Step 1: Understanding the Question:
The question asks for the average genetic relatedness between two randomly selected female offspring in a haplodiploid ant colony where the queen mated with three unrelated males.
Step 2: Key Formula or Approach:
In haplodiploid species, females are diploid (receive $50\%$ of their genome from the mother and $50\%$ from the father), while males are haploid (receive $100\%$ of their genome from the mother's unfertilized egg).
The genetic relatedness ($r$) between two female offspring can be calculated based on whether they share the same father (full sisters) or different fathers (half sisters).
Step 2: Detailed Explanation:
• Since the queen mates with three different unrelated males, and uses their sperm equally, any two randomly selected female offspring have a certain probability of being full sisters (sharing the same father) or half sisters (having different fathers).
• The probability that two randomly selected females share the same father is:
\[ P(\text{same father}) = 3 \times \left(\frac{1}{3} \times \frac{1}{3}\right) = \frac{1}{3} \]
• The probability that they have different fathers is:
\[ P(\text{different fathers}) = 1 - P(\text{same father}) = 1 - \frac{1}{3} = \frac{2}{3} \]
• Let us calculate the genetic relatedness ($r$) in both scenarios:
1. If they are full sisters (same father):
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• They share $50\%$ of their genes from the mother (relatedness via mother = $0.25$).
• Since the father is haploid, he passes $100\%$ of his genes to all of his daughters. Thus, they share $100\%$ of their paternal genes (relatedness via father = $0.5$).
• Therefore, the relatedness between full sisters is:
\[ r_{\text{full}} = 0.25 + 0.5 = 0.75 \]
2. If they are half sisters (different fathers):
• They share $50\%$ of their genes from the mother (relatedness via mother = $0.25$).
• Since their fathers are different and unrelated, they share $0\%$ of their paternal genes (relatedness via father = $0$).
• Therefore, the relatedness between half sisters is:
\[ r_{\text{half}} = 0.25 + 0 = 0.25 \]
The average genetic relatedness ($r$) is the weighted average of these two scenarios:
\[ r = P(\text{same father}) \times r_{\text{full}} + P(\text{different fathers}) \times r_{\text{half}} \]
\[ r = \left(\frac{1}{3} \times 0.75\right) + \left(\frac{2}{3} \times 0.25\right) \]
\[ r = 0.25 + \frac{0.5}{3} = 0.25 + 0.1667 \approx 0.417 \]
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Step 3: Final Answer:
Therefore, the average genetic relatedness between two randomly selected female offspring in this colony is 0.417.