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Dive Dry with Dr. Bill

#540: Baffling Biodiversity

Well before I traveled to the Philippines, I was aware of the tremendous biodiversity that existed there. I've dived in Asia before and enjoyed the richness of those waters. Back in my ecology class at Harvard we learned that tropical environments tend to have much great range of living things than temperate or polar regions. And, as I've written previously, the Philippines is in a region known as the Golden Triangle which has some of the highest marine biodiversity in the world. Neither our kelp forests nor even the Caribbean can hold a candle to that region.

Before I move on, it might be appropriate to actually define biodiversity. In earlier times biodiversity might be measured simply by the number of species in a given habitat or region. Today we call this "species richness." However, a region could have just a few really common species and lots of rare ones. That would not truly be a diverse ecosystem. Current measures of species diversity take into account the "evenness" of species in a region. If there are many species present, and few of them really dominate numerically, this would be considered a biodiverse region. To this we could add the elements of genetic diversity and ecosystem diversity, but let's not complicate things further at this point.

Polar regions are generally characterized by relatively few species often with very high numbers of each one. Hey, it's hard to live there and I ought to know since I grew up in Chicago and remember the day it hit 81 BELOW zero with the wind chill! Why do you think I choose to stay here in SoCal? The tropics more commonly have a high number of different species with fewer numbers of each, and only a small number of species contain large numbers of individuals. Here in the temperate kelp forests of our region we are somewhere in between.

I'll use species richness to illustrate the difference between our region and that of SE Asia. In Catalina waters we only have five damselfish including our state salt water fish, the garibaldi. That number includes two that are very rare, one of which (the whitetail damsel) has only been seen once in California... right in our dive park. One field guide to the fish of the Philippines region lists 246 damsels in those waters including our old friend Nemo, and it doesn't even cover them all. You may see the scythe butterflyfish at several sites around Catalina, but it is the only member of that family we have. There are some 84 species in the Golden Triangle, and those are only the ones in the guide. We have three wrasses including the sheephead, rock wrasse and senorita while there are at least 292 in the Philippines region.

The high number of species in the tropics means that each one must have some distinguishing feature that allows a scientist to classify it as a distinct species... and its potential mate to identify it from the myriad of related species which often have similar colors and patterns. In addition to that, juveniles, females and males of the same species may look different just as our sheephead and garibaldi do here. In trying to label the species I filmed in the Philippines, I'm confronted with a baffling array of biodiversity! Identifying the species in the less rich Caribbean waters of the Bahamas, Belize and Honduras was child's play compared to this.

My favorite poet, Robinson Jeffers, might refer to this incredible range of colors and patterns as "divinely superfluous beauty." As a marine biologist trying to sort out the critters I've filmed, I'll just call it perplexing, confusing and disorienting. Of course those aren't the technical terms we scientists use in our high falutin' technical papers, but they are very accurate! I just finished editing about 32 hours of video from my trip and now I have to try to identify each species that I can. Gulp. That might take me as long as the editing itself!

Why such high diversity in the tropics? Well, for one thing the "climate" underwater and topside is very easy to take. Who wants to live among icebergs when they can mellow out in toasty tropical waters or bask in the sun in a bikini (well, not me of course, but I do take note of these things)? My minimum water temperatures in Anilao and Puerto Galera were in the mid- to upper-80s. Not any different from the "snow birds" who abandon the cities of the Northeast and Midwest each winter for the sunny beaches of Florida, or for that matter the migratory birds that fly south as the snow approaches.

With such high numbers of related species, it is important that individuals in a given species are able to identify the correct "spouse" to mate with. Imagine the chagrin of a young male black backed butterflyfish when he approaches a female spot-tail butterflyfish thinking she is the girl of his dreams. Both species have the same basic colors and pattern, but the spots on their tales are slightly different. It could get very embarrassing for the young lad, although there may be chemical pheromones unique to each species which give him less mistakable clues. Imagine MY difficulty in distinguishing between the two when I can't tell (er, smell) the difference!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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The beauty and diversity of the Philippines Coral Triangle.

This document maintained by Dr. Bill Bushing.
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