Climate drives plant-pollinator interactions even along small-scale climate gradients: the case of the Aegean.

Plant-pollinator network structure is the outcome of ecological and evolutionary processes, and although the importance of environmental factors is beyond doubt, our knowledge of how abiotic factors (e.g. climate) shape plant-pollinator networks remains limited. This knowledge gap is critical, as climate change poses a major threat to ecosystems, especially in the Mediterranean. This study focuses on one of the hottest parts of the Mediterranean Basin, the Aegean Archipelago, Greece, and examines how climate affects species richness and network properties (e.g. nestedness, modularity and specialisation) - either directly or indirectly through species richness. We sampled systematically 39 local plant-pollinator networks on eight islands along a north-south climate gradient in the Aegean. All plant-pollinator material used in the analyses was collected in 2012 and identified to species level. Aspects of climate used in the models were expressed as average conditions (mean temperature and annual precipitation) or as seasonal variability (isothermality and temperature seasonality). Structural properties of plant-pollinator networks were found to be strongly associated with species richness, which was in turn affected by climate, implying that pollination network structure is driven indirectly by climate. In addition, climate had a direct effect on network structure, especially on modularity and specialisation. Different aspects of climate affected network properties in different ways. We highlight that even in a relatively narrow latitudinal gradient, such as within the Aegean Sea region, climate constitutes a significant driver of plant-pollinator interactions.

Molecular species delimitation in the genus Eumerus (Diptera: Syrphidae).

Eumerus is one of the most diverse genera of hoverfly worldwide. Species delimitation within genus is considered to be difficult due to: (a) lack of an efficient key; (b) non-defined taxonomical status of a large number of species; and (c) blurred nomenclature. Here, we present the first molecular study to delimit species of the genus by using a fragment of the mitochondrial cytochrome-c oxidase subunit I gene (COI) gene. We assessed 75 specimens assigned to 28 taxa originating from two biogeographic zones: 22 from the western Palaearctic and six from the Afrotropical region. Two datasets were generated based on different sequence lengths to explore the significance of availability of more polymorphic sites for species delimitation; dataset A with a total length of 647 bp and dataset B with 746 bp. Various tree inference approaches and Poisson tree processes models were applied to evaluate the putative 'taxonomical' vs. 'molecular' taxa clusters. All analyses resulted in high taxonomic resolution and clear species delimitation for both the dataset lengths. Furthermore, we revealed a high number of mitochondrial haplotypes and high intraspecific variability. We report two major monophyletic clades, and seven 'molecular' groups of taxa formed, which are congruent with morphology-based taxonomy. Our results support the use of the mitochondrial COI gene in species diagnosis of Eumerus.

Influence of landscape context on the abundance and diversity of bees in Mediterranean olive groves.

The diversity and abundance of wild bees ensures the delivery of pollination services and the maintenance of ecosystem diversity. As previous studies carried out in Central Europe and the US have shown, bee diversity and abundance is influenced by the structure and the composition of the surrounding landscape. Comparable studies have so far not been carried out in the Mediterranean region. The present study examines the influence of Mediterranean landscape context on the diversity and abundance of wild bees. To do this, we sampled bees in 13 sites in olive groves on Lesvos Island, Greece. Bees were assigned to five categories consisting of three body size groups (small, medium and large bees), the single most abundant bee species (Lasioglossum marginatum) and all species combined. The influence of the landscape context on bee abundance and species richness was assessed at five radii (250, 500, 750, 1000 and 1250 m) from the centre of each site. We found that the abundance within bee groups was influenced differently by different landscape parameters and land covers, whereas species richness was unaffected. Generally, smaller bees' abundance was impacted by landscape parameters at smaller scales and larger bees at larger scales. The land cover that influenced bee abundance positively was olive grove, while phrygana, conifer forest, broad-leaved forest, cultivated land, rock, urban areas and sea had mostly negative or no impact. We stress the need for a holistic approach, including all land covers, when assessing the effects of landscape context on bee diversity and abundance in the Mediterranean.

Establishment of a cross-European field site network in the ALARM project for assessing large-scale changes in biodiversity.

The field site network (FSN) plays a central role in conducting joint research within all Assessing Large-scale Risks for biodiversity with tested Methods (ALARM) modules and provides a mechanism for integrating research on different topics in ALARM on the same site for measuring multiple impacts on biodiversity. The network covers most European climates and biogeographic regions, from Mediterranean through central European and boreal to subarctic. The project links databases with the European-wide field site network FSN, including geographic information system (GIS)-based information to characterise the test location for ALARM researchers for joint on-site research. Maps are provided in a standardised way and merged with other site-specific information. The application of GIS for these field sites and the information management promotes the use of the FSN for research and to disseminate the results. We conclude that ALARM FSN sites together with other research sites in Europe jointly could be used as a future backbone for research proposals.

COI barcodes for identification of Merodon hoverflies (Diptera, Syrphidae) of Lesvos Island, Greece.

DNA barcoding has become a useful system for linking different biological life stages, and for identification of species within a known taxonomic framework. In this study, we generated mitochondrial DNA COI barcodes using adult specimens of all 22 species of the hoverfly genus Merodon (Diptera, Syrphidae) occurring on Lesvos island (Greece). The generated COI barcodes could well discriminate between all Merodon taxa of Lesvos, except for M. loewi and M. papillus that shared the same haplotype, despite their clear morphological differences. In addition, the barcodes revealed two cases of hitherto unknown morphologically cryptic species close to M. avidus and M. nigritarsis, respectively. Because only few successful rearings of immature stages of Merodon hoverflies are available, the larval host plant remains unknown for these phytophagous taxa. The obtained COI barcode library for the Merodon spp. of Lesvos will constitute a tool to link any unknown immature stages with already known species, and thus provide important life-history information and promise for ecological studies.

Pollination ecology and patch-dependent reproductive success of the rare perennial Gentiana pneumonanthe L.

The reproductive behaviour of Gentiana pneumonanthe L., a rare plant species in The Netherlands, was studied in a relatively large wet heathland population during summer 1989. The species co-occurred with the grass Molinia caerulea and co-flowered with Erica tetralix and Calluna vulgaris. The flowering period lasted from July to October, peaking in late August to late September. Flowers are protandrous. The species appeared to be self-compatible, but spontaneous self-pollination was strongly limited. Hand-crossing and hand-selfing resulted in the same amount of seed set as in natural pollination. Reproductive success was dramatically reduced late in the season. Pollination was achieved sternotribically by the species Bombus pascuorum, which visited the flowers for nectar. In the study area, three patch types were distinguished: co-dominated by Erica, by Calluna and Erica, and by Molinia, respectively. Frequency of visits to Gentiana was highest in the Erica-patch. However, this did not result in a higher seed set. In the Molinia-patch seed set was reduced. However, in the Molinia-patch the mean number of ovules was greater than in the others (as high as in plants raised indoors and in cross-pollinated plants). Fruits from the Calluna-patch had less ovules than those from the Erica-patch. We conclude that, in this remnant population, Gentiana is not pollination-limited. However, it is likely that in the Molinia-patch geitonogamy is frequent, which may lead to inbreeding depression. The greater number of ovules observed in Molinia-patches may reflect an excess of nutrients available there, relative to the Calluna-patch where there may be reduced water availability.