A reappraisal of Stegastes species occurring in the South Atlantic using morphological and molecular data

Abstract

The taxonomic status of Pomacentridae species can be difficult to determine, due to the high diversity, and in some cases, poorly understood characters, such as color patterns. Although Stegastes rocasensis, endemic to the Rocas atoll and Fernando de Noronha archipelago, and S. sanctipauli, endemic to the São Pedro and São Paulo archipelago, differ in color pattern, they exhibit similar morphological characters and largely overlapping counts of fin rays and lateral-line scales. Another nominal insular species, S. trindadensis, has recently been synonymized with S. fuscus but retained as a valid subspecies by some authors. Counts and morphometric analyses and mitochondrial DNA (COI, 16SrRNA, CytB) and nuclear DNA (rag1 and rhodopsin) comparisons of three insular species (S. rocasensis, S. sanctipauli and S. trindadensis) and three other South Atlantic species (S. fuscus, S. variabilis and S. pictus) were carried out in the present study. Analyses of the principal components obtained by traditional multivariate morphometry indicate that the species in general have similar body morphology. Molecular analyses revealed conspicuous similarity between S. rocasensis and S. sanctipauli and between S. trindadensis and S. fuscus and a clear divergence between S. variabilis from Northeast Brazil and S. variabilis from the Caribbean region. Our data suggest that S. sanctipauli is a synonym of S. rocasensis, support the synonymy of S. trindadensis with S. fuscus, and reveal the presence of a likely cryptic species in the Caribbean that has been confused historically with S. variabilis.

Systematics of Damselfishes

“…Stegastes variabilis has also been restricted to Brazil, and the widespread species that occurs elsewhere in the western Atlantic is now recognized as S. xanthurus (Robertson and Van Tassell, 2012;Smith-Vaniz and Jelks, 2014). Souza et al (2016) confirmed a genetic divergence between the two populations. Our specimen was collected off the coast of Belize (16848 0 11 00 N, 88813 0 58 00 W).…”

“…Furthermore, there are published sequences derived from that specimen labeled as Stegastes fuscus: JQ707061, JQ707096, JQ707129, JQ707164, JQ707186, JQ707219, JQ707255, JQ707289 (Frédérich et al, 2013: table S1); KC826243, KC826479, KC827380, KC827940, KC828201, KC828463, KC829313, KC830499, KC831203 (Betancur-R. et al, 2013a: table S1). Although the specific barcode sample was not identified, Souza et al (2016) were likely referring to this specimen when they mentioned a ''single record in the BOLD database identified as S. fuscus'' that ''matches sequences of S. diencaeus and appears to be a misidentification.'' Stegastes fuscus has been restricted to the coast of Brazil and USNM 327593 was collected in Belize where the name S. adustus would apply (Longley and Hildebrand, 1941;Greenfield and Woods, 1974;Smith-Vaniz et al, 1999).…”

“…Even though no pomacentrid-focused phylogeny has employed H3 prior to this study, sequences from this histone gene have been used to good effect in phylogenies of other percomorph groups (e.g., Wheeler, 2004, 2006;Sparks and Smith, 2004;Hastings, 2011, 2013;McMahan et al, 2013;Smith and Busby, 2014;Ghedotti et al, 2018;Smith et al, 2018). The nuclear gene RAG1 was chosen because it is widely used in fish systematics, including several studies of pomacentrids (e.g., Quenouille et al, 2004;Cooper et al, 2009;Frédérich et al, 2013;Lobato et al, 2014;Souza et al, 2016;Bertrand et al, 2017;Delrieu-Trottin et al, 2019). Tmo-4C4 has been used sparingly to investigate damselfishes (Allen et al, 2012a;DiBattista et al, 2015;He et al, 2018He et al, , 2019a, but it has proven to be phylogenetically informative for putative close relatives of Pomacentridae (e.g., Streelman and Karl, 1997;Streelman et al, 1998;Farias et al, 2000;Sparks and Smith, 2004;Chakrabarty, 2006;Smith et al, 2008;McMahan et al, 2013;Xia et al, 2016).…”

“…The phylogeny supports a S. partitus-S. pictus relationship (100% bootstrap) first identified by Emery and Allen (1980), on the basis of both species possessing one fewer row of cheek scales (3) than other Stegastes (4). In their analysis of Atlantic Stegastes, Souza et al (2016) also recovered a S. partitus-S. pictus clade. Our topology shares other similarities with theirs: a clade composed of S. adustus, S. beebei, S. diencaeus, S. flavilatus, S. variabilis, and S. xanthurus (treated as a population of S. variabilis therein); another clade of S. arcifrons, S. fuscus, S. planifrons, S. rectifraenum, and S. rocasensis; a third clade of S. albifasciatus, S. limbatus, S. nigricans, and S. punctatus.…”

“…All remaining Atlantic and eastern Pacific species (S. leucorus, S. lubbocki, S. redemptus, S. sanctaehelenae, and S. uenfi) are retained in Stegastes sensu stricto. We follow Souza et al (2016) in treating Stegastes sanctipauli as a synonym of S. rocasensis. Tree-based identifications (not shown) that assayed unreleased sequences in the BOLD database support this placement of S. leucorus, S. lubbocki, S. redemptus, and S. sanctaehelenae.…”