Abstracts (first author)

Talk 

Comparative phylogeography of African rain forest trees: a review of genetic signatures of vegetation history in the Guineo-Congolian region

Author(s): Hardy OJ

Summary:

The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forest plants now enables a first biogeographic synthesis. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic changes; and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. Phylogeographic patterns indicate that most of the widespread species showing nowadays a near continuous spatial distribution have been fragmented in the past. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, and at a large scale they often match the main phytogeographic subdivision of the Guineo-Congolian region. However, patterns vary substantially among species and they provide only partial support for current hypotheses on the location of Pleistocene forest refuges. Among the patterns shared by many species, we highlight a recurrent genetic discontinuity between the north and the south of the Lower Guinean region which matches the climatic hinge on each side of which dry and wet seasons are inverted. Whether this discontinuity results from past forest fragmentation or current climate conditions is discussed.


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Abstracts (coauthor)

Summary:

Vegetation history in tropical Africa is still to date largely unknown. Hypotheses include major speciation events during Pleistocene climate changes and ecological speciation across abiotic gradients. Phylogeographic studies might shed new light on this matter as indicated by similar studies in temperate regions; the challenges in tropical Africa being different highly diverse biotic and abiotic conditions and a distinct climatic and geological history. Here we analysed phylogeographic patterns (chloroplast-DNA sequences, AFLP, microsatellites) of eight widespread herb and liana species from four different genera of the family Marantaceae (Zingiberales) including four pairs of sister species.

Across all investigated species, intraspecific patterns of genetic diversity from chloroplast DNA were concordant with overall Marantaceae diversity: higher in topographically rich Gabon and showing traces of expansion across the rather flat central Cameroon and the Congo basin. However, comparing sister species relationships between different genera revealed different levels and modes of speciation. Patterns in the genus Haumania suggest allopatric speciation with genetic pattern concordant with postulated Pleistocene refugia followed by current intraspecific gene flow in overlapping distribution areas. Concordant pattern of genetic diversity and the absence of hybridization in the genus Megaphrynium might hint towards sympatric speciation through adaptation to different pollinator species. In the genus Marantochloa allopatric speciation followed by complete incompatibility between sister species is indicated in one species pair. In a second case two morphologically distinct sister species are indistinguishable genetically and the mode of speciation still open to debate.

This study gives an insight into the diverse and ongoing evolutionary processes in central tropical Africa and the role of different geographic areas and ecological traits in the evolutionary process.

Contacts

Chairman: Octávio S. Paulo
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Tel: 00 351 217500000 ext22359
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email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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