Emmanuelle Billard

Biography

"My work focuses on the mating systems and the way they can influence evolutionary processes at a relatively short time scale. I address two major kinds of questions: the first concerns the maintenance of sexual polymorphisms within and between species, while the second focuses on the impact of mating system on processes like hybridization or invasion by non-native species. I address these questions by multiple approaches, from reproductive ecology to population genetics. As a junior lecturer, I mainly taught plant biology and population genetics. A large part of my previous works dealt with marine species, and more specifically brown algae. During my PhD thesis, my study model was the species complex Fucus vesiculosus / F. spiralis which offers numerous advantages to address this kind of questions. The mating system has evolved several times in this genus and reproductive barriers are incomplete between species. In addition, hybrids don’t experience a fitness decrease in terms of fertility. However, a field survey combined with a population genetics analysis indicated that despite external fertilization, important inbreeding or even selfing, most certainly prevents hybridization. Conversely, it may have facilitated the split in the hermaphroditic species, which actually consists in two genetically distinct entities, now renamed as F. spiralis and F. guiryi. In vascular plants, a classical pathway to switch between hermaphroditism and dioecy is through gynodioecy; when hermaphrodites and females coexist in the same populations. However, in some species, this mating system appears to be a stable state and I became interested in the different possible causes of the maintenance of gynodioecy, like the importance of female advantage in angiosperms and the influence of local sex ratio on this advantage in the species Silene nutans. My current work in CIBIO-InBIO mainly concerns the African iconic plant: Welwitschia mirabilis, which is endemic to arid and semi-arid regions of western Namibia and Angola. This dioecious species is long-lived (individuals can live for more than 2000 years) and relies on pollinators for reproduction. It is found in discreet populations with obvious age cohorts, dispersal seems to be limited (≈10 km), and genetic variability appears relatively high, offering ideal conditions to investigate individual relationships among stable, multigenerational populations. Plus, W. mirabilis’ susceptibility to damages caused by humans, herbivores or even the fungus Aspergillus niger, well as its low recruitment rate, make it essential to better comprehend its population functioning."

Research Interest

Plant biology and population genetics