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Post-doctoral researcher

phone: +32 (0)2 650 45 11

e-mail: Alexandra.Ley@ulb.ac.be










Research interests



I am particularly interested in the underlying mechanisms of species diversification. Since experiences during my PhD I am in favour of a broadly arranged integrative approach. Shedding light onto the chosen organism from all possible angels might end up with some surprising results. It is not always the factor with the most obvious pattern at present that is also the most probable to have invoked speciation.

My favourite model organisms are hereby the Marantaceae (550 spp.) from the order Zingiberales. A fascinating family of pantropically distributed species of perennial herbs and lianas with spectacular flowers and a unique explosive pollination mechanism.

In my PhD I analysed various speciation relevant factors searching for differences between species in e.g. distribution range, habitat, habit, breeding system and pollinator association (including floral morphologies and pollinator behaviour). To determine their relevance to speciation they were set into a phylogenetic context. However, the so far investigated pattern could only suggest reasons for a few speciation events. The number of parameters should thus be enlarged and also take into account that some speciation events might be blurred through time.

In the current project I am thus taking it a bit further trying to illuminate the past geographic history of the species pursuing its traces in the genome. I will compare phylogeographic pattern between sister species which display today equal geographic distribution ranges and pollinator associations. As low resolutions in ITS sequences suggest a young radiation in some genera, speciation might here have occurred in allopatry in segregated forest patches (refugia) provoked by the fluctuating climate of the Pleistocene.

As the Marantaceae are particular diverse between genera I will further investigate the influences of several traits such as breeding system (autogam/xenogam), pollinator association (birds/bees) and dispersal agents/distances (water/birds/mammals, narrow/far) onto the phylogeographic pattern of tropical herbs and lianas in contrast to trees in Central Africa.




Post-doctoral project



Phylogeography of African Marantaceae - Reconstruction of the refugial theory in tropical Africa on Marantaceae

Supervisor: O. Hardy


Post-doctoral research fellowship of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG)




Education and Research



  1. 2008 - ongoing : Post-doctoral position. Phylogeography of African Marantaceae. Advisor: Dr. O. Hardy (Université Libre de Bruxelles, Belgium)

  2. 2004-2008 : Ph.D. Evolutionary tendencies in African Marantaceae – evidence from floral morphology, ecology and phylogeny. Advisor: Prof. Dr. R. Claßen-Bockhoff (University Mainz, Germany)

  3. 2002-2003 : Diploma in Biology – extrapolation of plant distribution ranges. Diversity and endemism in the tribus Epidendreae (Orchidaceae) in Bolivia. Advisor: Prof. Dr. W. Barthlott, Prof. Dr. P. Ibisch (University Bonn, Germany)

  4. 2000-2001 : Study abroad student at the La Trobe University, Melbourne (Australia)

  5. 1997-2002 : Biological studies at the Rheinische Friedrich Wilhelms University, Bonn (Germany)




Thesis



Ph.D. thesis: "Evolutionary tendencies in African Marantaceae – evidence from floral morphology, ecology and phylogeny" – University of Mainz , Germany. Supervised by Prof. Dr. R. Claßen-Bockhoff


The Marantaceae (550 species) are a world wide distributed family of perennial herbs and lianas from the understory of tropical lowland forests. A comparison between the basal branching Sarcophrynium-clade and the derived Marantochloa-clade based on morphological and ecological data should exemplarily elucidate evolutionary tendencies in the family.

Thus this PhD study gives for the first time an overview over the floral biology and phylogeny of about 30 of the 40 known African Marantaceae species. The analyses are based on data from three field trips to Gabon each taking several months between September and January. Five floral types are described, which are each associated with a specific pollination guild (small, medium-sized and large bees, birds). Pollination experiments prove that 18 species are self-compatible, but only two species are autogamous, thus are independent of pollinators. Fruit set is generally low (10 – 30 %).

The complex synorganisation of the flower facilitates an explosive pollination mechanism. In order to understand its ecological functionality flowers from 66 species representing all mayor phylogenetic clades of the Marantaceae were analysed under a functional morphological view. Despite apparent diversity there is a high correspondence between all analysed species in the synorganisation of the most important floral parts (style, hooded staminode, fleshy staminode) guaranteeing an obligate excitation of the explosive pollination mechanism. Minute variations lead to differential pollen deposition on the pollinator and occasionally autogamy.

