INSECT POLLINATORS AND THEIR CHALLENGES: A REVIEW (original) (raw)
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Plant-pollinator interactions over 120 years: loss of species, co-occurrence, and function
Science (New York, N.Y.), 2013
Using historic data sets, we quantified the degree to which global change over 120 years disrupted plant-pollinator interactions in a temperate forest understory community in Illinois, USA. We found degradation of interaction network structure and function and extirpation of 50% of bee species. Network changes can be attributed to shifts in forb and bee phenologies resulting in temporal mismatches, nonrandom species extinctions, and loss of spatial co-occurrences between extant species in modified landscapes. Quantity and quality of pollination services have declined through time. The historic network showed flexibility in response to disturbance; however, our data suggest that networks will be less resilient to future changes.
Plant–pollinator networks: adding the pollinator’s perspective
Ecology Letters, 2009
Pollination network studies are based on pollinator surveys conducted on focal plants. This plant‐centred approach provides insufficient information on flower visitation habits of rare pollinator species, which are the majority in pollinator communities. As a result, pollination networks contain very high proportions of pollinator species linked to a single plant species (extreme specialists), a pattern that contrasts with the widely accepted view that plant–pollinator interactions are mostly generalized. In this study of a Mediterranean scrubland community in NE Spain we supplement data from an intensive field survey with the analysis of pollen loads carried by pollinators. We observed 4265 contacts corresponding to 19 plant and 122 pollinator species. The addition of pollen data unveiled a very significant number of interactions, resulting in important network structural changes. Connectance increased 1.43‐fold, mean plant connectivity went from 18.5 to 26.4, and mean pollinator c...
Supporting crop pollinators with floral resources: network-based phenological matching
Ecology and Evolution, 2013
The production of diverse and affordable agricultural crop species depends on pollination services provided by bees. Indeed, the proportion of pollinatordependent crops is increasing globally. Agriculture relies heavily on the domesticated honeybee; the services provided by this single species are under threat and becoming increasingly costly. Importantly, the free pollination services provided by diverse wild bee communities have been shown to be sufficient for high agricultural yields in some systems. However, stable, functional wild bee communities require floral resources, such as pollen and nectar, throughout their active season, not just when crop species are in flower. To target floral provisioning efforts to conserve and support native and managed bee species, we apply network theoretical methods incorporating plant and pollinator phenologies. Using a two-year dataset comprising interactions between bees (superfamily Apoidea, Anthophila) and 25 native perennial plant species in floral provisioning habitat, we identify plant and bee species that provide a key and central role to the stability of the structure of this community. We also examine three specific case studies: how provisioning habitat can provide temporally continuous support for honeybees (Apis mellifera) and bumblebees (Bombus impatiens), and how resource supplementation strategies might be designed for a single genus of important orchard pollinators (Osmia). This framework could be used to provide native bee communities with additional, well-targeted floral resources to ensure that they not only survive, but also thrive.
Pollinators visit related plant species across 29 plant-pollinator networks
Ecology and Evolution, 2014
Understanding the evolution of specialization in host plant use by pollinators is often complicated by variability in the ecological context of specialization. Flowering communities offer their pollinators varying numbers and proportions of floral resources, and the uniformity observed in these floral resources is, to some degree, due to shared ancestry. Here, we find that pollinators visit related plant species more so than expected by chance throughout 29 plant-pollinator networks of varying sizes, with "clade specialization" increasing with community size. As predicted, less versatile pollinators showed more clade specialization overall. We then asked whether this clade specialization varied with the ratio of pollinator species to plant species such that pollinators were changing their behavior when there was increased competition (and presumably a forced narrowing of the realized niche) by examining pollinators that were present in at least three of the networks. Surprisingly, we found little evidence that variation in clade specialization is caused by pollinator species changing their behavior in different community contexts, suggesting that clade specialization is observed when pollinators are either restricted in their floral choices due to morphological constraints or innate preferences. The resulting pollinator sharing between closely related plant species could result in selection for greater pollinator specialization.
Pollination ecology: Understanding plant-pollinator relationships
International Journal of Research in Agronomy, 2024
Pollination, the transfer of pollen between flowers, forms the very foundation of plant reproduction and ecosystem health. Pollination ecology delves into the intricate and fascinating relationships between flowering plants and their pollinators, a story of coevolution spanning millions of years. Pollination ecology is a multidisciplinary field that explores the intricate relationships between plants and their pollinators, encompassing a diverse array of species interactions, ecological processes, and environmental dynamics. Understanding these plant-pollinator relationships is essential for elucidating the mechanisms of pollination, the ecological and evolutionary consequences of these interactions, and the factors shaping their stability and resilience. This article explores the various approaches used to understand these vital partnerships. At the heart lies the intricate language of flowers. Plants advertise their wares through a symphony of colors, scents, and shapes, each meticulously designed to attract specific pollinators. This study delves into the adaptations employed by plants, from vibrant flower displays to nectar production, to entice and reward their pollinators. Conversely, it explores how pollinators, primarily insects, birds, and bats, have coevolved specialized behaviors and morphologies to efficiently access pollen and nectar. It further explores the delicate balance and mutual benefit within these relationships. Plants rely on pollinators to transfer pollen and ensure successful reproduction, while pollinators depend on pollen and nectar for sustenance. This intricate dance, however, faces threats from habitat loss, climate change, and pesticide use. The study concludes by highlighting the importance of pollination ecology in understanding these threats and promoting sustainable practices that safeguard this vital ecological process.
