Direct and indirect effects of interspecific competition in a highly partitioned guild of reef fishes

Eurich, Jacob G., McCormick, Mark I., and Jones, Geoffrey P. (2018) Direct and indirect effects of interspecific competition in a highly partitioned guild of reef fishes. Ecosphere, 9 (8). e02389.

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Abstract

Competitive interactions and resource partitioning facilitate species coexistence in complex ecosystems. However, while pairwise interactions between ecologically similar species have been well studied, multi‐species competitive networks have received less attention. When interference competition between two species results in partitioning of resources, this may have indirect consequences for other species distributed along the same resource gradient. Here, we tested whether interference competition between two territorial damselfish influenced the fine‐scale species distributions of five other territorial damselfish in Kimbe Bay, Papua New Guinea. These species partition habitat across three reef zones—the flat, crest, and slope, with distinct patterns of distribution within these zones. We predicted the two species with similar distributions and microhabitat use, Pomacentrus adelus and Pomacentrus bankanensis, would display the greatest level of aggression toward one another. This was tested through an intruder experiment where stimulus fish were introduced into a resident's territory, which confirmed disproportionately high levels of interspecific aggression between these two species. We also predicted that the fine‐scale differences in the distribution of each species were maintained through multi‐species interference competition among neighboring species, with further indirect effects on species that did not directly interact. To test this, we conducted a large‐scale (22 × 10 m) experimental removal of the most abundant species, Po. adelus, and quantified the abundance and distribution of all territorial damselfish species for 6 months to a 25 cm resolution. The main direct competitor, Po. bankanensis, exhibited a marked increase in abundance and expanded its distribution (+1.33 m) to acquire the space previously occupied by Po. adelus. This competitive release triggered indirect effects on the distribution of other neighboring species further back on the reef flat, with Chrysiptera unimaculata moving into the zone formerly occupied by Po. bankanensis. This study indicates that the distinct distribution patterns among the reef crest species are linked to levels of interspecific agonistic behavior. We argue that the competitive release following the removal of a superior competitor resulted in both direct and indirect effects, with the immediate neighbor shifting into the newly available space, followed by successive shifts in species responding to the change in the distributions of their immediate neighbors.

Item ID: 55991
Item Type: Article (Research - C1)
ISSN: 2150-8925
Keywords: aggression; agonistic behavior; coral reef; damselfish; distribution gradient; species loss; intruder experiment; multi-species; niche; Papua New Guinea; removal experiment; resource partitioning
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Copyright Information: Copyright © 2018 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Additional Information:

A version of this publication was included as Chapter 4 of the following PhD thesis: Eurich, Jacob G. (2018) Processes underlying the fine-scale partitioning and niche diversification in a guild of coral reef damselfishes. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Research Council Centre of Excellence for Coral Reef Studies (ARC CoE Coral Reef Studies), James Cook University (JCU)
Date Deposited: 31 Oct 2018 04:53
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060202 Community Ecology (excl Invasive Species Ecology) @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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