explored the ecological significance of this interaction. The literature suggests that studies of allelopathy have been particularly important for three foci in ecology: species distribution, conditionality of interactions, and maintenance of species diversity. There is evidence that allelopathy influences local distributions of plant species around the world. Allelopathic conditionality appears to arise through coevolution, and this is a mechanism for plant invasions. Finally, allelopathy promotes species coexistence via intransitive competition, modifications of direct interactions, and (co)evolution. Recent advances additionally suggest that coexistence might be favored through biochemical recognition. The preponderance of phenomenological studies notwithstanding, allelopathy has broad ecological consequences.Fil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Callaway, Ragan M.. University of Montana; Estados Unido
Exotic insect pollinators and native pollination systems
No full textInsect pollinators have been relocated by humans for millennia and are, thus, among the world’s earliest intentional exotic introductions. The introduction of managed bees for crop pollination services remains, to this day, a common and growing practice worldwide and the number of different bee species that are used commercially is increasing. Being generalists and frequently social, these exotic species have the potential to have a wide range of impacts on native bees and plants. Thus, understanding the consequences of introduced species on native pollinator systems is a priority. We generated a global database and evaluated the impacts of the two main groups of invasive bees, Apis mellifera and Bombus spp., on their pollination services to native flora and impacts on native pollinators. In a meta-analysis, we found that per-visit pollination efficiency of exotic pollinators was, on average, 55% less efficient than native pollinators when visiting flowers of native species. In contrast to per-visit pollination efficiency, our meta-analysis showed that visitation frequency by exotic pollinators was, on average, 80% higher than native pollinators. The higher visitation frequency of exotic pollinators overcame deficiencies in pollen removal and transfer resulting in seed/fruit set levels similar to native pollinators. Also, evidence showed that exotic pollinators can displace native insect and bird pollinators. However, the direct effects of exotic insect pollinators on native pollination systems can be context dependent, ranging from mutualism to antagonism.Fil: Debnam, Scott. University of Montana; Estados UnidosFil: Sáez, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Callaway, Ragan M.. University of Montana; Estados Unido
Cheer Up!
No full text(Color) Four poem stanzas written as doses I-IV, in accordance with the poem's subtitle, "A Dose of Optimism." The red, white, and blue medicine bottle reads "Optimism The Does to be Taken as Required" and a British Flag is pinned into the cork stopper. A message on the back informs potential buyers of the card to obtain them directly from the author, Jule Critten at her residence. This card is uninscribed and unposted.This collection previously belonged to Dominic Hibberd, an English biographer most noted for the biographies of Wilfred Owen and Harold Monro, World War I poets. He collected these postcards for research purposes
Courage
No full text(Color) This postcard displays an image of seven Allied flags (United Kingdom, France, Russia, Belgium, Serbia, Italy, and Japan) with an accompanying poem to encourage the soldiers and folks back home to "Just Keep On!" The back indicates that the text author produces the poems herself out of a hotel, and proceeds go to the "Comforts for the Wounded at the Army Nursing Homes, Folkestone." This card is uninscribed and unposted.This collection previously belonged to Dominic Hibberd, an English biographer most noted for the biographies of Wilfred Owen and Harold Monro, World War I poets. He collected these postcards for research purposes
Data from: García Y, Callaway RM, Diaconu A, Montesinos D (2013) Invasive and Non-Invasive Congeners Show Similar Trait Shifts between Their Same Native and Non-Native Ranges. PLoS ONE 8(12): e82281
No full text<p>Data available from: García Y, Callaway RM, Diaconu A, Montesinos D (2013) Invasive and Non-Invasive Congeners Show Similar Trait Shifts between Their Same Native and Non-Native Ranges. PLoS ONE 8(12): e82281. doi:10.1371/journal.pone.0082281</p>
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Competition does not come at the expense of colonization in seed morphs with increased size and dispersal
