Moderation is best: Effects of grazing intensity on plant-flower visitor networks in Mediterranean communities

The structure of pollination networks is an important indicator of ecosystem stability and functioning. Livestock grazing is a frequent land use practice that directly affects the abundance and diversity of flowers and pollinators and, therefore, may indirectly affect the structure of pollination networks. We studied how grazing intensity affected the structure of plant-flower visitor networks along a wide range of grazing intensities by sheep and goats, using data from 11 Mediterranean plant-flower visitor communities from Lesvos Island, Greece. We hypothesized that intermediate grazing might result in higher diversity as predicted by the Intermediate Disturbance Hypothesis, which could in turn confer more stability to the networks. Indeed, we found that networks at intermediate grazing intensities were larger, more generalized, more modular, and contained more diverse and even interactions. Despite general responses at the network level, the number of interactions and selectiveness of particular flower visitor and plant taxa in the networks responded differently to grazing intensity, presumably as a consequence of variation in the abundance of different taxa with grazing. Our results highlight the benefit of maintaining moderate levels of livestock grazing by sheep and goats to preserve the complexity and biodiversity of the rich Mediterranean communities, which have a long history of grazing by these domestic animals.The research has been co-financed by the European Union (European Social Fund—ESF) and Greek National funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF)—Research Funding Program: THALES: Investing in knowledge society through the European Social FundPeer Reviewe

Effects of grazing intensity on pollinator abundance and diversity, and on pollination services

1. Pollinating insects provide important ecosystem services and are influenced by the intensity of grazing. Based on the Intermediate Disturbance Hypothesis (IDH), pollinator diversity is expected to peak at intermediate grazing intensities. However, this hump-shaped relationship is rarely found. 2. The effect of grazing intensity was tested on flower cover, on the abundance and richness of bees, hoverflies and bee flies, and on pollination services to early-flowering bee-pollinated Asphodelus ramosus L. For that, we used data on 11 plant–pollinator phryganic communities from Lesvos Island (Greece) widely differing in grazing intensities. 3. Flower abundance and richness showed hump-shaped relationships with grazing intensity. Grazing affected the abundance and richness of bees and hoverflies directly and also indirectly, through changes in the flower community. Grazing influenced directly the richness but not the abundance of bee flies. Overall, pollinator abundance and richness showed hump-shaped relationships with grazing intensity, but variations in strength (hoverfly abundance) and direction (bee community) of the effect appeared along the season. Early in the season, grazing increased bee abundance but decreased richness, resulting in increased pollen limitation in A. ramosus. 4. The effects of grazing on pollinators vary with the intensity of the disturbance, generally supporting the IDH, and the timing of land-use activities may influence pollination services. Management strategies should include moderate grazing levels to preserve overall diversity in this area, however, the conservation of particular early bee or bee-pollinated species may benefit from reduced grazing in early spring.The research has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program ‘Education and Lifelong Learning’ of the National Strategic Reference Framework (NSRF) – Research Funding Program: THALES. Investing in knowledge society through the European Social Fund.Peer Reviewe

DNA barcoding and male genital morphology reveal five new cryptic species in the West Palearctic bee Seladonia smaragdula (Vachal, 1895) (Hymenoptera: Apoidea: Halictidae)

Pauly, Alain, Devalez, Jelle, Sonet, Gontran, Nagy, Zoltán Tamás, Boevé, Jean-Luc (2015): DNA barcoding and male genital morphology reveal five new cryptic species in the West Palearctic bee Seladonia smaragdula (Vachal, 1895) (Hymenoptera: Apoidea: Halictidae). Zootaxa 4034 (2): 257-290, DOI: http://dx.doi.org/10.11646/zootaxa.4034.2.

FIGURE 22 in DNA barcoding and male genital morphology reveal five new cryptic species in the West Palearctic bee Seladonia smaragdula (Vachal, 1895) (Hymenoptera: Apoidea: Halictidae)

FIGURE 22. Comparison between the species of the clade "S. smaragdula + S. phryganica" in the S. smaragdula complex, showing ventral view of the large projection of the gonocoxites; first picture (a) reproduced from Pauly & Rassel (1982), other pictures by Pauly & Cillis; a, S. smaragdula (Croatia, Ugljan); b, S. smaragdula (France, Porquerolles); c, S. phryganica (Greece, Dafni); d, S. phryganica (Greece, Crete).Published as part of Pauly, Alain, Devalez, Jelle, Sonet, Gontran, Nagy, Zoltán Tamás & Boevé, Jean-Luc, 2015, DNA barcoding and male genital morphology reveal five new cryptic species in the West Palearctic bee Seladonia smaragdula (Vachal, 1895) (Hymenoptera: Apoidea: Halictidae), pp. 257-290 in Zootaxa 4034 (2) on page 284, DOI: 10.11646/zootaxa.4034.2.2, http://zenodo.org/record/24496

