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

Author(s)

Pelinson, Rodolfo Mei ^[1] ; Leibold, Mathew A. ^[2] ; Schiesari, Luis ^{[1, 3]}

Affiliation

^[1] Univ Sao Paulo, Inst Biociencias, Programa Posgrad Ecol, Sao Paulo, SP - Brazil

^[2] Univ Florida, Dept Biol, Gainesville, FL 32611 - USA

^[3] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: ECOLOGY; v. 102, n. 11 SEP 2021.
• Web of Science Citations: 0

Abstract

Current conceptual metacommunity models predict that the consequences of local selective pressures on community structure increase with spatial isolation when species favored by local conditions also have higher dispersal rates. This appears to be the case of freshwater insects in the presence of fish. The introduction of predatory fish can produce trophic cascades in freshwater habitats because fish tend to prey upon intermediate predatory taxa, such as predatory insects, indirectly benefiting herbivores and detritivores. Similarly, spatial isolation can limit dispersal and colonization rates of predatory insects more strongly than of herbivores and detritivores, thus generating similar cascading effects. Here we tested the hypothesis that the effect of introduced predatory fish on insect community structure increases with spatial isolation by conducting a field experiment in artificial ponds that manipulated the presence/absence of fish (the redbreast tilapia) at three different distances from a source wetland. Our results showed that fish have direct negative effects on the abundance of predatory insects but probably have variable net effects on the abundance of herbivores and detritivores because the direct negative effects of predation by fish may offset indirect positive ones. Spatial isolation also resulted in indirect positive effects on the abundance of herbivores and detritivores but this effect was stronger in the absence rather than in the presence of fish so that insect communities diverged more strongly between fish and fishless ponds at higher spatial isolation. We argue that an important additional mechanism, ignored in our initial hypothesis, was that as spatial isolation increases fish predation pressure upon herbivores and detritivores increases due to the relative scarcity of predatory insects, thus dampening the positive effect that spatial isolation confers to lower trophic levels. Our results highlight the importance of considering interspecific variation in dispersal and multiple trophic levels to better understand the processes generating community and metacommunity patterns. (AU)

• FAPESP's process: 14/16320-7 - Impacts of climate/environmental change on the fauna: an integrative approach
• Grantee: Carlos Arturo Navas Iannini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 18/07714-2 - Effects of land use intensification on freshwater community similarity and beta diversity
• Grantee: Rodolfo Mei Pelinson
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 15/18790-3 - Environmental effects of the pasture-sugarcane conversion and pasture intensification
• Grantee: Luiz Antonio Martinelli
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 17/04122-4 - Effects of local processes and spatial isolation on aquatic community assembly: a simulation of land use intensification
• Grantee: Rodolfo Mei Pelinson
• Support Opportunities: Scholarships in Brazil - Doctorate