scholarly journals Priority effects and non-hierarchical competition shape species composition in a complex grassland community

2018 ◽  
Author(s):  
Lawrence H. Uricchio ◽  
S. Caroline Daws ◽  
Erin R. Spear ◽  
Erin A. Mordecai
Keyword(s):  
Species Composition ◽  
Exotic Species ◽  
Native Species ◽  
Complex Mixture ◽  
Single Species ◽  
Priority Effects ◽  
Complex Species ◽  
Species Dominance ◽  
Grassland Community ◽  
Population Dynamic Model

AbstractNiche and fitness differences control the outcome of competition, but determining their relative importance in invaded communities – which may be far from equilibrium – remains a pressing concern. Moreover, it is unclear whether classic approaches for studying competition, which were developed predominantly for pairs of interacting species, will fully capture dynamics in complex species assemblages. We parameterized a population dynamic model using competition experiments of two native and three exotic species from a grassland community. We found evidence for minimal fitness differences or niche differences between the native species, leading to slow replacement dynamics and priority effects, but large fitness advantages allowed exotics to unconditionally invade natives. Priority effects driven by strong interspecific competition between exotic species drove single-species dominance by one of two exotic species in 80% of model outcomes, while a complex mixture of non-hierarchical competition and coexistence between native and exotic species occurred in the remaining 20%. Fungal infection, a commonly hypothesized coexistence mechanism, had weak fitness effects, and is unlikely to substantially affect coexistence. In contrast to previous work on pairwise outcomes in largely native-dominated communities, our work supports a role for nearly-neutral dynamics and priority effects as drivers of species composition in invaded communities.

scholarly journals The exotic species Senecio inaequidens pays the price for arriving late in temperate European grassland communities

Oecologia ◽  
2019 ◽  
Vol 191 (3) ◽  
pp. 657-671 ◽  
Author(s):  
Benjamin M. Delory ◽  
Emanuela W. A. Weidlich ◽  
Miriam Kunz ◽  
Joshua Neitzel ◽  
Vicky M. Temperton
Keyword(s):  
Exotic Species ◽  
Native Species ◽  
Species Abundance ◽  
Priority Effects ◽  
Native Community ◽  
Grassland Community ◽  
Early Arrival ◽  
Senecio Inaequidens ◽  
A Site ◽  
Timing Of Arrival

Abstract The exotic South African ragwort (Senecio inaequidens DC.) rapidly spread across Central Europe after its introduction, but we still do not know to what extent its timing of arrival in a plant community (i.e. before or after natives) and the composition of the native community being invaded affect (1) its capacity to invade a European grassland, (2) the performance of the native species, and (3) the direction and strength of priority effects. In a greenhouse experiment, we manipulated the timing of arrival of the exotic species (Senecio) and the composition of the native community to test the influence of these factors on the productivity and N content of exotic and native species. We also investigated if the plant species origin (native or exotic) and the native community composition affected the benefit of arriving early and the cost of arriving late in the community. The establishment success of Senecio strongly depended on its timing of arrival in a grassland community. Senecio benefited more from arriving early than did the natives. The presence of legumes in the community did not favour invasion by Senecio. When natives arrived later than Senecio, however, priority effects were weaker when legumes were part of the native community. Our results showed that inhibitory priority effects created by natives can lower the risk of invasion by Senecio. An early arrival of this species at a site with low native species abundance is a scenario that could favour invasion.

scholarly journals The exotic species Senecio inaequidens pays the price for arriving late in temperate European grasslands

2019 ◽  
Author(s):  
Benjamin Delory ◽  
Emanuela W. A. Weidlich ◽  
Miriam Kunz ◽  
Joshua Neitzel ◽  
Vicky Temperton
Keyword(s):  
Exotic Species ◽  
Native Species ◽  
Species Abundance ◽  
Priority Effects ◽  
Distribution Area ◽  
Native Community ◽  
Grassland Community ◽  
Early Arrival ◽  
Senecio Inaequidens ◽  
Timing Of Arrival

