Testo, Weston L. , Watkins, Jr., James (Eddie) .
Gametophyte ecology of the American hart's-tongue fern, Phyllitis scolopendrium var. americana.
The American hartís-tongue fern, Phyllitis scolopendrium var. americana, is one of the rarest ferns in North America. The species only exists in a few localities in Ontario, Michigan, New York, Tennessee, and Alabama. This remarkable distribution pattern seems to be related to the speciesí habitat requirements: it is only known to grow in lime sinks and on steep, talus slopes with calcareous substrates under hardwood canopies. In recent years, the decrease in the size of several large populations in central New York has raised concerns about the conservation status of this fern: a federally-listed threatened species. While the impact of climate change and habitat disturbance has been suggested as a likely cause for the alarming instability of populations of P. scolopendrium, little is known of its gametophyte ecology. This study investigates the ecophysiology of this fern, with a focus on the stress physiology, calcium relations, and gametophyte development. The importance of calcium availability to the species was studied by monitoring the development over three Ca treatments: control, 2x, and 3x. Germination rates were similar across the treatments. Gametophyte development was similar between control and 2x, but morphology in the 3x treatment was quite different. We examined the influence of temperature on gametophyte development across two treatments: 20C representing the mean summer time temperature of the species and 25C representing IPCC predicted global temperature increase in the coming decades. Germination and gametophyte development was significantly reduced in the 25C treatment. In all cases, development stopped at a 5-7 cell protonemal stage and remained in this state for several months. Under control conditions, gametophyte germination and growth were significantly slower in P. scolopendrium than several other temperate species comparisons. For example, Athyrium thelypteroides germinated rapidly and produced mature gametophytes before P. scolopendrium gametophytes attained mature sexual status. These data suggest that gametophytes may have greater edaphic flexibility compared to sporophytes, but may be negatively impacted by even modest increases in temperature.
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1 - Colgate University, Biology, 13 Oak Drive, Hamilton, NY, 13346, USA
Presentation Type: Poster:Posters for Sections
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM