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Many nutritious seeds are commonly attacked by insects which feed on the seed reserves. However, studies have not fully explored the ecological implications of insect infestation in animal seed dispersal and subsequent plant regeneration. Our question is whether the fact that an infested seed still contains the larva or not might increase/decrease the probability of being successfully dispersed by animals. This study examines the effects of weevil-infested seeds on the natural regeneration of a rodent-dispersed oak species. Rodents showed a high ability to discriminate between sound and infested seeds, even when the larva was still inside. As a result, rodents caused differential seed dispersal for sound and infested seeds by modifying multiple aspects of the dispersal process. We found that, for the same seed weight, infested acorns with a larva still inside can contribute to natural regeneration (0.7 % of seedlings in next summer), although in comparison to sound acorns they suffered higher predation rates by rodents (both partial and complete), were removed later from the ground (less preferred), cached less frequently, and dispersed to shorter distances, which reduced their potential to colonize new environments. However, infested seeds with exit holes are notably less preferred by rodents and, when dispersed, they are mostly deposited on the litter (uncached) with shorter dispersal distances and lower emergence success. Thus, the probability that larval-holed acorns will produce viable seedlings is extremely low (null in this study). Whether infested seeds still contain a larva or not clearly determines the probability of being successfully dispersed. Premature seed drop prolongs the presence of the larva inside the acorn after seed drop, and could be a possible mechanism to allow dispersal of infested seeds.

Microsites where seeds arrive during the dispersal process determine plant reproductive success, affecting the quality of dispersal. Despite their crucial role for plant recruitment, very few studies have addressed spatio–temporal variations in microsites of seed arrival in complex seed‐disperser networks. Using an endozoochorous dispersal system, we characterized the microsites of seed arrival of eight fleshy‐fruited plant species dispersed by five mammal species during two consecutive seasons across three sites in a Mediterranean environment (n = 383 feces with seeds; 261 453 seeds). We evaluated spatial and temporal variations in the probability of a seed to arrive at open microsites or at microsites with varying plant cover, considering selection by frugivores and assessing the extent to which seeds of particular species arrived under conspecifics or heterospecifics. We found strong spatio–temporal variations in the amounts of seeds of the eight target species arriving at different microsites. These variations were strongly driven by frugivores’ selection of different landscape elements (i.e. open areas and microsites dominated by different plant species), which differed from expectations based on their local availability. In general, more seeds than expected arrived at vacant (open) microsites. Using bipartite network graphs to connect seeds with their arrival microsites, we found that the proportion of seeds of fleshy‐fruited species arriving near conspecifics or heterospecifics, or at vacant microsites, varied depending on the target plant species, but also on the frugivore species dispersing it, on the study site and on the dispersal season. Our study revealed marked spatio–temporal variations in the microsites of seed arrival, which will potentially have implications for the quality of dispersal effectiveness, ultimately affecting plant population dynamics and community structure. Such a strong context‐dependence in the microsites of seed arrival is likely to confer resilience against unpredictable environmental conditions, like those typical of Mediterranean ecosystems. [ABSTRACT FROM AUTHOR]

Embryo damage in seed predation is a common occurrence and has been generally considered equivalent to seed death. We hypothesize that seeds with proportionally larger embryos (radicle plus plumule) provide greater tolerance to seed damage by rodents, allowing successful germination. To test this hypothesis, we examined germination and estimated the contribution of embryo-damaged seeds to plant regeneration by comparing the dispersal patterns of intact and embryo-damaged seeds and the ecophysiological responses of their emerged seedlings in two oak species of contrasting embryo size. Our results show that embryo size was positively correlated with seed size in both oak species, but one ( Quercus lobata ) had proportionally longer embryos than the other ( Q. agrifolia ), revealing inter-specific differences in embryo size. Probability of embryo excision behavior (partial seed damage to extirpate the embryo) was positively associated with seed size but intensity of damage was relatively constant across all sizes. The species with proportionally longer embryos showed a stronger capacity to regenerate from embryo damage because longer embryos experienced reduced probability of total (lethal) embryo damage by rodents. Seed size and thus intraspecific embryo size only increased germination success in the species with shorter embryos, allowing larger seeds to escape full embryo damage. Seedlings from intact seeds performed better (greater plant biomass and higher chlorophyll and nitrogen index) than those from embryo-damaged seeds. However, seedlings from embryo-damaged seeds showed higher anthocyanin content, a possible response to seed damage. Intact and embryo-damaged acorns showed similar dispersal patterns by rodents (e.g. seed caching behavior and dispersal distances). Importantly, seed retrieval by rodents was significantly lower for embryo-damaged seeds, allowing greater seed survival and supporting the expectation that embryo excision behavior is a strategy to store seeds for longer periods. We conclude that tolerance to embryo damage is an important reproductive strategy that enables plant recruitment. Embryo size could play a crucial role in the evolutionary and ecological responses of seeds to animal predation. [ABSTRACT FROM AUTHOR]

