Unraveling the mechanisms determining the diversity of tropical plant communities: examples from the early diverging land plants
Zusammenfassung der Projektergebnisse
Understanding the causes that led to the evolution of the enormous species number of plants and animals in the tropics is one of the longest standing and at the same time most current topics in biological research, covering phyologenetic, ecological and biogeographical aspects. In the last two decades, exciting new theoretical (e.g., null models, community phylogenetics) and methodological (e.g., molecular phylogenetics, fingerprinting) developments have opened whole new avenues for this biodiversity research. With a research background of over two decades on diversity patterns and phylogenetics of early diverging land plant lineages, we designed a project that aimed at applying these new approaches to bryophytes and ferns, divided into two subprojects: While one subproject focusses on the family Cyatheaceae (scaly tree ferns) at a global scale, the focus of the present study at Bonn addressed the bryophyte lineages. We applied community phylogenetics to all species of liverworts, mosses, and ferns recorded in 132 standardized survey plots along three tropical elevational transects in humid tropical forests in Ecuador, Uganda, and New Guinea. The field work resulted in over 4,700 samples collected along the three transects. However, thanks to scrutinous taxonomic work by seasoned specialists for mosses and liverworts, we were able to get several species per bryophyte sample on average. In Uganda alone, our collection included a total of 119 species, subspecies and varieties from 19 families. No fewer than 16 species were new records for the country. This is still poor compared to the known numbers of bryophyte species in Ecuador (ca. 1660 spp.) and Papua New Guinea (ca. 600 spp.). The absolute species count in our sampling will likely rise because we finished the taxonomic survey so far only for the liverworts; our collection of mosses, containing globally twice as many described species than the liverworts, may contain even more hidden species per sample. This is due to the fact that a superficially homogenic moss cushion is a microcosm in itself, harboring smaller bryophytes and other plants hidden within, which are only detected either by time consuming taxonomy or in the molecular lab. Our results further corroborate the long held notion that bryophytes like liverworts and mosses serve as easily observable and reliable bio-indicators. In Ugandan forests we found that epiphytic liverwort richness predicts many macro-climatic variables like annual mean temperature and precipitation, and will thus mirror any climate change that occurs on short term by rapid diversity turnover and species loss. This may also be true for other tropical regions, as the overall patterns of species richness is the same along each of our transects; the hump-shaped maximum situated at middle elevations is like a focal point where changes in species richness and abundance are most easily observed. Most of the tropical bryophytes are epiphytes, and in the case of the liverwort genus Metzgeria, we were able to show that the radiation of this group into speciose, predominantly epiphytic lineages follows in time the radiation of angiosperm lineages in the Cretaceous. With our ample sampling, we will be able to create comparative phylogenies that further test the hypothesis that the establishment of angiosperm dominated, tropical broad leaved forest had a positive effect on the speciation in all land plant lineages. Our project is a perfect example how important species and taxonomic knowledge is to assess biodiversity and to provide evolutionary models for the next generation. Unfortunately, the taxonomic experts are not fostered anymore in our current scientific environment and funding system, which leads to a great loss in the analyses and interpretation of biodiversity related analyses.
Projektbezogene Publikationen (Auswahl)
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(2016). Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints. Ecology Letters 9: 1009-1022
Colwell, R.K., Gotelli, L.A. Ashtone, J. Beck, G. Brehm, T.M. Fayle, K. Fiedler, M.L. Forister, M. Kessler, R.L. Kitching, P. Klimes, J. Kluge, J.T. Longino, S.C. Maunsell, C.M. McCain, J. Moses, S. Noben, K. Sam, L. Sam, A.M. Shapiro, X. Wangu, V. Novotny
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(2020). Different predictors shape the diversity patterns of epiphytic and non-epiphytic liverworts in montane forests of Uganda. Frontiers in Plant Science 11: 765
Maul, K., Wei, Y-M., Nebel, M., Luebert, F., Ho, B-C., Quandt, D, Kessler, M.
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(2020). Functional diversity in ferns is driven by species richness rather than by environmental constraints. Frontiers in Plant Science 11: 615723
Aros-Mualin, D., Noben, S., Karger, D., Carvajal-Hernández, C., Salazar, L., Hernández- Rojas, A., Kluge, J., Sundue, M., Lehnert, M., Quandt, D. Kessler, M.
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(2021). Phylogenetic diversity of ferns reveals different patterns of niche conservatism and habitat filtering between epiphytic and terrestrial assemblages. Frontiers of Biogeography 13(3)
Hernandez-Rojas, A., Kluge, J., Noben, S., Reyes Chávez, J., Krömer, T., Carvajal- Hernández, C., Salazar, L., Kessler, M.
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(2021). The evolution and biogeographic history of epiphytic thalloid liverworts. Molecular Phylogenetics and Evolution 165
Bechteler, J., Schäfer-Verwimp, A., Glenny, D., Cargill, D.C., Maul, K., Schütz, N., von Konrat, M., Quandt, D., Nebel, M.
