The native-exotic species richness relationship varies with spatial grain of measurement and environmental conditions

Ecology ◽  
2017 ◽  
Vol 98 (12) ◽  
pp. 3086-3095 ◽  
Author(s):  
Dennis D. Tarasi ◽  
Robert K. Peet
Keyword(s):  
Species Richness ◽  
Exotic Species ◽  
Environmental Conditions ◽  
Spatial Grain

scholarly journals Diversité des insectes floricoles de Abelmoschus esculentus (Malvaceae) et leur impact sur les rendements fruitier et grainier à Maroua-Cameroun.

2020 ◽  
Vol 43:1 ◽  
pp. 7350-7365
Author(s):  
Joseph Blaise Pando ◽  
Denis Djonwangwé ◽  
Olivier Balti Moudelsia ◽  
Fernand-Nestor Tchuenguem Fohouo ◽  
Joseph Lebel Tamesse
Keyword(s):  
Species Richness ◽  
Environmental Conditions ◽  
Relative Frequency ◽  
Positive Impact ◽  
Abelmoschus Esculentus ◽  
Flowering Period ◽  
Flower Buds ◽  
Protection Contre ◽  
Pollinating Insects ◽  
Number Of Seeds

Pour déterminer la richesse spécifique, la fréquence relative, les produits alimentaires recherchés, les insectes pollinisateurs et l’impact de ces insectes sur les rendements, deux traitements ont été formés à partir du marquage de 240 boutons floraux en 2015 et 2017 chacun selon la présence ou l’absence de protection contre les insectes. Les observations ont été faites sur les fleurs de Abelmoschus esculentus en libre pollinisation du 11 au 22 septembre 2015 et du 7 au 19 septembre 2017 à Wourndé et Palar respectivement. La diversité spécifique des insectes floricoles de gombo était de 17 et 20 espèces respectivement à Wourndé et à Palar. L’indice de Jacard (J = 0,15) révèle une similarité entre les deux sites, preuve que les conditions environnementales sont similaires dans les deux habitats. Les insectes butinaient les fleurs du gombo de 8 h à 13 h, avec le pic de l’activité de l’ensemble de visites de ceux-ci situé entre 10 h et 11 h. Les insectes développaient un comportement très élaboré lors de la récolte du nectar et/ou du pollen et la consommation du pétale. On peut regrouper ces insectes en pollinisateur majeur (Lipotriches collaris), pollinisateurs mineurs [Sphecodes albilabris, Camponotus flavomarginatus, le Vespidae (1 sp.), Lasioglossum albilabris, Seladonia sp., Lasioglossum albipes, Lipotriches pulchriventris et le Formicidae (1 sp.)] et pollinisateurs occasionnels. La comparaison des rendements des fleurs non protégées à celui des fleurs protégées des insectes ont montré que les insectes ont un impact positif sur ce rendement. L’influence de ces insectes est estimée à 9,57%, 7,18% et 4,34% pour le taux de fructification, le nombre de graines/capsule et le pourcentage de graines normales respectivement. Afin d’améliorer le rendement de A. esculentus, il est conseillé de préserver les insectes floricoles non nuisibles dans les champs de gombo en évitant les traitements aux pesticides pendant la période de floraison lorsqu’ils ne se justifient pas. ABSTRACT To determine the species richness, the relative frequency, desired food products, the pollinating insects and impact of these insects on the yields, two treatments were formed from the marking of 240 flower buds in 2015 and 2017, differentiated according to the presence or absence of protection against insect’s activities. Observations were made on free-pollinated Abelmoschus esculentus flowers from 11 to 22 September 2015 and from 7 to 19 September 2017 in Wourndé and Palar respectively. The specific diversity of the flowering insects of okra was 17 and 20 species respectively in Wourndé and Palar. The Jacard index (J = 0.15) reveals a similarity between the two sites, proof that the environmental conditions are similar in both habitats. The insects foraged the flowers of the okra from 8h to 13h, with the peak of the activity of the set of visits of them located between 10 h and 11 h. The insects developed a much elaborated behaviour during the harvest of the nectar and / or the pollen and the consumption of petal. These insects can be grouped into major pollinators (Lipotriches collaris), minor pollinators [Sphecodes albilabris, Camponotus flavomarginatus, Vespidae (1 sp.), Lasioglossum albilabris, Seladonia sp., Lasioglossum albipes, Lipotriches pulchriventris and Formicidae (1 sp.)).] and occasional pollinators. By comparing the yield of unprotected flowers to that of insect-protected flowers, it appeared that insects have a positive impact on this yield. The influence of these insects is estimated at 9.57 %, 7.18 % and 4.34 % for the fruiting rate, the number of seeds / capsule and the percentage of normal seeds respectively. To improve the yield of A. esculentus, it is advisable to preserve the flower-dwelling insects in okra fields by avoiding pesticide treatments during the flowering period when they are not justified.

