Contrasting multitaxon responses to climate change in Mediterranean mountains

Abstract

We explored the influence of climatic factors on diversity patterns of multiple taxa (lichens, bryophytes, and vascular plants) along a steep elevational gradient to predict communities' dynamics under future climate change scenarios in Mediterranean regions. We analysed (1) species richness patterns in terms of heat-adapted, intermediate, and cold-adapted species; (2) pairwise beta-diversity patterns, also accounting for its two different components, species replacement and richness difference; (3) the influence of climatic variables on species functional traits. Species richness is influenced by different factors between three taxonomic groups, while beta diversity differs mainly between plants and cryptogams. Functional traits are influenced by different factors in each taxonomic group. On the basis of our observations, poikilohydric cryptogams could be more impacted by climate change than vascular plants. However, contrasting species-climate and traits-climate relationships were also found between lichens and bryophytes suggesting that each group may be sensitive to different components of climate change. Our study supports the usefulness of a multi-taxon approach coupled with a species traits analysis to better unravel the response of terrestrial communities to climate change. This would be especially relevant for lichens and bryophytes, whose response to climate change is still poorly explored.

Figure 1

Location of the study area (a) and conceptualization of the sampling design (b,c). The elevational transect was split into ten 100 m belts (b). In each belt, 7 plots of 100 × 100 cm were randomly selected (c). Figure was produced using the open-source software QGIS 3.10.12 (https://www.qgis.org) and assembled using Adobe Photoshop CC 2018. In particular, figure (a) is based on the shapefiles freely available on the ISTAT (Istituto nazionale di statistica) website: https://www.istat.it/it/archivio/222527. The contour line in figure (b) were calculated using Contour function available in QGIS 3.10 and using a 10 m resolution DTM freely available on INGV Pisa (Istituto nazionale di geofisica e vulcanologia – Sezione di Pisa) website: http://tinitaly.pi.ingv.it/Download_Area2.html.

Figure 2

Results of the fourth corner analysis for Lichens (a), Bryophytes (b) and Plants (c). Boxes are coloured according to traits fourth-corner coefficients: red and blue indicate positive and negative significant trait-variable association respectively. Colour brightness indicates the strength of the association: brighter colour shows stronger association.