Distribution and morphological variation of invasive Elodea nuttallii and E. canadensis in Croatia
Elodea nuttallii and E. canadensis (Hydrocharitaceae) are two macrophyte plant species native to North America and invasive alien plants within the EPPO region (Table 1). In Croatia, E. nuttallii is a relatively recent addition to the alien flora, being first identified in 2006 whereas E. canadensis has been established since 1894. The species have separate geographical distributions in Croatia where E. nuttallii is found in the Kopački rit floodplain (river Drava) and E. canadensis occurs in the Lonjsko polje floodplain which is part of the Sava River Basin. Since the first identification of E. nuttallii in 2006, spread has occurred eastwards along the drainage channel networks potentially linked to flooding events that act to link stagnant waters and channels. Species identification within the genus Elodea is aided by taxonomic characteristics in the male flowers, however, this is not possible for these two species in Europe as only female plants were introduced – hence spread is vegetative. The authors show that identification of the two species is aided by morphological differences in both leaf length and width although there is some overlap between the species in Croatia. In general, E. nuttallii had longer leaves whereas leaf width was greater in E. canadensis
Table 1. The occurrence of Elodea nuttallii and Elodea canadensis in the EPPO region*.
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Species
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EPPO countries where present
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Elodea nuttallii
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AT, BE, CH, CZ, DE, DK, FI, FR, GB, HU, HR, IE, IT, NL, NO, PL, RO, SK, SE
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Elodea canadensis
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BE, BG,CH, DE, DK, ES, FI, FR, GB, GE, HR, HU, IE, IT, LT, NL, NO, PL, PT, RU
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* The distribution of species has been checked in the Q-bank database, as well as the DAISIE, NOBANIS and PQR databases.
Sources
Kočić A, Horvatić J ; Jelaska SD (2014) Distribution and morphological variation of invasive macrophytes Elodea nuttallii (Planch.) H. St. John and Elodea canadensis Michx in Croatia. Acta Botanica Croatica 73(2), 437-446.