scholarly journals Using Biogeography to Assess Key Adaptation Strength in Two Bird Families

2017 ◽  
Author(s):  
Abdel H. Halloway ◽  
Christopher J. Whelan ◽  
Çağan H. Şekercioğlu ◽  
Joel S. Brown
Keyword(s):  
Species Richness ◽  
Environmental Conditions ◽  
New World ◽  
Extreme Environments ◽  
The Other ◽  
Latitudinal Gradients ◽  
Old World ◽  
Extended Range

AbstractAdaptations can be thought of as evolutionary technologies which allow an organism to exploit environments. Among convergent taxa, adaptations may be largely equivalent with the taxa operating in a similar set of environmental conditions, divergent with the taxa operating in different sets of environmental conditions, or superior with one taxon operating within an extended range of environmental conditions than the other. With this framework in mind, we sought to characterize the adaptations of two convergent nectarivorous bird families, the New World hummingbirds (Trochilidae) and Old World sunbirds (Nectariniidae), by comparing their biogeography. Looking at their elevational and latitudinal gradients, hummingbirds not only extend into but also maintain species richness in more extreme environments. We suspect that hummingbirds have a superior key adaptation that sunbirds lack, namely a musculoskeletal architecture that allows for hovering. Through biogeographic comparisons, we have been able to assess and understand adaptations as evolutionary technologies among two convergent bird families, a process that should work for most taxa.

NULL MODELS OF EXOTIC INVASION AND SCALE-DEPENDENT PATTERNS OF NATIVE AND EXOTIC SPECIES RICHNESS

Ecology ◽  
2004 ◽  
Vol 85 (12) ◽  
pp. 3215-3222 ◽  
Author(s):  
Jason D. Fridley ◽  
Rebecca L. Brown ◽  
John F. Bruno
Keyword(s):  
Species Richness ◽  
Exotic Species ◽  
Null Models ◽  
Exotic Invasion

Distribution, abundance, and diversity of stream fishes under variable environmental conditions

2006 ◽  
Vol 63 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Christopher M Taylor ◽  
Thomas L Holder ◽  
Riccardo A Fiorillo ◽  
Lance R Williams ◽  
R Brent Thomas ◽  
...  
Keyword(s):  
Species Richness ◽  
Environmental Conditions ◽  
Community Dynamics ◽  
Local Community ◽  
Fish Assemblages ◽  
Fish Distribution ◽  
Stream Fish ◽  
Spatial And Temporal Variability ◽  
Regional Patterns ◽  
Abundance And Diversity

The effects of stream size and flow regime on spatial and temporal variability of stream fish distribution, abundance, and diversity patterns were investigated. Assemblage variability and species richness were each significantly associated with a complex environmental gradient contrasting smaller, hydrologically variable stream localities with larger localities characterized by more stable flow regimes. Assemblages showing the least variability were the most species-rich and occurred in relatively large, stable environments. Theory suggests that species richness can be an important determinant of assemblage variability. Although this appears to be true in our system, we suggest that spatial and temporal heterogeneity in the environment largely determines both assemblage richness and variability, providing a more parsimonious explanation for the diversity–variability correlation. Changes in species richness of local assemblages across time were coordinated across the landscape, and assemblages formed spatially and temporally nested subset patterns. These results suggest an important link between local community dynamics and community-wide occurrence. At the species level, mean local persistence was significantly associated with regional occurrence. Thus, the more widespread a species was, the greater its local persistence. Our results illustrate how the integrity of local stream fish assemblages is dependent on local environmental conditions, regional patterns of species distribution, and landscape continuity.

