Equation 9 · Part 4 · The Peacock Problem: Darwin's Second Theory and Its Hard Tests

Symbol beta_t

\begin{aligned} \Delta \bar{t} &= h_t^{2}\,\beta_t + B\,\beta_p \\ \Delta \bar{p} &= B\,\beta_t + h_p^{2}\,\beta_p \end{aligned}

\beta_t

What this part means

the write.

Its job in the formula

bet $a_t$ is one of the signed contributions combined to compute the quantity on the left.

Full expressionSymbol beta_tArticle meaning

Where the article explains it

Let $\bar t$ be the population mean of a male display trait and $\bar p$ the population mean of the corresponding female preference; write $\beta_t$ and $\beta_p$ for the direct selection gradients acting on each (natural selection pulling $\beta_t$ downward, since the ornament is costly), $h_t^2$ and $h_p^2$ for their heritabilities, and B for the genetic covariance that non-random mating builds between the two traits.

The passage around this formula

…of a population” [ 4 ] . One compact way to see why sits in the coupling itself. Let $\bar t$ be the population mean of a male display trait and $\bar p$ the population mean of the corresponding female preference; write $\beta_t$ and $\beta_p$ for the direct selection gradients acting on each (natural selection pulling $\beta_t$ downward, since the ornament is costly), $h_t^2$ and $h_p^2$ for their heritabilities, and B for the genetic covariance that non-random mating builds between the two traits. The standard…

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Sources cited in the surrounding passage

[4] Models of speciation by sexual selection on polygenic traits ↗

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