Trophic Specializations of Damselfishes Are Tightly Associated with Reef Habitats and Social Behaviours
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Mar Biol (2016) 163:249 DOI 10.1007/s00227-016-3020-x ORIGINAL PAPER Trophic specializations of damselfishes are tightly associated with reef habitats and social behaviours Laura Gajdzik1 · Eric Parmentier1 · Nicolas Sturaro2 · Bruno Frédérich1,2 Received: 19 August 2016 / Accepted: 19 October 2016 © Springer-Verlag Berlin Heidelberg 2016 Abstract Despite the increasing need to understand fac- the stomach content and the habitat–behaviour characters. tors shaping community assembly, few studies have However, the isotopic trait is evolutionarily more labile simultaneously explored the influence of niche-based and probably because it thoroughly depicts the ecological niche phylogenetic processes. Here, we investigate the relation- of species. To summarize, pelagic feeders (mainly from the ships between diet, habitat and social behaviour in dam- Chrominae) usually form shoals in areas close to the open selfishes (Pomacentridae) collected in 2014 at Moorea ocean at a maximum depth of 20 m. Benthic feeders (well Island (17°30′S, 149°50′W), French Polynesia. Isotope represented in the Stegastinae) are ubiquitous, solitary ratios of carbon and nitrogen, in association with stomach and mostly territorial species found at various depths. The contents, delineate three trophic groups: pelagic feeders intermediate group includes gregarious species from three consuming zooplankton, benthic feeders mainly grazing subfamilies that forage in the lagoon usually above 12 m on algae and an intermediate group feeding on prey from depth. Overall, we give insight into processes that have the whole bentho-pelagic compartment. Sulphur isotope structured the damselfish community in Moorea. ratios indicate segregation between species of the outer reef mostly depending on oceanic input of zooplankton and the lagoonal species relying on locally produced resources or Introduction even on terrestrial supply. We demonstrate a tight associa- tion between dietary specializations, habitat characteristics Coral reefs are highly productive and structurally complex and social behaviours, and these correlations are further environments that have promoted diversification of marine confirmed by integrating the phylogeny of Pomacentridae. teleost fishes (Alfaro et al. 2007; Price et al. 2011). Indeed, We also provide evidence of phylogenetic conservatism for they house a wide array of fishes where niche partitioning may be viewed as one of the key factors in the course of their diversification. These resulting high levels of eco- Responsible Editor: K.D. Clements. logical diversity have allowed the stable co-occurrence Reviewed by Undisclosed experts. of similar species (Schoener 1974; Colwell and Fuentes 1975). Within that context, unravelling the multiplicity of Electronic supplementary material The online version of this factors acting upon the fish community represents a key article (doi:10.1007/s00227-016-3020-x) contains supplementary challenge to be tackled. Community assembly is governed material, which is available to authorized users. by niche-based processes (including habitat filtering and * Laura Gajdzik competitive exclusion) and by the phylogenetic related- [email protected] ness among organisms (Cavender-Bares et al. 2009; Ndir- ibe et al. 2013). Nowadays, the use of phylogenetic infor- 1 Laboratory of Functional and Evolutionary Morphology, AFFISH Research Center, University of Liège, B6C, Sart mation has become more widespread in ecological studies Tilman, 4000 Liège, Belgium focusing on the structure of organisms (Losos et al. 2003) 2 Laboratory of Oceanology, MARE Centre, University because it gives valuable insight into the pattern of phylo- of Liège, B6C, Sart Tilman, 4000 Liège, Belgium genetic niche conservatism (PNC). This pattern is defined 1 3 249 Page 2 of 15 Mar Biol (2016) 163:249 as the tendency of lineages to retain their niche-related ecosystems. Interestingly, damselfishes show a great diver- traits through speciation events and over macroevolutionary sity of habitats (Ormond et al. 1996; Lecchini and Galzin time (Crisp and Cook 2012), with a corollary that closely 2005) and various social behaviours (Fishelson 1998). related species exhibit higher ecological similarities than Furthermore, recent studies have established a firm phylo- expected based on their phylogenetic relationships (Webb genetic framework for their radiation (Cooper et al. 2009; et al. 2002; Losos 2008). Cooper and Santini 2016) and revealed that damselfishes Niche-based processes include the study of feeding ecol- have iteratively evolved along three main feeding strate- ogy of species and populations, which is usually evaluated gies, i.e. pelagic feeders, benthic