High incidence of plant-animal mutualisms in the woody flora of the temperate forest of southern South America : biogeographical origin and present ecological significance

The flora of the temperate forest of southern South America highly depends on animals for pollination and seed dispersal. This resembles more tropical settings and distinguishes it from other temperate floras. This high mutualism-dependency seems paradoxical and potentially “anachronic” in view of this flora’s present interaction with an impoverished fauna. We analyzed the frequency of biotic pollination and seed dispersal across woody genera classified according to growth form and biogeographical affiliation. We found that genera that probably originated in warm or tropical like environments of ancient Gondwana and the Neotropics, two of the main biogeographical sources of this flora, had high incidences of biotic pollination and dispersal. The rich endemic foristic element, mostly related phylogenetically to these two foristic sources, also exhibited a high frequency of mutualism-dependency. Many endemic and Neotropical genera showed distinctive reproductive traits associated with bird pollination, a type of mutualism nearly absent in taxa with other biogeographical affiliations. This suggests that many southern South American plant taxa may have evolved novel mutualistic associations in situ, probably before the onset of present cooler climatic conditions. We propose that, despite the current relictual status of many of these genera and their associated reproductive traits, dependence on mutualists is not necessarily “anachronic” in today’s cool climate and depauperate faunal environment. Our finding that the average southernmost distribution limit is similar both for genera that depend on mutualists for either pollination or dispersal and for those that do not support this view. The steep W-E rainfall gradient created by the rising of the Andes represents a more potent ecological filter than the N-S temperature gradient, sorting out forest plant taxa according to their dependence on hummingbirds for pollination and vertebrates for dispersal. Overall, we believe that plant-animal mutualisms in the temperate forest of southern South America are still well suited interactions, because they rely on animals that are abundant and show a high degree of residency despite being represented by a low number of species. However, present human-induced elevated rates of deforestation, fragmentation and habitat degradation may be particularly threatening for mutualist-dependent plants due to low redundancy in alternative animal partners.Fil: Aizen, Marcelo A.. Universidad Nacional del Comahue - Departamento de Ecología, Bariloche, ArgentinaFil: Ezcurra, Cecilia. Universidad Nacional del Comahue - Departamento de Botánica, Bariloche, Argentin

The interplay between ovule number, pollination and resources as determinants of seed set in a modular plant

Background. A classical dichotomous perspective proposes that either pollination or plant resources limit seed production. However, ovule number could also be limiting when pollination results in complete ovule fertilization and there are more plant resources available than needed to develop seeds. Moreover, this dichotomous view assumes that all flowers of a plant have equal access to a shared pool of resources, although these are frequently compartmentalized within plant modules, e.g. inflorescences. How ovule number, pollination and resources affect seed production in physiologicallycompartmentalized rather than physiologically-integrated plants has yet to be explored. We used raspberry (Rubus idaeus) to address this question.Methods. We first assessed if ovule number affected the fraction of ovules that develop into seed (i.e. seed set) and whether this effect related to the extent of physiological integration among flowers within plants. This was achieved by statistically testing predictions on the sign and level of plant organization (i.e. among flowers within inflorescences, among inflorescences within ramets, and among ramets) of the relation between ovule number and seed set given different degrees of physiological integration. We then explored whether the relation between ovule number and seed set was affected by plant age (used here as a surrogate of resource availability) and pollination intensity (open pollination vs. exclusion).Results. Within inflorescences, flowers with more ovules set a larger fraction of seeds. On the other hand, seed set at the inflorescence level was negatively related to the average number of ovules per flower. Seed set increased with ovule number and open-pollination, and decreased with ramet age. However, ovule number explained more variation in seed set than ramet age and pollination treatment. Ramet age affected the strength of the relation of seed set to ovule number, which was stronger in old than young ramets. Pollination did not alter the strength of this relation to any significant extent.Discussion. Results reveal the importance of ovule number as an overriding factor affecting seed set. Within inflorescences, resources appear to be differentially allocated to developing fruits from flowers with many ovules. This is consistent with the fact that in raspberry a large proportion of the carbon invested in fruit development is fixed by the inflorescence subtending leaf. Differential resource allocation to flowers with many ovules is not affected by pollinator exclusion, being stronger in resourceexhausted ramets. This suggests that the effects of pollen limitation and resource allocation are compartmentalized at the inflorescence level. Consequently, modular plants can be viewed as reproductive mosaics where either ovule number, pollination or resources limit the number of seeds set by different flowers, so that improvements in any of them could increase plant seed production.Fil: Strelin, Marina Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentin

Worldwide occurrence records suggest a global decline in bee species richness

Wild and managed bees are key pollinators, ensuring or enhancing the reproduction of a large fraction of the world's wild flowering plants and the yield of ∼85% of all cultivated crops. Recent reports of wild bee decline and its potential consequences are thus worrisome. However, evidence is mostly based on local or regional studies; the global status of bee decline has not been assessed yet. To fill this gap, we analyzed publicly available worldwide occurrence records from the Global Biodiversity Information Facility spanning over a century. We found that after the 1990s, the number of collected bee species declines steeply such that approximately 25% fewer species were reported between 2006 and 2015 than before the 1990s. Although these trends must be interpreted cautiously given the heterogeneous nature of the dataset and potential biases in data collection and reporting, results suggest the need for swift actions to avoid further pollinator decline. Wild bee pollination is fundamental to the reproduction of hundreds of thousands of wild plant species and is key to securing adequate yields in about 85% of food crops. Declines in the abundance and diversity of bee species have been reported at local, regional, and country levels on different continents, but up to now there has not been a long-term assessment on global trends. We turned to publicly available data on specimen collections and observations gathered at the Global Biodiversity Information Facility, mostly coming from museum and academic collections and complemented by citizen-science efforts. We found that the number of bee species being collected or observed over time has been steadily declining since the 1990s. Although these results might in part reflect increased impediments to specimen collection and data mobilization, as well as reduced sampling coverage, they could also reflect a worldwide decline in bee diversity given that many species are becoming rarer and less likely to be found. Wild bees are key to pollination of wild and crop plants, and local and regional reports of their decline are cause for concern. Since there are no global long-term datasets of bee diversity, we analyzed historical occurrence data from collections and observations gathered by the Global Biodiversity Information Facility and found that the number of bee species worldwide has been steadily decreasing since the 1990s as a result of either concerted changes in data-gathering strategies or, most likely, an actual global decline in bee diversity.Fil: Zattara, Eduardo Enrique. Indiana University; Estados Unidos. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Wissenschaftskolleg zu Berlin; Alemani

The floral diversity of field margins influences the richness and abundance of native flower visitors in sunflower fields

La declinación en la diversidad y abundancia de polinizadores relacionada a diversos tipos de disturbios de origen antrópico es un tema de debate en el contexto del cambio en el uso de la tierra. Dentro de este debate se ha enfatizado la importancia de los remanentes de hábitats naturales y semi-naturales como reservorios de polinizadores para cultivos dependientes de ellos. El sudeste de la Provincia de Buenos Aires constituye una zona agrícolo-ganadera con un alto grado de uso y alteración de la tierra. Sin embargo, los márgenes de cultivos asociados a los bordes de caminos pueden proveer recursos florísticos y sitios de nidificación para una gran diversidad de polinizadores, los que podrían, eventualmente, incrementar la polinización y la productividad de muchos cultivos aledaños dependientes de ellos. Aquí evaluamos el efecto de la diversidad floral de los bordes de cultivos sobre la riqueza y abundancia de los visitantes florales en 17 lotes de girasol en la zona de Balcarce y Lobería. Nuestros resultados indican que la diversidad floral del borde tuvo un efecto positivo sobre la riqueza y abundancia de visitantes florales nativos en el cultivo adyacente. En consecuencia, los servicios de polinización en estos agroecosistemas podrían ser promovidos por un incremento en la cantidad y diversidad de estos hábitats marginales.Pollinator decline has been related to different types of anthropogenic disturbances, a topic largely debated in the context of global change. Within this debate, it has been stressed the importance of natural or semi-natural habitat remnants as pollinator sources for nearby agricultural fields. The SW of Buenos Aires Province is a highly-impacted and intensively-used agricultural region. However, field margins associated with country roads can provide diverse floristic resources and nesting sites for a variety of pollinators, which can eventually improve pollination and productivity of neighboring pollinator-dependent crops. Here, we evaluated the effect of floral diversity of field margins on the richness and abundance of floral visitors across 17 sunflower lots in the districts of Balcarce and Lobería. Our results indicate that floral diversity of field margins had a positive effect on the richness and abundance of native floral visitors in the adjacent crop field. As a consequence, pollination services in these agroecosystems would be promoted by increasing the amount and diversity of these marginal habitats.Fil: Sáez, Agustín. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Sabatino, Malena. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin

Approaches to the study of sexual plant reproduction in altered habitats : limitations and perspectives

Las interacciones planta-polinizador son susceptibles a diferentes tipos de perturbaciones de origen antrópico. Aunque se supone que las distintas actividades humanas tienen impactos disruptivos o negativos sobre estas interacciones, el signo y la magnitud de los mismos dependen de una serie de variables ambientales y atributos biológicos cuya modificación puede tener efectos de signo contrario sobre distintos componentes de estos mutualismos. En consecuencia, el impacto de las perturbaciones antrópicas sobre la polinización y éxito reproductivo de las plantas no es fácilmente predecible a priori, dependiendo también de la intensidad, escala espacial y frecuencia del disturbio. El enfoque empleado mayormente en esta clase de estudios es de tipo comparativo y reduccionista. Esto resulta en una falta en la comprensión de los factores mediatos e inmediatos involucrados en la respuesta reproductiva de las plantas a las perturbaciones, y a interpretaciones erróneas, o a lo sumo incompletas, asociadas a repuestas curvilíneas y a una replicación reducida. En este trabajo reviso distintos tipos de limitaciones relacionados a este enfoque y propongo uno alternativo, que si bien es de naturaleza correlativa, permite una comprensión más mecanicista y la puesta a prueba de hipótesis de causalidad. El enfoque propuesto también permite asimilar, en forma más natural, al diseño de muestreo los patrones de perturbación que usualmente se encuentran en el campo, mejor reflejados por gradientes que por clases discretas. Esta aproximación también implica una mayor integración entre las áreas de la ecología reproductiva de plantas y la del paisaje.Plant-pollinator interactions are susceptible to different types of anthropogenic disturbances. Although it is assumed that different human activities can disrupt these interactions, the direction and magnitude of their consequences are mediated by a series of environmental and biological variables that may have opposite effects on different aspects of these mutualisms. Therefore, the impact of human-driven habitat alteration on pollination and plant reproductive success can not be predicted a priori. The sign and magnitude of this impact will also depend on disturbance intensity, spatial scale and frequency. The current approach to study disturbance effects on plant reproduction is mostly comparative and highly reductionist (e.g., seed production is compared between disturbed vs. undisturbed sites). This approach leads to a lack of understanding on the proximal factors involved in the reproductive response of plants to habitat alteration, or even to incomplete or erroneous interpretations when responses are curvilinear or there is a low level of true replication. Here I review and comment on the different types of limitations arising from this comparative approach, and propose an alternative one. The proposed approach is exemplified in a simple conceptual model that can accommodate different aspects of the disturbance itself, including scale considerations, as well as aspects of plants, pollinators, and of the pollination process. This approach, even though of a correlative nature, allows a more mechanistic understanding of the effects of habitat disturbance on plant pollination and reproductive success by testing different proximal variables and causal models using path analysis and structural equation modeling. Also, the proposed approach can incorporate easily the disturbance patterns found in the field, better reflected in gradients than discrete classes. Finally, I advocate a greater integration between the mostly disconnected areas of plant reproductive ecology and landscape ecology

