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eBook details

• Title: Salvinia Molesta in Mexico (Shorter Notes)
• Author : American Fern Journal
• Release Date : January 01, 2009
• Genre: Engineering,Books,Professional & Technical,
• Pages : * pages
• Size : 53 KB

Description

Salvinia molesta in Mexico.--The genus Salvinia Seg. comprises ten species of mostly tropical ferns that are floating aquatics or less commonly stranded on receding shorelines. Among these, perhaps the best known is S. molesta D.S. Mitchell (Kariba weed, giant salvinia, giant water spangles), which is notorious as an extremely aggressive invasive exotic in both the New and Old Worlds. This species is extremely fast growing and has the capacity to cover the surface of even large bodies of standing and slow-moving water, forming so dense a continuous mat that oxygen exchange is inhibited and light passage is precluded, to the detriment of other aquatic organisms. Because it is a sterile pentaploid (n = 45; Loyal and Grewal, Cytologia 31: 330-338. 1966), S. molesta reproduces only vegetatively by fragmentation and regrowth; thus humans, waterfowl, and surface drainage are the main dispersal agents. The taxon first came to the world's attention in the 1930s, when plants inadvertently released into a lake in Sri Lanka quickly grew into a major infestation. Subsequently, it caused similar problems in portions of Australia, India, southeastern Asia, and Africa (Moran, Fiddlehead Forum 19[4+5]: 26-28. 1992). It was not until 1972 that the taxon was correctly determined to represent an unnamed species and was described as new to science, based on plants infesting Lake Kariba, along the border between Zambia and Zimbabwe (Mitchell, Brit. Fern Gaz. 10: 251-252. 1972). In the United States, S. molesta and its relatives are considered noxious weeds under the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) and thus are prohibited by law from international import or interstate shipment. Salvinia molesta is a member of the S. auriculata Aubl. complex, which consists of four taxa, all native to South America and Trinidad (Forno, Aquatic Bot. 17: 71-83. 1983). All of these taxa (but in particular S. molesta) are considered potentially severe aquatic weeds outside of their native ranges. Forno and Harley (Aquatic Bot. 6: 185-187. 1979) were the first to discover native populations of S. molesta growing at relatively low elevations in temperate southeastern Brazil. Curiously, although the species has proliferated in the Old World tropics, it apparently has not spread significantly thus far in the neotropics (Moran, F1. Mesoamer. 1: 396-397. 1995).

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