Species delimitation by DNA barcoding reveals undescribed diversity in Stelliferinae (Sciaenidae).

Stelliferinae is the third most speciose subfamily of Sciaenidae, with 51 recognized species arranged in five genera. Phylogenies derived from both morphological and molecular data support the monophyly of this subfamily, although there is no general consensus on the intergeneric relationships or the species diversity of this group. We used the barcoding region of the cytochrome oxidase C subunit I (COI) gene to verify the delimitation of Stelliferinae species based on the Automatic Barcode Gap Discovery (ABGD), Generalized Mixed Yule Coalescence (GMYC), and Bayesian Poisson Tree Process (bPTP) methods. In general, the results of these different approaches were congruent, delimiting 30-32 molecular operational taxonomic units (MOTUs), most of which coincided with valid species. Specimens of Stellifer menezesi and Stellifer gomezi were attributed to a single species, which disagrees with the most recent review of this genus. The evidence also indicated that Odontoscion xanthops and Corvula macrops belong to a single MOTU. In contrast, evidence also indicates presence of distinct lineages in both Odontoscion dentex and Bairdiella chrysoura. Such results are compatible with the existence of cryptic species, which is supported by the genetic divergence and haplotype genealogy. Therefore, the results of the present study indicate the existence of undescribed diversity in the Stelliferinae, which reinforces the need for an ample taxonomic review of the fish in this subfamily.

Multi-locus phylogeny of the catfish genus Ictalurus Rafinesque, 1820 (Actinopterygii, Siluriformes) and its systematic and evolutionary implications.

BACKGROUND: Ictalurus is one of the most representative groups of North American freshwater fishes. Although this group has a well-studied fossil record and has been the subject of several morphological and molecular phylogenetic studies, incomplete taxonomic sampling and insufficient taxonomic studies have produced a rather complex classification, along with intricate patterns of evolutionary history in the genus that are considered unresolved and remain under debate. RESULTS: Based on four loci and the most comprehensive taxonomic sampling analyzed to date, including currently recognized species, previously synonymized species, undescribed taxa, and poorly studied populations, this study produced a resolved phylogenetic framework that provided plausible species delimitation and an evolutionary time framework for the genus Ictalurus. CONCLUSIONS: Our phylogenetic hypothesis revealed that Ictalurus comprises at least 13 evolutionary units, partially corroborating the current classification and identifying populations that emerge as putative undescribed taxa. The divergence times of the species indicate that the diversification of Ictalurus dates to the early Oligocene, confirming its status as one of the oldest genera within the family Ictaluridae.

Genomic assessment reveals signal of adaptive selection in populations of the Spotted rose snapper Lutjanus guttatus from the Tropical Eastern Pacific.

Background: The lack of barriers in the marine environment has promoted the idea of panmixia in marine organisms. However, oceanographic conditions and habitat characteristics have recently been linked to genetic structure in marine species. The Tropical Eastern Pacific (TEP) is characterized by dynamic current systems and heterogeneous oceanographic conditions. The Gulf of Panama (part of the equatorial segment for the TEP) is influenced by a complex current system and heterogeneous environment, which has been shown to limit the gene flow for shoreline species. Next Generation Sequencing (NGS) has contributed to detect genetic differences in previously reported panmictic species by the assessment of loci associated with selection and to understand how selection acts affects marine populations. Lutjanus guttatus is a species distributed in the TEP for which previous studies using mitochondrial data recovered a panmictic pattern along its distributional range. In this study, we used SNP data of L. guttatus individuals sampled along its range to evaluate population genetic structure and investigate whether oceanographic factors influence the species' genetic architecture. Finally, we assessed the role of adaptive selection by evaluating the contribution of outlier and neutral loci to genetic divergence. Methods: The RADcap method was used to obtain 24 million paired reads for 123 individuals of L. guttatus covering nearly all its distributional area. Genetic variation was assessed using both spatial and non-spatial methods by comparing three different data sets: (i) a Combined Loci (CL dataset = 2003 SNPs); a search for putative loci under selection allowed the evaluation of (ii) Neutral Loci (NL dataset = 1858 SNPs) and (iii) Outlier Loci (OL dataset = 145 SNPs). We used the estimating effective migration surface (EEMS) approach to detect possible barriers to gene flow. Results: Genetic differences were found in the OL dataset, showing two clusters (Northern and Southern), whereas NL showed no differences. This result may be related to the Selection-Migration balance model. The limit between the Northern and Southern groups was in the Gulf of Panama, which has been previously identified as a barrier to gene flow for other species, mainly due to its heterogeneous oceanographic conditions. The results suggest that selection plays an important role in generating genetic differences in Lutjanus guttatus. A migration corridor was detected that coincides with the Costa Rica Coastal Current that flows from Central America to the Gulf of California, allowing the homogenization of the northern population. In the Southern cluster, a migration corridor was observed with the OL from Panama to Colombia, which could be associated with the currents found in the Gulf of Panama. Genetic variation found in the OL of Lutjanus guttatus highlights the usefulness of NGS data in evaluating the role of selection in population differentiation.