The South African ragwort (Senecio inaequidens DC.) is one of the fastest exotic plant invaders in Central Europe but, despite its large distribution area, it is still not commonly found in European grasslands. In order to better understand the mechanisms behind invasion resistance of grassland communities to S. inaequidens, we determined (1) to what extent the timing of arrival of S. inaequidens in the community affected its invasiveness as well as the performance of the native species, and (2) how the direction and strength of priority effects were affected by the composition of the native community being invaded, particularly with regard to the presence of N2-fixing species (legumes). In a greenhouse experiment, we manipulated the timing of arrival of the exotic species in the community and the composition of the native background community to test the influence of these factors on the productivity and N content of exotic and native species. Using a set of interaction indices, we also investigated if the plant species origin (native or exotic) and the native community composition affected the benefit of arriving early and the cost of arriving late (i.e., priority effects) in the community. We showed that both exotic and native species created inhibitory priority effects for late-arriving species. The establishment success of S. inaequidens strongly depended on its timing of arrival in a grassland community. On average, S. inaequidens benefited more from arriving early than the natives. We did not find any evidence to support that the presence of legumes in the background community would favour invasion by S. inaequidens. When natives arrived later than S. inaequidens, however, priority effects were weaker when legumes were present in the native community. Synthesis: we showed that priority effects created by natives can lower the risk of invasion by S. inaequidens and are an important mechanism to explain why this exotic species is not commonly found in European grasslands yet. Our results suggest that an early arrival of this species at a site with low native species abundance (e.g., following a disturbance) is a scenario that could favour invasion by S. inaequidens.

scholarly journals Priority Effects and Nonhierarchical Competition Shape Species Composition in a Complex Grassland Community

2019 ◽  
Vol 193 (2) ◽  
pp. 213-226 ◽  
Author(s):  
Lawrence H. Uricchio ◽  
S. Caroline Daws ◽  
Erin R. Spear ◽  
Erin A. Mordecai
Keyword(s):  
Species Composition ◽  
Priority Effects ◽  
Grassland Community

The loss of native terrestrial small mammals in large urban reserves in the Australian Capital Territory

2010 ◽  
Vol 16 (1) ◽  
pp. 36 ◽  
Author(s):  
A. J. Buckmaster ◽  
W. S. Osborne ◽  
N. Webb
Keyword(s):  
Species Composition ◽  
Exotic Species ◽  
Native Species ◽  
Indirect Detection ◽  
Urban Landscapes ◽  
Australian Capital Territory ◽  
Mammal Species ◽  
Detection Techniques ◽  
Australian Capital ◽  
Terrestrial Mammals

Urban development can alter species composition and diversity within an area through biotic homogenization, the introduction of exotic species, and localized extinctions of native species. In this study we examined the composition and diversity of small terrestrial mammals within nature reserves surrounded by urban landscapes and compared this with previous surveys of these reserves and nearby non-urban reserves with similar vegetative and geomorphological characteristics. A combination of live trapping and indirect detection techniques was employed in eight reserves in the Australian Capital Territory and surrounding New South Wales to determine current species composition. Compared with previous studies and the non-urban reserves, the urban reserves appear to have lost two-thirds of their native terrestrial small mammal species in the past 26 years. Exotic species were present in all urban reserves, but were only associated with areas characterized by human-induced disturbance in non-urban reserves. Possible causes of this disparity in native species diversity between urban and non-urban reserves are discussed.

Vegetation change in an urban grassy woodland 1974 - 2000

2004 ◽  
Vol 52 (5) ◽  
pp. 597 ◽  
Author(s):  
J. B. Kirkpatrick
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Exotic Species ◽  
Native Species ◽  
Vegetation Change ◽  
Structural Changes ◽  
Linear Models ◽  
Tree Cover ◽  
Native Plant ◽  
Native Species Richness

Few temporal studies document vegetation change in Australian temperate grassy woodlands. Floristic and structural data were collected from 68 randomly located sites in the Queens Domain, an urban grassy woodland remnant, in 1974, 1984, 1994 and 2000 and a search made for rare species. Species of conservation significance were concentrated at highly disturbed sites, whereas vegetation types of conservation significance decreased in area as a result of increases in the numbers of Allocasuarina verticillata, which caused a change in many unmown areas from Eucalyptus viminalis grassy woodland to E. viminalis–A. verticillata woodland/forest or A. verticillata open/closed forest. Structural changes were associated with changes in species composition and an increase in native-species richness. Increases in tree cover occurred where fires were most frequent, possibly as a result of the lack of mammalian herbivores. The frequencies of herbs and annual grasses were strongly affected by precipitation in the month of sampling. Half of the species that showed a consistent rise or fall through time were woody plants, approximately twice the number expected. In the dataset as a whole, species-richness variables were largely explained by varying combinations of variables related to moisture availability, altitude and the incidence of mowing. The strongest influences on species composition were the same, although slope and time since the last fire also contributed to multiple regression and generalised linear models. Compositional stability was positively related to native-species richness, whereas high levels of exotic-species richness occurred at both low and high levels of native-species richness. The maintenance of native-plant biodiversity on the Domain requires such counterintuitive measures as the maintenance of exotic trees and the control of native trees, demonstrating the contingencies of conservation management in fragmented vegetation that consists of a mixture of native and exotic species.

