PARENT SESSION
Oral Session # 49: Invasive Species IV: Grasslands; Wetlands.
Presiding: F Hughes
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 204.

The life history of the invasive fern Lygodium microphyllum: from reproductive strategy to landscape dispersal.

Volin, John^*,1, Lott, Michael¹, Muss, Jordan¹, Owen, Dianne¹, Stewart, Joy¹, ¹ Florida Atlantic University, Davie, FL

ABSTRACT- We studied the life history of Lygodium microphyllum, a highly invasive non-indigenous fern species with a kudzu-like growth form that is currently spreading rapidly throughout southern Florida. Examination of its reproductive biology showed that L. microphyllum is capable of using all three mating systems: intragametophytic selfing, intergametophytic selfing, and outcrossing. This complex reproductive biology is highly unusual for the vast majority of fern species studied to date. The ability of L. microphyllum to utilize all three mating systems lends support to our hypothesis that its reproductive strategy partially explains its invasive spread across the landscape. In addition, we found that its invasiveness is enhanced by the ability of a female gametophyte to determine the sex of nearby gametophytes, making them male and thus ensuring cross-fertilization. The distribution of L. microphyllum was also examined at the community level in forested wetland sites within the Big Cypress Swamp. The observed patterns indicated that L. microphyllum is predominantly found in moderately hydric conditions; relatively low elevation, deep substrate and high substrate water content were significantly related to its presence. We also developed a cellular automaton dispersal model for L. microphyllum. The model was calibrated using actual data from 1978 to 1993, then validated independently using actual data from 1993 through 1999. A projection to 2009 used actual 1999 flight survey data as a starting point and showed an alarming increase in L. microphyllum establishment across South Florida, in particular in the cypress-dominated wetlands of the Big Cypress Swamp.

Key words: invasive species, Lygodium microphyllum, Everglades, Old World climbing fern