scholarly journals Top predator introduction changes the effects of spatial isolation on freshwater community structure

2019 ◽  
Author(s):  
Rodolfo Mei Pelinson ◽  
Mathew A. Leibold ◽  
Luis Schiesari
Keyword(s):  
Community Structure ◽  
Dispersal Limitation ◽  
Interspecific Variation ◽  
Trophic Levels ◽  
Predatory Fish ◽  
Macroinvertebrate Communities ◽  
Local Conditions ◽  
Freshwater Habitats ◽  
Spatial Isolation ◽  
Predatory Insects

AbstractThe importance of local selective pressures on community structure is predicted to increase with spatial isolation when species favored by local conditions also have higher dispersal rates. In freshwater habitats, the introduction of predatory fish can produce trophic cascades because fish tend to prey upon intermediate predatory taxa, such as predatory insects, which indirectly benefits herbivores and detritivores. Similarly, spatial isolation is known to limit predatory insect's colonization rates more strongly than of herbivores and detritivores, thus generating similar effects. Here we tested the hypothesis that the effect of introduced predatory fish on macroinvertebrate community structure increases across a gradient of spatial isolation by conducting a field experiment where artificial ponds with and without fish (the Redbreast Tilapia) were constructed at three different distances from a source wetland. Overall results show that fish do reduce the abundance of predatory insects but have no effect on the abundance of herbivores and detritivores. Spatial isolation, however, does strengthen the trophic cascade caused by dispersal limitation of predatory insects, but only in the absence of fish. More importantly, macroinvertebrate communities with and without fish tend to diverge more strongly at higher spatial isolation, however, this pattern was not due to an increase in the magnitude of the effect of fish, as initially hypothesized, but to a change in the effect of isolation in the presence of fish. We argue that as spatial isolation increases, suitable prey, such as predatory insects become scarce and fish increases predation pressure upon herbivores and detritivores, dampening the positive effect of spatial isolation on them. Our results highlight the importance of considering interspecific variation in dispersal and multiple trophic levels to better understand the processes generating metacommunity structures.

scholarly journals Spatial community variability: Interactive effects of predators and isolation on stochastic community assembly

2020 ◽  
Author(s):  
Rodolfo Mei Pelinson ◽  
Mathew A. Leibold ◽  
Luis Schiesari
Keyword(s):  
Isolation By Distance ◽  
Dispersal Limitation ◽  
Priority Effects ◽  
Predatory Fish ◽  
Historical Contingency ◽  
Demographic Stochasticity ◽  
Community Size ◽  
Positive Effects ◽  
Community Variability ◽  
Predatory Insects

ABSTRACTIn the absence of environmental heterogeneity, spatial variation among local communities can be mostly attributed to demographic stochasticity (i.e., ecological drift) and historical contingency in colonization (i.e. random dispersal and priority effects). The consequences of demographic stochasticity are highly dependent on community size, gamma, and alpha diversity, which, along with historical contingency, can be strongly affected by dispersal limitation and the presence of predators. We used freshwater insect communities to experimentally test whether and how the presence of a generalist predatory fish and dispersal limitation (i.e., isolation by distance from a source habitat) can change the relative importance of stochastic and non-stochastic processes on community variability. We found that dispersal limitation can have both negative and positive effects on community variability, and their importance may depend on the presence of predatory fish. Negative effects happened because predatory insects cannot always successfully colonize highly isolated ponds, causing herbivores and detritivores to increase in abundance. As a consequence, community size increases, decreasing the importance of demographic stochasticity on community structure. However, when fish is absent, these effects are counterbalanced by an increase in the importance of priority effects generating more distinct communities in more isolated ponds. Such effects can be caused by either pre or post-colonization mechanisms and were absent in the presence of fish predators, likely because fish prevented both predatory and non-predatory insects from becoming more abundant, irrespective of their order of colonization.

scholarly journals Impacts of agrochemical intensification on the assembly and reassembly of a mainland-island model metacommunity

