RESUMO

Color polymorphism can be maintained in natural populations by natural selection or sexual selection. In this study, we use two different approaches to test which of these evolutionary mechanisms may explain the presence of color polymorphism in the Cuban Limia (Limia vittata), an endemic livebearing fish from Cuba. First, we investigate the role of sexual selection using traditional binary choice tests looking at both female and male preferences relative to varying degrees of black spotting in stimulus mates. Second, we assess the role of natural selection by analyzing the frequency and geographic distribution of black-spotted and nonspotted morphs of L. vittata in natural populations from Cuba. The frequency of black-spotted morphs is significantly higher in brackish and saltwater environments compared with freshwater habitats, which could be related to higher predation pressure in coastal ecosystems compared with purely freshwater environments. Our results suggest that habitat variation is the most important factor in maintaining color polymorphism in L. vittata. Salinity levels could be indirectly responsible for maintaining different color morphs in this species, likely due to the regulatory effect of saline gradients on predation regimes.

RESUMO

Carotenoid-based polymorphisms are widespread in populations of birds, fish, and reptiles,1 but generally little is known about the factors affecting their maintenance in populations.2 We report a combined field and molecular-genetic investigation of a nestling beak color polymorphism in Darwin's finches. Beaks are pink or yellow, and yellow is recessive.3 Here we show that the polymorphism arose in the Galápagos half a million years ago through a mutation associated with regulatory change in the BCO2 gene and is shared by 14 descendant species. The polymorphism is probably a balanced polymorphism, maintained by ecological selection associated with survival and diet. In cactus finches, the frequency of the yellow genotype is correlated with cactus fruit abundance and greater hatching success and may be altered by introgressive hybridization. Polymorphisms that are hidden as adults, as here, may be far more common than is currently recognized, and contribute to diversification in ways that are yet to be discovered.

Assuntos

Bico , Dioxigenases/genética , Tentilhões , Proteínas de Peixes/genética , Animais , Equador , Tentilhões/genética , Genótipo , Polimorfismo Genético

RESUMO

Traditionally, species identification in nudibranch gastropods relies heavily on body color pattern. The Felimida clenchi species complex, a group of brightly colored Atlantic and Mediterranean species in the family Chromodorididae, has a history of exceptional controversy and discussion among taxonomists. The most widely accepted hypothesis is that the complex includes four species (Felimida clenchi, F. neona, F. binza and F. britoi), each with a characteristic body color pattern. In this study, we investigated the taxonomic value of coloration in the Felimida clenchi complex, using molecular phylogenetics, species-delimitation analyses (ABGD, GMYC, PTP), haplotype-network methods, and the anatomy of the reproductive system. None of our analyses recovered the traditional separation into four species. Our results indicated the existence of three species, a result inconsistent with previous taxonomic hypotheses. We distinguished an undescribed species of Felimida and redefined the concepts of F. clenchi and F. binza, both highly polychromatic species. For the first time, molecular data support the existence of extreme color polymorphism in chromatic nudibranch species, with direct implications for the taxonomy of the group and its diversity. The polychromatism observed in the F. clenchi complex apparently correlates with the regional occurrence of similar color patterns in congeneric species, suggesting different mimicry circles. This may represent a parallel in the marine environment to the mechanisms that play a major role in the diversification of color in terrestrial and fresh-water chromatic groups, such as heliconian butterflies.

Assuntos

Gastrópodes/classificação , África , Animais , Brasil , Região do Caribe , Citocromos c/classificação , Citocromos c/genética , Citocromos c/metabolismo , DNA/química , DNA/isolamento & purificação , DNA/metabolismo , Bases de Dados Genéticas , Haplótipos , Histonas/classificação , Histonas/genética , Histonas/metabolismo , Filogenia , Filogeografia , Pigmentação , RNA Ribossômico 16S/classificação , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/metabolismo , RNA Ribossômico 28S/classificação , RNA Ribossômico 28S/genética , RNA Ribossômico 28S/metabolismo , Alinhamento de Sequência , Análise de Sequência de DNA

