Everything they told you is Wrong: More is Less!

Okay so let me explain. Don’t go out just yet wearing all of your jewelry and leopard print clothing, or go out buying every piece of Apple hardware you can find! Maybe less is more is still applicable to most situations (I mean, do I really need an iPad Mini and an iPad Air?) What I’m referring to is the really interesting interplay between species richness and species diversity.

So if you’re anything like me, and you were asked what had higher species diversity, you would probably scuffle and think in your head, “Well obviously the community with a higher number of species (otherwise known as a higher species richness.)” Well, as it turns out, that’s not always the case. Hence the “more (can) be less.” The really interesting part is that just because you see more species in a community doesn’t mean that the community is more diverse! Species diversity is not only dependent on species number, but also the proportion of each species. The more even the proportions of all the species you find, the more diverse the community is.

So now it’s your turn! In the pictures below which community do you think is more diverse?

Species Diagram

If you guessed A then I take full credit for my wonderful teaching skills. If not, don’t worry! Although you were probably right in thinking that B has more species, the proportion of species in this community is quite uneven. We have one dominating mussel species. If you look at A, we may have less species, but each species makes up exactly one quarter of the community. This makes it even and diverse. Now full disclosure, if you were to add a couple more species to community B the diversity would probably catch up to community A. I think the cool part is that in an ecological community, we couldn’t simply say that because we see more species it’s more diverse.

And if you’re wondering, this does have practical implications! Last week, our class made its way down to the very official sounding Coal Harbour and Jericho Royal Vancouver Yacht Clubs. There, as the loyal patrons looked at us with a glint of amusement, we all hung over the edge of the docks counting the number of species we observed.

Here's just a sample of what we found: although it looks like there were only mussels, we also saw tunicate colonies, hydroids, sponges, anemones, and more!

Here’s just a sample of what we found: although it looks like there were only mussels, we also saw tunicate colonies, hydroids, sponges, anemones, and more!

What we saw was that the Coal Harbour marina had more species than Jericho! But based on what we learned, we couldn’t assume that this observation meant that Coal Harbour was more diverse than Jericho, just that it housed more species!

So anyway, the next time you guys go somewhere cool, try it for yourself! Take a minute to count the number of individuals of each species. Then go here to learn how to calculate the diversity! If you want to learn about the importance of preserving biodiversity and the impact that humans are having on it click here and here.

Until next time, keep science-ing on!


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