Mitochondrial DNA variation in pupfishes assigned to the species Cyprinodon macularius (Atherinomorpha : Cyprinodontidae): Taxonomic implications andconservation genetics

Variation in mitochondrial DNA (mtDNA) was assessed in a captive stock and 11 wild populations (n = 259) from throughout the native range of Desert Pu pfish Cyprinodon macularius as traditionally understood. Using PCR-SSCP, 18 composite haplotypes were identified from a 333-bp segment of the mitochon drial D-loop and two segments of the ND2 gene (333 and 325 bp). Representat ives of each haplotype were sequenced for the entire ND2 gene and the 337-b p segment of the D-loop. Phylogenetic analyses revealed that haplotypes for m two monophyletic groups, one in the Rio Sonoyta/Qllitobaquito Springs are a and one in the Salton Sea/Colorado River Delta. This, with previous obser vations on morphology, color pattern, and geological history, supports reco gnition of the Rio Sonoyta/Quitobaquito populations as a separate species, the Quitobaquito Pupfish C. eremus Miller and Fuiman, from the more widespr ead desert pupfish C. macularius Baird and Chard. More than 70% of mtDNA di versity across all populations was attributable to differences between the two species. Within species, the average local population contains 94% and 97% of the diversity in, respectively, C. eremus and C. macularius. Differe nces between the Salton Sea and Colorado River Delta populations of C. macu larius ex plain a small (3.7%), but statistically significant, portion of m tDNA diversity in this species. This and the history of connections between Salton Sea and the delta suggest that the two regions should be managed se parately with no intermixing of pupfish other than what occurs when the pre sent, human-regulated hydrology is overcome by natural flooding. Haplotype frequencies in C. eremus from Quitobaquito Springs and Rio Sonoyta were not significantly different. However, the potentially long history of isolatio n between these two populations and evidence of some degree of morphologica l divergence indicate a need for conservative management with no intermixin g The captive stock exhibited reduced mtDNA variation relative to its wild parent population from a locality on the delta. Variacion de ADNmt fue examinado por una cepa de cautivo y 11 poblaciones s ilvestres (n = 259) de todas partes del rango natural del cachorrito del de sierto Cyprinodon macularius como entendido tradicionalmente. Utilizando PC R-SSCP, 18 haplotipos compuestos fueron identificados desde un segmento de 337-pb del D-loop mitocondrial y dos segmentos del gene DN2 (333 ph y 325 p b). Representantes de cada haplotipo fueron sequenciados por el gene DN2 en tero y el segmento de 337-pb del D-loop. Analisis filogenetico mostro una r elacion monofiletica reciproca ent-e poblaciones de dos regiones generales, Rio Sonoyta/Quitobaquito y Salton Sea/Delta del Rio Colorado. Esto, con ob servaciones previas de morfologia, patron de color, y la historia geologica , sostiene el reconocimiento de las poblaciones de Rio Sonoyta/Quitobaquito come ma especie distinta, el cachorrito de Quitobaquito C. eremus Miller a nd Fuiman, de la especie con una distribucion mb amplia, el cachorrito del desierto C. macularius Baird and Chard. Mb de 70% de la diversidad ADNmt de todas las poblaciones fue atribuida a diferencias entre las dos especies. Dentro de cada especie, la poblacion promedia local contiene 94% y 97% de l a diversidad de, respectivamente, C. eremus y C. macularius. Las diferencia s entre las poblaciones de C. macularius del Salton Sea y las de la Delta d el Rio Colorado explican una pequena (3.7%) pero ma porcion estadisticament e significativa de la diversidad ADNmt de esta especie. Esto y la historia de conecciones entre el Salton Sea y la delta sugieren que los dos regiones deben ser manejadas aparte sin mezclar a los cachorritos mb que lo que ya ocurre cuando la hidrologia actual controlada por los humanos, esta conquis tada por inundaciones naturales. Frequencias de los haplotipos en C. eremus del Quitobaquito Springs y el Rio Sonoyta no fueron sig-. (C) 2000 by the American Society of Ichthyologists and Herpetologists