Patterns of rotifer abundance within a leafy liverwort with lobular-shaped leaves

Mary Puterbaugh, J. J. Skinner, and J. M. Miller, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701. Manuscript in Review. Submitted to the American Journal of Botany, April, 2003.

We counted rotifers within lobules of an epiphytic liverwort (Frullania eboracensis subs. eboracensis). Between 13-71% of the lobules of plants growing near Portville, NY in 2000 were occupied by rotifers. Lobules containing multiple rotifers were more abundant than expected by the Poisson distribution, consistent with the hypothesis that rotifers are reproducing within lobules. Of 81 plants marked in the summer of 2001, 44 were female, 17 male, and 20 sterile. Sterile plants were significantly smaller than fertile plants. An ANCOVA revealed a nonsignificant tendency for the proportion of rotifer occupied lobules to differ among male, female, and sterile plants (P 0.09). Sterile plants tended to have the greatest proportion of occupied lobules. We hypothesized that sterile plants were younger than fertile plants. We investigated this pattern further by sampling from the interior and the edges of plants, knowing that the exterior of the plant is younger than the interior. In two separate experiments on different plants, a significantly greater proportion of exterior than interior lobules contained rotifers. The nonrandom pattern of rotifer abundance within plants is indicative of a fitness-relationship of the plants on the rotifers. We hypothesize that older plant tissue is less hospitable for rotifers than younger tissue.

2002:

Gall size and gallmaker survival under different laboratory temperature regimes: a comparison of two populations

Nicole. P. Kimball* and Mary N. Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701. Contributed Paper (poster presentation) at 78th Annual Meeting of the Pennsylvania Academy of Sciences, Pocono Manor, PA, April 5-7, 2002.

Goldenrod galls and gallmakers collected in Pennsylvania and New York (PANY) were compared to those collected in Missouri (MO). Galls were randomly assigned to four laboratory treatments: control, 5, -20, and -80 degree C treatment (N=70, MO; N=200, PANY). Galls received these temperature regimes for two weeks. Galls were opened, and larvae that failed to respond to prodding were recorded as dying during the experiment. Galls lacking gallmaker larvae were recorded as dying prior to the experiment and are not included in survival estimates that follow. Among MO gallmakers, 60, 40, 8 and 0% survived the experiment for the treatments respectively. Among PANY gallmakers, 100, 89, 77 and 64% survived respectively. The percent surviving the -80 treatment is surprising. The difference in survivorship in MO versus PANY gallmakers is consistent with the hypothesis that populations are locally adapted, though a more rigorous investigation is needed to confirm this conclusion.

Patterns of rotifer abundance in lobules of an epiphytic liverwort

John J. Skinner*, Jennifer M. Miller, and Mary N. Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701. Contributed Paper (oral presentation) at 78th Annual Meeting of the Pennsylvania Academy of Sciences, Pocono Manor, PA, April 5-7, 2002.

We investigated the rotifers occupying lobules of the epiphytic liverwort Frullania eboracensis. Samples of plants from a field population were examined microscopically for sex and rotifer abundance. Plant sex ratio was 44 female: 17 male: 20 unknown sex. Unknown plants were significantly smaller than sex-expressing plants, and the ratio of rotifers to lobules was significantly higher in the former than in the latter. Unknown plants had a mean ratio (± 1 standard error) of 0.83 (± 0.15) rotifers:lobule. Male and female plants had a mean ratio of 0.38 (± 0.04) rotifers:lobule. We also found that, within male and female plants, 68% of the lobules at the edges of plants contain rotifers (± 1SE of 2.15%), whereas lobules in the interior of the plant were less likely to contain rotifers (32 ± 4.40%). These data suggest that rotifer density is higher in lobules of young than in old plant tissue.

High rotifer abundance in liverwort plants lacking sexual structures suggests that rotifers may prefer younger plant tissue

John J. Skinner* and Mary N. Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701.. Contributed Paper (oral presentation) at 12th Annual Penn State Behrend-Sigma Xi Undergraduate Student Research and Creative Accomplishment Conference, Erie, PA, April 20, 2002

We counted rotifers that live within lobular-shaped leaves of an epiphytic liverwort (Frullania eboracensis). In the summer of 2001, portions of marked plants growing near Olean, NY were examined microscopically. Of the 81 plants, 44 were female, 17 male, and 20 plants lacked sexual structures (sex unknown). Plants lacking sexual structures were significantly smaller than sex-expressing plants, and the ratio of rotifers to lobules was significantly higher in former than in the latter (mean ratio +/- 1 standard error of 0.83 +/-0.15 and 0.38 +/- 0.04 rotifers:lobules respectively). The fact that the plants lacking sexual structures were smallest led us to believe they were younger than sex-expressing plants and that rotifers were preferentially living within younger plant tissue. To test this, we returned to the field and sampled the interior and exterior of 14 plants, knowing that within a plant the exterior tissue is likely to be younger than the interior tissue. The mean rotifer:lobule ratio in the younger exterior parts of the plants was 0.67 (+/- 0.11) and significantly higher than the ratio in the older interior parts of the plants (0.22 +/- 0.05). We hypothesize that older plant tissue is less hospitable for rotifers than younger plant tissue.

