Plant species natural history
In order to assess natural variation in constitutive plant chemical
defences along elevational gradients, we sampled 14 species ofCardamine , out of the 19 currently growing in Switzerland
(Aeschimann et al. 2004). Together, all species encompass almost
a 3000 m elevational gradient of the Alpine ecosystem. During the
radiation of the group, species have colonized a wide range of habitats,
including dry and wet alpine meadows, forests and riverbanks, and
growing between 300 m above sea level (m a.s.l.) (e.g. C.
bulbifera ) and more than 3000 m a.s.l. (e.g. C. alpina ). In the
field Cardamine plants are predominantly attacked by leaf chewers
such as Pieridae butterflies, flea beetles, aphids, and slugs (Rasmann
S., personal observations), and previous work has highlighted a steady
decline in herbivore damage with elevation (Pellissier et al.2016; Defossez et al. 2018). The phylogenetic relationships
between plants was pruned from a well-resolved and dated phylogeny of
European plant species (Durka & Michalski 2012) using the apepackage (Paradis et al. 2004).