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Robert C. Vrijenhoek - One of the best experts on this subject based on the ideXlab platform.
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A new species of the live-bearing fish genus Poeciliopsis from northern Mexico (Cyprinodontiformes, Poeciliidae).
ZooKeys, 2019Co-Authors: Kevin W. Conway, Mariana Mateos, Robert C. VrijenhoekAbstract:Poeciliopsis jackschultzi sp. nov., is described based on seven specimens (17.9-26.7 mm SL) from the Rio Concepcion (also known as Rio Magdalena), Sonora, Mexico. The new species belongs to the Leptorhaphis species group and can be distinguished from other members of this group by features of the skeleton and colouration. The new species is sympatric with P. occidentalis, a hybridogenetic all-female biotype P. monacha-occidentalis, and hybrids between P. monacha-occidentalis females and P. jackschultzi males. The distribution of P. jackschultzi is highly restricted, and the main habitat, spring-fed marshy streams and pools, is susceptible to loss and degradation in a desert environment with increasing human water demand.
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Complete mitochondrial genome of the headwater livebearer, Poeciliopsis monacha: the mother of clones
Mitochondrial DNA. Part B Resources, 2016Co-Authors: Yeon Seon Jeon, Shannon B. Johnson, Yong-jin Won, Robert C. VrijenhoekAbstract:The sexually reproducing fish, Poeciliopsis monacha (Actinopterygii, Cyprinodontiformes, Poeciliidae), is the maternal ancestor of six hybrid biotypes that reproduce clonally. The gene content and order of its 16,818 bp mitochondrial genome is virtually identical with that of other sexually reproducing poeciliid fishes, providing no evidence for a mitochondrial involvement in the origins of all-female reproduction.
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AMER. ZOOL, 19:787-797(1979). Factors Affecting Clonal Diversity and Coexistence
2015Co-Authors: Robert C. VrijenhoekAbstract:SYNOPSIS. Recent genetic studies of asexually reproducing fishes in the genus Poeciliopsis (Poeciliidae) revealed abundant variation in the form of multiple sympatric clones. Recur-rent hybridizations between sexual species provides the principal source of clonal variation. The hybrids are spontaneously endowed with a clonal reproductive mechanism that per-petuates a high level of heterozygosity. Migration within and between river systems, and mutations, also contribute to clonal diversity in " these fish. Coexistence among different clones and with the sexual ancestors depends in part upon specializations characteristic of individual clones. Clonal reproduction is an efficient mechanism for freezing a portion of the niche-width variation contained in the gene pool of the more broadly adapted, sexual ancestors. Multiclonal populations achieve significantly higher densities relative to the sexual forms than do monoclonal populations. This relationship is a function of the clonal variability upon which natural selection can act and upon the capacity of a multiclonal population to better exploit a heterogeneous environment through niche diversification. In all-female organisms such as Poeciliopsis, which are dependent upon sexual species for insemination, competitive abilities probably are at a premium in the densely populated pools and arroyos of the Sonoran Desert. Competitive abilities are probably less important for truly parthenogenetic clones which rely on colonization abilities to escape from their sexual ancestors and from other clones
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Independent Origins of Allotriploidy in the Fish Genus Poeciliopsis
The Journal of heredity, 2004Co-Authors: Mariana Mateos, Robert C. VrijenhoekAbstract:We examined mitochondrial DNA (mtDNA) sequences and allozymes to assess possible modes of origin, clonal diversity, and evolutionary age in a triploid all-female fish of the genus Poeciliopsis from the state of Sinaloa, Mexico. Analysis of multilocus allozymes revealed that the Rio Mocorito biotype (Poeciliopsis monacha-lucida-viriosa) is trihybrid, carrying haploid genomes from three sexually reproducing species, Poeciliopsis monacha, Poeciliopsis lucida, and Poeciliopsis viriosa. Composite allozyme and mtDNA genotypes identified four clones, all bearing closely related mitochondrial haplotypes originally derived from P. monacha. Apparently these trihybrids arose endemically by addition of a haploid genome from P. viriosa, a local sexual species, to an allodiploid biotype, P. monacha-lucida, also found in the Rio Mocorito. The present analysis clearly revealed that P. monacha-lucida-viriosa arose independently of the two allotriploid biotypes that live in a river to the north (Rio Fuerte). Although the origins of allotriploidy in Poeciliopsis are less constrained phylogenetically and geographically than previously thought, known triploid biotypes all had relatively recent origins, which supports the notion that most asexual lineages are evolutionarily short-lived.
