Because the Florida tree snail occurs  in numerous hammocks within its limited range, and that much of their range is on protected lands, it  is generally not considered in imminent danger of extinction (Voss 1976).

However, a new threat has emerged that warrants consideration of its potential threat to the viability of tree snails in southern Florida. Red imported fire ants (Solenopsis invicta Buren) have become well established in Florida and may pose a serious threat to L. fasciatus, as well as numerous other invertebrate species (Porter and Savignano 1990, Forys et al. 2001a, 2001b, Stevens et al.1999, Yusa 2001).

Fire ants were inadvertently introduced into the southeastern United States > 50 years ago and arrived in Florida soon thereafter (Callcott and Collins 1996). They were first confirmed within the range of Liguus in Florida (i.e., in Collier, Dade, and Monroe Counties) during the 1970s, and have expanded within those counties since that time.

First Reported Occurance of Red Imported Fire Ant (Solenopsis invicta ) in the United States.  Click for Map

Fire ants are known to attack and kill Liguus (Tuskes 1981, Forys et al. 2001a), as well as other invertebrates (Porter and Savignano 1990) including Florida apple snails (Pomacea paludosa) (Stevens et al. 1999) and the eggs of apple snails elsewhere (Yusa 2001). Further, recent studies have indicated that fire ants are one of the most likely causes for the extinction of the Stock Island tree snails (Orthalicus reses reses) within their native range (Forys et a, 2001a).

The effects of fire ants on native fauna is an emerging issue that will likely intensify over the next few decades.  The potential effects also go well beyond Liguus tree snails. Fire ants may also affect ground-nesting birds (Allen et al. 1995)(which may ultimately raise concern for species such as the Cape Sable Seaside Sparrow), small mammals (Allen et al. 1994), and widespread effects on invertebrate communities (Porter and Savignano 1990).

Because of this concern, the USGS is attempting to initiate a project in collaboration with Big Cypress National Preserve to evaluate the risk that fire ants pose on the viability of populations of Liguus within otherwise protected habitats.

Pending funding, the specific objectives of this research would be to assess the effect of imported red fire ants on: (1) the relative density of Florida tree snails in hammocks with and without fire ants, (2)  the relative hatching success of Florida tree snail egg clutches laid in hammocks with and without fire ants, and (3) the relative survival of Florida tree snails in hammocks with and without fire ants.

For further information about this project contact:

Robert Bennetts, Email: rbennetts@usgs.nps
USGS, Florida Integrated Science Center

or

Deborah Jansen, Email: Deborah_Jansen@nps.gov
Big Cypress National Preserve
 

Literature Cited:

Allen, C. R., S. Demarais, and R. S. Luiz.  1994. Red imported fire ant impacts on wildlife: an overview.  Texas Journal of Science 46:51-19.   

Allen, C. R., R. S. Luiz, and S. Demarais. 1995.  Red imported fire ant impacts on northern bobwhite quail populations. Ecological Applications 5:632-638.

Callcott, A. A. and H. L. Collins. 1996.  Invasion and range expansion of imported fire ants (Hymenoptera: Formidicidae) in North America from 1918-1995. Florida Entomologist 79:240-251.

Forys, E.A., A. Quistorff, C. R. Allen, and D.P. Wojcik. 2001a. The likely cause of extinction of the tree snail Orthalicus reses reses (Say). Journal of Molluscan Studies 67:369-376.

Forys, E.A., A. Quistorff, and C. R. Allen.  2001b.  Potential fire ant (Hymenoptera: Formicidae) inpact on the endangered Schaus swallowtail (Lepidoptera: Papilionidae). Florida. Florida Entomologist 84:254-258.

Hillis D. M., M. T. Dixon, and A. L. Jones.  1991. Minimal genetic variation in a morphologically diverse species (Florida tree snails, Liguus fasciatus). J. Heredity 82:282-286.   

Porter S. D.,and D. A. Savignano.  1990. Invasion of polygyne fire ants decimates native ants and disrupts arthropod community.  Ecology 71:2095-2106.

Stevens, A. J., N. M. Stevens, P. C. Darby, and H.F. Percival. 1999.  Observations of fire ants (Solenopsis invicta Buren) attacking apple snails (Pomacea paludosa) exposed during dry down conditions.  Journal of Molluscan Studies 65:507-510.

Tuskes, P. M.  1981. Population structure and biology of Liguus tree snails on Lignumvitae Key, Florida. Nautilus 95:162-169.

Voss, R. S.  1976. Observations of the biology of the Florida tree snail, Liguus fasciatus (Müller).  Nautilus 90:65-69.

Yusa, Y. 2001.  Predation on eggs of the apple snail Pomacea canaliculata (Gastropoda: Ampullariidae) by the fire ant (Solenopsis geminata). Journal of Molluscan Studies 67:275-279.