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.

Distribution and current conservation status of the Mexican Goodeidae (Actinopterygii, Cyprinodontiformes).

The current distribution and abundance of the 40 species of Goodeidae fishes known from Mexico are described, and a total of 84 Evolutionarily Significant Units (ESUs) is designated within these species. Two species and four ESUs are likely extinct with no captive populations, and three species and eight ESUs are probably extinct in the wild but have at least one captive population in Mexico, the United States, or Europe. Of the 35 extant species, the analyses indicate that nine should be considered as critically endangered, 14 as endangered, nine as vulnerable, and only three as least concern. Twenty-seven of these species have experienced substantial declines in distribution or abundance or both since 2000, and only eight appear to have remained relatively stable. Of the 72 extant ESUs, our analyses indicate that 29 should be considered as critically endangered, 21 as endangered, 18 as vulnerable, and only four as least concern. Brief summaries of the historic and current distributions and abundance of each species are provided, as well as ESU. Three strategies are recommended to conserve Mexican goodeids: protect the best-quality remaining habitats where goodeids still persist, restore degraded habitat and re-introduce species or ESUs where practical, and establish captive populations to ensure continued survival of the many species and ESUs that will almost inevitably go extinct in the coming years. Limited resources require cooperation and collaboration between scientists, conservationists, and aquarium hobbyists for successful captive maintenance.

Assessing phylogenetic information to reveal uncertainty in historical data: An example using Goodeinae (Teleostei: Cyprinodontiformes: Goodeidae).

A major emerging challenge to resolution of a stable phylogenetic Tree of Life has been incongruent inference among studies. Given the increasing ubiquity of incongruent studies, analyzing the predicted phylogenetic utility and quantitative evidence regarding contributions toward resolution of commonly-used markers in historical studies over the last decade represents an important, yet neglected, component of phylogenetics. Here we examine the phylogenetic utility of two sets of commonly-used legacy markers for understanding the evolutionary relationships among goodeines, a group of viviparous freshwater fishes endemic to central Mexico. Our analyses reveal that the validity of existing inferences is compromised by both lack of information and substantially biased patterns of nucleotide substitution. Our analyses demonstrate that many of the evolutionary relationships of goodeines remain uncertain - despite over a century of work. Our results provide an updated baseline of critically needed areas of investigation for the group and underscore the importance of quantifying phylogenetic information content as a fundamental step towards eroding false confidence in results based on weak and biased evidence.

Species or population? Systematic status of Vieja coatlicue (Teleostei: Cichlidae)

Pacific and Atlantic-slope rivers of the Isthmus of Tehuantepec in Mexico contain two cichlid species of the genus Vieja relevant to the current study, V. zonata and V. coatlicue, respectively. The Atlantic-slope species was initially considered a population of uncertain taxonomic status and recently described as a distinct species based on three putatively diagnostic morphological characters. The objective of this study was to combine new and existing genetic data, along with reanalysis of morphological characters, to test the distinctiveness of V. coatlicue. Little genetic variability and no geographic structuring were recovered. Additionally, putatively diagnostic morphological character states were present across both species, failing to separate the forms. The synthesis of molecular and morphological data supports the recognition of V. coatlicue as a junior synonym of V. zonata.(AU)

Dos especies del género Vieja se encuentran distribuidas a lo largo Istmo de Tehuantepec en México; V. zonata se distribuye en los ríos de la vertiente del Pacífico y V. coatlicue en los ríos de la vertiente del Atlántico. La especie que se distribuye en la vertiente del Atlántico era considerada como una población de estado taxonómico incierto, pero recientemente fue descrita como nueva especie en base a tres caracteres morfológicos diagnósticos. El objetivo de este estudio fue utilizar datos moleculares nuevos con datos moleculares previamente publicados en combinación con una reanálisis de los caracteres morfológicos para testear la validez taxonómica de la especie V. coatlicue. Nuestros análisis moleculares no recobran estructura geográfica y además muestran baja variabilidad genética. Además, los tres caracteres morfológicos diagnósticos se encontraron presentes en individuos de ambas especies, nuestro trabajo sugiere que estos caracteres morfológicos diagnósticos no proven información que permita separar a las formas que se distribuyen en la vertiente del Pacífico y la vertiente del Atlántico. Nuestra síntesis de datos moleculares y morfológicos provee evidencia para reconocer a V. coatlicue como una sinónima mas reciente de V. zonata.(AU)

