Lower selfing rates in metallicolous populations than in non-metallicolous populations of the pseudometallophyte Noccaea caerulescens (Brassicaceae) in Southern France.

BACKGROUND AND AIMS: The pseudometallophyte Noccaea caerulescens is an excellent model to study evolutionary processes, as it grows both on normal and on heavy-metal-rich, toxic soils. The evolution and demography of populations are critically impacted by mating system and, yet, information about the N. caerulescens mating system is limited. METHODS: Mean selfing rates were assessed using microsatellite loci and a robust estimation method (RMES) in five metallicolous and five non-metallicolous populations of N. caerulescens in Southern France, and this measure was replicated for two successive reproductive seasons. As a part of the study, the patterns of gene flow among populations were analysed. The mating system was then characterized at a fine spatial scale in three populations using the MLTR method on progeny arrays. KEY RESULTS: The results confirm that N. caerulescens has a mixed mating system, with selfing rates ranging from 0·2 to 0·5. Selfing rates did not vary much among populations within ecotypes, but were lower in the metallicolous than in the non-metallicolous ecotype, in both seasons. Effective population size was also lower in non-metallicolous populations. Biparental inbreeding was null to moderate. Differentiation among populations was generally high, but neither ecotype nor isolation by distance explained it. CONCLUSIONS: The consequences of higher selfing rates on adaptation are expected to be weak to moderate in non-metallicolous populations and they are expected to suffer less from inbreeding depression, compared to metallicolous populations.

Large distribution and high sequence identity of a Copia-type retrotransposon in angiosperm families.

Retrotransposons are the main component of plant genomes. Recent studies have revealed the complexity of their evolutionary dynamics. Here, we have identified Copia25 in Coffea canephora, a new plant retrotransposon belonging to the Ty1-Copia superfamily. In the Coffea genomes analyzed, Copia25 is present in relatively low copy numbers and transcribed. Similarity sequence searches and PCR analyses show that this retrotransposon with LTRs (Long Terminal Repeats) is widely distributed among the Rubiaceae family and that it is also present in other distantly related species belonging to Asterids, Rosids and monocots. A particular situation is the high sequence identity found between the Copia25 sequences of Musa, a monocot, and Ixora, a dicot species (Rubiaceae). Our results reveal the complexity of the evolutionary dynamics of the ancient element Copia25 in angiosperm, involving several processes including sequence conservation, rapid turnover, stochastic losses and horizontal transfer.