Venezuelan Andes Research Articles

New locality records and geographic distribution map of Dendropsophus meridensis (Rivero, 1961) (Anura: Hylidae) in the Andes of Venezuela

Dendropsophus meridensis is a medium-sized treefrog endemic to the Cordillera de Mérida in the Venezuelan Andes. The geographic distribution of this species is poorly known, and only 10 localities known in the literature. Most of these localities do not have associated geographic coordinates and altitude. In this note we provide eight new locality records and a geographic distribution map of D. meridensis, based on field work, revision of Venezuelan museum collections, and species distribution modeling. Three of these new localities were found after performing species distribution modeling. Additionally, some comments on natural history and color variation are included.

A new Poissonian algorithm for the determination of fission-track ages

Fission-track (FT) thermochronology has been widely used since the 1970s to constrain the low-temperature thermal history of rocks in numerous geological settings. Statistical problems associated with this method have been addressed since the 1980s. Today, with the improvements brought to the technique, new questions arise which require the adaptation of previously established statistical methods. Samples used for FT thermochronology are typically composed of minerals (e.g. apatite, zircon, titanite, etc.) with a wide variability in uranium (U) concentration. In this work we propose a new statistical methodology, called p-partition, that even assuming grains of a same sample could have different uranium concentrations. We apply our methodology to fission-track ages standards, in-situ and detrital samples. For standards we found that the new estimated age is closer to the independently determined K–Ar age, for detrital samples we applied our methodology to existent and published data for the case of the Venezuelan Andes. Our results were compared with other decomposition methods for the fission-track ages distributions, they show robustness, and in some particular case our method has more resolution in comparison with conventional methods. In this work we present a methodology and algorithms that attempt to solve mathematically the problem of decomposition of data with Poisson mixtures.

Addendum to ‘New dinosaur (Theropoda, stem -Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes’

[This corrects the article DOI: 10.1098/rsos.140184.].

Linking patterns and processes through ecosystem engineering: effects of shrubs on microhabitat and water status of associated plants in the high tropical Andes

Studies on alpine and semi-arid environments indicate that plants that act as ecosystem engineers improve microhabitat conditions and modify local plant abundance and diversity. However, few studies have linked these patterns with the physiological responses of associated species. We analyze the role of a dominant shrub (Hypericum laricifolium) as an ecosystem engineer in paramo ecosystems at two altitudes (3,715 and 4,300 m) in the Venezuelan Andes. Superficial soil temperatures, soil water content, and organic matter were compared under the crown and outside. We selected the species with positive and negative spatial relations with the shrub and compared their midday leaf water potentials and turgor loss points in individuals growing under shrubs and outside. Results show that H. laricifolium dampened temperature oscillations and increased soil water and organic matter contents, the effect being more pronounced at the drier, lower elevation site. While positively associated forbs showed an improvement in their water status when growing under the crown, the species with the lowest water potentials and higher water-stress tolerance were grasses with a negative spatial relation with the shrub; this was consistent at both elevations. Moreover, the effect of the shrub on the water status and abundance of the exotic herb Rumex acetosella changed from positive in the drier site to negative in the more mesic site. Our results provide mechanistic evidence for interpreting spatial association patterns between nurse plants and other species in the alpine tropics. We propose that stress-resistance strategies (tolerance vs. avoidance) and origin (native vs. exotic) influence interactions with ecosystem engineers.

Reassessment of the Microbial Role in Mn-Fe Nodule Genesis in Andean Paleosols

The presence of Mn-Fe nodules in the epipedons (surface horizons) of paleosols of presumed Upper Neogene age in the northwestern Venezuelan Andes have been interpreted as products of inorganic oxidation and reduction processes operating over the full range of glacial and interglacial cycles that affected paleosol morphogenesis. New microscopic/chemical data from combined SEM-EDS-FIB analyses of representative Mn-Fe nodules indicate microbes play an important role in Mn/Fe precipitation leading to their genesis in alpine Mollisols (Argiustolls). Although the prevailing new data are based mainly on fossil forms of filamentous bacteria and fungi and other biogenic pseudomorphs that may represent the former resident bacteria, the presence of extant microbes must await field experiments/collection, followed by a molecular microbiology approach to determine the biological drivers of metal precipitation. As in other terrestrial niche environments, microbes are seen here to play a role, perhaps a key one, in the morphogenesis of paleosols of importance in upper Neogene paleoenvironmental reconstruction.