Species or population? Systematic status of Vieja coatlicue (Teleostei: Cichlidae)

Pacific and Atlantic-slope rivers of the Isthmus of Tehuantepec in Mexico contain two cichlid species of the genus Vieja relevant to the current study, V. zonata and V. coatlicue, respectively. The Atlantic-slope species was initially considered a population of uncertain taxonomic status and recently described as a distinct species based on three putatively diagnostic morphological characters. The objective of this study was to combine new and existing genetic data, along with reanalysis of morphological characters, to test the distinctiveness of V. coatlicue. Little genetic variability and no geographic structuring were recovered. Additionally, putatively diagnostic morphological character states were present across both species, failing to separate the forms. The synthesis of molecular and morphological data supports the recognition of V. coatlicue as a junior synonym of V. zonata.(AU)

Dos especies del género Vieja se encuentran distribuidas a lo largo Istmo de Tehuantepec en México; V. zonata se distribuye en los ríos de la vertiente del Pacífico y V. coatlicue en los ríos de la vertiente del Atlántico. La especie que se distribuye en la vertiente del Atlántico era considerada como una población de estado taxonómico incierto, pero recientemente fue descrita como nueva especie en base a tres caracteres morfológicos diagnósticos. El objetivo de este estudio fue utilizar datos moleculares nuevos con datos moleculares previamente publicados en combinación con una reanálisis de los caracteres morfológicos para testear la validez taxonómica de la especie V. coatlicue. Nuestros análisis moleculares no recobran estructura geográfica y además muestran baja variabilidad genética. Además, los tres caracteres morfológicos diagnósticos se encontraron presentes en individuos de ambas especies, nuestro trabajo sugiere que estos caracteres morfológicos diagnósticos no proven información que permita separar a las formas que se distribuyen en la vertiente del Pacífico y la vertiente del Atlántico. Nuestra síntesis de datos moleculares y morfológicos provee evidencia para reconocer a V. coatlicue como una sinónima mas reciente de V. zonata.(AU)

Disentangling the drivers of diversification in an imperiled group of freshwater fishes (Cyprinodontiformes: Goodeidae).

BACKGROUND: One of the most perplexing questions in evolutionary biology is why some lineages diversify into many species, and others do not. In many cases, ecological opportunity has played an important role, leading to diversification along trophic or habitat-based axes. The Goodeidae (Teleostomi: Cyprinodontiformes) are a family of freshwater fishes with two subfamilies: Goodeinae (42 species, viviparous, heterogeneous habitats, Mesa Central of Mexico) and Empetrichthyinae (4 species, oviparous, homogeneous habitats, Great Basin of the United States). These discrepant sets of characteristics and their sister-group relationship make the goodeids amenable to a comparative study of diversification. We gathered lateral body images from more than 1600 specimens of all extant species in the family. Geometric morphometric, and phylogenetic comparative analyses were used to address whether higher species diversity correlates with higher rates of morphological shape evolution and whether there are differences in functional/habitat modules between the two subfamilies. RESULTS: This study recovered a higher rate of overall body shape evolution in the Goodeinae that is nearly double in magnitude compared to the Empetrichthyinae. A modularity test indicated that the Goodeinae displayed elevated rates of morphological evolution in comparison to the Empetrichthyinae when only trunk (locomotor) regions were compared between subfamilies. No significant differences in evolutionary shape rates were recovered when the trophic (head) regions were compared between subfamilies. DISCUSSION: These results support the hypothesis that Mexican goodeids radiated via an ecological opportunity scenario into a wide-array of novel habitats in the island-like Mesa Central as evidenced by their high rate of shape evolution, relative to the Empetrichthyinae. This study quantitatively unraveled the drivers of evolution and eliminated trophic specialization as a driving force within the Goodeidae. CONCLUSIONS: A combination of phylogenetic and morphometric data, and phylogenetic comparative analyses were used to examine body shape rate evolution within the Goodeidae. Results support the hypothesis that species in the subfamily Goodeinae on the central Mexican plateau had a higher rate of body shape evolution relative to its sister subfamily Empetrichthyinae in the Great Basin suggesting that the Goodeinae diversified via an ecological opportunity scenario along habitat, rather than trophic axes.

