Entomophilous Plant Species Research Articles

Cross-taxon analysis in the highly threatened Mediterranean dunes reveals consistent diversity patterns in butterfly and plant communities

AbstractButterflies and plant species are widely used as model systems in biodiversity and conservation research. However, little is known about spatial patterns of butterfly diversity linked to plant communities across coastal dune ecotones. We explored the relation between butterfly and vegetation diversity in a Mediterranean protected dune system in Central Italy. We sampled butterfly and plant communities on shifting and fixed dunes and investigated their distribution patterns by diversity indexes and Species Abundance Diversity models (SADs). We also computed species beta-diversity and analyzed the relation between butterfly communities and vegetation by correlation analyses. Cross-taxon congruence in species richness, composition and abundance was assessed using Mantel correlation tests. Both butterfly and plant diversity were higher on the fixed dunes than on the shifting dunes. In both communities, SADs were adequately described by the geometric series model, which is typical of harsh environments with simple communities dominated by few species. Among both butterflies and plants, we identified species found only on either the shifting or the fixed dunes. Correlation between plant and butterfly diversity was higher for entomophilous plant species than for the more abundant anemophilous ones. Our results indicate that both plant and butterfly communities respond to the sea-inland environmental gradient, forming distinct communities with specialized taxa. Our findings also provide evidence of the importance of butterfly-plant relations for preserving biological diversity and ecosystem functioning in Mediterranean coastal areas.

Searching to improve connectivity in fragmented landscapes: Road verges as complementary habitats

AbstractAimsFunctional connectivity is crucial for conserving biodiversity and ecosystem services in fragmented landscapes. Linear landscape elements play an important role in providing refuge for plants and pollinators, as well as serving as biological corridors. The aim of this study was to assess the importance of road verges in maintaining the ecological connectivity of plant species assemblages in the Tandilia mountain system.LocationSouth America, Southern Pampa region of Argentina, Tandilia mountain system.MethodsUsing graph theory, landscape connectivity was quantified both at landscape scale and at the patch scale using the probability connectivity index (PCnum), taking into account the dispersal ability of observed species. The contribution of each landscape element to habitat availability and connectivity was evaluated using different fractions of the PCnum metric. Likewise, the influence of connectivity variables in explaining species assemblages grouped by functional categories was investigated using canonical ordination techniques.ResultsThe inclusion of road verges led to an 81% increase in overall connectivity at a threshold distance of 500 m. Connectivity significantly explained the assemblages of entomophilous plant species for all dispersal distances. Annual species assemblage variation was associated with intra‐patch connectivity. Variation in perennial and shrub species assemblages was explained by intra‐patch and inter‐patch connectivity.ConclusionsPreservation and restoration of these linear landscape elements play a pivotal role in transitioning toward more sustainable agroecosystems. This ecological and practical information may help prioritize plant species and the sites used to restore an essential but neglected ecosystem.

