MEPS 588:135-145 (2018)  -  DOI: https://doi.org/10.3354/meps12422

ABSTRACT: The functional approach, using morphology and/or ecological traits, allows grouping of species that play similar roles in an ecosystem. Although species may have unique functions, some may overlap in key morphological traits, leading to similar functions (i.e. functional redundancy). To understand the functional roles of southwestern Atlantic labrids, we analyzed 21 species, focusing on morphological characteristics linked to habitat use, feeding habits and swimming ability, and further taking ontogeny into account by analyzing 3 size categories (small, medium and large) that vary in life history aspects. A comprehensive functional analysis using 11 functional traits defined according to 12 morphological measurements was performed to generate a consensus tree that segregated species into 9 functional groups. Body elongation was the most important characteristic separating parrotfishes from wrasses. Small size class was separated from medium and large size class wrasses and parrotfishes through eye size and eye positioning, respectively. Thalassoma noronhanum was grouped with invertivorous species, despite its classification as a planktivore in previous studies. This species, together with Xyrichtys splendens and Scarus zelindae, showed no size-related shifts in functional role with increasing size. Although recognized as members of different trophic guilds, different size classes of different labrid species may play similar functional roles. This suggests the need for taking size and species identity into account when measuring functional diversity and redundancy in reef ecosystems, key features for maintaining the health and robustness (i.e. resistance/resilience) of reef systems.

KEY WORDS: Functional morphology · Atlantic labrids · Wrasses · Parrotfishes · Ontogeny