13. Lichtenberg, EM; Kennedy, CM; Kremen, C; Batary, P; Berendse, F; Bommarco, R; Bosque-Perez, NA; Carvalheiro, LG; Snyder, WE; Williams, NM; Winfree, R; Klatt, BK; Astrom, S; Benjamin, F; Brittain, C; Chaplin-Kramer, R; Clough, Y; Danforth, B; Diekotter, T; Eigenbrode, SD; Ekroos, J; Elle, E; Freitas, BM; Fukuda, Y; Gaines-Day, HR; Grab, H; Gratton, C; Holzschuh, A; Isaacs, R; Isaia, M; Jha, S; Jonason, D; Jones, VP; Klein, AM; Krauss, J; Letourneau, DK; Macfadyen, S; Mallinger, RE; Martin, EA; Martinez, E; Memmott, J; Morandin, L; Neame, L; Otieno, M; Park, MG; Pfiffner, L; Pocock, MJO; Ponce, C; Potts, SG; Poveda, K; Ramos, M; Rosenheim, JA; Rundlof, M; Sardinas, H; Saunders, ME; Schon, NL; Sciligo, AR; Sidhu, CS; Steffan-Dewenter, I; Tscharntke, T; Vesely, M; Weisser, WW; Wilson, JK; Crowder, DW. (2017) A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes.Global Change Biology 23: 4946-4957 A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes
agricultural management schemes; arthropod diversity; biodiversity; evenness; functional groups; landscape complexity; meta-analysis; organic farming; plant diversity
Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in-field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in-field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes. DOI
12. Moeller, DA; Runquist, RDB; Moe, AM; Geber, MA; Goodwillie, C; Cheptou, PO; Eckert, CG; Elle, E; Johnston, MO; Kalisz, S; Ree, RH; Sargent, RD; Vallejo-Marin, M; Winn, AA. (2017) Global biogeography of mating system variation in seed plants.Ecology Letters 20: 375-384 Global biogeography of mating system variation in seed plants
Biotic interactions; breeding system; floral evolution; latitudinal gradient; life history; outcrossing; plant-pollinator interaction; pollination; self-fertilisation; sexual system
Latitudinal gradients in biotic interactions have been suggested as causes of global patterns of biodiversity and phenotypic variation. Plant biologists have long speculated that outcrossing mating systems are more common at low than high latitudes owing to a greater predictability of plant-pollinator interactions in the tropics; however, these ideas have not previously been tested. Here, we present the first global biogeographic analysis of plant mating systems based on 624 published studies from 492 taxa. We found a weak decline in outcrossing rate towards higher latitudes and among some biomes, but no biogeographic patterns in the frequency of self-incompatibility. Incorporating life history and growth form into biogeographic analyses reduced or eliminated the importance of latitude and biome in predicting outcrossing or self-incompatibility. Our results suggest that biogeographic patterns in mating system are more likely a reflection of the frequency of life forms across latitudes rather than the strength of plant-pollinator interactions. DOI
11. Gibbs, J; Elle, E; Bobiwash, K; Haapalainen, T; Isaacs, R. (2016) Contrasting Pollinators and Pollination in Native and Non-Native Regions of Highbush Blueberry Production.PLoS One 11 Contrasting Pollinators and Pollination in Native and Non-Native Regions of Highbush Blueberry Production
Highbush blueberry yields are dependent on pollination by bees, and introduction of managed honey bees is the primary strategy used for pollination of this crop. Complementary pollination services are also provided by wild bees, yet highbush blueberry is increasingly grown in regions outside its native range where wild bee communities may be less adapted to the crop and growers may still be testing appropriate honey bee stocking densities. To contrast crop pollination in native and non-native production regions, we sampled commercial 'Bluecrop' blueberry fields in British Columbia and Michigan with grower-selected honey bee stocking rates (0-39.5 hives per ha) to compare bee visitors to blueberry flowers, pollination and yield deficits, and how those vary with local-and landscape-scale factors. Observed and Chao-1 estimated species richness, as well as Shannon diversity of wild bees visiting blueberries were significantly higher in Michigan where the crop is within its native range. The regional bee communities were also significantly different, with Michigan farms having greater