Differential ecomorphic analysis of urban park vegetation

The ecomorphic approach was developed to analyze the structure of natural plant communities. This method was applied to analyze the ecological structure of an artificial park plantation in an urban environment. Urban parks perform important and diverse functions in the urban environment. As anthropogenic objects, urban parks should be subject to adequate and effective management that can increase the functional value of forest plantations in the city and ensure their sustainability. In this regard, the choice of the quantitative parameters of the park plantation to be managed is crucial. We hypothesize that ecomorphic analysis can be the basis for selecting optimal quantitative criteria for parkland management. Therefore, the goal of our study was to assess the informational value of ecomorphic analysis for characterizing park plantation in urban environments. In the park, 166 species of vascular plants were found, which are represented by phanerophytes (19.9%), nannophanerophytes (8.4%), hemicryptophytes (40.4%), geophytes (11.4%), theorophytes (18.7%) and geolophytes (1.2%). Sylvants (35.5%) predominate among the coenomorphs, with slightly less pratants (22.3%), ruderants (18.7%) and stepants (14.5%). Cultivants (3.0%), psammophytes (3.0%) and paludants (3.0%) were occasionally found. The proportion of xeromesophytes and mesophytes was the highest (32.5 and 31.3% respectively). The proportion of mesoxerophytes was also relatively high (28.3%). The proportion of other hygromorphs was relatively low. The trophomorphs were represented mainly by mesotrophs (71.1%) and a slightly smaller proportion of megatrophs (22.3%). The oligotrophs were found occasionally (6.6%). Sciogeophytes (57.2%) and heliophytes (30.1%) prevailed among heliomorphs. The proportion of sciophytes and heliosciophytes was much lower (3.6 and 9.0 %, respectively). Entomophilous plant species were the most common among the vegetation cover of the park (71.7%). Anemophilous plants were significantly inferior to them (26.5%). Autogamous and hydrophilous plants were found occasionally (1.2 and 0.6% respectively). Ballistic diasporeochores prevailed among diasporeochores (39.8%). The proportion of anemochores and endozoochores was somewhat lower (27.7 and 12.0% respectively). The results obtained allow to discover the essential ecological features of the park plantation. The park plantation has many features that bring it closer to natural forests. The similarity consists in a significant proportion of silvants, shade-loving species, and mesotrophs. A significant level of anthropogenic impact can be diagnosed on the basis of information about the increased proportion of ruderants in the plant community. The differential analysis of the ecomorphic structure in the section by climorphs is of considerable value. This approach allowed to detect an increased role of the zoogenic factor in the distribution of diaspores of phanerophytes and nannophanerophytes and an increased role of wind in the dispersal of geophytes and therophytes. The role of wind is reduced in the dispersion of hemicryptophytes in the urban environment.

Few plants and one dominant fly shape a unique pollination network in a Neotropical mangrove

Mangroves are unique ecosystems supported by very small plant assemblages. Those few plants tend to be insect-pollinated and make generalized interactions, which leads to competition for pollinators. Mangroves are poorly studied in terms of pollination ecology, and we still do not know how those interactions scale up to form networks. We described the pollination network of a Neotropical mangrove to understand how plant species share pollinators and to gain insight into network assembly in a species-poor ecosystem. We assessed year-round pollination interactions in a mangrove in north-eastern Brazil comprising three entomophilous plant species and described the topology of the resulting network in terms of nestedness, specialization, and modularity. We also assessed the relative importance and niche breadth of different pollinator groups using centrality metrics. The network had highly imbalanced node classes, comprising three zoophilous plant species and 29 insect species from the orders Diptera, Hymenoptera, and Lepidoptera. Pollinator species were mostly peripheral and rarely interacted with all plants, while plant species formed a generalized core. A single dominant fly species, Palpada albifrons, visited all plants and made most interactions, softening the separation between modules. The network was nonetheless moderately specialized due to several exclusive interactions with a taxonomic signal. These taxon-specific interaction patterns point to idiosyncrasies in mangrove pollination systems instead of the expected generalized interactions with non-selective insects. However, the mangrove’s reproductive dynamics seems to be dominated by a single pollinator species, and its network topology is heavily influenced by the low plant richness resultant from strong environmental filters.

¿Las plantas exóticas leñosas dependen de los polinizadores para reproducirse? Un estudio de caso en las Sierras de la Ventana (Argentina)

Most of the flowering plants depend on pollinators, in different degrees, for their reproduction. The degree of pollinator dependence is especially important in exotic plants because it could determine their colonization success in new locations. The objective of this study was to determine the degree of pollinator dependence in five exotic entomophilous plant species in a Pampean grassland located in Sierra de Ventana. It was determined if the differences in dependency are related to the geographic location and the phylogeny of plant species. The plants species were Spartium junceum, Genista monspessulana, Prunus mahaleb, Rosa rubiginosa and Rubus ulmifolius. Sampling was carried out in the Ernesto Tornquist Provincial Park and in surrounding areas (Buenos Aires Province). During the flowering peak of each species and in different sites, two treatments were undertaken in pre-bagged flowers: self-pollination and cross-pollination. Also, others pre-bagged flowers were left without pollination as control. Later, the probability of fruit develop and seed set under the two treatments and the control were assessed. Finally, the results of this study were compared with studies carried out in other regions (except for R. ulmifolius). The studied plant species showed a varied response to pollinator dependence, from very dependent species, such as S. junceum, G. monspessulana and P. mahaleb, to low dependent species such as R. rubiginosa y R. ulmifolius. Our results indicate that pollinator dependence can be variable in plants species that are colonizing non-native habitats. Furthermore, there are variations in the degree of pollinator dependency according to the geographical area, except for R. rubiginosa, showing that the geographical location can influence the dependence on pollinators for woody plants.