RESUMO

Recent studies investigating vicariance and dispersal have been focused on correlating major geological events with instances of taxonomic expansion by incorporating the fossil record with molecular clock analyses. However, this approach becomes problematic for soft-bodied organisms that are poorly represented in the fossil record. Here, we estimate the phylogenetic relationships of the nudibranch genus Acanthodoris Gray, 1850 using three molecular markers (16S, COI, H3), and then test two alternative geologically calibrated molecular clock scenarios in BEAST and their effect on ancestral area reconstruction (AAR) estimates employed in LAGRANGE. The global temperate distribution of Acanthodoris spans multiple geological barriers, including the Bering Strait (∼5.32 Mya) and the Baja Peninsula (∼5.5 Mya), both of which are used in our dating estimates. The expansion of the Atlantic Ocean (∼95-105 Mya) is also used to calibrate the relationship between A. falklandica Eliot, 1905 and A. planca Fahey and Valdés, 2005, which are distributed in southern Chile and South Africa respectively. Phylogenetic analyses recovered strong biogeographical signal and recovered two major clades representing northern and southern hemispheric distributions of Acanthodoris. When all three geological events are applied to the calibration analyses, the age for Acanthodoris is estimated to be mid-Cretaceous. When the expansion of the Atlantic Ocean is excluded from our analyses, however, Acanthodoris is estimated to be much younger, with a divergence time estimate during the Miocene. Regardless of divergence estimates, our AAR suggests that Acanthodoris may have origins in the Atlantic Ocean with the Atlantic acting as a dispersal point to the northeastern Pacific. These results suggest that Acanthodoris exhibits a rare instance of western trans-arctic expansion. This study also shows that northeast Pacific specimens of A. pilosa should be regarded as A. atrogriseata and that A. serpentinotus should be regarded as a synonym of A. pina.

Assuntos

Calibragem , Gastrópodes/classificação , Filogenia , Animais , Regiões Árticas , Oceano Atlântico , Chile , Feminino , Fósseis , Gastrópodes/genética , Masculino , Oceano Pacífico , Filogeografia , África do Sul , Fatores de Tempo

RESUMO

The green and black poison-dart frog Dendrobates auratus exhibits high intraspecific variation in hue color and pattern throughout its range, making it a very popular species in the pet trade. We analyzed the correspondence between color variation and molecular variation of D. auratus from Costa Rica using RAPD analysis. Twenty-six random primers were analyzed for variation in 99 individuals from seven populations. Color pattern was scored from digital images of the dorsal and ventral views. In general, frogs from the Caribbean coast had significantly more light coloration than black color but cannot be grouped by population based only on hue pattern. Only 3 RAPD primers were found to be polymorphic, representing a total of 16 loci. Most of the molecular variation encountered here occurs within populations, thus making unclear the degree of population structure and differentiation. Further examination of COI mtDNA sequences from our samples also supports these results. Partial Mantel correlations suggested that the pattern of molecular variation is not congruent with the variation in color pattern in this species, an outcome that is discussed in terms of phenotypic evolution. Rev. Biol. Trop. 57 (Suppl. 1): 313-321. Epub 2009 November 30.

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La rana venenosa Dendrobates auratus posee una gran variación intraespecífica en tonos y patrones de coloración a lo largo de toda su distribución, lo que la hace una especie muy reconocible entre las especies de dendrobátidos. Analizamos la correspondencia entre variación de coloración y variación molecular de D. auratus de Costa Rica empleando análisis de RAPDs. La variación resultante en veintiséis "primers" aleatorios fue analizada en 93 individuos de siete localidades en Costa Rica. El patrón de coloración fue evaluado de imágenes digitales del dorso y vientre para los mismos individuos. En general, las ranas provenientes de localidades en la costa Caribe tienen significativamente una coloración más clara, con menos proporción de color negro que las de localidades en la vertiente Pacífica, pero no pueden ser agrupadas por localidad basadas simplemente en el patrón de coloración. Solamente tres RAPD "primers" fueron encontrados polimórficos, representando un total de 16 loci. Mucha de la variación molecular encontrada habita dentro de poblaciones, lo que hace difícil determinar el grado de estructura poblacional y diferenciación. La reexaminación posterior de secuencias del gen mitocondrial CO1 también apoya estos resultados. Correlaciones parciales de matrices (test de Mantel) sugieren que el patrón de variación molecular no es congruente con la variación en el patrón de coloración en esta especie, un resultado que es discutido en términos de evolución fenotípica.

Assuntos

Ranidae/classificação , Ecossistema , Costa Rica , Polimorfismo Genético

RESUMO

Body color polymorphism of urban populations of cosmopolite fly Drosophila kikkawai Burla, 1954 was investigated in relation to its possible association with environmental temperature. Samples of D. kikkawai were collected in spring, summer, autumn and winter between 1987 to 1988, in zones with different levels of urbanization in the southern Brazilian city of Porto Alegre, Rio Grande do Sul. A clear association was observed between darker flies and both seasons with low temperatures and areas of low urbanization (where temperature is generally lower than in urbanized areas). Results of preliminary laboratory experiments involving six generations of flies grown in chambers at temperatures of 17º and 25ºC confirmed this tendency to a relationship between body color and temperature, with allele frequency of the main gene involved in body pigmentation changing over time.

