Model species
We modeled the metapopulation dynamics of five generalized model species of insects
having different characteristics regarding mean dispersal distance and substrate requirements:
a ‘‘normal’’ (i.e., average) species, a long-distance disperser, a short-distance disperser,
a closed forest specialist and a sun-exposure specialist (Table 1). Furthermore, due
to poor empirical knowledge about local extinction risks and turnover rates, we modeled
four additional species to explore the sensitivity to the local extinction risk parameters. All
species were dependent on dead wood of Norway spruce being younger than 10 years and
having a diameter[10 cm. Young dead wood is an important substrate, especially for
saproxylic insects living under bark, because almost a half of Norway spruce dead wood is
without bark after 10 years [calculated from data presented in Ranius et al. (2003)]. The
inner bark and subcortical space of dead trees is an important microhabitat; among 542
saproxylic red-listed invertebrates in Sweden, 168 (31%) are directly dependent on bark as
a microhabitat (Jonsell et al. 1998).