Dioecy hotspots in Southeast Florida (U.S.A.), especially Saw Palmetto (Serenoa repens, Arecaceae) thickets

A survey of woody marshland hummocks, of Saw Palmetto (Serenoa repens, Arecaceae) thickets, and of additional Southeast Florida habitats revealed multiple sites with dioecy rates of 50–100%, especially in the Saw Palmetto thickets. These rates exceeded any encountered for woody species in a literature review globally or for Florida. A particularly notable feature of the thicket sites is extreme thick low-elevation palm frond canopy coverage, consistent with the historical perspective that a benefit of dioecy is sexual selection for seed quality where harsh ecological filters limit establishment.