RESUMEN
Fruit traits have historically been interpreted as plant adaptations to their seed dispersers. On the other hand, different environmental factors, which vary spatially and temporally, can shape fruit-trait variation. The mistletoe Tristerix corymbosus has a latitudinal distribution along the South American Pacific rim that encompasses two different biomes, the matorral of central Chile and the temperate forest that extends south of the matorral. This mistletoe shows contrasting fruiting phenology (spring vs summer), fruit color (yellow vs green), and seed dispersers (birds vs marsupial) in these two biomes. We characterized geographic variation of morphological and nutritional fruit traits of T. corymbosus to evaluate which macroecological factor, biome or latitude, better explains spatial variation in these variables. For each of 22 populations, we obtained environmental data (temperature, precipitation, and canopy cover), measured fruit and seed morphology traits (size, shape, and weight), and pulp moisture and nutritional content (fiber, protein, fat, carbohydrates, ash, and caloric content). Patterns of variation for each variable were described by fitting and comparing five different simple models varying in slope, intercept or both. Fruit morphology showed a clear biome-related disruptive pattern, seed morphological traits were unrelated to either biome or latitude, whereas nutritional variables showed diverse patterns. Different environmental factors seem to affect fruit development and phenology, determining the observed fruit characteristics, with seed dispersers playing a minor role in shaping these patterns. More generally, the contrasting plant-seed disperser associations we addressed can be interpreted as the outcome of an ecological-fitting rather than of a coevolutionary process.
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Marsupiales , Muérdago , Phoradendron , Animales , Frutas , Fenotipo , SemillasRESUMEN
The current distribution of the flora and fauna of southern South America is the result of drastic geological events that occurred during the last 20 million years, including marine transgressions, glaciations and active vulcanism. All these have been associated with fragmentation, isolation and subsequent expansion of the biota, south of 35°S, such as the temperate rainforest. This forest is mostly dominated by Nothofagus trees and is the habitat of the relict marsupial monito del monte, genus Dromiciops, sole survivor of the order Microbiotheria. Preliminary analyses using mtDNA proposed the existence of three main Dromiciops lineages, distributed latitudinally, whose divergence was initially attributed to recent Pleistocene glaciations. Using fossil-calibrated dating on nuclear and mitochondrial genes, here we reevaluate this hypothesis and report an older (Miocene) biogeographic history for the genus. We performed phylogenetic reconstructions using sequences from two mitochondrial DNA and four nuclear DNA genes in 159 specimens from 31 sites across Chile and Argentina. Our phylogenetic analysis resolved three main clades with discrete geographic distributions. The oldest and most differentiated clade corresponds to that of the northern distribution (35.2°S to 39.3°S), which should be considered a distinct species (D. bozinovici, sensu D'Elía et al. 2016). According to our estimations, this species shared a common ancestor with D. gliroides (southern clades) about ~13 million years ago. Divergence time estimates for the southern clades (39.6°S to 42.0°S) ranged from 9.57 to 6.5 Mya. A strong genetic structure was also detected within and between clades. Demographic analyses suggest population size stability for the northern clade (D. bozinovici), and recent demographic expansions for the central and southern clades. All together, our results suggest that the diversification of Dromiciops were initiated by the Middle Miocene transgression (MMT), the massive marine flooding that covered several lowlands of the western face of Los Andes between 37 and 48°S. The MMT resulted from an increase in global sea levels at the Miocene climatic optimum, which shaped the biogeographic origin of several species, including Nothofagus forests, the habitat of Dromiciops.
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Marsupiales , Animales , Chile , ADN Mitocondrial/genética , Ecosistema , Filogenia , FilogeografíaRESUMEN
One of the possible consequences of biological invasions is the decrease of native species abundances or their replacement by non-native species. In Andean Patagonia, southern Argentina and Chile, many non-native animals have been introduced and are currently spreading. On Isla Victoria, Nahuel Huapi National Park, many non-native vertebrates were introduced ca. 1937. Records indicate that several native vertebrates were present before these species were introduced. We hypothesize that seven decades after the introduction of non-native species and without appropriate management to maintain native diversity, non-native vertebrates have displaced native species (given the known invasiveness and impacts of some of the introduced species). We conducted direct censuses in linear transects 500 m long (n = 10) in parallel with camera-trapping (1,253 camera-days) surveys in two regions of the island with different levels of disturbance: high (n = 4) and low (n = 6) to study the community of terrestrial mammals and birds and the relative abundances of native and non-native species. Results show that currently non-native species are dominant across all environments; 60.4% of census records and 99.7% of camera trapping records are of non-native animals. We detected no native large mammals; the assemblage of large vertebrates consisted of five non-native mammals and one non-native bird. Native species detected were one small mammal and one small bird. Species with the highest trapping rate were red and fallow deer, wild boar, silver pheasant (all four species are non-native) and chucao (a native bird). These results suggest that native species are being displaced by non-natives and are currently in very low numbers.
