Wolf spiders (Schizocosa ocreata) are active leaf-litter predators. Mature male wolf spiders can develop large, conspicuous dark tufts of bristles on their forelegs, which they wave during courtship displays, whereas females are cryptically colored and lack these tufts.
Scientists investigated how a female's prior exposure to avian predator cues affects her subsequent mate choice. They used adult female wolf spiders raised in the laboratory under two different conditions: "predator-exposed" (exposed to avian chemical and visual predator cues during juvenile development) and "predator-naive" (never exposed to predator cues).
They set up a test chamber as shown in the diagram below:
They observed each female for 20 minutes and recorded which male they spent more time facing and remaining near (indicating attraction). They repeated this with 50 predator-exposed females and 50 predator-naive females.
Suggest three possible limitations of this laboratory investigation.
In environments with high avian predation, males with large leg tufts are at a significantly higher risk of being preyed upon, but large leg tufts are also a reliable indicator of high foraging efficiency and overall genetic quality. The scientists found that predator-exposed females preferred males with small leg tufts, while predator-naive females preferred males with large leg tufts.
Suggest and explain the advantage of this flexible mate-choice behavior to the wolf spider population.
Describe how these differences in mate-choice behavior could result in sympatric speciation.
Practise AQA A Level Biology Evolution may lead to speciation (A-level only) with exam-style questions for A Level Biology. 9 questions, matched to the AQA A Level Biology (7402) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