Sowing of margin strips rich in floral resources improves herbivore control in adjacent crop fields

Field margin vegetation provides resources for natural enemies of crop herbivores. Thus, the design of plant mixtures improving resource provisioning is being discussed increasingly with respect to improving herbivore control. We set up a field experiment to assess the effect of (i) a wildflower strip optimized for nectar provisioning; (ii) a grass strip and (iii) spontaneous vegetation on herbivore regulation in oilseed rape and wheat. We also analyzed the attractiveness of plant species to natural enemies. The cover of flowering entomophilous plant species as a proxy of floral resource provisioning was twice as high in wildflower strips compared with the other strip treatments. Natural enemy densities were higher within and close to wildflower strips in the field. A corresponding effect on aphid predation and aphid infestation was observed. Significant negative correlations between natural enemy abundance in the margin and aphid infestation in the fields supported a causal relationship. The sown wildflower strip species were more attractive to natural enemies than spontaneous vegetation. The results of the present study demonstrate that improved nectar provisioning increased the predation and parasitism of crop herbivores. Further research on the spatio‐temporal dynamics of interactions is needed to determine why not all crop herbivores respond to an increase of natural enemies in field margins.

Floral resource partitioning by individuals within generalised hoverfly pollination networks revealed by DNA metabarcoding

Pollination is a key ecosystem service for agriculture and wider ecosystem function. However, most pollination studies focus on Hymenoptera, with hoverflies (Syrphidae) frequently treated as a single functional group. We tested this assumption by investigating pollen carried by eleven species of hoverfly in five genera, Cheilosia, Eristalis, Rhingia, Sericomyia and Volucella, using DNA metabarcoding. Hoverflies carried pollen from 59 plant taxa, suggesting they visit a wider number of plant species than previously appreciated. Most pollen recorded came from plant taxa frequently found at our study sites, predominantly Apiaceae, Cardueae, Calluna vulgaris, Rubus fruticosus agg., and Succisa pratensis, with hoverflies transporting pollen from 40% of entomophilous plant species present. Overall pollen transport network structures were generalised, similar to other pollination networks elsewhere. All hoverfly species were also generalised with few exclusive plant/hoverfly interactions. However, using the Jaccard Index, we found significant differences in the relative composition of pollen loads between hoverfly genera, except for Volucella, demonstrating some degree of functional complementarity. Eristalis and Sericomyia species had significant differences in relative pollen load composition compared to congeners. Our results demonstrate the range of pollens transported by hoverflies and the potential pollination function undertaken within this ecologically and morphologically diverse guild.

Effects of spontaneous field margin vegetation on the regulation of herbivores in two winter crops

Non-crop vegetation of field margins provides resources for natural enemies of crop herbivores. However, it is still not well known whether this resource provisioning effect is strong enough to improve herbivore regulation within crop fields and which plant species and functional groups favour this ecosystem service. A better understanding of the interactions between field margin vegetation and herbivore regulation is crucial to evaluate management strategies and to design suppressive plant mixtures. We surveyed 64 wheat and oilseed rape fields of Western France for two years (16 fields per year and crop) in order (1) to identify plant diversity or group effects on herbivore regulation within crop fields and (2) to identify species within plant groups that improve regulation. Herbivores, herbivore damage and natural enemies were monitored on crop plants at a distance of 5 and 50m from the field margin. At the same time, the cover and phenological stage of all vascular plants were estimated in the adjacent field margin. The study demonstrated a positive relationship between the cover of entomophilous plant species that were flowering at the survey date and response variables related to herbivore regulation. Plant species richness and the cover of plant species taxonomically close to crop plants had a small influence on herbivores and natural enemies in wheat whereas related wild Brassicaceae increased herbivory and decreased herbivore regulation in oilseed rape. Within the entomophilous flowering plants, several species were significantly related to a better herbivore regulation in univariate analyses. Multivariate ordination techniques allowed the identification of plant species influencing several response variables of herbivore regulation at the same time. Our study demonstrated the importance of entomophilous species that flowered at peak infestation of crop herbivores. Spontaneous field margins rich in flowering entomophilous species provide an important ecosystem service without expensive sowing of seed mixtures.