RESUMEN
Introduction and naturalization of non-native species is one of the most important threats to global biodiversity. Birds have been widely introduced worldwide, but their impacts on populations, communities, and ecosystems have not received as much attention as those of other groups. This work is a global synthesis of the impact of nonnative birds on native ecosystems to determine (1) what groups, impacts, and locations have been best studied; (2) which taxonomic groups and which impacts have greatest effects on ecosystems, (3) how important are bird impacts at the community and ecosystem levels, and (4) what are the known benefits of nonnative birds to natural ecosystems. We conducted an extensive literature search that yielded 148 articles covering 39 species belonging to 18 families -18% of all known naturalized species. Studies were classified according to where they were conducted: Africa, Asia, Australasia, Europe, North America, South America, Islands of the Indian, of the Pacific, and of the Atlantic Ocean. Seven types of impact on native ecosystems were evaluated: competition, disease transmission, chemical, physical, or structural impact on ecosystem, grazing/ herbivory/ browsing, hybridization, predation, and interaction with other non-native species. Hybridization and disease transmission were the most important impacts, affecting the population and community levels. Ecosystem-level impacts, such as structural and chemical impacts were detected. Seven species were found to have positive impacts aside from negative ones. We provide suggestions for future studies focused on mechanisms of impact, regions, and understudied taxonomic groups.
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Aves/fisiología , Ecosistema , Internacionalidad , Animales , Especificidad de la Especie , Factores de TiempoRESUMEN
Interaction webs summarize the diverse interactions among species in communities. The addition or loss of particular species and the alteration of key interactions can lead to the disassembly of the entire interaction web, although the nontrophic effects of species loss on interaction webs are poorly understood. We took advantage of ongoing invasions by a suite of exotic species to examine their impact in terms of the disassembly of an interaction web in Patagonia, Argentina. We found that the reduction of one species (a host of a keystone mistletoe species) resulted in diverse indirect effects that led to the disassembly of an interaction web through the loss of the mistletoe, two key seed-dispersers (a marsupial and a bird), and a pollinator (hummingbird). Our results demonstrate that the gains and losses of species are both consequences and drivers of global change that can lead to underappreciated cascading coextinctions through the disruption of mutualisms.
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Ecosistema , Especies Introducidas , Modelos Biológicos , Simbiosis , Animales , Argentina , Aves/fisiología , Mamíferos/fisiología , Muérdago/fisiología , Especificidad de la Especie , Avispas/fisiologíaRESUMEN
Dromiciops gliroides is an arboreal marsupial found in the temperate forests of South America (36-43 °S). This species is the sole extant representative of the order Microbiotheria, and is a key seed disperser of many native plant species, including the keystone mistletoe Tristerix corymbosus. Here, we synthesized the current knowledge on the ecological aspects of this species, and compared the available information from Argentina and Chile. Population density (23 ± 2 (mean ± SE) individual/ha) and home range (1.6 ± 0.6 ha) appear to be relatively similar across a marked ecological gradient in the mainland, but lower densities (7 ± 2 individual/ha) and smaller home ranges (0.26 ± 0.04 ha) were detected at island sites. We detected regional variation in body condition in Chile, but there were no significant differences across a wider E-W gradient. Movement patterns fit a random walk model; such behavior might have important consequences in shaping plant's spatial patterns. Although our data suggest that D. gliroides is more tolerant to habitat disturbance than previously thought, its incapability to disperse across non-forested areas suggests that the rapid rate of habitat loss and fragmentation that characterizes southern temperate forests likely poses a serious threat to this species. These ecological similarities are surprising given that forests studied receive dramatically different rainfall and correspond to distinct forest types. The evidence synthetized here dispels some of the myths about this species but also stresses the need for more comprehensive ecological studies across its distribution range.
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Ecología , Marsupiales/fisiología , Animales , Argentina , Constitución Corporal , Chile , Ecosistema , Densidad de Población , Lluvia , Dispersión de Semillas , ÁrbolesRESUMEN
Chaenothecopsis quintralis from southwestern Argentina is described and illustrated as a new species in the family Mycocaliciaceae. It has been found in three localities in the Andean Patagonian temperate forests, growing strictly on dung of an endemic marsupial Dromiciops gliroides. The new species is distinguished by the hemispherical, black capitulum of ascoma, the presence of asci with croziers, one-celled brown ascospores, and its fimicolous habitat. Analysis of partial nuclear large subunit rDNA (LSU) sequences showed that this taxon is within Mycocaliciales.
