Genomic, ecological, and morphological approaches to investigating species limits: A case study in modern taxonomy from Tropical Eastern Pacific surgeonfishes

Abstract

A wide variety of species are distinguished by slight color variations. However, molecular analyses have repeatedly demonstrated that coloration does not always correspond to distinct evolutionary histories between closely related groups, suggesting that this trait is labile and can be misleading for species identification. In the present study, we analyze the evolutionary history of sister species of Prionurus surgeonfishes in the Tropical Eastern Pacific (TEP), which are distinguished by the presence or absence of dark spots on their body. We examined the species limits in this system using comparative specimen‐based approaches, a mitochondrial gene (COI), more than 800 nuclear loci (Ultraconserved Elements), and abiotic niche comparisons. The results indicate there is a complete overlap of meristic counts and morphometric measurements between the two species. Further, we detected multiple individuals with intermediate spotting patterns suggesting that coloration is not diagnostic. Mitochondrial data recovered a single main haplotype shared between the species and all locations resulting in a complete lack of structure (Φ ST = 0). Genomic analyses also suggest low levels of genetic differentiation ( F ST = 0.013), and no alternatively fixed SNPs were detected between the two phenotypes. Furthermore, niche comparisons could not reject niche equivalency or similarity between the species. These results suggest that these two phenotypes are conspecific and widely distributed in the TEP. Here, we recognize Prionurus punctatus Gill 1862 as a junior subjective synonym of P. laticlavius (Valenciennes 1846). The underlying causes of phenotypic variation in this species are unknown. However, this system gives insight into general evolutionary dynamics within the TEP.

Fine-scale species delimitation: speciation in process and periodic patterns in nudibranch diversity

“…The present case clearly differs from the situation when a reticulated molecular phylogenetic pattern of two closely related species was used for evidence of their synonymy (Ludt et al 2019), because significant molecular and ecological data are presented for two Amphorina species and their ongoing speciation processes. When a species is still in the process of speciation (and we can expect it for a majority of species) it must preserve various degrees of connection with an ancestral species (an ancestral group of populations) and hence some ability to hybridise with the ancestral species.…”

Ictiofauna de la bahía Maguey, Oaxaca, México, y su relación con la estructura del hábitat

“…El presente estudio lo confirma al haber identificado un total de 60 especies de peces. Inicialmente, se consideraron 61 especies, ya que se incluyó a Prionurus punctatus; sin embargo, el conteo se redujo a 60 especies porque, según Ludt et al (2019), P. punctatus es un sinónimo menor de related to rocky-coral/coral-rocky (T2, T9, T3, T8), coral (T7), and mixed (T6) habitats. In this regard, certain species (P. laticlavius, L. novemfasciatus, K. elegans, K. vaigiensis, and H. passer) were associated with the depth and wave exposure attributes, with both attributes having a greater magnitude in the rocky-coral habitat (T9) (Fig.…”

Checklist of marine and estuarine fishes from the Alaska–Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico

“…: Sánchez-Jiménez et al 2018). We follow Ludt et al (2018) and consider Prionurus punctatus (Gill, 1862) a junior synonym.…”