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The American Naturalist Apr 2024AbstractEcologists increasingly recognize that interactions between two species can be affected by the density of a third species. How these higher-order interactions...
AbstractEcologists increasingly recognize that interactions between two species can be affected by the density of a third species. How these higher-order interactions (HOIs) affect species persistence remains poorly understood. To explore the effect of HOIs stemming from multiple trophic layers on a plant community composition, we experimentally built a mesocosm with three plants and three pollinator species arranged in a fully nested and modified network structure. We estimated pairwise interactions among plants and between plants and pollinators, as well as HOIs initiated by a plant or a pollinator affecting plant species pairs. Using a structuralist approach, we evaluated the consequences of the statistically supported HOIs on the persistence probability of each of the three competing plant species and their combinations. HOIs substantially redistribute the strength and sign of pairwise interactions between plant species, promoting the opportunities for multispecies communities to persist compared with a non-HOI scenario. However, the physical elimination of a plant-pollinator link in the modified network structure promotes changes in per capita pairwise interactions and HOIs, resulting in a single-species community. Our study provides empirical evidence of the joint importance of HOIs and network structure in determining species persistence within diverse communities.
Topics: Pollination; Plants
PubMed: 38489780
DOI: 10.1086/729222 -
Frontiers in Plant Science 2023Monoecy is usually interpreted as an important evolutionary route of the plant sexual system from hermaphroditism to dioecy. This floral mechanism can effectively reduce...
INTRODUCTION
Monoecy is usually interpreted as an important evolutionary route of the plant sexual system from hermaphroditism to dioecy. This floral mechanism can effectively reduce self-interference during the reproductive process, and the services provided by pollinators may play an essential role in monoecious species; however, relevant research is still lacking. Thus, we aimed to determine whether monoecious plants could effectively avoid self-interference and promote the evolution of monoecy under the service of pollinators.
METHODS
Here, we successfully performed manipulation experiments to test self-compatibility, pollinator behavior, and self-interference between male and female functions in , a typical monoecious species.
RESULTS
We demonstrated that experimental self-pollination did not yield any fruit, and supplemental pollination significantly increased fruit set and fruit weight compared to natural pollination, suggesting that this species is completely self-incompatible and experiences strong pollen limitation. Simultaneous self- and cross-pollination and self-pollination prior to cross-pollination significantly reduced reproductive fitness, but self-pollination after cross-pollination did not, indicating self-interference in this plant. Moreover, both male flower probing preference and switching modes within inflorescences by pollinators successfully reinforced self-interference and were also responsible for decreasing reproductive fitness in . .
DISCUSSION
In summary, pollinator-mediated self-interference significantly reduced selfing, providing potential dynamics for the maintenance and evolution of monoecy.
PubMed: 37881614
DOI: 10.3389/fpls.2023.1243764 -
PNAS Nexus Jun 2024The discourse surrounding the structural organization of mutualistic interactions mostly revolves around modularity and nestedness. The former is known to enhance the...
The discourse surrounding the structural organization of mutualistic interactions mostly revolves around modularity and nestedness. The former is known to enhance the stability of communities, while the latter is related to their feasibility, albeit compromising the stability. However, it has recently been shown that the joint emergence of these structures poses challenges that can eventually lead to limitations in the dynamic properties of mutualistic communities. We hypothesize that considering compound arrangements-modules with internal nested organization-can offer valuable insights in this debate. We analyze the temporal structural dynamics of 20 plant-pollinator interaction networks and observe large structural variability throughout the year. Compound structures are particularly prevalent during the peak of the pollination season, often coexisting with nested and modular arrangements in varying degrees. Motivated by these empirical findings, we synthetically investigate the dynamics of the structural patterns across two control parameters-community size and connectance levels-mimicking the progression of the pollination season. Our analysis reveals contrasting impacts on the stability and feasibility of these mutualistic communities. We characterize the consistent relationship between network structure and stability, which follows a monotonic pattern. But, in terms of feasibility, we observe nonlinear relationships. Compound structures exhibit a favorable balance between stability and feasibility, particularly in mid-sized ecological communities, suggesting they may effectively navigate the simultaneous requirements of stability and feasibility. These findings may indicate that the assembly process of mutualistic communities is driven by a delicate balance among multiple properties, rather than the dominance of a single one.
