Birds and passion, Ecuador rules in biodiversity

By Dave Armstrong - 01 Oct 2014 9:15:0 GMT
Birds and passion, Ecuador rules in biodiversity

The Yanacocha Reserve in Ecuador is the place to be seen, if you’re a sword-billed humming bird. Wonder how he cleans his feathers without impaling himself? Sword-bill image; Credit: © Shutterstock

Ecology is the study of interrelationships. While we concentrate on focus species and children’s icons, the underlying feeling is generally that it’s the bacteria and fungi that do all the work. The rest of us simply live off the fat of the other species we ingest. Real ecology emerges in this passion flower, bat and humming bird study. Interesting evolution adds to the mix, while we conclude with other ideas on pointless deforestation.

Passiflora mixta is the major example of the species of Andean passion flowers, modified in this case over the last 10.7 million years for specialised pollination by the sword-billed humming bird, The bird’s record of this coevolution dates to 11.6 mya. While the flowers’ nectar tubes are 6-14cm long, the record-breaking bill of Ensifera is up to 11cm. The nearest living relative of the sword bill is a short-billed humming bird, Pterophanes cyanopterus. Adding to this the red flower is self-incompatible, meaning it really needs the cross-pollination provided by this unique humming bird. Interestingly, even mountain building tectonics play a part, as the Northern Andes rose up much higher around 9 mya, indicating the plant and the bird needed to adapt to climate change at that time too.

Distribution records are the key to a study by S. Abrahamczyk, D. Souto-Vilaro´s and S. S. Renner from the Universities of Bonn and Munich. Incorporated with phylogenetic studies, they have produced a stylish proof of a unique ecological situation. They even have evidence from molecular clock models that the plant managed to break away from dependence by using other “hummers” and bats. The isolated species distribution at the present time shows that it now relies exclusively on the fairly common, but localised Ensifera ensifera The full paper is in Proc.Roy.Soc.B under the title, Escape from extreme specialization,passionflowers, bats and the sword-billed hummingbird.

The reversibility of the mutual dependence indicates that evolutionary dead-ends can be avoided. Other plants such as Aquilegia or ,em>Penstemon have shifted between hawk moth, humming bird and bee pollination. However this case study is probably the most extreme with heavy investment by both protagonists in long nectar tubes and a unique bill longer than the bird’s body. There are 7 species in the Passiflora group(clade) to which P.mixta belongs, are all adapted to humming bird pollination. In all 37 species can be pollinated by the sword bill, out of a large number making up around 500 South American species. Bats pollinate only 7 green/white flowered species.

The distribution maps tell the real story. Northern Ensifera bills are longer to match slightly longer Passiflora flower parts. Shorter nectar tubes in the south match the Ensifera there. The transfer of the stamen’s pollen to the stigma by the lengthy tongue of the bird is critical to the survival of these plants, it seems. Sword bills are called “trap-liners” as they revisit the plants while the 5 day flowers last.

The cloud forests of Ecuador have a lot to reveal to us. This is simply a huge example of one of many stories the biodiversity has for us. With the possibilities of scientific advance on many fronts, it is remarkable that all we ever seem to do is destroy these precious places in exchange for outdated fossil fuels. Deforestation is noted here to reduce the number of plants available for sword bills and the fruit set of the passion flower. Both species suffer, but not as much as the human prospect. Depending on one source of energy is unrealistic for these birds, while the plants lose their coevolved partner and have lost 4 species locally. As for the humans ---- simply have a look at the Ecuadorian Chocó rainforest habitat of the umbrella bird. Maria Gonzalez could tell you a lot about that in Whitley Wonders.