Angiosperm polyploids and their road to evolutionary success

Abstract

The abundance of polyploidy among flowering plants has long been recognized, and recent studies have uncovered multiple ancient polyploidization events in the evolutionary history of several angiosperm lineages. Once polyploids are formed they must get locally established and then propagate and survive while adapting to different environments and avoiding extinction. This might ultimately lead to their long-term evolutionary success, where their descendant lineages survive for tens of millions of years. Along this road to evolutionary success, polyploids must overcome several obstacles, to which several genetic and ecological factors are likely to contribute. One recurrent observation, based on present-day polyploids, has been the high frequency of polyploids in harsh environments. Also, recent studies proposed that the success of certain ancient polyploids might be linked to periods of climatic change. Although we are still in the early stages of unraveling the factors that resulted in the long-term evolutionary success of ancient polyploids, the advances in genomic sequencing and molecular dating methods promise to enhance our understanding. It, therefore, seems timely to review our current knowledge of what determines the success of polyploids. Here, we discuss especially how harsh conditions or periods of climatic change might affect the rate of formation, establishment, persistence and long-term evolutionary success of polyploids in angiosperms.

Polyploid Evolution of the Brassicaceae during the Cenozoic Era

“…The lower speciation/diversification rates and higher extinction rates observed in neopolyploids compared with diploids (Mayrose et al, 2011) could be due to sampling errors and methodological shortcomings (Soltis et al, 2014) or may also be a consequence of the outweighing costs of polyploidy associated genomic and phenotypic instability, as well as the reproductive disadvantages under normal conditions. However, the adaptive advantages of polyploidy caused by enhanced genetic repertoire (resulting from increased heterozygosity, the buffering effect of gene redundancy on mutations, neofunctionalization, differential expression, or epigenetic reprogramming of duplicated genes) and reproductive plasticity (facilitation of reproduction through selffertilization or asexual means) would be expected to confer a competitive advantage to polyploid species under extreme and unstable environmental conditions (Comai, 2005;Fawcett and Van de Peer, 2010). Indeed, polyploid species, owing to their better adaptability to adverse environmental conditions and extreme habitats, were proposed to have survived the catastrophic events leading to the CretaceousTertiary extinction event (Fawcett et al, 2009).…”

Research Article Chromosome variations and diversity of Epidendrum ibaguense Lindl. (Orchidaceae) on the Tepequém's Tepuy, Roraima, Brazil.

“…Interestingly, this and other polyploid species are found in disturbed environments (Assis, 2009;Pinheiro et al, 2009;Felix and Guerra, 2010). Duplicated or repetitive gene sequence may provide a local advantage for polyploid organisms (Fawcett and Van der Peer, 2010). On the other hand, such a variation in chromosome number may not represent an effective reproductive barrier neither for Epidendrum nor the remaining groups of plants (Cozzolino et al, 2004;Marques et al, 2010).…”

Genome size variation and polyploidy incidence in the alpine flora from Spain

“…Polyploidy is thought to influence the capacity to tolerate environmental stress (Fawcett & Van de Peer, 2010) and may have granted some plant species a higher capacity to colonize new habitats after glaciation (Brochmann & al., 2004). Altogether, these beneficial traits have led to the assumption that polyploids are more frequent at higher latitude or altitude than related diploids (Löve & Löve, 1949;Love & Love, 1967).…”

“…Due to the possibility of immediate changes in the phenotype, fitness and ecological tolerances of polyploid lineages in comparison with its diploid progenitors, polyploidization has been proposed as a major mechanism of sympatric speciation (Adams & Wendel, 2005), and might allow evolutionary transitions that would have been previously impossible (Comai, 2005;Hegarty & Hiscock, 2008). Thus, in a single genetic event, polyploidy may produce a broad variation, increasing the likelihood of coping with drastic environmental stress, such as climate changes (Fawcett & Van de Peer, 2010).…”