What is the potential of spread in invasive bryophytes?

Abstract

Although the number of invasive bryophytes is much lower than that of higher plants, they threaten habitats that are often species rich and of high conservation relevance. Their potential of spread has, however, never been determined. Here, we assess whether the three most invasive bryophyte species shifted their niche during the invasion process and whether the extent of the study area defined to calibrate the model (geographic background, GB) affects model transferability. We then determine whether ecological niche models (ENMs) developed in their native range can be projected in other areas to assess their invasive potential. The macroclimatic niches of Campylopus introflexus, Orthodontium lineare and Lophocolea semiteres were compared in their native range (Southern Hemisphere) and in their invasion range (Northern Hemisphere) using ordination techniques. ENMs from an ensemble model were calibrated in the native range and projected onto the Northern Hemisphere using different GBs. No evidence for niche expansion in the invaded range was found and the species occur in the invaded range under climate conditions that are similar to those in the native range. The performance of the models to predict occurrences in the invaded range increased with the extent of the GB. The potential range of all species included entire regions on continents where they are still absent. The expansion of the investigated species appears to be constrained by climate conditions that are similar to those currently prevailing in their native range, which is consistent with our failure to demonstrate macroclimatic niche shift in the invaded range. The use of large GBs is recommended in such vagile organisms with large, disjunct distributions. The models indicated that invasive bryophyte species might become a threat in central and eastern Europe, North America and eastern Asia if accidentally introduced or naturally dispersed.

Regional Bans on Wild‐Bird Trade Modify Invasion Risks at a Global Scale

“…To reduce problems related to model extrapolation, model projections were adjusted using multivariate environmental similarity surfaces (MESSs) (Mateo et al . ). Environmental suitability in highly dissimilar areas (MESS < ‐20) (Mateo et al .…”

“…Environmental suitability in highly dissimilar areas (MESS < ‐20) (Mateo et al . ) was considered to be 0 (Supplementary Figure S2).…”

A global assessment of climatic niche shifts and human influence in insect invasions

“…We allowed for variable selection and fitting to be done under default settings (as in Petitpierre et al, ; Strubbe et al, ), with all eight variables applied to each species. Prevalence weights for presence points and pseudo‐absence points were set at neutral (0.5) (Mateo et al, ; Petitpierre et al, ). Models were trained on the native and native + invasive ranges for each species, with training data split for 70% training and 30% test data, and this was repeated 10 times for each modelling algorithm, giving a total of 40 model iterations per species, training extent and background.…”

“…The ability of ENMs to accurately predict non‐native ranges relies on adequately sampled distribution data, and inherently makes assumptions of climate equilibrium and niche conservatism (Mateo et al, ). Species that occur in all available suitable climates are said to be in equilibrium with climate (Petitpierre et al, ; Wiens et al, ).…”

Incorporating movement in species distribution models

“…These conceptualizations of M within the BAM framework have led to an increased understanding of model interpretation, (Barve et al 2011;Saupe et al 2012;Qiao et al 2015), with a number of studies explicitly acknowledging M when defining modelling extent, pseudo-absence selection or model validation (Belaire et al 2014;Escobar et al 2104;Strubbe et al 2015;McQuillan and Rice 2015;Mateo et al 2015;Bradley et al 2015).…”