Four new species of Andean Pilea (Urticaceae), with additional notes on the genus in Venezuela.

Four new species of Pilea (Urticaceae) from the Andes of Venezuela are described and illustrated: Pilea matthewii sp. nov., Pilea miguelii sp. nov., Pilea nicholasii sp. nov., and Pilea nidiae sp. nov. The affinities of these species and their positions within the informal classifications of Pilea proposed by Weddell and Killip are discussed. Notes on other species of Pilea found in Venezuela also are presented.

A palaeoequatorial ornithischian and new constraints on early dinosaur diversification

Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic-Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history.

Primer registro de Nemopalpus phoenimimos Quate & Alexander, 2000 (Diptera, Psychodidae, Bruchomyiinae) en Venezuela

Se registra por primera vez la presencia en Venezuela del díptero-psicódido de la subfamilia Bruchomyiinae Nemopalpus phoenimimos Quate & Alexander, 2000. Se capturaron dos especímenes a 2200 m de altitud en Escagüey (8°42’31.19”N; 70°59’41.25”W), estado Mérida, en la región andina de Venezuela. Este registro representa la segunda especie de Nemopalpus Macquart,1838 reportada para el país.

Nuevos registNuevos registros de especies del género Pristimantis (Anura: Craugastoridae) para el nororiente de Colombiaros de especies del género Pristimantis (Anura: Craugastoridae) para el nororiente de Colombia

Colombia is one of the countries with the highest species richness of the genus Pristimantis , however, there are gaps in taxonomic, ecological knowledge and distribution of many of them, particularly in the northeastern region of Colombia, since by its proximity to Venezuela probably harbors species not yet reported for Colombia. Objective: To report new distribution records for species of Pristimantis in Colombia. Methodology: Between October 2010 and April 2012 amphibians sampling were conducted in four localities in the department of Norte de Santander. The collected specimens were properly preserved and all smorphometric measurements were made for identified by the original descriptions and comparisons with specimens deposited in biological collections. Results: We expand the geographic distribution of four species: P. gryllus , P. melanoproctus , P. mondolfii and P. frater . The first three previously known only to the Andes of Venezuela and are registered for the first time for Colom- bia; P. frater , which is distributed in the Eastern Cordillera of Colombia, so our record represents the northernmost point of its known distribution. Conclusion: Three new records of Pristimatis for Colom- bia and one range expansion of one species for the country, however these species face threats from forest fragmentation and infection with Batrachochytrium dendrobatidis in the localities reported in Norte de Santander.

A Taxonomic Assessment ofRacomitrium steerei(Grimmiaceae, Musci) from Venezuela

Bednarek-Ochyra, H. 2014. A taxonomic assessment of Racomitrium steerei (Grimmiaceae, Musci) from Venezuela.–Herzogia 27: 141–146.Racomitrium steerei from the northern Andes of Venezuela is taxonomically assessed and some diagnostic traits of the type material are illustrated. An investigation of the type material revealed that this species is inseparable from Bucklandiella lamprocarpa, a south-pan-temperate species which extends into the Neotropics along the Andean chain. Diversity of the Grimmiaceae subfam. Racomitrioideae in northern South America is briefly outlined.

A NEW LOCALITY OF THE HOODED ANTPITTA (GRALLARICULA CUCULLATA: GRALLARIDAE) FOR THE COLOMBIAN CENTRAL ANDES

We report a new locality record of the Hooded Anpitta ( Grallariculla cucullata ) , a threatened species inhabiting montane cloud forests of the Colombian and Venezuelan Andes. This is the first record for Quindio department. We present capture-rate data at this site that suggests a resident, relatively large population.