RESUMO

Body color polymorphism of urban populations of cosmopolite fly Drosophila kikkawai Burla, 1954 was investigated in relation to its possible association with environmental temperature. Samples of D. kikkawai were collected in spring, summer, autumn and winter between 1987 to 1988, in zones with different levels of urbanization in the southern Brazilian city of Porto Alegre, Rio Grande do Sul. A clear association was observed between darker flies and both seasons with low temperatures and areas of low urbanization (where temperature is generally lower than in urbanized areas). Results of preliminary laboratory experiments involving six generations of flies grown in chambers at temperatures of 17º and 25ºC confirmed this tendency to a relationship between body color and temperature, with allele frequency of the main gene involved in body pigmentation changing over time.

RESUMO

Body color polymorphism of urban populations of cosmopolite fly Drosophila kikkawai Burla, 1954 was investigated in relation to its possible association with environmental temperature. Samples of D. kikkawai were collected in spring, summer, autumn and winter between 1987 to 1988, in zones with different levels of urbanization in the southern Brazilian city of Porto Alegre, Rio Grande do Sul. A clear association was observed between darker flies and both seasons with low temperatures and areas of low urbanization (where temperature is generally lower than in urbanized areas). Results of preliminary laboratory experiments involving six generations of flies grown in chambers at temperatures of 17º and 25ºC confirmed this tendency to a relationship between body color and temperature, with allele frequency of the main gene involved in body pigmentation changing over time.

RESUMO

Here we describe the immature stages of Acrosternum (Chinavia) ubicum Rolston, and test the effect of the host plant on the size and coloration of the nymphs, by feeding them with developing fruits of Crotalaria incana L., Phaseolus vulgaris L., Glycine max (L.) Merril, Abelmoschus esculentus (L.), and Lycopersicon esculentum Mill. A. ubicum immatures are very similar to those from other neotropical Acrosternum species. The egg coloration varies from ochre to brown; the chorion is reticulated and the micropylar processes are clubbed and white. First to third instars are predominantly dark and the abdomen has a series of creamy to white maculae. Second to fifth instars show red to orange-red maculae on each of the dorso-lateral margins of the pronotum and mesonotum. In the fourth and fifth instars, these maculae are wider, and may also appear on the margins of the jugae, on the pronotum and mesonotum, and in the middle of the mesal and lateral plates of the abdomen. The orange-red coloration of these dorsal maculae seems specific to A. ubicum, but additional studies with other species of the genus are necessary to validate it as a good diagnostic characteristic. Fourth and fifth instars presented light and dark morphs, and their proportion varied according to the type of plant used as food. From the third instar on, the food also affected most of the morphometric parameters measured, i.e., length and width of the body, pronotum and scutelum, and antennal length; only the rostrum length remained unchanged.

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Neste trabalho são descritos os estágios imaturos de Acrosternum (Chinavia) ubicum Rolston e é avaliado o efeito do alimento no tamanho e coloração, das ninfas alimentadas com frutos de Crotalaria incana L., Phaseolus vulgaris L., Glycine max (L.) Merril, Abelmoschus esculentus (L.) e Lycopersicon esculentum Mill. Os imaturos de A. ubicum são semelhantes aos das demais espécies neotropicais de Acrosternum. Os ovos apresentam coloração ocre a castanho-parda, cório reticulado e processos micropilares clavados de coloração branca. Do 1° ao 3° ínstar, as ninfas têm coloração do corpo predominantemente escura e abdome com uma série de manchas de coloração creme a branca. A partir do 2° ínstar, apresentam manchas de coloração vermelha a vermelho-alaranjada nas margens dorsais do pronoto e mesonoto. A partir do 4° ínstar, as manchas são mais amplas, podendo também ocorrer nas margens das jugas, na superfície dorsal do pronoto e mesonoto e no centro das placas medianas e laterais do abdome. A coloração vermelho-alaranjada das manchas dorsais é aparentemente específica de A. ubicum, mas é necessário conhecer as ninfas das demais espécies do gênero para verificar se essa característica tem valor diagnóstico. O 4° e o 5° ínstares apresentaram formas escuras e claras, sendo que sua proporção variou de acordo com o tipo de alimento oferecido. A partir do 3° ínstar, o alimento também influenciou praticamente todos os parâmetros morfométricos considerados, isto é, comprimento e largura do corpo, comprimento e largura do pronoto e do escutelo e comprimento das antenas; somente o comprimento do rostro permaneceu inalterado.