Abstract
Ploidy and species range size or threat status have been linked to variation in phenotypic and phenological seed and seedling traits, including seed size, germination rate (speed) and seedling stature. There is surprisingly little known about the ecological outcomes of relationships between ploidy, key plant traits and the drivers of range size. Here we determined whether ploidy and range size in Pomaderris, a genus of shrubs that includes many threatened species, are associated with variation in seed and seedling traits that might limit the regeneration performance of obligate seeders in fire-prone systems. We experimentally quantified seed dormancy and germination processes using fire-related heat treatments and evaluated seedling performance under drought stress. We also examined the association of seed size with other seed and seedling traits. Polyploids had bigger seeds, a faster germination rate and larger and taller seedlings than diploids. There was a lack of any clear relationship between range size and seed or seedling traits. The ploidy effects observed for many traits are likely to be indirect and associated with the underlying seed size differences. These findings indicate that there is a higher potential competitive advantage in polyploid than diploid Pomaderris during regeneration, a critical stage in the post-fire environment. This insight to the regeneration phase may need to be considered when planning and prioritising management of threatened species.
Highlights
Polyploidy, the condition of having more than two genome copies, is widespread in plants and thought to be a key evolutionary mechanism in the diversification of flowering plants (Hoya et al, 2007; Madlung, 2013)
There was no interaction between ploidy and range size influencing the four traits measured in the seed germination experiment
Polyploid seeds were significantly heavier than diploid seeds (χ2 = 11.555, d.f. = 1, p < 0.001; Figure 1A) and reached 50% germination (T50) significantly faster than diploid seeds (χ2 = 4.953, d.f. = 1, p = 0.048; Figure 1B)
Summary
Polyploidy, the condition of having more than two genome copies, is widespread in plants and thought to be a key evolutionary mechanism in the diversification of flowering plants (Hoya et al, 2007; Madlung, 2013). Polyploids are thought to have advantages over diploids that allow them to persist in Polyploidy Affects Seed and Seedling Traits challenging environments (Soltis and Soltis, 2000; Madlung, 2013; Ramsey and Ramsey, 2014) They can be more resilient or competitive under stress than diploids (Godfree et al, 2017; Stevens et al, 2020) and have an increased chance of becoming invasive (Soltis and Soltis, 2000; Hull-Sanders et al, 2009; Pandit et al, 2011; Thébault et al, 2011; Te Beest et al, 2012). Polyploidy may affect a species’ relative evolutionary capacity, competitive dominance and conservation status
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