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HISTORICAL BIOGEOGRAPHY OF THE LIVEBEARING FISH GENUS Poeciliopsis (POECILIIDAE: CYPRINODONTIFORMES)
Evolution; international journal of organic evolution, 2002Co-Authors: Mariana Mateos, Oris I. Sanjur, Robert C. VrijenhoekAbstract:To assess the historical biogeography of freshwater topminnows in the genus Poeciliopsis, we examined sequence variation in two mitochondrial genes, cytochrome b (1140 bp) and NADH subunit 2 (1047 bp). This wide- spread fish genus is distributed from Arizona to western Colombia, and nearly half of its 21 named species have distributions that border on the geologically active Trans-Mexican Volcanic Belt (TMVB), a region that defines the uplifted plateau (Mesa Central) of Mexico. We used the parametric bootstrap method to test the hypothesis that a single vicariant event associated with the TMVB was responsible for divergence of taxa found to the north and south of this boundary. Because the single-event hypothesis was rejected as highly unlikely, we hypothesize that at least two geological events were responsible for divergence of these species. The first (8-16 million years ago) separated ancestral populations that were distributed across the present TMVB region. A second event (2.8-6.4 million years ago) was associated with northward dispersal and subsequent vicariance of two independent southern lineages across the TMVB. The geological history of this tectonically and volcanically active region is discussed and systematic implications for the genus are outlined.
J. Jaime Zúñiga-vega - One of the best experts on this subject based on the ideXlab platform.
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Superfetation in live-bearing fishes is not always the result of a morphological constraint
Oecologia, 2016Co-Authors: Patricia Frías-alvarez, J. Jaime Zúñiga-vegaAbstract:Superfetation is an unusual reproductive strategy that consists of the presence of multiple broods at different developmental stages within a single female. One hypothesis that was proposed to explain its adaptive significance suggests that, in fishes, superfetation is a response to selective pressures that promote a thin and streamlined body shape, such as high-velocity water systems. Superfetation may allow for reduction in ovary size and hence improve streamlining because superfetating females carry few large, full-term embryos at any given time. We tested this morphological constraint hypothesis using reproductive and morphological data from several populations of two viviparous fishes of the family Poeciliidae ( Poeciliopsis gracilis and Poeciliopsis infans ). We found no evidence to support the morphological constraint hypothesis. In both species the degree of superfetation varied as a function of a complex interaction between source population and female size, and this interpopulation variation was not associated with the velocity of the water current. Contrary to what we expected, females of P. gracilis with more streamlined bodies were observed in rivers where water velocity is slow or moderate. In P. infans the velocity of the water current did not predict variation in body shape. Our results are noteworthy because a previous study which focused on a congeneric species ( Poeciliopsis turrubarensis ) demonstrated strong support for this hypothesis. However, based on our evidence we conclude that the association among increased superfetation, streamlined morphologies, and fast-flowing environments is not a general rule and that the adaptive value of superfetation may differ among species.
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Spatial and temporal variation in superfoetation and related life history traits of two viviparous fishes: Poeciliopsis gracilis and P. infans.
Die Naturwissenschaften, 2014Co-Authors: Patricia Frías-alvarez, Constantino Macías Garcia, Luis F. Vázquez-vega, J. Jaime Zúñiga-vegaAbstract:Superfoetation is the ability of females to simultaneously bear multiple broods of embryos at different developmental stages. Most studies on the phylogenetic distribution of superfoetation and on the factors that potentially promote superfoetation ignore variation within species. Here, we studied 11 populations of two species of viviparous fishes of the family Poeciliidae (Poeciliopsis gracilis and Poeciliopsis infans) and document wide variation in superfoetation and in three related life history traits: brood size, individual embryo mass and total reproductive allotment. We found significant differences in the average number of simultaneous broods among populations of P. gracilis but not among populations of P. infans. In addition, we found even greater variation between months within populations for both species, although no specific pattern of temporal variation was evident. Instead of the expected consistency of seasonal differences in superfoetation across populations, we found that large variation among months within seasons and the amount and direction of this monthly variation differed widely between populations. Our results emphasize the importance of including intraspecific variation in superfoetation and other life history traits in studies that aimed at finding general explanations of life history trait evolution.