Based on data from nrDNA (ITS, 5S) and cpDNA (trnLF) and a nearly complete taxon sampling the  phylogeny of the two African clades is reconstructed. Morphological and ecological traits and geographic distribution patterns are parsimoniously reconstructed onto the latter in order to evaluate their evolutionary significance. The results hint to the involvement of a number of different speciation factors.


Key words: Africa, breeding system, floral morphology, Gabon, Marantaceae, nectar, plant-pollinator interaction, pollen, P/O-ratio, pollination, pollination syndromes, phylogeny, tropical forest




Publications in international peer-reviewed journals



Ley AC, Classen-Bockhoff R (2010) Evolution in African Marantaceae - Evidence from Phylogenetic, Ecological and Morphological Studies. Systematic Botany In press.

Ley AC, Hardy OJ (2010) Species delimitation in the Central African herbs Haumania (Marantaceae) using georeferenced nuclear and chloroplastic DNA sequences. Molecular Phylogenetics and Evolution 57, 859.

Pischtschan E, Ley AC, Classen-Bockhoff R (2010) Ontogenetic and phylogenetic diversification of the hooded staminode in Marantaceae. Taxon 59, 1111-1125.

Ley AC, Claßen-Bockhoff R (2009) Pollination syndromes in African Marantaceae. Annals of Botany 104, 15.




Thesis



Ley AC (2008) Evolutionary tendencies in African Marantaceae - evidence from floral morphology, ecology and phylogeny PhD, Johannes Gutenberg University.




Other publications


Ley AC, Claßen-Bockhoff R (2010) Parallel evolution in plant-pollinator interaction in African Marantaceae. In: X. van der Burgt, J. can der Maesen & J.-M. Onana (eds.) Systematics and Conservation of African Plants, pp. 847-854. Royal Botanic Gardens, Kew.

Ley AC, Claßen-Bockhoff R (2010) Ontogenetic and phylogenetic diversification in Marantaceae - a review. In Wanntorp, L. & Ronse de Craene, L (eds.) Flowers on the Tree of Life. Cambridge Univ. Press.

Ley AC, Nowicki C, Barthlott W, Ibisch PL (2004a) Biogeography and spatial diversity. In: Orchids of Bolivia - Diversity and conservation status (eds. Vasquez R, Ibisch PL), pp. 492-571. Editorial FAN, Santa Cruz de la Sierra, Bolivia.

Ley AC, Nowicki C, Ibisch PL (2004b) Distribution maps of the Pleurothallidinae. In: Orchids of Bolivia - Diversity and conservation status (eds. Vasquez R, Ibisch PL), pp. 402-487. Editorial FAN, Santa Cruz de la Sierra.

Nowicki C, Ley AC, Caballero R, et al. (2004) Extrapolating distribution ranges - BIOM 1.1, a computerized bio-climatic model for the extrapolation of species ranges and diversity patterns. In: Orchids of Bolivia - Diversity and conservation status (eds. Vasquez R, Ibisch PL), pp. 39-68. Editorial FAN, Santa Cruz de la Sierra.




Conferences


Ley AC, Nowicki C, Barthlott W, Ibisch PL (2004) Modelling and mapping diversity and endemism patterns of plant species: the example of the orchids of Bolivia. 17th annual meeting of the Society for Tropical Ecology in Bayreuth, Germany.

Ley AC, Claßen-Bockhoff R (2006, 2007, 2008) Parallel evolution in plant-pollinator interactions in African Marantaceae. Botany 2006, Chico, USA; 17th International Symposium Biodiversity and Evolutionary Biology, Bonn, Germany; 18th AETFAT Congress in Yaounde, Cameroon; Monocots 2008, Copenhagen, Denmark.

Ley AC, Claßen-Bockhoff R (2009) Ontogenetic and phylogenetic diversification in the flower of Marantaceae. First meeting of Biosyst EU, Leiden, Netherlands.









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