Original paper
The Asplenium ceterach complex (Aspleniaceae, Polypodiopsida) on Rhodes and Chalki (Greece) – with an overview of its Euro-Mediterranean range
Kummer, Volker; Viane, Ronnie; heede, Caroline Van den; Welk, Erik; Fuchs, Jörg; Scheffel, André; Bennert, H. Wilfried
90 references
published online: May 27, 2025
manuscript accepted: Apr 30, 2025
manuscript revision requested: Apr 1, 2025
manuscript received: Feb 23, 2025
Abstract
In Europe, Asplenium subgenus Ceterach represents an autopolyploid complex consisting of three species with different ploidy levels (diploid, tetraploid, and hexaploid), along with two hybrids (triploid and pentaploid). As part of a comprehensive floristic survey of cormophytes on the islands of Rhodes and Chalki, living specimens of subgenus Ceterach were collected, and their ploidy levels were determined through flow cytometric analysis. For certain samples, where flow cytometry was not applicable, ploidy levels were inferred based on spore size measurements. Three taxa were identified: the tetraploid A. ceterach, the hexaploid A. cyprium, and the pentaploid hybrid A. ×troodeum. A map depicting the distribution patterns of all taxa found on Rhodes and Chalki in 2015 and 2016 is provided. Asplenium cyprium is the most common taxon on both islands, while A. ceterach s.str. is less abundant. The pentaploid hybrid A. ×troodeum is rare. In the study area, these plants typically colonize fissures in limestone rocks along paths or within the phrygana vegetation, with less frequent occurrences on limestone walls or serpentinite rocks. They prefer habitats that are north- to west-facing and shaded to varying degrees. We also present a more general distribution map for the entire Euro-Mediterranean region, based on earlier versions by Meusel et al. (1965) and Jalas & Suominen (1972), which primarily distinguished the diploid and tetraploid cytotypes. This map is supplemented with data from GBIF and additional occurrences gathered from the literature. Recent data on cytotype distribution, in the context of the geographical range of the complex, were obtained through extensive fieldwork conducted over the past few decades (mostly by R.V.), resulting in many new records of cytotypes within the Asplenium ceterach complex. This includes data from regions such as Spain, Italy, Greece, and North Africa (Algeria).
Keywords
Autopolyploidy • hybridization • flow cytometry • nuclear genome size • cytotype distribution • Rhodes flora • Mediterranean flora