Oxalis seeds from the Cape Flora have a spectrum of germination strategies

PREMISE : Seed germination strategy has profound ecological and evolutionary consequences, with transitions between germination strategies receiving renewed recent attention. Oxalis from the Cape Flora, South Africa, has seeds with two contrasting germination strategies: orthodox and recalcitrant. The morphological gulf between these strategies (and potential intermediate morphologies) has been poorly quantified, with questions regarding their ecological function and evolution. We reconsidered this binary classification, emphasizing potential intermediate states. METHODS : Seed physiological traits were used to assign strategies to 64 Oxalis species. We tested for morphological/phenological signal corresponding to defined strategies with cluster, principal component, K-means clustering and discriminant analyses. RESULTS : We showed that an intermediate germination strategy does exist among Cape Oxalis, with two possible morphological groups within each strategy. These could reflect a continuum of germination states, where an ancestral orthodox strategy evolved toward a maximally recalcitrant peak, with a mosaic of intermediate states reflected in extant taxa. CONCLUSIONS : Environmental factors may affect germination strategy and distribution throughout the Cape because recalcitrant and intermediate species are confined to the winter rainfall region. They occupy specialized niches and may face adverse impacts under predicted climate change (hotter and drier winters), meriting focused future conservation.Appendix S1. Oxalis species with corresponding physiological, morphological, and phenological data. The seed, seedling, and combined seed‐and‐seedling data sets are recorded on three separate sheets.Appendix S2. Cluster dendrograms indicating the percentage difference between Oxalis species, based on discrete and continuous seed and seedling morphological and developmental data. Data from the seed (A), seedling (B), and combined seed‐and‐seedling (C) data set were analyzed. The majority of replicates per species cluster together coherently. Cluster analyses revealed coherent clustering of data into at least three (or four) clusters, supporting three germination strategies.Appendix S3. Individual factor maps of principal component analyses to visualize discrete and continuous Oxalis seed (A), seedling (B), and combined seed‐and‐seedling (C) morphological and developmental data for five replicates per species.Appendix S4. A composite of three seed physiological traits used to define germination strategies among Cape Oxalis.Appendix S5. Descriptions and interpretations of seed and seedling morphological and phenological traits associated with orthodox, intermediate, and recalcitrant Oxalis Groups A to F.Appendix S6. A key to variable factor names used in Fig. 2A–C. Abbreviations correspond to descriptions of seed, seedling, and combined seed and seedling data sets as indicated on three separate sheets.Appendix S7. Key to Oxalis species from Fig. 3. Group names and codes correspond to abbreviations used in this figure.The National Research Foundation for the Scarce Skills Doctoral Scholarship.http://www.wileyonlinelibrary.com/journal/AJBhj2019Plant Production and Soil Scienc