Comparative trophic morphology in eight species of damselfishes (Pomacentridae)

Abstract

Damselfishes show significant biodiversity in the coral reefs. To better understand such diversity, an ecomorphological approach was investigated in the trophic morphology of eight species of Pomacentridae (Chromis acares, C. margaritifer, Dascyllus aruanus, D. flavicaudus, Pomacentrus pavo, Plectroglyphidodon johnstonianus, Pl. lacrymatus and Stegastes nigricans) belonging to different trophic guilds (zooplankton, algal, coral polyp feeders and omnivores). Geometric morphometrics were used to quantify size and shape variations in four skeletal units: (1) neurocranium, (2) suspensorium and opercle, (3) mandible and (4) premaxilla. This method allowed us to reveal shape and size differences correlated to functional diversity both within and between trophic guilds. Among zooplanktivores, C. margaritifer, D. aruanus and D. flavicaudus have a high and long supraoccipital crest, short mandibles forming a small mouth and high suspensoria and opercles. These three species can be considered to be suction feeders. In the same guild, C. acares shows opposite characteristics (long and thin mandibles, lengthened neurocranium and suspensorium) and can be considered as a ram feeder. Among herbivores and corallivores, the two species of Plectroglyphidodon and S. nigricans can be considered as grazers. Differences in skeletal shape are mainly related to improving the robustness of some skeletal parts (broad hyomandibular, short and high mandibles). The shapes of P. pavo, which feeds largely on algae, strongly differ from that of the other three grazers exhibiting similar morphological characteristics to C. acares (e.g., long and shallow suspensorium, lengthened neurocranium). This highlights likely differences concerning cutting or scraping method. Finally, no strong correlations exist between size and shapes in the eight studied species. Size difference among species having a very similar shape could be viewed as a factor optimizing resource partitioning.

Diversification of the pectoral fin shape in damselfishes (Perciformes, Pomacentridae) of the Eastern Pacific

“…Most ecomorphological studies in Pomacentridae focused on the relationship between cephalic shape and feeding behavior (Gluckmann and Vandewalle 1998;Frédérich et al 2008;Aguilar-Medrano et al 2011;Frédérich and Vandewalle 2011). According to our results, locomotion can be viewed also as an important factor in the adaptive evolution of this group.…”

Morphological and Genetic Divergences in a Coral Reef Damselfish, Pomacentrus coelestis

“…2). All landmarks are described in Frédérich et al (2008) and the various steps taken to reduce measurement errors are detailed in Frédérich and Sheets (2010). For each skeletal unit, all specimens were optimally aligned using a generalized procrustes superimposition (Rohlf and Slice 1990), the grand mean (i.e.…”

“…Geometric morphometric methods are known as a highly powerful tool for detecting shape variation, even very small ones (Adams et al 2004;Zelditch et al 2004). Shape differences among P. coelestis populations are obvious, especially for the mandible (Table 4) but the magnitude of variation is lower than those of inter-specific comparisons (Frédérich et al 2008). Latitude and longitude explain a very low level of shape variance among P. coelestis populations (Table 5); and Mantel and Procrustes tests revealed no correlation between geographical distances and morphological divergences (Table 6).…”

“…Although P. coelestis feeds mainly on planktonic copepods (Kuo and Shao 1991), the shape divergence observed among populations could be explained by diet variation. Previous ecomorphological studies in damselfishes (Gluckmann and Vandewalle 1998;Frédérich et al 2008;Frédérich and Vandewalle 2011) allow interpretations of shape variation of both studied structural units. For example, thinner and proportionally longer mandibles observed in P. coelestis populations from TS, SK and OS could suggest a higher level of planktivory than in the two others.…”

“…However the geographic variation of phenotypic traits, such as morphology or skeletal shapes, was never studied. In addition, the oral jaws (mandible and premaxilla) shape variation was found to have a strong relationship with trophic evolution in damselfishes (Frédérich et al 2008;Cooper and Westneat 2009;Frédérich and Vandewalle 2011). So, rapid morphological divergences in oral jaws among populations might be expected under various trophic factors (e.g.…”