Germination behavior is one of the earliest phenotypes expressed by plants. This fact has several consequences for the evolution of postgermination traits, ecological niches, and geographic ranges. By determining the conditions that plants experience after they germinate, germination influences phenotypic expression of postgermination traits, natural selection on them, and their genetic basis. The breadth of germination niches may influence the ecological breadth and geographic ranges of species. Because germination is expressed early, it is frequently subjected to natural selection before other traits are expressed. We review evidence for natural selection on and adaptation of germination and discuss how the breadth of the germination niche is associated with the ecological niche and range of plant species. We review evidence for the coevolution of germination and postgermination traits and compare germination to postgermination niches. Finally, we discuss how germination responses to altered environments can influence species distribution and the evolution of postgermination traits after environmental change.

Climate change has led to major changes in the phenology (the timing of seasonal activities, such as flowering) of some species but not others. The extent to which flowering-time response to temperature is shared among closely related species might have important consequences for community-wide patterns of species loss under rapid climate change. Henry David Thoreau initiated a dataset of the Concord, Massachusetts, flora that spans Ϸ150 years and provides information on changes in species abundance and flowering time. When these data are analyzed in a phylogenetic context, they indicate that change in abundance is strongly correlated with flowering-time response. Species that do not respond to temperature have decreased greatly in abundance, and include among others anemones and buttercups [Ranunculaceae pro parte (p.p.)], asters and campanulas (Asterales), bluets (Rubiaceae p.p.), bladderworts (Lentibulariaceae), dogwoods (Cornaceae), lilies (Liliales), mints (Lamiaceae p.p.), orchids (Orchidaceae), roses (Rosaceae p.p.), saxifrages (Saxifragales), and violets (Malpighiales). Because flowering-time response traits are shared among closely related species, our findings suggest that climate change has affected and will likely continue to shape the phylogenetically biased pattern of species loss in Thoreau's woods.conservation ͉ extinction ͉ phenology ͉ phylogenetic conservatism ͉ phylogeny T he impact of climate change on species and communities has been well documented. Arctic forests are shifting poleward and alpine tree lines are shifting upward (1-3); spring flowering time is advancing rapidly (4-7); pest outbreaks are spreading (8); and numerous species are declining in abundance and risk extinction (9). However, despite these generalized trends, species vary dramatically in their responses to climate change. For example, although the spring flowering times of many temperate plants are advancing, some are not changing and others are flowering later in the season (5, 10, 11). Understanding the evolutionary (i.e., phylogenetic) history of traits that are influenced by climate (e.g., flowering phenology) has been an underexplored area of climate change biology, despite the fact that it could prove especially useful in predicting how species and communities will respond to future climate change. Closely related species often share similar traits, a pattern known as phylogenetic conservatism (12)(13)(14)(15)(16)17). If closely related species share similar traits that make them more susceptible to climate change (14, 17), species loss may not be random or uniform, but rather biased against certain lineages in the Tree of Life (i.e., phylogenetic selectivity; see ref. 18). However, a deeper inquiry into these patterns has been hampered largely because adequate datasets documenting community-wide responses to climate change are exceedingly rare.During the mid-19th century, the naturalist and conservationist Henry David Thoreau spent decades exploring the temperate fields, wetlands, and deciduous forests of Concord...

SummarySeed dormancy, by controlling the timing of germination, can strongly affect plant survival. The kind of seed dormancy, therefore, can influence both population and species-level processes such as colonization, adaptation, speciation, and extinction.We used a dataset comprising over 14 000 taxa in 318 families across the seed plants to test hypotheses on the evolution of different kinds of seed dormancy and their association with lineage diversification.We found morphophysiological dormancy to be the most likely ancestral state of seed plants, suggesting that physiologically regulated dormancy in response to environmental cues was present at the origin of seed plants. Additionally, we found that physiological dormancy (PD), once disassociated from morphological dormancy, acted as an 'evolutionary hub' from which other dormancy classes evolved, and that it was associated with higher rates of lineage diversification via higher speciation rates.The environmental sensitivity provided by dormancy in general, and by PD in particular, appears to be a key trait in the diversification of seed plants.

Our findings support the use of herbarium records for understanding plant phenological responses to changes in temperature, and also importantly establish a new use of herbarium collections: inferring primary phenological cueing mechanisms of individual species (e.g., temperature, winter chilling, photoperiod). These latter data are lacking from most investigations of phenological change, but are vital for understanding differential responses of individual species to ongoing climate change.