Philippi, Tom , Richards, Jennifer .
Spore rain and environmental effects on spore germination and gametophyte growth in the invasive exotic Old World climbing fern, Lygodium microphyllum.
THE fern Lygodium microphyllum is a major invasive exotic in southern Florida wetlands, where it overgrows tree islands and mangroves. Because its spores are aerially dispersed, and a single spore can produce a new infestation, this species has immense potential to colonize new habitats. The additional life cycle steps required by spore reproduction, however, are filters, because each stage requires specific environmental conditions. Knowing spore dispersal phenology and gametophyte environmental requirements could substantially reduce the area and times of year that need to be searched for new infestations. To quantify spore rain onto a known area, we developed low cost spore samplers built from three Buchner funnels and a bucket reservoir. In 2005 we deployed 11 samplers around southern Florida. At sites close to heavy L. microphyllum infestations, May-August influx rates ranged from 15 to 170 spores m-2day-1 but declined to 6-17m-2day-1 after October, which may reflect seasonal phenology or pre- vs. post-hurricane conditions. A site in the urban landscape had lower but variable influx, declining from 11m-2day-1 in May-August to 2.3m-2day-1 in November-December. Influx rates in or close to Everglades National Park ranged from 0.1m-2day-1 to 2m-2day-1. To understand environmental requirements for spore reproduction, we germinated spores on 1/4 strength Hoagland’s nutrient medium in petri dishes randomly assigned to growth chambers programmed with 13 hr Light:11 hr Dark or 11 Light:13 Dark and 30°C/25°C or 25°C/20°C day/night temperatures. Within each growth chamber, light levels were ~310µmol m-2sec-1 or ~75µmol m-2sec-1 under neutral density shade film. Spores germinated within 8 days; under the best treatment combination, gametes were present by day 23 and sporophytes by day 53. Chamber conditions affected the timing and growth rates of gametophytes, with lower temperatures and shorter days having earlier spore germination and faster gametophyte development.
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1 - Florida International University, Deparment of Biological Sciences, 11200 SW 8th St., Miami, Florida, 33199, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 4:00 PM