Frequency, Distribution and Ecological Impact of Cryptic Hybrid Invaders: Management Tools for Eradication of Invasive Spartina

Spartina alterniflora is an exotic weed that has prolifically interbred with the native cordgrass (S. foliosa) in the San Francisco Bay’s marshlands. Its hybrids have elbowed out parent species and are colonizing habitats beyond the ranges of either parent species. This project seeks to document hybrids’ fitness advantage, through “common garden experiments.” The fellow has planted hybrids and parental species across a range of intertidal elevations and is monitoring survivorship and growth. To date, all taxa have grown best at mid elevations, under favorable environmental conditions, with the hybrids growing fastest in this optimal habitat. As environmental conditions became stressful in late autumn, all taxa performed poorly at mid elevation, and the parental species perished at low elevations. The hybrid was able to survive in both mid and low habitats. It appears that hybrids are effective invaders because they can colonize new habitat and capitalize on optimal growing conditions.