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219 Exotic and Invasive Species 13 Exotic and invasive species are a big conservation problem of our time, a consequence of habitat disturbance , global trade and travel, and the relentless tendency of any species to reproduce to the utmost when given the opportunity (as first pointed out in 1859 by Charles Darwin, who described examples of exotic species explosions in The Origin of Species). Since 1800, many organisms have entered or been brought into Indiana and established viable populations. Undoubtedly , many others have entered the state and failed to establish, though this is rarely documented. Flora There are about 800 exotic plant species in Indiana, including some highly detrimental invasives; the most troublesome are indicated in Table P-14. Two important exotics are garlic mustard (Figure 13.1) and purple loosestrife (Figure 13.2). The percentage of exotics among the state’s vascular plants (approximately 29%) is much higher than for any of the animal groups treated here. Exotic species have been introduced from foreign lands by intentional means, e.g., bringing in plant materials for food, building materials , medicine, ornamental use, etc., and unintentionally , such as weed seeds transported in soil or crop seed mixes. Regardless of the source, some exotics are having a tremendous, negative environmental and economic impact on the state. Fish Twenty-two exotic species of fish now inhabit the aquatic systems of Indiana (Table F-6). The striped mullet and inland silverside now occur in the state as the result of natural upstream range expansion on the Ohio River, and could be omitted from the list. They are included because the current, altered state of the Ohio River may have contributed to their range expansion , which might otherwise not have occurred. Many of the exotic fish species currently found in Indiana, such as common carp, rainbow smelt, the various species of Salmonidae, and striped bass, were intentionally stocked for recreational purposes; alewife was stocked as a forage species. The others have arrived unintentionally, the round goby via the ballast water of transoceanic vessels; the goldfish, grass carp, silver carp, bighead carp (Figure 13.3), and white catfish by escape from private waters. The sea lamprey , threespine stickleback, and white perch arrived through man-made canals/connections between normally disconnected drainages. The rudd arrived as the result of aquarium or bait-bucket release. The oriental weatherfish arrived by the three latter methods. Many exotic fish species have become invasive, with negative impacts on native species diversity and natural communities. Some, such as sea lamprey , carp, and goldfish, were established over a century ago, while invasions by bighead carp, silver carp, grass carp, white perch, round goby, and oriental weatherfish date from the early 1990s. The highest number of exotic species occurs in Lake Michigan. Although not exotic to Indiana, a host of native species are now found outside their native ranges; these non-indigenous species can be found in Tables F-2 through F-5, which list the species found in each of the aquatic systems. Amphibians and Reptiles Apparently only one species of truly exotic reptile or amphibian has become established in Indiana. The common wall lizard, an exotic from Europe, is clearly resident in at least one location along the Ohio River. It appears to have emigrated from populations upstream around Cincinnati. The red-eared slider, a natural resident in a few Indiana locations, is also now established in a variety of other places; the sources may have been completed science experiments or pets that outlived their entertainment value. Other turtle species populations have likely become established as well, such as the river cooters on the St. Joseph River. Last, the green treefrog has been found in a growing number of locations along the Indiana side of the Ohio River in the vicinity of Evansville. The sheer number of localities and the proximity of natural populations across the river near Henderson, Kentucky, suggest that this species is managing to naturally expand its range into Indiana. Birds Eight exotic species have established populations that persist currently, without human help except for ringnecked pheasant. They are listed below in taxonomic order with their source location in parentheses. 1. Mute swan (Europe), well established in Michigan, has increased as a breeding bird in Indiana at an alarming rate in the twenty-first century, spreading from the northern part of the state into the central part. 2. Ring-necked pheasant (Asia), a managed game bird, was introduced to almost all counties, repeatedly in many areas. It is best...

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