Seed germination strategies: an evolutionary trajectory independent of vegetative functional traits

Abstract

Seed germination strategies vary dramatically among species but relatively little is known about how germination traits correlate with other elements of plant strategy systems. Understanding drivers of germination strategy is critical to our understanding of the evolutionary biology of plant reproduction.We present a novel assessment of seed germination strategies focussing on Australian alpine species as a case study. We describe the distribution of germination strategies and ask whether these are correlated with, or form an independent axis to, other plant functional traits. Our approach to describing germination strategy mimicked realistic temperatures that seeds experience in situ following dispersal. Strategies were subsequently assigned using an objective clustering approach. We hypothesized that two main strategies would emerge, involving dormant or non-dormant seeds, and that while these strategies would be correlated with seed traits (e.g., mass or endospermy) they would be largely independent of vegetative traits when analysed in a phylogenetically structured manner.Across all species, three germination strategies emerged. The majority of species postponed germination until after a period of cold, winter-like temperatures indicating physiological and/or morphological dormancy mechanisms. Other species exhibited immediate germination at temperatures representative of those at dispersal. Interestingly, seeds of an additional 13 species “staggered” germination over time. Germination strategies were generally conserved within families. Across a broad range of ecological traits only seed mass and endospermy showed any correlation with germination strategy when phylogenetic relatedness was accounted for; vegetative traits showed no significant correlations with germination strategy. The results indicate that germination traits correlate with other aspects of seed ecology but form an independent axis relative to vegetative traits.

Habitat‐related seed germination traits in alpine habitats

“…In the alpine environment, the large species and microhabitats diversity have resulted in a variety of germination responses and dormancy types, which makes it difficult to define a common "alpine" germination strategy (Hoyle et al, 2015;Körner, 2003;Schwienbacher, Navarro-Cano, Neuner, & Erschbamer, 2011). For example, although many alpine plants have deep physiological dormancy Schwienbacher et al, 2011;Sommerville, Martyn, & Offord, 2013) and require light (Jaganathan, Dalrymple, & Liu, 2015) and high temperatures for germination (Jumpponen, Vare, Mattson, Ohtonen, & Trappe, 1999), nondormant seeds (Sommerville et al, 2013), very low temperature requirements and dark conditions (Schwienbacher et al, 2011) for germination have also been observed.…”

Testing the niche‐breadth–range‐size hypothesis: habitat specialization vs. performance in Australian alpine daisies

“…The rare species were characterized by high seed viability and low germination (or higher germination sensitivity), particularly in the open heathland habitat, which is known for its high species diversity. Previous research on germination in Australian alpine plants suggested that plants follow three strategies: postponed germination, immediate germination, and staggered germination (Hoyle et al 2015). The Brachyscome species appear to follow the first and third of these strategies.…”

“…Previous research on germination in Australian alpine plants suggested that plants follow three strategies: postponed germination, immediate germination, and staggered germination (Hoyle et al. ). The Brachyscome species appear to follow the first and third of these strategies.…”

Conservation choice on the rare endangered plants Glehnia littoralis

“…Buoyancy and germination ability of the fruits during and after seawater immersion are adaptations of coastal specialists to seawater dispersal (Nilsson et al , 2010; Yang et al , 2012; Hoyle et al , 2015; Lin et al , 2016). Without these properties, G. littoralis cannot disperse and persist along supratidal zones of coasts and will be eliminated or suppressed by surging seawater, with the fruits sinking to seabed or unable to germinate (Yang et al , 2012).…”