Rapid evolution of a divergent ecogeographic cline in introduced lady beetles

• Published in: Evolutionary ecology Vol. 31; no. 5; pp. 695 - 705
• Main Authors: O’Neill, Eric M., Hearn, Erik J., Cogbill, Jessica M., Kajita, Yukie
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-10-2017; Springer; Springer Nature B.V
• Subjects: Animal Ecology; Beetles; Biological evolution; Biomedical and Life Sciences; Clines; Coccinella septempunctata; Colonization; Convergence; Correlation; Divergence; Ecology; Evolution; Evolutionary Biology; Genetic diversity; Geography; Insects; Introduced species; Ladybirds; Life Sciences; Melanin; Original Paper; Plant Sciences; Populations; North America; Contemporary evolution; Bogert’s rule; Invasive species; Gloger’s rule; Melanin
• ISSN: 0269-7653; 1573-8477
• DOI: 10.1007/s10682-017-9908-1

The evolution of ecogeographic clines in recently introduced species is often rapid and predictable, as introduced populations often converge on the same or similar clines found among native populations. In contrast, we demonstrate the rapid evolution of a divergent ecogeographic cline among introduced populations of the seven-spotted lady beetle,
Coccinella septempunctata.
In the native range of Eurasia, this species follows Gloger’s rule—a positive correlation between melanin and precipitation. However, over several decades, introduced populations in North America have developed a divergent ecogeographic cline, Bogert’s rule, in which melanin is negatively correlated with temperature. Our common garden experiment indicates that this new pattern is not simply a plastic response to temperature, but likely reflects evolutionary change in North America. Furthermore, this new cline is not correlated with colonization history or sample collection time, but is convergent on a pattern found in other species of insects including other lady beetles. The rate of melanin evolution in North America was rapid (6897–10,000 darwins and 0.051–0.077 haldanes) and among the highest rates found in introduced insects. We propose that high levels of genetic diversity from human mediated admixture combined with altered selection pressures may have contributed to the rapid evolution of this unpredicted ecogeographic cline.