Species richness of both native and invasive aquatic plants influenced by environmental conditions and human activity

Botany ◽  
2009 ◽  
Vol 87 (3) ◽  
pp. 306-314 ◽  
Author(s):  
Robert S. Capers ◽  
Roslyn Selsky ◽  
Gregory J. Bugbee ◽  
Jason C. White
Keyword(s):  
Invasive Species ◽  
Species Richness ◽  
Human Activity ◽  
Environmental Conditions ◽  
Native Plants ◽  
Water Clarity ◽  
Phosphorus Concentration ◽  
Lake Area ◽  
Species Dominance ◽  
High Productivity

Invasive plants alter community structure, threatening ecosystem function and biodiversity, but little information is available on whether invasive species richness responds to environmental conditions in the same way that richness of native plants does. We surveyed submerged and floating-leaved plants in 99 Connecticut (northeast USA) lakes and ponds, collecting quantitative data on abundance and frequency. We used multiple linear and logistic regression to determine which environmental conditions were correlated with species richness of invasive and native plants. Independent variables included lake area, maximum depth, pH, alkalinity, conductivity, phosphorus concentration, productivity, and dominance (the proportional abundance of the most abundant and frequently found species), plus two estimates of human activity. Species richness of both native and invasive richness was correlated with alkalinity and human activity. Native richness also increased with water clarity, lake area, and productivity; invasive species richness also rose with pH. We found no evidence that richness of one group affected richness of the other. We also investigated patterns of dominance and found that native plants were as likely to become dominant as invasive species. Dominance occurred overwhelmingly in shallow lakes with high productivity.

Exotic plant invasion and understorey species richness: a comparison of two types of eucalypt woodland in agricultural Western Australia

1998 ◽  
Vol 4 (1) ◽  
pp. 21 ◽  
Author(s):  
Max Abensperg-Traun ◽  
Lyn Atkins ◽  
Richard Hobbs ◽  
Dion Steven
Keyword(s):  
Species Richness ◽  
Exotic Species ◽  
Plant Species ◽  
Plant Invasion ◽  
Native Plants ◽  
Exotic Plants ◽  
Exotic Plant ◽  
Native Plant ◽  
Road Verge ◽  
Exotic Plant Invasion

Exotic plants are a major threat to native plant diversity in Australia yet a generic model of the invasion of Australian ecosystems by exotic species is lacking because invasion levels differ with vegetation/soil type and environmental conditions. This study compared relative differences in exotic species invasion (percent cover, spp. richness) and the species richness of herbaceous native plants in two structurally very similar vegetation types, Gimlet Eucalyptus salubris and Wandoo E. capillosa woodlands in the Western Australian wheatbelt. For each woodland type, plant variables were measured for relatively undisturbed woodlands, woodlands with >30 years of livestock grazing history, and woodlands in road-verges. Grazed and road-verge Gimlet and Wandoo woodlands had significantly higher cover of exotic species, and lower species richness of native plants, compared with undisturbed Gimlet and Wandoo. Exotic plant invasion was significantly greater in Gimlet woodlands for both grazed (mean 78% cover) and road-verge sites (mean 42% cover) than in comparable sites in Wandoo woodlands (grazed sites 25% cover, road-verge sites 19% cover). There was no significant difference in the species richness of exotic plants between Wandoo and Gimlet sites for any of the three situations. Mean site richness of native plants was not significantly different between undisturbed Wandoo and undisturbed Gimlet woodlands. Undisturbed woodlands were significantly richer in plant species than grazed and road-verge woodlands for both woodland types. Grazed and road-verge Wandoo sites were significantly richer in plant species than communities in grazed and road-verge Gimlet. The percent cover of exotics was negatively correlated with total (native) plant species richness for both woodland types (Wandoo r = ?0.70, Gimlet r = ?0.87). Of the total native species recorded in undisturbed Gimlet, 83% and 61% were not recorded in grazed and road-verge Gimlet, respectively. This compared with 40% and 33% for grazed and road-verge Wandoo, respectively. Grazed Wandoo and grazed Gimlet sites had significantly fewer native plant species than did road-verge Wandoo and road-verge Gimlet sites. Ecosystem implications of differential invasions by exotic species, and the effects of grazing (disturbance) and other factors influencing susceptibility to exotic plant invasion (landscape, competition and allelopathy) on native species decline are discussed. Exclusion of livestock and adequate methods of control and prevention of further invasions by exotic plants are essential requirements for the conservation of these woodland systems.