dissimilarity than British Columbia. Blueberry fields in British Columbia had fewer visits by honey bees than those in Michigan, irrespective of stocking rate, and they also had lower berry weights and a significant pollination deficit. In British Columbia, pollination service increased with abundance of wild bumble bees, whereas in Michigan the abundance of honey bees was the primary predictor of pollination. The proportion of seminatural habitat at local and landscape scales was positively correlated with wild bee abundance in both regions. Wild bee abundance declined significantly with distance from natural borders in Michigan, but not in British Columbia where large-bodied bumble bees dominated the wild bee community. Our results highlight the varying dependence of crop production on different types of bees and reveal that strategies for pollination improvement in the same crop can vary greatly across production regions. DOI
9. Kleijn, D; Winfree, R; Bartomeus, I; Carvalheiro, LG; Henry, M; Isaacs, R; Klein, AM; Kremen, C; M'Gonigle, LK; Rader, R; Ricketts, TH; Williams, NM; Adamson, NL; Ascher, JS; Baldi, A; Batary, P; Benjamin, F; Biesmeijer, JC; Blitzer, EJ; Bommarco, R; Brand, MR; Bretagnolle, V; Button, L; Cariveau, DP; Chifflet, R; Colville, JF; Danforth, BN; Elle, E; Garratt, MPD; Herzog, F; Holzschuh, A; Howlett, BG; Jauker, F; Jha, S; Knop, E; Krewenka, KM; Le Feon, V; Mandelik, Y; May, EA; Park, MG; Pisanty, G; Reemer, M; Riedinger, V; Rollin, O; Rundlof, M; Sardinas, HS; Scheper, J; Sciligo, AR; Smith, HG; Steffan-Dewenter, I; Thorp, R; Tscharntke, T; Verhulst, J; Viana, BF; Vaissiere, BE; Veldtman, R; Westphal, C; Potts, SG. (2015) Delivery of crop pollination services is an insufficient argument for wild pollinator conservation.Nature Communications 6 Delivery of crop pollination services is an insufficient argument for wild pollinator conservation
There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost- effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost- effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments. DOI
8. Wray, JC; Elle, E. (2015) Flowering phenology and nesting resources influence pollinator community composition in a fragmented ecosystem.Landscape Ecology 30: 261-272 Flowering phenology and nesting resources influence pollinator community composition in a fragmented ecosystem
Habitat fragmentation; Oak-savannah; Landscape matrix; Community composition; Flowering plants; Nesting resources
Habitat loss is the leading cause of extinctions on the planet. However, negative effects of habitat loss and fragmentation on biodiversity can be reduced if resources in urban or semi-natural areas in the surrounding matrix can be used by wildlife. We investigated the influence of floral and nesting resources in urban- and forest-associated oak-savannah fragments, surrounding urban and forest matrix, and urban areas spatially independent from oak-savannah habitat on pollinator community composition in a fragmented oak-savannah ecosystem. Both independent urban and urban matrix sites supported high abundance and richness of plants and pollinators relative to other fragment categories, especially towards the end of the season when plants and pollinators in oak-savannah fragments were scarce. A species of particular conservation concern in our region, Bombus occidentalis, was supported by late-flowering resources in our urban sites. Forest-associated oak-savannah fragments were missing late-season species while urban-associated fragments supported high abundance and richness of mid- to late-season pollinators, likely due to supplemental use of floral resources in the urban matrix. Female cavity-nesting and ground-nesting bees were not restricted by the availability of natural nesting resources we expected them to require (e.g. small cavities, bare soil). These results provide important information on native pollinators in a highly fragmented habitat, and suggest that we should consider matrix quality in conservation planning. DOI
7. Button, L; Elle, E. (2014) Wild bumble bees reduce pollination deficits in a crop mostly visited by managed honey bees.Agriculture Ecosystems & Environment 197: 255-263 Wild bumble bees reduce pollination deficits in a crop mostly visited by managed honey bees
