The Pollination Story; part 1, beginnings

I think the story of flower pollination is one of the great narratives of our planet, and I love telling it, though preferably out in the bush surrounded by the flowers and their attendant animals. However that's not very practical for us, so let's make a start here. It's too big and beautiful a story to tell in one sitting and I anticipate it will take at least half a dozen chapters, which will appear from time to time.

The early land plants - whose ancestors came ashore into shallow estuaries and coast lines only some 450 million years, after nearly three billion years of life in the oceans - had no flowers, no seeds. Like their aquatic ancestors they relied on water to permit sperm to swim to eggs. In time dominant groups of plants developed the seed, a wonderful package of fertilised embryo, with food and water to start it out in life, insulated from the drought and cold of the world so that plants could at last spread into the bare inland.

An idea of how the entire world looked until about 360 million years ago, when the evolution
of the seed allowed plants to colonise the forbidding wastelands.
Lava fields, Bartolomé, Galápagos.

A related development was the wrapping of the sperm into its own tough packaging, which we call pollen, and which was cast to the winds. It's a hideously inefficient system - the chance of a pollen grain landing on the female receptacle of the right species at the right time is minuscule, and only a fraction of a fraction of  a percent of pollen produced forms a seed. As a result, vast quantities of pollen must be produced. Nonetheless, it works and conifers and cycads - the great dynasties of pre-flowering seed plants - dominated the world for some 250 million years. Indeed in vast areas of high altitudes and high latitudes where conditions are too harsh for animal pollinators, they still do dominate.

Black Cypress Pine Callitris enlicheri, Family Cupressaceae, Cooma, New South Wales.
Female (large woody) and male (small and pale brown) cones.

However, some 130 million years ago in China, according to the fossil record (longer ago, and perhaps in western Gondwana, according to some genetic evidence), plants took the next Great Leap Forward.

Archaefructus liaoningensis, one of the oldest known flowering plant fossils.
Courtesy Wiki Commons.

Pollen is high in protein, and doubtless early beetles - ancient insects - blundered around collecting some to eat, and in the process accidentally transferred some to other plants. And here was an evolutionary opportunity - if the plant could persuade the beetle to selectively take pollen to another of its species, it would be a massive advantage. It would be like addressing an envelope to a destination rather than dropping millions of identical letters from an aeroplane in the hope that one or two fluttered to the right doorstep, as the conifers were doing. 

Beetle on Xanthorrhoea flower spike.
The early beetles weren't the ideal carriers, relatively clumsy, hard-shelled and (it has been
unkindly suggested) not all that bright!

For effective pollination, plants need pollen-carriers which could visit relatively distant populations of the same plant species. The arrival of more mobile insect groups such as flies, bees and wasps, moths and butterflies, and even more modern beetles, with better sensory apparatus than the early beetles, provided an immense opportunity and, for most of the past 100 million years, the evolution of flowering plants and insects has proceeded as an inextricable partnership.

Native Bee on Xerochrysum sp., National Botanic Gardens, Canberra.
The underside of the body, especially the thorax, is covered with yellow pollen,
sticking to the hairs.

Fly, family Acroceridae (thanks Susan!), on Xerochrysum sp., National Botanic Gardens, Canberra.
Pollen can be seen adhering to the legs.

See-through butterfly on daisy, Milpe Reserve, north-west of Quito, Ecuador.

In particular, butterfly proboscises are known from 190 million year old fossils - much older than the oldest known flowers - presumably originally for taking up water and resin, but they were pre-adapted for nectar and as the flowering plants exploded in diversity across the world, so did the butterflies and moths.

Male Australian Yellow Admiral Vanessa itea on Xerochrysum sp., National Botanic Gardens, Canberra. Note coiled proboscis.

Pollen wasn't a great reason for insects to visit flowers, from the point of view of either party. It comprises complex proteins and isn't easy to digest, and of course the last thing the plant 'wants' is to have its pollen eaten. (I'm talking here in evolutionary terms, not really being anthropomorphic!) Further, the worst result of all would be having the insect carrier deliver the precious pollen uselessly to the wrong flower, ie of another species.

So two problems needed to be solved by the evolving plants. The insect had to be given another reason than pollen to visit, and the flower had to be visible, and recognisably different from the competition.

The first was solved by the development of a special gland called a nectary in the base of the flower, which produced a simple sugar solution, nectar - an energy source in other words, which was a great prize for any animal. Its sole purpose was to bribe the insects to visit. The second was by an increasingly complex system of 'flags', based initially on leaves, which we now know better as petals and sepals. And the pollinators, the early flies, bees, wasps, butterflies, moths and flower beetles, were quite capable of recognising and remembering these flag messages.

