Kwak 1978
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Kwak, M. M. 1978: Pollination, Hybridization and Ethological Isolation of Rhinanthus minor and R. serotinus (Rhinanthoideae: Scrophulariaceae) by Bumblebees (Bombus Latr.). In: Taxon. Bd. 27, Nr. 2/3, ISSN 0040-0262, S. 145–158, doi:10.2307/1220235 (https://www.jstor.org/stable/1220235, abgerufen am 19. Mai 2020). (Übersetzung: Bestäubung, Hybridisierung und ethologische Isolierung von Rhinanthus minor und R. serotinus (Rhinanthoideae: Scrophulariaceae) durch Hummeln (Bombus Latr.))
Zusammenfassung: The pollination, hybridization and ethological isolation of sympatric and synchronously flowering annuals Rhinanthus minor and R. serotinus were studied. Pollination was achieved by nototribically and sternotribically pollinating bumblebees (Bombus spp.), i.e. the essential parts of the flower contacts the dorsal respectively the ventral side of the insect’s body. In general, pollination behaviour was related to tongue lengths of bumblebee species. Bumblebees could bring about species hybridization by visits to both plants species during one foraging trip as nototribic or as sternotribic pollinators and species isolation by visits to only one species during one foraging trip or by visits to one species nototribically and to the other sternotribically during one foraging trip. Hybridization between the two annual Rhinanthus species resulted in the rise of hybrid swarms. Partial isolation could be effected if medium-tongued or short-tongued bumblebee species visited both plant species during one foraging trip; in that case the stigma of R. minor is not able to touch the sites of R. serotinus pollen on the bodies of the bumblebees, but the reverse may be possible. The inaccessibility of the R. minor stigma resulted in R. minor remaining relatively „pure“. By analyzing the foraging patterns of bumblebees on Rhinanthus during three successive days the significance of two different forms of ethological isolation is considered. About 40% of the observed bumblebees confined their visits to one Rhinanthus species. The long-tongued B. hortorum showed a strong preference for R. serotinus. The behaviour patterns of 60% brought about partial isolation or hybridization. The medium-tongued B. pascuorum was responsible for partial isolation (isolation of R. minor). The short-tongued species B. pratorum, B. terrestris and B. lapidarius were „good“ hybridizers. To support the idea that introgression into R. serotinus was likely, some other factors are discussed, e.g. the attractiveness of R. serotinus, and the fact that bumblebees are more likely to alternate between R. serotinus and the hybrid forms.
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