<< Vers l'annuaire

Eric Imbert

University lecturer Team Metapopulation
Phone +33 (0)4 67 14 49 10
Localization Bâtiment 22, 2ème étage

Key research activities

1- Biology, population demography and genetics of a rare and endemic specie : Centaurea corymbosa

Rare species are an important component of biodiversity and are generally seen as indicators of special ecological conditions, often with high and/or unique biodiversity  The combination of the effects of land use changes and of climatic changes will severely affect both the ability of such organisms to adjust in the short term and their ability to adapt by evolution (long term).
Centaurea corymbosa is an endemic plant in the Massif de la Clape (South of France). The aims of the research are to quantify the effects of habitat closure on the demographic equilibrium and the genetic structure of these populations. The demography and genetics of the 6 populations of Centaurea corymbosa have been monitored since 1994 -we currently have the life history for 5791 individuals. Most of the individuals (85%) occur in a band of varying width that extends along the cliff edge of a plateau. This marginal habitat probably protects the plant from direct extinction by habitat closure. However, the closure of the habitat matrix causes habitat fragmentation for species of open habitats such as Centaurea corymbosa, and therefore an increasing isolation. One of the first effects of fragmentation is to reduce the exchange of individuals and genes between existing populations. This leads to an increase in population inbreeding and an increased sensitivity to perturbations.

In addition, habitat loss reduces the probability of site re-colonisation of certain sites because of isolation. As a result, the occupation rate of favourable habitats is reduced, which causes a reduced viability of the meta-population.

This kind of questions are usually studied at the scale of meta-populations, but similar patterns are observed at the population level. Thus, local habitat modifications such as, for example, shrubland encroachment, can lead to the isolation of favourable occupied or unoccupied habitat patches.

Contributors : Eric Imbert, David Carbonell
Collaborations : Miquel Riba (CREAF, UAB, Spain), Bruno Colas & Hélène Fréville (MNHN, Paris)


2-Reproductive biology in Iris chamaeris : does the flower colour matter ?

Iris chamaeiris is a common species in the south of France, Italy and Spain. This species has a wide range of flower colour including purple, blue, white and yellow. Most of the natural populations are polymorphic, and a few monomorphic populations (with the yellow morph only) have been described. Note that populations where only purple phenotypes can be found have never been observed. Common garden experiments have shown that flower colour is genetically determined and heritable. Furthermore, there is no difference in odour composition and flower morphology between yellow and purple morphs. Changes in flower colour are thought to be one of the most common transitions in plant reproductive biology, but yet the selective forces responsible for shifts in colour are still poorly understood.

One frequently invoked reason for colour shifts is that flower colour is linked to pollination syndromes (a suite of characteristics associated with a certain pollinator) and this has led many to argue that pollinator preferences are the primary selective agents driving colour transitions. Questions invoked in this species are 1) is flower colour associated with a differentiation in pollinator community, 2) what is the importance of gene flow between phenotypes, 3) what are the processes (pollinator community, drift…) related to spatial variation (i.e. population differentiation) in morph frequency ?

Contributors: Eric Imbert
Collaborations : Bertrand Schatz (CEFE, Montpellier), Carol Wilson (Claremont University, California), Bruce Anderson (Stellenbosch University, South Africa)

3-Other research activities :

Could  we use herbarium samples to infer past genetic diversity ?
Is plant reproductive system affected by pollinator decline ?