Pinus densa (Little & K.W. Dorman) Silba. Subgenus: Pinus. Section: Trifoliae. Subsection: Australes. clade: Elliottii. Common name: South Florida Slash Pine. Phenology: Jan-Feb; Oct-Nov. Habitat: Pine flatwoods, pine rocklands, scrubby flatwoods, wet pine (and cutthroat grass) savannas. Distribution: Restricted to c. and s. peninsular FL. Falsely reported by Small (1933) for GA.

Origin/Endemic status: Endemic

Taxonomy Comments: Phylogenetic studies to date fail to show that Pinus densa is more closely related to Pinus elliottii than to other Southeastern United States or West Indian pines; its treatment as a variety of P. elliottii is therefore inappropriate. Pile et al. (2018) discuss differentiation of seedling morphology of Pinus densa, P. elliottii, and other southern pines. Nikles (1966) did extensive morphological studies on Pinus elliottii s.l. and Pinus caribaea s.l., and recognized Pinus elliottii var. elliottii and var. densa. He found substantial differentiation between 'densa' and 'elliottii', and expressed both that they perhaps intergraded and that "the group of traits used in this analysis showed var. elliottii to be quite similar to var. bahamensis and var. hondurensis. There was similarity of var. elliottii and the northern populations of var. bahamensis which had been noted in the study of parental traits. There seems little doubt that the two taxa are closely related. It is of interest to note that the Big Pine Key population (area F) diverged somewhat from the three tightly clustered populations of var. densa. This probably reflects strong ecological selection peculiar to this isolated population." Furthermore Nikles (1966) concluded that "There were large differences between samples of var. densa and var. elliottii. Perhaps the discontinuity found between varieties was unduly affected by the limited sampling in the transition zone between the two" and "The current recognition of south Florida slash pine, var. densa as a variety of P. elliottii is accepted. However, further studies of P. elliottii in the transition zone are needed to determine the relationship between the two varieties." Based on his sampling, Nikles (1966) further noted a separation between Florida keys and mainland populations of 'densa': "The Florida Keys populations of var. densa constitute a distinct ecotype, just as do the Caicos Islands populations of var. bahamensis, but here also formal nomenclatural recognition is not warranted because of the clinal patterns of variation. Florida Keys slash pine has fewer and shorter cotyledons, slower development of secondary needles, lower seedling height to diameter ratio, and shorter needles than northern populations of var. densa. Further and modern study is needed.

Synonymy ⓘ: = Pinus caribaea Morelet — S, misapplied; = Pinus elliottii Engelm. ssp. densa (Little & K.W.Dorman) A.E.Murray; = Pinus elliottii Engelm. var. densa Little & K.W.Dorman — FNA2, K4, NS, POWO, SFla, Nikles (1966), Price (1989), Ward (1963); >< Pinus caribaea Morelet — S13; > Pinus densa (Little & K.W.Dorman) Silba var. austrokeysensis Silba; < Pinus elliottii Engelm. — Fl1, WH3; > Pinus elliottii Engelm. ssp. austrokeysensis (Silba) Silba. Basionym: Pinus elliottii Engelm. var. densa Little & K.W.Dorman 1952

Links to other floras: = Pinus elliottii var. densa - FNA2

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: FACW (taxonomic split from wetland indicator species)
• Great Plains: FAC (taxonomic split from wetland indicator species)

Heliophily ⓘ: 9