Nicolas Thiercelin


Institute of Evolution, Behavior and Genetics
Biology I

University of Regensburg
D-93040 Regensburg
Germany

Tel: +49 (0)941 9431677
E-Mail: nicolas.thiercelin (at) biologie.uni-regensburg.de

Curriculum Vitae

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Impact of life history and ecology on rate of diversification and speciation,
as exemplified by crustacean communities along the western Atlantic and
on both sides of the Panama Isthmus


The rise of the Panama Isthmus, from about 12Mya until 3Mya ago (Coastes & Obando, 1996), caused the closure of the Tropical American Seaway, which connected the tropical Pacific and Atlantic Oceans. From this geological event resulted an isolation and genetic divergence of the populations on both sides of the isthmus, a process commonly reffered  to as trans-isthmian divergence (Lessios, 2008).

Knowlton & Weigt (1998) showed that sister-species of pistol shrimp from the genus Alpheus living in mangroves on both sides of the isthmus had a lower genetic differentiation than pairs of sister-species in this highly diversified genus. Mangroves are supposed to be the last environment allowing genetic exchange between the Pacific and Atlantic Ocean during the final closure of the Panama Isthmus, about 3Mya ago.


To investigate how the ecological characteristics (as habitat, length of larval stage or behaviour) may have influenced the process of speciation, I use littoral grapsoid crabs as model organisms comparing species from mangroves and rocky shore environments.

Grapsoid crabs represent an important part of the worldwide mangrove diversity with approximately 60 genera and 400 species. They are found from subtidal to freshwater environments and the American species are characterized by a wide distribution (Florida to Brazil and Baja California to Peru), with some species considered to have trans-isthmian and amphi-atlantic distributions.


My project focuses on two aspects :

1) Studying the connectivity of populations of grapsoid crabs along the western Atlantic Ocean, and the influence of the Amazon and Orinoco freshwater plume (see Lessios, 2003).

2) Investigating the trans-isthmian differentiation for the same species of grapsoid crabs with emphasis on the ecological characteristics of these species and the search of unnamed species (Schubart & Cuesta, 2005).

Additionally, data concerning amphi-atlantic differentiation will be acquired for the studied species that also have an amphi-atlantic distribution (3).

  
map

p_transversus_network_cox1P_transversus_image

Maximum parsimony haplotype networks of Pachygrapsus transversus (top) and Cyclograpsus integer (bottom) based on the Cox1 gene. Green: Caribbean population; orange: Brazilian population.


cyclograpsus_integer_network_cox1

References:

Coates, A.G., and Obando, J.A. (1996) The geological evolution of the Central American Isthmus. In Evolution and environment in tropical America. Jeremy B. C. Jackson, J.B.C., Budd, A.F. and Coates, A.G. (eds). Chicago: University of Chicago Press, pp. 21-56.

Knowlton, N., and Weigt, L.A. (1998) New dates and new rates for divergence across the Isthmus of Panama. Proceeding of the Royal Society of London, B 265: 2257-2263.

Lessios HA, Kane J, Robertson DR (2003) Phylogeography of the pantropical sea urchin Tripneustes: contrasting patterns of population structure between oceans. Evolution 57: 2026-2036.

Lessios, H.A. (2008) The Great American Schism: Divergence of marine organisms after the rise of the Central American Isthmus. Annual Review of Ecology, Evolution, and Systematic 39: 63-91.

Schubart, C.D., Cuesta, J.A., and Felder, D.L. (2005) Phylogeography of Pachygrapsus transversus (Gibbes, 1850): The effect of the American continent and the Atlantic Ocean as gene flow barriers and recognition of Pachygrapsus socius Stimpson 1871 as a valid species. Nauplius 13: 99-113.






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