scholarly journals Contemporary morphological diversification of passerine birds introduced to the Hawaiian archipelago

2011 ◽  
Vol 278 (1716) ◽  
pp. 2392-2400 ◽  
Author(s):  
Blake A. Mathys ◽  
Julie L. Lockwood
Keyword(s):  
Exotic Species ◽  
Native Species ◽  
Bird Species ◽  
Single Species ◽  
Adaptive Divergence ◽  
Evolutionary Divergence ◽  
Contemporary Evolution ◽  
Origin Time ◽  
Hawaiian Archipelago ◽  
Introduced Range

Species that have been introduced to islands experience novel and strong selection pressures after establishment. There is evidence that exotic species diverge from their native source populations; further, a few studies have demonstrated adaptive divergence across multiple exotic populations of a single species. Exotic birds provide a good study system, as they have been introduced to many locations worldwide, and we often know details concerning the propagule origin, time of introduction, and dynamics of establishment and dispersal within the introduced range. These data make them especially conducive to the examination of contemporary evolution. Island faunas have received intense scrutiny, therefore we have expectations concerning the patterns of diversification for exotic species. We examine six passerine bird species that were introduced to the Hawaiian archipelago less than 150 years ago. We find that five of these show morphological divergence among islands from the time since they were established. We demonstrate that some of this divergence cannot be accounted for by genetic drift, and therefore we must consider adaptive evolution to explain it. We also evaluate evolutionary divergence rates and find that these species are diverging at similar rates to those found in published studies of contemporary evolution in native species.

A review of the Afrotropical sand tampan, Ornithodoros savignyi: a complex species.

2021 ◽  
Vol 16 (036) ◽  
Author(s):  
Roxanne Albertha Charles
Keyword(s):  
Species Complex ◽  
Single Species ◽  
Biological Molecules ◽  
Soft Tick ◽  
Complex Species ◽  
Lake Chad ◽  
Ornithodoros Savignyi ◽  
Morphological Studies ◽  
Biological Studies ◽  
Wide Range

Abstract The sand tampan, Ornithodoros savignyi (Audouin, 1827), is an economically important soft tick of the Afrotropics parasitising a wide range of livestock and humans. These ticks are known to inflict painful bites which may be fatal in susceptible hosts. Historically thought to be a single species, Ornithodoros savignyi is now considered to be a complex of four tick subspecies based on molecular and morphological studies. They include Ornithodoros (Ornithodoros) kalahariensis, O. (O.) pavimentosus, O. (O.) noorsveldensis and O. (O.) savignyi. As such there may be significant implications for previous biological studies conducted on this tick. Therefore, for the purposes of this review, sand tampan toxicosis and potentially useful biological molecules have been discussed for O. (O.) savignyi sensu lato since most reported work was based on ticks collected from the Kalahari and Lake Chad region. An overview of the host range and vector biology for the O. (O.) savignyi species complex will also be examined.

scholarly journals Squamata reptiles of a fragment of tropical dry forest in northwestern Venezuela (Lake Maracaibo region)

Check List ◽  
2012 ◽  
Vol 8 (6) ◽  
pp. 1220 ◽  
Author(s):  
Junior T. Larreal ◽  
Gilson A. Rivas ◽  
Carlos Portillo-Quintero ◽  
Tito R. Barros
Keyword(s):  
Species Composition ◽  
San Francisco ◽  
Tropical Dry Forest ◽  
Single Species ◽  
Dry Forest ◽  
Forest Fragment ◽  
Dry Forests ◽  
Maracaibo Basin ◽  
Lake Maracaibo