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Ascomicetos/clasificación , Argentina , Ascomicetos/genética , Ascomicetos/ultraestructura , ADN de Hongos/genética , ADN Ribosómico/genética , Filogenia , Árboles/microbiologíaRESUMEN
PREMISE OF THE STUDY: In the North American Arctic, the existence of one or several taxa closely related to Deschampsia cespitosa var. cespitosa has remained a puzzle for many years. Extreme morphological variation, lack of clear limits between alleged forms, and an extended geographic range often render identification keys incomplete, and raise the question of how many species this taxon represents. METHODS: Morphological and molecular analysis, including multivariate statistics, ITS and the cpDNA marker trnK-rps16, was conducted on D. cespitosa var. cespitosa and related taxa using 201 herbarium specimens from northern North America (Alaska, Canada, and Greenland). Fifty-three morphological centeracters were recorded from all specimens, while sequences were retrieved from 167 specimens. KEY RESULTS: Results show that Deschampsia cespitosa (L.) P. Beauv. var. cespitosa, D. cespitosa subsp. alpina (L.) Tzvelev, D. cespitosa subsp. beringensis (Hultén) W. E. Lawr., D. brevifolia R. Br., D. cespitosa (L.) P. Beauv. subsp. glauca (Hartm.) C. Hartm., D. mackenzieana Raup, D. cespitosa subsp. orientalis Hultén, and D. pumila (Griseb.) Ostenf. differed significantly in a few morphological variables, but molecularly are a closely related group with several sequences and haplotypes that are nearly identical. CONCLUSIONS: Overall, the evidence points to the existence of a single species, Deschampsia cespitosa. The occurrence of slightly different morphological types related to specific geographical distributions allows recognition of three additional taxa at the infraspecific level, D. cespitosa subsp. alpina, D. cespitosa subsp. beringensis, and D. brevifolia. All studied taxa showed morphological variation in a gradient, suggesting the existence of phenotypic plasticity.
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ADN de Plantas/genética , Genoma de Planta , Poaceae/genética , Secuencia de Bases , Canadá , Núcleo Celular/genética , Cloroplastos/genética , ADN de Cloroplastos/genética , ADN Intergénico/genética , Ambiente , Evolución Molecular , Heterogeneidad Genética , Marcadores Genéticos , Haplotipos , Análisis Multivariante , América del Norte , Fenotipo , Filogenia , Hojas de la Planta/genética , Hojas de la Planta/fisiología , Poaceae/clasificación , Poaceae/fisiología , Alineación de Secuencia , Análisis de Secuencia de ADN , Especificidad de la EspecieRESUMEN
Seed dispersal by animals is considered a pivotal ecosystem function that drives plant-community dynamics in natural habitats and vegetation recovery in human-altered landscapes. Nevertheless, there is a lack of suitable ecological knowledge to develop basic conservation and management guidelines for this ecosystem service. Essential questions, such as how well the abundance of frugivorous animals predicts seeding function in different ecosystems and how anthropogenic landscape heterogeneity conditions the role of dispersers, remain poorly answered. In three temperate ecosystems, we studied seed dispersal by frugivorous birds in landscape mosaics shaped by human disturbance. By applying a standardized design across systems, we related the frequency of occurrence of bird-dispersed seeds throughout the landscape to the abundance of birds, the habitat features, and the abundance of fleshy fruits. Abundance of frugivorous birds in itself predicted the occurrence of dispersed seeds throughout the landscape in all ecosystems studied. Even those landscape patches impoverished due to anthropogenic disturbance received some dispersed seeds when visited intensively by birds. Nonetheless, human-caused landscape degradation largely affected seed-deposition patterns by decreasing cover of woody vegetation or availability of fruit resources that attracted birds and promoted seed dispersal. The relative role of woody cover and fruit availability in seed dispersal by birds differed among ecosystems. Our results suggest that to manage seed dispersal for temperate ecosystem preservation or restoration one should consider abundance of frugivorous birds as a surrogate of landscape-scale seed dispersal and an indicator of patch quality for the dispersal function; woody cover and fruit resource availability as key landscape features that drive seedfall patterns; and birds as mobile links that connect landscape patches of different degrees of degradation and habitat quality via seed deposition.