Research press release


Nature Communications

Zoology: Galapagos birds get a taste for flowers



今回、Anna Travesetたちは、ガラパゴス諸島に生息する陸鳥による訪花と花粉の輸送を計測し、観察対象の鳥類種の全てが被子植物と直接に相互作用していることを見いだした。今回の研究の対象となったのは、ガラパゴス諸島で見られる合計23種の鳥類のうち、最も生息数の多い19種の陸鳥類で、100種以上の植物との相互作用が認められた。Travesetたちは、鳥類と花との相互作用のネットワーク特性を大陸部と島嶼部の生態系のネットワーク特性と比較し、ガラパゴス諸島におけるネットワークの方がノード間のつながりが密で、食餌の汎化が進んでいることを示していることを明らかにした。


Almost every species of land bird in the Galapagos Islands has expanded its diet to include nectar and pollen from flowers, finds a new study in Nature Communications. Such a large expansion of a feeding niche has not been reported previously among vertebrates and suggests that birds act as key pollinators across the archipelago.

Isolated oceanic islands like the Galapagos typically harbour a much lower diversity of plant and insect species than mainland areas, since dispersal over large expanses of water is often unsuccessful. In contrast, bird species may be able to reach these areas but face a limited range of insect and plant food when they arrive. As a result, species may broaden their diets to include floral resources, although the extent to which this occurs across island archipelagos is not known.

Anna Traveset and colleagues measure flower visits and pollen transport by Galapagos land birds and find that every species they observed interacted directly with flowering plants. This represents the 19 most abundant land birds out of the total 23 species found in the islands, who together interact with more than 100 different species of plants. Comparing the network characteristics of bird-flower interactions with those from other mainland and island ecosystems, they find that the Galapagos network is more highly connected, indicating a greater degree of diet generalisation.

This generalisation means that birds do not discriminate between interacting with native or invasive plant species, suggesting that although feeding niche expansion may have aided the birds’ initial survival on these islands, it may also be playing an unwanted role in the pollination of invasive plants.

doi: 10.1038/ncomms7376

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