New insights into plants co‐existence in species‐rich communities: The pollination interaction perspective

AbstractQuestionsIn animal‐mediated pollination, pollinators can be regarded as a limiting resource for which entomophilous plant species might interact to assure pollination, an event pivotal for their reproduction and population maintenance. At community level, spatially aggregated co‐flowering species can thus be expected to exhibit suitable suites of traits to avoid competition and ensure pollination. We explored the problem by answering the following questions: (1) are co‐flowering species specialized on different guilds of pollinators; (2) do co‐flowering pollinator‐sharing species segregate spatially; and (3) do co‐flowering pollinator‐sharing species that diverge in anther position spatially aggregate more than those that converge in anther position?Study SiteEuganean Hills,NEItaly.MethodsPlant composition, flowering phenology and interactions between each entomophilous plant species and pollinating insects were monitored every 15 days in 40 permanent plots placed in an area of 16 ha. We quantified the degree of flowering synchrony, pollinator‐sharing and spatial aggregation between each pair of entomophilous species. We then tested the relationship between the degree of co‐flowering, pollinator‐sharing and spatial aggregation, and between spatial aggregation and anther position.ResultsEntomophilous species converged, at least partially in flowering time, and the phenological synchronization of flowering was significantly associated with the sharing of pollinator guilds. Co‐flowering pollinator‐sharing species segregated spatially. Furthermore, co‐flowering pollinator‐sharing species that diverged in anther position aggregated more than those that converged in anther position.ConclusionsReproductive traits that facilitate the co‐existence of co‐flowering species include specialization on different pollinator guilds and a phenological displacement of the flowering time. Furthermore, in circumstances of increased competition due to phenological synchronization, pollinator‐sharing and spatial aggregation, the chance of effective pollination might depend on differences in anther position, resulting in a divergent pollen placement on pollinator bodies. One of the most interesting results we obtained is that the presence of one mechanism does not preclude the operation of others, and each plant species can simultaneously exhibit different strategies. Although more studies are needed, our results can provide additional information about plant–plant interactions and provide new insights into mechanisms allowing the co‐existence of a high number of plant species in local communities.

Grassland connectivity explains entomophilous plant species assemblages in an agricultural landscape of the Pampa Region, Argentina

AbstractThe Pampa grassland of Argentina is one of the most highly threatened biomes in the world. A high proportion of the original grassland cover has been transformed into land for agriculture or degraded. In the southern part of the region, fragmented semi‐natural grasslands over exposed rock still persist and connectivity between them is assumed to be crucial for maintaining viable populations. We quantified overall connectivity of grassland patches in a sector of the Southern Pampa region, and investigated the degree to which landscape connectivity explains entomophilous plant species assemblages in a subset of patches. We characterized each of the 301 patches in the landscape by their degree of intra‐patch and inter‐patch connectivity based on graph theory, and considering threshold dispersal distances from 100 to 1000 m. We surveyed entomophilous plant species in 39 grassland patches and classified the species in three categories (annual herbs, perennial herbs and shrubs) considering their different growth form and longevity. The influence of connectivity variables on entomophilous plant species assemblages variation was explored using Canonical Correspondence Analysis. Although grassland patches were poorly connected at all threshold distances, some of them were found to be critical for global connectivity. Connectivity significantly explained total, annual‐biennial and shrub assemblages for all threshold dispersal distances (6–13% of total variation). Variation in annual species assemblages was associated with intra‐patch and inter‐patch connectivity at short distance (100 m), while variation in shrub species assemblages was explained by intra‐patch and inter‐patch connectivity for distances between 100 m and 1000 m. This study evidenced the low connectivity of the study system, allowed the identification of critical areas for conservation, and provided valuable information to develop management strategies in increasingly human‐dominated landscapes.