2021 ◽  
Author(s):  
Rodolfo Mei Pelinson ◽  
Bianca Rodrigues Strecht ◽  
Erika Mayumi Shimabukuro ◽  
Luis Cesar Schiesari
Keyword(s):  
Community Structure ◽  
Rainy Season ◽  
Isolation By Distance ◽  
Single Pulse ◽  
Temporary Pond ◽  
Species Dispersal ◽  
Crop Fields ◽  
Predatory Insect ◽  
Spatial Isolation ◽  
Predatory Insects

ABSTRACTMany lentic aquatic environments are found embedded in agricultural fields, forming complex metacommunity structures. These habitats are vulnerable to contamination by agrochemicals, which can differentially affect local communities depending on the intensity and variability of species dispersal rates. We conducted a field experiment to assess how agrochemical intensification simulating the conversion of savannas into managed pastures and sugarcane fields affects freshwater community structure at different levels of spatial isolation. We constructed forty-five 1,200-L artificial ponds in a savanna landscape at three distances from a source wetland (30 m, 120 m, and 480 m). Ponds were spontaneously colonized by aquatic insects and amphibians and treated with no agrochemicals (‘savanna’ treatment), fertilizers (‘pasture’ treatment), or fertilizers and a single pulse of the insecticide fipronil and the herbicide 2,4-D (‘sugar cane’ treatment) following realistic dosages and application schedules. The experiment encompassed the entire rainy season. ‘Pasture’ communities were only slightly different from controls largely because two predatory insect taxa were more abundant in ‘pasture’ ponds. ‘Sugarcane’ communities strongly diverged from other treatments after the insecticide application, when a decrease in insect abundance indirectly benefitted amphibian populations. However, this effect had nearly disappeared by the end of the rainy season. The herbicide pulse had no effect on community structure. Spatial isolation changed community structure by increasing the abundance of non-predatory insects. However, it did not affect all predatory insects nor, surprisingly, amphibians. Therefore, spatial isolation did not change the effects of agrochemicals on community structure. Because agrochemical application frequently overlaps with the rainy season in many monocultures, it can strongly affect temporary pond communities. Ponds embedded in pastures might suffer mild consequences of fertilization by favoring the abundance of few predators through bottom-up effects. Ponds in sugarcane fields, however, might experience a decline in the insect population, followed by an increase in the abundance of amphibians tolerant to environmental degradation. Furthermore, we found no evidence that isolation by distance can change the general effects of chemical intensification, but future experiments should consider using real crop fields as the terrestrial matrix since they can represent different dispersal barriers.

scholarly journals Top predator introduction changes the effects of spatial isolation on freshwater community structure

Ecology ◽  
2021 ◽  
Author(s):  
Rodolfo Mei Pelinson ◽  
Mathew A. Leibold ◽  
Luis Schiesari
Keyword(s):  
Community Structure ◽  
Top Predator ◽  
Spatial Isolation ◽  
Freshwater Community Structure ◽  
Freshwater Community

scholarly journals Changes in tree community structure in defaunated forests are not driven only by dispersal limitation

2020 ◽  
Vol 10 (7) ◽  
pp. 3392-3401
Author(s):  
Kirstie Hazelwood ◽  
C. E. Timothy Paine ◽  
Fernando H. Cornejo Valverde ◽  
Elizabeth G. Pringle ◽  
Harald Beck ◽  
...  
Keyword(s):  
Community Structure ◽  
Dispersal Limitation ◽  
Tree Community

scholarly journals Assessing macroinvertebrate communities in relation to environmental variables: the case of Sambandou wetlands, Vhembe Biosphere Reserve

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Tatenda Dalu ◽  
Rivoningo Chauke
Keyword(s):  
Community Structure ◽  
Water Depth ◽  
Environmental Variables ◽  
Anthropogenic Activities ◽  
Biosphere Reserve ◽  
High Water ◽  
Macroinvertebrate Community ◽  
Macroinvertebrate Communities ◽  
Negative Effect ◽  
Macrophyte Cover

