Morphological variations of natural populations of an aquatic macrophyte Elodea nuttallii in their native and in their introduced ranges.
Résumé
Introduced plant species appear often more vigorous than their conspecifics in the native range. We investigated the morphological variations of Elodea nuttallii (Planch.) St John and its behaviour in its native and in its introduced habitats. We assessed eight morphological traits of 24 populations in the native North America range and 16 populations in the introduced European range. The introduced taxa can be very distinct in their growth form and size from counterparts in their native range. The shorter broaded-leaved phenotype typically occurs in shallow streams, whereas the longer spacer narrow-leaved phenotype occurs in lakes. Larger leaf width and higher number of lateral shoots - when nutrients are not limiting- may enhance plant performance. The European populations grow more vigorously than their American relatives, possibly because of different selection pressures.