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Mortality rates in two populations of the viviparous fish Poeciliopsis baenschi (Teleostei: Poeciliidae)
Revista Mexicana de Biodiversidad, 2013Co-Authors: Alejandro Molina-moctezuma, J. Jaime Zúñiga-vega, Hector Espinosa-perezAbstract:Mortality is one of the most important demographic features. Measures of size- or sex-specific mortality can help to explain local selective pressures and can also be used to construct demographic models that estimate population trends. This study estimated mortality rates for 2 populations of a viviparous freshwater fish, endemic to western Mexico (Poeciliopsis baenschi). We found that mortality was size- and sex-dependent and different between both populations. We compared our findings with mortality rates previously estimated for other populations of this species.
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POPULATION ABUNDANCE AND SEX RATIO OF THE VIVIPAROUS FRESHWATER FISH Poeciliopsis BAENSCHI (POECILIIDAE) THROUGHOUT ITS RANGE IN WESTERN MEXICO
Western North American Naturalist, 2012Co-Authors: J. Jaime Zúñiga-vega, Alejandro Molina-moctezuma, Ana L. Hernández-rosas, Hibraim Adán Pérez-mendoza, Fernanda R. Rodríguez-reyes, Yolotzin M. Bravo-espinosa, Hector Espinosa-perezAbstract:We estimated population abundance and sex ratio for a freshwater live-bearing fish species (Poeciliopsis baenschi) that inhabits fluvial systems in western Mexico. We conducted mark-recapture experiments in 6 distinct popu- lations. We used both our catch data as well as estimates of capture probability to calculate the number of individuals per unit water volume for adult males, adult females, and juveniles. Overall, abundance varied among sites from 23.8 individuals ⋅ m-3 to 363.2 individuals ⋅ m-3. In most of our study sites, the estimated sex ratio was markedly biased toward females (up to 11 females per male). We discuss the potential causes and implications of the observed demo- graphic features. RESUMEN.—Estimamos abundancia poblacional y proporcion sexual para una especie de pez viviparo de agua dulce (Poeciliopsis baenschi) que habita sistemas fluviales en el occidente de Mexico. Llevamos a cabo experimentos de mar- caje y recaptura en seis poblaciones distintas. Utilizamos tanto nuestras capturas observadas asi como estimaciones de probabilidad de captura para calcular el numero de individuos por unidad de volumen de agua para machos adultos, hembras adultas y juveniles. En general, la abundancia vario entre sitios desde 23.8 individuos por m3 y hasta 363.2 individuos por m3. En la mayoria de nuestros sitios de estudio, la proporcion sexual estimada estuvo marcadamente ses- gada hacia las hembras (hasta 11 hembras por cada macho). Discutimos las causas potenciales y las implicaciones de los rasgos demograficos observados.
Mariana Mateos - One of the best experts on this subject based on the ideXlab platform.
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A new species of the live-bearing fish genus Poeciliopsis from northern Mexico (Cyprinodontiformes, Poeciliidae).
ZooKeys, 2019Co-Authors: Kevin W. Conway, Mariana Mateos, Robert C. VrijenhoekAbstract:Poeciliopsis jackschultzi sp. nov., is described based on seven specimens (17.9-26.7 mm SL) from the Rio Concepcion (also known as Rio Magdalena), Sonora, Mexico. The new species belongs to the Leptorhaphis species group and can be distinguished from other members of this group by features of the skeleton and colouration. The new species is sympatric with P. occidentalis, a hybridogenetic all-female biotype P. monacha-occidentalis, and hybrids between P. monacha-occidentalis females and P. jackschultzi males. The distribution of P. jackschultzi is highly restricted, and the main habitat, spring-fed marshy streams and pools, is susceptible to loss and degradation in a desert environment with increasing human water demand.
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A multilocus phylogeny of the fish genus Poeciliopsis: Solving taxonomic uncertainties and preliminary evidence of reticulation.
