Abstract
Seeds play a major role in plant species persistence and expansion, and therefore they are essential when modeling species dynamics. However, homogeneity in seed traits is generally assumed, underestimating intraspecific trait variability across the geographic space, which might bias species success models. The aim of this study was to evaluate the existence and consequences of interpopulation variability in seed traits of the invasive species Carpobrotus edulis at different geographical scales. We measured seed production, morphology, vigour and longevity of nine populations of C. edulis along the Catalan coast (NE Spain) from three differentiated zones with a human presence gradient. Geographic distances between populations were contrasted against individual and multivariate trait distances to explore trait variation along the territory, evaluating the role of bioclimatic variables and human density of the different zones. The analysis revealed high interpopulation variability that was not explained by geographic distance, as regardless of the little distance between some populations (< 0.5 km), significant differences were found in several seed traits. Seed production, germination, and persistence traits showed the strongest spatial variability up to 6000% of percent trait variability between populations, leading to differentiated C. edulis soil seed bank dynamics at small distances, which may demand differentiated strategies for a cost-effective species management. Seed trait variability was influenced by human density but also bioclimatic conditions, suggesting a potential impact of increased anthropogenic pressure and climate shifts. Geographic interpopulation trait variation should be included in ecological models and will be important for assessing species responses to environmental heterogeneity and change.
Highlights
Seeds, the reproductive units of flowering plants, constitute one of the main factors defining the persistence and expansion of species and play a crucial role in determining species success (Saatkamp et al 2014; Gioria and Pyšek 2016)
Considering the three geographically distant zones, seeds from the populations at Costa Brava (CB) showed significantly higher seed mass and viability percentages compared to Maresme and Cap de Creus but high variability was found between populations within each zone (Fig. 2b, d)
Seed traits types showed a differential degree of trait variation, suggesting different traits sensitivity, supporting hypothesis 2 that expected high interpopulation variability in key seed traits determining soil seed bank dynamics such as seed production, germination, and persistence
Summary
The reproductive units of flowering plants, constitute one of the main factors defining the persistence and expansion of species and play a crucial role in determining species success (Saatkamp et al 2014; Gioria and Pyšek 2016). Complex biochemical regulation prevents seeds to germinate, resisting for several years at the soil seed bank (Kucera et al 2005). Longevous seeds may increase the capacity of a species to persist in a particular site and increase the impact of invasive species due to increased needs of post-eradication management (Gioria et al 2016). Seed morphology, production, viability, germination, biochemistry, and persistence may have important implications in species success (Saatkamp et al 2019), as they offer an approximated reflect of the soil seed bank dynamics (Gioria and Pyšek 2016)
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