2001:

Preliminary investigation of the interaction between the liverwort Frullania eborascensis and Bdelloid rotifers

Mary N. Puterbaugh*, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701.. Contributed Paper (poster presentation) at Annual Meeting of the Botanical Society of America, Albuquerque, NM, August 12, 2001.

Bryophyte and invertebrate interactions abound, but they are poorly understood. I examined the frequency of Bdelloid rotifers within lobular-shaped leaves of an epiphytic liverwort (Frullania eborascensis) in northwestern Pennsylvania. Liverworts were randomly sampled from the bark of three neighboring streamside trees from July through September, 2000. Between 13-68% of the lobules on any given plant were occupied by rotifers (mean=30%; N = 34 samples; 5054 lobules). Of occupied lobules, 71% contained one rotifer, 20% two, and 9% three or more. This distribution is significantly different from that expected at random (Chi-square test using Poisson distribution for expected values, P<0.0001). Although further analyses are needed to confirm this conclusion, the excess of lobules with multiple rotifers supports the hypothesis that rotifers reproduce within lobules and that the plant-animal interaction could have fitness consequences for the rotifer.

An association between sex-expression in the liverwort Frullania eboracensis and Bdelloid rotifers occupying lobular leaves

John J. Skinner* and Mary N. Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701. Contributed Paper (poster presentation) at Annual Meeting of the Botanical Society of America, Albuquerque, NM, August 12, 2001.

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.

An association between sex-expression in the liverwort Frullania eboracensis and Bdelloid rotifers occupying lobular leaves

John J. Skinner* and Mary N. Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA, 16701.. Contributed Paper (poster presentation) at 2nd Annual Penn-York Undergraduate Research Conference, Buffalo State College, Buffalo, NY, October 20, 2001.

Rotifers are small animals that are often found in moss and liverwort plants. We investigated whether the abundance of rotifers occupying lobules of the liverwort Frullania eboracensis was associated with sex expression of the plants. Isolated plants of F. eboracensis growing on the bark of large trees were marked in southwestern New York (N=81 plants). Portions of the plants were removed, and examined microscopically in the laboratory. Of the 81 plants, there were 44 females, 17 males, and 20 of unknown sex. Using an analysis of variance and Tukey comparisons, we found that unknown plants were 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. Furthermore, the rotifer:lobule ratio is higher at the edge of plants than in the center. Our results provide evidence that this plant-animal interaction has ecological significance to the taxa involved.

2000:

A Study of an Unusual Relationship Between a Plant and Animal.

Mary N. Puterbaugh Mulcahy and Jennifer M. Miller*, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA 16701

Bryophyte and invertebrate interactions abound, but they are poorly understood. We examined the frequency of Bdelloid rotifers within lobular-shaped leaves of an epiphytic liverwort (Frullania eborascensis) in northwestern Pennsylvania. We randomly sampled liverworts from the bark of three neighboring streamside trees from July through September, 2000. Between 13-68% of the lobules on any given plant contained at least one rotifer (mean=28%; N = 24 samples; 3609 lobules). Of lobules containing rotifers, 72% contained one rotifer, 17% two, and 11% three or more. This distribution is significantly different from that expected at random (Poisson, X2=475, df=4, P<0.01). Although further analyses are needed to confirm this conclusion, the excess of lobules with multiple rotifers supports the hypothesis that rotifers reproduce within lobules and that the plant-animal interaction could have fitness consequences for the rotifer.

1999:

Fruit Color Preferences of Frugivorous Birds

Lisa VanGordon*, Eileen Burley, and Mary Puterbaugh, Allegheny Institute of Natural History, University of Pittsburgh-Bradford, Bradford, PA 16701

We tested whether frugivorous birds had a preference for bicolored or monocolored fruit displays. To test the hypothesis that bicolored fruit displays enhance fruit dispersal, we made two bicolored displays (black fruit with red stems and red fruit with black stems) and two monocolored fruit displays (red fruit with red stems and black fruit with black stems.) Fruits were made from flour, lard, and food coloring and were hung in trees along Tunungwant Creek near the University of Pittsburgh at Bradford campus in McKean County, PA, for two weeks in November, 1999 (n=116 artificial fruits). Each tree contained mixtures of all fruit display types. In contrast to other studies, no preference by birds was detected for fruit color, stem color or mono- or bicolored displays (chi-square analysis, P>0.05).

Studies are underway to examine fruit removal rates among the numerous trees, each consisting of one type of fruit display.

Dr. Mary Norris Puterbaugh Mulcahy

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