Keystones species in the functional space of plant traits
We found higher keystone plant species scores in warmer environments (i.e. 0.41 on average for study sites located <1050 m; Appendix S1, Table S2) than in colder environments (i.e. 0.26 on average for sites located >2000 m; Appendix S1, Table S2). The keystone scores were generally low, with the removal of a single plant species resulting, on average, in less than one insect secondary extinction (Appendix S1, Table S2). The top 10 keystones species retrieved from alpine and lowland trophic networks had same dietary preferences for botanical groups, as illustrated by their similar distribution patterns within the functional space of the plant traits (Fig. 3). In both warm and cold environments, the top 10 keystone species occupied the functional space characterized by high punch values (to the maximal extent of this axis; Fig. 3). The top three keystone species of warm and cold environments all belonged to the Poaceae family (Appendix S1, Table S2). Forb keystone species were located in the functional space along the opposing axes of C/N, LDMC vs . SLA in both low- and high-elevation networks; while legume keystone species were mostly distributed along the SLA trait axis, at high but not at low elevation (Fig. 3).