Community structure and diversity of vegetation and flower-visiting wild bees (Hymenoptera: Apoidea) in sandy dry grassland: are there congruent characteristics?

We studied community structures of mainly threatened types of sandy dry grassland, and those of flower-visiting wild bees, in successional, non-ruderal or ruderal gradients in the Upper Rhine Valley (Germany). We searched for congruent characteristics in the floristic/faunistic structure of plant and bee species, and for differences between two study years. We also asked which vegetation type or complex plays the most important role as a pollen or nectar resource for wild bees, and what conclusions can be drawn for nature conservation. The vegetation types or complexes range from basiphytic pioneer stages to consolidated basiphytic to slightly acidophytic grasslands (classes Koelerio-Corynephoretea and Festuco-Brom- etea): Koelerion glaucae complex (1), Armerio-Festucetum trachyphyllae (2a, typical; 2b, ruderalized), ruderalized ex-arable field (3), and Allio-Stipetum capillatae (4). We used a plot-based approach for recording vegetation data and flower-visiting wild bees. Releves were sampled and flower- visiting bees netted on defined flower resources (2004, 2005). Data were analyzed by ordination, mixed linear models and regres- sion analysis. Phytosociological table and DCA show clear floristic differentiations between the vegetation types and complexes. For the bee data there were weaker species-based differentiations. In the year 2004 there were two bee assemblages, in the year 2005 this dif- ferentiation was not detectable. The most species- and individual-rich wild-bee populations were detected in the vegetation types 2b, 3 and 4. These types were characterized by a high diversity of entomophilous plant species in combination with high flower density. Although ruderalized sandy grasslands have only moderate conservation value based on vegetation characteristics, they offer remarkable resources for species-rich populations of wild bees. Important flower resources for endangered wild-bee species are, among others, Centaurea stoebe s.l., Berteroa incana and Carduus nutans. The diversity characteristics of the studied vegetation types or complexes do not always correspond to those of the flower-visit- ing bees, which should be taken into account in developing conservation strategies.

Triple interaction network among flowers, flower visitors and crab spiders in a grassland ecosystem

This study presents the first description of a tri-trophic interaction network with crab spiders as predators. Monthly observations of flowering entomophilous plant species were recorded between December 2009 and March 2010 and their flower visitors and predators (crab spiders) were caught, with or without prey. Moreover, flower visitors of different orders were caught to evaluate the amount of pollen transported. In order to analyze changes in the plant species and crab spiders, we evaluated the interaction networks in which we had removed different orders of prey (Hymenoptera, Diptera and Lepidoptera) from the original network. Our results indicate that crab spiders select their preys within the community. Furthermore, the Hymenoptera carried higher pollen loads and were the less frequent prey. When the Diptera preys were removed from the initial interaction network, network changes mainly affected the species richness of crab spiders. Decrease in density of Diptera could increase plant resources useful for flower visitors carrying great pollen loads and could promote pollination. Crab spider prey might be restricted to only the more vulnerable flower visitors (e.g. smaller dimensions, without sting or with delicate cuticula) which consume resources and are inefficient as pollen carriers. The selected predation could not negatively affect the fitness of plants.

Restoration of riverine inland sand dune complexes: implications for the conservation of wild bees

Summary 1. The evaluation of restoration measures is an important task of conservation biology. Inland sand dunes and dry, oligotrophic grasslands have become rare habitat types in large parts of Central Europe and their restoration and management is of major importance for the preservation of many endangered plant and insect species. Within such habitats, it is important to restore key ecosystem services, such as pollination networks. As wild bees are the most important pollinators in many ecosystems, they represent a suitable key group to evaluate restoration measures. Furthermore, the recent decline of many bee species and the potential ecological and economic consequences are currently topics of strong scientific interest. 2. We studied the succession of bee communities in response to restoration measures of sand dunes and sand grasslands and compared these communities with those of old sand dune complexes. 3. Our results show that wild bees respond rapidly to restoration measures indicated by a high species richness and abundance. The community structure of bees at restoration sites converged only slightly to those of the target sites. A higher similarity was found between bee communities at the restoration sites (sand dunes and grasslands), indicating that their close proximity was an important determinant of species overlap. Environmental factors such as the number of entomophilous plant species and moisture had a strong influence on wild bee species composition. 4. Synthesis and applications. The restoration of inland sand dune complexes provides opportunities for colonization by a diverse wild bee community. Although it is difficult to establish a given target community, restoration measures gave rise to a high pollinator diversity and abundance, suggesting that community function can be re‐established.