The ability of animals to find and consume hoarded seeds (i.e. seed recovery) is a key stage within the seed dispersal process. However, the ecology of seed recovery is still poorly understood. Here, we analyze the factors controlling seed recovery by scatter-hoarding rodents in an oak-dominated temperate forest. We examined the relative importance of intrinsic seed traits (i.e. plant-driven) and extrinsic seed factors (i.e. animal-driven) on the probability of seed recovery. We found that seed recovery is mainly driven by extrinsic seed factors, mostly related to animal behavior (pilfering frequency, microsite preference, predation risk, burial depth and cache size). Important intrinsic traits such as seed size, seed quality and seed-drop timing were, on average, of lower significance in the probability of seed recovery (2.8-times less important than extrinsic factors); only seed quality was an important intrinsic trait. On the other hand, larger and nutritionally more valuable seeds showed a removal-recovery tradeoff as they enhance seed removal and hoarding (increasing dispersal quality) but also favour seed recovery (increasing predation). We find that other mechanisms beyond seed traits (e.g. masting) are needed to decrease seed recovery and, thus, increase seed survival. We conclude that, as seed recovery is mostly driven by animal behavioural factors, it substantially differs from other previous stages of the seed dispersal process that are more dependent on seed traits. We argue that seed recovery needs further attention to advance our understanding of the ecology of seed dispersal and the role of secondary dispersers as a selective force for seeds. [ABSTRACT FROM AUTHOR]

Animals may disperse cultivated trees outside the agricultural land, favoring the naturalization or, even, the invasiveness of domestic plants. However, the ecological and conservation implications of new or unexplored mutualisms between cultivated trees and wild animals are still far from clear. Here, we examine the possible role of an expanding and, locally, overabundant pigeon species ( Columba palumbus ) as an effective disperser of domestic olive trees ( Olea europaea ), a widespread cultivated tree, considered a naturalized and invasive species in many areas of the world. By analyzing crop and gizzard content we found that olive fruits were an important food item for pigeons in late winter and spring. A proportion of 40.3% pigeons consumed olive seeds, with an average consumption of 7.8 seeds per pigeon and day. Additionally, most seed sizes (up to 0.7 g) passed undamaged through the gut and were dispersed from cultivated olive orchards to areas covered by protected Mediterranean vegetation, recording minimal dispersal distances of 1.8–7.4 km. Greenhouse experiments showed that seeds dispersed by pigeons significantly favored the germination and establishment in comparison to non-ingested seeds. The ability of pigeons to effectively disperse domestic olive seeds may facilitate the introduction of cultivated olive trees into natural systems, including highly-protected wild olive woodlands. We recommend harvesting ornamental olive trees to reduce both pigeon overpopulation and the spread of artificially selected trees into the natural environment. [ABSTRACT FROM AUTHOR]

European white elm (Ulmus laevis Pallas) populations are scarce, small and fragmented in the Iberian Peninsula. Due to these characteristics the indigenous status of the species in the region has been questioned, whilst the species' role in Iberian riparian forest ecology has been neglected. Herein we review past studies regarding this species' distribution and ecology in the Iberian Peninsula, with special emphasis on the establishment of conservation priorities. We first present a collection of palaeogeographic, historic and genetic data suggesting that the Iberian Peninsula was a glacial refuge for U. laevis. Secondly, we analyse U. laevis distribution in relation to soil physicochemical properties and water availability in Spain. Following this, we focus on the reproductive biology of the species, and investigate the effect of masting and empty seed production on predation and regeneration establishment. Finally, based on this knowledge, we propose conservation policies for U. laevis in the Iberian Peninsula. [ABSTRACT FROM AUTHOR]

