A decade of genetic makeup in the aerial seed bank of a fire-evader tree

Abstract

Background Aerial seed banks occur in plants that postpone the release of viable seeds, thereby providing a mechanism for population maintenance in unpredictable environments. Seeds retained on the mother trees offer a reservoir of genetic diversity across years, but the pattern and evolutionary consequences of such accumulated diversity are poorly understood. We characterize the genetic layout of an aerial seed bank composed of serotinous cones formed in 2003 and in 2014 in a historically fire-prone area. Our hypothesis is that within this timeframe, recurrent fires could have modified the genetic makeup of the seed bank. Results Our results did not reveal any genetic difference along the 12-year period, but indicated a significant genetic variation (13%) of seed banks among trees within the same year. Moreover, progeny from the seed bank showed a 4% increase of observed heterozygosity, together with 14 new alleles, compared to mother trees. Finally, a strong homogenization effect of pollen flow on the genetic diversity was detected, with a very high effective number of fathers in 2003 and 2014. Conclusions Our results highlight the temporal stability of the genetic makeup of aerial seed banks in this fire-prone area. The maternal genetic differences and an increase of genetic diversity (linked to effective pollen flow) in new generations compared to their maternal progenitors are also noteworthy. Together, these characteristics represent key assets for serotinous forest adaptation and persistence in the face of increasing wildfire activity.