Mito y realidad de una crisis global de la polinización en la agricultura

Mounting evidence shows that pollinators are declining as a result of widespread environmental degradation. This loss raises concerns that a global pollination crisis could threaten the human food supply by decreasing crop yield and even promote famine under a hypothetical scenario of total pollinator extinction. This catastrophic possibility has prompted intense interest from scientists, politicians and the general public. However, three lines of evidence do not support such an apocalyptic scenario. First, even though the abundance and diversity of wild pollinators are declining worldwide, the global population of managed honey-bee hives has increased by ~80% since the early 1960s. Second, agricultural production would decrease by <10% in the total absence of bees because relatively few crops are completely pollinator dependent. Lastly, despite widespread pollination deficits, current evidence is inconsistent with deceleration in yield growth with increasing pollinator dependence at a global scale, probably due to improvements in crop breeding and external agricultural subsidies. Overall, this evidence refutes simplistic claims of human starvation caused by a hypothetical total pollinator extinction. Nevertheless, pollination problems may loom. Although pollinators are responsible for a minor fraction of global agriculture production, this fraction has increased ~600% since 1961, greatly outpacing human population growth and the growth of the global population of managed honey bees. This large production increase is explained to a considerable extent by the rapid expansion of pollinatordependent monocultures at the expense of natural and diverse agricultural habitats. By driving pollinator decline, this land-use transformation could worsen pollination deficits and promote further crop expansion given sustained market demands. Therefore, although the human food supply is not currently subject to a global pollination crisis, a spiralling positive-feedback between the impacts of agriculture expansion and pollinator decline on crop yield could accelerate precipitous biodiversity loss by promoting further habitat destruction and homogenization.Los polinizadores están disminuyendo como consecuencia de la degradación generalizada del medio ambiente. Esta pérdida ha suscitado la preocupación de que una crisis global de polinización pueda estar amenazando nuestro suministro de alimentos vía una reducción en el rendimiento agrícola. Sin embargo, tres líneas de evidencia no apoyan tal expectativa. Primero, aunque la abundancia y la diversidad de los polinizadores silvestres están disminuyendo en todo el mundo, la población mundial de colmenas de abejas melíferas manejadas ha aumentado en un ~80% desde principios de la década de 1960. Segundo, la producción agrícola disminuiría sólo <10% en ausencia total de abejas ya que relativamente pocos cultivos dependen completamente de los polinizadores. Por último, a nivel global no parece existir una desaceleración del crecimiento en el rendimiento con el incremento en la dependencia de los polinizadores. Sin embargo, la expansión de cultivos dependientes de polinizadores puede tener un alto costo ambiental. Aunque los polinizadores son responsables de una fracción menor de la producción agrícola mundial, esta fracción ha aumentado en un ~600% desde 1961, superando el crecimiento de la población mundial de abejas melíferas manejadas. El incremento de esta fracción de la agricultura se explica en gran medida por la rápida expansión de monocultivos dependientes de polinizadores. A través de incrementar la pérdida de polinizadores silvestres, esta transformación en el uso de la tierra puede causar un incremento en los déficits de polinización y promover la expansión de cultivos dependientes de polinizadores en respuesta a demandas sostenidas del mercado. Por lo tanto, una espiral de retroalimentación positiva entre la expansión de la agricultura y un declive de los polinizadores que afecte al rendimiento de los cultivos podría acelerar la enorme pérdida de biodiversidad en curso al promover la destrucción de los hábitats naturales remanentes y la homogeneización de los paisajes agrícolas.Fil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Garibaldi, Lucas Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. - Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; ArgentinaFil: Harder, Lawrence. University of Calgary; Canad

