Abstract
Polyploidy is a common phenomenon in the evolution of angiosperms. It has been suggested that polyploids manage harsh environments better than their diploid relatives but empirical data supporting this hypothesis are scarce, especially for trees. Using microsatellite markers and flow cytometry, we examine the frequency of polyploids and diploids in a progeny trial testing four different populations of Acacia senegal, a species native to sub-Saharan regions of Africa. We compare growth between cytotypes and test whether polyploid seedlings grow better than diploids. Our results show that polyploids coexist with diploids in highly variable proportions among populations in Senegal. Acacia senegal genotypes were predominantly diploid and tetraploid, but triploid, pentaploid, hexaploid, and octaploid forms were also found. We find that polyploids show faster growth than diploids under our test conditions: in an 18 years old field trial, polyploid superiority was estimated to be 17% in trunk diameter and 9% in height while in a growth chamber experiment, polyploids grew 28% taller, but only after being exposed to drought stress. The results suggest that polyploid A. senegal can have an adaptive advantage in some regions of Africa.
Highlights
Polyploidy, the achievement of more than two sets of chromosomes through gametic nonreduction and to a lesser degree somatic doubling has important ecological and evolutionary consequences for speciation (Madlung, 2013)
Investigating a progeny trial with mature A. senegal, we discovered that the trees had mixed ploidy levels (Diallo et al, 2015)
All offspring from diploid mothers were diploid, while tetraploid mothers produced either offspring with the same ploidy level or higher levels
Summary
Polyploidy, the achievement of more than two sets of chromosomes through gametic nonreduction and to a lesser degree somatic doubling has important ecological and evolutionary consequences for speciation (Madlung, 2013). It has been estimated that polyploids form at the frequency of approximately 1 per 100,000 individuals (Ramsey and Schemske, 1998; Levin, 2002) and that 2–4% of all speciation events involve polyploidization (Otto and Whitton, 2000). Successful polyploidization is generally accompanied by morphological, phenological, physiological, and ecological changes in plants (Levin, 2002), and may produce individuals that can tolerate fluctuating environments (Soltis et al, 2004; Prentis et al, 2008), make use of new niches or by other means become more successful than their progenitor species (Leitch and Leitch, 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
