Effect of population size on reproductive success and pollinator guild of Comarum palustre (Rosaceae)
(2009) Young Botanists’ Day “Evolution in Botany: from Darwin to women” — Location: Brussels, Belgium (24.November.2009)
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- The great majority of flowering plants in temperate regions depends on insects for efficient pollination and reproductive success, especially Apidae and Syrphidae. Any disturbance in the pollinator guild composition would enhance the vulnerability of the insect pollinated species. Habitat destruction and fragmentation resulting in small and isolated plant populations are major threats to plant-pollinator networks. It has been shown that populations containing a high diversity of plant species as well as high numbers of individuals attract more visitors. Comarum palustre (Rosaceae), a perennial herb growing in highly fragmented bogs in the Ardennes in Belgium, does not depend on specialist pollinators, and might therefore be facilitated by surrounding floral resources by sharing pollinators. We investigated whether the size of C. palustre populations plays a major role in its reproductive success. Flower observations and pollen limitation experiments were conducted in small and large populations of C. palustre, at the end of the flowering season in July 2008 and during the whole flowering season in June 2009. The study sites were based west of Arlon, South Belgium. In July 2008, only Diptera (Syrphidae and Muscidae) were observed in a small population with only nine inflorescences. The following year, the area occupied by C. palustre was much larger (1 241m²) resulting in a greater insect diversity. In total, insects from five orders were recorded (Coleoptera, Diptera, Hymenoptera, Lepidoptera and Mecoptera). Even though the population size had grown compared to the previous year, it was still considered a small population. In large populations, six insect orders visited C. palustre in July 2008 (Coleoptera, Diptera, Heteroptera, Hymenoptera, Lepidoptera and Mecoptera) compared to four in June 2009 (Coleoptera, Diptera, Hymenoptera and Lepidoptera). Bees (Apoidea) were represented almost exclusively by Bombus in small populations in June 2009 while in big populations Bombus, Apis mellifera and other solitary bee species were observed. Out of seven bumble bee species, two were only seen in large populations; both of them cuckoo species (B. campestris & B. sylvestris). Regarding the visitation rate, three times more flowers were visited in large compared to small populations during the same amount of time. Observations showed significant differences between the two flowering seasons and between small and large populations. This could be explained by the fact that both the surrounding vegetation and the size of the populations were different and had evolved. The effect of both population size and surrounding vegetation will be assessed in the next few years.
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Somme, L., Mayer, C., & Jacquemart, A.-L. (2009). Effect of population size on reproductive success and pollinator guild of Comarum palustre (Rosaceae). Young Botanists’ Day “Evolution in Botany: from Darwin to women”, Brussels, Belgium. https://hdl.handle.net/2078.5/200182