Nothing in Biology Makes Sense: Chipmunks have no respect for species boundaries

A yellow pine chipmunk, Tamias amoenus. Photo by Noah Reid, via Nothing in Biology Makes Sense.

At Nothing in Biology Makes Sens, Sarah Hird explains some of her own research, recently published at the journal Heredity, which documented just how “leaky” species boundaries can be in the chipmunks of western North America.

While doing a comparative phylogeography study, the Sullivan lab discovered that one particular subspecies, T. a. canicaudus, had a mitochondrial genome that was most closely related to the red-tailed chipmunk (T. ruficaudus), instead of the other yellow-pine subspecies. Additional data show that the T. a. canicaudus nuclear genome is in fact most similar to other yellow-pines – it’s just that the mitochondria is of red-tailed origin.

For all the sordid phylogenetic details, go read the whole post, and check out the original paper.◼

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Nothing in Biology Makes Sense: Making sense of the missing human baculum

Walruses on the corner If you think those tusks are impressive, you ain’t seen nothing yet. Photo by Joe King.

Over at Nothing in Biology Makes Sense! Sarah Hird discovers a case in which Creationists are willing to cite phylogenetic context to make a point, and that point is that God made Eve from the bone in Adam’s penis. What, you didn’t know that most mammals have a penis bone?

Baculum is the technical term for the penis bone. Many mammals have one – presumably to aid in sexual intercourse. For mammals that mate infrequently, prolonged intercourse ups the chances that a particular male sires some babies. For mammals that must mate quickly, the baculum provides immediate rigidity. And for all mammals, keeping the urethra straight while copulating is imperative, so maybe it’s there to prevent a kink in the works, so to speak.

To see the full phylogenetic context of the baculum, and learn some possible reasons why a male walrus has a two-footer but humans have none at all, go read the whole thing.◼

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The Molecular Ecologist: Climate’s a-changin’. Will the living world evolve to cope?

Warm Fire It’s getting hot out there. Photo by Kaibab National Forest.

Over at The Molecular Ecologist, I discuss a new study that uses phylogenetic estimates for 17 families of vertebrates to estimate how rapidly those animals have evolved in response to past climate change, and compares those estimates to how fast they’ll need to evolve to keep up with projected climate change. Spoiler alert: past rates of adaptation to climate aren’t anywhere near fast enough.

To keep up with projected climate change, Quintero and Wiens estimated that the species in their dataset would have to undergo adaptive change at from 10,000 to 100,000 times faster than the rates estimated in their evolutionary past.

Well, but maybe. To learn whether the data are telling us what the study’s authors say they’re telling us, go read the whole thing.◼

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Nothing in Biology Makes Sense: Tuning the molecular clock

Clock Photo by Earls37a.

Over at Nothing in Biology Makes Sense!, guest poster Gustavo Bravo explains why evolutionary biologists spend a lot of time thinking about how frequently DNA mutations occur.

There are two ways in which we can translate the number of substitutions between a pair of lineages into absolute dates. First, we can calibrate the clock against absolute times resulting from independent evidence such as fossil or geological dates. And secondly, we can measure directly the rate of mutation by comparing DNA or protein sequence data in present day organisms. Because the fossil record for some groups is incomplete and the dating of geological events remains controversial, some of those clocks are likely to produce inaccurate estimates of time.

To learn how re-setting the “molecular clock” has changed our thinking about human evolution, go read the whole thing.◼

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