A mighty and earth-changing partnership was established.

Hoverfly, Syrphidae, on Bulbine bulbosa, Asphodeliaceae, Canberra.
As it accesses the energy treat in the nectary, it is encountering the pollen
on the fluffy anthers and the waiting club-like female stigmas.

Later, another and more distantly effective signal was added, to bring potential pollinators within sight of the petals. This was scent, another chemical released to the breezes. Poets have waxed lyrical on flower scents, but as usual they weren't developed for our benefit. The poets shouldn't be too disappointed at this realisation however - if blowflies were better pollinators, more flowers would smell of rotting meat rather than of roses!

Wilga Geijera parvifolia, Rutaceae, western New South Wales.
This rather lovely spreading tree of inland Australia, is one which does
attract blowflies to its somewhat putrid-smelling flowers.
(Ironically it is in the same family as famously sweet-smellers such as oranges and boronias!)

In the next episode, in a week or so, I want to explore how flowers and inflorescences (the arrangement of flowers on a stem) became more and more complex and specialised.

MEANTIME, BACK ON SUNDAY FOR AN ANNIVERSARY OF SOMEONE WHO IS A BIT OF A HERO OF MINE

Preening; how birds stay beautiful - and alive...

Feathers to a bird are, if not the Meaning of Life, then the necessity of it. They insulate (this was their original purpose), they disguise from enemies or display to their rivals and intended mates, and of course they enable flight, one of evolution's most difficult challenges. (It has only arisen on four occasions in all the vast history of life - in birds, bats, insects and pteranodons, just once in each case - compared to some 40 separate times for the compound eye, oft cited as the most unlikely result of evolution.) If they are not operating at optimal efficiency, the bird may well die from heat loss, or fail to catch dinner or succeed in becoming someone else's, or be insufficiently attractive to a mate, in itself a form of death.

Blue-faced Honeyeater Entomyzon cyanotis preening, Griffith, New South Wales.

So care of feathers is critical to life itself, and a considerable portion of a bird's day is devoted to preening to achieve this. It is often closely associated with bathing, either in water or dust, but we've discussed that before and we'll focus on the direct preening today. Each feather - and there may be tens of thousands of them in larger birds or cold climate ones - must be individually 'combed' with the bill (or sometimes the foot), so that each tiny barbule 'zips' properly with the adjacent one and the whole feather must perfectly align with its neighbours. Dirt and parasites must be removed - a single bird may be carrying a dozen species of feather-eating lice, each restricted to that bird species, and each restricted to a single part of the bird's body!

Yellow-billed Spoonbill Platalea flavipes, Canberra, carefully 'combing' a single wing feather.

Key to most preening is a waxy oil produced by the uropygial gland at the base of the tail. It is collected on the bill and wiped into the feathers - understandably this is particularly significant to waterbirds, though most other groups also utilise them. The birds in the following photos appear to be accessing the gland prior to applying the oil.

Male Australian Darter Anhinga novaehollandiae, Canberra.

In close up, the gland is visible at the bill tip.

Kelp Geese Chloephaga hybrida, Puñihuil, Isla de Chiloé, Chile.
They are strongly dimorphic; the male is the white one, recharging with oil.

Marabou Stork Leptoptilos crumeniferus, at dawn, Jinja, Uganda.

Australian Pelican Pelicanus conspicillatus, Nowra, New South Wales.

Other bird groups, notably ratites (the flightless giants of the southern continents), pigeons, parrots and woodpeckers, don't have the valuable gland and many of these rely on powder down, obtained from special feathers which, unlike all others, grow perpetually and are not moulted and regrown each year. They are scattered amongst 'normal' feathers (or in herons for instance, are concentrated into a couple of patches) and their tips readily disintegrate into powdery talc-like keratin which scatters through and 'reinforces' the other feathers.

Mealy Parrots Amazona farinosa, Blanquillo Clay Lick, Peruvian Amazonia.
The 'mealy' name, meaning 'floury', is due to plentiful powder down.

Both the Spinifex Pigeons Geophaps plumifera, Alice Springs, central Australia (above)
and the Red and Green Macaws Ara chloropterus, Blanquillo (below)
are using powder down to preen.

 

Some parts just can't be reached with a bill (especially the head) and feet must be used to comb out the feathers, though presumably it can't be as effective.

White-necked Heron Ardea pacifica, Grenfell, New South Wales.

Golden-headed Cisticola Cisticola exilis, Canberra.

Olive-backed Oriole Oriolus sagittatus, Nowra, New South Wales.

Additionally, mutual grooming - 'allo-preening' - can also help to reinforce pair bonds, as well as getting the job done.

