Category Archives: Ecology (scientific)

ODD POLLINATORS

Insects and plants are intimately linked in terms of their ecology and evolution. Insects and vascular plants both first appear in the fossil record around 400 MY ago, at the beginning of the Devonian, as terrestrial ecology changed to allow the colonization of the land.

Then about 20 MY later, the first arboreal plants appear, and insects developed wings (probably from ancestral gills – the same genes are now involved in the development of arthropod gills and insect wings). However, things really went crazy in the middle of the Carboniferous, when seed plants first appeared, and the insects underwent a massive diversification, or “radiation” as paleontologists call it.

In this period, all of the major insect groups appeared, with only one (the Palaeodictyopterida – they looked a bit like dragonflies) disappearing between then and now. Insects even breezed through the end-Permian mass extinctions around 248 MY ago, when around 95% of marine species disappeared, profiting from the changed ecosystem to undergo a further wave of radiation.

By the time the flowering plants (“angiosperms”) appeared around 100 MY ago (flowers are a relatively recent invention), the insects were established as one of the dominant features of the terrestrial ecosystem, and quickly took advantage of the new plant arrivals. Although insects (and their larvae) munch through plants, the relation can also be mutually beneficial, especially with regard to pollination. Flowering plants generally provide a sucrose reward (nectar) for insect visitors, which in turn inadvertently carry off pollen to other plants of the same species, spreading the genes about. This mutually beneficial relation is shown by the parallel radiation of angiosperms and lepidopterans (butterflies and moths).

Darwin famously predicted that the comet orchid, which has an amazingly long “nectar spur” (the structure holding the nectar – it can be over 30cm long), must be pollinated by an insect with an equally long proboscis. He was right – it turned out to be the nocturnal hawk moth, with a 35cm long proboscis.

But what happened before there were flowers? Did insects simply eat the gymnosperms and ginkos that covered the Earth, or were they still involved in pollination – and how? Were all plants simply wind-pollinated?

Two recent discoveries give some insight into this. First, back in November, a stunning set of fossils was described in Science, showing in exquisite detail the mouthparts of some Mecopterans – scorpion flies. Nowadays they are a pretty insignificant bunch of around 600 species (and, of course, they are not flies…).


The fossils (and contemporaneous amber specimens) showed long, flexible probosces, and sucky ends that the insects could have used to suck up nectar-like substances produced by gynmosperms. The authors, led by Dong Ren of Capital Normal University, Beijing, conclude:

The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms.

Now another insight into unusual pollinators has come from Reunion Island, down in the south Indian Ocean, next to Mauritius (despite its distance from Europe, Reunion is part of France). Writing in the Annals of Botany, Claire Micheneau describes how she set out to find out how an unusual orchid, Angraecum cadetii (related to Darwin’s star orchid), was pollinated. [See also this BBC page.] They discovered that the animal responsible was an unusual – and unnamed – cricket with unusually long antennae:

These crickets, which are nocturnal foragers, reached flowers by climbing up leaves of the orchid or jumping across from neighbouring plants and probed the most ‘fresh-looking’ flowers on each plant.

They even provide a video, which should be visible below (although perhaps not to readers outside the UK; try here if not):

This is the first time that a cricket has been described as a pollinator, but it gives some indication of the variety of ways that pollination could have taken place even before flowers.  Orthopterans (crickets and grasshoppers) appeared at the same time as the gymnosperms; although people generally assumed the insects would have eaten the plants, the example of the scorpion flies suggests they might also have played a role in pollination.

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Filed under Ecology (scientific), Fossils, Insects

SAVE THE PARROTFISH TO SAVE THE REEFS

November 2007

Parrotfish are major grazers of the algae that grow on coral reefs. Protecting them from over-fishing may be decisive for the survival of reefs in the Caribbean. Sea urchins can also do the trick. That’s the take-home message of a Nature article, most of which consists are rather hard to follow mathematical modelling – ecology is not all (or even at all) about tree hugging! There are some very tough sums involved!

BBC article (includes loadsavideos of parrotfish doing stuff); Nature article (not for the faint-hearted or those without a subscription).

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Filed under Ecology (scientific), Fish, Oceans

FLIES ON A CRAB

September 2007

Essay from Current Biology about the varied lives of flies – including the three species that live in land crabs…

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Filed under Ecology (scientific), Insects

ANTARCTIC BIODIVERSITY

May 2007

Amazing discoveries of fantastic new animals deep in the freezing sea around Antarctica. Described in this article in Nature (subscription needed to get past abstract), and in these pieces from The Independent and the BBC. Pictures here.

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Filed under Ecology (scientific), Fish, Images, Oceans

ARE WHALES LIKE LYNX?

May 2007

Part of the complexity of understanding population cycles is that species can end up too successful, become so numerous that they eat all their food sources, then have a catastrophic collapse, before slowly rebuilding their population size. This is often seen with predators like lynx. Is this what is happening to the Pacific whale? How could we test this hypothesis? BBC summary.

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Filed under Ecology (scientific), Mammals

EXTINCTION AND SPECIATION

March 2007

Interesting article in Science looking at the role of latitude in extinction and speciation. The authors conclude: ” most efforts have aimed at identifying the geological, climatic, and ecological factors that might have elevated tropical speciation rates, our results suggest that both speciation and extinction vary with latitude and contributed importantly to the latitudinal diversity gradient.” You or your institution will need a subscription to get past the abstract.

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Filed under Ecology (scientific), Evolution, Extinction

TOO MANY GOATS IN SNOWDONIA?

November 2006

An article from The Guardian about plans to cull wild goats – which have been there for 10,000 years – to save woodland. And to make way for sheep…

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Filed under Ecology (political), Ecology (scientific), Mammals