Browsing by Subject "BEES"

Sort by: Order: Results:

Now showing items 1-4 of 4
  • Abdi, Abdulhakim; Carrié, Romain; Sidemo-Holm, William; Cai, Zhanzhang; Boke Olén, Niklas; Smith, Henrik G; Eklundh, Lars; Ekroos, Johan Edvard (2021)
    Increasing land-use intensity is a main driver of biodiversity loss in farmland, but measuring proxies for land-use intensity across entire landscapes is challenging. Here, we develop a novel method for the assessment of the impact of land-use intensity on biodiversity in agricultural landscapes using remote sensing parameters derived from the Sentinel-2 satellites. We link crop phenology and productivity parameters derived from time-series of a two-band enhanced vegetation index with biodiversity indicators (insect pollinators and insect-pollinated vascular plants) in agricultural fields in southern Sweden, with contrasting land management (i.e. conventional and organic farming). Our results show that arable land-use intensity in cereal systems dominated by spring-sown cereals can be approximated using Sentinel-2 productivity parameters. This was shown by the significant positive correlations between the amplitude and maximum value of the enhanced vegetation index on one side and farmer reported yields on the other. We also found that conventional cereal fields had 17% higher maximum and 13% higher amplitude of their enhanced vegetation index than organic fields. Sentinel-2 derived parameters were more strongly correlated with the abundance and species richness of bumblebees and the richness of vascular plants than the abundance and species richness of butterflies. The relationships we found between biodiversity and crop production proxies are consistent with predictions that increasing agricultural land-use intensity decreases field biodiversity. The newly developed method based on crop phenology and productivity parameters derived from Sentinel-2 data serves as a proof of concept for the assessment of the impact of land-use intensity on biodiversity over cereal fields across larger areas. It enables the estimation of arable productivity in cereal systems, which can then be used by ecologists and develop tools for land managers as a proxy for land-use intensity. Coupled with spatially explicit databases on agricultural land-use, this method will enable crop-specific cereal productivity estimation across large geographical regions.
  • Klein, Antonia; Schultner, Eva; Lowak, Helena; Schrader, Lukas; Heinze, Juergen; Holman, Luke; Oettler, Jan (2016)
    The major transition to eusociality required the evolution of a switch to canalize development into either a reproductive or a helper, the nature of which is currently unknown. Following predictions from the 'theory of facilitated variation', we identify sex differentiation pathways as promising candidates because of their pre-adaptation to regulating development of complex phenotypes. We show that conserved core genes, including the juvenile hormone-sensitive master sex differentiation gene doublesex (dsx) and a kruppel homolog 2 (kr-h2) with putative regulatory function, exhibit both sex and morph-specific expression across life stages in the ant Cardiocondyla obscurior. We hypothesize that genes in the sex differentiation cascade evolved perception of alternative input signals for caste differentiation (i.e. environmental or genetic cues), and that their inherent switch-like and epistatic behavior facilitated signal transfer to downstream targets, thus allowing them to control differential development into morphological castes.
  • Toivonen, Marjaana; Herzon, Irina; Rajanen, Hanne; Toikkanen, Jenni; Kuussaari, Mikko (2019)
    Ecological intensification has been proposed as a strategy to mitigate the impacts of conventional intensive land use on pollinators and insect pollination. However, research has concentrated on the effects of land management on pollinator abundance and diversity, while studies directly measuring pollination services are still lacking for many crops and regions. This study examines the effects of landscape heterogeneity, pesticide use intensity and flowering time on insect pollination of turnip rape Brassica rapa ssp. oleifera, a major oil crop at high latitudes. The field experiment included monitoring pollinator visits on turnip rape flowers and measuring yield in 34 spring-sown turnip rape fields in Southern Finland. The fields were situated in two landscape types that differed in the cover of arable land and represented independent gradients of pesticide use intensity and flowering time. Based on flower visits and number of seeds per silique, turnip rape was best pollinated in fields with late flowering time. The result suggests a temporal mismatch between crop flowering and the availability of pollination service in early sown fields. The increase in flower visits during summer was steeper among fields with low than high pesticide use, possibly due to a faster colony growth of important bee pollinators. Pollinator community in turnip rape fields was more diverse in heterogeneous