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19 results for “flower density”
Fig. 2 in Examining the relationship between flower thrips (Thysanoptera: Thripidae) spatial distribution and blueberry (Ericales: Ericaceae) flower density
Fig. 2. Graph of percentage of open blueberry flowers vs. log10 thrips per trap from the Windsor farm on 18 Mar 2010. The black line represents a regression line fitted by least squares regression.
Fig. 1 in Examining the relationship between flower thrips (Thysanoptera: Thripidae) spatial distribution and blueberry (Ericales: Ericaceae) flower density
Fig. 1. Graphs showing percentage of open blueberry flowers vs. thrips per trap from the Inverness farm on a) 30 Jan and b) 5 Feb 2009. The black lines represent regression lines fitted by Theil regression.
Data from: Fine-scale genetic structure in the orchid Gymnadenia conopsea is not associated with local density of flowering plants
<p><span><strong>Premise</strong>:</span><span> Density-dependent pollinator visitation can lead to density-dependent mating patterns and within-population genetic structure. In Gymnadenia conopsea, individuals in low-density patches receive more self-pollen than individuals in high-density patches, suggesting higher relatedness at low density. Ongoing fragmentation is also expected to cause more local matings, potentially leading to biparental inbreeding depression.</span></p> <p><span><strong>Methods</strong>: </span><span>To evaluate whether relatedness decreases with local density, we analysed 1315 SNP loci in 113 individuals within two large populations. We quantified within-population genetic structure in one of the populations, recorded potential habitat barriers, and visualized gene flow using estimated effective migration surfaces (EEMS). We further estimated the magnitude of biparental inbreeding depression that would result from matings restricted to within 5 m.</span></p> <p><span><strong>Results</strong>: </span><span>There was no significant relationship between local density and relatedness in any population. We detected significant fine-scale genetic structure consistent with isolation-by-distance, with positive kinship coefficients at distances below 10 m. Kinship coefficients were low, and predicted biparental inbreeding depression resulting from matings within the closest 5 m was a modest 1–3%.</span> <span>EEMS suggested that rocks and bushes may act as barriers to gene flow within a population.</span></p> <p><span><strong>Conclusions</strong>: </span><span>The results suggest that increased self-pollen deposition in sparse patches does not necessarily cause higher selfing rates, or that inbreeding depression results in low establishment success of inbred individuals. The modest relatedness suggests that biparental inbreeding depression is unlikely to be an immediate problem following fragmentation of large populations. The results further indicate that habitat structure may contribute to governing fine-scale genetic structure in <em>G. conopsea</em>.</span></p>
Impacts of flowering density on pollen dispersal and gametic diversity are scale dependent
<p>Pollen dispersal is a key evolutionary and ecological process, but the degree to which variation in the density of concurrently flowering conspecific plants (i.e., co-flowering density) shapes pollination patterns remains understudied. We monitored co-flowering density and corresponding pollination patterns of the insect-pollinated palm <em>Oenocarpus bataua</em> in northwestern Ecuador and found that the influence of co-flowering density on these patterns was scale-dependent: high neighborhood densities were associated with reductions in pollen dispersal distance and gametic diversity of progeny arrays, whereas we observed the opposite pattern at the landscape scale. In addition, neighborhood co-flowering density also impacted forward pollen dispersal kernel parameters, suggesting that low neighborhood densities encourage pollen movement and may promote gene flow and genetic diversity. Our work reveals how co-flowering density at different spatial scales influences pollen movement, which in turn informs our broader understanding of the mechanisms underlying patterns of genetic diversity and gene flow within populations of plants.</p>
Patterns of frequency and density dependence are highly variable in diverse annual flowering plant communities
<p>Applications of ecological theory to natural communities often assume that competitive, negative density-dependent processes are the only type of interaction important for diversity maintenance. Recent advances suggest that positive interactions within trophic levels (e.g. plant-plant) may also affect plant coexistence. Though positive plant-plant interactions theoretically might result in positive or nonmonotonic frequency or density dependence (FD/DD), less is known about how commonly these patterns occur, or which ecological processes might result in such patterns in natural plant communities. In this study, we test for signals of variable frequency and density dependence in annual flowering plant communities in Western Australia and search for evidence that interactions among plants during flowering might induce positive or nonmonotonic FD/DD in flowering plants. Using four common annual wildflower species, we ask if plant fecundity exhibits positive or nonmonotonic FD/DD and if pollinator-mediated plant-plant interactions during flowering change patterns of FD/DD relative to pollinator-independent plant interactions. Three species exhibited nonmonotonic (hump-shaped) density dependence, and only one species experienced strictly negative density dependence. Each species exhibited a different pattern of frequency dependence (positive, negative, weakly nonmonotonic, and no detectable frequency dependence). Pollinator-mediated plant-plant interactions during flowering induced both nonmonotonic density dependence and negative frequency dependence in one species. Importantly, the extent of variation in FD/DD observed in our study brings into question the dominance of negative density and frequency dependence in theory, suggesting instead that demographic responses of plants to their communities fall along a continuum of possible density- and frequency-dependent patterns.</p>
