FIGURE 1 (a) Map and geographical location of the edaphic
islands on rocky outcrops in the Czech Republic, Central Europe
(red-filled circle in the inset); black-filled circles correspond to the
studied edaphic islands, while the white circles represent all the
edaphic islands in the surrounding landscape. (b) Example of one edaphic
island embedded in the agricultural landscape, and (c) a closer look at
the studied shallow-soil, acidophilous temperate dry grassland. Photo
credit: FE Méndez-Castro.
We focused on 13 perennial plant species confined to the discrete
outcrop grasslands, constituting ~45% of the total
number of specialist species of this vegetation type (Méndez-Castro et
al., 2021). These specialist species should be: 1) adapted to the harsh
environment of rocky outcrops (especially concerning the putatively
strong edaphic filter), and 2) more affected by insularity than
non-specialists (for which the surrounding landscape should not be as
inhospitable; Conti et al., 2021; Méndez-Castro et al., 2021). The
selected species belong to different plant functional types (9 forb
species, 2 chamaephytes, 1 grass, 1 sedge), and life histories (5
clonal, 8 non-clonal species). The clonal species are Carex
caryophyllea, Cerastium arvense, Hieracium pilosella, Koeleria
macrantha, and Trifolium alpestre , whereas the non-clonal
species are Carlina acaulis, Centaurea stoebe, Helianthemum
grandiflorum subsp. obscurum, Knautia arvensis, Lychnis viscaria,
Scleranthus perennis, Silene nutans, and Thymus pulegioides .
Hereafter, we refer to these species using their genus name. Species
were found in the majority of the edaphic islands (i.e. 12 to 20
islands), except for Helianthemum (6) and Carex (9).