Mistreated native plants or overlooked invaders?

Scientists agree in considering plant invasions as one of the worst threats to conservation of wilderness as well as to human health and economy. However, the efforts against invasions are too often frustrated by the uncertainty in assessing the native status of a plant. In fact, especially in countries that have a long history of human presence and are fully industrialized, it is almost impossible to recognize with certainty introduced plants from native ones, when they appear by then completely adapted to the wild. This problem is especially serious in south-western Europe and in Italy, where the number of the so-called “doubtfully native” (otherwise called “cryptogenic”) plant taxa is high. In many cases, our knowledge of the native status of a plant is very poor, while phytogeographical and floristic data give evidence that the native or alien status of several species needs to be clarified, especially for biodiversity conservation and the management of possible impacts. Some species of uncertain origin are often regarded as naturalized, or even as invasive aliens, and are therefore considered as a threat to biodiversity. Various of these putative aliens, however, when subjected to a careful scrutiny, may reveal themselves as fully indigenous and sometimes worth of protection. On the contrary, some species which are traditionally indicated as rare natives may be later discovered as deliberately or accidentally introduced. Evidently, any re-assessment of the native status can strongly improve allocation of efforts and resources in both controlling aliens and protecting native plants when needed. A project funded by the University of Naples “Federico II” (UTOPIAN: Unravelling Timespan and Origin of Plants in Italy: Aliens or Natives?) is focused on cryptogenic plants and is based on the study of selected model species. In the framework of this project, we are studying three different cases based on three vascular plants occurring in Italy: an invasive aquatic perennial, which might be on the contrary native to the Mediterranean region (Hydrocotyle ranunculoides L.f., Apiaceae); an annual species almost univocally regarded as native to Italy but possibly accidentally introduced (Cephalaria joppensis (Rchb.) Coult., Caprifoliaceae), and an ornamental woody species of much debated origin (Styrax officinalis L., Styracaceae). Hydrocotyle ranunculoides is generally regarded as native to Americas and reported among the most aggressive invasive species of the fresh waters in the Old World. However, according to some authors, the species would be native to the Mediterranean. Historical documents report its presence in southern Italy since the early XVII century, where it was later known as H. natans Cirillo and, until few decades ago, was considered a very rare and endangered plant. Cephalaria joppensis infrequently occurs in southern Italy and Sicily in man-managed environments, especially fields margins. The plant is more common in the Eastern Mediterranean Basin with a completely disjunct areal: some authors suggested that this plant was introduced in Italy in conjunction with crops. Finally, Styrax officinalis has an E-Mediterranean distribution (Balkans and W Minor Asia), with scattered localities in western Central Italy, where it has been often regarded as a native (possibly as a relic of Pleistocene glaciations). According to a different interpretation, however, it was possibly introduced into Italy in Roman Age and naturalized as an archaeophyte. The work is being carried out by field investigations, which include collection of voucher specimens and associated information on vegetation and ecology. Herbarium specimens from worldwide herbaria have been obtained for molecular investigations (Sanger sequencing). Data analysis will focus on identifying rare haplotypes and ribotypes to develop phylogenetic and phylogeographic inferences.