Local epiphyte establishment and future metapopulation dynamics in landscapes with different spatiotemporal properties

Abstract

Abstract. Understanding the relative importance of different ecological processes on the metapopulation dynamics of species is the basis for accurately forecasting metapopulation size in fragmented landscapes. Successful local colonization depends on both species dispersal range and how local habitat conditions affect establishment success. Moreover, there is limited understanding of the effects of different spatiotemporal landscape properties on future meta population size. We investigate which factors drive the future metapopulation size of the epiphytic model lichen species Lobaria pulmonaria in a managed forest landscape. First, we test the importance of dispersal and local conditions on the colonization-extinction dynamics of the species using Bayesian state space modelling of a large scale data set collected over a 10 yr period. Second, we test the importance of dispersal and establishment limitation in explaining establishment probability and subsequent local population growth, based on a 10 yr propagule sowing experiment. Third, we test how future metapopulation size is affected by different meta population and spatiotemporal landscape dynamics, using simulations with the metapopula tion models fitted to the empirical data. The colonization probability increased with tree inclination and connectivity, with a mean dispersal distance of 97 m (95% credible intervals, 5-530 m). Local extinctions were mainly deterministic set by tree mortality, but also by tree cutting by forestry. No experimental establishments took place on clearcuts, and in closed forest the establishment probability was higher on trees growing on moist than on dry mesic soils. The subsequent local population growth rate increased with increasing bark roughness. The simulations showed that the restricted dispersal range estimated (compared to non restricted dispersal range), and short tree rotation length (65 yr instead of 120) had approxi mately the same negative effects on future metapopulation size, while regeneration of trees creating a random tree pattern instead of an aggregated one had only some negative effect. However, using the colonization rate obtained with the experimentally added diaspores led to a considerable increase in metapopulation size, making the dispersal limitation of the species clear. The future metapopulation size is thus set by the number of host trees located in shady conditions, not isolated from occupied trees, and by the rotation length of these host trees.

Conservation benefits of international Aichi protection and restoration targets for future epiphyte metapopulations

“…This may increase their metapopulation viability and also occupancy inside protected areas; but is something that remains to be studied. Recent experimental and empirical data have shown that the future metapopulation size of the lichen Lobaria pulmonaria is foremost set by the number of host trees located in shady uncut forest conditions, not isolated from occupied trees, and by the rotation length of these host trees (Belinchón et al., ). Increased rotation times of existing and restored stands above a mean clear‐cut age of 120 years will likely also aid the implementation of national targets to increase the area cover of old forests (>120 years) in Sweden, although not by the target year 2020 (http://www.miljomal.se).…”

“…Stochastic extinction rates were assumed to be negligible (zero) from uncut occupied beech stands (e.g. Belinchón et al., ; Johansson et al., ; Snäll et al., ). Species‐specific connectivity measures to every suitable beech stand that could represent a potential dispersal source (based on species‐specific minimum suitable stand age, see below) were calculated and ranked.…”

“…Based on Bayesian statistical modelling of empirical, observational data collected at the studied landscape scale, five species were found to be restricted by dispersal range, while four species were not found to have restricted dispersal range (Table ; Ruete et al., ). The species specificity to old beech trees (Fritz et al., ) allowed us to assume that beech stands constitute the patches of the epiphytes’ patch‐tracking metapopulation dynamics (Belinchón et al., ; Johansson et al., ; Snäll, Ribeiro, & Rydin, ). The focal species are red‐listed according to a range of IUCN threat categories (Table ; ArtDatabanken, ) or indicator species of old‐growth forests (Norén, Hultgren, Nitare, & Bergengren, ).…”

“…Many crustose epiphytic lichens are slow‐growing and long‐lived organisms associated with high tree age (Fritz, Niklasson, & Churski, ), and their stochastic extinction rate from trees that remain standing is often negligible (e.g. Belinchón et al., ; Johansson et al., but see Öckinger & Nilsson, ; Fedrowitz et al., ). Hence, the time window when a forest constitutes a patch for epiphytes can be defined as the time between when the forest obtains the required habitat quality (e.g.…”

Discovery of long‐distance gamete dispersal in a lichen‐forming ascomycete

“…pulmonaria in the first survey, but colonized in the second survey, as offspring. However, it is also well known that a proportion of occupied trees are erroneously recorded as unoccupied, 4.4% in this study system (Belinchón et al ., ). In analyses II and III, we accounted for imperfect detection and classified some of these individuals as potential parents instead of offspring.…”