The alien Moss Campylopus introflexus in the NE region of the Iberian Peninsulapopulation dynamics and impacts on vascular plants and arthropod communities

Resumen

Biological invasions are the second cause of loss of biodiversity at global scale, behind habitat destruction. Most of the biological invasions caused by plant species are due to vascular plants; however, in recent years the number of works due to the invasions caused by bryophytes is increased. Campylopus introflexus (Hedw.) Brid. is a originating from the temperate regions of the southern hemisphere, which behaves as invasive in Europe and the west coast of North America. In these regions occupy a variety of habitats such as bogs, heaths of Calluna vulgaris, sandy dunes or on the surface of old buildings, and impacts of this alien moss on biodiversity are numerous and known since long time. In the Iberian Peninsula the presence of this moss is known in areas next to Cantabrian Sea, but not in the Mediterranean region, where we recently found it in the provinces of Barcelona and Gerona. In these locations the species grows mainly on heathlands developed over siliceous soils, at altitudes up to 900 meters above sea level, where it forms dense and compact mats that cover the soil; in this carpets, Campylopus introflexus is the dominant species. We also occasionally found in other habitats, like inland dunes fixed with pines or on litter in decomposition. In all cases the species grows in places with sparse vegetation because his heliophilic preferences. There is a good knowledge about the effects of this moss on biodiversity in countries with oceanic climate; in contrast, until our work there was a lack of works investigating the impact of Campylopus introflexus in the Mediterranean region, because almost all of recordings of the species in the region are recent. This thesis attempts to describe what are the impacts of this non-native moss on different biological groups in the northeast of the Iberian Peninsula; specifically, its population dynamics during two years, its impact on germination of some species of vascular plants and its influence on communities of epigeic arthropods. In order to assess the population dynamics in spatial small-scale, permanent plots were installed and sampled every three months during a period of two years, recording coverage of Campylopus introflexus, as much as the other species of bryophytes, lichens and vascular plants. Three types of plots were Summary 6 established, regarding the initial coverage of Campylopus introflexus (low density, high density and disrupted plots experimentally). During the two years of the experiment, we have observed no significant expansion of the alien moss at local scale, because his cover had not increased in any treatment. Many parcels were removed during the monitoring, but coverage C. introflexus remained constant, although the global cover of native cryptogams decreased. Therefore, these results suggest that C. introflexus behaves as a pioneer species in a similar way than is described in other European countries, which takes advantage of disturbances in soil to settle and form dense carpets. We have also studied the phenology of the reproductive structures, recording in each seasonal sampling the presence of archegonia, propagules and capsules. Archegonia appeared mainly during spring and summer, while the propagules were observed mainly in autumn and winter. We believe this temporal segregation is due to the inability to simultaneously produce the two types of structures. The capsules, however, showed no seasonal pattern. We also studied the effect of carpets of C. introflexus on the germination of ten species of shrubs, common in siliceous shrublands where grows the alien moss: Calicotome spinosa, Cistus albidus, C. monspeliensis, C. salviifolius, Erica arborea, E. scoparia, Lavandula stoechas, Rosmarinus officinalis, Sarothamnus arboreus and Spartium junceum. Performing a germination experiment in a greenhouse, we evaluated the effect of the presence of carpets of C. introflexus on seed germination and seedling growth and establishment, as well as the influence of the water regime misture (drought vs. humidity) and the interaction between this two factors (substrate and water regime). Moss carpets reduced germination Lavandula stoechas, while Cistus albidus and Sarothamnus arboreus had higher germination in presence of moss carpets. However, in C. albidus, C. monspeliensis, Lavandula stoechas and Rosmarinus officinalis, carpets of C. introflexus caused a reduction in root growth and thus less capacity to resist the summer drought. This reduction in growth is due to the physical resistance to root penetration offered by the mats of alien moss. In a second field experiment we evaluated the effect of carpets of C. introfl