Periodic Reporting for period 2 - EPIDYN (Life on a leaf: species interactions and community dynamics in epiphyll communities)
Periodo di rendicontazione: 2018-09-01 al 2019-08-31
The highest biodiversity worldwide has been found in tropical forests, where bryophytes and lichens represent a significant amount of diversity and cover. In spite of this, due to their relatively small size and challenging identification, these organisms have been largely neglected in many ecological studies.
Tree and shrub leaves that harbour epiphyll communities (bryophytes, lichens, algae and fungi) in miniature ecosystems are an interesting model system in which to study ecological processes, precisely because epiphyll community dynamics happen quickly, during the life-span of the leaf, ensuring economy both in terms of time and resources. Due to the ephemeral character of their substrate and the small scale and relatively fast dynamics, epiphyllous communities offer an ideal system to study dynamics of primary succession and mechanisms explaining biodiversity maintenance (BM) in relation to environmental variables.
Taking a closer look, epiphyll communities can be extremely diverse, with up to 80 species of lichens on a single leaf, plus numerous species of bryophytes (mostly foliose liverworts), algae, fungi and bacteria. As in other tropical biotic communities, it is unknown why these epiphyll communities are so diverse or how biodiversity is maintained. Theoretical models of BM range from ‘neutral theories,’ where random processes explain the high degree of coexistence without counting on different species responses to the environment, to niche-based models, where interactions between species and the environment play a more central role in BM. When a new area is first colonized by plants—for example in primary succession—the course of succession may be a chance process depending on what species happen to arrive first (the ‘priority effect’); or at the other extreme, it may be highly deterministic with very specific roles (e.g. first colonizer, late-successional) or niches for each species. In all these models of BM, species interaction plays an important role, but the predicted outcomes of the interactions differ. While the priority effect implies that the first species to arrive will dominate, models including species-specific niches allow for a range of interactions, both negative (competition) and positive (facilitation). In this project, we aim to determine which are the most appropriate theoretical models for describing species interactions and successional dynamics in epiphyll communities (liverworts, lichens, algae and fungi) and how the relative role of each model depends on environmental conditions.
Species composition differed between closed forest and gap sites, and specialist species could be identified. Higher epiphyll species richness and cover were found on older leaves, which was due to an accumulation of species rather than a turnover. Lichen cover did not differ between closed forest and gaps, liverwort cover was higher in gaps. These data are compiled in the first manuscript, accepted by the Journal of Vegetation Science and published in open access. Data used in this article will be soon freely available in Dryad digital repository.
The second manuscript on epiphyll SPPs is under preparation. We analyzed epiphyll communities in four epiphyll functional groups (liverworts, lichens, algae and fungi) and found that epiphyll SPP change over time, but not between microsites (gaps vs. closed forest). Within epiphyll functional groups, we found two SPPs, aggregated and random, while between functional group pairs, in addition to aggregated and random, we also found segregated SPPs.
Part of the research results were presented in a Bambi talk on BCI, at the University of Chiriqui, at the Technological University of Panama, during bryophyte course at STRI and at Marburg University.The researcher also presented the project results in five International conferences and the researcher's oral presentation has been accepted at the British Ecological Society Annual meeting 2019 in Belfast.
The research results also received attention from the general public (school children, students, tourists) during field trips on BCI and in Punta Culebra and at the Marburg University Bryophyte course for students. A wider audience was reached with information about the project through press releases and project websites which were picked up and elaborated upon on websites and newspapers in Germany and Panama.