Patterns of frequency and density dependence are highly variable in diverse annual flowering plant communities
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Data from: Fine-scale genetic structure in the orchid Gymnadenia conopsea is not associated with local density of flowering plants
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Impacts of flowering density on pollen dispersal and gametic diversity are scale dependent
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Data from: Scale-dependent shifts in the species composition of flower visitors with changing floral density
Responses of flower-visiting animals to floral density can alter interactions between plants, influencing a variety of biological processes, including plant population dynamics and the evolution of flowering phenology. Many studies have found effects of floral or plant density on pollinator visitation rates at patch scales, but little is known about responses of flower visitors to floral densities at larger scales. Here, I present data from an observational field study in which I measured the effects of floral density on visitation to the annual composite Holocarpha virgata at both patch (4 m(2)) and site (12.6 ha) spatial scales. The species composition of flower visitors changed with floral density, and did so in different ways at the two scales. At the site scale, average floral density within patches of H. virgata or within patches of all summer-flowering species combined had a significant positive effect on per-flowerhead visitation by the long-horned bee Melissodes lupina and no significant effects on visitation by any other taxa. At the patch scale, per-flowerhead visitation by honeybees significantly increased whereas visitation by M. lupina often decreased with increasing floral density. For both species, responses to patch-scale floral density were strongest when site-scale floral density was high. The scale-dependence of flower visitor responses to floral density and the interactions between site- and patch-scale effects of floral density observed in this study underscore the importance of improving our understanding of pollinators' responses to floral density at population scales.
Data from: Experimental small-scale flower patches increase species density but not abundance of small urban bees
1. Large flower plantings are often used to combat negative effects of habitat loss on pollinators, but whether these floral additions are effective at smaller scales remains unclear, particularly in urban settings. 2. To test the effectiveness of small-scale floral additions on enhancing urban bee populations, as well as their impact from one year to the next, different quantities of potted sweet alyssum (Lobularia maritima) flowers were placed across sites in Ann Arbor, Michigan for two consecutive years and the resulting Halictid bee visitors were monitored. 3. Overall we found the number of flowers added at the local level was significantly and positively correlated with small Halictid bee abundance and species density in an urban landscape. At smaller flower quantities dynamics were clearly linear, where incremental increases in number of flowers showed significant increases in bee abundance and species density. At larger quantities of floral additions, however, dynamics were nonlinear in that incremental increases in flower quantity had no effect on bee abundance and highly variable effects on bee species density. 4. When comparing the change in small Halictid bee abundance and species density from one year to the next, we found a significant increase in bee species density in the second year of small-scale floral additions, but no significant difference in bee abundance. 5. Synthesis and applications. Our results show that small flower plantings can have positive effects on small bee communities in urban systems even over a short period of time, and therefore confirm that encouraging citizens to plant flowers can be an effective conservation strategy for certain urban pollinator populations. In addition, our finding that smaller flower plantings may have higher impacts on small pollinators than larger plantings suggests resource managers interested in pollinator conservation should consider spreading multiple, smaller floral plantings across the urban landscape, rather than pooling all resources into one large flower patch.29-Nov-2017
Data from: Experimental evidence that honeybees depress wild insect densities in a flowering crop
While addition of managed honeybees (Apis mellifera) improves pollination of many entomophilous crops, it is unknown if it simultaneously suppresses the densities of wild insects through competition. To investigate this, we added 624 honeybee hives to 23 fields of oilseed rape (Brassica napus L.) over 2 years and made sure that the areas around 21 other fields were free from honeybee hives. We demonstrate that honeybee addition depresses the densities of wild insects (bumblebees, solitary bees, hoverflies, marchflies, other flies, and other flying and flower-visiting insects) even in a massive flower resource such as oilseed rape. The effect was independent of the complexity of the surrounding landscape, but increased with the size of the crop field, which suggests that the effect was caused by spatial displacement of wild insects. Our results have potential implications both for the pollination of crops (if displacement of wild pollinators offsets benefits achieved by adding honeybees) and for conservation of wild insects (if displacement results in negative fitness consequences).
