Host race radiation in the soapberry bug: natural history with the history

Abstract

In this century, populations of Jadera haematoloma (Hemiptera: Rhopalidae) have colonized three plant species introduced to North America. Each new host differs in fruit size from the native hosts, providing an unplanned experiment in natural selection of the insect's beak length. In each of three host shifts, beak length has increased or decreased in the direction predicted from fruit size. Museum specimens show historical changes consistent with the host shift scenario inferred from beak length values in contemporary populations. The extent to which beak length evolution has been accompanied by evolution in other body size characters differs between races, suggesting that the evolution has proceeded differently in each case. In all cases, significant evolution has occurred in as little as 20-50 yr (40-150 generations), creating a species-level mosaic of response to simultaneous directional, diversifying, and normalizing selection. -from Authors