Lupinus floridanus

Like other members of the unifoliolate Lupinus group, Lupinus floridanus is adapted to disturbance-dependent ecosystems and is associated with fire-maintained habitats.

As a legume, it forms symbiotic relationships with nitrogen-fixing bacteria, allowing it to thrive in nutrient-poor sandy soils.

Lupinus floridanus is a member of the unifoliolate Lupinus species complex of peninsular Florida, a group of closely related taxa segregated from the historically broad concept of Lupinus diffusus based on morphological and geographic differentiation.^[3][2]

Within this complex, species are distinguished primarily by leaf pubescence (density and whether the green surface is visible), leaf proportions, floral characters (especially the banner eyespot), habit, and geographic distribution.^[3]

Lupinus floridanus is characterized by moderately pubescent leaves that retain a clearly visible green surface, elongate leaf blades typically 2.4–2.9 times longer than wide, and a pale to cream-colored banner eyespot.^[2][3]

It differs from related species as follows:

• Lupinus cumulicola — leaves densely silky-pubescent, giving a silvery appearance and largely obscuring the green surface; typically occurring in central Florida ridge and scrub habitats.^[3][2]
• Lupinus pilosior — similar to L. cumulicola but with even denser, more persistent pubescence and often a more compact growth form; restricted to xeric sandy habitats in peninsular Florida.^[3]
• Lupinus ocalensis — differs in leaf shape and pubescence as well as floral characters; geographically restricted to ridge ecosystem systems of central Florida, particularly the Ocala region.^[3][2]
• Lupinus westianus — generally more robust, with broader leaves and distinct floral characteristics; restricted to southern Florida and the Florida Keys, and divided into two subspecies.^[3]
• Lupinus diffusus (sensu stricto) — more widespread outside peninsular Florida; differs in leaf morphology and floral traits, and many Florida populations formerly assigned to this species are now referred to L. floridanus or other segregates.^[3][2]
• Lupinus villosus — a more widespread southeastern species with densely silky, silvery foliage and typically larger, more robust vegetative structures; occurring primarily in longleaf pine sandhills and disturbed sandy habitats.^[2][3]

These distinctions reflect a radiation of closely related taxa adapted to xeric, fire-maintained sandy habitats of peninsular Florida, with Lupinus floridanus representing one of several narrowly endemic lineages within this complex.^[3]