FIG. 1 in Foraging by the flower-dwelling spider, Misumenops argenteus (Thomisidae), at high prey density sites
FIG. 1. Manly's index of habitat preference for (A) M. argenteus and of (B) potential prey for each phase of T. adenantha flowerheads (F1 to F5, see Methods) along the Mirante track, during the rainy season. Values above and below 0.20 (1/total number of flowerhead phases) indicate a preference for and avoidance of flowerhead types by the spiders, respectively. The distribution of the spiders in the dry season was not assessed because of the low number of animals encountered. In the dry season the prey and adult females were not considered because their distribution among the different flowerheads was not significant (see Results).
Influence of local density and sex ratio on pollination in an ambophilous flowering plant
<p class="MSbody"><span><b>PREMISE OF THE STUDY:</b> Variation in local density and sex ratio in dioecious plants can affect mating success through the actions of pollen vectors, principally generalist insects or wind. Increased density and male-biased sex ratios should promote pollen transfer and seed production, but their combined effects have not been investigated for ambophilous species, which exhibit both insect and wind pollination. </span></p> <p class="MSbody"><span><b>METHODS: </b>We manipulated density (low vs. high) and sex ratio (1:1 vs. 3:1 male-biased) in arrays of dioecious ambophilous <i>Thalictrum pubescens</i>. We quantified visitation rates and foraging time to examine whether pollinators exhibited sex-specific preferences and determined the seed set of arrays.<b> </b></span></p> <p class="MSbody"><b>KEY RESULTS:</b> Pollinators visited more plants per foraging bout at high than low density. Visitation rates and foraging times of visitors were greater for male than female plants but did not depend on the density or sex ratio of arrays. However, whereas solitary bees displayed a strong preference for males, hover flies were indifferent to plant sex phenotype. Solitary bees also visited significantly more plants per foraging bout than hover flies. There was a significant interaction between density and sex ratio on seed set. At low density, seed set was greater for 1:1 than 3:1 arrays, but at high density the opposite pattern occurred. </p> <p class="MSbody"><b>CONCLUSIONS: </b>The demographic factors we investigated had complex influences on pollinator foraging behavior and patterns of seed set. Several factors may explain our results including the influence of density and sex ratio on pollen export from arrays, grooming by pollinators and the contribution of wind pollination.</p>
Data from: Scale-dependent shifts in the species composition of flower visitors with changing floral density
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Data from: Experimental small-scale flower patches increase species density but not abundance of small urban bees
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Influence of local density and sex ratio on pollination in an ambophilous flowering plant
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Data from: Experimental evidence that honeybees depress wild insect densities in a flowering crop
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Spartina patens surveys of flowering density at marsh-forest ecotone
<p>Climate change is driving abiotic shifts that can threaten the conservation of foundation species and the habitats they support. Range shifts are one mechanism of escape, but this requires successful colonization of habitats where interspecific interactions may differ from those to which a species has adapted. For plants with multiple reproductive strategies, these range-edge interactions may alter the investment or allocation towards a given reproductive strategy. In this study, we quantify sexual reproduction of the clonal marsh grass <em>Spartina patens </em>across an inland colonization front into maritime forest being driven by sea-level rise. We find that flowering is variable across <em>S. patens </em>meadows, but consistently reduced under low light conditions like those of the forest understory. Observational surveys of <em>S. patens</em> flowering at four sites in the Delmarva Peninsula agreed with the results of two experimental manipulations of light availability (shading experiment in <em>S. patens</em>-dominated marsh and a forest dieback manipulation). These three approaches pinpointed light limitation as a principal control on <em>S. patens</em> flowering capacity, suggesting that light competition with taller upland species can suppress <em>S. patens</em> flowering along its upland migration front. Consequently, all propagation in shaded conditions must occur clonally or via seeds from the marsh, a reproductive restriction that could limit the potential for local adaptation and reduce genetic diversity. Future research is needed to determine if the lack of flowering is the result of a tradeoff between sexual and clonal reproduction or if it results from insufficient photosynthetic products needed to achieve either reproductive method.</p>
Spartina patens surveys of flowering density at marsh-forest ecotone
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Allen Brain Atlas
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International Brain Laboratory public data
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OpenNeuro
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