AbstractThe Vhembe Biosphere Reserve, South Africa, contains many wetlands that serve as wildlife habitats and provide vital ecosystem services. Some of the wetlands are continuously being degraded or destroyed by anthropogenic activities causing them to disappear at an alarming rate. Benthic macroinvertebrates are known as good water quality bioindicators and are used to assess aquatic ecosystem health. The current study investigated habitat quality using macroinvertebrate community structure and other biotic variables (i.e. phytoplankton, macrophytes) in relation to environmental variables in the Sambandou wetlands using canonical correspondence analysis (CCA). A total of fifteen macroinvertebrate families were identified over two seasons. The CCA highlighted seven variables, i.e. pH, phosphate concentration, temperature, ammonium, macrophyte cover, conductivity and water depth, which were significant in structuring macroinvertebrate community. Picophytoplankton and microphytoplankton concentrations decreased from winter to summer, whereas nanophytoplankton concentration increased from winter to summer. Thus, the dominance of small-sized phytoplankton indicated nutrient limitation and decreased productivity, whereas winter sites 2 and 3 were dominated by large-celled phytoplankton, highlighting increased productivity. Winter sites were mostly negatively associated with CCA axis 1 and were characterised by high temperature, phosphate and ammonium concentrations, macrophyte cover, pH and conductivity. Summer sites were positively associated with axis 1, being characterised by high water depth and pH levels. The results obtained highlighted that agricultural activities such as cattle grazing and crop farming and sand mining/poaching had a negative effect on macroinvertebrate community structure.

scholarly journals Nonrandom variation in Poecilia marcellinoi n. sp. and P. salvatoris Regan, 1907 in El Salvador (Pisces, Poeciliidae)

1995 ◽  
Vol 64 (4) ◽  
pp. 239-252 ◽  
Author(s):  
Fred. N. Poeser
Keyword(s):  
New Species ◽  
El Salvador ◽  
Character Displacement ◽  
Interspecific Variation ◽  
Ecological Stress ◽  
Freshwater Habitats ◽  
High Degree ◽  
A New Species ◽  
Meristic Data

A new species of the genus Poecilia Bloch & Schneider, 1801 is recorded from El Salvador. Morphological and meristic data of P. marcellinoi n. sp. and of the sympatric P. salvatoris Regan, 1907 are analysed. Intra- and interspecific variation are compared and correlated with environmental and interspecific influences. A high degree of character displacement is observed in populations from stable freshwater habitats. In habitats with presumed marine influences, this character displacement is counteracted by ecological stress. Based on the evidence presented, subspecific separation of observed ecotypes from literature is rejected.

scholarly journals Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

2014 ◽  
Vol 281 (1797) ◽  
pp. 20142103 ◽  
Author(s):  
Marlee A. Tucker ◽  
Tracey L. Rogers
Keyword(s):  
Community Structure ◽  
Body Size ◽  
Body Mass ◽  
Marine Environment ◽  
Trophic Level ◽  
Marine Mammals ◽  
Trophic Position ◽  
Trophic Levels ◽  
Predator Prey ◽  
Terrestrial Mammals

Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial ( n = 51) and marine ( n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities.

scholarly journals A Perspective on Body Size and Abundance Relationships across Ecological Communities

Biology ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 42
Author(s):  
Vojsava Gjoni ◽  
Douglas Stewart Glazier
Keyword(s):  
Body Size ◽  
Ecological Factors ◽  
Trophic Levels ◽  
Marine Phytoplankton ◽  
Published Data ◽  
Scaling Exponent ◽  
Ecological Communities ◽  
Macroinvertebrate Communities ◽  
Power Functions ◽  
Phytoplankton Communities