Various environmental factors may influence the foraging behaviour of seed dispersers which could ultimately affect the seed dispersal process. We examined whether moonlight levels and the presence or absence of rodent shelter affect rodent seed removal (rate, handling time and time of removal) and seed selection (size and species) among seven oak species. The presence or absence of safe microhabitats was found to be more important than moonlight levels in the removal of seeds. Bright moonlight caused a different temporal distribution of seed removal throughout the night but only affected the overall removal rates in open microhabitats. Seeds were removed more rapidly in open microhabitat (regardless of the moon phase), decreasing the time allocated to seed discrimination and translocation. Only in open microhabitats did increasing levels of moonlight decrease the time allocated to selection and removal of seeds. As a result, a more precise seed selection was made under shelter, owing to lower levels of predation risk. Rodent ranking preference for species was identical between full/new moon in shelter but not in open microhabitats. For all treatments, species selection by rodents was much stronger than size selection. Nevertheless, heavy seeds, which require more energy and time to be transported, were preferentially removed under shelter, where there is no time restriction to move the seeds. Our findings reveal that seed selection is safety dependent and, therefore, microhabitats in which seeds are located (sheltered versus exposed) and moonlight levels in open areas should be taken into account in rodent food selection studies. [Copyright &y& Elsevier]

Abstract: Nuts are heavy and nutritious seeds that need animals to be successfully dispersed. Most studies address nut removal by a single animal species once seeds fall onto the ground. However, nuts are also accessible before the seed drop and usually to a wide guild of seed foragers. This study examines the factors controlling arboreal seed removal in oak–beech forests within the whole guild of nut foragers. We found that seed-dispersing rodents (Apodemus sylvaticus) were the main acorn removers in the oaks (up to 3.75m height), with a rapid seed encounter and a high removal rate. However, rodents did not climb the beech trees, probably due to their smoother bark in comparison to oak bark and/or the lower nutritional value of beechnuts with regard to acorns. Jays (Garrulus glandarius) were more abundant in oak stands (both dense and scattered) and clearly preferred acorns to beechnuts whereas nuthatches (Sitta europaea) were more abundant in beech stands and preferred beechnuts to acorns. Non-storing birds such as great tits (Parus major) also removed acorns and beechnuts, especially in the stands where oaks are dominant. Jays and rodents preferred sound seeds over insect-infested seeds but such a preference was not found for nuthatches. This study highlights that pure beech stands showed a reduced guild of arboreal nut foragers in comparison to oak stands. This different guild could probably affect the spatial patterns of seed dispersal, with a proportionally higher number of long dispersal events for acorns (mostly jay-dispersed) than for beechnuts (mostly nuthatch-dispersed). Long-distance dispersal of beechnuts (by jays) is determined by the presence of other preferred species (oaks) and their frequency of non-mast years. Seed location in different habitats strongly determines the contribution of different arboreal removers (including climbing rodents) and their removal speed, leading to a differential seed fate that will eventually affect tree regeneration. As nuthatches are sedentary birds, it is important to maintain old and dead trees where they can breed (crevices), forage (arthropods) and store seeds in order to favor beechnut dispersal and gene flow. By maintaining or favoring oak trees within beech stands we will ensure a wider guild of arboreal nut dispersers. [Copyright &y& Elsevier]

Fleshy fruits fall on to the ground together with cleaned seeds previously ingested by primary dispersers, offering a wide range of fruits and seeds to the ground foragers. Although nutritional properties strongly differ between fruits and seeds, this different seed presentation (cleaned seeds versus seeds within the pulp) has not been addressed in seed removal studies. This study reports on the removal of fruits versus their seeds in five fleshy-fruited species in a temperate forest. We found that rodents removed most of the seeds and partially consumed most of the fruits, preferring seeds to fruits. Rodents bit the fruits to extract the seeds, leaving most of the pulp. We found a preference ranking for the seeds (Sorbus aucuparia>Ilex aquifolium>Sorbus aria>Rosa canina>Crataegus monogyna) but no preferences were found for the fruits, probably due to their similarities in pulp constituents. Seed and fruit choice were affected by chemical and physical properties and not by their size. The presence of alternative and preferred seeds (nuts) delayed the encounter of the fruits and seeds and diminished their removal rates. We found that higher rodent abundance is not necessarily associated with higher removal rates of fleshy fruits. Rodent abundance, fruit size and seed size are minor factors in the removal of fleshy fruits and their seeds. This study underlines that scatter-hoarding rodents are important removers of fleshy fruits and their seeds, producing a differential seed removal depending on the seed presentation (with or without pulp), the nutritional properties of the seeds (but not of the fruits) and the presence of alternative food. [ABSTRACT FROM PUBLISHER]