Competition
 

Explanations for answers to quiz on damselfishes:

1. Which species is aggressively dominant over the other? The answer is, of course, 3-spots...recall that this species forces the duskies into the less-preferred shallow habitat.

2. Which species has a longer relative gut length? If you have chosen dusky damselfish, you are incorrect, but have inherently good "smarts". In fact, 3-spots have guts almost 3 times longer than those of duskies. There is no obvious explanation for this. The intuitive expectation is that duskies, with their poorer food resources, would have longer relative gut lengths for better processing of less-nutritious foods.

3. Which species has a higher absorption efficiency? This is another tricky question. Once you know that 3-spots have relatively longer guts than duskies, then you will know that they have the higher absorption efficiencies. However, the intuitively obvious answer is duskies, because they feed on nutritionally inferior foods. So, if you get this wrong, it's not for lack of thinking.

4. Which species grows faster? For this question, choice of 3-spot damselfish should have been a good one, because it has a longer relative gut length and higher absorption efficiency. However, growth rates of the 2 species are actually similar. Duskies must compensate by eating more of their poorer foods.

5. Which species defends a larger territory? There is no trick to this question. Dusky damselfishes have to tend and defend larger territories to compensate for the poorer food resources in the shallow reef area.

6. Which species has a higher cost of territorial defense? Based on the answer to # 5, this is straightforward...the larger territories of dusky damselfishes cost more to defend.

 
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