We present a commented taxonomic list of the reptiles found during herpetological surveys carried out in an isolated fragment of tropical dry forest located in the municipality of San Francisco, Zulia state, northwestern Venezuela between January-December 2011. We report a total of 24 species belonging to the order Squamata, distributed in 12 families and 21 genera. Colubridae is the most diverse family with six species, followed by Dipsadidae (four species), Boidae, Gymnophthalmidae, Phyllodactylidae and Teiidae with two species each, and finally Dactyloidae, Iguanidae, Elapidae, Gekkonidae, Sphaerodactylidae and Viperidae with a single species each. The species composition at this site matches what would be expected in a tropical dry forest in the region. Our study suggests that this isolated tropical dry forest fragment is the last refuge of the herpetofauna that once occupied much of the dry forests of the northern Maracaibo basin and should therefore be considered for conservation purposes.

scholarly journals Generation and Characterization of Indoor Fungal Aerosols for Inhalation Studies

2016 ◽  
Vol 82 (8) ◽  
pp. 2479-2493 ◽  
Author(s):  
Anne Mette Madsen ◽  
Søren T. Larsen ◽  
Ismo K. Koponen ◽  
Kirsten I. Kling ◽  
Afnan Barooni ◽  
...  
Keyword(s):  
Species Composition ◽  
Indoor Environment ◽  
Building Materials ◽  
Inhalation Exposure ◽  
Single Species ◽  
Fungal Species ◽  
Exposure Level ◽  
Exposure System ◽  
Content Type ◽  
Water Damage

ABSTRACTIn the indoor environment, people are exposed to several fungal species. Evident dampness is associated with increased respiratory symptoms. To examine the immune responses associated with fungal exposure, mice are often exposed to a single species grown on an agar medium. The aim of this study was to develop an inhalation exposure system to be able to examine responses in mice exposed to mixed fungal species aerosolized from fungus-infested building materials. Indoor airborne fungi were sampled and cultivated on gypsum boards. Aerosols were characterized and compared with aerosols in homes. Aerosols containing 107CFU of fungi/m3air were generated repeatedly from fungus-infested gypsum boards in a mouse exposure chamber. Aerosols containedAspergillus nidulans,Aspergillus niger,Aspergillus ustus,Aspergillus versicolor,Chaetomium globosum,Cladosporiumherbarum,Penicillium brevicompactum,Penicillium camemberti,Penicillium chrysogenum,Penicillium commune,Penicillium glabrum,Penicillium olsonii,Penicillium rugulosum,Stachybotrys chartarum, andWallemia sebi. They were all among the most abundant airborne species identified in 28 homes. Nine species from gypsum boards and 11 species in the homes are associated with water damage. Most fungi were present as single spores, but chains and clusters of different species and fragments were also present. The variation in exposure level during the 60 min of aerosol generation was similar to the variation measured in homes. Through aerosolization of fungi from the indoor environment, cultured on gypsum boards, it was possible to generate realistic aerosols in terms of species composition, concentration, and particle sizes. The inhalation-exposure system can be used to study responses to indoor fungi associated with water damage and the importance of fungal species composition.

scholarly journals Priority Treatment Leaves Grassland Restoration Vulnerable to Invasion

Diversity ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 71 ◽  
Author(s):  
Katharine L. Stuble ◽  
Truman P. Young
Keyword(s):  
Native Species ◽  
Priority Effects ◽  
Native Grasses ◽  
Target Species ◽  
California Grasslands ◽  
Early Arrival ◽  
Regional Species Pool ◽  
Conservation Concern ◽  
Indirect Impacts ◽  
One Year

Priority effects can be used to promote target species during restoration. Early planting can provide an advantage over later-arriving species, increasing abundance of these early-arrivers in restored communities. However, we have limited knowledge of the indirect impacts of priority effects in restoration. In particular, we do not understand how priority effects impact non-target species. Of particular conservation concern is how these priority effects influence establishment by non-native species. We use a field-based mesocosm experiment to explore the impacts of priority effects on both target and non-target species in California grasslands. Specifically, we seeded native grasses and forbs, manipulating order of arrival by planting them at the same time, planting forbs one year before grasses, planting grasses one year before forbs, or planting each functional group alone. While our study plots were tilled and weeded for the first year, the regional species pool was heavily invaded. We found that, while early-arrival of native grasses did not promote establishment of non-native species, giving priority to native forbs ultimately left our restoration mesocosms vulnerable to invasion by non-native species. This suggests that, in some cases, establishment of non-native species may be an unintended consequence of using priority treatments as a restoration tool.

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