Objectively measuring subjectively described traits: geographic variation in body shape and caudal coloration pattern within Vieja melanura (Teleostei: Cichlidae)

Abstract

Vieja melanura is a Neotropical cichlid occurring in the Petén-lake district systems of Guatemala, as well as the Río Grijalva-Usumacinta basin, and other systems in Southern México, Belize, and Guatemala. A caudal stripe, extending forward from the caudal peduncle, is characteristic of this species. This stripe is sloped downward in nearly all individuals of V. melanura, but the degree of the slope is highly variable throughout its range. The slope and shape of the stripe has previously been used in diagnosing and differentiating between species of Vieja. The purpose of this study was to use objective methods to investigate morphological variation in the caudal stripe and body shape throughout the range of V. melanura. We studied geometric morphometric analyses of body shape and empirical measurements of the slope of the caudal stripe in 215 specimens of V. melanura. We also used the mitochondrial cytochrome b marker to study population level patterns within V. melanura. Results from our analyses showed significant geographic variation in body shape and patterns of coloration with little mitochondrial phylogeographic structure. These patterns likely correspond to differences in riverine habitats throughout the species’ distribution. In conclusion, these results can be used to inform other studies of color and shape variation as it applies to taxonomy and systematics.

Scale(s) matter: Deconstructing an area of endemism for Middle American freshwater fishes

“…Two species of cichlids (V. melanura and P. splendida) and one species of poeciliid (X. hellerii) lack phylogeographical structure within the G-U AoE. These results are congruent with other findings for cichlids and poeciliids in the region (Alda, Reina, Doadrio, & Bermingham, 2013;Harrison et al, 2014;McMahan, Geheber, & Piller, 2010;McMahan, Kutz, et al, 2017). In contrast, two species of poeciliids (B. belizanus in aridity in the region and a reduced amount of surface water availability (Anselmetti et al, 2006;Hodell et al, 2008;Hulsey & López-Fernández, 2011).…”

Niche overlap between sympatric cichlid species of the genus Rocio (Cichliformes: Cichlidae) in Guatemala

“…This could also be linked to the fact that still waterbodies tend to show lower oxygen levels, making the water flow a plausible explanation for the observed body shape variation as it has also been proposed for other cichlids in the region (McMahan et al, 2017).…”

“…Variation within each species is reflected by the differences related to mouth positioning, head shape, and slight differences in fin positioning and the caudal peduncle. This is more evident in spec- show that intraspecific body shape variation is common (Ardón et al, 2022;Macossay-Cortez et al, 2022;McMahan et al, 2017) and might lead to understanding the kinds of habitats where those species are found (Aguilar-Contreras et al, 2021). However, the similarity in closely related species might lead to the perception that morphological similarity could be biased due to the inherent intraspecific variation, limiting any analysis that suggests a pattern similar to that of ecological character displacement (Elmer et al, 2010;Garita-Alvarado et al, 2021).…”

Negative effects of artificial diets on growth and the digestive tract of 1‐month‐old Redhead cichlid ( Vieja melanura , Günther, 1862)

“…Neotropical cichlids are a highly diverse group of fish, whose taxonomic status was heavily revised in recent years (McMahan et al, 2017; Říčan et al, 2008). Still, there are significant knowledge gaps in terms of their basic biology.…”