Phylogenetic relationships of the North American catfishes (Ictaluridae, Siluriformes): Investigating the origins and parallel evolution of the troglobitic species.

Insular habitats have played an important role in developing evolutionary theory, including natural selection and island biogeography. Caves are insular habitats that place extreme selective pressures on organisms due to the absence of light and food scarcity. Therefore, cave organisms present an excellent opportunity for studying colonization and speciation in response to the unique abiotic conditions that require extreme adaptations. One vertebrate family, the North American catfishes (Ictaluridae), includes four troglobitic species that inhabit the karst region bordering the western Gulf of Mexico. The phylogenetic relationships of these species have been contentious, and conflicting hypotheses have been proposed to explain their origins. The purpose of our study was to construct a time-calibrated phylogeny of Ictaluridae using first-occurrence fossil data and the largest molecular dataset on the group to date. We test the hypothesis that troglobitic ictalurids have evolved in parallel, thus resulting from repeated cave colonization events. We found that Prietella lundbergi is sister to surface-dwelling Ictalurus and that Prietella phreatophila + Trogloglanis pattersoni are sister to surface-dwelling Ameiurus, suggesting that ictalurids colonized subterranean habitats at least twice in evolutionary history. The sister relationship between Prietella phreatophila and Trogloglanis pattersoni may indicate that these two species diverged from a common ancestor following a subterranean dispersal event between Texas and Coahuila aquifers. We recovered Prietella as a polyphyletic genus and recommend P. lundbergi be removed from this genus. With respect to Ameiurus, we found evidence for a potentially undescribed species sister to A. platycephalus, which warrants further investigation of Atlantic and Gulf slope Ameiurus species. In Ictalurus, we identified shallow divergence between I. dugesii and I. ochoterenai, I. australis and I. mexicanus, and I. furcatus and I. meridionalis, indicating a need to reexamine the validity of each species. Lastly, we propose minor revisions to the intrageneric classification of Noturus including the restriction of subgenus Schilbeodes to N. gyrinus (type species), N. lachneri, N. leptacanthus, and N. nocturnus.

Genome-wide species delimitation analyses of a silverside fish species complex in central Mexico indicate taxonomic over-splitting.

BACKGROUND: Delimiting species across a speciation continuum is a complex task, as the process of species origin is not generally instantaneous. The use of genome-wide data provides unprecedented resolution to address convoluted species delimitation cases, often unraveling cryptic diversity. However, because genome-wide approaches based on the multispecies coalescent model are known to confound population structure with species boundaries, often resulting in taxonomic over-splitting, it has become increasingly evident that species delimitation research must consider multiple lines of evidence. In this study, we used phylogenomic, population genomic, and coalescent-based species delimitation approaches, and examined those in light of morphological and ecological information, to investigate species numbers and boundaries comprising the Chirostoma "humboltianum group" (family Atherinidae). The humboltianum group is a taxonomically controversial species complex where previous morphological and mitochondrial studies produced conflicting species delimitation outcomes. We generated ddRADseq data for 77 individuals representing the nine nominal species in the group, spanning their distribution range in the central Mexican plateau. RESULTS: Our results conflict with the morphospecies and ecological delimitation hypotheses, identifying four independently evolving lineages organized in three geographically cohesive clades: (i) chapalae and sphyraena groups in Lake Chapala, (ii) estor group in Lakes Pátzcuaro and Zirahuén, and (iii) humboltianum sensu stricto group in Lake Zacapu and Lerma river system. CONCLUSIONS: Overall, our study provides an atypical example where genome-wide analyses delineate fewer species than previously recognized on the basis of morphology. It also highlights the influence of the geological history of the Chapala-Lerma hydrological system in driving allopatric speciation in the humboltianum group.

Historical analysis of an imperiled fish species: environmental variables modeling, biotic interactions, extirpation, and current restricted-range.