Assessing population-level morphometric variation of the Mountain Mullet Agonostomus monticola (Teleostei: Mugilidae) across its Middle American distribution

Population-level morphometrc variation of the Mountain Mullet (Agonostomus monticola) was assessed in 419 adult specimens from 25 sample sites (river basins) across its Middle American distribution (Pacific and Atlantic-Caribbean drainages). This analysis was based on 36 standardized linear measurements and 19 landmarks on geometric morphometrics approach. Discriminant function analysis (DFA) revealed 19 linear morphological characters with significant variation among groups. Geometrically, the most notable changes were associated to the curvature of the frontal region of the head, the anterior and posterior insertion of the first dorsal and anal fins. The resulting grouping based on the DFA and geometric morphometrics techniques (Pacific-A, Pacific-B and NE México-Caribbean) were similar to those previously recovered by genetic techniques, where the Pacific-B (Ayuquila river basin) was the most different group. Our results provide morphological evidence for considering Agonostomus monticola as a complex of evolutionary entities, represented by two forms in the Pacific Ocean and another in the Atlantic Ocean.(AU)

La variación morfométrica de poblaciones de la lisa de montaña Agonostomus monticola fue evaluada en 419 especímenes adultos recolectados en 25 sitios (cuencas) a través de su distribución mesoamericana (Pacífico, Atlántico y cuencas del Caribe). El análisis fue basado en 36 medidas lineales estandarizadas y 19 puntos de referencia basados en morfometría geométrica. El análisis de función discriminante (AFD) reveló 19 caracteres morfométricos con variación significativa entre grupos. Geométricamente, los cambios más notables estuvieron asociados con la curvatura de la región frontal de la cabeza y la inserción anterior y posterior de la primera aleta dorsal y de la aleta anal. Los agrupamientos resultantes del AFD y del análisis de morfometría geométrica (Pacífico-A, Pacífico-B y NE México-Caribe) fueron similares con los previamente definidos mediante técnicas genéticas. El grupo Pacífico-B (cuenca de Ayuquila) fue el más disímil. Nuestros resultados proveen evidencia morfológica para considerar a Agonostomus monticola como un complejo de entidades evolutivas, representadas por dos formas en la cuenca del océano Pacífico y una forma en la cuenca del océano Atlántico.(AU)

Assessing population-level morphometric variation of the Mountain Mullet Agonostomus monticola (Teleostei: Mugilidae) across its Middle American distribution

Population-level morphometric variation of the Mountain Mullet (Agonostomus monticola) was assessed in 419 adult specimens from 25 sample sites (river basins) across its Middle American distribution (Pacific and Atlantic-Caribbean drainages). This analysis was based on 36 standardized linear measurements and 19 landmarks on geometric morphometrics approach. Discriminant function analysis (DFA) revealed 19 linear morphological characters with significant variation among groups. Geometrically, the most notable changes were associated to the curvature of the frontal region of the head, the anterior and posterior insertion of the first dorsal and anal fins. The resulting grouping based on the DFA and geometric morphometrics techniques (Pacific-A, Pacific-B and NE México-Caribbean) were similar to those previously recovered by genetic techniques, where the Pacific-B (Ayuquila river basin) was the most different group. Our results provide morphological evidence for considering Agonostomus monticola as a complex of evolutionary entities, represented by two forms in the Pacific Ocean and another in the Atlantic Ocean.(AU)