Recently, several studies have reported relationships between the abundance of organisms in an ecological community and their mean body size (called cross-community scaling relationships: CCSRs) that can be described by simple power functions. A primary focus of these studies has been on the scaling exponent (slope) and whether it approximates −3/4, as predicted by Damuth’s rule and the metabolic theory in ecology. However, some CCSR studies have reported scaling exponents significantly different from the theoretical value of −3/4. Why this variation occurs is still largely unknown. The purpose of our commentary is to show the value of examining both the slopes and elevations of CCSRs and how various ecological factors may affect them. As a heuristic exercise, we reanalyzed three published data sets based on phytoplankton, rodent, and macroinvertebrate assemblages that we subdivided according to three distinctly different ecological factors (i.e., climate zone, season, and trophic level). Our analyses reveal significant variation in either or both the CCSR slopes and elevations for marine phytoplankton communities across climate zones, a desert rodent community across seasons, and saltwater lagoon macroinvertebrate communities across trophic levels. We conclude that achieving a comprehensive understanding of abundance-size relationships at the community level will require consideration of both slopes and elevations of these relationships and their possible variation in different ecological contexts.

scholarly journals Challenges, tactics and integrated management of emerald ash borer in North America

2019 ◽  
Author(s):  
Deborah G McCullough
Keyword(s):  
North America ◽  
Integrated Management ◽  
Management Strategies ◽  
Emerald Ash Borer ◽  
Interspecific Variation ◽  
Agrilus Planipennis ◽  
Local Conditions ◽  
Ash Trees ◽  
Invasion Impacts ◽  
Individual Trees

Abstract Emerald ash borer (EAB) (Agrilus planipennis Fairmaire), discovered in southeastern Michigan, USA in 2002, has become the most destructive and costly invasive forest insect in North America. This phloem-boring beetle has also invaded Moscow, Russia and continued spread of EAB potentially threatens European ash (Fraxinus spp.) species. This review summarizes EAB life history, including interspecific variation in host preference, invasion impacts and challenges of detecting new infestations and provides an overview of available management tactics. Advances in systemic insecticides, particularly emamectin benzoate products applied via trunk injection, have yielded effective and practical options both to protect individual trees and to slow EAB population growth and ash decline on an area-wide basis without disrupting natural enemies. Economic costs of treating ash are substantially lower than removal costs, retain ecosystem services provided by the trees, reduce sociocultural impacts and conserve genetic diversity in areas invaded by EAB. Girdled ash trees are highly attractive to EAB adults in low-density populations and debarking small girdled trees to locate larval galleries is the most effective EAB detection method. An array of woodpeckers, native larval parasitoids and introduced parasitoids attack EAB life stages but mortality is highly variable. Area-wide management strategies that integrate insecticide-treated trees, girdled ash trap trees and biological control can be adapted for local conditions to slow and reduce EAB impacts.

Macroinvertebrate Communities and Environment in a Southern African Mountain Stream

1988 ◽  
Vol 45 (12) ◽  
pp. 2168-2181 ◽  
Author(s):  
J. M. King ◽  
J. A. Day ◽  
P. R. Hurly ◽  
M-P. Henshall-Howard ◽  
B. R. Davies
Keyword(s):  
Community Structure ◽  
Environmental Variables ◽  
Mediterranean Ecosystems ◽  
Mountain Stream ◽  
Functional Feeding Groups ◽  
Stepwise Discriminant Analysis ◽  
Macroinvertebrate Communities ◽  
Strong Correlations ◽  
Stream Community ◽  
Community Changes

In a study of a second-order southern African stream, complementary classification and multidimensional scaling (MDS) techniques revealed longitudinal changes in macroinvertebrate community structure, but no temporal changes. Stepwise discriminant analysis and multiple linear regression were used to identify environmental variables correlated with the community changes but produced conflicting results depending on the information used, possibly because of strong correlations between some of the variables. The MDS plot of biotic samples illustrated that potassium levels correlated most strongly with community distribution. Because of the large number of variables now shown worldwide to correlate with faunal distributions, we suggest ways to choose the variables to suit the kind of study to be undertaken. Attempts to assign the invertebrates to functional feeding groups (FFGs) were unsatisfactory as the relevant categories are poorly defined and often inadequate for classifying the fauna. We suggest that until these categories are more clearly defined, and more uniformly applied, concepts relating to FFGs cannot be tested satisfactorily. The stream community in Langrivier is more similar to communities found in two other mediterranean ecosystems than to those in other southern African rivers, probably because of the greater predictability of flow in the former.

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