Pollination deficit; Edge effect; Mixed pollinator strategy; Apis mellifera; Bombus; Blueberry
We assessed the pollinator community of two cultivars of highbush blueberry (Vaccinium corymbosum, Duke and Bluecrop), and determined the importance of different pollinators to overall crop yield by measuring pollination deficits. The importance of distance to putative wild pollinator habitat (natural field edges) for pollinator abundance within fields and crop yield was also considered. Managed honey bees made 70% of flower visits (85% to Duke, 49% to Bluecrop). Wild bumble bees made half of the visits to Bluecrop. Though bumble bees were observed less frequently as distance from the natural edge increased, there was no effect of distance on levels of crop pollination. Pollination deficits were less pronounced in Duke than Bluecrop, with maximum (hand) pollination leading to a 12% (Duke) to 23% (Bluecrop) increase in yield. Exclusion of pollinators reduced yield by 50-80% compared to ambient pollination. For both cultivars, pollination deficits declined most strongly with either increasing bumble bee visits or increasing total visits (honey bees and bumble bees combined), and in no case were deficit levels significantly reduced by honey bees alone. This study supports a growing body of literature that suggests managed honey bees alone cannot reduce deficits, and that wild pollinators are needed to maximize yields in pollinator-dependent agricultural systems. (C) 2014 Elsevier B.V. All rights reserved. DOI
6. Chamberlain, S; Vazquez, DP; Carvalheiro, L; Elle, E; Vamosi, JC. (2014) Phylogenetic tree shape and the structure of mutualistic networks.Journal of Ecology 102: 1234-1243 Phylogenetic tree shape and the structure of mutualistic networks
connectance; diversity; modularity; nestedness; network structure; phylogeny imbalance; plant population and community dynamics; plant-pollinator interactions
1. Species community composition is known to alter the network of interactions between two trophic levels, potentially affecting its functioning (e. g. plant pollination success) and the stability of communities. Phylogenies vary in shape with regard to the rate of evolutionary change across a tree (influencing tree balance) and variation in the timing of branching events (affecting the distribution of node ages in trees), both of which may influence the structure of species interaction networks. Because related species are likely to share many of the traits that regulate interactions, the shape of phylogenetic trees may provide some insights into the distribution of traits within communities, and hence the likelihood of interaction among species. However, little attention has been paid to the potential effects of changes in phylogenetic diversity (PD) on interaction networks. 2. Phylogenetic diversity is influenced by species diversity within a community, but also how distantly-related the constituent species are from one another. Here, we evaluate the relationship between two important measures of phylogenetic diversity (tree shape and age of nodes) and the structure of plant-pollinator interaction networks using empirical and simulated data. Whereas the former allows us to evaluate patterns in real communities, the latter allows us to evaluate more systematically the relationship between tree shape and network structure under three different models of trait evolution. 3. In empirical networks, less balanced plant phylogenies were associated with lower connectance in interaction networks indicating that communities with the descendants of recent radiations are more diverged and specialized in their partnerships. In simulations, tree balance and the distribution of nodes through time were included in the best models for modularity, and the second best models for connectance and nestedness. In models assuming random evolutionary change through time (i.e. Brownian motion), less balanced trees and trees with nodes near the tips exhibited greater modularity, whereas in models with an early burst of radiation followed by relative stasis (i.e. early-burst models) more balanced trees and trees with nodes near roots had greater modularity. 4. Synthesis. Overall, these results suggest that the shape of phylogenies can influence the structure of plant-pollinator interaction networks. However, the mismatch between simulations and empirical data indicate that no simple model of trait evolution mimics that observed in real communities. DOI
