Abstract Detail

Ecological Section

Sebesta, Nicole [1], Richards, Jennifer [2], Taylor, Jonathan [3].

The Effects of Fire on Spore Viability of Lygodium microphyllum.

Lygodium microphyllum (Old World Climbing Fern) is a twining fern native to the subtropics of Africa, Asia and Australia. Since its introduction to Florida’s east coast in the late 1950s, the fern has infested more than 49,000 hectares of central and south Florida, destroying native habitats, reducing biodiversity and altering fire regimes in part by forming meter-thick rachis mats that smother native vegetation. L. microphyllum has been designated one of Florida’s most serious invasive species due to the severe ecological damage it has caused, which even threatens the success of Everglades restoration.
A homosporous fern, L. microphyllum produces spores that develop into bisexual gametophytes able to reproduce sexually by three modes: intergametophytic crossing, intergametophytic selfing, and intragametophytic selfing. Intragametophytic selfing, which requires only a single spore, may be the most important mode for long-range dispersal and colonization, allowing L. microphyllum to colonize remote areas in the Everglades.
Prescribed fire is one method used to control L. microphyllum. In fire-adapted habitats, prescribed fire effectively reduces L. microphyllum biomass over large areas, but fire’s effects on spore viability are unknown. Many factors affect fire behavior, including fuel characteristics, soil moisture, relative humidity, and duration, yielding a mosaic of temperatures up to 700°C, sometimes more. As burns are variable and heterogeneous across a landscape, areas of sporulating L. microphyllum may be flanked by fire but escape combustion. If unconsumed spores remain viable and are further dispersed by fire-created updrafts, prescribed fire treatments may exacerbate L. microphyllum spread. If spores experience elevated temperatures, however, they may be rendered nonviable. To address this concern, we tested the heat tolerance of L. microphyllum spores.
Spores were collected from local populations of L. microphyllum and exposed to temperatures ranging from 50°C to 95°C for durations of 5 minutes to 1 hour, then allowed to germinate on fern nutrient agar (0.8%) in petri plates set in growth chambers with 13/11 light/dark cycle and 26/24°C. Percent spore germination was assayed after two weeks.
Temperatures of 50°C had little effect on germination; 95°C killed spores at all durations. Between these extremes, spore viability decreased with exposure to increasing temperatures and durations. Results indicate that viability of unconsumed spores depends on temperature and duration of heat exposure, but also that relatively low temperatures kill spores. This knowledge, combined with heat maps of Lygodium burns, will allow us to more accurately predict fire’s effects on the spread of this invasive exotic.

1 - Florida International University, Biology, 11200 SW 8th Street , Miami, FL, 33199, USA
2 - Florida International University, Department Of Biological Sciences, Miami, FL, 33199, USA
3 - Everglades National Park, Restoration Program, 40001 State Road 9336, Homestead, FL, 33034, USA

Keywords:
Lygodium microphyllum
Old World Climbing Fern
invasive species
Everglades
spores
prescribed fire.

Presentation Type: Oral Paper:Papers for Sections
Session: 9
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 9:00 AM
Number: 9003
Abstract ID:1278
Candidate for Awards:Ecological Section Best Graduate Student Paper