Eucalypts are unattractive to frogs

(writing in progress)

Both eucalypts1 and Australasian treefrogs2 have radiated into hundreds of species in Australia and New Guinea. These are parallel processes in terms of evolutionary history but the two genera (Eucalyptus and Litoria) have no particular relationship to each other because eucalypts tend to be associated with well-drained, drought-prone lands whereas Australasian treefrogs tend to be associated with well-watered environments.

 
Although this has never been remarked in the literature, a noteworthy aspect of Australian ecology is the failure of any species of Australasian treefrog to forage in the crown of any eucalypt, particularly on insects attracted to the blossoms.

Although no climbing frog penetrates the eucalypt-dominated Great Western Woodland of Western Australia, much of the vegetation dominated by eucalypts elsewhere in Australia – whether forest, woodland or mallee – does contain at least one climbing species of the genus Litoria.

Furthermore, the hollow branches of eucalypt trees are occupied during the daytime by several species3 of Australasian treefrogs, spanning latitudes from the temperate zone to the tropics. The reason for the inadvertent exclusion of tree frogs from eucalypt foliage is the sensitivity of thin-skinned amphibians to the volatile hydrocarbons produced by eucalypt leaves.

What emerges is that Australasian treefrogs have radiated evolutionarily – to a degree unrivalled by any other genus of frogs on Earth – despite the evolutionary radiation of eucalypts on the same landmasses.”

(I don’t think this topic makes the grade in its present form. Should we rather harp on the fact that Litoria caerulea is the only tree frog on Earth that uses sound amplification by natural tree hollows) Yes, I agree that that would add an interesting angle; could we go with both topics? The angle could be that it is surprising that Eucalypts are not used by tree climbing frogs as a place of forage, but at least one species has occupied a very interesting niche – the large hollows which they use as boom boxes. It is perhaps a good example of ‘nature abhors a vacuum’ :)? I say that only half-joking. Here is a case of a niche that was seized by the frog. Nature is arguably ‘all-knowing’ in that it sees and uses all niches.

1 Myrtaceae: Eucalyptus

2 Pelodryadidae: Litoria

3 e.g. Litoria caerulea, L. peronii and L. gracilenta

(writing in progress)

Posted on June 14, 2022 05:16 AM by milewski