FWGNA > Species Accounts > Pleuroceridae > Pleurocera floridensis timidus
Pleurocera floridensis timidus (Goodrich 1942)
Goniobasis or "Elimia" floridensis

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> Habitat & Distribution

Populations of P. floridensis are widespread throughout the northern half of Florida and the Gulf drainages of Georgia (Clench & Turner 1956, Chambers 1980, Thompson 2004) in rivers, springs, and the nearshore regions of lakes with low to moderate current.  Hanley & Ultsch (1999) reported individuals on all available substrates, to depths of 1.5 meters, in waters with temperatures of 14 - 26 degrees C and a pH of 7.55 - 8.45.

The occurrence of P. floridensis in Atlantic drainages of Georgia was not suspected until the population genetic survey of Dillon & Robinson (2011).  We have recently documented several populations of P. floridensis bearing weakly-sculptured shells inhabiting springs and spring fed streams in the vicinty of Hawkinsville.  These populations were originally described as "Goniobasis mutabilis timidus" by Goodrich (1942).  But since mutabilis has proven to be a synonym of catenaria, we suggested that the subspecific nomen be transferred to P. floridensis.  Pleurocera floridensis is pseudo-rare in our 17-state study area, FWGNA incidence rank I-2p.  See my essay of 6Jan14 (from the link below) for more.

> Ecology & Life History

In peninsular Florida, populations of P. floridensis bearing the typical shell morphology lay eggs from February to October, embedding them within sand grain matrices and affixing them to plants and hard objects (Chambers 1980).  Although there have been no detailed studies of P. floridensis life history, I imagine that two years are required for maturity, and that several years of iteroparous reproduction can be expected thereafter, as is the case for pleurocerids generally (Dazo 1965).  This is life cycle Hi of Dillon (2000: 156 - 162).

Hanley & Ultsch (1999) reported that P. floridensis grazes on algae and other periphyton, as is typical of pleurocerids generally.  Grazing by high densities of pleurocerids can have a significant impact on energy flow in streams (Dillon 2000: 86 - 91).

> Taxonomy & Systematics

Genetic divergence at allozyme-encoding loci among populations of P. floridensis from Florida and the Gulf drainages of Georgia has been well studied by Chambers (1978, 1980, 1990). The survey of Dillon & Robinson (2011) included one of the Chambers (1980) populations (bearing Click for largerthe typical shell morphology) as a control, as well as samples of P. floridensis timidus from Mile Creek (on the southern edge of Hawkinsville) and a Flint River tributary near Vienna.  All three were quite similar genetically.  The diploid numbers of several populations have been reported as 2N = 36 (Chambers 1982, Dillon 1989, 1991).

Mihalcik & Thompson (2002) reported that the mitochondrial CO1 gene sequences of two timidus individuals sampled from the vicinity of Hawkinsville were very similar to individual P. floridensis sampled from tributaries of the Flint River ("induta") and Chattahoochee River ("glarea").  They nonethless raised Goodrich's taxon to the specific level and described two subspecies beneath it, "Elimia" timida exul and E. timida nymphaea.  These are all synonyms of P. floridensis timidus, as well as inclinans (Lea 1862).

This species has travelled through three genera in thirty years.  Although predominantly assigned to Goniobasis through most of the 20th century, in the 1980s many workers began placing it in the resurrected generic nomen, "Elimia."  Both Goniobasis and Elimia were subsumed under Pleurocera by Dillon (2011).  See my essay of 23Mar11 from the link below for more.

> Supplementary Resources [PDF]

> Essays

  • Taxonomic controversy has surrounded the generic nomina Pleurocera, Goniobasis, and Elimia for many years.  The best entry into the subject would be my essay of 23Mar11, entitled Goodbye Goniobasis, Farewell Elimia.  Links are available from that essay to older resources.
  • I used P. floridensis timidus to illustrate the concept of "pseudo-rarity" in my essay of 6Jan14, Why Is Rarity? 
  • Pleurocera floridensis timida received passing mention in my essay of 4Feb14, What Is a Subspecies? 
  • The taxonomic history of the nomen "timida" was reviewed at somewhat greater length in my follow-up essay of 5Mar14, What Subspecies Are Not.
  • I reviewed the tortured taxonomic history of P. floridensis in a pair of companion pieces, "Fred Thompson, Steve Chambers, and the Pleurocerids of Florida" (15Feb17) and "Fred Thompson, Elizabeth Mihalcik, and the Pleurocerids of Georgia" (14Mar17).

> References

Chambers, S. M.  (1978)  An electrophoretically detected sibling species of "Goniobasis floridensis" (Mesogastropoda: Pleuroceridae).  Malacologia 17: 157-162.  
Chambers, S. M. (1980)  Genetic divergence between populatons of Goniobasis (Pleuroceridae) occupling different drainage systems.  Malacologia 20: 63 - 81.  
Chambers, S. M. (1982)  Chromosomal evidence for parallel evolution of shell sculpture pattern in Goniobasis.  Evolution 36: 113-120.  
Chambers, S. M. (1990) The genus Elimia (= Goniobasis) in Florida (Prosobranchia: Pleuroceridae). Walkerana, 4, 237-70.  
Clench, W. J. & R. D. Turner (1956)  Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River.  Bull. Florida State Museum 1: 94 - 239.   
Dazo, B. C. (1965)  The morpholoogy and natural history of Pleurocera acuta and Goniobasis livescens (Gastropoda: Cerithiacea: Pleuroceridae).  Malacologia 3: 1 - 80.    
Dillon, R., T. Jr. (1989)  Karyotypic evolution in pleurocerid snails: I. Genomic DNA estimated by flow cytometry. Malacologia, 31: 197-203.  
Dillon, R., T. Jr. (1991)  Karyotypic evolution in pleurocerid snails: II.  Pleurocera, Goniobasis and Juga.  Malacologia 33: 339 - 344.   
Dillon, R. T., Jr. (2000)  The Ecology of Freshwater Molluscs. Cambridge, Cambridge University Press.  509 pp. 
Dillon, R. T., Jr. (2011)  Robust shell phenotype is a local response to stream size in the genus Pleurocera (Rafinesque, 1818).  Malacologia 53: 265-277.
Dillon, R. T., Jr. & Robinson, J. D. (2011) The opposite of speciation: Genetic relationships among populations of Pleurocera (Gastropoda: Pleuroceridae) in central Georgia.  Am. Malac. Bull. 29: 1 - 10. 
Goodrich, C. (1942) The Pleuroceridae of the Atlantic coastal plain. Occas. Pprs. Mus. Zool. Univ. Mich., 456, 1-6.  
Hanley, R.W. & G.R. Ultsch (1999)  Ambient oxygen tension, metabolic rate, and habitat selection in freshwater snails. Archiv fur Hydrobiologie 144:195-214.  
Mihalcik, E. R. & F. G. Thompson (2002) A taxonomic revision of the freshwater snails referred to as Elimia curvicostata, and related species.  Walkerana 13: 1 - 108.   
Thompson, F.G. (2004)  An identification manual for the freshwater snails of Florida. [html]