The results

The overall difference in vertebral number between inland and coastal populations can be summarized as:

$$\begin{eqnarray*} \mbox{body}_{\mbox{inland}} - \mbox{body}_{\mbox{coastal}} &=&... ...ox{tail}_{\mbox{inland}} - \mbox{tail}_{\mbox{coastal}} &=& 9.69 \end{eqnarray*}$$

Given the estimate of $\bf G$ already obtained, this corresponds to a cumulative selection gradient between inland and coastal populations of

$$\begin{eqnarray*} \beta_{\mbox{body}} &=& 0.414 \\ \beta_{\mbox{tail}} &=& 0.134 \end{eqnarray*}$$

Applying the same technique to looking at the differences between populations within the inland site and within the coastal site we find cumulative selection gradients of

$$\begin{eqnarray*} \beta_{\mbox{body}} &=& 0.035 \\ \beta_{\mbox{tail}} &=& 0.038 \end{eqnarray*}$$

for the coastal site and

$$\begin{eqnarray*} \beta_{\mbox{body}} &=& 0.035 \\ \beta_{\mbox{tail}} &=& -0.004 \end{eqnarray*}$$

for the inland site.