foragers and an interme- with two methods. (1) Stomach content analysis is widely diate group (Cooper and Westneat 2009; Frédérich et al. recognized as a standard technique to determine the diet 2013, 2016a, b). Several field observations also suggested but only displays the most recent meal (Hyslop 1980). (2) a strong link between diet, habitat use and social behaviour Stable isotope ratios of carbon (C13/C12, hereafter noted as in Pomacentridae (Emery 1973; Frédérich et al. 2009), but δ13C) and nitrogen (N15/N14, noted as δ15N) are a classical they only constitute a qualitative assumption. The analysis approach in trophic ecology, allowing time-integrated stud- of quantitative data is therefore needed to formally estab- ies of animal diet or niche assessment (Post 2002; Newsome lish these correlations. et al. 2007). More recently, the stable isotope ratio of sul- The aim of the present study is to examine the congru- phur (S34/S32 or δ34S) has been used as an additional tracer ence between diet, habitat and social behaviour in damself- of food sources (McCutchan et al. 2003; Connolly et al. ishes (Pomacentridae) from coral reefs at Moorea Island, 2004; Moreno et al. 2010). The high variation in δ34S val- French Polynesia. We first explore the niche partitioning of ues between seawater (~22.9‰) and sediments (~1‰) helps Pomacentridae through an approach combining three sta- to discriminate the origins of prey and locations of feeding ble isotope ratios (δ15N, δ13C and δ34S) and the analysis of grounds within the marine environment (Kharlamenko et al. stomach contents. Then, we describe the habitat and social 2001; Fry et al. 2008; Mittermayr et al. 2014). Even though behaviour of each species. We investigate whether there is a δ34S is extremely helpful to disentangle trophic interactions correlation between dietary and habitat–behaviour charac- among organisms, no study has integrated this element to teristics at the present time. We further explore the relation- investigate the ecology of coral reef fishes. Other informa- ships between these ecological traits across the phylogeny tion regarding habitat preferences and social behaviours, of Pomacentridae and test whether these traits show a phy- needed to appraise all aspects of ecological niches, are com- logenetic signal. Overall, our data provide a better under- monly collected by visual observations (e.g. Lecchini and standing of the processes ruling the damselfish community Galzin 2005). assembly and the causes of its structure. Many studies in diverse taxa (e.g. insular terrestrial organisms and marine invertebrates) used the historic rela- tionships among species to evaluate PNC patterns of vari- Materials and methods ous ecological traits (e.g. Knouft et al. 2006; Roy et al. 2009; Cooper et al. 2011). The study of phylogenetic Sampling and collection of ecological data signal constitutes one method to detect PNC and greatly varies among traits (Blomberg et al. 2003; Losos 2008). The sampling campaign was carried out from April to July The niche-complementarity hypothesis predicts that spe- 2014 in Moorea, an island located in the South Pacific cies similar along one dimension of the niche must differ (17°30′S, 149°50′W; French Polynesia). The lagoon in along other axes to support their coexistence (Schoener Moorea comprises coral patches found in between sand 1974). However, in some clades, there is not always tan- banks and a fringing reef shaped as a wall. The barrier gible evidence sustaining that prediction because interac- reef includes the outer reef slope and the reef crest and is tions among species may be responsible for a non-random hereafter referred as the outer reef. Sampling occurred at distribution of species within the ecological space. Conse- Opunohu Bay located on the north side of Moorea but also quently, distantly related species might share more in com- in front of Haapiti in south-west part of the island (Fig. 1; mon than closely related ones (Losos et al. 2003). To date, Table 1). Damselfishes—belonging to four subfamilies there is an overall scarcity of documented cases investigat- and 17 species—were either caught with a speargun or by ing the interactions between feeding strategy, habitat and the use of clove oil across the whole reef at Opunohu Bay behaviour when taking into account phylogenetic informa- (Table 1). Four species (Chromis iomelas, Chromis mar- tion, especially in coral reef fishes. garitifer, Dascyllus flavicaudus and Dascyllus trimacula- The Pomacentridae family (damselfishes), which groups tus) were ubiquitous with individuals foraging in the two 399 species (Eschmeyer et al. 2016), represents a suitable main reef zones (the lagoon and the outer reef), which were system to investigate factors shaping the community in reef treated separately during statistical analyses. Furthermore, 1 3