An experimental study of the pollination biology of the perennial halophyte Frankenia pauciflora var. gunnii (Frankeniaceae) in a South Australian salt marsh

Relatively little is known about the pollination biology or breeding systems of entomophilous plant species in salt-marsh habitats. In the present study, the pollination biology of the perennial halophyte Frankenia pauciflora DC. var. gunnii Summerh. (Frankeniaceae) was investigated in a salt marsh near Goolwa, South Australia. The flowering peak of this species occurs in summer and flowers are visited by a diverse array of insects in the Diptera, Hymenoptera and Lepidoptera. An experiment was performed to test for the presence of pollen limitation in the field. Flowers to which outcross pollen was added produced significantly more fruits and significantly more seeds per fruit than did unmanipulated control flowers. Average seed weight per fruit did not differ significantly between control and pollen-addition flowers. In glasshouse experiments, flowers to which cross-pollen was added produced significantly more fruit than did flowers to which self-pollen was added, suggesting the presence of a facultatively xenogamous breeding system.

Perianth organization and intra-specific floral variability

Floral symmetry and fusion of perianth parts are factors that contribute to fine-tune the match between flowers and their animal pollination vectors. In the present study, we investigated whether the possession of a sympetalous (fused) corolla and bilateral symmetry of flowers translate into decreased intra-specific variability as a result of natural stabilizing selection exerted by pollinators. Average size of the corolla and intra-specific variability were determined in two sets of southern Spanish entomophilous plant species. In the first set, taxa were paired by family to control for the effect of phylogeny (phylogenetically independent contrasts), whereas in the second set species were selected at random. Flower size data from a previous study (with different species) were also used to test the hypothesis that petal fusion contributes to decrease intra-specific variability. In the phylogenetically independent contrasts, floral symmetry was a significant correlate of intra-specific variation, with bilaterally symmetrical flowers showing more constancy than radially symmetrical flowers (i.e. unsophisticated from a functional perspective). As regards petal fusion, species with fused petals were on average more constant than choripetalous species, but the difference was not statistically significant. The reanalysis of data from a previous study yielded largely similar results, with a distinct effect of symmetry on variability, but no effect of petal fusion. The randomly-chosen species sample, on the other hand, failed to reveal any significant effect of either symmetry or petal fusion on intra-specific variation. The problem of low-statistical power in this kind of analysis, and the difficulty of testing an evolutionary hypothesis that involves phenotypic traits with a high degree of morphological correlation is discussed.

Analysis of pollen loads in a wild bee community (Hymenoptera: Apidae) – a method for elucidating habitat use and foraging distances

Resource utilisation and foraging ranges of Apidae (excluding Apis and Bombus) were studied in sandy grasslands of the temperate zone by pollen analysis combined with direct observation of bees. Planttaxa composition of 558 pollen loads collected from 56 bee species was determined. We recorded flower-visits using plot-based observations and resource utilisation using pollen analysis. For the most important entomophilous plant species flower-visitation and pollen-analytical data correspond (e.g. Berteroa incana, Centaurea stoebe, Potentilla argentea). Whenever pollen of plant species that are limited in their occurrence could be detected, we were able to use pollen analysis to determine foraging distances, but not maximum foraging distances. Using tree pollen, minimum flight ranges up to 1250 m were documented even for bees with 7 mm body size. Thus pollen analysis not only provides valuable information about foraging on different spatial scales, but also enables foraging ranges to be calculated without experimental manipulation.