Apostlebirds Struthidea cinerea, Cobar, New South Wales.
One of the most sociable birds in the world, the behaviour here reinforces bonds for the whole group.

Major Mitchell Cockatoo Lophochroa leadbeateri, MacDonnell Ranges, central Australia.

African Silverbills Lonchura cantans, Waza National Park, northern Cameroon.

Finally, let's just enjoy a few more birds at their daily maintenance and repair sessions - it's late Friday afternoon of a busy week here...

Brolgas Grus rubicunda, Rockhampton, Queensland.

Brown Pelican Pelecanus occidentalis, Puerto Ayora, Galápagos.

 

Flightless Cormorant Phalacrocorax harrisi, Fernandina, Galápagos.

Great Crested Grebe Podiceps cristatus, Lake Alexandrina, South Australia.

Little Raven Corvus mellori, Kosciuszko National Park, New South Wales.

Mistletoebird Dicaeum hirundinaceum, Goolwa, South Australia.

Australian White Ibis Threskiornis moluccus, Darwin.

Nazca Booby Sula granti, Española, Galápagos.

Superb Fairy-wren Malurus cyaneus, Canberra.

You probably see birds undertaking this task - doubtless mundane, though vital, for them but fascinating for us - more often than you realise. Take time to enjoy the moment next time, knowing what they're up to.

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Stunning Española, a Galápagos jewel; part 2

While the seabirds are the obvious focus of any visit to Española, there is much, much more to enthral us as well. For a start, if you're excited by ocean blowholes (and who isn't?) there's a pretty good one near the Waved Albatross colony.

Blowhole, Española.

The island, like most of the smaller Galápagos isles, is covered by low vegetation, some shrubby, some no higher than herbs.

Carpet Weed Sesuvium edmonstonei, family Aizoaceae, a Galápagos endemic.

Which brings us to a key aspect of the Galápagos which, having never been part of any continental mainland, boasts large numbers of endemic species which have developed in isolation.The most recently arrived of these endemics, at least among the birds, is the conspicuous Galápagos Hawk Buteo galapagoensis, whose ancestor (something very like the modern Swainson's Hawk B. swainsoni) arrived from the mainland only some 300,000 years ago. Their conspicuousness is misleading - there may be only 130 breeding pairs left throughout the archipelago, following loss of prey species to exotic animals. They will eat anything, living or dead, but cannot survive where the Lava Lizards (see below) are absent.

Galápagos Hawk cleaning up Sea Lion placenta on Española beach.

Two of the most evident Galápagos endemic animals on any Galápagos beach are Galápagos Sea Lions and Marine Iguanas; Española is no exception.

Galápagos Sea Lion pups Zalophus wollebaeki; Bahia Gardner on the north shore of Española
supports a major colony.

The Española sub-species of Marine Iguana Amblyrhynchus cristatus venustissimus is regarded as the
most colourful of all; no problem finding plenty to admire!

As everywhere in the archipelago there are the famous 'Darwin's Finches', but the Large Cactus Finch Geospiza conirostris can only be found here and on even more remote Genovesa, and the distant and inaccessible Darwin and Wolf islets.

Large Cactus Finch male, Española.

However, Española goes further than some of the other islands, and boasts its own endemic species, found nowhere else even in the Galápagos. One of these will accompany you on your walks; the Española Mockingbird Mimus macdonaldi derived from the more widespread Galápagos Mockingbird M. parvulus, which in turn seems to have descended from wayward Long-tailed Mockingbirds M. longicaudatus from Ecuador.

Española Mockingbirds, above and next two photos.

Like most Galápagos animals, these mockingbirds have no fear at all of humans!

Then there are two endemic Española reptile species, one of which you will certainly see, the other you'll need some luck for. Lava Lizards Microlophus spp. are members of the Neotropical ground lizard family and are restricted to the Galápagos; however those on Española are not only the largest and most colourful of them all, but are found on no other island.

Española Lava Lizards; female above, male below.

The Galápagos Racers Pseudalsophis spp. are a closely related group of five species (relatively recently recognised) of colubrid (back-fanged) snakes restricted to the islands. They grow to over a metre long, are remarkably swift, as their name suggests, and like other colubrids are mildly venomous. Lava Lizards are an important part of their diet, but they also prey on finches and small iguanas. The Española Racer P. hoodensis (Hood is the English name for Española) is another endemic to this tiny island. We were lucky to come on one in the dunes by Bahia Gardner, made sluggish by the cool of the evening; this was a highlight among many.

Española Racer, Bahia Gardner.

 

So, Española... Most tours and cruises don't go there, but I'd really suggest you look for one that does when you visit the fabulous Galápagos.

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