Breeding and age-structure seasonality in Carollia brevicauda and other frugivorous bats (Phyllostomidae) in cloud forests in the Venezuelan Andes

The most universal adaptations of tropical frugivores to the seasonal rhythms of fruiting involve their annual breeding cycles. In bats, these cycles typically follow a pattern termed bimodal polyestry, consisting in the production of one offspring per female twice during the breeding season. We use data gathered along 29 years to show that, in cloud forests in the Venezuelan Andes, the breeding cycles of Carollia brevicauda and other frugivorous phyllostomid bats (eigth species of the genera Sturnira , Artibeus , Dermanura , Enchisthenes , and Platyrrhinus ) conform to bimodal polyestry, with a high interspecific synchronization and a low interannual variability. We analyze the adaptive significance of this pattern in terms of three hypothetical variables: demand, consumption, and supply of food sources, explicitly concluding that the seasonality of fruit production, resulting from the average rainfall regime, is the ultimate factor causing bimodal polyestry. The constancy in the seasonal schedule of breeding and concomitant fluctuation of age proportions, both in the bat populations studied under natural conditions, and in captive Carollia colonies maintained under year-round uniform conditions, suggests presence of an endogenous component in the annual breeding cycles of frugivorous phyllostomids. To conclude, we argue that the seasonality of fruiting is also likely to be the proximate environmental factor modulating these cycles, irrespective of whether it does so indirectly as a time cue entraining endogenous rhythms, or directly as a limiting factor determining whether bat breeding and population growth are possible. Key words: Artibeus , bimodal polyestry, circannual rhythms, Dermanura , Enchisthenes , environmental cues, Platyrrhinus , reproductive strategies, Sturnira , tropical seasons.

Constraints for the restoration of tropical alpine vegetation on degraded slopes of the Venezuelan Andes

Background: In the Venezuelan high Andes, wheat cultivation on steep slopes since colonial times has caused the degradation of extensive areas. After several decades of abandonment, natural succession has not allowed the spontaneous recovery of the original alpine vegetation.Aims: Our aim was to identify a degradation gradient, based on vegetation structure, and relate this gradient to different environmental factors (grazing intensity, physical soil degradation, distance to seed sources and loss of soil fertility) that could be preventing spontaneous succession.Methods: Vegetation structure and 22 environmental variables were sampled on 92 slopes with different degrees of degradation. Multivariate statistics were used to relate the state of the vegetation to environmental factors.Results: Six types of vegetation were identified and ranked along a degradation gradient. Several soil properties, for example C, N, clay content and cation-exchange capacity, decreased by as much as 50% along this gradient, while other variables, such as current grazing intensity were only slightly correlated to the degradation gradient.Conclusions: Vegetation and soil properties were clearly related to a strong degradation gradient, caused by former wheat cultivation and overgrazing, with symptoms of desertification. Restoration practices have to be directed towards re-establishing soil organic matter and its functional role in regulating water balance and nutrient cycling.

Population dynamics of the rat Microryzomys minutus (Rodentia: Muridae) in the Venezuelan Andes

The population dynamics of the small forest rice rat Microryzomys minutus, a murid rodent that occurs in the high altitudes of the northern and central Andes, was studied in disturbed and primary environments in a cloud forest of the Venezuelan Andes (Juan Pablo Peñaloza National Park, 8 degrees 11'N, 71 degrees 49'W). We collected 121 animals (66 female female and 55 male male) between 1995 and 1998, using pitfall traps with formalin. Adult males were heavier than adult females. Relative abundance was much greater in the disturbed environments (over 10 individuals in some periods) than in the primary cloud forest: 4-8 individuals. In the disturbed environments, the rats were extremely abundant in the first sampling period, and less frequent afterwards. In the cropland, abundance showed some fluctuations during the study and displayed two small abundance peaks in March-June 1997 and 1998. In the mined area, the rats had irregular fluctuations until March-June 1997 and were not recorded in July-October 1997. The occurrence of this rat in both disturbed and natural habitats confirms the wide ecological tolerance of this species.

