Welcome, toad overlords

i-9f1b3abfbfab7c7a000e79a7e243844d-canetoad.jpg

In yet another example of evolution in action, investigators have documented morphological changes in the cane toads (Bufo marinus) that infest parts of Australia. They’re an invasive species that was introduced in a misbegotten attempt to control beetles that were damaging the sugar cane crop; as it turns out, they are aggressive predators that eat lots of other native fauna, and they secrete toxins that kill animals that try to eat them.

Another feature that contributes to their unwanted success is their rapid dispersal. Individuals can move up to 1.8km per night, occupying new territory at a distressing pace. In the 70 years since they were introduced, they’ve taken over a million square kilometers of Australia. Since dispersal into virgin territories is a significant advantage for the toads, it was predicted that there would be selection for faster migration rates in the population. The authors have several lines of evidence to show that this is the case.

[Read more…]

Guanlong wucaii

i-3fb07e2ea156651f95030b773f812590-guanlong_skull.jpg
a, b, Cranial reconstruction in left lateral (a; shaded area indicates the unpreserved portion) and dorsal (b) views. adc, anterodorsal concavity; al, anterior lamina; an, angular; aof, antorbital fenestra; d, dentary; dg, dentary groove; emf, external mandibular fenestra; en, external naris; if, infratemporal fenestra; isf, foramen on ischium; j, jugal; jp, pneumatic jugal foramen; l, lacrimal; m, maxilla; mc I–IV, metacarpals I–IV; mo, maxillary opening; mt I–V, metatarsals I–V; mvc, median vertical crest; nc, nasal crest; obf, obturator foramen; orb, orbit; pf, prefrontal; pfe, pneumatic fenestra; pl, posterior lamina; pm, premaxilla; po, postorbital; pr, pneumatic recess; qj, quadratojugal; ri, right ilium; ris, right ischium; rp, right pubis; sa, surangular; sac, sacrum; sc, sagittal crest; sec, semilunate carpal; sq, squamosal; tp, tubercle on pubis; tr, transverse ridge. Scale bar: 5 cm

Well, I was going to put together more about this beautiful new basal tyrannosauroid from the Jurassic of China, Guanlong wucaii, but Carl Zimmer beat me to it. I’ll just show you that lovely crested skull, and below the fold, a picture of the fossil in situ, and let Carl do the hard work of explaining it all.

[Read more…]

Evolution of a polyphenism

Here’s some very cool news: scientists have directly observed the evolution of a complex, polygenic, polyphenic trait by genetic assimilation and accommodation in the laboratory. This is important, because it is simultaneously yet another demonstration of the fact of evolution, and an exploration of mechanisms of evolution—showing that evolution is more sophisticated than changes in the coding sequences of individual genes spreading through a population, but is also a consequence of the accumulation of masked variation, synergistic interactions between different alleles and the environment, and perhaps most importantly, changes in gene regulation.

Unfortunately, it’s also an example of some extremely rarefied terminology that is very precisely used in genetic and developmental labs everywhere, but probably makes most people’s eyes glaze over and wonder what the fuss is all about. I’ll try to give a simple introduction to those peculiar words, and explain why the evolution of a polyphenic pigment pattern in a caterpillar is a fascinating and significant result.

[Read more…]

The real truth about the Sasquatch

As a proud native of the great Pacific Northwest, when an article on one of our noblest creatures was mentioned to me, I had to read it. Here’s the center of the story.

In July 2005, nine residents of Teslin, Yukon,
witnessed through a kitchen window a large bipedal
animal moving through the brush. The next morning, they
collected a tuft of coarse, dark hair and also observed a
footprint measuring 43 cm in length and 11.5 cm in width.

That’s right: physical evidence, a footprint and hair, from…Bigfoot. The Sasquatch. A sample captured in the wild and brought into the lab. Pinned against the wall, trapped and unable to escape the probing appendages of an implacable, intrusive Science.

So they extracted DNA from the hair and amplified conserved mammalian sequences. They sequenced fragments of the DNA and compared them against sequences in the databases, and got a shocking answer. Prepare yourself: here is a diagram of the phylogenetic relationship of Sasquatch to other mammalian species.

i-f917d5dd7868188506e91ce434e810f0-sasquatch_tree.jpg
Maximum parsimony tree illustrating the position of the Sasquatch hair sample. Bootstrap support values are given at the nodes. The species and GenBank accession numbers are water buffalo Bubalus bubalis*, yak Bos mutus, cow Bos taurus, wisent Bos bonasus, and
North American bison Bison bison.

The scientists squirm and try to avoid the obvious conclusions of their results, inventing foolish excuses rather than facing reality.

There are several possible explanations for these
results. First, as suggested from molecular analysis of
hair from a suspected Yeti, the Sasquatch might be a
highly elusive ungulate that exhibits surprising morphological convergence with primates. Alternately, the hair
might have originated from a real bison and be unrelated
to the Sasquatch. Parsimony would favor the second
interpretation, in which case, the identity and taxonomy
of this enigmatic and elusive creature remains a mystery.

I wonder what Radical Sasquatch will think of this.

*Wait a minute…the scientific name for the water buffalo is Bubalus bubalis? Bubalus bubalis? No wonder they’re so mean.

Coltman D, Davis C (2006) Molecular cryptozoology meets the Sasquatch . Trends in Ecology and Evolution 21(2):60-61.