La variación morfométrica de poblaciones de la lisa de montaña Agonostomus monticola fue evaluada en 419 especímenes adultos recolectados en 25 sitios (cuencas) a través de su distribución mesoamericana (Pacífico, Atlántico y cuencas del Caribe). El análisis fue basado en 36 medidas lineales estandarizadas y 19 puntos de referencia basados en morfometría geométrica. El análisis de función discriminante (AFD) reveló 19 caracteres morfométricos con variación significativa entre grupos. Geométricamente, los cambios más notables estuvieron asociados con la curvatura de la región frontal de la cabeza y la inserción anterior y posterior de la primera aleta dorsal y de la aleta anal. Los agrupamientos resultantes del AFD y del análisis de morfometría geométrica (Pacífico-A, Pacífico-B y NE México-Caribe) fueron similares con los previamente definidos mediante técnicas genéticas. El grupo Pacífico-B (cuenca de Ayuquila) fue el más disímil. Nuestros resultados proveen evidencia morfológica para considerar a Agonostomus monticola como un complejo de entidades evolutivas, representadas por dos formas en la cuenca del océano Pacífico y una forma en la cuenca del océano Atlántico.(AU)

Two new species of the genus Xenotoca Hubbs and Turner, 1939 (Teleostei, Goodeidae) from central-western Mexico.

The subfamily Goodeinae (Goodeidae) is one of the most representative and well-studied group of fishes from central Mexico, with around 18 genera and 40 species. Recent phylogenetic studies have documented a high degree of genetic diversity and divergences among populations, suggesting that the diversity of the group may be underestimated. The species Xenotoca eiseni has had several taxonomic changes since its description. Xenotoca eiseni is considered a widespread species along the Central Pacific Coastal drainages of Mexico, inhabiting six independent drainages. Recent molecular phylogenetic studies suggest that X. eiseni is a species complex, represented by at least three independent evolutionary lineages. We carried out a meristic and morphometric study in order to evaluate the morphological differences among these genetically divergent populations and describe two new species. The new species of goodeines, Xenotoca doadrioi and X. lyonsi, are described from the Etzatlan endorheic drainage and upper Coahuayana basin respectively.

Stable isotope evidence for trophic overlap of sympatric Mexican Lake Chapala silversides (Teleostei: Atherinopsidae: Chirostoma spp)

We explore the trophic role that a diverse sympatric group of fishes in the genus Chirostoma play in a large, shallow lake in central Mexico, Lake Chapala. We use δ13C and δ15N stable isotope - based food web analyses to explore how they relate to other components of the Lake Chapala ecosystem. We find five Chirostoma species in top trophic levels of the Chapala food web compared to other fishes, relying on a combination of zooplankton, fish and benthic resources as energy sources. Food web metric analyses showed generally overlapping trophic niches for members of Chirostoma, especially in terms of δ13C. However, C. jordani had lower mean δ15N isotopic values than C. promelas. As a group, "pescados blancos" (C. sphyraena and C. promelas) also had higher δ15N signatures than "charales" (C. consocium, C. jordani and C. labarcae) reflecting greater piscivory, but these differences were not strong for all food web metrics used. Trophic overlap among species of Chirostoma in Lake Chapala raises questions about the forces that might have led to a morphologically diverse but functionally similar and monophyletic group of species.(AU)

Exploramos el papel trófico de un diverso grupo de peces (género Chirostoma) que habita en simpatría en el Lago Chapala, México central. Utilizamos isótopos estables de δ13C y δ15N para explorar la relación que guardan éstos peces con otros componentes del ecosistema. Encontramos a Chirostoma en niveles altos de la red trófica de Chapala, dependiendo energéticamente de zooplankton, peces y recursos del bentos. Análisis de parámetros de la red trófica demostraron traslape de nicho trófico para cinco miembros de Chirostoma, especialmente con relación a δ13C. Sin embargo, C. jordani tuvo un menor valor promedio de δ15N que C. promelas. Al ser analizados como grupo, los "pescados blancos" (C. sphyraena, C. promelas) tuvieron niveles promedio de δ15N mayores que los "charales" (C. consocium, C. jordani, C. labarcae), indicando mayor ictiofagia, pero las diferencias no fueron significativas para todos los parámetros de red trófica utilizados. El traslape trófico entre las especies de Chirostoma en Chapala da origen a cuestionamientos acerca de las fuerzas que pueden haber intervenido en el surgimiento de un morfológicamente diverso pero funcionalmente similar grupo monofilético de peces.(AU)