Trends in the formation of biotopic complexes of bumblebees (Hymenoptera, Apidae: Bombini) in northern taiga karst landscapes of the Western Russian Plain

Main trends in the formation of biotopic complexes of bumblebees in the northern taiga zone are analyzed. It is proposed that Eurasian forest species of bumblebees ( Bombus (Th.) schrencki, B. (Mg.) conso- brinus , etc.) are coadaptively connected with entomophilous plant species belonging to the synusia of Eurosi- berian riverine-mountain meadow tall herbage, with the numbers of species in both biotic groups (pollinating insects and plants) and their abundance being greater in the landscape characterized by a high degree of karsti- fication. In the biotopic bumblebee complex of a large river valley, the relative abundance of forest bumblebee species is 2.5-5.3 times lower than in other complexes, whereas that of meadow species is two orders of mag- nitude higher due to favorable thermal conditions and a large number of habitats with mesophilic herbage and legumes. Each of the distinct ecogeographic groups of bumblebees and the corresponding synusiae (each com- prising entomophilous plants of different taxonomic groups) appear to be coadapted. This is probably a result of the diffuse coevolution of pollinators and plants belonging to the genetically unified biota. DOI: 10.1134/S1067413606030039

Quantitative floral phenology at the landscape scale: Is a comparative spatio-temporal description of ‘‘flowering landscapes’’ possible?

Entomophilous flowers form the food resources for insect pollinators. Many pollinator species forage at the landscape scale and depend on floral resources that are highly variable in space and time. We present a general model approach in which the floral resources of plant communities are estimated by the floral phenology and the cover of entomophilous plant species. We applied this landscape model in a case study for three landscape sections (1.5–2.2 km 2 ) with strongly differing land-use patterns. The comparison between a conservation area and two agricultural landscapes shows extreme differences in the quantities and in the course of floral resources. In a stepwise simplification of the landscape model we tested the effects of input data with lower spatio-temporal resolution. Even if input data for floral phenology and vegetation have a low resolution, the landscape model allows a ranking of landscape-specific floral resource potentials. The results of the case study encourage the use of landscape models to estimate floral resource potentials. The assessment of floral resource potentials may help to define this essential landscape quality for evaluation in practical nature conservation.

Sex Allocation and Reproductive Success in the Andromonoecious Perennial Solanum carolinense (Solanaceae). II. Paternity and Functional Gender.

According to Bateman's principle, male fitness in entomophilous plant species should be limited by mating opportunity, which is influenced by the size or number of flowers. We determined male-specific fitness consequences of floral phenotype in andromonoecious Solanum carolinense, examined the relationship between male and female reproductive success within plants, and evaluated the distribution of functional gender among plants. A maximum likelihood-based paternity analysis, based on multilocus allozyme phenotypes of parents and offspring from four experimental plots, was used to determine male reproductive success and its relationship to floral phenotype. Male success was enhanced by an increase in the proportion of male flowers produced but not by an increase in total flower number, even though all flowers contain male parts. Larger flower size increased male success in only one plot. Male and female reproductive success were negatively correlated, and plants varied in functional gender from completely female to completely male. This gender specialization may occur because hermaphroditic and male flowers differ in their ability to contribute to male and female success. Although sex allocation theory predicts a positive relationship between the size or number of plant parts and reproductive success, this study indicates that aspects of floral morphology that affect gender specialization should also be considered.

Efficiency of various insects in germplasm regeneration of carrot, onion and turnip rape accessions

AbstractSeed regeneration is one of the most important tasks in genebank work. To regenerate germplasm of allogamous, entomophilous plant species in isolation facilities, insects are often used as pollen vectors. The objective of this study was to determine the effect of pollinator species, pollinator densities, pollinator combinations, and flower preferences on the seed quantity and quality of Daucus carota, Allium cepa, and Brassica rapa. The isozyme phosphoglucoisomerase (PGI) served as genetic marker in determining outcrossing rates and pollen dispersal distances. Field plots and isolation cages without insects were used as controls. The pollinators studied consisted of the following insect species from German native fauna: red mason bees (Osmia rufa L.), hoverflies (Eristalis tenax L.), and blowflies (Calliphora sp. and Lucilia sp.). In D. carota and B. rapa, higher seed yields were achieved in isolation cages than in field plots, but in A. cepa lower seed yields were obtained in the isolation cages. Although O. rufa showed no liking for A. cepa, unintentional pollination was effected by this insect in isolation cages. Lower insect densities were necessary for O. rufa than for the various fly species.