Ecology and evolution, 2019Co-Authors: Mariana Mateos, Omar Domínguez-domínguez, Alejandro Varela-romeroAbstract:The fish genus Poeciliopsis constitutes a valuable research system for evolutionary ecology, whose phylogenetic relationships have not been fully elucidated. We conducted a multilocus phylogenetic study of the genus based on seven nuclear and two mitochondrial loci with a thorough set of analytical approaches, that is, concatenated (also known as super-matrix), species trees, and phylogenetic networks. Although several relationships remain unresolved, the overall results uncovered phylogenetic affinities among several members of this genus. A population previously considered of undetermined taxonomic status could be unequivocally assigned to P. scarlli; revealing a relatively recent dispersal event across the Trans-Mexican Volcanic Belt (TMVB) or Pacific Ocean, which constitute a strong barrier to north-south dispersal of many terrestrial and freshwater taxa. The closest relatives of P. balsas, a species distributed south of the TMVB, are distributed in the north; representing an additional north-south split in the genus. An undescribed species of Poeciliopsis, with a highly restricted distribution (i.e., a short stretch of the Rio Concepcion; just south of the US-Mexico border), falls within the Leptorhaphis species complex. Our results are inconsistent with the hypothesis that this species originated by "breakdown" of an asexual hybrid lineage. On the other hand, network analyses suggest one or more possible cases of reticulation within the genus that require further evaluation with genome-wide marker representation and additional analytical tools. The most strongly supported case of reticulation occurred within the subgenus Aulophallus (restricted to Central America), and implies a hybrid origin for P. retropinna (i.e., between P. paucimaculata and P. elongata). We consider that P. balsas and P. new species are of conservation concern.
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Comparative phylogeography of livebearing fishes in the genera Poeciliopsis and Poecilia (Poeciliidae: Cyprinodontiformes) in central Mexico
Journal of Biogeography, 2005Co-Authors: Mariana MateosAbstract:Aim To test the hypothesis that the vicariant event responsible for north–south divergences in two clades of the fish genus Poeciliopsis Regan was also responsible for north–south divergences in the fish Poecilia butleri Jordan. Location Central Mexico. Methods Parsimony, distance, maximum likelihood and Bayesian phylogenetic analyses of a mitochondrial gene. Molecular clock test and Bayesian analyses of divergence time. Results We report concordant phylogeographical patterns between two clades in the genus Poeciliopsis (i.e. the other formed by P. latidens Garman and P. fasciata Meek, and the other formed by P. presidionis Jordan and P. turneri Miller) and the clade of Poecilia butleri, with northern and southern individuals within each clade grouping into separate lineages. There is also evidence for slower substitution rates in Poecilia compared with Poeciliopsis. After taking into account these substitution rate discrepancies with Bayesian relaxed molecular clock analyses, north–south divergences in Poecilia butleri were equivalent to those reported for Poeciliopsis latidens-fasciata and P. presidionis-turneri. Main conclusions The same Plio-Pleistocene vicariant event associated with geological activity of the Trans-Mexican Volcanic Belt (TMVB) appears to have caused divergence in three different freshwater fish lineages. This study is an example of how comparative phylogeography can strengthen inferences about vicariant events in regions of high biological diversity and complex geological history such as the TMVB.
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Independent Origins of Allotriploidy in the Fish Genus Poeciliopsis
The Journal of heredity, 2004Co-Authors: Mariana Mateos, Robert C. VrijenhoekAbstract:We examined mitochondrial DNA (mtDNA) sequences and allozymes to assess possible modes of origin, clonal diversity, and evolutionary age in a triploid all-female fish of the genus Poeciliopsis from the state of Sinaloa, Mexico. Analysis of multilocus allozymes revealed that the Rio Mocorito biotype (Poeciliopsis monacha-lucida-viriosa) is trihybrid, carrying haploid genomes from three sexually reproducing species, Poeciliopsis monacha, Poeciliopsis lucida, and Poeciliopsis viriosa. Composite allozyme and mtDNA genotypes identified four clones, all bearing closely related mitochondrial haplotypes originally derived from P. monacha. Apparently these trihybrids arose endemically by addition of a haploid genome from P. viriosa, a local sexual species, to an allodiploid biotype, P. monacha-lucida, also found in the Rio Mocorito. The present analysis clearly revealed that P. monacha-lucida-viriosa arose independently of the two allotriploid biotypes that live in a river to the north (Rio Fuerte). Although the origins of allotriploidy in Poeciliopsis are less constrained phylogenetically and geographically than previously thought, known triploid biotypes all had relatively recent origins, which supports the notion that most asexual lineages are evolutionarily short-lived.
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Independent Origins and Rapid Evolution of the Placenta in the Fish Genus Poeciliopsis
Science (New York N.Y.), 2002Co-Authors: David N. Reznick, Mariana Mateos, Mark S. SpringerAbstract:The evolution of complex organs is a source of controversy because they require the contributions of many adaptations to function properly. We argue that placentas are complex, that they have evolved multiple times in Poeciliopsis, and that there are closely related sister taxa that have either no placentas or intermediate stages in the evolution of a placenta. Furthermore, placentas can evolve in 750,000 years or less, on the same time scale as suggested by theoretical calculations for the evolution of complex eyes. Independent origins of such complexity, accompanied by sister taxa that either lack or have intermediate stages in the evolution of the trait, present an opportunity to study the evolution of novelty and complexity from a comparative, evolutionary perspective.