No full textPREMISE OF THE STUDY: Seed-level trade-offs of heterocarpic species remain poorly understood. We propose that seedlings emerging from seeds with apermanent pappus (dispersing seeds) are stronger competitors than those emerging from seeds without a pappus (nondispersing seeds) because dispersingseeds are larger and germinate faster than nondispersing seeds in Centaurea solstitialis .METHODS: We conducted a competition experiment with both seed morphs, in which we recorded emergence rate and proportion, estimated seed dispersalby wind (anemochory) and by mammals (exozoochory), and measured size and abundance of seed morphs.KEY RESULTS: We found that seedlings from pappus seeds had greater competitive abilities than those from non-pappus seeds. Similarly, pappus seedlingsemerged at much faster rates and larger proportions than non-pappus seedlings. Pappus seeds were larger, were more numerous, and displayed improvedexozoochory compared to non-pappus seeds. Anemochory was poor for both seed morphs.CONCLUSIONS: We found support for our hypothesis, raising in turn the possibility that competition and colonization are positively associated in seedmorphs of heterocarpic species with enhanced exozoochory of larger seeds. These fi ndings are not consistent with those from heterocarpic species withenhanced anemochory of smaller seeds or slower-germinating seeds. Our results additionally suggest that pappus and non-pappus seeds of C. solstitialisdisplay a task-division strategy in which pappus morphs colonize and preempt unoccupied sites through improved dispersal and fast and large emergenceof seedlings with increased competitive abilities, whereas non-pappus morphs promote site persistence through delayed germination and dormancy.This strategy may contribute to the success of C. solstitialis in highly variable environments.Fil: Miguel, María Florencia. Universidad Nacional de la Pampa. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Lortie, Christopher J.. University of York; Reino UnidoFil: Callaway, Ragan M.. University of Montana; Estados UnidosFil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin
Inter-regional hybrids of native and invasive Centaurea solstitialis display intermediate competitive ability
No full textInvasive species can rapidly adapt to conditions in non‐native ranges, including changes in size and competitive ability. However, little is known about the heritability of such changes, and on the importance of hypothetical reintroductions in the maintenance of locally adapted traits. To test for this, we experimentally produced a cohort of Centaurea solstitialis of ancestry from either the native range in Spain, the invasive range in California, or inter‐regional hybrids from both ranges. We then set up one‐to‐one competition experiments with the grass Bromus hordeaceus. Centaurea solstitialis individuals grown from seed produced from two Californian parents had almost twice the competitive effect on B. hordeaceus than descendants of two Spanish parents, whereas inter‐regional hybrids between Spain and California showed intermediate values. These results suggest that, at this stage of invasion, homogenizing gene flow resulting from hypothetical re‐introductions from the native range could lower their competitive effects on the invaded plant communities.Thanks to Margarita Zorrilla and to the Callaway Lab staff. RMC was funded by NSF‐DEB 0614406 and the NSF‐EPSCR Track‐1 EPS‐1101342 (INSTEP 3). DM was funded by Micinn (2008‐0662); by FCT (PCT/BIA‐PLA/3389/2012; IF‐00066‐2013); and by the EC (FP7‐PEOPLE‐MC‐CIG‐321909). FCT is partially funded by the EU via QREN, COMPETE and FEDER.Peer reviewe
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No full textAn important hypothesis for how plants respond to introduction to new ranges is the evolution of increased competitive ability (EICA). EICA predicts that biogeographical release from natural enemies initiates a trade-off in which exotic species in non-native ranges become larger and more competitive, but invest less in consumer defences, relative to populations in native ranges. This trade-off is exceptionally complex because detecting concomitant biogeographical shifts in competitive ability and consumer defence depends upon which traits are targeted, how competition is measured, the defence chemicals quantified, whether defence chemicals do more than defend, whether ‘herbivory’ is artificial or natural, and where consumers fall on the generalist-specialist spectrum. Previous meta-analyses have successfully identified patterns but have yet to fully disentangle this complexity. We used meta-analysis to reevaluate traditional metrics used to test EICA theory and then expanded on these metrics by partitioning competitive effect and competitive tolerance measures and testing Leaf-Specific Mass in detail as a response trait. Unlike previous syntheses, our