Geographic variation among Iberian communities of the exotic halophyte Cotula coronopifolia

Abstract

The exotic annual forb Cotula coronopifolia has locally invaded salt marsh communities naturally dominated by Spergularia marina along large parts of the Iberian coastline. While the floristic composition of C. coronopifolia dominated communities on the Atlantic coast of northern Portugal has already been described, this information was missing for the southern part of the country. We carried out a phytosociological study at 21 sites along the south-western and southern coast of mainland Portugal to determine the ecology and syntaxonomical status of these communities, and to compare them to the Atlantic ones. Plant communities co-dominated by C. coronopifolia and S. marina were generally found in the sub-halophilous inner part of salt marshes. They occupied gaps within taller perennial vegetation (Juncus maritimus formations), such as small pools temporarily inundated with brackish waters. Southern communities differed from the northern ones by the high abundance of Triglochin barrelieri and the absence of salt-intolerant species that are present in the Atlantic communities. This difference may result from the drier summer climate in southern regions, leading to intense water evaporation and thus, more saline conditions. We propose to classify the Mediterranean communities in a new association, the Cotulo coronopifoliae-Triglochinetum barrelieri. High abundance of Limonium diffusum further allowed the distinction of a new subassociation limonietosum diffusi for the southernmost part of Portugal. Results show that invasive exotic plants can form new phytosociological associations with a characteristic species composition, but that these community types, despite being dominated by the same invader, still show ecological and geographical differentiation.

Genetic diversity and geographic differentiation analysis of duckweed using inter-simple sequence repeat markers

“…The results indicated that geographic region had significant influence on the populations' genetic diversity. These results correspond with the report of Bergmann et al that large differences among geographic isolates of duckweeds were found when they selected superior duckweed (Lemnaceae) genotypes for the utilization of nutrients in animal wastes [32], and the geographic differentiation of some other plants [33][34][35][36]. Different communities may have resulted in the significant genetic differentiation between duckweed populations; local selective forces may greatly affect genetic diversity within duckweed populations.…”

Biogeography of salt marsh plant zonation on the Pacific coast of South America

“…Disturbances, such as tsunamis and floods that frequently occur in Chile, may also be important (Fariña & Camaño, 2012). Cotula coronopifolia, for example, is found to be associated with tsunamis disturbance, and also colonizes gaps in tall perennial vegetation (Costa, Neto, Ars enio, & Capelo, 2009 Bertness, Cough, & Shumway, 1992;Bertness & Ellison, 1987). In arid higher latitudes, lowered high-marsh salinity stress due to increased precipitation allows S. fruticosa to occupy the entire marsh.…”

The impacts of land-use changes on the recovery of saltmarshes in Portugal

“…The presence is estimated in percentages of a species and classified according to a chosen scale into a set of 'classes of presence'. The classes were defined as follows (Costa et al, 2009): r (< 6%); + (6-10%); I (11-20%); II (21-40%); III (41-60%); IV (61-80%); V (> 81%).…”