PubMed: 38881844
DOI: 10.1093/pnasnexus/pgae209 -
PeerJ 2023Mutualistic interactions between plants and their pollinating insects are critical to the maintenance of biodiversity. However, we have yet to demonstrate that we are...
BACKGROUND
Mutualistic interactions between plants and their pollinating insects are critical to the maintenance of biodiversity. However, we have yet to demonstrate that we are able to manage the structural properties of these networks for the purposes of pollinator conservation and preserving functional outcomes, such as pollination services. Our objective was to explore the extent of our ability to experimentally increase, decrease, and maintain connectance, a structural attribute that reflects patterns of insect visitation and foraging preferences. Patterns of connectance relate to the stability and function of ecological networks.
METHODS
We implemented a 2-year field experiment across eight sites in urban Dublin, Ireland, applying four agrochemical treatments to fixed communities of seven flowering plant species in a randomized block design. We spent ~117 h collecting 1,908 flower-visiting insects of 92 species or morphospecies with standardized sampling methods across the 2 years. We hypothesized that the fertilizer treatment would increase, herbicide decrease, and a combination of both maintain the connectance of the network, relative to a control treatment of just water.
RESULTS
Our results showed that we were able to successfully increase network connectance with a fertilizer treatment, and maintain network connectance with a combination of fertilizer and herbicide. However, we were not successful in decreasing network connectance with the herbicide treatment. The increase in connectance in the fertilized treatment was due to an increased species richness of visiting insects, rather than changes to their abundance. We also demonstrated that this change was due to an increase in the realized proportion of insect visitor species rather than increased visitation by common, generalist species of floral visitors. Overall, this work suggests that connectance is an attribute of network structure that can be manipulated, with implications for management goals or conservation efforts in these mutualistic communities.
Topics: Animals; Fertilizers; Insecta; Pollination; Plants; Herbicides
PubMed: 38025756
DOI: 10.7717/peerj.16319 -
Annals of Botany Mar 2024Floral characteristics vary significantly among plant species, and multiple underlying factors govern this diversity. Although it is widely known that spatial variation...
BACKGROUND AND AIMS
Floral characteristics vary significantly among plant species, and multiple underlying factors govern this diversity. Although it is widely known that spatial variation in pollinator groups can exert selection on floral traits, the relative contribution of pollinators and climate to the variation of floral traits across large geographic areas remains a little-studied area. Besides furthering our conceptual understanding of these processes, gaining insight into the topic is also of conservation relevance: understanding how climate may drive floral traits variation can serve to protect plant-pollinator interactions under global change conditions.
METHODS
We used Rhododendron as a model system and collected floral traits (corolla length, nectar volume and concentrations), floral visitors, and climatic data on 21 Rhododendron species across two continents (North America-Appalachians and Asia-Himalaya). Based on this we quantified the influence of climate and pollinators to floral traits using phylogeny-informed analyses.
KEY RESULTS
Our results indicate that there is substantial variation in pollinators and morphological traits across Rhododendron species and continents. We came across four pollinator groups: birds, bees, butterflies, and flies. Asian species were commonly visited by birds, bees, and flies, while bees and butterflies were the most common visitors of North American species. The visitor identity explained nectar trait variation, with flowers visited by birds presenting higher volumes of dilute nectar and those visited by insects producing concentrated nectar. Nectar concentration and corolla length exhibited a strong phylogenetic signal across the analysed set of species. We also found that nectar trait variation in the Himalaya could also be explained by climate, which presented significant interactions with pollinator identity.
