Scientific Note: Capsule-Seed Allometric Relationships in Ludwigia ravenii (Onagraceae), a Critically Imperiled Wetland-Obligate

Abstract

ABSTRACT Ludwigia ravenii is a critically imperiled tetraploid known historically from Virginia to Florida. There have been no published studies examining the number of seeds produced per capsule to guide researchers and conservationists in planning studies or collection efforts. Such data are important considering current guidelines by the Center for Plant Conservation recommend that no more than 10 percent of a population's seed production be collected in a single season. To fill this void, our objective was to examine and report on capsule-seed allometric relationships in the species. Our study is based on 25 capsules from six plants from the North Carolina Coastal Plain. Though admittedly limited in geographic scope, we focused on these wild plants to avoid destruction of herbarium specimens and as they were already the subject of a broader, permitted inquiry into seed germination. Consistent with prior, range-wide monographic study, measured capsule dimensions were: length 2.87–5.41 mm (mean=3.98, sd=0.64); broader facet width 1.95–3.67 mm (mean=2.94, sd=0.43); narrower facet width 1.88–3.27 mm (mean=2.70, sd=0.39). The mean number of seeds produced per capsule was 304.8 (sd=94.9). The mean number of seeds produced by capsules at least 4 mm long was 361 (sd=65.7), whereas the mean number of seeds produced by capsules less than 4 mm long was 233 (sd=77.8). In the absence of additional data from other populations, we preliminarily recommend that capsule collection efforts focus on capsules at least 4 mm long.