@article{SoutoVeigaGroeneveldEnrightetal.2022, author = {Souto-Veiga, Rodrigo and Groeneveld, Juergen and Enright, Neal J. and Fontaine, Joseph B. and Jeltsch, Florian}, title = {Declining pollination success reinforces negative climate and fire change impacts in a serotinous, fire-killed plant}, series = {Plant ecology : an international journal}, volume = {223}, journal = {Plant ecology : an international journal}, number = {7}, publisher = {Springer}, address = {Dordrecht}, issn = {1385-0237}, doi = {10.1007/s11258-022-01244-7}, pages = {863 -- 881}, year = {2022}, abstract = {Climate change projections predict that Mediterranean-type ecosystems (MTEs) are becoming hotter and drier and that fires will become more frequent and severe. While most plant species in these important biodiversity hotspots are adapted to hot, dry summers and recurrent fire, the Interval Squeeze framework suggests that reduced seed production (demographic shift), reduced seedling establishment after fire (post fire recruitment shift), and reduction in the time between successive fires (fire interval shift) will threaten fire killed species under climate change. One additional potential driver of accelerated species decline, however, has not been considered so far: the decrease in pollination success observed in many ecosystems worldwide has the potential to further reduce seed accumulation and thus population persistence also in these already threatened systems. Using the well-studied fire-killed and serotinous shrub species Banksia hookeriana as an example, we apply a new spatially implicit population simulation model to explore population dynamics under past (1988-2002) and current (2003-2017) climate conditions, deterministic and stochastic fire regimes, and alternative scenarios of pollination decline. Overall, model results suggest that while B. hookeriana populations were stable under past climate conditions, they will not continue to persist under current (and prospective future) climate. Negative effects of climatic changes and more frequent fires are reinforced by the measured decline in seed set leading to further reduction in the mean persistence time by 12-17\%. These findings clearly indicate that declining pollination rates can be a critical factor that increases further the pressure on the persistence of fire-killed plants. Future research needs to investigate whether other fire-killed species are similarly threatened, and if local population extinction may be compensated by recolonization events, facilitating persistence in spatially structured meta-communities.}, language = {en} } @article{HuthSchwarzGorb2022, author = {Huth, Steven and Schwarz, Lisa-Maricia and Gorb, Stanislav N.}, title = {Quantifying the influence of pollen aging on the adhesive properties of Hypochaeris radicata pollen}, series = {Insects}, volume = {13}, journal = {Insects}, number = {9}, publisher = {MDPI}, address = {Basel}, issn = {2075-4450}, doi = {10.3390/insects13090811}, pages = {13}, year = {2022}, abstract = {Simple Summary Pollination is the transfer of pollen from a plant's male part (anther) to the corresponding female part (stigma). It is a fundamental biological process that ensures plant reproduction. Most studies investigate pollination from a biological perspective, but the underlying physical processes are poorly understood. Many plants rely on insects to transport pollen and the forces with which pollen adhere to insects and floral surfaces are fundamental for successful pollination. We quantified pollen adhesion by measuring the forces necessary to detach Hypochaeris radicata (catsear, a common insect-pollinated plant) pollen from glass and studied for the first time how the adhesion forces change with pollen aging. Our results show that newly formed adhesion bonds between H. radicata pollen and glass are stronger for fresh pollen than for old ones. On the other hand, when H. radicata pollen age in contact with glass, the adhesion between pollen and glass strengthens over time. These effects are probably caused by the viscous liquid covering most pollen (pollenkitt) changing its viscoelastic properties as it dries. Although pollination is one of the most crucial biological processes that ensures plant reproduction, its mechanisms are poorly understood. Especially in insect-mediated pollination, a pollen undergoes several attachment and detachment cycles when being transferred from anther to insect and from insect to stigma. The influence of the properties of pollen, insect and floral