SKINNER, JOHN J.* and MARY N. PUTERBAUGH. University of Pittsburgh at Bradford, Allegheny Institute of Natural History, 300 Campus Dr., Bradford, PA 16701. - An association between sex expression in the liverwort Frullania eboracensis and Bdelloid rotifers occupying lobular leaves.
During May, 2001, we investigated whether there was an association
between the abundance of rotifers occupying lobules of the epiphytic
liverwort Frullania eboracensis and sex expression of the
plants. At our field site in southwestern New York, isolated patches
of F. eboracensis (referred to as "plants" and
assumed to be unique genets) were marked on nine different trees (N=81
plants). Portions of the plants were removed, and examined
microscopically in the laboratory. Presence of sexual structures
(antheridial branches and sporophytes) was noted, and the numbers of
rotifers and lobules were counted. Plants were also measured for size.
Plants for whom no sexual structures were found were sampled at least
twice more in June to confirm lack of sex-expression. Of the 81
plants, there were 44 females, 17 males, and 20 of unknown sex. Using
an analysis of variance followed by Tukey multiple comparison tests,
we found that unknown plants were significantly smaller than
sex-expressing plants and that the ratio of rotifers to lobules was
significantly higher in plants of unknown sex than in either male or
female plants. Plants of unknown sex had a mean ratio (± 1 standard error) of 0.83 (±0.15) rotifers:lobules. Male and female plants
had a mean ratio of 0.38 (± 0.04)
rotifers:lobules. Within sexes, there was no significant correlation
between rotifer abundance and size nor between rotifer abundance and
the number of sexual structures observed on the samples. Our results
provide evidence that this plant-animal interaction has ecological
significance to the taxa involved.
Key words: Bdelloid rotifer, bryophyte, Frullania eboracensis, liverwort, plant-animal interaction, sex ratio