Bryophyte community assembly on young land uplift islands – dispersal and habitat filtering assessed using species traits
(English)Manuscript (preprint) (Other academic)
The combined challenges from rapid landscape transformations and climate change have actualize the need to understand community assembly processes in order to efficiently conserve threatened species in changing landscapes. In this study we focus on community assembly in bryophytes and use species traits to examine habitat filtering and dispersal limitation during colonization of islands recently created by land uplift processes in the Bothnian bay in northern Europe. The bryophyte floras of 20 islands differing in age, area, connectivity and habitat composition were assessed through field inventories and we compiled information across several sources to create a list of all species in the regional species pool. Data on traits related to habitat affiliations (substrate, light, moisture and pH) and dispersal/colonization ability (e.g regional abundance, spore size, sporophyte frequency) were collected and, for 420 species (94% of the regional pool) with available data, we used multivariate models to compare trait effects on species occurrence probabilities across the 20 islands. We found that occurrence probabilities depended strongly on the availability of different habitats across the islands and that regionally rare species and predominantly asexual species had sharply reduced probabilities of being present on islands compared to regionally abundant and /or sexual species, Having specialized asexual propagules had a positive effect on occurrence probabilities, but compensated only partly for the reductions in asexual species. No effects of spore size were detected. A comparison of trait effects on occurrence probabilities across island connectivity and area gradients, revealed reduced habitat filtering on larger islands and that the negative effects on occurrence probabilities in the asexual species decreased with island connectivity. An absence of connectivity relationships for sexual species, suggest that their colonization is regulated by habitat availability and the contributions of each species landscape level spore output to a “regional spore rain” from which species recruited. Conservation strategies, aimed at conserving and increasing the frequency of regional propagule sources, irrespective of their spatial configuration, could therefore be useful in this group. For asexual species, our results instead suggest a strategy aimed at spatially concentrating the conservation and restoration of habitats in order to increase metapopulation persistence.
Research subject Ecological Botany; Conservation Biology
IdentifiersURN: urn:nbn:se:umu:diva-121236OAI: oai:DiVA.org:umu-121236DiVA: diva2:932304
FunderSwedish Research Council Formas, 215-2010-998