Pollination success increases with plant diversity in high-Andean communities

Pollinator-mediated plant–plant interactions have traditionally been viewed within the competition paradigm. However, facilitation via pollinator sharing might be the rule rather than the exception in harsh environments. Moreover, plant diversity could be playing a key role in fostering pollinator-mediated facilitation. Yet, the facilitative effect of plant diversity on pollination remains poorly understood, especially under natural conditions. By examining a total of 9371 stigmas of 88 species from nine high-Andean communities in NW Patagonia, we explored the prevalent sign of the relation between conspecific pollen receipt and heterospecific pollen diversity, and assessed whether the incidence of different outcomes varies with altitude and whether pollen receipt relates to plant diversity. Conspecific pollen receipt increased with heterospecific pollen diversity on stigmas. In all communities, species showed either positive or neutral but never negative relations between the number of heterospecific pollen donor species and conspecific pollen receipt. The incidence of species showing positive relations increased with altitude. Finally, stigmas collected from communities with more co-flowering species had richer heterospecific pollen loads and higher abundance of conspecific pollen grains. Our findings suggest that plant diversity enhances pollination success in high-Andean plant communities. This study emphasizes the importance of plant diversity in fostering indirect plant–plant facilitative interactions in alpine environments, which could promote species coexistence and biodiversity maintenance.Fil: Gavini, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Sáez, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Tur, Cristina. No especifíca;Fil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

Exotic insect pollinators and native pollination systems

Insect pollinators have been relocated by humans for millennia and are, thus, among the world’s earliest intentional exotic introductions. The introduction of managed bees for crop pollination services remains, to this day, a common and growing practice worldwide and the number of different bee species that are used commercially is increasing. Being generalists and frequently social, these exotic species have the potential to have a wide range of impacts on native bees and plants. Thus, understanding the consequences of introduced species on native pollinator systems is a priority. We generated a global database and evaluated the impacts of the two main groups of invasive bees, Apis mellifera and Bombus spp., on their pollination services to native flora and impacts on native pollinators. In a meta-analysis, we found that per-visit pollination efficiency of exotic pollinators was, on average, 55% less efficient than native pollinators when visiting flowers of native species. In contrast to per-visit pollination efficiency, our meta-analysis showed that visitation frequency by exotic pollinators was, on average, 80% higher than native pollinators. The higher visitation frequency of exotic pollinators overcame deficiencies in pollen removal and transfer resulting in seed/fruit set levels similar to native pollinators. Also, evidence showed that exotic pollinators can displace native insect and bird pollinators. However, the direct effects of exotic insect pollinators on native pollination systems can be context dependent, ranging from mutualism to antagonism.Fil: Debnam, Scott. University of Montana; Estados UnidosFil: Sáez, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Callaway, Ragan M.. University of Montana; Estados Unido

Ecological correlates of crop yield growth and interannual yield variation at a global scale

Artificial selection and genetic engineering plus an expanding repertoire and use of agrochemical inputs have allowed a rapid and continuous increase in crop yield (i.e., volume production per unit area) over the last century, which is needed to fulfill food demands from a growing human population. However, the first signs of yield deceleration and stagnation have already been reported for some globally important crops. Therefore, the study of the drivers of yield growth and its variation is essential for directing research and policies aiming at ensuring food security in the forthcoming years. We used data on mean and variability in annual yield growth for 107 globally important crops to assess the role of environmental (i.e., climatic region) and plant intrinsic traits (i.e., type of harvested organ, pollinator dependence, and life form) as drivers of change in yield growth and its stability. We applied a comparative approach to control for biases associated with phylogenetic non-independence among crops, an approach rarely used in agronomic studies. Average yield growth and its variation were not phylogenetically structured. Yield growth decreased with increasing pollinator dependence in tree crops but not in herbaceous and shrubby crops. Interannual yield variation tended to increase with increasing pollinator dependence, and it was higher in crops from temperate regions, in those cultivated for their reproductive organs, and in tree and shrubby crops as compared with herbaceous ones. Information on ecological correlates of crop yield growth and interannual yield variation can be used in the design of more sustainable and diversified agriculture schemes.Fil: Gleiser, Gabriela Laura. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Leme Da Cunha, Nicolay. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Sáez, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Aizen, Marcelo Adrian. Wissenschaftskolleg Zu Berlin; Alemania. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

Seed dispersal by birds in a temperate forest of southern South America: : who disperses to whom?