Bumblebee diversity and pollination networks along the elevation gradient of Mount Olympus, Greece

Aim We studied bumblebee diversity and bumblebee pollination networks along the altitudinal gradient of Mt. Olympus, a legendary mountain in Central Greece, also known for its exceptional flora. Location Mt. Olympus, Central Greece. Taxon Bombus (Latreille, 1802). Methods We explored 10 study sites located on the north‐eastern slope of the mountain, from 327 to 2,596 m a. s. l. Bumblebee surveys were carried out on a monthly basis using pan traps (years 2013 and 2014) and random transect observations assisted by hand netting (years 2013, 2014, and 2016); visited flowering plants and their diversity were recorded during the transect observations. Results With a total of 22 recorded bumblebee species and one species complex, Mt. Olympus is one of the richest mountains in Mediterranean Europe regarding bumblebee diversity. Bombus quadricolor was recorded as a new species for Greece, whereas four species were recorded at their southernmost distribution limit, therefore possibly vulnerable to climate change. Species richness of both bumblebees and plants in flower followed a unimodal pattern along the altitudinal gradient, the former peaking at high altitudes (1,900–2,200 m a.s.l.), the latter at lower to intermediate altitudes (500–1,500 m a.s.l.). Bumblebee–plant visitation networks were larger, more diverse and more generalized in the between intermediate altitudes (1,500–1,800 m a.s.l.), while nestedness peaked at low and high altitudes. Main conclusions Our results disclose the differential significance of the altitudinal zones of Mt. Olympus for the conservation of the diversity of bumblebees and their host plants, as well as of the interactions among them. Furthermore, they highlight the importance of this mountain, because of its South‐European location, regarding climate change impacts on the bumblebee fauna of Europe. All in all, they point towards more reinforced conservation measures to be taken including the expansion of the protection status to the entire mountain.ISSN:1366-9516ISSN:1472-464

High species turnover and unique plant-pollinator interactions make a hyperdiverse mountain

We studied α- and β-diversity of pollinators, flowering plants and plant–pollinator interactions along the altitudinal gradient of Mt. Olympus, a legendary mountain and biodiversity hotspot in Central Greece. We explored 10 study sites located on the north-eastern slope of the mountain, from 327 to 2596 m a.s.l. Insect surveys were conducted once a month using hand netting (years 2013, 2014 and 2016), and they were combined with recordings of flowering plant diversity (species richness and flower cover). We then calculated α- and β-diversity of pollinators, plants in flower and plant–pollinator interactions, and explored their demographic response along the altitudinal gradient. Alpha diversity of pollinators, plants and plant–pollinator interactions were altitude dependent; α-diversity of all pollinators, bees, non-bumblebee bees, bee flies and butterflies showed linear declines with altitude, whereas those of hoverflies and bumblebees showed unimodal patterns. Beta diversity and its turnover component of all pollinators, hoverflies, bees, bumblebees, non-bumblebee bees, butterflies and plants showed linear increases, whereas those of bee flies and of plant–pollinator interactions varied independently from the pairwise altitudinal difference. The high dissimilarity and uniqueness of pollination networks, which is probably a result of the high biodiversity and endemism of Mt. Olympus, is driven by species turnover and the formation of new interactions between new species. Contrasting to the monotonic decline of the remaining groups, the unimodal patterns of hoverfly and bumblebee α-diversity are probably the effect of a higher tolerance of these groups to high-altitude environmental conditions. Our findings highlight that the high turnover of species and of pollination interactions along the altitudinal gradient are the mainstay of hyperdiverse mountains, a fact that conveys important historical, ecological and conservational implications.ISSN:0021-8790ISSN:1365-265

FamiliPlantsDryad

Degree and d' for the plant species in the study network

SummaryNetLevelDryad

Network-level characteristics for the 33 study network

StandardNetwDryad

Network-level characteristics for the standardized network

GuildDryad

Degree and d' for each insect species in the study network