What drives evolutionary diversification in a biodiversity hotspot? A `next generation´ phylogenetic approach comparing three clades of the Cape Floristic Region´s mega-genus Erica
Final Report Abstract
The question of what generates biodiversity remains a longstanding classic and is yet still not adequately answered. Since Humboldt and Bonpland (1805; 1846) we know that biodiversity is unequally distributed around the globe with often high diversity in the tropics decreasing towards the poles. Mountain regions with steep ecological gradients and pronounced habitat heterogeneity are unusually diverse, especially in the tropics. Centres of plant diversity outside the tropics, such as the Mediterranean ecosystems, contribute to the uneven distribution in space. Similar to the geographic patterns, diversity is unequally distributed among groups, with radiating lineages often attended by species-poor successive sister clades. In this project, we studied the evolution of biodiversity using its simplest quantity: species richness. We focused on a flowering plant clade, Erica (heathers) that shows tremendous differences in species richness among its lineages and that is an iconic member of the fynbos flora of the Cape Floristic Region (CFR) of South Africa, one of the Mediterranean biodiversity hotspots. We tested hypotheses that might explain the incredible diversity of heathers in the CFR. We conducted weeks of fieldwork observing and documenting over 1260 plants, collected more than 700 herbarium specimens and leaf tissue samples, and curated a database of over 65 000 geo-referenced observations. We DNA sequenced three complete genomes, 295 samples by Hyb-Seq, 66 by GBS, and 525 Sanger sequenced, together covering about 425 species. During the project, we also brought together various experts to join forces for Erica-specific conservation actions and founded the Global Conservation Consortium for Erica (GCC Erica). To address our project-specific questions, we reconstructed phylogenetic trees at different evolutionary scales: genus, species, and below species level. Genomic markers and bioinformatic tools were newly developed to suit our purposes. This allowed us to investigate the age and the biogeographic origin of Cape Erica. We tested for likely factors proposed as potential causes of the high plant diversity of the CFR, principally those relating to shifts in geographic range, ecological niche, and pollinators. Taken together, a highly dynamic picture of Cape Erica’s evolution is emerging that points towards geographic features – dissected ‘sky island’ topography in the CFR, spatial distance, and altitude differences – setting the stage for intensified initial speciation (in isolation). Ecological adaptations dynamically interrelate possibly at finer scales, for example, in situ adaptation to edaphic conditions or more rocky and arid habitats. In parts potentially neutrally driven morphological innovations seem to keep populations separated on secondary contact by influencing pollinator specificity. We inferred these dynamics to be underpinned by genomic processes, including hybridization and horizontal gene transfer. Taken together, neutral and adaptive processes with scale-dependent effects contribute to lineage diversification, and thus, to the megadiverse species richness in Erica in the CFR.
Publications
-
An approach to determining anthocyanin synthesis enzyme gene expression in an evolutionary context: an example from Erica plukenetii. Annals of Botany, 124(1), 121-130.
Le Maitre, N C; Pirie, M D & Bellstedt, D U
-
Floral Color, Anthocyanin Synthesis Gene Expression and Control in Cape Erica Species. Frontiers in Plant Science, 10(2019, 11, 28).
Le Maitre, N C; Pirie, Michael David & Bellstedt, Dirk U.
-
Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica. BMC Evolutionary Biology, 19(1).
Pirie, Michael D.; Kandziora, Martha; Nürk, Nicolai M.; Le Maitre, Nicholas C.; Mugrabi de Kuppler, Ana; Gehrke, Berit; Oliver, Edward G. H. & Bellstedt, Dirk U.
-
Small differences, big secrets. Veld & Flora 106(1): 22– 31
Bellstedt, D.U.; Coetzee, A.; Hitchcock, A.; Kandziora, M.; van der Niet, T.; Nürk, N.M.; Musker, S. & Pirie, M.D.
-
Botaniske hager går sammen for å stanse utryddelsen av arter: Global Conservation Consortium for Erica Årringen 2020–2021 (24–25): 103–110
Pirie, M.D.; Blackhall-Miles, R.; Bourke, G.; Crowley, D.; Ebrahim, I.; Forest, F.; Knaack, M.; Koopman, R.; Lansdowne, A.; Nürk, N.M.; Osborne, J.; Pearce, T.R.; Rohrauer, D.; Smit, M. & Wilman, V.
-
Preventing species extinctions: A global conservation consortium for Erica. PLANTS, PEOPLE, PLANET, 4(4), 335-344.
Pirie, Michael D.; Blackhall‐Miles, Robbie; Bourke, Greg; Crowley, Dan; Ebrahim, Ismail; Forest, Félix; Knaack, Michael; Koopman, Rupert; Lansdowne, Alex; Nürk, Nicolai M.; Osborne, Jo; Pearce, Timothy R.; Rohrauer, Daniel; Smit, Martin & Wilman, Victoria
-
Where have all the heathers gone?. Sibbaldia: the International Journal of Botanic Garden Horticulture (21).
Nelson, Charles & Pirie, Michael
-
Geographic isolation enables recurrent pollinator shifts despite hybridisation in the Cape’s hyperdiverse heathers. (2023, 7, 19). Wallstein Verlag.
Musker, Seth D.; Pirie, Michael D. & Nürk, Nicolai M.
-
Phylogenomic Studies in Heathers (Erica L.). Doctoral thesis, University of Bayreuth, Faculty of Biology, Chemistry and Earth Sciences Bayreut
Musker, S.D.
