Examinando por Autor "Nabais, Cristina"

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Pre-dispersal predation effect on seed packaging strategies and seed viability
(2016) DeSoto, Lucía; Tutor, David; Torices, Rubén; Rodríguez-Echeverría, Susana; Nabais, Cristina
An increased understanding of intraspecific seed packaging (i.e. seed size/number strategy) variation across different environments may improve current knowledge of the ecological forces that drive seed evolution in plants. In particular, pre-dispersal seed predation may influence seed packaging strategies, triggering a reduction of the resources allocated to undamaged seeds within the preyed fruits. Assessing plant reactions to pre-dispersal seed predation is crucial to a better understanding of predation effects, but the response of plants to arthropod attacks remains unexplored. We have assessed the effect of cone predation on the size and viability of undamaged seeds in populations of Juniperus thurifera with contrasting seed packaging strategies, namely, North African populations with single-large-seeded cones and South European populations with multi-small-seeded cones. Our results show that the incidence of predation was lower on the single-large-seeded African cones than on the multi-small-seeded European ones. Seeds from non-preyed cones were also larger and had a higher germination success than uneaten seeds from preyed cones, but only in populations with multi-seeded cones and in cones attacked by Trisetacus sp., suggesting a differential plastic response to predation. It is possible that pre-dispersal seed predation has been a strong selective pressure in European populations with high cone predation rates, being a process which maintains multi-small-seeded cones and empty seeds as a strategy to save some seeds from predation. Conversely, pre-dispersal predation might not have a strong effect in the African populations with single-large-seeded cones characterized by seed germination and filling rates higher than those in the European populations. Our results indicate that differences in pre-dispersal seed predators and predation levels may affect both selection on and intraspecific variation in seed packaging.
Variation in seed packaging of a fleshy‐fruited conifer provides insights into the ecology and evolution of multi‐seeded fruits
(2017) DeSoto, Lucía; Torices, Rubén; Rodríguez-Echeverría, Susana; Nabais, Cristina
The study of intraspecific seed packaging (i.e. seed size/number strategy) variation across different populations may allow better understanding of the ecological forces that drive seed evolution in plants. Juniperusthurifera (Cupressaceae) provides a good model to study this due to the existence of two subspecies differentiated by phenotypic traits, such as seed size and cone seediness (number of seeds inside a cone), across its range. The aim of this study was to analyse seed packaging (seed mass and cone seediness) variation at different scales (subspecies, populations and individuals) and the relation- ship between cone and seed traits in European and African J. thurifera populations. After opening more than 5300 cones and measuring 3600 seeds, we found that seed packaging traits followed different patterns of variation. Large-scale effects (region and population) significantly contributed to cone seediness variance, while most of the seed mass variance occurred within individuals. Seed packaging differed between the two sides of the Mediterranean Sea, with African cones bearing fewer but larger seeds than the European ones. However, no differences in seed mass were found between populations when taking into account cone seediness. Larger cones contained more pulp and seeds and displayed a larger variation in individual seed mass. We validated previous reports on the intraspecific differences in J. thurifera seed pack- aging, although both subspecies followed the same seed size/number trade-off. The higher seediness and variation in seed mass found in larger cones reveals that the positive relationship between seed and cone sizes may not be straightforward.We hypothesise that the large variation of seed size found within cones and individuals in J. thurifera, but also in other fleshy-fruited species, could represent a bet-hedgingstrat- egy for dispersal.