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Evaluating the effects of pollinator‐mediated interactions using pollen transfer networks: evidence of widespread facilitation in south Andean plant communities 下载免费PDF全文
Information about the relative importance of competitive or facilitative pollinator‐mediated interactions in a multi‐species context is limited. We studied interspecific pollen transfer (IPT) networks to evaluate quantity and quality effects of pollinator sharing among plant species on three high‐Andean communities at 1600, 1800 and 2000 m a.s.l. To estimate the sign of the effects (positive, neutral or negative), the relation between conspecific and heterospecific pollen deposited on stigmas was analysed with GLMMs. Network analyses showed that communities were characterised by the presence of pollen hub‐donors and receptors. We inferred that facilitative and neutral pollinator‐mediated interactions among plants prevailed over competition. Thus, the benefits from pollinator sharing seem to outweigh the costs (i.e. heterospecific deposition and conspecific pollen loss). The largest proportion of facilitated species was found at the highest elevation community, suggesting that under unfavourable conditions for the pollination service and at lower plant densities facilitation can be more common. 相似文献
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Pollen transfer by hummingbirds and bumblebees, and the divergence of pollination modes in Penstemon 总被引:2,自引:0,他引:2
Castellanos MC Wilson P Thomson JD 《Evolution; international journal of organic evolution》2003,57(12):2742-2752
We compared pollen removal and deposition by hummingbirds and bumblebees visiting bird-syndrome Penstemon barbatus and bee-syndrome P. strictus flowers. One model for evolutionary shifts from bee pollination to bird pollination has assumed that, mostly due to grooming, pollen on bee bodies quickly becomes unavailable for transfer to stigmas, whereas pollen on hummingbirds has greater carryover. Comparing bumblebees and hummingbirds seeking nectar in P. strictus, we confirmed that bees had a steeper pollen carryover curve than birds but, surprisingly, bees and birds removed similar amounts of pollen and had similar per-visit pollen transfer efficiencies. Comparing P. barbatus and P. strictus visited by hummingbirds, the bird-syndrome flowers had more pollen removed, more pollen deposited, and a higher transfer efficiency than the bee-syndrome flowers. In addition, P. barbatus flowers have evolved such that their anthers and stigmas would not easily come into contact with bumblebees if they were to forage on them. We discuss the role that differences in pollination efficiency between bees and hummingbirds may have played in the repeated evolution of hummingbird pollination in Penstemon. 相似文献
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Gidi Ne'eman Andreas Jürgens Linda Newstrom‐Lloyd Simon G. Potts Amots Dafni 《Biological reviews of the Cambridge Philosophical Society》2010,85(3):435-451
Measuring pollinator performance has become increasingly important with emerging needs for risk assessment in conservation and sustainable agriculture that require multi‐year and multi‐site comparisons across studies. However, comparing pollinator performance across studies is difficult because of the diversity of concepts and disparate methods in use. Our review of the literature shows many unresolved ambiguities. Two different assessment concepts predominate: the first estimates stigmatic pollen deposition and the underlying pollinator behaviour parameters, while the second estimates the pollinator's contribution to plant reproductive success, for example in terms of seed set. Both concepts include a number of parameters combined in diverse ways and named under a diversity of synonyms and homonyms. However, these concepts are overlapping because pollen deposition success is the most frequently used proxy for assessing the pollinator's contribution to plant reproductive success. We analyse the diverse concepts and methods in the context of a new proposed conceptual framework with a modular approach based on pollen deposition, visit frequency, and contribution to seed set relative to the plant's maximum female reproductive potential. A system of equations is proposed to optimize the balance between idealised theoretical concepts and practical operational methods. Our framework permits comparisons over a range of floral phenotypes, and spatial and temporal scales, because scaling up is based on the same fundamental unit of analysis, the single visit. 相似文献
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Patterns of among‐ and within‐species variation in heterospecific pollen receipt: The importance of ecological generalization 下载免费PDF全文
Gerardo Arceo‐Gómez Luis Abdala‐Roberts Anneka Jankowiak Clare Kohler George A. Meindl Carmen M. Navarro‐Fernández Víctor Parra‐Tabla Tia‐Lynn Ashman Conchita Alonso 《American journal of botany》2016,103(3):396-407
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Variation in sampling effort affects the observed richness of plant–plant interactions via heterospecific pollen transfer: implications for interpretation of pollen transfer networks 下载免费PDF全文
Gerardo Arceo‐Gómez Conchita Alonso Tia‐Lynn Ashman Victor Parra‐Tabla 《American journal of botany》2018,105(9):1601-1608
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? Premise of the study: Exceptions to the ideal of complete reproductive isolation between species are commonly encountered in diverse plant, animal, and fungal groups, but often the causative ecological processes are poorly understood. In flowering plants, the outcome of hybridization depends in part on the effectiveness of pollinators in interspecific pollen transport. In the Asclepias exaltata and A. syriaca (Apocynaceae) hybrid zone in Shenandoah National Park, Virginia, extensive introgression has been documented. The objectives of this study were to (1) determine the extent of pollinator overlap among A. exaltata, A. syriaca, and their hybrids and (2) identify the insect taxa responsible for hybridization and introgression. ? Methods: We observed focal plants of parental species and hybrids to measure visitation rate, visit duration, and per-visit pollinia removal and deposition, and we calculated pollinator effectiveness and importance. ? Key results: Visitation rates varied significantly between the 2 yr of the study. Overall, Apis mellifera, Bombus sp., and Epargyreus clarus were the most important pollinators. However, Bombus sp. was the only visitor that was observed to both remove and insert pollinia for both parent species as well as hybrids. ? Conclusions: We conclude that Bombus may be a key agent of hybridization and introgression in these sympatric milkweed populations, and hybrids are neither preferred nor selected against by pollinators. Thus, we have identified a potential mechanism for how hybrids act as bridges to gene flow between A. exaltata and A. syriaca. These results provide insights into the breakdown of prezygotic isolating mechanisms. 相似文献
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Abstract The frequency of hybrids was monitored using progenies grown from seeds collected from open-pollinated plants in mixed populations of Farfugium hiberniflorium and F. japonicum . The results showed that hybrids are more frequently derived from F. japonicum than from F. hiberniflorum . This directionality of hybridization and extraordinarily high frequency of hybrids among progenies grown from seeds from open-pollinated plants of F. japonicum enabled us to derive an empirical equation describing the frequency of hybridization as a decreasing exponential function of interspecific plant distance. The relationship between these two variables fitted a function describing pollen flow from a particular plant. This finding suggests that interspecific pollen exchange can be viewed simply as a process dependent of interspecific plant distance, and the actual rate of hybridization is determined by the level of cross-compatibility of a particular species. 相似文献
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