No description available.

Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Includes bibliographical references (leaves 110-117).

Tesis entregada a la Universidad de Chile en cumplimiento parcial de los requisitos para optar al grado de Doctora en Ciencias con Mención en Ecología y Biología Evolutiva. / Durante el proceso continuo de la especiación se genera la divergencia genética y el establecimiento del aislamiento reproductivo. La descripción de los patrones genéticos de diferenciación entre pares de taxa cercanamente relacionados en diferentes etapas de este continuo podría ayudar a determinar la proporción del genoma que contribuye a la divergencia y la naturaleza de los genes involucrados. En el contexto de especiación alopátrica, se espera que la magnitud del primer aspecto sea proporcional al tiempo de divergencia, mientras que la deriva génica debería hacer aparecer mutaciones al azar en el genoma, afectando a diferentes regiones génicas e intergénicas en diferentes etapas del continuo de especiación. En esta tesis se describen los patrones de divergencia genómica entre dos pares de especies chilenas del género Orestias, pupfishes que habitan el Altiplano de Chile, Perú y Bolivia, que se encuentran en etapas diferentes del continuo de especiación. En una etapa inicial de este proceso se encuentran O. chungarensis y O. laucaensis, ambas presentes en ambientes aislados (Lago Chungará y Río Lauca, respectivamente). Por otra parte, en una etapa tardía se encuentran O. ascotanensis y O. gloriae, quienes habitan en vertientes de salares cercanos, pero desconectados (salar Ascotán y salar Carcote, respectivamente). Por una parte, debiera existir mayor diferenciación genómica entre las especies de la etapa más avanzada que entre las especies de la etapa más reciente. Por otra parte, y dado que estas especies se originaron en un contexto de especiación alopátrica que se ha mantenido hasta el presente, los patrones de divergencia genómica en cada par de especies debieran haber seguido rutas independientes. Se aplicó la técnica RAD-Seq, un tipo de secuenciación genómica de representación reducida, a los individuos muestreados de las cuatro especies. Los análisis de estructuración genética detectaron una 17 fuerte divergencia entre las especies de los salares y entre éstas y O. chungarensis y O. laucaensis, y una divergencia mucho menor entre éstas últimas. Los niveles de diferenciación global, medidos con el índice FST, indicaron que las especies recientes se han diferenciado tres veces menos que las especies más divergentes. Además se observó que ~20% de los loci totales se diferencia entre las especies recientes, mientras que esa cantidad aumenta a ~50% entre especies divergentes. Estos loci no estarían concentrados en ninguna región en particular, sino que se encontrarían distribuidos a lo largo de todo el genoma. Los análisis del número total de SNPs y de SNPs que más diferencian a las especies indicaron que estos polimorfismos son particulares de cada especie al igual que las funciones biológicas en las que están involucrados. Estos resultados permitieron observar empíricamente cómo el grado de divergencia a nivel genómico aumenta a medida que se avanza en el continuo de especiación, tanto a nivel de diferenciación global, como de la diferenciación de cada locus, y que el proceso de diferenciación ha seguido un camino independiente en cada una de las especies y pares de especies, lo cual es concordantes con un modelo de especiación alopátrica. / During the continuum process of speciation the genetic diversity is generated and the reproductive isolation is stablished. The description of genomic patterns of differentiation from pairs of closely related taxa at different stages of this continuum would help identify the proportion of the genome that contributes to the divergence and the nature of the genes involved. In an allopatric speciation context, it is expected that the magnitude of the first aspect is proportional to divergence time, while the genetic drift would give rise mutations randomly in the genome affecting therefore different genic and intergenic regions at different stages of the speciation continuum. This study described the genomic patterns of divergence between two pairs of Chilean species of the genus Orestias at different stages of the speciation continuum. An initial stage involves O. chungarensis and O. laucaensis, both inhabiting isolated environments (Lake Chungara and Lauca River, respectively). On the other hand, O. ascotanensis and O. gloriae represent a late stage of this continuum. They both inhabit close, unconnected salt pans (Ascotan and Carcote salt pan, respectively). On one hand, there should be a higher genomic differentiation between species of the late stage than species of the recent stage. On the other hand, and given these species were originated in an allopatric speciation context that persist until today, then the patterns of genomic divergence of each species pair should have follow different and independent paths. We obtained RAD-Seq data, a reduced representation sequencing technique, from individuals of each of these species. Genetic structure analyses found a deep divergence between salt pans samples and between these and O. chungarensis and O. laucaensis samples, and much less divergence between these last two. 19 Overall FST values, as a measure of genetic differentiation, are three times higher between the distant species than the close related pair of species. Moreover, ~20% of the loci are differentiated between O. chungarensis and O. laucaensis, while ~50% of the total loci are differentiated between the distant species, and these loci are not concentrated in any specific region, but distributed along the whole genome. Analyses of the total number of SNPs and the SNPs that more differentiate the species indicate that the polymorphisms are particular of each species, as well as the biological functions they are associated with. These results allowed to empirically observing how the genomic divergence increase as the speciation continuum advance, at both overall differentiation and differentiation of locus-by-locus, and that the differentiation process has followed an independent path in each of species and species pairs, in concordance with an allopatric speciation model. / FONDECYT 1140540 y FONDECYT 1140543, Dr. Miguel Allende y al Centro de Regulación del Genoma FONDAP- CRG-1509007, Beca de Doctorado Nacional otorgada por CONICYT, CONICYT-PCHA/doctorado Nacional/2012-21120972.