BACKGROUND: Analyses of spatial and temporal patterns and interactions are important for determining the abiotic factors limiting populations and the impact from other species and different anthropogenic stressors that promote the extirpation of species. The fish Hubbsina turneri de Buen (1940) was studied as a model species in a historical context at varying locations. Originally distributed only in the Lerma-Chapala basin, the main lake complex in Mexico, this species has not been collected from Lake Cuitzeo (LC) and now is restricted to Lake Zacapu (LZ). At present, the Highland splitfin is classified as critically endangered. METHODS: Historical information of LC and historical and current information from LZ were explored by applying cluster analysis and generalized additive mixed model (GAMM) to describe the biotic interactions among fish species and the relationship between density and environmental variables, respectively. The two lakes' contrasting abiotic/biotic characteristics provided elements to describe some species distribution limits in chemical ion gradients. Extirpation calendar dates were estimated using an optimal linear estimation method. Finally, a bibliographic review was conducted on the causes that promoted the extirpation and restriction of H. turneri and the prognosis for its reestablishment and conservation. RESULTS: Clusters showed the fishes relationship according to their distribution along the lakes. GAMM indicated that high H. turneri density is related to low hardness/fecal coliforms, medium depth/suspended solids, and high oxygen concentration. Estimated extirpation dates were between the years 2013 and 2018. The extirpation was linked to an abrupt drop in the LC volume, water quality degradation, increased biotic interactions within macrophytes habitats with native and introduced species, and fisheries bycatches. The current restricted range of H. turneri resulted from the draining of the larger lake, forcing the remaining populations to small spring-fed remnants. Recent samplings in LZ resulted in a low number of individuals. CONCLUSIONS: The integration of ecological interactions derived from statistical models, extirpation dates from nonparametric tests, and the exhaustive analysis of historical information can be applied to define the current situation of imperiled, ecologically relevant species, in different aquatic ecosystems. We are confident that this general framework is important for determining (1) the requirements and limitations of populations regarding abiotic variables, (2) biotic interactions (trophic and spatial) with native and introduced species, and (3) different anthropogenic stressors within and around the ecosystem. This knowledge will also allow understanding those aspects that contribute to the extirpation of populations and could help the restoration of the habitat and the reintroduction of extirpated species.

Phylogeography and evolutionary history of the Panamic Clingfish Gobiesox adustus in the Tropical Eastern Pacific.

The Panamic Clingfish Gobiesox adustus is widely distributed in the Tropical Eastern Pacific (TEP), from the central Gulf of California, Mexico to Ecuador, including the oceanic Revillagigedo Archipelago, and Isla del Coco. This cryptobenthic species is restricted to very shallow rocky-reef habitats. Here, we used one mitochondrial and three nuclear DNA markers from 155 individuals collected across the distribution range of the species in order to evaluate if geographically structured populations exist and to elucidate its evolutionary history. Phylogenetic analyses recovered a monophyletic group, with four well-supported, allopatric subgroups. Each subgroup corresponded to one of the following well-known biogeographic regions/provinces: 1) the Revillagigedo Archipelago, 2) the Cortez + Mexican provinces (Mexico), 3) the Panamic province (from El Salvador to Ecuador), and 4) Isla del Coco. A molecular-clock analysis showed a mean date for the divergence between clade I (the Revillagigedos and Cortez + Mexican provinces) and clade II (Panamic province and Isla del Coco) in the Pliocene, at ca. 5.33 Mya. Within clade I, the segregation between the Revillagigedos and Cortez + Mexican province populations was dated at ca. 1.18 Mya, during the Pleistocene. Within clade II, the segregation between samples of Isla del Coco and the Panamic province samples was dated at ca. 0.77 Mya, during the Pleistocene. The species tree, Bayesian species delimitation tests (BPP and STACEY), the ΦST, AMOVA, and the substantial genetic distances that exist between those four subgroups, indicate that they are independent evolutionary units. These cladogenetic events seem to be related to habitat discontinuities, and oceanographic and geological processes that produce barriers to gene flow for G. adustus, effects of which are enhanced by the intrinsic ecological characteristics of this species.

A multi-locus approach to elucidating the evolutionary history of the clingfish Tomicodon petersii (Gobiesocidae) in the Tropical Eastern Pacific.

