The Wonders of Convergence

One of the most captivating things about evolution is its propensity to produce identical twins on opposite sides of the globe. Species that are near inseparable morphologically, ecologically and behaviorally, but which have very different DNA. They don’t have common forebears, at least not recent ones. Instead, having been buffeted by equivalent forces over the millennia, and run a parallel race of natural selection, they’ve reached the same evolutionary sweet spot. They’ve been sculpted by the same chisel and converged.

The wonders of convergence were bought home to me again this week while working on a paper I’ve been meaning to write for some time. It concerns the phenology of mate-calling among frogs from my home town of Melbourne, in southern Australia (‘phenology’ being the timing and determinants of periodic biological events). In my ramblings through the literature, I came across a great paper by Daniel Saenz and colleagues on the phenology of mate-calling in a community of frogs from eastern Texas. Texas, that’s roughly 14,000 km from Melbourne, on the other side of the world’s greatest ocean. And yet, what Saenz et al. had to say about the frogs they studied sounded very familiar. Oddly familiar.

And so, with Google’s help, I set to work looking up these Texan amphibians. Surprise, surprise, they are the same frogs I work on 14,000 km away. Quite unrelated phylogenetically, but counterparts nonetheless. Take a look for yourself. In the following pairs of photos, the Australian species is on the left and its Texan analogue on the right. It’s incredible, isn’t it?

Whistling Tree Frog, Litoria verreauxii

Whistling Tree Frog, Litoria verreauxii

Western Chorus Frog, Pseudacris triseriata

Western Chorus Frog, Pseudacris triseriata

 

 

 

 

 

 

Growling Grass Frog, Litoria raniformis

Growling Grass Frog, Litoria raniformis

Common Bullfrog, Rana catesbeiana

Common Bullfrog, Lithobates catesbeiana

 

 

 

 

 

 

 

Common Froglet, Crinia signifera

Common Froglet, Crinia signifera

Northern Cricket Frog, Acris crepitans

Northern Cricket Frog, Acris crepitans

 

 

 

 

 

 

Peron's Tree Frog, Litoria peronii

Peron’s Tree Frog, Litoria peronii

Gray Tree Frog, Hyla versicolor

Gray Tree Frog, Hyla versicolor

 

 

 

 

 

 

Sudell's Frog, Neobatrachus sudelii

Sudell’s Frog, Neobatrachus sudelii

Eastern Spadefoot Toad, Scaphiopus holbrookii

Eastern Spadefoot Toad, Scaphiopus holbrookii

 

 

 

 

 

 

Spotted Marsh Frog, Limnodynastes tasmaniensis

Spotted Marsh Frog, Limnodynastes tasmaniensis

Southern Leopard Frog, Rana sphenocephala

Southern Leopard Frog, Lithobates sphenocephala

 

 

 

 

 

 

 

Photo sources (those not listed are my own):

Western Chorus Frog –  calphotos.berkeley.edu, photographer Todd Pierson.
Common Bullfrog – http://www.discoverlife.org/, photographer unknown.
Northern Cricket Frog – https://www.flickr.com/photos/52463647@N08/, photographer Melville Osborne.
Gray Tree Frog – http://www.californiaherps.com/noncal/misc/miscfrogs/pages/h.versicolor.html, photographer Gary Nafis.
Sudell’s Frog – www.stewartmacdonald.com.au, photographer Stuart MacDonald.
Eastern Spadefoot Toad – http://www.discoverlife.org/, photographer Todd Pierson
Spotted Marsh Frog – http://bwvp.ecolinc.vic.edu.au/fieldguide/fauna/spotted-marsh-frog, photographer Craig Cleeland
Southern Leopard Frog – http://www.frogforum.net/, photographer John Clare

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