5. Chamberlain, SA; Cartar, RV; Worley, AC; Semmler, SJ; Gielens, G; Elwell, S; Evans, ME; Vamosi, JC; Elle, E. (2014) Traits and phylogenetic history contribute to network structure across Canadian plant-pollinator communities.Oecologia 176: 545-556 Traits and phylogenetic history contribute to network structure across Canadian plant-pollinator communities
Mutualism; Interaction webs; Trophic levels; Morphological trait; Functional trait
Interaction webs, or networks, define how the members of two or more trophic levels interact. However, the traits that mediate network structure have not been widely investigated. Generally, the mechanism that determines plant-pollinator partnerships is thought to involve the matching of a suite of species traits (such as abundance, phenology, morphology) between trophic levels. These traits are often unknown or hard to measure, but may reflect phylogenetic history. We asked whether morphological traits or phylogenetic history were more important in mediating network structure in mutualistic plant-pollinator interaction networks from Western Canada. At the plant species level, sexual system, growth form, and flower symmetry were the most important traits. For example species with radially symmetrical flowers had more connections within their modules (a subset of species that interact more among one another than outside of the module) than species with bilaterally symmetrical flowers. At the pollinator species level, social species had more connections within and among modules. In addition, larger pollinators tended to be more specialized. As traits mediate interactions and have a phylogenetic signal, we found that phylogenetically close species tend to interact with a similar set of species. At the network level, patterns were weak, but we found increasing functional trait and phylogenetic diversity of plants associated with increased weighted nestedness. These results provide evidence that both specific traits and phylogenetic history can contribute to the nature of mutualistic interactions within networks, but they explain less variation between networks. DOI PubMed
4. Kennedy, CM; Lonsdorf, E; Neel, MC; Williams, NM; Ricketts, TH; Winfree, R; Bommarco, R; Brittain, C; Burley, AL; Cariveau, D; Carvalheiro, LG; Chacoff, NP; Cunningham, SA; Danforth, BN; Dudenhoffer, JH; Elle, E; Gaines, HR; Garibaldi, LA; Gratton, C; Holzschuh, A; Isaacs, R; Javorek, SK; Jha, S; Klein, AM; Krewenka, K; Mandelik, Y; Mayfield, MM; Morandin, L; Neame, LA; Otieno, M; Park, M; Potts, SG; Rundlof, M; Saez, A; Steffan-Dewenter, I; Taki, H; Viana, BF; Westphal, C; Wilson, JK; Greenleaf, SS; Kremen, C. (2013) A global quantitative synthesis of local and landscape effects on wild bee pollinators in agroecosystems.Ecology Letters 16: 584-599 A global quantitative synthesis of local and landscape effects on wild bee pollinators in agroecosystems
DIFFERENT SPATIAL SCALES; AGRICULTURAL LANDSCAPES; CROP POLLINATION; ECOSYSTEM SERVICES; SPECIES RICHNESS; NATIVE BEES; BIODIVERSITY; INTENSIFICATION; CONTEXT; METAANALYSIS
Bees provide essential pollination services that are potentially affected both by local farm management and the surrounding landscape. To better understand these different factors, we modelled the relative effects of landscape composition (nesting and floral resources within foraging distances), landscape configuration (patch shape, interpatch connectivity and habitat aggregation) and farm management (organic vs. conventional and local-scale field diversity), and their interactions, on wild bee abundance and richness for 39 crop systems globally. Bee abundance and richness were higher in diversified and organic fields and in landscapes comprising more high-quality habitats; bee richness on conventional fields with low diversity benefited most from high-quality surrounding land cover. Landscape configuration effects were weak. Bee responses varied slightly by biome. Our synthesis reveals that pollinator persistence will depend on both the maintenance of high-quality habitats around farms and on local management practices that may offset impacts of intensive monoculture agriculture. DOI
