In the lab, you learned about the benthic and limnetic sticklebacks of Paxton La

Question

In the lab, you learned about the benthic and limnetic sticklebacks of Paxton Lake. Benthics are stout-bodied fish with wide mouths that feed on invertebrates in the mud in the shallow margins of the lake. Limnetics are slim-bodied fish with narrow mouths that feed on zooplankton in the center of the lake. Researchers working on the sticklebacks have made the following observations. Limnetic and benthic sticklebacks differ in number of dorsal spines, number of lateral plates and presence of a pelvic girdle. 1-2% of sticklebacks in Paxton Lake are hybrids. Limnetic and benthic sticklebacks build their nests in the same region on the benthic margin of the Paxton Lake. However, benthic males select heavily vegetated areas while limnetic sticklebacks males select bare areas of the lake bottom. Hybrid fish were released in a small lake that lacked a resident stickleback population. 20 years later, they have formed a small, healthy population of sticklebacks in the lake. Limnetic and benthic males differ in courtship behaviors. When given a choice, male and female benthics and limnetics choose to mate with their own kind. Consider the information provided in this case study in addressing the questions below. Does the case study describe sympatric or allopatric speciation? Explain your answer, including a definition of the mode of speciation that you have identified in this case. Do the benthic and limnetic sticklebacks of Paxton Lake represent separate species: According to the biological species concept? According to the morphological species concept? According to the ecological species concept?

Explanation / Answer

Part a: The case study describes sympatric speciation, because the 2 freshwater species live in the same lake and therefore according to thedefinition of sympatric speciation, "sym" meaning the same, and"patric" meaning fatherland, the two species have divergedindependently while living the same range. Sympatricspeciation has been observed. Part b: - According to the biological species concept, they are not thesame species because they prefer to mate with their own kinds inthe wild and therefore they do not generally interbreed and produceoffspring. - According to the morphological species concept, they aredifferent species because they differ in feeding morphology andanti-predator defenses. The limnetic stickleback has long gill rakers and have long dorsaland pelvic spines. Due to the fact that they live in thecenter of the lake they have developed these characteristics toimprove their defense mechanisms. On the other hand, the benthic species lives in the banks of thelake and does not deal with big predators, so therefore it hasdeveloped smaller pelvic and dorsal spines and have short gillrakers. - Ecological species concept suggests that they are differentspecies because they occupy separate niches and have a differentrole in the environment. Please Rate and Comment, hope this helps!

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