The macroecology of reef fish agonistic behaviour

Abstract

Understanding the interplay between processes operating at large and small spatiotemporal scales in shaping biotic interactions remains challenging. Recent studies illustrate how phenotypic specialization, species life‐history traits and/or resource partitioning recurrently underlie the structure of mutualistic interactions in terrestrial ecosystems along large latitudinal gradients of biodiversity. However, we know considerably less about how local processes interact with large‐scale patterns of biodiversity in modulating biotic interactions in the marine realm. Considering agonistic behaviour as a proxy for contest competition, we empirically investigate whether the structure of reef fish agonistic interactions is conserved across a 34 000‐km longitudinal gradient of biodiversity. By sampling coral reefs using standardized remote underwater video, we found recurrent patterns of fish agonistic behaviour in disparate communities distributed across five biogeographic provinces of the Pacific and Atlantic oceans. While the sheer number of species increases with regional richness, the number of aggressive disputes at the habitat scale is similar across communities. We then combined generalized linear models and network theory to reveal that, the emergent structure of local agonistic networks is not modular but instead recurrently display a nested structure, with a core of highly interactive site‐attached herbivores of the Pomacentridae family. Therefore, despite the increase in the number of species involved in agonistic interactions toward speciose communities, the network structure is conserved along the longitudinal richness gradient because local disputes are mostly driven by closely‐related, functionally‐similar species. These findings suggest that evolutionary and local processes interact in modulating reef fish agonistic behaviour and that fine‐scale niche‐partitioning can structure the ecological networks in marine ecosystems.

Reef microhabitats mediate fish feeding intensity and agonistic interactions at Príncipe Island Biosphere Reserve, Tropical Eastern Atlantic

“…The territorial herbivore St. imbricatus is central in the agonistic networks in EAM, sand/rock and coral microhabitats (Figure 3b). Fishes from the genus Stegastes are key species for structuring agonistic interactions in coral reefs (Fontoura et al., 2020), and display intra and interspecific aggressiveness towards other fishes by defending their “algal gardens”, especially from other herbivores (Lassuy, 1980). These territories are highly productive and have greater algal biomass and diversity than adjacent areas, features that makes worth spending energy on defending them (Hinds & Ballantine, 1987; Sammarco, 1983).…”

“…(2018). We focused on individuals larger than 5 cm in total length, because identification of smaller individuals in RUVs can be unprecise (Fontoura et al., 2020; Longo & Floeter, 2012).…”

“…Each fish recorded biting the substrate or performing agonistic interactions inside the 2 m 2 area was identified, had its total length (cm) visually estimated and assigned to a trophic guild, according to Mouillot et al (2014) and Maia et al (2018). We focused on individuals larger than 5 cm in total length, because identification of smaller individuals in RUVs can be unprecise (Fontoura et al, 2020;Longo & Floeter, 2012).…”

Agonistic Behavior Is Affected by Memory in the Dusky Damselfish Stegastes fuscus

“…This phenomenon has been confirmed in territorial fish by the lower number of displays (Earley et al, 2003 ; Sogawa et al, 2016 ; Silveira et al, 2020 ) and changes in the use of space (Frostman and Sherman, 2004 ; Saeki et al, 2018 ) between neighbors. As a consequence, these agonistic interactions may have community-level impacts (Fontoura et al, 2020 ), and could provide useful information for the individual’s recognition process (Miklósi et al, 1992 ).…”

“…Most defend their territories against co- and heterospecific intruders (Taylor and Francis, 2016 ), and may respond differently to confrontations involving familiar and unfamiliar individuals (Thresher, 1979 ; Silveira et al, 2020 ). According to a recent study that empirically investigated the agonistic interactions of reef fish, damselfish are one of the most important groups responsible for establishing coral reef communities (Fontoura et al, 2020 ). While most of our knowledge of reef fish ecology is based on damselfish, their learning and memory processes are poorly understood.…”