The Salvinia auriculata complex is a group of four similar species that share the common and defining character of “egg-beater like” hairs (figure 1). The upper surfaces of floating leaves are covered with rows of papillae (columnar projections) topped with four hairs which rejoin at the tip to form the “egg-beaters”.

Salvinia auriculata Aublet, Salvinia molesta D.S. Mitchell, Salvinia herzogii de la Sota and Salvinia biloba Raddi make up the S. auriculata complex. The floating leaves of all four are orbicular to ovate. Those of S. auriculata, S. herzogii and S. biloba usually range from 1.5 – 2 cm long and 1.8 – 2.5 cm wide.  The floating leaves of Salvinia molesta are larger, potentially reaching 4 cm long and 5 cm wide at maturity.

Within the S. auriculata complex species are distinguished by sporocarp bearing plants as follows:

Salvinia auriculata: Stalk of submersed leaf usually sessile to subsessile, immediately dividing into 2 to 3 horizontal trunks which recurve upwards (figure 2). (Stalk occasionally reaching lengths of 10 cm before dividing into trunks). Branches extending to 1.5 cm long off the main trunks, terminating in sporocarps held at the same level (cymose) (figure 3). Sporocarps carried on stalks 1 - 12 mm long, spherical or globose, not pointed.

Salvinia biloba: Stalk of submersed leaf reaching 0.2 – 1 cm before dividing into many branches. Branches open, to 2 - 5 cm long (figure 4a, 4b) bearing alternately arranged sporocarps. Sporocarps carried on stalks 3 -10 mm long, globose, pointed at the tip.

Salvinia herzogii: Stalk of submersed leaf usually extending 0.2 – 1.4 cm long before dividing into many branches.  Branches bearing alternately arranged sporocarps vary considerably from appearing compact and recurved, 0.8 – 1 cm long, when sporocarps are closely placed (figure 5a) to 1.2 – 2.2 cm long and more spread out when sporocarps are more widely spaced (figure 5b). Sporocarps carried on very short stalks, < 1 mm, ovoid, pointed at the tip.

Salvinia molesta: Stalk of submersed leaf reaching 2 - 6 mm long before dividing into many branches.  Branches extensive and long, potentially reaching 5 cm or longer, bearing evenly placed, alternately arranged sporocarps when fully matured. Sporocarps sessile or carried on very short stalks, < 1 mm, ovoid, pointed at the tip.

Their Native Ranges:

Salvinia auriculata: Trinidad, Guyana, Brazil, Paraguay, and Argentina.
Salvinia biloba: Espirito Santa and Rio de Janeiro, southeast Brazil.
Salvinia herzogii: Paraguay, Uruguay, southern Brazil and northern Argentina.
Salvinia molesta: Southeast coast of Brazil.

Comments:

Salvinia molesta is the only species within the S. auriculata complex that has become established in the United States having been introduced through the horticultural trade.

Salvinia auriculata has not been documented in the horticultural trade in recent times and there are no records of either S. biloba or S. herzogii having ever been carried into horticultural cultivation.

References:

Forno, I.W.  1983. Native distributions of the Salvinia auriculata complex and keys to species identification.  Aquatic Botany 17:71-83.

Mickel, J.T. and A.R. Smith. 2004.  The Pteridophytes of Mexico.  Memoirs of The New York Botanical Garden 88:546-547.

Mitchell, D.S. and Thomas, P.A.  1972. Ecology of waterweeds in the Neotropics.  UNESCO Technical Papers in Hydrology, No. 12. pp. 13-21.

*Salvinia auriculata, Salvinia biloba and Salvinia herzogii illustrations redrawn from Forno, I. W. 1983.  Native distribution of the Salvinia auriculata complex and keys to species identification. Aquatic Botany 17:71-83.

Figures 1 - 5 page.

Authors: M.M. Richerson and C.C. Jacono

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