Marine species that are widely distributed in the Tropical Eastern Pacific (TEP) has served as a model for studying biogeographic patterns resulting from the effects of intraregional habitat discontinuities and oceanographic processes on the diversification and evolution of cryptobenthic reef fishes. Tomicodon petersii, a clingfish (Gobiesocidae) endemic to the TEP, is found on very shallow rocky reefs from central Mexico to northern Peru, and in the Cocos and Galapagos islands. We evaluated the effect of likely biogeographic barriers in different parts of the TEP on the diversification process of this species. We used one mitochondrial and three nuclear DNA markers from 112 individuals collected across the distribution range of T. petersii. Our phylogenetic results showed the samples constituted a monophyletic group, with three well-supported, allopatric subgroups: in the Mexican province, the Panamic province (from El Salvador to Ecuador), and the Galapagos Islands. The split between the Mexican and more southerly clades was estimated to occur at the end of the Miocene ca. 5.74 Mya, and the subsequent cladogenetic event separating the Galapagos population from the Panamic population at the junction of the Pliocene and Pleistocene, ca. 2.85 Mya. The species tree, Bayesian species delimitation tests (BPP), STACEY, and substantial genetic distances separating these three populations indicate that these three independent evolutionary units likely include two unnamed species. The cladogenetic events that promoted the formation of those genetically differentiated groups are consistent with disruptive effects on gene flow of habitat discontinuities and oceanographic processes along the mainland shoreline in the TEP and of ocean-island isolation, in conjunction with the species intrinsic life-history characteristics.

Genetic differentiation in the genus Characodon: implications for conservation and taxonomy.

The subfamily Goodeinae is a group of fishes endemic to the Mexican highlands. Most of the species are restricted to small and isolated streams or springs. Within this subfamily, the genus Characodon is the earliest diverging lineage of which three species have been described: C. lateralis, C. audax, and C. garmani, with the latter, considered extinct. Characodon lateralis and C. audax are classed as endangered, and have been the subject of taxonomic controversy since their description: previous studies have recognized a genetic differentiation in two groups separated by the El Salto waterfall, but morphological analyses contradict these genetic results. We perform a phylogeographic study using the mitochondrial cytb gene and d-loop region to elucidate the evolutionary history of C. lateralis and C. audax. The results with both markers show the presence of two highly differentiated haplogroups; one distributed north and the other distributed south of the waterfall, with genetic distances of 1.7 and 13.1% with cytb and d-loop respectively, and divergence calculated to have occurred 1.41 Mya. Significant genetic structure was found within each haplogroup and suggests the existence of at least four Evolutionary Significant Units (ESUs) within the examined populations. The possible processes identified as contributing to the formation of differentiated genetic groups are isolation, low population size, recurrent bottlenecks, and the strong sexual selection exhibited by the genus.

Population-level morphological variation of Anisotremus interruptus (Gill, 1862) (Perciformes: Haemulidae) in the Tropical Eastern Pacific, with the description of two new species.

The family Haemulidae is a wide-ranging group of marine fishes that are of significant commercial value in the Tropical Eastern Pacific (TEP). Phylogenetic studies on the species Anisotremus interruptus have revealed high levels of genetic diversity as well as divergence among populations in the TEP, which suggests that the taxonomic diversity of A. interruptus could be underestimated. Anisotremus interruptus has a large distribution, ranging from central Baja California, Mexico to northern Peru, including all oceanic islands except Clipperton. Recent genetic studies on this taxon indicate the presence of a species complex of at least three distinctive lineages. We performed a comparative study of the population-level meristic and morphometric variation of A. interruptus in the TEP to evaluate and identify possible morphological features concordant with the genetic differentiation of populations. Our results provide evidence of the presence of two new species of the genus Anisotremus, A. perezponcedeleoni sp. n. from the Revillagigedo Archipelago and A. espinozai sp.n. from Galapagos Archipelago-Cocos Island.

Molecular systematics of the Awaous banana complex (River gobies; Teleostei: Oxudercidae).

Diadromous fishes can exhibit interesting evolutionary and population-level patterns given their use of freshwater and marine environments as part of their life histories. The River goby genus Awaous are prominent members of riverine ichthyofaunas and occur throughout Atlantic and Pacific slopes of the Americas from the southern United States to Ecuador and Brazil. Here we study the widespread and polymorphic Awaous banana complex to assess phylogeographic patterns and test previous hypotheses that all populations of this species in the Americas belong to the same species. Analysis of sequence data based on the mitochondrial cytochrome oxidase I gene shows multiple clades within the Atlantic and Pacific basins, which correspond to previously described species. Additionally, haplotype analysis demonstrates unique and unconnected networks between these species. Within these clades we document biogeographic patterns that are congruent with results of other co-occurring diadromous species, as well as a novel biogeographic pattern for the region. Our results support the recognition of distinct species of Awaous in the Atlantic (A. banana and A. tajasica) and Pacific (A. transandeanus) basins. These results are concordant with previously established morphological characters permitting the separation of these species.