Diversity of desmids in three Thai peat swamps

Biologia ◽  
2008 ◽  
Vol 63 (6) ◽  
Author(s):  
Neti Ngearnpat ◽  
Peter Coesel ◽  
Yuwadee Peerapornpisal
Keyword(s):  
Species Richness ◽  
Environmental Conditions ◽  
New Records ◽  
Rare Taxa ◽  
Peat Swamp ◽  
Physical And Chemical ◽  
Habitat Parameters

AbstractThree peat swamps situated in the southern part of Thailand were investigated for their desmid flora in relation to a number of physical and chemical habitat parameters. Altogether, 99 species were encountered belonging to 22 genera. 30 species are new records for the Thai desmid flora. Laempagarung peat swamp showed the highest diversity (45 species), followed by Maikhao peat swamp (32 species) and Jud peat swamp (25 species). Despite its relatively low species richness, Jud swamp appeared to house a number of rare taxa, e.g., Micrasterias subdenticulata var. ornata, M. suboblonga var. tecta and M. tetraptera var. siamensis which can be considered Indo-Malaysian endemics. Differences in composition of the desmid flora between the three peat swamps are discussed in relation to environmental conditions.

scholarly journals Disturbance alters ecosystem engineering by a canopy-forming alga

2017 ◽  
Vol 98 (4) ◽  
pp. 687-698 ◽  
Author(s):  
Jacqueline B. Pocklington ◽  
Stuart R. Jenkins ◽  
Alecia Bellgrove ◽  
Michael J. Keough ◽  
Tim D. O'Hara ◽  
...  
Keyword(s):  
Species Richness ◽  
Environmental Conditions ◽  
Ascophyllum Nodosum ◽  
Ecosystem Engineering ◽  
Rocky Intertidal ◽  
Coralline Algae ◽  
Littorina Obtusata ◽  
Invertebrate Species ◽  
Light Levels ◽  
Pulse Disturbance

Canopy-forming fucoid algae have an important role as ecosystem engineers on rocky intertidal shores, where they increase the abundance of species otherwise limited by exposure during low tide. The facilitative relationship between Ascophyllum nodosum and associated organisms was explored using a frond breakage experiment (100%, 50%, 25%, 0% intact-frond treatments) in southern England, to assess the consequences of disturbance. Understorey substratum temperature was on average 3°C higher in 0% and 25% intact-frond treatments than in plots with 50% and 100% intact fronds. Light (as PAR during low tide) doubled in 0% intact-frond treatments in comparison to other treatments (which had similar light levels). Mobile invertebrate species richness declined by on average 1 species per m2 in the treatments with only 25% and 0% intact fronds, and the abundance of Littorina obtusata declined by 2.4–4.2 individuals per m2 in the treatments with 25 and 0% intact fronds. Sessile taxa, including Osmundea pinnatifida and encrusting coralline algae, declined by half on average in the 0% intact-frond treatment. These results suggest that the ability of Ascophyllum to mediate environmental conditions to the understorey is the mechanism responsible for species distributed in the understorey (autogenic ecosystem engineering). The results of this study imply that a pulse disturbance resulting in a 50% breakage of Ascophyllum fronds significantly increases temperature and decreases the abundance of mobile invertebrates usually associated with Ascophyllum. Sessile taxa associated with Ascophyllum can, however, withstand disturbances down to 25% intact Ascophyllum fronds.

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