CAREY, SYDNEY* and D. NICHOLAS MCLETCHIE. Department of Biological Sciences, 101 Morgan Building, University of Kentucky, Lexington, KY 40506. - Testing for sex-specific life history traits under field conditions in a dioecious liverwort.
In the liverwort Marchantia inflexa, sex-specific differences
in life histories were documented in greenhouse-grown plants. Such
sex-specific life history patterns can lead to biased population sex
ratios as seen in the field. Greenhouse and field conditions are
likely to differ and sex-specific differences might be dependent on
environmental conditions. Therefore, we undertook a study to test for
sex specific differences in life histories of M. inflexa in the
field across relevant environmental variation. Along a river in a
tropical rain forest in Trinidad, plants likely to be male and plants
likely to be female were collected and planted on ten plots (40 cm x
60 cm) cleared of other M. inflexa plants. Twenty plants of
each sex were randomly planted per plot. Canopy photos (180 degree)
were taken above each plot. Analysis of these photos allowed us to
categorize each plot as a low, medium or high light plot. Data were
taken on initial plant size, and after six months we recorded final
size, number of cups (structures that produce asexual propagules) and
number of growing tips (analogous to shoots) of each plant. Females
and males did not differ in any of the three response variables.
However, there was a strong light effect where plants had greater
growth, produced more cups and produced more growing tips in high
light compared to low light. The lack of sex-specific differences in
life history traits might be due to the slower growth rates in the
field compared to the greenhouse. Plants grew approximately three
times faster in the greenhouse than in the field, and sex-specific
differences became evident after three months of greenhouse growth.
Key words: bryophytes, Marchantia inflexa, sex-specific life history traits