Ictiofauna de la zona intermareal rocosa del Área de Conservación Guanacaste, Pacífico Norte de Costa Rica: diversidad y aspectos ecológicos y biogeográficos

Introducción: El intermareal rocoso constituye un paisaje marino costero dominante en el Pacífico Tropical Oriental, albergando comunidades biológicas altamente diversas y funcionalmente complejas. El conocimiento sobre la diversidad y los diversos procesos biológicos que ocurren en tales ambientes es, no obstante, bastante limitado a escala regional. Objetivo: Cuantificar, describir y comparar (a escala regional) la diversidad ictiológica asociada al intermareal rocoso del Área de Conservación Guanacaste (ACG), Costa Rica, así como evaluar y discutir algunos patrones biogeográficos y ecológicos. Métodos: Entre 2014 y 2019 se muestrearon un total de 49 pozas de marea en siete ubicaciones dentro del ACG. Se obtuvieron datos sobre diversidad absoluta (presencia/ausencia de especies), además de algunos datos ecológicos (estatus de residencia, estadio(s) de desarrollo, gremio trófico, hábitos de agrupación y crípticos y distribución generalizada) los cuales se compararon con datos publicados de otros estudios/inventarios llevados a cabo en diversas localidades (20) a lo largo de la costa del Pacífico Oriental. Por medio de un análisis de similitud se evaluaron posibles patrones de agrupamiento entre localidades (según su composición de especies) y, bajo una perspectiva biogeográfica, hipótesis previas de regionalización. Resultados: Se registraron un total de 67 especies de peces óseos asociadas al intermareal rocoso del ACG, siendo la localidad con datos publicados, más diversa a nivel del Pacífico Oriental. En el ACG los componentes/categorías transitorio con 30 especies (44.8 %), juveniles con 38 especies (55.9 %), carnívoros con 47 especies (70.1 %), solitarios con 32 especies (47.8 %) y endémico del PTO con 66 especies (98 %), fueron dominantes. A nivel regional se recopilaron datos para un total de 246 especies. Los resultados del análisis de similitud soportaron el esquema de división biogeográfico, definido a priori, a nivel regional, con las localidades ubicadas dentro de las provincias Californiana, Cortez, Mexicana, Panámica y Peruana-Chilena recuperadas como grupos altamente consistentes. Esta estructura es consecuente con el efecto de barreras como las brechas arenosas de Sinaloa y Centroamericana, entre otras, limitando el flujo de especies entre unidades biogeográficas. Conclusiones: El ACG presenta una elevada diversidad ictiológica asociada a su intermareal rocoso producto de una combinación de factores única a nivel regional. Los resultados de este estudio refuerzan además la necesidad de realizar más estudios básicos y aplicados a diferentes escalas local y regional con el objetivo de ayudar a comprender y conocer mejor diversos aspectos clave de la dinámica y procesos físico-químico-biológicos ocurriendo en las zonas intermareales, de su riqueza biológica asociada, de su importancia dentro del paisaje marino-costero como un continuo y de las posibles afectaciones que estos podrían sufrir debido al impacto de las actividades humanas.

Introduction: The rocky intertidal constitutes a dominant coastal seascape in the Eastern Tropical Pacific, harboring highly diverse and functionally complex biological communities. The knowledge about the diversity and the diverse biological processes that occur in such environments is, however, quite limited on a regional scale. Objective: Quantify, describe and compare (on a regional scale) the ichthyological diversity associated with the rocky intertidal zone of the Guanacaste Conservation Area (ACG), Costa Rica, as well as to evaluate and discuss some biogeographic and ecological patterns. Methods: A total of 49 tide pools were sampled between 2014 and 2019, at seven locations within the ACG. Data on absolute diversity (presence/absence of species) were obtained, in addition to some ecological data (residence status, development stage (s), trophic guild, aggregation and cryptic habits and generalized geographic distribution), these data were compared with published records from other surveys/inventories carried out at various locations (20) along the Eastern Pacific coast. Through a similarity analysis, both possible clustering patterns between localities (according to their species composition) and previous hypotheses of regionalization, under a biogeographic perspective, were evaluated. Results: A total of 67 species of bony fish were recorded in the rocky intertidal area of the ACG, being this the most diverse locality (with published data) in the Eastern Pacific. The components/categories "transitory" with 30 species (44.8 %), "juveniles" with 38 species (55.9 %), "carnivores" with 47 species (70.1 %), "solitary" with 32 species (47.8 %) and "endemic to the ETP" with 66 species (98 %), were dominant (in terms of the total number of species) within the ACG. The results of the similarity analysis supported the biogeographic division scheme, defined a priori; with the localities within the Californian, Cortez, Mexican, Panamic and Peruvian-Chilean provinces recovered as highly consistent groups. This structure is consistent with the effect of barriers such as the sandy gaps of Sinaloa and Central America, among others, limiting the flow of species between biogeographic units. Conclusions: The ACG has a high ichthyological diversity associated with its rocky intertidal zone, which is product of a unique combination of factors at the regional level. The results of this study reinforce the need to carry out more basic and applied studies with the aim of helping to better understand and know different key aspects of the dynamics and physical-chemical-biological processes occurring in intertidal zones, of its associated biological diversity, of its importance within the marine-coastal landscape as a continuum and of the possible effects that these environments could suffer due to the impact of human activities.