Proglacial lake sediment records reveal Holocene climate changes in the Venezuelan Andes

Lake sediment records from the Cordillera de Mérida in the northern Venezuelan Andes document the history of local glacial variability and climate changes during the Holocene (∼12 ka to the present). The valleys that contain these lakes have similar bedrock compositions and hypsometries, but have different headwall elevations and aspects, which makes them useful for investigating the magnitude of past glaciations. There was widespread glacial retreat in the Venezuelan Andes during the early Holocene, after which most watersheds remained ice free, and thus far only valleys with headwalls higher than ∼4400 m asl contain evidence of glaciation during the last ∼10 ka. There was a pronounced shift in sediment composition for the Montos (headwall: ∼4750 m asl) and Los Anteojos (headwall: ∼4400 m asl) records during the middle Holocene from ∼8.0 to 7.7 ka when conditions appear to have become ice free and drier. There is tentative evidence that the glacier in the Mucubají valley (headwall: ∼4609 m asl) advanced from ∼8.1 to 6.6 ka and then retreated during the latter stages of the middle Holocene. Clastic sediment accumulation in other nearby lake basins was either low or decreased throughout most of the middle Holocene as watersheds stabilized under warmer and/or drier conditions. In the Montos record, there was another major shift in sediment composition that occurred from ∼6.5 to 5.7 ka, similar to other regional records that suggest conditions were drier during this period. Overall, the late Holocene was a period of warmer and wetter conditions with ice extent at a minimum in the northern tropical Andes. There were also punctuated decadal to multi-centennial periods of higher clastic sediment accumulation during the last ∼4 ka, likely in response to periods of cooling and/or local precipitation changes. In watersheds with headwalls above 4600 m asl, there is evidence of glacial advances during the Little Ice Age (∼0.6–0.1 ka). The pattern of glacial variability is generally similar in both the northern and southern tropics during the Little Ice Age, suggesting that ice margins in both regions were responding to colder and wetter conditions during the latest Holocene. The observed pattern of Holocene climate variability in the Venezuelan Andes cannot be explained by insolation forcing alone, and tropical ocean influences were likely associated with the observed glacial and lake level changes.

Flora of Guaramacal (Venezuela): Monocotyledons

The present volume is a taxonomic study of the monocotyledons that occur in Guaramacal National Park (officially El Parque Nacional “General Cruz Carillo en Guaramacal”), which protects the Ramal de Guaramacal, an outlier of the more extensive Cordillera de Mérida in the Venezuelan Andes. The park covers 215 km2 in Trujillo and Portuguesa states and includes forest and páramo found between 1,600 and 3,100 m elevation. In all, 25 families, 135 genera, and 315 species (316 taxa) are treated; the greatest species diversity occurs in Orchidaceae (147 species), Poaceae (57 species), and Cyperaceae (28 species). Twenty species are currently known only from Guaramacal and might be endemic. Four new combinations are made: Cyperus hortensis (Salzm. ex Steud.) Dorr, Acronia archidiaconi (Ames) Carnevali & G. A. Romero, Crocodeilanthe gelida (Lindl.) Carnevali & I. Ramírez, and Fernandezia schultesii (L. O. Williams) Carnevali & Dorr.

La Tribu Dysoniini Parte III: Adiciones a Los GénerosApolinaria, Lichenodraculus, Machimoidesy Markia (Orthoptera: Tettigoniidae)

Abstract In this paper seven new species are described: Machimoides sofiae n. sp., from the Colombian Andes, Lichenodraculus holgeri n. sp., from the Guiana Shield and Venezuelan Amazon, Markia nicolasi n. sp., from Costa Rica, M. agudeloi n. sp., from Guyana (previously British Guiana) near the border with Suriname, M. bolivarensis n. sp., from the states of Bolivar and Amazonas in Venezuela (located on the Guiana Shield), M. guerreroi n. sp., and M. gaianii n. sp., from the Venezuelan Andes. A female of Apolinaria hygracantha (Karsch, 1896) is described and illustrated. Keys to species of all genera treated here are provided. The distribution of the genera Markia and Machimoides is discussed; for the latter genus discussion focuses on the current status of its species. Description of new species treated herein expands considerably the distribution range of the genera studied, also the generic diagnostic characters are enriched and reinforced.

