The three-spine stickleback ( Gasterosteus spp.) are fish that are often found a
ID: 48251 • Letter: T
Question
The three-spine stickleback (Gasterosteus spp.) are fish that are often found as pairs of species in the same lake. In all cases, the two species in a given lake have different patterns of jaw morphology and diet. Individuals found in open water (limnetic form) feed on brine shrimp larvae (Artemia) while individuals found in shallow water near the bottom (benthic form) feed primarily on amphipods. Researchers conducted an experiment where they fed each food type to both benthic and limnetic morphs. The graph below shows the mean intake rate (and standard errors) of food consumption by each species for the two different diets (all P < 0.05):
a) Which species of fish is most efficient at feeding on Amphipods? On Artemia?
b) Are any observed differences statistically significant? How do you know?
c) It has been hypothesized that the evolution of two different species in each lake is due to trade-offs associated with foraging efficiencies on different prey items. Assuming phenotypic plasticity with respect to feeding is low, do the results of this experiment provide evidence for or against this hypothesis? Explain.
d) What sort of speciation event would this represent?
1.0 Benthic fish 0.9 Limnetic 0.7 Hfish 0.6 0.5 1.5 2.0 2.5 3.0 3.5 4.0 Artemia intake rateExplanation / Answer
(a)
According to the graph the Benthic form is most efficient at feeding on Amphipods and the Limnetic form is most efficient at feeding on Artemia.
(b)
Significance level is 0.05
Since P < 0.05 therefore this value reflects population characteristics so the observed differences will be statistically significant.
(c)
The evolution of two different species in each lake is due to trade-offs associated with foraging efficiencies on different prey items. We can use statistical significance for testing our statistical hypothesis. Since, P < 0.05 so we can conclude that the results of the experiment is not due to sampling error but are actually statistically significant so the results of the experiment should be rejected that is it provides evidence against the hypothesis.
(d)
This event would represent Sympatric speciation because the two species are formed from a single ancestral species The three-spine stickleback and become dependent on different diet for survival.
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