surfaces on the adhesion forces that mediate pollen transfer have been poorly studied. Here, we investigate the adhesive properties of Hypochaeris radicata pollen and their dependence on pollen aging by quantifying the pull-off forces from glass slides using centrifugation and atomic force microscopy. We found that the properties of the pollenkitt-the viscous, lipid liquid on the surface of most pollen grains-influences the forces necessary to detach a pollen from hydrophilic surfaces. Our results show that aged H. radicata pollen form weaker adhesions to hydrophilic glass than fresh ones. On the other hand, when a pollen grain ages in contact with glass, the adhesion between the two surfaces increases over time. This study shows for the first time the pollen aging effect on the pollination mechanism.}, language = {en} } @article{HobbhahnKuechmeisterPorembski2006, author = {Hobbhahn, Nina and K{\"u}chmeister, Heike and Porembski, Stefan}, title = {Pollination biology of mass flowering terrestrial Utricularia species (Lentibulariaceae) in the Indian Western Ghats}, series = {Plant biology}, volume = {8}, journal = {Plant biology}, number = {6}, publisher = {Wiley-Blackwell}, address = {Oxford}, issn = {1435-8603}, doi = {10.1055/s-2006-924566}, pages = {791 -- 804}, year = {2006}, abstract = {The pollination biology of three mass flowering Utricularia species of the Indian Western Ghats, U. albocaerulea, U. purpurascens, and U. reticulata, was studied for the first time by extensive observation of flower visitors, pollination experiments, and nectar analyses. The ephemerality of the Utricularia habitats on lateritic plateaus, weather conditions adverse to insects, lack of observations of flower visitors to other Utricularia spp., and the predominance of at least. facultative autogamy in the few Utricularia species studied so far suggested that an autogamous breeding system is the common case in the genus. In contrast, we showed that the studied populations are incapable of autonomous selfing, or that it is an event of negligible rarity, although P/O was similarily low as in autogamous species investigated by other authors. In all three species the spatial arrangement of the reproductive organs makes an insect vector necessary for pollen transfer between and within flowers. However, U. purpurascens and U. reticulata are highly self-compatible, which allows for visitor-mediated auto-selfing and geitonogamy on inflorescence and clone level. Floral nectar is present in extremely small volumes in all three species, but sugar concentrations are high. More than 50 species of bees, butterflies, moths, hawk moths, and clipterans were observed to visit the flowers, and flower morphology facilitated pollination by all observed visitors. The results are discussed in the context of the phenological characteristics of the studied species, especially the phenomenon of mass flowering, and the environmental conditions of their habitats.}, language = {en} } @phdthesis{Hahn2002, author = {Hahn, Robert}, title = {Das Bl{\"u}te-Best{\"a}uber-Netz auf Brachfl{\"a}chen : bioz{\"o}nologische Untersuchung zur Bedeutung von Brachen in einer intensiv genutzten Agrarlandschaft}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000652}, school = {Universit{\"a}t Potsdam}, year = {2002}, abstract = {In der vorliegenden Dissertation wird die Bedeutung von Brachen f{\"u}r Artenvielfalt und Stabilit{\"a}t von Bl{\"u}te-Best{\"a}uber-Nahrungsnetzen in agrarisch genutzten Landschaften anhand ausgew{\"a}hlter bl{\"u}tenbesuchender Insektengruppen (Syrphidae, Lepidoptera) untersucht. Die Freilandarbeiten fanden von 1998-2000 im Raum der Feldberger Seenlandschaft, Mecklenburg-Vorpommern, statt. Es werden die beiden Hauptnahrungsquellen Nektar und Pollen betrachtet, dabei fanden Untersuchungen zur Intensit{\"a}t der Bl{\"u}te-Best{\"a}uber-Interaktion auf Stilllegungsfl{\"a}chen, zum fl{\"a}chenbezogenen quantitativen Nektarangebot im Jahresverlauf, zur individuellen Pollennutzung bei Syrphiden und zur Breite und {\"U}berlappung der Nahrungsnischen bei den dominanten Arten Episyrphus balteatus, Metasyrphus corollae, Syritta pipiens und Sphaerophoria scripta statt. Im Ergebnis zeigt sich eine hohe Bedeutung der Brachfl{\"a}chen f{\"u}r die Stabilit{\"a}t des Bl{\"u}te-Best{\"a}uber-Netzes, w{\"a}hrend die Diversit{\"a}t von anderen, eher landschaftsbezogenen Faktoren abh{\"a}ngig ist.}, subject = {Feldberger Seenlandschaft ; Agrarlandschaft ; Brache ; Samenpflanzen ; Best{\"a}uber ; Artenreichtum}, language = {de} }