Examination of the reproductive ecology of Pistia stratiotes L. in Florida

Authors: ZITELLI, ANGELINA - Florida Atlantic University; FRAZIER, EVELYN - Florida Atlantic University; Dray Jr, Forrest

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Waterlettuce is an important aquatic weed interfering with agricultural irrigation, flood controls, and recreational boating/fishing activities tied to ecotourism. Little is known about how this weed reproduces or what pollinates it, yet this knowledge is important for forming plans on controlling it. Further, recent discoveries show there are multiple genotypes in the state and understanding differences between them is critical for control efforts. We're studying whether the plants self-pollinate, are insect pollinated, or both, whether microbes in the flowers influence pollination, and whether reproduction differs between the invasive and the native gentoypes. Preliminary results suggest the two types differ in reproductive success and timing, but that microbes may not influence this success.

Technical Abstract: Pistia stratiotes L. (waterlettuce) is one of the world's most problematic aquatic weeds, yet its reproductive ecology remains poorly understood. While vegetative propagation via stolons is well documented, the relative contributions of sexual reproduction, pollination mode, and floral microbiome to population dynamics and invasion success have received little scientific attention. This knowledge gap limits the effectiveness of management strategies targeting the plant's most vulnerable life history stages. This study investigates pollination mechanisms, reproductive phenology, and floral microbiome composition in two Florida haplotypes of P. stratiotes, Type A (non-native, invasive) and Type E (native), to determine how reproductive ecology varies with haplotypic identity and which ecological partners influence reproductive success. Controlled pollination experiments are being conducted at the USDA-ARS Invasive Plant Research Laboratory in Davie, Florida, exposing tagged individuals (n = 100; 50 per haplotype) to five treatments: open pollination, pollinator exclusion (bagged), manual self-pollination, manual cross-pollination, and an emasculated control. Seed set per inflorescence is quantified 14–21 days post-anthesis and analyzed using generalized linear mixed models with pollination treatment and haplotype as fixed effects and tank as a random effect. Pollinator identity is assessed by applying Tangle-Trap® adhesive to spathes and identifying captured arthropods to family or species level. Floral microbiome composition is characterized through culture-based methods, with colony morphotypes compared qualitatively between haplotypes and treatments. Preliminary results indicate that manually pollinated treatments are expected to produce greater seed set than pollinator-exclusion treatments, suggesting pollen limitation under natural conditions and confirming a functional role for sexual reproduction in this species. Pollinator visitation is expected to be infrequent and dominated by small arthropods, consistent with P. stratiotes' reliance on vegetative reproduction as a reproductive assurance strategy. Culture-based microbiome screening is expected to reveal little to no difference in colony morphotype assemblages between Type A and Type E haplotypes, suggesting that shared aquatic environmental conditions, rather than host plant identity, are the primary driver of culturable floral microbial composition in P. stratiotes. These findings indicate that sexual reproduction in P. stratiotes is functionally present but likely pollinator-limited, and that haplotypic identity has minimal influence on floral microbial assemblages under shared environmental conditions. Understanding these reproductive dynamics has direct implications for aquatic weed management: targeting the conditions under which sexual reproduction succeeds may offer novel strategies for reducing waterlettuce spread and protecting native freshwater biodiversity.