Drought tolerance increases with seed size in a semiarid grassland from southern Mexico
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Drought tolerance increases with seed size in a semiarid grassland from southern Mexico Marcela Martı´nez-Lo´pez . Clara Tinoco-Ojanguren
. Carlos Martorell
Received: 24 March 2020 / Accepted: 3 July 2020 Ó Springer Nature B.V. 2020
Abstract Due to increased reserves available to face adverse conditions, drought tolerance should increase with seed size. This has been confirmed in the laboratory, but under field conditions the pattern has not yet been found. We tested whether drought tolerance increases with seed size under field conditions in a semiarid grassland. We recorded the performance (germination, survival, and growth) of 12 species with different-sized seeds sown under conditions associated with hydric stress: along a natural stress gradient related to soil depth, and under experimentally manipulated irradiance levels that affected evaporation and thus soil humidity. We estimated drought tolerance indices for each Communicated by Daniel L Potts.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11258-020-01056-7) contains supplementary material, which is available to authorized users. M. Martı´nez-Lo´pez C. Martorell (&) Departamento de Ecologı´a y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Auto´noma de Me´xico, Circuito Exterior s/n, Ciudad Universitaria, 04510 Mexico, Mexico e-mail: [email protected] C. Tinoco-Ojanguren Departamento de Ecologı´a de la Biodiversidad, Instituto de Ecologı´a, Universidad Nacional Auto´noma de Me´xico, Blvd L.D. Colosio s/n Esquina Madrid, 83250 Hermosillo, Sonora, Mexico
performance metric, as well as a multivariate tolerance index that integrated the different components of performance. Each index was regressed on seed size accounting for phylogenetic effects. Seed size had little effect on individual metrics, but the joint evidence from all tests revealed a clear positive correlation with seed size. The multivariate tolerance index also increased with seed size, confirming the expected relationship. This suggests that comprehensive measures encompassing the whole life cycle may be required to characterize drought tolerance properly and may explain why this pattern has remained elusive in most studies. Also, we used a narrow range of seed sizes, so there is the possibility that the relationship between seed size and tolerance holds only for smallseeded species. Keywords Germination Growth Hydric stress Seed mass Soil depth Survival
Introduction Seedlings that come from large seeds may perform better than those from small seeds in stressful environments. These patterns hold both within and across species (Facelli 2008; Khurana and Singh 2004; Leishman and Westoby 1994; Leishman et al. 2000). Large seeds contain more reserves, enabling the
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successful establishment of seedlings under adverse conditions that impede the rapid acquisition of resources (Baker 1972; Beaton and Dudley 2010; Facelli 2008; Grubb 1998; Leck et al
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