Ecology Letters, 2014
Co-flowering plant species commonly share flower visitors, and thus have the potential to influence each other's pollination. In this study we analysed 750 quantitative plant-pollinator networks from 28 studies representing diverse biomes worldwide. We show that the potential for one plant species to influence another indirectly via shared pollinators was greater for plants whose resources were more abundant (higher floral unit number and nectar sugar content) and more accessible. The potential indirect influence was also stronger between phylogenetically closer plant species and was independent of plant geographic origin (native vs. non-native). The positive effect of nectar sugar content and phylogenetic proximity was much more accentuated for bees than for other groups. Consequently, the impact of these factors depends on the pollination mode of plants, e.g. bee or fly pollinated. Our findings may help predict which plant species have the greatest importance in the functioning of plant-pollination networks.
Phenological shifts drive biodiversity loss in plant--pollinator networks
2020
Plant-pollinator interactions are key for ecosystem maintenance and world crop production, and their occurrence depends on the synchronization of life-cycle events among interacting species. Phenological shifts observed for plant and pollinator species increase the risk of phenological mismatches, threatening community stability. However, the magnitudes and directions of phenological shifts present a high variability, both among communities and among species of the same community. Community-wide consequences of these different responses have not been explored. Additionally, variability in phenological and topological traits of species can affect their persistence probability under phenological changes. We explored the consequences of several scenarios of plant-pollinator phenological mismatches for community stability. We also assessed whether species attributes can predict species persistence under phenological mismatch. To this end, we used a dynamic model for plant-pollinator networks. The model incorporates active and latent life-cycle states of species and phenological dynamics regulating life-cycle transitions. Interaction structure and species phenologies were extracted from eight empirical plant-pollinator networks sampled at three locations during different periods. We found that for all networks and all scenarios, species persistence decreased with increasing magnitude of the phenological shift, for both advancements and delays in flowering phenologies. Changes in persistence depended on the scenario and the network being tested. However, all networks exhibited the lowest species persistence when the mean of the expected shift was equivalent to its standard deviation and this shift was greater than two weeks. Conversely, the highest species persistences occurred when earlier-flowering plants exhibited stronger shifts. Phenophase duration was the most important attribute as a driver of plant persistence. For pollinator persistence, species degree was the most important attribute, followed by phenophase duration. Our findings highlight the importance of phenologies on the stability and robustness of mutualistic networks.
What do we know about the effects of landscape changes on plant–pollinator interaction networks?
Ecological Indicators, 2013
Biotic interactions play an important role on the organization and persistence of biodiversity. Unnatural modifications of landscape structure such as habitat loss and fragmentation can isolate populations and disrupt biological communities, affecting species survival and altering the complex set of relationships between plants and pollinators. Plant-pollinator interaction networks have characteristics such asymmetry and nestedness that may influence the stability and robustness of networks to landscape changes. Species in mutualistic networks might respond to landscape modifications with a sudden collapse at critical habitat destruction thresholds. In this work we review general trends in the scientific literature related to the effects of landscape changes on plant-pollinator networks. For this, a survey in Scopus and Web of Knowledge databases was conducted in May 2011 using all seven possible combinations of the terms "pollinat*" with the terms "landscape", "habitat loss" and "network". We found 155 papers and 92% of those showed significant effects of landscape changes on pollinator diversity and plant reproductive success. Approximately 50% of all analyzed papers showed effects of agriculture intensification as a result of increases in the conversion of natural areas into agricultural crops on plant-pollinator interactions. Landscape modifications affected cross-pollination and the sexual reproduction of plants largely because of reduced diversity and availability of pollinators due to increased habitat isolation and reduction of floral resources and nesting areas in the remaining available habitat. An integrated approach concerning the effects of modified landscapes on natural ecosystems regarding how these variations can affect the stability and robustness of pollination networks can be extremely useful for conservation of plant-pollinators interactions, with positive overall consequences for conservation of plant, pollinators and pollination services in natural and agricultural ecosystems.
Tolerance of pollination networks to species extinctions
Proceedings of the Royal Society B: Biological Sciences, 2004
Mutually beneficial interactions between flowering plants and animal pollinators represent a critical 'ecosystem service' under threat of anthropogenic extinction. We explored probable patterns of extinction in two large networks of plants and flower visitors by simulating the removal of pollinators and consequent loss of the plants that depend upon them for reproduction. For each network, we removed pollinators at random, systematically from least-linked (most specialized) to most-linked (most generalized), and systematically from most-to least-linked. Plant species diversity declined most rapidly with preferential removal of the most-linked pollinators, but declines were no worse than linear. This relative tolerance to extinction derives from redundancy in pollinators per plant and from nested topology of the networks. Tolerance in pollination networks contrasts with catastrophic declines reported from standard food webs. The discrepancy may be a result of the method used: previous studies removed species from multiple trophic levels based only on their linkage, whereas our preferential removal of pollinators reflects their greater risk of extinction relative to that of plants. In both pollination networks, the most-linked pollinators were bumble-bees and some solitary bees. These animals should receive special attention in efforts to conserve temperate pollination systems.
Pollinators communities differ across years and crops
Plant, Soil and Environment
Insect pollination is one of the most important ecosystem services. Pollinator communities are rarely studied across years and crops in the same location. The aim of this study was to investigate the pollinator community structure on five different fruit crops, as well as the activity of different pollinator groups during the day and their temperature preferences. Pollinator activity was observed across two years on apple trees and blueberry, strawberry, blackcurrant and raspberry bushes. Pollinator community structure varied by plant and year. Honeybees were the most numerous pollinators on all plants except blueberry bushes (39–95% of visits). Bumblebee numbers were high on blackcurrant (up to 28%) and blueberry bushes (up to 61%). Solitary bees visited all plants except blueberries. Honeybees, solitary bees, and hoverflies were most active in the middle of the day, while bumblebees became active earlier in the morning and remained active later in the evening. Pollinators also dif...