|Citizen Cane Toad|
What's more, this feature appears to be very common in evolutionary biology when we are dealing with invasive species - it may even be the rule. It's obvious when you think about it - the fastest hoppers are going to be the first to reach a new area, so they'll get busy and colonise it before anyone else comes along. Then at the outer reaches of *that* area, it'll still be populated with the fastest of the fast, so we get a selective pressure at the outer reaches (effectively) for the best hoppers, perhaps at the expense of other adaptations.
Ribbit. Hat tip to Graham.