Un gran número de plantas depende de animales mutualistas para la dispersión de sus semillas, tarea principalmente realizada por aves que ingieren los frutos y defecan o regurgitan las semillas en forma intacta. El Bosque Templado de Sudamérica Austral (BTSA) se diferencia de otros biomas boscosos templados por poseer una gran proporción de plantas leñosas (~60% de los géneros) que producen frutos carnosos. Estudiamos las interacciones entre plantas y aves dispersoras en un bosque mésico dominado por Nothofagus dombeyi en la Reserva Municipal de Llao-Llao, Argentina (41° 00’S; 71°30´O), cerca del extremo oriental del BTSA. Las aves fueron capturadas utilizando ocho redes de niebla, y muestreadas por avistaje y sonido en cinco estaciones de conteo durante dos estaciones de fructificación. La dieta de las aves capturadas fue estimada mediante el lavado del tracto digestivo. Se estimó la disponibilidad de frutos carnosos en el área de estudio y se realizaron registros de la fenología de fructificación de las especies de plantas leñosas. Se capturaron un total de 296 individuos de 12 especies de aves. Restos de frutos carnosos y semillas fueron encontrados en sólo dos especies, una migrante, Elaenia albiceps, y otra residente, Turdus falcklandii. Estos frutos pertenecieron a ocho de las nueve especies de plantas leñosas productoras de frutos carnosos presentes en el bosque. Adicionalmente, las dos especies de aves fueron comunes en el área de estudio durante la estación de fructificación, representando el 52% y 9% de todas las capturas y el 35% y 4% en las estaciones de conteo, respectivamente. Resultados de un estudio similar en Chiloé, Chile, concuerdan en señalar la importancia de E. albiceps y T. falcklandii como especies claves en la dispersión de frutos del BTSA.Many plants depend on animals for seed dispersal, a task carried out mainly by birds that ingest fruits and defecate or regurgitate seeds undamaged. Unlike other temperate forest biomes, the Temperate Forest of Southern South America (TFSA) is characterized by a large proportion of woody plants (~ 60% of genera) producing fleshy fruits. We studied the interactions between plants and bird dispersers in a mesic forest dominated by Nothofagus dombeyi at the Llao-Llao Forest Reserve, Argentina (41°00’S; 71° 30´W), close to the eastern boundary of the TFSA. We sampled birds using eight mist-nets and five sight/sound census stations during two consecutive fruiting seasons (1999 - 2000). We also recorded the phenology and fruit availability of six tree and shrub species. Gut content analysis was used to determine which fruits were consumed by the dispersers. Through the two sampling methods, we surveyed a total of 23 bird species occurring in the study area. We captured a total of 296 birds belonging to 12 species. We found evidence of fleshy fruit consumption only in two species, Elaenia albiceps and Turdus falcklandii, that consumed fruits and defecated seeds of eight from the nine fleshy-fruited plant species locally present. These two bird species were common in the forest during the fruiting season accounting for 52% and 9% of all mist-net captures and 35% and 4% of all sight/sound censuses, respectively. Other birds consumed fruit or seeds (without dispersing them), insects, and/or small vertebrates. Phenological records indicated that most plant species bear ripe fruit during January and February. The most important fleshy-fruited plants in the area were Aristotelia maqui and Tristerix corymbosus; the latter dispersed by a marsupial. Results presented here, together with a similar study carried out in Chiloé, stress the importance of E. albiceps and T. falcklandii as key mutualists throughout the TFSA