Anthropogenic habitat disturbance is a strong biodiversity change driver that compromises not only the species persistence but also the ecological interactions in which they are involved. Even though seed dispersal is a key interaction involved in the recruitment of many tree species and in consequence critical for biodiversity maintenance, studies assessing the effect of different anthropogenic disturbance drivers on this interaction have not been performed under a meta-analytical framework. We assessed the way habitat fragmentation and degradation processes affect species diversity (abundance and species richness) and interaction rates (i.e., fruit removal and visitation rates) of different groups of seed-disperser species at a global scale. We obtained 163 case studies from 37 articles. Results indicate that habitat degradation had a negative effect on seed-disperser animal diversity, whereas habitat fragmentation had a negative effect on interaction rates. Birds and insects were more sensitive in terms of their diversity, whereas mammals showed a negative effect on interaction rates. Regarding habitat, both fragmentation and degradation had a negative effect on seed-disperser animal diversity only in temperate habitats, and negative effects on interaction rates in tropical and temperate habitats. Our results indicate that the impact of human disturbance on seed-disperser species and interactions is not homogeneous. On the contrary, the magnitude of effects seems to be dependent on the type of disturbance, taxonomic group under assessment, and geographical region where the human impact occurs.
We conducted a systematic review of the scientific literature published on plant-pollinator interactions, from both the plant and pollinator perspective, in the Chilean Mediterranean-type ecosystem (MTE hereafter). Our search identified 69 published papers on 235 native plant species from 62 families. Less than 7.9% of the flowering species inhabiting the Chilean Mediterranean have been studied, and most studies were restricted to only one locality and one reproductive season. The geographic location of the studies differed from a random pattern, showing two well-defined areas where most studies were conducted. Likewise, most studies in the Andes Range were performed above 2000 m a.s.l. The number of species of flower visitor per plant species was low (4.25 ± 0.22), which probably results from the historical and biogeographic isolation of Chile. This literature survey shows that studies relating floral traits with pollinator attraction and plant reproduction are the most frequent topics of research, reaching 37.6% of studies, followed by studies that examine pollination in relation to human impact (16.1%), micro- and macroevolution (14.0%), relationships between pollination and other ecological interactions (10.8%), community and network assessments (11.8%), and effects of abiotic variables on pollination interactions (9.7%). Our review highlights a lack of research on the effects of pollination for anthropogenic land use especially as agricultural practice is one of the most salient features of the Chilean MTE. Future directions to increase our understanding of the role of plant-pollinator relationships for biodiversity maintenance should include: to extend the taxonomic and geographic scope of research, to increase the number of spatial and temporal replicates, to increase the number of studies on pollination networks as they provide estimates of community complexity and putative stability, to develop studies that estimate the importance of pollination for plant demographic parameters and conservation, and to conduct studies that estimate the ecological service provided by Chilean native pollinators for crop yield and sustainable agriculture.
G. L. Stebbins' most effective pollinator principle states that when pollinators are not limiting, plants are expected to specialize and adapt to the most abundant and effective pollinator species available. In this study, we quantify the effectiveness of bees, hummingbirds and hawkmoths in a Chilean population of (Phrymaceae), and examine whether flower traits are subject to pollinator-mediated selection by the most effective pollinator species during two consecutive years. Unlike most species in the pollinator community, the visitation rate of the recently arrived did not change substantially between years, which together with its high and stable pollen delivery to flower stigmas made this species the most important in the pollinator assemblage, followed by the solitary bee Flower traits were under significant selection in the direction expected for short-tongue bees, suggesting that is in the initial steps of adaptation to the highly effective exotic bumblebee Our results illustrate the applicability of Stebbins' principle for new invasive pollinators, and stress their importance in driving flower adaptation of native plant species, a critical issue in the face of biotic exchange and homogenization.
Herbivory has been long considered an important component of plant-animal interactions that influences the success of invasive species in novel habitats. One of the most important hypotheses linking herbivory and invasion processes is the enemy-release hypothesis, in which exotic plants are hypothesized to suffer less herbivory and fitness-costs in their novel ranges as they leave behind their enemies in the original range. Most evidence, however, comes from studies on leaf herbivory, and the importance of flower herbivory for the invasion process remains largely unknown. Here we present the results of a meta-analysis of the impact of flower herbivory on plant reproductive success, using as moderators the type of damage caused by floral herbivores and the residence status of the plant species. We found 51 papers that fulfilled our criteria. We also included 60 records from unpublished data of the laboratory, gathering a total of 143 case studies. The effects of florivory and nectar robbing were both negative on plant fitness. The methodology employed in studies of flower herbivory influenced substantially the outcome of flower damage. Experiments using natural herbivory imposed a higher fitness cost than simulated herbivory, such as clipping and petal removal, indicating that studies using artificial herbivory as surrogates of natural herbivory underestimate the real fitness impact of flower herbivory. Although the fitness cost of floral herbivory was high both in native and exotic plant species, floral herbivores had a three-fold stronger fitness impact on exotic than native plants, contravening a critical element of the enemy-release hypothesis. Our results suggest a critical but largely unrecognized role of floral herbivores in preventing the spread of introduced species into newly colonized areas.
Artículo de publicación ISI.The arrival of exotic pollinators to new habitats may introduce new patterns of floral preference and foraging behavior that modify the structure of the resident plant-pollinator community. The aim of this paper is to examine the potential impact of the exotic bumblebee Bombus terrestris on the pollination service provided by the native pollinator assemblage of the herb Mimulus luteus. The study was performed in a high-elevation locality in the Chilean Andes during the summer seasons of 2010, 2011, and 2012. We recorded visitation rate, and the number of pollen grains transported on the body of B. terrestris and native pollinators and the pollen deposition on the stigmas of M. luteus. Pollinator effectiveness (pollen deposited x visitation rate) was compared among species. Results revealed that B. terrestris was an inefficient pollinator, due to the low amount of pollen delivered on stigmas and the low and intermittent visitation rate across years. The parallel inter-annual variation in the visitation rate of B. terrestris and the native bumblebee Bombus dahlbomii suggests that the integration of B. terrestris had no important consequences for the congeneric species. In general, B. terrestris accounted for a low proportion of the pollen transfer in M. luteus, reaching 4.6 % in 2010, absence of effect in 2011, and 0.01 % in 2012. These results suggest that in spite of being a quickly spreading species in Chile, B. terrestris is still in the initial phase of invasion in this area.FONDECYT 1120155 and ACT 34/2006
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