Biology subjects

Pelinson, R. M.

Publications and source records attributed to Pelinson, R. M..

3 recordsLinked to original sources

bioRxiv2021

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

Many 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.

ecology↗

bioRxiv2020

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

In 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.

ecology↗

bioRxiv2019

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

The 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.

ecology↗