Genetic differentiation among populations of the blackfin goodea Goodea atripinnis (Cyprinodontiformes: Goodeidae): implications for its evolutionary history.

Central Mexico is characterized by a complex topography that is the result of historic and contemporary tectonic and climatic factors. These events have influenced the evolutionary history of numerous freshwater fishes in the region. Nonetheless, recent studies have shown that life-history traits and ecological characteristics of species may influence dispersal capabilities and the degree of genetic connectivity. Goodea (Cyprinodontiformes: Goodeidae) is one of the most widely distributed and environmentally tolerant genera of goodeids. In this study, the authors analysed variation in the mitochondrial cytochrome b gene to evaluate the phylogeographic relationships, genetic structure, genetic diversity and demographic history of Goodea from across its distribution range. They found low genetic differentiation and identified shared haplotypes among several regions. Geographic segregation was found in samples southwest and northeast of the Lower Lerma region, with some internal isolated groups showing phylogeographic differentiation and unique haplotypes. The AMOVA best explained genetic structure when grouped by haplogroups rather than when grouped by recognized biogeographic regions. Several regions showed null genetic diversity, raising the possibility of dispersal mediated by humans. Finally, Bayesian Skyline Plot analysis showed a population expansion for the Southwest haplogroup, except for the Armería population and sub-group II of the Northeast haplogroup. All this suggests a recent colonization of Goodea atripinnis throughout some of the biogeographic regions currently inhabited by this species.

Reproductive cycle of native viviparous fish species (Actinopterygii: Cyprinodontiformes: Goodeidae) in a subtropical Mexican lake

Reproductive tactics and strategies contribute to the persistence and maintenance of long-term populations in fish species. Members of the subfamily Goodeinae are a group of small-bodied freshwater fish with specialized reproduction (viviparity-matrotrophy). They are found in the highlands of central Mexico, most of them endemic. The aim of this study was to conduct a comprehensive investigation to evaluate the annual reproductive cycle of seven species of goodeines (splitfins). We carried out our study in the subtropical Lake Zacapu, Mexico, with bi-monthly sampling from May 2019 to March 2020. We obtain the fertility, size at first maturity (L50), sex ratio, and gonadosomatic index. Our result shows that populations of goodeines have high fertility compared to other populations of the same species in other aquatic systems and also to other species of goodein. We found that males mature at smaller sizes than females, the observed proportion of females was greater than males in all the goodeines. Lake Zacapu goodeines have two reproductive peaks, one in spring (April to June) and another in fall (September to November). These tactics (fertility rates, sex ratio, reproductive period) and strategies (viviparity-matrotrophy) favor reproductive success in this environmentally stable subtropical lake in the highlands of Mexico.(AU)

Las tácticas y estrategias reproductivas contribuyen a la persistencia y el mantenimiento de las poblaciones a largo plazo en especies de peces. Miembros de la subfamilia Goodeinae son un grupo de peces de agua dulce con reproducción especializada (viviparidad-matrotrofia). Se encuentran en el centro de México, la mayoría de ellos endémicos. El objetivo de este estudio fue realizar una investigación integral para evaluar el ciclo reproductivo anual de siete especies de goodeines o mexclapiques. Realizamos nuestro estudio en el lago subtropical de Zacapu, México, con muestreo bimestral de mayo de 2019 a marzo de 2020. Nuestros resultados muestran que las poblaciones de goodeines tienen una alta fertilidad en comparación con otras poblaciones de la misma especie en otros sistemas acuáticos y también con otras especies de goodeines. Encontramos que los machos maduran en tamaños más pequeños que las hembras, la proporción observada de hembras fue mayor que los machos en todas las goodeines. Los goodeines del lago Zacapu tienen dos picos reproductivos, uno en primavera (abril a junio) y otro en otoño (septiembre a noviembre). Estas tácticas (fertilidad, proporción de sexos, período reproductivo) y estrategias (viviparidad-matrotrofia) favorecen el éxito reproductivo en este lago subtropical ambientalmente estable en el altiplano de México.(AU)

Genetic diversification of acanthocephalans of the genus Floridosentis Ward 1953 (Acanthocephala: Neoechinorhynchidae), parasites of mullets from the Americas.

