Composición y distribución de hepáticas (Marchantiophyta) en un intervalo altitudinal en la Cordillera Oriental de Colombia / Composition and distribution of liverworts (Marchantiophyta) in a continuous altitudinal range on the Cordillera Oriental of Colombia

Resumen La composición de especies de hepáticas sobre los Andes del Norte varía con la altitud en relación con diferentes factores bióticos (vegetación) y abióticos (temperatura, humedad y luminosidad). Para probar esta afirmación se determinó la diversidad y distribución de las Marchantiophytas en un rango altitudinal entre los 2 400 y 3 400 m sobre la Cordillera Oriental colombiana, estableciendo cómo éstas varían entre altitudes y zonas de vida con respecto a los factores abióticos. Se realizaron muestreos cada 200 m y se registraron datos ambientales durante un año. Se encontraron 162 especies, la composición de hepáticas varió a lo largo del gradiente altitudinal con un gran número de especies únicas en cada altitud. Se encontró la máxima diversidad en los 3 000 m, con una dominancia del hábito folioso y de especies epifitas, mientras que la mayor riqueza de familias y géneros se presentó entre los 3 200 y 3 400 m. Anoplolejeunea conferta presentó la mayor cobertura en la zona así como el mayor valor del índice de valor de importancia (IVI) y distribución altitudinal más amplia, ubicándose desde los 2 400 hasta 3 000 m en cuatro diferentes sustratos. Las hepáticas se distribuyeron altitudinalmente de manera diferencial, con una diversidad beta alta (0.864) debido al recambio altitudinal de especies, con más del 30 % de disimilaría en la composición de especies cada 200 m altitudinales, dependiendo principalmente de cambios en la luminosidad. Consecuentemente, la temperatura, humedad y luminosidad y su relación con la vegetación son determinantes en la diversidad y distribución de las hepáticas en la Cordillera Oriental de los Andes colombianos.

Abstract The species composition of liverworts varies with altitude in the Northern part of the Andes due to the relationship of biotic (vegetation) and abiotic factors (temperature, humidity, and sunlight brightness). In order to test this affirmation we determined the diversity, species composition, abundance, and distribution of species of Marchantiophyta in an altitudinal range from 2 400 to 3 400 m on the Colombian Cordillera Oriental, and established how these vary with altitude and life-zones, regarding abiotic factors. Samples, taken every 200 m in the altitudinal range, and environmental data were registered during a year. We found 162 species, the composition of liverworts varied throughout the altitudinal gradient with a high number of unique species in each altitude. The maximum diversity was found at 3 000 m, along with a dominance of leafy habit and epiphytic species, while the higher richness of families and genera was found between 3 200 and 3 400 m. Anoplolejeunea conferta had the largest value of coverage in the zone, the highest value of importance value index (IVI), and the widest altitudinal distribution, from 2 400 to 3 000 m in four different substrates. The liverworts were distributed differently with altitude, we found a high beta diversity (0.864) due to the replacement of species, with more that 30 % of dissimilarity in species composition every 200 altitudinal meters, mainly depending on sunlight brightness variation. Accordingly, we found that abiotic factors like temperature, humidity, and sunlight brightness and its relationship vegetation are determinant in the diversity and altitudinal distribution of liverworts in the study area. Rev. Biol. Trop. 66(2): 559-570. Epub 2018 June 01.

Estimates of DNA damage by the comet assay in the direct-developing frog Eleutherodactylus johnstonei (Anura, Eleutherodactylidae)

The aim of this study was to use the Comet assay to assess genetic damage in the direct-developing frog Eleutherodactylus johnstonei. A DNA diffusion assay was used to evaluate the effectiveness of alkaline, enzymatic and alkaline/enzymatic treatments for lysing E. johnstonei blood cells and to determine the amount of DNA strand breakage associated with apoptosis and necrosis. Cell sensitivity to the mutagens bleomycin (BLM) and 4-nitroquinoline-1-oxide (4NQO) was also assessed using the Comet assay, as was the assay reproducibility. Alkaline treatment did not lyse the cytoplasmic and nuclear membranes of E. johnstonei blood cells, whereas enzymatic digestion with proteinase K (40 !g/mL) yielded naked nuclei. The contribution of apoptosis and necrosis (assessed by the DNA diffusion assay) to DNA damage was estimated to range from 0 percent to 8 percent. BLM and 4NQO induced DNA damage in E. johnstonei blood cells at different concentrations and exposure times. Dose-effect curves with both mutagens were highly reproducible and showed consistently low coefficients of variation (CV < 10 percent). The results are discussed with regard to the potential use of the modified Comet assay for assessing the exposure of E. johnstonei to herbicides in ecotoxicological studies.