Abstract Detail

Bryological and Lichenological Section/ABLS

Moore , Jonathan David [1], Kollar, Leslie [2], McLetchie, D. Nicholas [3].

Sex-specific clump morphology leads to differences in water retention ability in Bryum argenteum.

Males of abiotically pollinated angiosperms (both woody and herbaceous) and water-fertilized bryophytes should have comparable morphologies that reflect selection to increase mating success.  In wind pollinated species this means allowing air flow (pollen dispersal); and in water-fertilized species this means allowing water flow (pollen or sperm dispersal).  In bryophytes, this may mean smaller males with more streamlined clump profiles or lower shoot densities.  For female bryophytes, the prediction would be for clump morphology that would lead to higher water retention (required for successful fertilization).  While such studies on sexual dimorphisms in morphology in wind pollinated species have been done, no analogous studies have been done in water fertilized species like bryophytes.  We tested the prediction that females would retain more water at the clump level due to differences in morphological characters such as density or size of shoots using the moss, Bryum argenteum.  Twenty five female and 25 male isolates were collected in three urban environments in Kentucky, USA and were cultured in a growth chamber to remove field effects.  We grew four replicates of each isolate in identical conditions in a greenhouse in local topsoil kept evenly moist.    Plants were allowed to grow for five weeks and then were assayed for external water retention at the single shoot level while both dry and hydrated.  Plants were allowed to continue to grow for 35 subsequent weeks to allow for clump formation.  One cm² soil surface samples were taken and saturated with water.  External clump water content was estimated by removing water from plants using centrifugal force and weighing. We found that females retain more water per unit horizontal clump area than males.  This difference was not due simply to the external water retention ability of individual shoots because males and females did not differ in water retention at the single shoot level either hydrated or dry when standardized for shoot length.   Our results support our hypothesis that selection due to sex-specific reproductive requirements leads to differing clump morphologies. These differences could lead to females being hydrated for longer periods than males, which would increase their opportunity to grow faster than and outcompete males leading to female-biased adult sex ratios.

1 - University of Kentucky, Biology, 101 T. H. Morgan Building, Lexington , KY, 40506-0225, USA
2 - Washington and Jefferson College, Biology, 60 South Lincoln St, Washington, PA, 15301, USA
3 - University Of Kentucky, Department Of Biology, 101 MORGAN BUILD., LEXINGTON, KY, 40506-0225, USA

Keywords:
external water content
mating success
biased sex ratios.

Presentation Type: Oral Paper:Papers for Sections
Session: 2
Location: Firs North/Boise Centre
Date: Monday, July 28th, 2014
Time: 8:30 AM
Number: 2003
Abstract ID:754
Candidate for Awards:A. J. Sharp Award