The reproductive and developmental styles of Aplocheilichthys johnstoni closely resemble those of other oviparous cyprinodont fishes reported in the literature. Reproductively it sorts to the guild of nonguarding phytophyllic broodhiders, is a daily, fractional spawner of relatively large, adhesive eggs. The length of the embryonic period varies between 14 and 19 days and the larval period can last for up to 30 days. Sexual maturity can be attained at an age of 150 days from fertilization. The embryology is described in detail and close comparison is made with the embryology of other cyprinodonts to highlight possible phylogenetic differences. Major differences with other cyprinodonts are in the rate of development, and heterochronic shifts in the appearance of certain structures in relation to each other. A discussion is included on the nature of development. It is suggested that development proceeds in a gradual stepwise fashion, interspersed with four major saltations, namely, fertilisation, onset of exogenous feeding, sexual maturity and death

Karyotypes of nine species of Venezuelan annual killifishes were compared. Karyotypic differences were found between species and between some genera. A chromosomal sexual dimorphism was found in <u>Pterolebias hoignei</u> (2N = 46). Males of this species possess a single large "Y" chromosome. No chromosomal divergence was detected among conspecific populations from different localities. <u>Pterolebias hoignei</u> and <u>Pterolebias zonatus</u> were found to differ both in diploid number (46 and 42 respectively) and in metacentric chromosome number (6 and 12 respectively). All <u>Rachovia</u>species were found to have a diploid number of 44. <u>Rachovia maculipinnis</u>and <u>R. brevis</u> were found to differ from one another in metacentric chromosome number (20 and 12 respectively). <u>Rachovia hummelincki</u> and <u>R. pyropunctata</u> both possess metacentric chromosome counts of 10. No karyotypic differences were found between <u>Austrofundulus transilis</u> and <u>Austrofundulus limnaeus</u> (2N = 44, metacentrics = 12). Several populations of the latter although divergent in male color patterns, did not differ karyotypically. All species examined, except <u>Rivulus stellifer</u>, departed from the presumptive ancestral teleost diploid number of 48. The degree of chromosomal variation appears not to be as high among the New World as among the Old World annuals. This difference among lineages with similar life histories and reproductive strategies suggests that stochastic events have not played a major role in mediating chromosomal divergence in annual fishes. / Master of Science

Drastic alterations to the North American Southwest’s hydrology have highly influenced resident fish communities. In New Mexico and Texas, the Pecos River has been severely altered as a result of water manipulation, isolating backwaters and various habitats that were once connected to the main river. Cyprinodon pecosensis (Pecos pupfish) has been highly impacted due to the effects of anthropogenic water manipulation, as well as species introductions. Cyprinodon pecosensis populations have become isolated and scattered, residing in sinkholes, remnant lakes, and static backwaters, thus creating numerous micropopulations. The purpose of this study was to assess the morphological variation in cranial features that occur in response to varied habitats, especially in terms of environmental factors and species co-occurrence. Landmark-based geometric morphometrics was used to assess shape variation across the aforementioned micropopulations comprising four general habitat types and 27 different localities, each with varied community structure and salinity. Results from this study suggest that head and mandible morphology vary temporally, with year to year variation, as well as among different localities. The head morphology of C. pecosensis was most heavily influenced by habitat type and localities within habitat types, but was largely canalized with the exception of localities classified as deep sinkholes. Year to year variation and localities among habitat types were the most influential factors associated with mandible morphology, but there was strong overlap among the convex hulls that defined regions of morphospace for habitat types. As C. pecosensis is a threatened species, this research has important implications for future conservation and management. Additionally, these results could further aid in the understanding of preserving species in fragmented landscapes.

No description available.

This paper investigates a means of detecting the reaction of aquatic vertebrates to environmental change by recording behavioral patterns within the diurnal activity. An apparatus measuring the activity of Jordanella floridae, Goode and Bean, using a photoelectric sensor system is described. Individual sensors monitored specific areas of the test aquarium that had special significance to the fish in the way of a particular behavioral category. An event recorder documented the breakage of light beams, giving continuous and accurately timed data of activity. Two distinct patterns of activity were recognized; a control, or typical, pattern, and a pattern resulting from the administration of a large (10°C) change in environmental temperature. Modifications in the diurnal behavior were consistent with reactions that could be adaptive for the species under similar conditions in nature.

The hermaphroditic fish, Rivulus marmoratus, is the only vertebrate known to reproduce by internal self-fertilization; this process results in populations of homozygous clones. Most natural populations consist entirely of hermaphrodites, but phenotypically distinct, fertile males occur at frequencies up to 24% on some islands off the coast of Belize. The presence of large numbers of males in natural populations prompted this study to determine if males are involved in the mating system. The occurrence of cross-fertilization between males and hermaphrodites was determined by surveying progeny of field-caught hermaphrodites for non-segregation or segregation of DNA fingerprint markers as an indication of the homozygosity or heterozygosity of the parent. DNA fingerprinting revealed no segregation of markers among the offspring in 12 of 12 Florida and Brazil laboratory lines and in 5 of 30 Belize Cay broods. These data indicate that the hermaphrodite parents were homozygous; thus, no detectable outcrossing has occurred in these populations. However, DNA fingerprinting revealed segregation of markers among the offspring in 25 of 30 Belize Cay broods. Twenty-four of these broods were from the island of Twin Cays. An average of 30% of the parental bands were segregating among the offspring; values ranged from 0.09 to 0.50. Offspring were, on average, 8% dissimilar to one another; values ranged from 2.08% to 15.09%. These data suggest that the 25 hermaphrodite parents were heterozygous; thus, males are involved in the mating system in some Belize Cay populations. These data are the first evidence of outcrossing in this species. / Master of Science