Jadera Haematoloma - Evolution

Evolution

Two populations in southern Florida are particularly notable. The more southern of these two populations has colonized a native host soapberry tree and balloon vine (Cardiospermum corindum). This vine produces capsules of a fairly uniform size, which adult J. haematoloma feed on by inserting their mouthparts (beak) through the capsule's exterior and into the interior seeds. In the mid-1950s, a southeast Asian tree, the flat-podded goldenrain tree (Koelreuteria elegans), was introduced as an ornamental plant. It escaped domestication and naturalized. Significantly, the goldenrain tree can be colonized by J. haematoloma, though its capsules are smaller and the seeds less deeply embedded than in the balloon vine.

In a seminal paper published in the scientific journal Genetica in 2001, it was shown that evolution that had taken place in this southernmost population of J. haematoloma in a period of only a few decades. They showed that the beak length, which in the ancestral type was about 70% the length of the body, was only about 50% the body length in the insects that had colonized the non-native tree, though the size of the bugs themselves had not changed. In addition, they found that:

...derived bugs mature 25% more rapidly, are 20% more likely to survive, and lay almost twice as many eggs when reared on seeds of the introduced host rather than those of the native host. Fecundity is also twice as great as that of ancestral type bugs reared on either host, while egg mass is 20% smaller.