CONCLUSIONS
Our results indicate that both pollinators and climate contribute and interact to drive nectar trait variation, suggesting that both can affect pollination interactions and floral (and plant) evolution individually and interacting with each other.
PubMed: 38502826
DOI: 10.1093/aob/mcae046 -
PloS One 2023As the current climate crisis intensifies, drought resistant crops are becoming more important due to their ability to withstand the increasingly hotter and drier...
As the current climate crisis intensifies, drought resistant crops are becoming more important due to their ability to withstand the increasingly hotter and drier summers. Such crops are valuable for pollinators as they provide food resources for wild and managed species. The carob tree (Ceratonia siliqua L.) represents an example of a heat- and drought- resistant crop, able to grow in dry areas with practically no inputs. The current study assessed over two growing seasons the diversity of wild bees and other pollinators relying on carob flowers, as well as the contribution of animal pollination to carob production. Carob flowers were subjected to two treatments: Open pollination, where inflorescences were left untreated, and wind pollination, where inflorescences were bagged in a mesh during blooming. Weekly observations during blooming showed that Apis mellifera was the most frequent floral visitor followed by wild bees and wasps. Carob flowers were visited by at least 10 different wild bee species. Open-pollinated flowers produced significantly more pods, with the benefit ranging from 4 to 16 times higher production, depending on the region. Open pollination led to pods with greater weight, length and number of seeds compared to pods derived from wind pollination. The results of the current study highlight the importance of animal pollination to carob production, as well as the significance of carob trees to wild bee conservation.
Topics: Bees; Animals; Biodiversity; Crops, Agricultural; Seeds; Wasps; Flowers; Pollination
PubMed: 37862335
DOI: 10.1371/journal.pone.0291431 -
Plants (Basel, Switzerland) Mar 2024For a long time, it was considered that entomogamy was the only pollination mechanism in the Mediterranean area. However, data recorded in this review prove that... (Review)
Review
For a long time, it was considered that entomogamy was the only pollination mechanism in the Mediterranean area. However, data recorded in this review prove that ornithogamy and saurogamy also take place. With the exception of the nectarivorous (Nectariniidae) which pollinates the mistletoe in Israel, all birds responsible for the pollination of several plant species in this area are primarily insectivorous, sedentary, or migrating passerine birds, particularly and . They contribute, together with insects, to the pollination of , three species of with big flowers, , and some other plants. The lacertid lizard acts as a pollinating agent on several W Mediterranean islands, where it effectively pollinates , and presumably and . The flowers of some other plant species are visited by birds or by species in the Mediterranean area, where they could also contribute to their pollination.
PubMed: 38592907
DOI: 10.3390/plants13060895 -
PloS One 2024Pollination biology in the widespread species Impatiens capensis Meerb. has only been studied in America, specifically in zones of the U.S.A. and Canada. In this study,...
Pollination biology in the widespread species Impatiens capensis Meerb. has only been studied in America, specifically in zones of the U.S.A. and Canada. In this study, we investigated the pollination biology of I. capensis using an integrative identification approach using morphological and molecular tools in four populations of Northwest Poland. We also determined and compared the functional characteristics of the pollinators of the introduced species from the study sites and the native ones reported, for the latter collecting information from bibliographic sources. Visitors were identified using standard morphological keys, including identifying and classifying insect mouthparts. Molecular identification was carried out using mitochondrial DNA's cytochrome oxidase subunit I (COI). We morphologically identified 20 species of visitors constituted by 17 pollinators and three nectar robbers. DNA barcoding of 59 individuals proved the identification of 18 species (also 18 BINs). The frequency of pollinator species was primarily made up of representatives of both Hymenoptera (75%) and Diptera (21%). The morphological traits, such as the chewing and sucking mouthparts, small and big body height, and robber and pollinator behavior explained mainly the native and introduced visitors' arrangements that allow pollination success. However, to understand the process comprehensively, further investigation of other causalities in pollination success and understanding the diversity of pollinators in outer native ranges are necessary.
