Abstract

A cryptic invader of the genus Persicaria has recently increased in the damper, northern parts of La Palma and Gran Canaria in the Canary Islands (Spain) and locally behaves as an invasive species. Examination of historical herbarium specimens showed this species to be present in Gran Canaria since the 1960s and the same probably applies to La Palma. Up to now, this species had been assigned to the Old World weed P. maculosa. However, morphologically, these plants clearly correspond with P. hydropiperoides, a common and widespread weed native to the New World, and indeed morphologically similar to P. maculosa. Diagnostic features for these two species, as well as for another similar species (P. decipiens, originally described from the Canary Islands), are compared, thoroughly discussed, and copiously illustrated. The current distribution, ecology, and naturalization status of P. hydropiperoides in the Canary Islands are also assessed. The variability of P. hydropiperoides is discussed, more precisely the taxonomic position of a southern ‘race’ of it that is sometimes referred to as a distinct species, P. persicarioides, and to which the Canarian plants belong. The taxonomic value of the latter appears to be clear, although at a lower level. A new combination, at varietal rank, is proposed and validated. In addition to our morphology-based study, a molecular phylogenetic analysis has been conducted on the nuclear ITS region and the plastid DNA region trnL-F.

Highlights

  • The generic limits of Persicaria (L.) Mill. were controversial for quite a long time

  • A thorough investigation proved these plants to belong to the American species Persicaria hydropiperoides (Michx.) Small, and more precisely to a southern ‘race’ formerly separated as P. persicarioides (Kunth) Small

  • The following description is entirely based on plant material from La Palma and Gran Canaria: Persicaria hydropiperoides (Michx.) Small, Fl

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Summary

Introduction

The generic limits of Persicaria (L.) Mill. were controversial for quite a long time. Cryptic invasions are defined as the invasion of non-native species that goes unnoticed due to misidentification as a native or another invasive species [23] As a result, such events are difficult to recognize and, despite being likely widespread, often go undetected. Jarić et al [24] recently emphasized the importance of crypticity in biological invasions: they may blur invasion impacts and reduce their predictability, since the impacts are often only detected in retrospect and understood with delay, long after control measures would have been effective They concluded that considering crypticity in biological invasions would strongly enhance the efficiency of monitoring and management planning.

Materials and Methods
Based on Morphological Data
Phylogenetic Analyses
Primary and Secondary Distribution
Habitat and Ecology
Biostatus in the Canary Islands
Discussion and Conclusions
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