Lessons from Travels: Australian Flowering Trees

by Carl Strang

The focus of this blog is the natural history of northeast Illinois and northwest Indiana. This year’s winter series, which probably will spill into next winter, brings out lessons I have learned about our region during travel experiences in other places. Previous winter series have focused on science and spirituality (The Winter Campfire series, two years ago) and the prehistoric life and geological history of our region (last year’s Prehistoric Life series).

Today’s topic is the startling contrast between reproductive strategies of our trees and those of Australia, one of many lessons I learned in my 5-week vacation Down Under in late 2000. Nearly all of our trees are wind pollinated.

This silver maple is an example.

The flowers are unspectacular, because the trees put their energy into sending out volumes of pollen to drift on the breezes, so that a tiny portion of the grains by chance will land on female flowers of the same species and pollinate them. In Australia, most of the trees have showy flowers.

Flowers of one of the many eucalypt trees that dominate Australia’s woodland floras.

Flowers are showy not to impress us (though we certainly breed plants to enhance floral qualities we like), but rather to attract the attention of animals, which in the process of feeding on nectar and pollen actively carry some of the pollen from plant to plant. In Australia the most conspicuous pollinators are birds.

Here one of the dozens of species of honeyeaters approaches a passion fruit flower in the Alice Springs Desert Park, easily the most creatively interpreted zoo I have ever visited.

Honeyeaters come in a wide range of sizes and colors. The small ones are reminiscent of our wood warblers in their colors, diversity, and small size. Ecologically they are quite different, their tongues equipped with brushes to help them exploit floral resources. They supplement that diet with insects and fruits to different degrees. There also are larger honeyeaters, including the odd looking wattlebirds and friarbirds.

One of the friarbirds, which have patches of bare, pigmented skin around their heads and necks to help release excess heat.

On my second day in Australia I parked my rental car at a roadside rest stop in Tasmania, where a large eucalypt was flowering.

The tree bore an abundance of blooms.

It was noisy with birds drawn to its new flowers.  Not only were there two species of wattlebirds, but also musk lorikeets.

Here is a related parrot, the red-collared lorikeet, likewise interested in flowers of a tree, at Kakadu National Park in the Northern Territory.

The main lesson here was the rich addition to Australia’s avifauna, as well as to the beauty of the trees, made possible by the evolutionary channeling of most of the trees into mutualistic partnerships with the birds. Our trees succeed instead by the more independent means of wind pollination. There probably is more than one underlying factor influencing this difference. The greater diversity of trees in tropical areas, possibly extending throughout Australia’s relatively mild climate zone, means the individual trees of each species are fewer, and more widely scattered, reducing the effectiveness of wind pollination and increasing the need for animal vectors. The mild climate also makes it easier for diverse animal pollinators to remain in an area throughout the year. Most of our wind-pollinated trees bloom in early spring, before the trees leaf out, when wind is able to move through their canopies better and carry pollen from plant to plant more effectively.

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4 Comments

  1. Sam Droege said,

    November 1, 2011 at 7:34 am

    Hi Carl:

    Lovely blog post, as usual. Just a slight clarification. Red Maples actually employ a mixed strategy. They do wind pollination, but also have nectar and a complement of syrphid flys and very early bees (Andrena fenningeri being the most obvious) also help with pollination.

    • natureinquiries said,

      November 2, 2011 at 5:54 am

      Thanks, Sam, that’s interesting. I wonder if that extends to silver maples as well (we don’t have red maples in my county). Looking back at the picture it would account for the red pigmentation in the flowers. Something with a less colorful, catkin-like male flower, say an oak or willow, might be a better illustration of my point. Regards, Carl

  2. November 5, 2011 at 8:03 pm

    Hello Carl
    Thanks for the kind comments about the Alice Springs Desert Park! In fact, we are more a biopark than we are a zoo. We work hard to describe the inter-relationships between plants, animals and people. That is after all how most of us see the world. Not surprisingly, the use of stories as a major plank in our interpretation proves irresistible to many people.
    I hope you enjoyed your visit.
    Gary Fry
    Director, Alice Springs Desert Park

    • natureinquiries said,

      November 7, 2011 at 7:00 am

      Thanks, Gary,
      I enjoyed it very much. At some point I will elaborate on my visit to your park, including the most amazing raptor presentation that illustrates your point.
      Regards, Carl


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