Folsom Lake is a dammed reservoir experiencing anthropogenic lake level fluctuations that have created a novel germination time for Lupinus nanus. The recently discovered summer germinating plants begin to grow in May-June, just after the typical winter germinating plants in that location die. Since flowering of summer and winter germinating plants is temporally isolated, and plants are subject to differing selective pressures, they could be two independently evolving populations. Alternatively, they could be part of one population that can respond to both natural and anthropogenic germination cues. Through a common garden experiment, a germination experiment, and microsatellite analyses of plants from these environments, these hypotheses are tested. All evidence supports the hypothesis that summer and winter germinating plants are part of the same population, which can respond to germination cues at various times of the year.