3. Winn, AA; Elle, E; Kalisz, S; Cheptou, PO; Eckert, CG; Goodwillie, C; Johnston, MO; Moeller, DA; Ree, RH; Sargent, RD; Vallejo-Marin, M. (2011) ANALYSIS OF INBREEDING DEPRESSION IN MIXED-MATING PLANTS PROVIDES EVIDENCE FOR SELECTIVE INTERFERENCE AND STABLE MIXED MATING.Evolution 65: 3339-3359 ANALYSIS OF INBREEDING DEPRESSION IN MIXED-MATING PLANTS PROVIDES EVIDENCE FOR SELECTIVE INTERFERENCE AND STABLE MIXED MATING
Age-specific expression of inbreeding depression; gynodioecy; mating-system evolution; outcrossing; purging; selfing
Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of selfing, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r > 0.8), mixed-mating (0.2 =r= 0.8), and highly outcrossing (r < 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (d= 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them. DOI
2. Eckert, CG; Kalisz, S; Geber, MA; Sargent, R; Elle, E; Cheptou, PO; Goodwillie, C; Johnston, MO; Kelly, JK; Moeller, DA; Porcher, E; Ree, RH; Vallejo-Marin, M; Winn, AA. (2010) Plant mating systems in a changing world.Trends in Ecology & Evolution 25: 35-43 Plant mating systems in a changing world
There is increasing evidence that human disturbance can negatively impact plant-pollinator interactions such as outcross pollination. We present a meta-analysis of 22 studies involving 27 plant species showing a significant reduction in the proportion of seeds outcrossed in response to anthropogenic habitat modifications. We discuss the evolutionary consequences of disturbance on plant mating systems, and in particular whether reproductive assurance through selfing effectively compensates for reduced outcrossing. The extent to which disturbance reduces pollinator versus mate availability could generate diverse selective forces on reproductive traits. Investigating how anthropogenic change influences plant mating will lead to new opportunities for better understanding of how mating systems evolve, as well as of the ecological and evolutionary consequences of human activities and how to mitigate them. DOI
1. Goodwillie, C; Sargent, RD; Eckert, CG; Elle, E; Geber, MA; Johnston, MO; Kalisz, S; Moeller, DA; Ree, RH; Vallejo-Marin, M; Winn, AA. (2010) Correlated evolution of mating system and floral display traits in flowering plants and its implications for the distribution of mating system variation.New Phytologist 185: 311-321 Correlated evolution of mating system and floral display traits in flowering plants and its implications for the distribution of mating system variation
LEPTOSIPHON-JEPSONII POLEMONIACEAE; NUMBER TRADE-OFF; SELF-FERTILIZATION; INBREEDING DEPRESSION; RESOURCE-ALLOCATION; FEMALE FUNCTIONS; POLLINATOR VISITATION; PHYLOGENETIC EVIDENCE; FITNESS CONSEQUENCES; INFLORESCENCE SIZE
P> Reduced allocation to structures for pollinator attraction is predicted in selfing species. We explored the association between outcrossing and floral display in a broad sample of angiosperms. We used the demonstrated relationship to test for bias against selfing species in the outcrossing rate distribution, the shape of which has relevance for the stability of mixed mating. Relationships between outcrossing rate, flower size, flower number and floral display, measured as the product of flower size and number, were examined using phylogenetically independent contrasts. The distribution of floral displays among species in the outcrossing rate database was compared with that of a random sample of the same flora. The outcrossing rate was positively associated with the product of flower size and number; individually, components of display were less strongly related to outcrossing. Compared with a random sample, species in the outcrossing rate database showed a deficit of small floral display sizes. We found broad support for reduced allocation to attraction in selfing species. We suggest that covariation between mating systems and total allocation to attraction can explain the deviation from expected trade-offs between flower size and number. Our results suggest a bias against estimating outcrossing rates in the lower half of the distribution, but not specifically against highly selfing species. DOI