Topics: Pollination; Animals; Impatiens; Introduced Species; Diptera; Poland; DNA Barcoding, Taxonomic; Hymenoptera
PubMed: 38900825
DOI: 10.1371/journal.pone.0302283 -
Environmental Pollution (Barking, Essex... Jun 2024Soil heavy metal contamination is often an unintended byproduct of historic land-use. This contamination can negatively impact resident plants and their interactions...
Soil heavy metal contamination is often an unintended byproduct of historic land-use. This contamination can negatively impact resident plants and their interactions with other organisms. Plant fitness in contaminated landscapes depends not only on plant growth, but also on the maintenance of interactions with pollinators. Cadmium (Cd) is a heavy metal that is commonly found in agricultural, urban, and industrial ecosystems as a legacy of historic land-use. It is a prioritized pollutant in soils because of its wide distribution and strong biotoxicity. To understand how Cd influences plant growth and pollinator interactions, we grew sunflowers in media with three different Cd concentrations to represent the range of Cd contamination faced by sunflowers growing on land recovering from past land-use. We measured Cd contamination effects on sunflower morphology and pollinator foraging behavior, specifically the number of visits and visit duration. We then measured seed number and weight to determine if contamination directly or indirectly, as mediated by pollinators, altered plant fitness. Plant height was negatively correlated with Cd concentration, but contamination alone (in the absence of pollinators) did not affect sunflower reproduction. Bumble bees visited sunflowers grown in Exceeding Threshold Cd concentrations less often and for shorter time compared to visits to Below Threshold Cd sunflowers, but honey bees and sweat bees showed similar foraging behavior across Cd contamination treatment levels. Sunflower seed set was positively correlated with the total number of pollinator visits, and sunflowers grown in Exceeding Threshold Cd soil had marginally lower seed set compared to those grown in Below Threshold Cd soil. Our results suggest that at Exceeding Threshold Cd contamination levels plant-pollinator interactions are negatively affected with consequences for plant fitness.
PubMed: 38848955
DOI: 10.1016/j.envpol.2024.124316 -
Ecology and Evolution Apr 2024The Rich. (Orchidoideae) comprise a speciose genus of orchids primarily in the northern hemisphere, with up to 200 known species worldwide. Individual species are known... (Review)
Review
The Rich. (Orchidoideae) comprise a speciose genus of orchids primarily in the northern hemisphere, with up to 200 known species worldwide. Individual species are known to self-pollinate, but many rely on insect pollinators with characteristics such as floral color, timing of floral odor emissions, nectar rewards, and spur length associated with particular pollination syndromes. As with many orchids, some orchid-pollinator associations are likely highly co-evolved, but we also know that some spp. are the result of hybridization events, which implies a lack of pollinator fidelity in some cases. Some spp. occur in large numbers which, coupled with the numerous -pollinator systems, make them accessible as study species and useful for co-evolutionary studies. Due to the likely effects of climate change and ongoing development on spp. habitats, these orchids and their associated pollinators should be a focus of conservation attention and management. However, while there is a fairly substantial literature coverage of -pollinator occurrence and interactions, there are still wide gaps in our understanding of the species involved in these systems. In this systematic review, we outline what is current knowledge and provide guidance on further research that will increase our understanding of orchid-insect co-evolutionary relationships. Our review covers 157 orchid species and about 233 pollinator species interacting with 30 spp. We provide analyses on aspects of these interactions such as flower morphology, known insect partners of species, insect- specificity, pollination visitor timing (diurnal vs. nocturnal), floral rewards, and insect behavior affecting pollination outcomes (e.g., pollinia placement). A substantial number of spp. and at least a few of their known pollinators are of official (IUCN) conservation concern - and many of their pollinators remain unassessed or even currently unknown - which adds to the urgency of further research on these co-evolved relationships.
PubMed: 38606342
DOI: 10.1002/ece3.11223