PhD

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I am interested in a broad range of topics from evolutionary biology to population ecology. I am especially interested in combining demographical, genetic and life-history trait studies to better understand metacommunity and metapopulation dynamics. During my PhD, at the Center for Evolutionary and Functional Ecology (CEFE-CNRS) in Montpellier, France, I focused on the freshwater snail metacommunity that inhabits a network of highly unstable freshwater habitats in Guadeloupe (a Island of the Lesser Antilles of about 570 km²) that frequently dry out to investigate how fragmentation affects both species diversity within local community and genetic diversity within local populations of a set of species (see my PhD thesis summary below).

Keywords: metapopulation, metacommunity, population genetics, extinction-colonization, fragmentation, selfing, mating systems, mollusk.

PhD thesis - from population genetics to community ecology: the case of the freshwater snail metacommunity in the French West Indies

            Striking similarities underlies the processes involved in the dynamics of genetic diversity and species diversity. However these diversities have been considered separately as part of population genetics and community ecology respectively. My work aims at quantifying processes that govern genetic diversity within species and species diversity within communities. To address this question I focus on the freshwater snail metacommunity from Grande-Terre Island (800 km²) in Guadeloupe. Twenty-nine snail species inhabit a network of highly unstable freshwater habitats that frequently dry out. This instability probably triggers extinction-colonization cycles of local populations. However, drying-out periods do not necessarily lead to extinction as some species are able to aestivate. First, I focused on the pulmonate gastropod Drepanotrema depressissimum. I used three complementary approaches: (1) an analysis of the spatial and temporal distribution of genetic diversity, (2) a patch occupancy model that take into account the presence of resistance forms such as aestivating snails and (3) a laboratory experiment in order to infer whether this species can rely on selfing to recolonize empty sites. These analyses reveal that extinction is not as frequent as previously thought and is not positively related to instability. Indeed, unstable sites are less prone to extinction. D. depressissimum overcome efficiently drying-out events aestivating in the ground and do not rely on selfing. Besides, extinction is more frequent in stable environments that encompass more speciose communities. Finally, at the scale of investigation, genetic diversity depends much more on patch size and connectivity than on apparent population age, suggesting that extinction-colonization cycles play a minor role in the species dynamics. In the last chapter, I quantify the impact of neutral processes on community assemblage. To this aim, I analyze the correlation between genetic diversity (microsatellites) of the two most-commonly encountered species – this diversity reflects neutral sampling process, with species diversity of local communities. This correlation is highly positive and relies on the parallel effect of a single site characteristic (connection to the local hydrographic network during the rainy season) on migration and colonization of both alleles and species. This suggests that neutral processes play an important role on the regulation of both genetic diversity and local species occurrence.

(A) Localization of Guadeloupe within the Lesser Antilles. (B) The Guadeloupe archipelago is divided in different islands. (C) Localization of the different freshwater environments in Guadeloupe. Black dots are the different sites surveyed since 2001 in the Islands of Grande-Terre and Marie-Galante while gray dots represent the different freshwater habitats that are not sampled.

Publications published

see the list at the bottom of the page

Publications in preparation

   4 - Lamy T, Pointier J-P, Jarne P, David P. Parallel processes drive species and genetic diversity in a freshwater snail metacommunity. In preparation.

  3 - Lamy T, Gimenez O, Pointier J-P, Jarne P, David P. A multistate occupancy model to infer metapopulation dynamics with hidden life stages. Submitted to Ecology.

Oral presentations and posters

• January 2011 “Community Genetics: what can a freshwater snail metacommunity from Lesser Antilles tell us?” Thomas Lamy, Jean Pierre Pointier, Philippe Jarne and Patrice David. CEFE Student seminary, 11 January 2011, Montpellier, France (Oral presentation)

• September 2010 “Link between genetic and species diversity in a metacommunity” Thomas Lamy, Géraldine Huth, Jean Pierre Pointier, Philippe Jarne and Patrice David. 1st French Ecology meeting, 2 - 4 September 2010, Montpellier, France (Oral presentation)

• July 2010 “Determinants of species diversity and genetic diversity in a community of tropical freshwater molluscs” Thomas Lamy, Géraldine Huth, Jean Pierre Pointier, Philippe Jarne and Patrice David.17th World Congress of Malacology, 18 - 24 July 2010, Phuket, Thailand (Oral presentation)

• November 2008 “Retracing history and the effect of human impact in European kelp forests”Myriam Valero, Christophe Destombe, Claire Daguin-Thiebaut, Thomas Lamy, Valeria Oppliger, Cécile Ribout, Anne Marie Jacob. World conference on Marine Biodiversity, 11-15 November 2008, Valencia, Spain (Oral presentation)

• August 2008 “History of the distribution area of the kelp Saccorhiza polyschides: relative importance of historical factors and genetic flow” Thomas Lamy and Myriam Valero. 30th meeting of the population genetics group, Petit Pois Déridé, Rennes, France (Poster)

Teaching (University Montpellier II)

• 2009 - 2011 Practical course and training sessions in Ecology, License (2nd and 3rd year students)
• 2008 - 2011 Courses and training sessions for students preparing the Agrégation and the Capes (teacher grade) in life sciences
• 2008 - 2009 Practical course in cellular Biology, License (1st and 2nd year students)