Seed dispersal in heterogeneous landscapes: linking field observations with spatially explicit models

Abstract

Seed dispersal by animals drives persistence and colonization of the majority of fleshy‐fruited plants. Different factors have been identified as important in shaping patterns of seed deposition. These factors include habitat heterogeneity, movement patterns of frugivore species, and their feeding behavior. Most studies, however, have analysed the effect of one factor at the time, either with a modelling approach or from field observations. Here, we combine empirical data with spatially‐explicit models to explore the contribution of habitat availability and patterns of frugivore post‐feeding flight distances to the spatial patterns of seed dispersal. We found that both factors, distance from the mother tree and microhabitat identity, were shaping those patterns. Our results show that seed dispersal is tremendously heterogeneous and complex in space. The observed seed shadow is not the result of a single process but instead an intricate combination of distance and habitat selection. We suggest that the apparent combination of processes results from the simultaneous effects of distinct functional groups of frugivores.

Geographic consistency in the seed dispersal patterns of Taxus baccata L. in the Iberian Peninsula

“…We observed similar patterns at our study sites. For example, at Escobarejos, T. baccata female trees are mainly surrounded by conspecific males and open areas (Sanz, 2008;Lavabre et al, 2014). These were, indeed, the microhabitats receiving a greater fraction of bird-dispersed seeds in 2006, when T. merula was the dominant seed disperser.…”

“…Nonetheless, some studies have shown that seed dispersal patterns do not necessarily match with microhabitat availaibility (Bartuszevige & Gorchov, 2006;Lavabre et al, 2014). Actually, at Escobarejos, 84 % of the bird-dispersed seeds were found beneath female yews in both years when these barely cover 0.4% of the landscape (Lavabre et al, 2014).…”

“…Besides the spatial components, an important feature of plant-frugivore interactions is their temporal 3 Seed dispersal patterns of Yew fleshy-fruited trees (Sorbus aucuparia L., Ilex aquifolium L., and Taxus baccata) distributed along seasonal streams (Sanz, 2008;Lavabre et al, 2014). Although present at a low density, yew is the dominant tree species at this site, and the population included 21 adult trees, 15 females and 6 males.…”

“…For the "rock" microhabitat, due to the difficulty to install seed traps and their conspicuousness to animals (including frugivores), we collected the seeds directly from open quadrats, permanently marked on the rock substrate, with the same surface than seed traps. Seed predation by rodents is usually low in open microhabitats and it mostly occurs in late winter (Hulme, 1997;García et al, 2005a), and thus seed losses due to predation were considered negligible (see García et al, 2011;Carlo et al, 2013;Lavabre et al, 2014, for validation of the methodology). In Peña Mayor and Escobarejos, we also sampled seed deposition in permanently labelled open quadrats of 0.5×0.5 m, as the presence of abundant free-ranging cattle and human activities in these two sites prevented the use of seed traps.…”

The spatial complexity of seed movement: Animal‐generated seed dispersal patterns in fragmented landscapes revealed by animal movement models

“…The spatial complexity of seed dispersal patterns has motivated the development of new methods of data analysis to characterize the patterns of seed dispersal (Lavabre, Stouffer, Sanz, & Bascompte, 2014;Nathan et al, 2012;Robledo-Arnuncio et al, 2014). Habitat loss and fragmentation directly impact animal movement (Tucker et al, 2018), with significant negative flow-on effects for seed dispersal, including a reduction in seed dispersal distances (Jones, Duke-Sylvester, Leberg, & Johnson, 2017) and altered seed rain composition (McConkey et al, 2012).…”