RESUMO

Little is known about the natural history, biology, and population genetic structure of the Hardhead Silverside, Atherinomorus stipes, a small schooling fish found around islands throughout the Caribbean. Our field observations of A. stipes in the cays of Belize and the Florida Keys found that populations tend to be in close association with the shoreline in mangrove habitats. Due to this potential island-based population structuring, A. stipes represents an ideal system to examine questions about gene flow and isolation by distance at different geographic scales. For this study, the mitochondrial gene nd2 was amplified from 394 individuals collected from seven different Belizean Cays (N = 175) and eight different Floridian Keys (N = 219). Results show surprisingly high haplotype diversity both within and between island-groups, as well as a high prevalence of unique haplotypes within each island population. The results are consistent with models that require gene flow among populations as well as in situ evolution of rare haplotypes. There was no evidence for an isolation by distance model. The nd2 gene tree consists of two well-supported monophyletic groups: a Belizean-type clade and a Floridian-type clade, indicating potential species-level differentiation.

RESUMO

Models generally predict a response in species richness to climate, but strong climate-diversity associations are seldom observed in long-term (more than 10(6) years) fossil records. Moreover, fossil studies rarely distinguish between the effects of atmospheric CO2 and temperature, which limits their ability to identify the causal controls on biodiversity. Plants are excellent organisms for testing climate-diversity hypotheses owing to their strong sensitivity to CO2, temperature and moisture. We find that pollen morphospecies richness in an angiosperm-dominated record from the Palaeogene and early Neogene (65-20 Ma) of Colombia and Venezuela correlates positively to CO2 much more strongly than to temperature (both tropical sea surface temperatures and estimates of global mean surface temperature). The weaker sensitivity to temperature may be due to reduced variance in long-term climate relative to in higher latitudes, or to the occurrence of lethal or sub-lethal temperatures during the warmest times of the Eocene. Physiological models predict that productivity should be the most sensitive to CO2 within the angiosperms, a prediction supported by our analyses if productivity is linked to species richness; however, evaluations of non-angiosperm assemblages are needed to more completely test this idea.

Assuntos

RESUMO

Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.

Harttia merevari, uma espécie nova de bagre loricarideo é descrita com base em oito exemplares capturados no alto rio Caura, bacia do rio Orinoco, Venezuela. A espécie nova se distingue pela seguinte combinação de caracteres: abdome nu; duas ou três placas preanais; presença de uma placa óssea anterior a cada abertura branquial; sete placas laterais entre as nadadeiras peitorais e pélvicas; barbilhão maxilar curto e unido ao disco oral por uma dobra carnosa; superfície dorsal da cabeça e região anterior do corpo amarelo escuro ou marrom claro com numerosos pontos negros arredondados, região dorsal e posterior do corpo amarelo escuro ou marrom claro com cinco bandas transversais negras, as duas bandas anteriores com a parte dorsocentral difusa. A descoberta desta espécie nova estende a distribuição do gênero ao noroeste incluindo a bacia do rio Orinoco na vertente norte do Escudo das Guianas.

RESUMO

Harttia merevari, a new species of loricariid catfish, is described from eight specimens captured in the upper Caura River, Orinoco River basin, Venezuela. The new species is recognized by the following combination of characters: abdomen naked; two or three preanal plates; a bony plate before each branchial opening; seven lateral plates between the pectoral and pelvic fins; maxillary barbel short and attached to the oral disk by a fleshy fold; head dorsal surface and anterior portion of the body light or dark yellow with numerous, round black spots; posterior region of the body light or dark yellow with five black transverse bands, dorsal central area of the two anterior bands diffused. The discovery of this new species extends the distribution of the genus northwest to include the Orinoco River basin on the northern slope of the Guyana shield.

Harttia merevari, uma espécie nova de bagre loricarideo é descrita com base em oito exemplares capturados no alto rio Caura, bacia do rio Orinoco, Venezuela. A espécie nova se distingue pela seguinte combinação de caracteres: abdome nu; duas ou três placas preanais; presença de uma placa óssea anterior a cada abertura branquial; sete placas laterais entre as nadadeiras peitorais e pélvicas; barbilhão maxilar curto e unido ao disco oral por uma dobra carnosa; superfície dorsal da cabeça e região anterior do corpo amarelo escuro ou marrom claro com numerosos pontos negros arredondados, região dorsal e posterior do corpo amarelo escuro ou marrom claro com cinco bandas transversais negras, as duas bandas anteriores com a parte dorsocentral difusa. A descoberta desta espécie nova estende a distribuição do gênero ao noroeste incluindo a bacia do rio Orinoco na vertente norte do Escudo das Guianas.

RESUMO

Hipótesis nulas concernientes a distribuciones de especies al azar con respecto a subregiones y macrohábitats dentro del Río Paraguay son examinadas con datos provenientes de 131 especies de macrocrustáceos e invertebrados bénticos y 186 especies de plantas acuáticas. Los patrones son comparados con el resultado de distrubuciones de peces presentedos por Chernoff et al. (2004). Los datos provenientes de invertebrados mostraron un patrón identico entre subregiones, como es evidente en las distribuciones de peces. Los resulatdos apoyan el reconocimiento de dos zonas:i) la zona del Río Paraguay incluyendo las regiones superiores e inferiores del Río Negro, ii) la zona del Río Apa incluyendo el Río Apa y el Riacho La Paz. Para todos los grupos de datos, la zona del Río Paraguay posee una mayor riqueza de especies que la zona del Río Apa. La frontera entre las zonas es abrupta, lo cual es tamién apoyado por los datos provenientes de las plantas. Solo 11 de 186 especies de plantas fueron encontradas en ambas zonas. No existen patrones de congruencia entre macrohábotats. Datos de plantas e invertebrados contienen muchos valores que no son diferentes de las medias de similaridades al azar. Los datos provenientes de las plantas demuestra una relación entre hábitats de orilla y arena, los cuales están más sometidos a grandes corrientes que los otros hábitats. Las plantas encontradas en hábitats de aguas negras poseen poca similaridad con otros macrohábitats. Basado en estas observaciones, se concluye que habitats significantes dentro de cada zona deben ser preservados para mantener una gran porción de la biodiversidad

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RESUMO

Este trabajo presenta la descripción de dos nuevas especies género Bryconops Kner (1858) para Venezuela: Bryconops humeralis y Bryconops vibex. Estas especies son comunes en los ríos de la cuenca del orinoco en el Estado Amazonas (Venezuela). Ambas especies poseen manchas humeral sencilla, sin embargo ellas se diferencian por los siguientes caracteres: En B.vibex el cuerpo robusto, hocico, maxilar y aletas pélvicas alargados; B.humeralis posee un número menor de series de escamas bajo la línea lateral 4-5 vs 6 en B.vibex. Junto con Bryconops inpai, son las únicas especies del género que poseen mancha humeral. Sin embargo, en esta última especie la mancha es doble en lugar de sencilla

Assuntos