Tag Archives: diversity

The Common Era: A Pet Peeve

The problem with being the type of person who regularly reads and talks about events that happened a really long time ago is that you develop pet peeves. Like mine about the terms BCE and CE.

BCE (Before the Common Era) and CE (Common Era) are touted as the politically correct alternative to BC (Before Christ) and AD (Anno Domini [Year of Our Lord]). Which is great! By all means, let’s have a common era.

But the problem with the BCE/CE system is that it isn’t any broader than BC/AD. Year 0 is the same. Taking one group’s system and changing some letters doesn’t make an unbiased system, it makes nice wallpaper. If you really want to create a common era, pick a year at random and make that Year 0.

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My, What Long Data You Have!

Isle Royale, looking lovely. Photo by the National Parks Service via Wikimedia Commons. Creative Commons info.

Isle Royale, looking lovely. Photo by the National Park Service via Wikimedia Commons. Public domain.

One of the challenges of ecology is that its data take time to exist. If you want to study the offspring of some yeast cells you poked somehow, just take a long lunch break and they’ll be waiting for you in about 80 minutes. Go away for a full day and you’ll come back to the 18th generation of baby yeast cells. (That’s not to say yeast studies are easy, their time investments just come in different forms.) If you want to look over the same number of generations of a larger, longer-lived mammal, you need a longer data history.

So imagine if you had 55 years of data about wolves and moose on a small island. And now imagine if the wolf population was in trouble–small and inbred. Would you sit by and let the wolves die out, or would you try to throw them a life vest? And in either case, how does the value of your data change?

Those are some of the questions being asked on Isle Royale, a small island 15 miles into Lake Superior. But they’re also being asked of you.

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The Food Chain of Evidence

Ask me about trophic cascades! Photo by Mike Baird via Wikimedia Commons. Creative Commons info.

Ask me about trophic cascades! Photo by Mike Baird via Wikimedia Commons. Creative Commons info.

In the 1960s, a guy named Bob Paine picked a small stretch of rocky beach in Washington state and evicted its sea stars, crowbarring them off the rocks and throwing them back into the ocean. Within a year, the beach’s demographics had changed dramatically: barnacles and then mussels replaced algae and limpets. Species richness, or the number of different species present, hadn’t gone down by the number of sea stars–it had halved.

Paine realized the reason behind the shift was that without the sea stars around to eat barnacles and mussels, their populations skyrocketed, and their demand for algae and limpets increased, causing those populations to crash. He called the three-step chain a “trophic cascade”; the sea stars at the top that shaped the chain he called an “apex predator.”

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It Takes Toucans for These Trees to Tango (Well)

Green-billed toucan (Ramphastos dicolorus), by Cláudio Dias Timm  via the Encyclopedia of Life.

Green-billed toucan (Ramphastos dicolorus), by Cláudio Dias Timm via the Encyclopedia of Life. Creative Commons info.

I’m fascinated by the relationships between species, particularly when you bring evolution into the picture. So I was pleased to meet a collection of birds like this charmer living along the southern coast of Brazil, courtesy of a recent Science article and its resulting coverage, and I wanted to share the acquaintance with all of you.

But first, let’s take a step back, this being lunch time, to…fruit!

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On Population Genetics

So, why do I get so excited about non-invasive methods of collecting genetic samples? Because they can tell you a ton.

Florida panther, Rodney Cammauf/National Park Service

Florida panthers are a poster child for the risks of low genetic diversity. Photo by Rodney Cammauf/National Park Service

You’re probably used to thinking about genetics in terms of an individual–perhaps genetic tests for susceptibility to certain diseases, the potential for gene therapy, or of course as a convenient scapegoat for one’s height (or lack thereof).

But genetics also happen at the level of a population, of course. If you’ve ever taken a biology class, “population genetics” may give you hazy flashbacks to some guys named Hardy and Weinberg and their equilibrium, which is nice and all except for the bit where you have to assume several things that don’t really happen in real life ever (large populations with only two “flavors” of a gene that has no effect on reproductive success and can’t mutate). Where’s the fun in that?

But there are real reasons to care about a population’s genetics, and if you can get enough data from, say, a scat survey, you can look at some interesting questions, particularly if you’re thinking with species conservation in mind.

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