Effects of larger heterospecifics and structural refuge on the survival of a coral reef fish, Thalassoma hardwicke

Abstract

Structural refuge and competition can influence the survival of coral reef fishes; however, the effect of structural refuge on the outcome of competition remains unclear. In Moorea, French Polynesia, surveys were used to quantify habitat association for juvenile Thalassoma hardwicke and 7 sympatric labroid species. Having identified the 3 species most similar to focal T. hardwicke in habitat association, a field assay was used to determine if the presence of larger individuals of these species adversely affected the survival of focal individuals. Finally, a field experiment was used to test how competition with larger residents and structural refuge interact to influence survival of transplanted T. hardwicke. Surveys demonstrated that Gomphosus varius, Pseudocheilinus hexataenia, and T. quinquevittatum were most similar to T. hardwicke in habitat association. In the field assay, the presence of T. quinquevittatum had the greatest negative effect on survival of T. hardwicke. The field experiment revealed that competition with T. quinquevittatum and structural refuge both altered T. hardwicke survival, although their effects were not interactive. Survival of T. hardwicke was 2.3 times greater in treatments without T. quinquevittatum relative to those with T. quinquevittatum, and 2.8 times greater in treatments with structural refuge relative to those without structural refuge. The additive effect may have occurred via the establishment of social dominance hierarchies between transplanted T. hardwicke and resident T. quinquevittatum independently of structural refuge, suggesting that it is important to account for interactions occurring independently of resources when examining resource competition. KEY WORDS: Habitat complexity · Competition · Structural refuge · Reef fish · LabroidResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 407: 197-207, 2010 heterogeneity in the provisioning of structural complexity and refuges (or other habitat features) may drive variability in the strength of competition and predation.Competitive interactions have previously been shown to play a fundamental role in coral reef community dynamics, e.g. between algae and coral (McCook et al. 2001, Jompa & McCook 2003, sponges and coral (Hill 1998, Lopez-Victoria et al. 2006), vermetid gastropods (Gagern et al. 2008) and fishes (Holbrook & Schmitt 2002, Forrester & Steele 2004, Bonin et al. 2009). Coral reefs consist of structurally diverse microhabitats, with the availability of structural refuges within these microhabitats capable of determining the magnitude of competitive interactions. Bonin et al. (2009) demonstrated that the complexity of structural refuges and interspecific competition both influenced early post-settlement survival of a damselfish, with survival in the presence of competitors greatest on intricately-structured habitats. Alternatively, Almany (2004a) found that increasing the complexity of structural refuges increased the abundance of adults in the presence o...

Scaling patterns inform ontogenetic transitions away from cleaning in Thalassoma wrasses

“…We suggest that these reduced suites of mechanical features -low maxillary KT, small gape and low bite force -in Thalassoma wrasses may have evolved as a result of competitive displacement. Thalassoma wrasses co-occur, often in great abundance, in many tropical regions including but not limited to the Indian Ocean, the Indo-Pacific and the Caribbean (Randall et al, 1997;Geange, 2010;Geange et al, 2013;Froese and Pauly, 2014). In fact, field surveys conducted in the Indo-Pacific and Caribbean found that reef crests were typically numerically dominated by members of this clade (Bellwood et al, 2002).…”

A unified analysis of niche overlap incorporating data of different types

“…These species have distinct functional niches; the former over‐associates with Porites rus , Turbinaria ornata and coral rubble (Geange 2010), feeding primarily on algae (Chen 2002). Pseudocheilinus hexataenia over‐associates with the structurally complex hard corals Pocillopora verrucosa and Porites rus (Geange 2010), feeding on copepods, amphipods, gastropods, shrimps and polychaete worms (Harmelin‐Vivien 1979). Conversely, the local realized niches of P. hexataenia and T. hardwicke were most similar.…”

“…Conversely, the local realized niches of P. hexataenia and T. hardwicke were most similar. Like, P. hexataenia , T. hardwicke feeds primarily on small invertebrates (Myers 1999) and over‐associates with Pocillopora verrucosa and Porites rus (Geange 2010).…”

Competitive hierarchies among three species of juvenile coral reef fishes

“…obs.). At our study site, juveniles of all 3 species use similar habitats; all 3 species form strong associations with massive Porites corals and Pocillopora verrucosa (Geange 2010). All 3 species also have similar diets, feeding predominantly on planktonic and benthic crustaceans (Randall 2005).…”

“…Munday et al 2001, Almany 2003, and such interactions may determine the success of newly arrived indi viduals, e.g. if superior competitors ex clude inferior competitors from mutually preferred habitats (Robertson & Gaines 1986, Munday et al 2001, Geange 2010) and increase their exposure to predators (Holbrook & Schmitt 2002). Ultimately, a pattern of negative spatial co-variation between superior and inferior competitors may ensue, with important demographic consequences for subsequent life-history stages.…”