The scale on the plot shows the values of the standardized variables, but this is undocumented and is therefore quite confusing for users (as I've heard).
That is, the scale shows the values of: (trait - mean)/standard deviation. This is done in the code here. The values printed on the left and right side of the axis are the min and max of the standardized trait, which are: (min and max of the original values - mean)/sd. The place where the bars start corresponds to the mean of the original trait values (and corresponds to 0 for the standardized values).
This is all useful for visually highlighting the species with low / average / high values, but should be documented.
The scale on the plot shows the values of the standardized variables, but this is undocumented and is therefore quite confusing for users (as I've heard).
That is, the scale shows the values of: (trait - mean)/standard deviation. This is done in the code here. The values printed on the left and right side of the axis are the min and max of the standardized trait, which are: (min and max of the original values - mean)/sd. The place where the bars start corresponds to the mean of the original trait values (and corresponds to 0 for the standardized values).
This is all useful for visually highlighting the species with low / average / high values, but should be documented.