Adult worms of the genus Floridosentis are endoparasites of marine fishes of the genus Mugil and are broadly distributed in the Americas. Currently, Floridosentis includes two species, F. mugilis, distributed in the Gulf of Mexico and along the Atlantic Ocean coast, and F. pacifica, restricted to the Pacific Ocean coast. The aim of this study was to explore the species limit of both species of the genus Floridosentis, collected in 37 localities in eight countries: Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Ecuador and Venezuela. We sequenced 253 specimens to build a comprehensive dataset for three genes: the cytochrome c oxidase subunit I (cox 1) from mitochondrial DNA, the internal transcribed spacers ITS1 and ITS2 including the 5.8S gene (ITS region), and the D2 + D3 domains of the large subunit (LSU) of nuclear DNA. Maximum likelihood and Bayesian analyses with the cox 1 and concatenated (cox 1 + ITS+LSU) datasets were conducted. Two species delimitation methods were implemented, the Automatic Barcode Gap Discovery (ABGD), and Bayesian species delimitation (BPP), plus a haplotype network inferred with 253 specimens, allowing us to validate two nominal species of Floridosentis., F. mugilis, plus one linage distributed in the Gulf of Mexico and along the Atlantic Ocean coast, and F. pacifica, plus two additional lineages distributed along the Pacific Ocean coast. All these lineages are shared by both species of mullet (Mugil curema and M. cephalus). The currents in the Atlantic Ocean, Pacific Ocean and Gulf of Mexico, in combination with the biology of the definitive hosts, have played a key role in the distribution of the two nominal species and of the three lineages of Floridosentis across the Americas.

Genetic diversity and structure of circumtropical almaco jack, Seriola rivoliana: tool for conservation and management.

The almaco jack, Seriola rivoliana, is a circumtropical pelagic fish of importance both in commercial fisheries and in aquaculture. To understand levels of genetic diversity within and among populations in the wild, population genetic structure and the relative magnitude of migration were assessed using mtDNA sequence data and single nucleotide polymorphisms (SNPs) from individuals sampled from locations in the Pacific and Atlantic Oceans. A total of 25 variable sites of cytochrome c oxidase subunit 1 and 3678 neutral SNPs were recovered. Three genetic groups were identified, with both marker types distributed in different oceanic regions: Pacific-1 in central Pacific, Pacific-2 in eastern Pacific and Atlantic in western Atlantic. Nonetheless, the analysis of SNP identified a fourth population in the Pacific coast of Baja California Sur, Mexico (Pacific-3), whereas that of mtDNA did not. This mito-nuclear discordance is likely explained by a recently diverged Pacific-3 population. In addition, two mtDNA haplogroups were found within the western Atlantic, likely indicating that the species came into the Atlantic from the Indian Ocean with historical gene flow from the eastern Pacific. Relative gene flow among ocean basins was low with r m < 0.2, whereas in the eastern Pacific it was asymmetric and higher from south to north (r m > 0.79). The results reflect the importance of assessing genetic structure and gene flow of natural populations for the purposes of sustainable management.

Independent evolutionary lineage of the clingfish Gobiesox adustus (Gobiesocidae) from Isla del Coco, Costa Rica

Introduction: Isla del Coco is an important protected area for marine fauna in the Eastern Tropical Pacific. In this area, the species that inhabit the intertidal zone have been subject to few studies. One of the species inhabiting these areas is the clingfish Gobiesox adustus (Gobiesocidae). Objective: To analyze for the first time the mitochondrial gene cytochrome oxidase subunit 1 (cox1) of G. adustus' population from Isla del Coco and compare it with those of continental coast of Costa Rica and Ecuador. Methods: We constructed a haplotype network for these samples. Genetic diversity, distance and structure were calculated by several software. The historical demography of Isla del Coco samples was assessed with the method Bayesian skyline plot as implemented in BEAST2. Results: The samples segregate into three haplogroups: one consisting of the Isla del Coco samples, a second consisting of a subset of the Ecuador samples, and a third consisting of Costa Rica and the remaining Ecuador samples. The genetic distances between the three haplogroups range between 1.6% and 2.1% (uncorrected p-distance), and pairwise ΦST and AMOVA results between the three haplogroups show high and significant values. Conclusions: The Isla del Coco haplogroup showed a Pleistocene population growth, which agrees with demographic patterns found in other marine organisms. The history of isolation of the G. adustus population from Isla del Coco demonstrates the evolutionary independence of this population.