Two New Species of <I>Chusquea</I> (Poaceae: Bambusoideae: Bambuseae) from Venezuela and a Redescription of <I>Chusquea purdieana</I>

Abstract Chusquea purdieana is a previously poorly known species of woody bamboo (Poaceae: Bambusoideae: Bambuseae) from northern Colombia characterized by a scandent habit, a large number of leafy subsidiary branches per node, and narrow foliage leaf blades. A morphological analysis of similar collections from Venezuela and Colombia allowed us to distinguish two new species from the Venezuelan Andes, C. aurea and C. multiramea, based on a combination of vegetative and reproductive features. We here describe and illustrate the new species and we also provide a detailed redescription of C. purdieana, along with illustrations of its most diagnostic features. We report the occurrence of C. purdieana in Venezuela and document a broader range for the species in Colombia.

Susceptibility of the endangered frog Dendropsophus meridensis to the pathogenic fungus Batrachochytrium dendrobatidis

Chytridiomycosis is an emerging disease that has driven some amphibian species to extinction while leaving others apparently unharmed. Its causative agent, Batrachochytrium dendrobatidis (Bd), now persists endemically in many amphibian communities. Understanding host species response to Bd infection is critical for managing chytridiomycosis because the epidemiology of this disease is host-specific. Dendropsophus meridensis is an endangered hylid frog endemic to the Venezuelan Andes. This species is sympatric with the American bullfrog Lithobates catesbeianus, an introduced species known to act as a reservoir for Bd. High prevalence of infection and high zoospore burdens in wild populations of D. meridensis in the Venezuelan Andes suggested some tolerance for Bd. However, experimental exposure of post-metamorphic frogs resulted in 53% mortality, a value that represents a 14-fold increase in the odds of dying compared to control frogs. Repeated diagnostics using real-time polymerase chain reaction assays demonstrated that individuals that died accumulated a higher number of zoospores than those that survived, although this value was lower than the mean zoospore burdens observed in natural populations. Given the susceptibility of D. meridensis to a strain of Bd isolated from a nearby population of bullfrogs, we emphasize the need to limit the dispersion of this invasive species.

Bacteria recovered from a high-altitude, tropical glacier in Venezuelan Andes

Glacial-ice microorganisms are intensively studied world-wide for a number of reasons, including their psychrophilic lifestyle, their usefulness in biotechnology procedures and their relationship with the search of life outside our planet. However, because of the difficulties for accessing and working at altitudes of >5.000 m above sea level, tropical glaciers have received much less attention than their arctic and antarctic counterparts. In the present work we isolated and characterized a total of forty-five pure isolates originating from direct plating of melted ice collected at the base of a rapidly-retreating, small glacier located at around 4.900 m.a.s.l. in Mount Humboldt (Sierra Nevada National Park, Mérida State, Venezuela). Initial examination of melted ice showed the presence of abundant- (>10⁶ cells ml⁻¹), morphologically diverse- and active bacterial cells, many of which were very small ("dwarf cells"). The majority of the isolates were psychrophilic or psychrotolerant and many produced and excreted cold-active extracellular enzymes (proteases and amylases). The antibiotic tests showed an elevated percentage of isolates resistant to high doses (100 μg/ml) of different antibiotics including ampicillin, penicillin, nalidixic acid, streptomycin, chloramphenicol, kanamycin and tetracycline. Multiresistance was also observed, with 22.22 % of the strains simultaneously resistant up to five of the antibiotics tested. Metal resistance against Ni⁺⁺, Zn⁺⁺ and Cu⁺⁺ was also detected. In accordance with these results, plasmids of low and high molecular weight were detected in 47 % of the isolates. Twenty-two partial 16S rDNA sequences analyzed allowed grouping the isolates within five different phyla/classes: Alpha-, Beta- and Gamma-proteobacteria, Actinobacteria and Flavobacteria. This is the first report concerning South American Andean glacial ice microorganisms.