Abstract
Seed dormancy is considered to be an adaptive strategy in seasonal and/or unpredictable environments because it prevents germination during climatically favorable periods that are too short for seedling establishment. Tropical dry forests are seasonal environments where seed dormancy may play an important role in plant resilience and resistance to changing precipitation patterns. We studied the germination behavior of seeds from six populations of the Neotropical vine Dalechampia scandens (Euphorbiaceae) originating from environments of contrasting rainfall seasonality. Seeds produced by second greenhouse‐generation plants were measured and exposed to a favorable wet environment at different time intervals after capsule dehiscence and seed dispersal. We recorded the success and the timing of germination. All populations produced at least some dormant seeds, but seeds of populations originating from more seasonal environments required longer periods of after‐ripening before germinating. Within populations, larger seeds tended to require longer after‐ripening periods than did smaller seeds. These results indicate among‐population genetic differences in germination behavior and suggest that these populations are adapted to local environmental conditions. They also suggest that seed size may influence germination timing within populations. Ongoing changes in seasonality patterns in tropical dry forests may impose strong selection on these traits.
Highlights
Successful plant establishment in seasonal environments requires accurate timing of germination to match favorable environmental conditions
Because we were interested in variation in germination behavior in response to rainfall seasonality, we studied seed dor‐ mancy in six populations originating from regions characterized by different degrees of seasonality, that is, the contrast in precipitation between rainy and dry seasons (Figure 1, Table 1)
We evaluated whether the time from watering to germina‐ tion depended on the duration of after‐ripening or seed size in the second experiment
Summary
Successful plant establishment in seasonal environments requires accurate timing of germination to match favorable environmental conditions. We modeled the time to germination (log‐trans‐ formed) as a function of population, watering treatment (duration of after‐ripening), and seed size (fixed effects) and included sowing tray (block), maternal identity, and blossom identity nested within maternal identity as random effects. All analyses were performed using R 3.5.0 (R Core Team, 2018) In both experiments, the proportion of seeds germinating increased with longer exposure to dry conditions prior to watering, suggest‐ ing a gradual release from dormancy through after‐ripening of seeds (Figure 3, Supporting Information Table S1). The proportion of seeds germinating increased with longer exposure to dry conditions prior to watering, suggest‐ ing a gradual release from dormancy through after‐ripening of seeds (Figure 3, Supporting Information Table S1) This observation places D. scandens in the common class of nondeep physiological dormancy (PD sensu Baskin & Baskin, 2004). The Tovar population differed strongly from the other populations, while differences among the remaining populations were more subtle
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