Stable isotope evidence for trophic overlap of sympatric Mexican Lake Chapala silversides (Teleostei: Atherinopsidae: Chirostoma spp)

We explore the trophic role that a diverse sympatric group of fishes in the genus Chirostoma play in a large, shallow lake in central Mexico, Lake Chapala. We use δ13C and δ15N stable isotope - based food web analyses to explore how they relate to other components of the Lake Chapala ecosystem. We find five Chirostoma species in top trophic levels of the Chapala food web compared to other fishes, relying on a combination of zooplankton, fish and benthic resources as energy sources. Food web metric analyses showed generally overlapping trophic niches for members of Chirostoma, especially in terms of δ13C. However, C. jordani had lower mean δ15N isotopic values than C. promelas. As a group, "pescados blancos" (C. sphyraena and C. promelas) also had higher δ15N signatures than "charales" (C. consocium, C. jordani and C. labarcae) reflecting greater piscivory, but these differences were not strong for all food web metrics used. Trophic overlap among species of Chirostoma in Lake Chapala raises questions about the forces that might have led to a morphologically diverse but functionally similar and monophyletic group of species.

Exploramos el papel trófico de un diverso grupo de peces (género Chirostoma) que habita en simpatría en el Lago Chapala, México central. Utilizamos isótopos estables de δ13C y δ15N para explorar la relación que guardan éstos peces con otros componentes del ecosistema. Encontramos a Chirostoma en niveles altos de la red trófica de Chapala, dependiendo energéticamente de zooplankton, peces y recursos del bentos. Análisis de parámetros de la red trófica demostraron traslape de nicho trófico para cinco miembros de Chirostoma, especialmente con relación a δ13C. Sin embargo, C. jordani tuvo un menor valor promedio de δ15N que C. promelas. Al ser analizados como grupo, los "pescados blancos" (C. sphyraena, C. promelas) tuvieron niveles promedio de δ15N mayores que los "charales" (C. consocium, C. jordani, C. labarcae), indicando mayor ictiofagia, pero las diferencias no fueron significativas para todos los parámetros de red trófica utilizados. El traslape trófico entre las especies de Chirostoma en Chapala da origen a cuestionamientos acerca de las fuerzas que pueden haber intervenido en el surgimiento de un morfológicamente diverso pero funcionalmente similar grupo monofilético de peces.

Molecular systematics of the enigmatic Middle American genus Vieja (Teleostei: Cichlidae).

The genus Vieja represents a group of heroine cichlids (Teleostei: Cichlidae) distributed on the Atlantic and Pacific slopes of North and Central America from southern Mexico to Panama. Sixteen species of Vieja are presently recognized; however, based on long-standing taxonomic problems, the genus itself appears to be weakly defined. A number of different generic designations have been proposed for members of Vieja, and recent systematic studies of heroine cichlids have not specifically addressed the validity of the grouping and have not included all species in the genus. Therefore, the purpose of this study was to assess the monophyly of the genus Vieja by including all nominal species in the genus using the mitochondrial encoded cytochrome b gene and nuclear S7-1 intron. Results of Maximum Parsimony, Bayesian inference, and topology tests (constraint tree searches and post-burn-in Bayesian filtering) indicate that the genus is not monophyletic as it is currently recognized. The genus Herichthys was recovered as sister to a clade consisting of a number of Vieja species (V. fenestrata, V. guttulata, V. zonata, V. hartwegi, V. bifasciata, V. breidohri, V. argentea, V. regani, V. melanura, V. synspila, and V. maculicauda, as well as Paraneetroplusbulleri). A clade consisting of V. intermedia, V. godmanni, and V. microphthalma was recovered sister to Theraps. Additionally, V. heterospila and V. tuyrensis were recovered outside of Vieja and Herichthys clades. Based on the results of this comprehensive study, we suggest a revised classification of Vieja species.