Jerald B. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Sympatry Predicts Spot Pigmentation Patterns and Female Association Behavior in the Livebearing Fish Poeciliopsis baenschi
PloS one, 2017Co-Authors: Andrea J. Roth-monzón, Laura E. Scott, Ashley A. Camargo, Eliza I. Clark, Eric E. Schott, Jerald B. JohnsonAbstract:In this study, we explored the possibility that differences in pigmentation patterns among populations of the fish Poeciliopsis baenschi were associated with the presence or absence of the closely related species P. turneri. If reproductive character displacement is responsible, spotting patterns in these two species should diverge in sympatry, but not allopatry. We predicted that female P. baenschi from sympatric sites should show a preference for associating with conspecifics vs. heterospecific males, but females from allopatric sites should show no such preferences. To evaluate these predictions, we compared spotting patterns and female association behaviors in populations of P. baenschi from Central Mexico. We found that both of our predictions were supported. Poeciliopsis baenschi that co-occured with P. turneri had spotting patterns significantly different than their counterparts from allopatric sites. Using a simultaneous choice test of video presentations of males, we also found that female P. baenschi from populations that co-occured with P. turneri spent significantly more time with males of their own species than with P. turneri males. In contrast, females from allopatric populations of P. baenschi showed no differences in the amount of time they spent with either conspecific or heterospecific males. Together, our results are consistent with the hypothesis that reproductive character displacement may be responsible for behavioral and spotting pattern differences in these populations of P. baenschi.
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What can phylogeographic breaks in the livebearer Poeciliopsis turrubarensis tell about fish community boundaries in western Costa Rica
Journal of fish biology, 2012Co-Authors: A. D. Larson, P. L. Scarborough, Casey L. Sayre, Jerald B. JohnsonAbstract:This study asks if the geographic boundary delineating two fish communities in western Costa Rica is congruent with a phylogeographic break in a single widespread fish species Poeciliopsis turrubarensis (Poeciliidae) that spans this area. Such congruence would suggest that a common historical event (e.g. geological or climatic) could be responsible for both patterns. It was found that there was a shared break across a region in central Costa Rica suggesting a common cause may be responsible for both the abrupt shift in fish community composition and the genetic break in P. turrubarensis.
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Does sympatry predict life history and morphological diversification in the Mexican livebearing fish Poeciliopsis baenschi
Biological Journal of the Linnean Society, 2010Co-Authors: Laura E. Scott, Jerald B. JohnsonAbstract:Understanding why some species coexist and others do not remains one of the fundamental challenges of ecology. Although there is evidence to suggest that closely-related species are unlikely to occupy the same habitat because of competitive exclusion, there are many cases where closely-related species do co-occur. Research comparing sympatric and allopatric populations of co-occurring species provides a framework for understanding the role of phenotypic diversification in species coexistence. In the present study, we compare phenotypic divergence between sympatric and allopatric populations of the livebearing fish, Poeciliopsis baenschi. We focus on life-history traits and body shape, comprising two sets of integrated traits likely to diverge in response to varying selective pressures. Given that males and females can express different phenotypic traits, we also test for patterns of divergence among sexes by comparing size at maturity and sexual dimorphism in body shape between males and females in each population type. We take advantage of a natural experiment in western Mexico where, in some locations, P. baenschi co-occur with a closely-related species, Poeciliopsis turneri (sympatric populations) and, in other locations, they occur in isolation (allopatric populations). The results obtained in the present study show that sympatric populations of P. baenschi differed significantly in life-history traits and in body shape compared to their allopatric counterparts. Additionally, males and females showed different responses for size at maturity in sympatric conditions versus allopatric conditions. However, the amount of sexual dimorphism did not differ between sympatric and allopatric populations of P. baenschi. Hence, we conclude that not all traits show similar levels of phenotypic divergence in response to sympatric conditions. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 608–618.
Joseph M. Quattro - One of the best experts on this subject based on the ideXlab platform.
