Asexual reproduction and distribution of Adirondack bladderworts
Utricularia inflata is a submersed macrophyte expanding its range in the northeastern United States and threatening lake ecosystems. While U. inflata is a new addition to these systems, there are a number of closely related Utricularia species within the invaded waterways. Utricularia pupurea and U. vulgaris are two such free-floating plants. A series of greenhouse and field studies sought to distinguish traits among these three macrophytes. A greenhouse experiment compared the vegetative propagation of these plants in a temperature-controlled tank. The displacement of these species by water movement was examined in field trials while vegetation sampling with SCUBA determined the distribution of these species across a range of depths at five lake sites.
Utricularia inflata and U. vulgaris had a greater production of potential propagules compared to U. purpurea, but the two former species exhibited differences in their asexual reproduction. New U. vulgaris branches grew significantly longer (P<0.001), while U. inflata fragments exhibited a greater number of new branches (P<0.001). Each new branch has the potential to develop into a new individual as the original stolon decays; this trait may help explain how U. inflata is quickly reaching high populations in newly colonized lakes. Results of the displacement experiment showed that all species were less likely to remain in the shallows (P<0.01). However, recovery of U. inflata was lower than U. vulgaris (P<0.05). Vegetation sampling also indicates that U. vulgaris and Utricularia species attached to the sediment (U. resupinata and U. intermedia) are found in the shallows, while U. inflata and U. purpurea are found at greater depths. These results suggest that U. inflata is more susceptible to water movement and may be spread to downstream systems at a faster rate, compared to U. vulgaris and attached Utricularia species.