Caleb D. McMahan

Temporal Patterns of Diversification across Global Cichlid Biodiversity (Acanthomorpha: Cichlidae)

The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

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.

Taxonomic Status of the Lago Coatepeque Endemic Convict Cichlid Amatitlania coatepeque (Teleostei: Cichlidae)

As part of a revision of the cichlid genus Archocentrus, a new genus, Amatitlania, was erected comprising four species: A. nigrofasciata (the type species), A. siquia, A. kanna, and A. coatepeque. Amatitlania coatepeque is an endemic and an eponym of Lago Coatepeque in the interior highlands of western El Salvador. This species was diagnosed by a Y-shaped pattern formed by the ventral fusion of bars four and five on the body; a triple-spined, squarish, or blunt appearance of the dentigerous arm of the dentary; the presence of a posterior projection at the dorsal corner of the lower lip; the presence of a double medial-loop in the gut; sparsely uniform pigmentation of the peritoneum, and 5–5.5 scale rows from the lateral line to the origin of the dorsal fin. Here we examined the taxonomic status of A. coatepeque using molecular and morphological characters. We found that A. coatepeque is phylogenetically nested within the clade of A. nigrofasciata. Additionally, our re-examination of the reported diagnostic morphological characters failed (even in combination) to diagnose A. coatepeque. We instead found that some of those characters were highly variable within A. coatepeque and are sometimes present in members of A. nigrofasciata. Based on our results, we conclude that A. coatepeque is a junior synonym of A. nigrofasciata. Como parte de un revisión del genero de ciclidos Archocentrus, un nuevo género (Amatitlania) fue descrito e incluye cuatro especies: A. nigrofasciata (la especie tipo), A. siquia, A. kanna, y A. coatepeque. Amatitlania coatepeque es endémica y un epónimo del Lago Coatepeque que se localiza en las tierras altas en el interior del oeste de El Salvador. Esta especie fue diagnosticada por una banda en forma-Y formada por la fusión ventral de las barras 4 y 5 en el lado del cuerpo; un dentario romo, triplemente-espinado y más o menos cuadrado; la presencia de una proyección posterior en la esquina dorsal del labio inferior; la presencia de un circulo-medial doble en el intestino, pigmentación uniformemente dispersada pero escasa en el peritoneo y 5–5.5 líneas de escamas desde la línea lateral al origen de la aleta dorsal. En este estudio con el uso de caracteres moleculares y morfológicos examinamos el estatus taxonómico de A. coatepeque. Encontramos que A. coatepeque filogenéticamente se encuentra anidada dentro de clados de A. nigrofasciata. Adicionalmente, la re-examinación de los caracteres morfológicos utilizados para diagnosticar la especies fallaron (aun en combinación) en diagnosticar A. coatepeque. Al contrario, nosotros encontramos que algunos de estos caracteres fueron altamente variables dentro de A. coatepeque y algunas veces están presentes en miembros de A. nigrofasciata. Basados en nuestros resultados nosotros concluimos que A. coatepeque es un sinónimo juvenil de A. nigrofasciata.

Description of a New Species of Killifish of the Genus Profundulus (Atherinomorpha: Profundulidae) from the Mexican State of Oaxaca

The Middle American killifish genus Profundulus occurs in most Pacific and Atlantic drainages from the Mexican state of Guerrero to the Chamelecón River in Honduras, with highest species diversity in southern Mexico. In this study, we describe a new member of the genus, Profundulus parentiae, new species, from the Mexican state of Oaxaca. It is distinguished from P. guatemalensis and P. kreiseri by having rows of dots on the sides of the body. Profundulus parentiae, new species, can be distinguished from P. oaxacae by having 33 lateral scales, versus 29–31 in P. oaxacae. Profundulus parentiae, new species, can be distinguished from P. balsanus, P. oaxacae, and P. mixtlanensis by the presence of long epiotic processes that extend beyond the epipleural ribs of the first vertebra, versus short epiotic processes not reaching the epipleural ribs of the first vertebra. Profundulus parentiae, new species, can be differentiated from P. punctatus by the presence of a dorso-ventrally compressed Meckels cartilage with a relatively straight medial process and a narrow and strongly concave sesamoid articular, versus a dorso-ventrally expanded Meckels cartilage with concave medial process and a wide and moderately concave sesamoid articular. Based on the phylogenetic analysis of molecular sequence data, the new species is recovered as the sister taxon to P. balsanus. The discovery and description of this new species in southeastern Mexico, raises the number of species from this region to five and suggests that this area has been an important center for diversification within this lineage of killifishes.

A new species of Roeboides (Teleostei: Characidae) from Costa Rica and Panama, with a key to the middle American species of the genus

A new species of Roeboides is described from the Pacific slope of Costa Rica and Panama. Roeboides bussingi differs from all other Central American Roeboides and all members of the R. guatemalensis species group by the following combination of characters: presence of 18-22 scales above the lateral line (vs. 12-16 in R. dientito); 15-22 scales below the lateral line (vs. 10-14 in R. dientito, and 20-24 in R. loftini); an inconspicuous, sometimes absent, crescent-shaped humeral spot (vs. a large round, conspicuous humeral spot in R. carti, R. dayi, R. dientonito, R. ilseae, R. loftini, and R. occidentalis); a small wedge-shaped spot that does not reach the lateral line (vs. a large spot crossing the lateral line in R. guatemalensis); a teardrop shaped caudal spot (vs. caudal spot triangle shaped in R. bouchellei); and a dark band at the distal tip of the anal fin (vs. dark band absent in R. bouchellei). A key to all Middle American species of Roeboides is also presented. Uma especie nova de Roeboides e descrita da vertente pacifica da Costa Rica e Panama. Roeboides bussingi difere de todas as outras especies de Roeboides da America Central e de todos os membros do grupo R. guatemalensis pela seguinte combinacao de caracteres: presenca de 18-22 escamas acima da linha lateral (vs. 12-16 em R. dientito); 15-22 escamas abaixo da linha lateral (vs. 10-14 em R. dientito e 20-24 em R. loftini); mancha umeral inconspicua, as vezes ausente, no formato de meia lua (vs. mancha humeral conspicua e arredondada em R. carti, R. dayi, R. dientonito, R. ilseae, R. loftini e R. occidentalis); pequena mancha em forma de cunha, nao alcancando a linha lateral (vs. mancha grande, atravessando a linha lateral em R. guatemalensis); mancha do pedunculo caudal em formato de gota d’agua (vs. mancha caudal com formato triangular em R. bouchellei); banda escura na margem distal da nadadeira anal (vs. banda escura ausente em R. Bouchellei). Uma chave para todas as especies de Roeboides da America Media e fornecida.