Abstract Detail

Ecological Section

RICHARDS , JENNIFER H [1], ABREU, ANDREW [2], CORDOVA, JOSE R. [2], TAYLOR, JONATHAN [3].

Sawgrass (Cladium jamaicense) fruit development, phenology and abortion in relation to sawgrass seed bank viability.

The common, Caribbean, marsh macrophyte Cladium jamaicense (sawgrass) has high levels of fruit abortion in the field.  We determined the timing of fruit abortion in relation to fruit shedding by following the phenology of post-fertilization fruit development and of fruit drop in southern Florida, USA.  To document changes in fruit biomass, morphology, and abortion rate, fruits at two sites were harvested from the same individuals at 2-week intervals, weighed individually, and examined for potential viability, as determined by endosperm condition.  To determine the phenology of fruit loss, fruits shed into ¼ m² traps placed in sawgrass patches at two sites were counted and assayed for potential viability every one or two weeks in the summer 2009 and 2010.  Mature viable sawgrass fruits invested 18 ± 1% of their biomass in the outer fruit wall, 69 ± 2% in the endocarp and 13 ± 1% in the seed embryo and endosperm.  Sawgrass plants had late fruit abortion that occurred prior to shedding but after investment in fruit development, including production of the thick lignified endocarp; this developmental sequence produced persistent aborted fruits that were retained on the plant and shed with viable fruits.  Sawgrass shed fruits from mid-July through September with peak fruit drop from late July to mid-August, 2 to 2.5 months after flowering.  Sawgrass fruits had high rates of abortion that differed among plants and between sites and increased from mid-July through August.  One-third to one-half of all fruits shed by a plant over the summer were aborted.  Because aborted fruits can persist in the soil, we constructed a model for seed bank viability that included the effect of these fruits, as well as loss over time by germination and other losses (predation, decay and seed burial) on seed bank viability.  The model predicted levels of 2% seed germination from the seed bank for 50% abortion that produces persistent aborted fruits; similar values have been documented in the literature for germination rates from sawgrass seed banks.  The low percent of viable sawgrass seeds reported here provides a baseline population parameter for Everglades and other Caribbean marsh restoration modeling and indicates a general need to determine contribution of persistent aborted fruits when studying seed banks and/or germination.

1 - Florida International University, Department Of Biological Sciences, Miami, FL, 33199, USA
2 - Florida International University, 11200 SW 8th St., Dept. of Biological Sciences FIU, Miami, Florida, 33199, United States
3 - Everglades National Park, South Florida Natural Resources Center, 40001 State Highway 9336, Homestead, FL, 33034, United States

Keywords:
sawgrass
Cyperaceae
fruit abortion
seed bank
Everglades.

Presentation Type: Oral Paper:Papers for Sections
Session: 1
Location: Firs South/Boise Centre
Date: Monday, July 28th, 2014
Time: 8:15 AM
Number: 1002
Abstract ID:171
Candidate for Awards:None