Legacy effects of seed dispersal mechanisms shape the spatial interaction network of plant species in Mediterranean forests

Abstract

Seed dispersal by frugivores plays a key role in structuring and maintaining tree diversity in forests. However, little is known about how the spatial legacy of seed dispersal and early recruitment shapes spatial patterns and the spatial interaction network of plant species in mature forest communities. We analysed two fully mapped mixed Pine–Oak forest communities using spatial point pattern analysis to determine (a) the detailed structure of the intraspecific spatial patterns of saplings and adults, (b) the intra‐ and interspecific spatial interaction of saplings, adults and saplings relative to adults, (c) the spatial patterns of species richness at the community level and (d) whether seed dispersal mechanisms affect the plant–plant interaction networks and the ratio of adult to sapling neighbourhood densities used as surrogate for spatial self‐thinning. The intraspecific spatial patterns of saplings and adults showed in general complex nested cluster structures that were similar for sapling and adult stages, despite substantial self‐thinning in some dry‐fruited species. The spatial network of saplings was characterized by positive spatial interactions. Adults of several tree species facilitated saplings in their proximity; however, adults of dry‐fruited species, but not those of fleshy‐fruited ones, lost almost all positive interactions that occurred at the sapling stage. Besides, interaction strength between adults was positive and often significantly stronger if both species were fleshy‐fruited. At the community level, the forests were structured into multispecies clumps across all life stages. Synthesis. Our analyses highlight the importance of the spatial legacy of seed dispersal and early recruitment in the assembly of plant communities. Particularly, animal seed dispersal can lead to multispecies clusters and positive spatial associations across life stages in Mediterranean forests, with surprisingly little signatures of negative interactions. Our analysis suggests that changes of the spatial structure across plant life stages are driven by seed dispersal mechanisms and subsequent spatial self‐thinning, generating a spatial footprint at the sapling stage that conditions the long‐term interactions between adult plants. Combining spatial point pattern analysis with network analysis and species traits is a promising way to disentangle the processes underlying observed patterns of local diversity.

Persistence of Seed Dispersal in Agroecosystems: Effects of Landscape Modification and Intensive Soil Management Practices in Avian Frugivores, Frugivory and Seed Deposition in Olive Croplands

“…Vast areas of the Mediterranean lowlands have been progressively occupied through centuries by olive groves, rendering highly variegated natural landscapes into an olive monoculture (Weissteiner et al, 2011). Olive cropland has expanded at the expense of Mediterranean native forest, woodlands, and scrublands (seminatural woodland habitats, SNWH hereafter), particularly rich in fleshy-fruited plant species (Herrera, 1984a;Jordano, 1984) and where avian seed dispersal by birds represents a major driver of woody vegetation recovery and the long-term dynamics of ecological communities Alcántara, 2000, 2014;Perea et al, 2021). However, unlike some notable information on avian frugivore abundance and diversity (Rey, 1993(Rey, , 1995(Rey, , 2011Morgado et al, 2021), data on frugivory and seed dispersal in olive grove landscapes is anecdotal, restricted to fruit consumption during winter by the most abundant frugivores, or taken from a single or a small number of localities (Jordano and Herrera, 1981;Rey, 1992;Blanco et al, 1994;Rey and Valera, 1999;Delibes et al, 2012;Perea and Gutiérrez-Galán, 2016).…”

Spatial phylogenetic and phenotypic patterns reveal ontogenetic shifts in ecological processes of plant community assembly

“…A total of 15 and 10 woody plant species were found in the small plots of MFJ and MFS, respectively. However, the surrounding community in their corresponding large plots was also composed of other less abundant species (see Supporting information in Perea et al 2021b). The number of individuals of each species allowed for point pattern analyses of nine species in each community.…”

“…DBH > 10 cm for upper-canopy species). Concentrically to the large plot, we settled on a 50 × 50 m plot (small plot, hereafter), where we took the same variables for saplings (see Perea et al 2021b for further details). We considered saplings as plants with a DBH higher than 1 mm but lower than 1 cm, and without symptoms of being a reproductive individual (flower and/or fruits).…”

“…Spatial neighbourhood patterns, therefore, carry information about the operation of processes in the past, and they form the template for the processes operating in the future (Law et al 2009). In particular, ecological processes that occur in early life stages can leave long-lasting footprints in the spatial structure of adults (Perea et al 2020(Perea et al , 2021b. Then, comparisons of their spatial patterns, and the phylogenetic and phenotypic structure of their surrounding neighbourhoods, may improve our understanding of the processes and legacy effects involved in shaping plant communities (Moeur 1997, Plotkin et al 2002, Getzin et al 2008, Wang et al 2016, Wiegand et al 2017, Chun and Lee 2019.…”

Neighborhood Effects on Tree Mortality Depend on Life Stage of Neighbors

“…Due to the positive spatial association between adult trees and their offspring, more living adult trees occur in the area with aggregations of earlier stage conspecific neighbors ( Perea et al, 2021 ). Here, we found that when more conspecific earlier stage neighbors were clumped around the focal adult tree, its mortality was lower.…”