Introducción: Isla del Coco es un área protegida importante para la fauna marina en el Pacifico Oriental Tropical. En esta área, las especies que habitan la zona intermareal han sido objeto de pocos estudios. Una de las especies que habitan en estas áreas es el clingfish Gobiesox adustus (Gobiesocidae). Objetivo: Analizar por primera vez el gen mitocondrial citocromo oxidasa sub unidad 1 (cox1) de poblaciones de Isla del Coco y compararlo con las de la zona continental de Costa Rica y Ecuador. Métodos: Se construyó una red de haplotipos. La diversidad, la distancia y la estructura genética fueron calculadas por diversos programas. La demografía histórica de las muestras de Isla del Coco fue evaluada con el método Bayesian skyline plot implementado en BEAST2. Resultados: Las muestras se agruparon en tres haplogrupos: en un haplogrupo se incluyó a los individuos de Isla del Coco, otro haplogrupo integró las muestras de Ecuador y un tercer grupo incluyó las muestras restantes de Costa Rica y Ecuador. Las distancias genéticas entre los tres haplogrupos oscilan entre 1.6% y 2.1% (p-distancia, no corregida), las distancias ΦST y los resultados de AMOVA entre los tres haplogrupos muestran valores altos y significativos. Conclusiones: El haplogrupo de Isla del Coco mostró un crecimiento poblacional datado en el Pleistoceno, coincidiendo con la demografía poblacional encontrada en otros organismos marinos. La historia de aislamiento de la población de G. adustus de Isla del Coco demostró la independencia evolutiva de esta población.

Cryptic molecular diversity in the morphologically variable rotiferan Brachionus quadridentatus (Rotifera: Monogononta)

Brachionus quadridentatus es una especie morfológicamente variable, distribuida por todo el mundo. Su taxonomía es confusa debido a las numerosas variantes infrasubespecíficas descritas en este taxón. Con la taxonomía basada en la morfología, B. quadridentatus tiene tres variantes reconocidas: B. quadridentatus quadridentatus, B. quadridentatus f. brevispinus and B. quadridentatus f. cluniorbicularis. En este estudio, exploramos la diversidad genética entre algunas poblaciones de B. quadridentatus, usando secuencias de los genes COI ADNmt y 18S ARNr. El análisis de delimitación de especies coalescente usando el gen 18S apoya la presencia de al menos tres especies putativas dentro del complejo B. quadridentatus. Estos resultados estuvieron en concordancia con los análisis filogenético y GMYC usando el gen 18S. Sin embargo, se encontró variación en morfología y secuencias del gen COI dentro de cada una de las tres especies putativas. Se encontraron siete linajes delimitados por las secuencias del gen COI usando el método de delimitación ABGD, que además están morfologicamente diferenciadas. Se encontró discordancia mitonuclear entre la filogenia del gen COI y la del gen 18S. La incongruencia entre el marcador mitocondrial y el nuclear puede ser explicada por sorteo incompleto de linaje.

Brachionus quadridentatus is a morphologically variable species of rotifer distributed worldwide. The taxonomy of this species is confused, with numerous infrasubspecific variants described in the taxon: B. quadridentatus quadridentatus, B. quadridentatus f. brevispinus and B. quadridentatus f. cluniorbicularis. In this study, we explored genetic diversity among some populations of B. quadridentatus, using sequences of mitochondrial COI and nuclear 18S genes. The coalescent species delimitation analysis with the 18S gene highly supports the presence of at least three putative species within the B. quadridentatus complex. These results were in agreement with the phylogenetic and GMYC analysis using the 18S gene. However, we also found variation within each of these three putative species in morphology and COI gene sequences. There were seven morphologically differentiated lineages that were recovered as distinct based on COI gene sequences using the ABGD delimitation method. As such, mitonuclear discordance between COI and 18S phylogenies was found. The incongruence between mitochondrial and nuclear markers could be explained by incomplete lineage sorting.

An update to the inventory of shore-fishes from the Parque Nacional Sistema Arrecifal Veracruzano, Veracruz, México.

Data on marine and brackish-water fishes recorded in the area of the Parque Nacional Sistema Arrecifal Veracruzano in the southwest Gulf of Mexico were extracted from online aggregators of georeferenced location records, the recent ichthyological literature reviewed, and collections and observations made to provide a more complete faunal inventory for that park. Those actions added 95 species to a comprehensive inventory published in 2013, and brought the total to 472 species, an increase of 22%. Seventy-four percent of the additions came from online aggregators of georeferenced species records, which clearly demonstrates the value of reviewing and incorporating such data into species inventories. However, different aggregators recorded different sets of species, and some of their data were linked to outdated taxonomy or included identification errors. Hence individual records from multiple aggregators need to be obtained and reviewed for such issues when using such data to compile and revise faunal inventories. Existing lists also need to be carefully reviewed to ensure that errors are not perpetuated during updates.