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Mode of Origin and Sources of Genotypic Diversity in Triploid Gynogenetic Fish Clones (Poeciliopsis: Poeciliidae)
Genetics, 1992Co-Authors: Joseph M. Quattro, John C. Avise, Robert C. VrijenhoekAbstract:Most tributaries of the Rio Fuerte in northwestern Mexico contain one or more clones of allotriploid fish of the genus Poeciliopsis. We used multilocus allozyme genotypes and mitochondrial DNA (mtDNA) haplotypes to examine several potential modes of origin of these gynogenetic all-female fish. The allozyme studies corroborated earlier morphological work revealing the hybrid constitution of two triploid biotypes, Poeciliopsis 2 monacha-lucida and Poeciliopsis monacha-2 lucida. Each biotype carries one or two whole genomes from the each of the sexual species P. monacha and P. lucida. Restriction site analysis of mtDNA revealed that P. monacha was the maternal ancestor of five electrophoretically distinguishable triploid clones. Four of five clones were marked by closely related, composite, allozyme/mtDNA genotypes, suggesting they had common origins from an allodiploid clone of the P. monacha-lucida biotype. Genotypic analysis revealed that all five clones arose via the "genome addition" pathway. Fertilization of unreduced ova in P. monacha-lucida females by sperm from P. monacha and P. lucida males, respectively, gave rise to both biotypes.
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An ancient clonal lineage in the fish genus Poeciliopsis (Atheriniformes: Poeciliidae).
Proceedings of the National Academy of Sciences of the United States of America, 1992Co-Authors: Joseph M. Quattro, John C. Avise, Robert C. VrijenhoekAbstract:Genetic diversity in mtDNA was assessed within the unisexual (all female) hybridogenetic fish Poeciliopsis monacha-occidentalis and the two sexual species from which it arose. Results confirm that P. monacha was the maternal ancestor and that paternal leakage of P. occidentalis mtDNA has not occurred. Of particular interest is the high level of de novo mutational divergence within one hybridogenetic lineage that on the basis of independent zoogeographic considerations, protein electrophoretic data, and tissue grafting analysis is of monophyletic (single hybridization) origin. Using a conventional mtDNA clock calibration, we estimate that this unisexual clade might be >100,000 generations old. Contrary to conventional belief, this result shows that some unisexual vertebrate lineages can achieve a substantial evolutionary age.
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life history plasticity under resource stress in a clonal fish poeciliidae Poeciliopsis
Journal of Fish Biology, 1991Co-Authors: S. C. Weeks, Joseph M. QuattroAbstract:Within-individual plasticity for reproductive investment was examined in a clonal fish (Poeciliidae: Poeciliopsis) grown under six levels of resource stress. Growth, age at first reproduction, egg production, egg size, egg energetic content, and survivorship were measured from fish grown in three dietary and two density treatments. Growth and fecundity decreased with both increased density and food stress. Age at first reproduction increased with increased density, but was unaffected by the diet treatments. Reproductive effort (clutch size per female weight), offspring investment (egg size and egg energetic content), and survivorship were invariant across all treatment combinations. We compare these results with predictions based on theoretical treatments of optimal reproductive investment.
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Molecular Evidence for Multiple Origins of Hybridogenetic Fish Clones (Poeciliidae: Poeciliopsis)
Genetics, 1991Co-Authors: Joseph M. Quattro, John C. Avise, Robert C. VrijenhoekAbstract:Hybrid matings between the sexual species Poeciliopsis monacha and Poeciliopsis lucida produced a series of diploid all-female lineages of P. monacha-lucida that inhabit the Rio Fuerte of northwestern Mexico. Restriction site analyses of mitochondrial DNA (mtDNA) clearly revealed that P. monacha was the maternal ancestor of these hybrids. The high level of mtDNA diversity in P. monacha was mirrored by similarly high levels in P. monacha-lucida; thus hybridizations giving rise to unisexual lineages have occurred many times. However, mtDNA variability among P. monacha-lucida lineages revealed a geographical component. Apparently the opportunity for the establishment of unisexual lineages varies among tributaries of the Rio Fuerte. We hypothesize that a dynamic complex of sexual and clonal fishes appear to participate in a feedback process that maintains genetic diversity in both the sexual and asexual components.
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Correlations between egg size and egg energetic content within and among biotypes of the genus Poeciliopsis
Journal of Fish Biology, 1991Co-Authors: Joseph M. Quattro, S. C. WeeksAbstract:That a positive correlation exists between egg size and egg energetic content is an assumption of empirical and theoretical studies of life-history evolution. Although assumed, this relationship lacks substantiative support, particularly at the intraspecific level. To this end, we evaluated the validity of this assumption within and among clonal and bisexual females of the desert fish Poeciliopsis. As anticipated, we found generally high correlations between the two variables at all levels studied. Thus, egg volume remains a reliable and often precise indicator of maternal investment in this species.