meta-analyses detected evidence consistent with the classic trade-off inherent to EICA. Plants from non-native ranges imposed greater competitive effects than plants from native ranges and were less quantitatively defended than plants from native ranges. Our results for defence were not based on complex leaf chemistry, but instead were estimated from tannins, toughness traits and primarily Leaf-Specific Mass. Species specificity occurred but did not influence the general patterns. As for all evidence for EICA-like trade-offs, we do not know if the biogeographical differences we found were caused by trade-offs per se, but they are consistent with predictions derived from the overarching hypothesis. Underestimating physical leaf structure may have contributed to two decades of tepid perspectives on the trade-offs fundamental to EICA.Fil: Callaway, Ragan M.. University of Montana; Estados UnidosFil: Lucero, Jacob E.. University of Montana; Estados Unidos. New Mexico State University.; Estados UnidosFil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Lortie, C. J.. York University; Canad
The Charge of the Loyal North Lancs
No full text(Color) This card contains a poem text with an image of two Union Flags, written for the "Local Lads" on October 25, 1916; The card is uninscribed and unposted
What makes a good neighbour? Drivers of facilitation in alpine cushion plant communities
No full textSpecies interactions, whether facilitative or competitive, play key roles in structuring plant communities. Research into these associations has focused on competitive interactions, however recently, facilitation research has increased in popularity. Using cushion plants as a model, the objective of this thesis is to determine the effect of abiotic drivers on species interactions as well as on the morphology and reproduction of a potential facilitator. Results from a New Zealand cushion species, Donatia novae-zelandiae found in mosaic alpine environments and oceanic sea-level sites were compared to those from a widespread Northern Hemisphere cushion species, Silene acaulis.
Alpine (~1000m) D. novae-zelandiae cushions produced three times as many flowers and seven times as many seeds per capsule than at sea-level, but leaves were larger at sea-level. Cushion compactness was greatest at alpine sites. After two seasons of artificially warming 1.8°C, significant decreases in seed production (35%), leaf length (5%), and width (13%) were observed in the cushions.
Donatia novae-zelandiae modestly increased species richness at the sea-level sites (1.4 ± 0.5 more species), but no species was specifically limited to growing within the cushions. Most species showed no significant association, although Dracophyllum longifolium, D. prostratum, Phyllachne colensoi, Rhacomitrium pruinosum, and Coprosma cheesemanii showed significant negative associations with Donatia novae-zelandiae at the alpine sites. Donatia novae-zelandiae may marginally increase species diversity locally, but diversity is not affected at the community level. At alpine sites, D. novae-zelandiae decreased species richness (2.5 ± 0.8 fewer species) compared to open areas.
Removing neighbours growing within the D. novae-zelandiae resulted in significant heat stress to the cushions, reducing seed production, compactness, and leaf size. Donatia novae-zelandiae, unlike other cushion species, does not appear to be acting as key a facilitator regardless of whether they grow in an alpine community, or in a more mesic, low altitude habitat. D. novae-zelandiae may in fact benefit from their association with neighbouring plants.
Unlike D. novae-zelandiae, Silene acaulis fitness at a high elevation site (2560 m) was reduced compared to the lower site (2317 m); female flower production decreased by 40%, seeds per fruit by 11.6%, and leaf size by 24% at the high site. Strong facilitators, hermaphroditic Silene acaulis individuals supported a greater number of plant species than females (hermaphrodites: 4.2 ± 0.3, females: 3.5 ± 0.2). Facilitative effects also significantly increased with elevation (2560 m: 2.1 ± 1.6, 2317 m: 3.2 ± 1.8).
The typical ‘cushion model’ so often reported in the facilitation literature does not accurately represent the cushion plant functional type as a whole. D. novae-zelandiae is not a facilitator, but may rather be acting as a competitor, particularly in alpine cushion mosaic communities. This is likely driven by the peat substrate, typical of cushion mosaic communities. In comparison, cushions growing on more skeletal substrates, such as Silene acaulis are important facilitators. Results of this thesis stress the importance of studying cushion facilitation over a broader spectrum of cushion life forms and habitats
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