Effects of Soil Characteristics, Allelopathy and Frugivory on Establishment of the Invasive Plant Carpobrotus edulis and a Co-Occuring Native, Malcolmia littorea

Abstract

BackgroundThe species Carpobrotus edulis, native to South Africa, is one of the major plant invaders of Mediterranean coastal ecosystems around the world. Invasion by C. edulis exerts a great impact on coastal habitats. The low number of native species in invaded communities points to the possible existence of mechanisms suppressing their germination. In this study we assessed whether soil factors, endozoochory, competition and allelopathic effects of the invader affect its own early establishment and that of the native species Malcolmia littorea. We used laboratory solutions representing different chemical composition and moisture of the soil, herbivore feeding assays to simulate seed scarification and rainwater solutions to account for the effect of differently aged C. edulis litter.Principal FindingsWe show that unlike that of the native species, germination and early growth of C. edulis was not constrained by low moisture. The establishment of C. edulis, in terms of germination and early growth, was increased by scarification of seeds following passage through the European rabbit intestines; the rabbits therefore may have potential implications for plant establishment. There was no competition between C. edulis and M. littorea. The litter of the invasive C. edulis, which remains on the soil surface for several years, releases allelopathic substances that suppress the native plant germination process and early root growth.ConclusionsThe invasive species exhibits features that likely make it a better colonizer of sand dunes than the co-occurring native species. Allelopathic effects, ability to establish in drier microsites and efficient scarification by rabbits are among the mechanisms allowing C. edulis to invade. The results help to explain the failure of removal projects that have been carried out in order to restore dunes invaded by C. edulis, and the long-lasting effects of C. edulis litter need to be taken into account in future restoration projects.

Allelopathic effects of Sonchus oleraceus L. on the germination and seedling growth of crop and weed species

“…The rate of seed germination decreased in parallel with increasing concentrations of the extract. Previous studies have demonstrated that allelopathic plants can affect the germination indices (G T and A S ) and seedling growth of many target species (Hussain et al 2011;Novoa et al 2012). Increasing the inhibitory effect by altering the extract concentration is in accordance with previous studies (Hussain et al 2011;Gomaa & AbdElgawad 2012).…”

The impact of Carpobrotus cfr. acinaciformis (L.) L. Bolus on soil nutrients, microbial communities structure and native plant communities in Mediterranean ecosystems

“…The flowers are frequently visited by native pollinators (Bartomeus et al 2008), seed production is particularly abundant, reaching an average of 1000 seeds per fruit (Carta et al 2004; Bartomeus and Vilà 2009), and a high proportion of seeds is stored in the soil seed bank and in litter (Chenot et al 2014). Seed dispersal is then carried out mainly by small mammals such as rats and rabbits, whose ingestion causes an increase in the germination percentage and therefore the chance for new individuals to become established (D'Antonio 1990a;Bourgeois et al 2005;Novoa et al 2012).…”

“…invasive success (D'Antonio 1990b(D'Antonio , 1993D'Antonio et al 1993;Novoa et al 2012) and to assessing the ecological consequences associated with their invasion on floristic richness and diversity (Carta et al 2004;Vilà et al 2006;Andreu et al 2010;Novoa et al 2013;Chenot et al 2014;Fried et al 2014), on soil properties (Vilà et al 2006;Conser and Connor 2009;de la Peña et al 2010;Santoro et al 2011;Novoa et al 2013 or on both (Vilà et al 2006;Novoa et al 2013). In all previous references, Carpobrotus spp.…”

Distribution of alien species along sand dune plant communities zonation

“…Some invaders, such as Carpobrotus edulis, affect the community composition, diversity and succession via modification of the soil properties. It has been shown that the effect of C. edulis on pH and nitrogen compounds persists over time even after Carpobrotus removal (13,14). This suggests a possible allelopathic effect of its litter (14).…”

“…It has been shown that the effect of C. edulis on pH and nitrogen compounds persists over time even after Carpobrotus removal (13,14). This suggests a possible allelopathic effect of its litter (14). Clonal growth has recently been indicated as an attribute that could contribute to the invasiveness of plants (15,16).…”