Ecomorphology, trophic niche, and distribution divergences of two common damselfishes in the Gulf of California

Abstract

Damselfishes of the genus Stegastes are among the most conspicuous benthic reefassociated fish in the Gulf of California, and the two most commonly found species are the Beaubrummel Gregory Stegastes flavilatus and the Cortez damselfish Stegastes rectifraenum. Both species are described as ecologically and morphologically very similar. However, the niche theory predicts that coexisting species will tend to minimize competition through niche partitioning. We, therefore, investigated the degree of their ecological similarity through their morphology, trophic ecology, and spatial distribution, as well as, the effects of environmental variables on their abundance. We showed that S. rectifraenum is highly abundant in the entire Gulf of California while S. flavilatus is only found in the central and southern part. The abundance of S. rectifraenum was higher in shallow water and decreased when the cover of macroalgae and sand increased. No environmental variable was related to the abundance of S. flavilatus. Both species had distinct isotopic niches: S. flavilatus fed almost exclusively on plankton and zoobenthos, while S. rectifraenum had an omnivorous diet mixing turf, zoobenthos and plankton. The diet divergence was reflected in the morphology of the two species. Stegastes flavilatus had a more rounded body shape, with a higher supraoccipital crest and more gill rakers than S. rectifraenum, which may increase its ability to feed on vagile invertebrates and zooplankton. Our results support the hypothesis that a niche partition has occurred between the two species. Furthermore, the importance of planktonic food sources to both species, considered as benthic territorial feeders, challenges the traditional ecological description of the Stegastes species.

Cadmium, Lead, Copper, Zinc, and Iron Concentration Patterns in Three Marine Fish Species from Two Different Mining Sites inside the Gulf of California, Mexico

“…Zinc was the only metal with a higher concentration in B. polylepis than in K. vaigiensis, which is contrary to the findings reported in other trophic webs where carnivorous fish have shown lower zinc contents [72]. The omnivorous species S. rectifraenum [24] showed significantly higher cadmium and lead levels than K. vaigiensis, whereas copper and zinc concentrations were significantly higher in K. vaigiensis. The amount of a given metal accumulated in an aquatic organism depends on the particular element and the species involved and may vary across species according to the particular ecological niche, swimming behavior, and metabolic activity of each [77].…”

“…Studies on the diet of K. vaigiensis confirm that this species is a functional herbivore that feeds primarily on macroalgae, including phaeophytes, chlorophytes, and rhodophytes, and almost no animal material [17,18] as other herbivorous species of Kyphosus, such as K. bigibbus, K. cinerascens, K. sydneyanus, K. azureus, and K. elegans (the latter two also from the Gulf of California) [17,[19][20][21]. S. rectifraenum (family Pomacentridae) was first described as an herbivore [22], but later studies have reported an omnivorous diet consisting of turf, zoobenthos, and plankton [23,24]. B. polylepis (Balistidae) has been classified as predominantly carnivorous, although some algae are consumed occasionally as incidental food [25,26].…”

Caracterización y clasificación del fondo en el arrecife rocoso La Sorpresa (Baja California Sur, México) implementando métodos de interpolación espacial.

“…Estas áreas protegidas de la energía del oleaje y de alta heterogeneidad, propician un incremento en la disponibilidad de refugio y permite a los individuos encontrar alimento, ocultarse de su depredador y al mismo tiempo puede proveer de superficie para la reproducción (Meléndez, 2014). Se ha encontrado una correlación positiva entre las características del medio donde se presentan las rocas y corales con la especie Stegastes rectifaenum (Olivier et al 2019), posiblemente contrastada con las funciones antes descrita. Las macroalgas son el componente biótico más extendido superficialmente que cubre aproximadamente el 60% del área de estudio y constituyen microhábitats específicos para especies principalmente herbívoras.…”

Functional niches of cleanerfish species are mediated by habitat use, cleaning intensity and client selectivity

“…However, with the refinement of investigations into dietary differences (Casey et al., 2019; Clements et al., 2017; Leray et al., 2019; Longenecker, 2007), evidence for dietary resource partitioning has now accumulated for several groups such as herbivores (e.g. Adam et al., 2015; Kelly et al., 2016; Nicholson & Clements, 2020; Olivier et al., 2019), different sized predators (e.g. Frisch et al., 2016; Matley et al., 2016) and cryptobenthic fishes (Andrades et al., 2019; Brandl et al., 2020; Hernaman et al., 2009; Hundt et al., 2017).…”