Worldwide most pollinators, e.g. bumblebees, are undergoing global declines. Loss of genetic diversity can play an essential role in these observed declines. In this paper, we investigated the level of genetic diversity of seven declining Bombus species and four more stable species with the use of microsatellite loci. Hereto we genotyped a unique collection of museum specimens. Specimens were collected between 1918 and 1926, in 6 provinces of the Netherlands which allowed us to make interspecific comparisons of genetic diversity. For the stable species B. pascuorum, we also selected populations from two additional time periods: 1949–1955 and 1975–1990. The genetic diversity and population structure in B. pascuorum remained constant over the three time periods. However, populations of declining bumblebee species showed a significantly lower genetic diversity than co-occurring stable species before their major declines. This historical difference indicates that the repeatedly observed reduced genetic diversity in recent populations of declining bumblebee species is not caused solely by the decline itself. The historically low genetic diversity in the declined species may be due to the fact that these species were already rare, making them more vulnerable to the major drivers of bumblebee decline.
Citation: Roberts SPM, Potts SG, Biesmeijer K, Kuhlmann M, Kunin B, Ohlemüller R (2011) Assessing continentalscale risks for generalist and specialist pollinating bee species under climate change. BioRisk 6: 1-18. AbstractIncreased risks of extinction to populations of animals and plants under changing climate have now been demonstrated for many taxa. This study assesses the extinction risks to species within an important genus of pollinating bees (Colletes: Apidae) by estimating the expected changes in the area and isolation of suitable habitat under predicted climatic condition for 2050. Suitable habitat was defined on the basis of the presence of known forage plants as well as climatic suitability. To investigate whether ecological specialisation was linked to extinction risk we compared three species which were generalist pollen foragers on several plant families with three species which specialised on pollen from a single plant species. Both specialist and generalist species showed an increased risk of extinction with shifting climate, and this was particularly high for the most specialised species (Colletes anchusae and C. wolfi). The forage generalist C. impunctatus, which is associated with Boreo-Alpine environments, is potentially threatened through significant reduction in available climatic niche space. Including the distribution of the principal or sole pollen forage plant, when modelling the distribution of monolectic or narrowly oligolectic species, did not improve the predictive accuracy of our models as the plant species were considerably more widespread than the specialised bees associated with them.
22 23 Abstract 24 Romania and Ukraine share the Black Sea coastline, the Danube Delta and associated habitats, 25 which harbor the unique Pontocaspian biodiversity. Pontocaspian biota represents endemic 26 aquatic taxa adapted to the brackish (anomalohaline) conditions, which evolved in the Caspian 27 and Black Sea basins. Currently, this biota is diminishing both in the numbers of species and28 their abundance because of human activities. Consequently, its future persistence strongly 29 depends on the adequacy of conservation measures. Romania and Ukraine have a common 30 responsibility to effectively address the conservation of this biota. The socio-political and legal 31 conservation frameworks, however, differ in the two countries -Romania is a member of the 32 European Union (EU), thus complying with the EU environmental policy, whereas Ukraine is an 33 EU-associated country. This may result in differences in the social network structure of 34 stakeholder institutions with different implications for Pontocaspian biodiversity conservation.35 Here, we study the structure and implications of the social network of stakeholder organizations 36 involved in conservation of Pontocaspian biodiversity in Romania, and compare it to Ukraine. 37 We apply a mix of qualitative and quantitative social network analysis methods to combine the 38 content and context of the interactions with relational measures. We show that the social 39 networks of stakeholder organizations in Romania and Ukraine are very different. Structurally, in 40 Romanian network there is a room for improvement through e.g. more involvement of 3 41 governmental and non-governmental organizations and increased motivation of central 42 stakeholders to initiate conservation action, whereas Ukrainian network is close to optimal. 43 Regardless, both networks translate into sub-optimal conservation action and the road to optimal 44 conservation is different. We end with sketching implications and recommendations for 45 improved national and cross-border conservation efforts. 46 47 Introduction 48 Pontocaspian (PC) biota is a unique, endemic flora and fauna which includes mollusks, 49 crustaceans, planktonic groups (e.g. dinoflagellates and diatoms) and fish species. This 50 biodiversity evolved in brackish (anomalohaline) conditions of the Black Sea and Caspian Sea 51 basins over the past 2.5 million years [1,2] and nowadays PC communities inhabit the Northern 52 Black Sea, Sea of Azov, Caspian Sea and adjacent river and lake systems, stretching across the 53 vast political and administrative boundaries of the surrounding countries . Currently, PC biota 54 is decreasing in numbers of species and abundances as a result of human activities and their 55 future persistence strongly depends on the adequacy of conservation measures [1,4,5]. Romania 56 and Ukraine hold an important part of the PC habitats. PC species in Romania are limited to the 57 Razim-Sinoe-Babadag lake complex [6,7], the area along the Danube River and the Black Sea 58 coastal zone, which t...
While shifts to high-intensity land cover have caused overwhelming biodiversity loss, it remains unclear how important natural land cover is to the occurrence, and thus the conservation, of different species groups. We used over 4 million plant species’ observations to evaluate the conservation importance of natural land cover by its association with the occurrence probability of 1 122 native and 403 exotic plant species at 1 km resolution by species distribution models. We found that 74.9% of native species, 83.9% of the threatened species and 77.1% rare species preferred landscapes with over 50% natural land cover, while these landscapes only accounted for 15.6% of all grids. Most species preferred natural areas with a mixture of forest and open areas rather than areas with completely open or forested nature. Compared to native species, exotic species preferred areas with lower natural land cover and the cover of natural open area, but they both preferred extremely high and low cover of natural forest area. Threatened and rare species preferred higher natural land cover, either cover of natural forest area or cover of natural open area than not threatened and common species, but rare species were also more likely to occur in landscapes with 0–25% cover of natural open area. Although more natural land cover in a landscape will not automatically result in more native species, because there is often a non-linear increase in species occurrence probability when going from 0% to 100% natural land cover, for conserving purposes, over 80% natural land cover should be kept in landscapes for conserving threatened and very rare species, and 60% natural land cover is the best for conserving common native species. Our results stress the importance of natural areas for plant species’ conservation. It also informs improvements to species conservation by increasing habitat diversity.
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