landscapes with less arable land than in homogeneous field-dominated landscapes, suggesting higher stability of pollination services in diverse landscapes. Total yield per plant was positively related to pesticide use intensity. The relationship between insect pollination and total yield was weakened by high compensation capacity of turnip rape, the plants producing more flowers under poor pollination.Synthesis and applications. Crop pollination can be enhanced by shifting sowing time to better match crop flowering to the peak availability of the most important pollinators. Reduced pesticide use may also enhance pollination services but can lead to the total yield reduction due to pests. This highlights the need for pollinator-friendly pest control methods to maintain turnip rape yields while conserving pollination services. Foreign Language AbstractTiivistelma Maatalouden ekologista tehostamista on esitetty strategiaksi, jonka avulla intensiivisen maankayton kielteisia vaikutuksia polyttajiin ja hyonteispolytykseen voidaan hillita. Tutkimukset maankayton vaikutuksista viljelykasvien hyonteispolytykseen kuitenkin puuttuvat yha monilta viljelykasveilta ja alueilta. Tama tutkimus tarkasteli maiseman monimuotoisuuden, torjunta-aineiden kayton ja kukinta-ajan vaikutusta rypsin hyonteispolytykseen. Peltokokeessa seurattiin polyttajien vierailuja rypsin kukilla ja mitattiin satoa 34 kevatrypsipellolla Uudellamaalla. Pellot sijaitsivat kahdessa maisematyypissa, joista toinen oli peltovaltainen ja toinen monimuotoisempi ja vahemman peltoa sisaltava. Lisaksi pellot erosivat toisistaan torjunta-aineiden kayton ja kukinta-ajan suhteen. Polyttajien kukkavierailut ja siementen maara per litu olivat korkeimmillaan myohaan kukkineilla rypsipelloilla, mika kertoo hyvasta polytyksesta. Tuloksen perusteella aikaisin kylvetyt rypsipellot saattavat kukkia liian aikaisin polyttajien saatavuuden nakokulmasta. Voimakkaimmin polyttajien maara lisaantyi kesan aikana niiden peltojen joukossa, joilla ei kaytetty torjunta-aineita. Mahdollinen selitys on, etta tarhamehilaisten ja kimalaisten yhdyskunnat kasvoivat nopeimmin naiden peltojen laheisyydessa. Polyttajien monimuotoisuus oli suurempi monimuotoisessa kuin peltovaltaisessa maisemassa, mika parantaa polytyspalvelun vakautta muuttuvissa olosuhteissa. Kokonaissato per kasvi nousi torjunta-aineiden kayton lisaantyessa. Hyonteispolytyksen ja sadon valista yhteytta heikensi rypsin hyva kompensaatiokyky, jonka ansiosta heikosti polyttyneet kasvit tuottivat enemman kukkia.Yhteenveto ja sovellukset. Viljelykasvin polytysta voi parantaa saatamalla kylvoaikaa siten, etta kasvin kukinta ajoittuu tarkeimpien polyttajien runsaushuippuun. Torjunta-aineiden kayton vahentaminen voi parantaa polytysta mutta laskea samaan aikaan satoa tuholaisten ja rikkakasvien lisaantymisen takia. Polyttajaystavallisten kasvinsuojelukeinojen kehittaminen on tarkeaa korkeiden rypsisatojen ja polytyspalveluiden sailymisen kannalta. Crop pollination can be enhanced by shifting sowing time to better match crop flowering to the peak availability of the most important pollinators. Reduced pesticide use may also enhance pollination services but can lead to the total yield reduction due to pests. This highlights the need for pollinator-friendly pest control methods to maintain turnip rape yields while conserving pollination services.
  • Paukkunen, Juho; Pöyry, Juha; Kuussaari, Mikko (2018)
    1. Kleptoparasitic and parasitoid insects are expected to be particularly sensitive to changes in habitat availability due to their high trophic position and small population sizes compared with their hosts, but there are only few quantitative studies on their population changes. 2. Here, we studied the distribution and abundance of 48 kleptoparasitic and parasitoid species of cuckoo wasps (Chrysididae) and eight selected host species recorded in Finland from 1840 to 2015 based on an extensive survey of entomological collections. Population trends were assessed by studying changes in occupancy in 10 9 10 km grid squares between two study periods, 1840-1967 and 1968-2015. 3. Statistically significant decreases in occurrence were found for 11 cuckoo wasp species and one host species, while significant increases were not observed for any species. Trends of cuckoo wasps and their hosts were positively correlated, and changes were generally stronger in cuckoo wasps than in their hosts. 4. In a comparative analysis of species traits, abundance, body size and nesting type of host were related to occurrence changes of cuckoo wasps. Scarce and small species that use above ground-nesting hosts declined more than abundant and large species that use ground-nesting hosts. 5. Cuckoo wasp species dependent on dead wood are more vulnerable to changes in the environment than species associated with open sandy habitats. While both groups of species have probably suffered from habitat loss, the emergence of secondary habitats may have benefitted species living in sandy areas and compensated for the negative impact of habitat destruction.