"Subspecies - A category in biological classification that ranks immediately below a species and designates a population of a particular geographic region genetically distinguishable from other such populations of the same species and capable of interbreeding successfully with them where its range overlaps theirs." 

(Merriam-Webster)


I used the above definition when choosing subspecies, though I included probable species at this rank, erring on the side of caution. There are other defininitions, and defining "species" is quite problematic. I think this one seems to be a workable and respectable choice for the Florida Liguus

All six tentative subspecies were in isolated geographic regions. They retained their distinct morphologies and behaviors. Up-to-date genetic analyses are needed.

Only one pair of the tentative subspecies used in this model has been known to interbreed successfully - pictus and lignumvitae, (dryas x pseudopictus), have produced a persistent and consistent offspring, the proposed sparksi. They were artificially brought together. Other such efforts with different "subspecies" seem to have failed. This suggests that only pictus and lignumvitae are truly subspecies. The six follow.


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L. f. lignumvitae Pilsbry 1912

Range of the subspecies lignumvitae in about 1900: primarily on Lower Matecumbe Keys. Also on several nearby keys. 
Morphology of the subspecies: relatively elongate. Body whorl with somewhat flattened sides and an associated weak keel at the base. Columella typically thin and straight. Shell smooth although growth stops may be slightly prominent. Periostracum glossy. Pattern and color not continuously variable within the subspecies, though mixes, very uncommon, are more frequent than within pictus. Periostrical green lines occur more frequently than within pictus.

Comments - Similar to pictus and apparently closely related. One seemingly consistent and persistent hybrid was artificially created with a mating of dryas and pseudopictus. The graphicus morph innominatus was conflated with lignumvitae by Pilsbry. The background color is usually a pale yellow-cream to white, making the zonation on some varieties difficult to determine.



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L. f. matecumbensis Pilsbry 1912


Range of the subspecies matecumbensis in about 1900: primarily on the southwestern edge of Floridafrom Cape Sable to Flamingo, and the Matecumbe Keys. Several other occurances in the Keys include Key Vaca.
Morphology of the subspecies: rather squat only at the type locality, more elongate in most other populations, primarily on the mainland. The more elongate shells have flattened sides and the associated basal keel. The elongate shells almost always have a unique concave columella. Easily identified by a yellow-orange subsutural line that blends into the paler overall yellow-orange of the shell.

Comments - Not closely related to any other subspecies although some hybridization with nearby subcrenatus on Upper Matecumbe Key caused some collectors to link the two.



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L. f. pictus (Reeve 1842)

Range of the subspecies pictus in about 1800: primarily on the Pine and Torch Keys, and Key West, and probably several keys between;
by 1900, on the Pine and Torch Keys only. 
Morphology of the subspecies: relatively elongate. Body whorl evenly convex. Columella typically thin and straight. Shell surface very smooth, even at growth stops. Periostracum glossy. Patterns and colors of individual varieties are not continuously variable. Mixes within the subspecies are very rare.

Comments - Similar to lignumvitae and apparently closely related. One seemingly consistent and persistent hybrid was artificially created with a mating of dryas and pseudopictus.


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L. f. septentrionalis Pilsbry 1912


Range of the subspecies septentrionalis in about 1900: exclusively between Palm Beach and just north of Miami.
Morphology of the subspecies: a rather squat shell similar in shape to the matecubensis of Upper Matecumbe Key. Columella thin and straight. It differs from matecumbensis in having a strong keel at the level of the posterior end of the aperture. The sides of the spire are relatively flattened. Relatedly, another unique characteristic of the subspecies is the large aperture, about half the length of the shell. The shell is smooth with a slight prominence at growth stops. The periostracum is very glossy. The shell color is invariably pure white, and with or without green periostrical green lines. 
Comments: The morphology appears to be homozygous, with no noticeable variation throughout its range. Septentrionalis seems to be the result of a single landfall and is not closely related to any other Florida subspecies. 


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L. f. solidulus Pilsbry 1912

Range of the subspecies septentrionalis in about 1800: Stock Island, Saddlebunch Keys, and possibly Key West and other nearby keys.
Morphology of the subspecies: less narrow than the other subspecies of the Lower Keys, pictus. It's shape is similar to vacaensis with the exception of its columella which is usually straight and thin. The shell is marked by vertical striations, strongest just below the suture. This is a unique characteristic. The yellow banding is not related to zonation. The same pattern is not unique and is found on mainland shells, particularly yellow morphs of lossmanicus.
Comments: This subspecies seems to be related to the subspecies solidus. I think it may have been an introduction of lossmanicus that developed the unique texture in isolation (Stock Island?), i.e., the founder effect and/or mutation.   


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L. f. solidus (Say 1825), Key Vaca (left); holotype (right)

Range of the subspecies solidus in about 1800: centered at Brickell Hammock, extending throughout most of the range of the Florida Liguus. 
Morphology of the subspecies: overall shell shape is very variable though most are evenly convex. The base is rarely keeled. The columella varies from straight and thin to heavy and truncate.This variation is associated with shell mass, which within this subspecies is largely subject to environmental conditions.The shell surface is usually marked by growth lines and prominent growth stops. Color and pattern often change significantly after these stops. The periostracum varies from somewhat glossy to thick, rough and, prone to flaking. Pattern and color are continuously variable, a unique feature of the subspecies. Hundreds of color/patten combinations occur, with some consistent and persistent, and others not. This is the only subspecies with significant mixing. These phenotypes should not be confused with genotypes. See Donax variabilis, the small surf clam of the southeast coast of the U.S.
Comments - Most named and published taxa of the Florida Liguus fall within this subspecies.    

Edited 108 times by Lysiloma Dec 23 15 8:12 AM.