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Pollinator on Dryas Octopetala © Simen S. Hjelle

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Pollinators and their importance in the Arctic environment

Globally, most flowering plants reproduce sexually and are pollinated by insects or other animals rather than abiotic pollen vectors such as wind. Plant-pollinator interactions are usually mutualistic, where both sides benefit from the interaction; thus, the plant’s pollen is transferred to a receptor plant, while the pollinator retrieves food in the form of nectar or pollen. In colder regions, bowl-shaped flowers (solar furnaces) may also provide thermal refuges for basking insects, as they are often warmer than the surrounding ambient temperatures.

Forms of reproduction
Sexual reproduction :: Producing a new organism by the combining genetic material from two different parent organisms.
Asexual preproduction :: Producing a new organism by combining genetic material from a singular parent organism.

The importance of pollinating insects in the Arctic is poorly understood (Robinson..). As a consequence of the tight energy budget experience by Arctic plants (section XXXX), dependence on insect-pollination is costly and risky. In addition, the overall pollinator activity and abundance in the Arctic is low, and several arctic regions have few or no representatives of specialist pollinators such as bees or bumblebees (Bombus spp.) (Hodkinson 2013, Coulson et al. 2014). Thus, Arctic plants often use less costly reproduction strategies independent of insect pollinators, like wind-pollination, self-pollination or asexual reproduction (Bierzychudek, 1985; Johnson et al, 2010)(Kevan, 1972, Brochmann, 1993)(ref wind).

Arctic flora has been thought to not depend on insects as pollinators; in addition, the proportion of species adapted to insect-pollination to other those adapted to other strategies decreases with latitude. However, most arctic plants are still adapted to insect pollination. For example, approximately 55% of Svalbard’s vascular flora is adapted to insect-pollination, although most of these can also self-pollinate (e.g. Kevan, 1972, Brochmann, 1993). A large number of genetic studies also suggest a much higher level of outcrossing in the Arctic than expected (e.g. for Gabrielsen et al. 1998; Kjølner et al 2006; Müller et al 2012; Pietiläinen 2013), and the presence of pollinators influence seed set in arctic areas (Kevan 1972; 1973).

Flies and midges (Diptera) are relatively abundant in the Arctic (Hodkinson 2013), where they play an important role of pollinators despite their loser efficiency compared to bees and bumblebees (Mosquin and Martin 1967, Kevan 1972, Totland 1994). While bees and bumblebees prefer blue-purple flowers (ref), flies and midges have a known preference for yellow and white flowers (Pickering & Stock, 2004), leading to larger proportions of white and yellow flowers in some Arctic regions (Kevan 1972; Wilmer) and influencing the colonization process of recently deglaciated areas (see Chapter 4). This follows the results of a recent meta-study, which showed a correlation between the frequency of distribution of blue and purple flowers in the Arctic and the diversity and distribution of bees and bumblebees (Little).

Arctic plants are mainly perennial and not constrained by the need of immediate reproductive success. Thus, inter-annual variations in climate and pollination availability might influence the type of pollination. For example, the flowers of the perennial purple saxifrage (Saxifraga oppositifolia) are attractive to specialist pollinators such as bumble bees, but even in systems where no bumble bees are present, this species show high levels of genetic diversity and clear signs of efficient out-crossing (Müller… Pietiläinen 2013). The female parts of the flower (the stigma) mature first, allowing pollination with pollen from another open flower if insects are available. If cross-pollination does not occur within two to four days, the male flower parts (anthers) lengthen and curve inwards to facilitate self-pollination. However, self-pollination gives fewer and higher rate infertile seeds.

Basking diptera
Photo:
Diptera
Order of insects. Two-winged or so-called true flies.
Pollinators on Arctic flowers around Longyearbyen, Svalbard.
Video: Learning Arctic Biology
Basking diptera
Photo: Simen Hjelle
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