Plant species variation in bottom‐up effects across three trophic levels: a test of traits and mechanisms

1. An increasing number of studies have addressed the mechanisms by which plant inter‐specific variation influence interactions at higher trophic levels, but little is known about the underlying plant traits driving these dynamics. 2. Here we investigated the effects of host plant species on herbivore‐parasitoid interactions and the underlying traits driving such effects. For this, we measured the abundance of seed‐eating bruchids and their parasitoids across seven sympatric populations of the bean species Phaseolus coccineus and Phaseolus vulgaris in Central Mexico. To investigate the mechanisms underlying differences between bean species in bruchid‐parasitoid interactions, we carried out two laboratory experiments to test whether bruchid and parasitoid performance differed between plant species. We also measured seed size and phenolic compounds to investigate if seed traits mediate bruchid‐parasitoid interactions by influencing herbivore susceptibility or resistance to parasitoids. 3. Field surveys revealed that the rate of parasitoid recruitment to bruchids was significantly higher on P. vulgaris than on P. coccineus. Subsequent laboratory bioassays indicated that bruchids developed more slowly and exhibited lower fitness on P. vulgaris seeds than on P. coccineus seeds. Accordingly, we found that bean species differed in seed size, with P. vulgaris having smaller (less nutritious) seeds, which explains why bruchid development was slower on this plant species. 4. These results provide a mechanism for why bruchids exhibited higher parasitism rates on seeds of P. vulgaris in the field which could be due to Slow‐Growth/High‐Mortality effects, a smaller physical refuge provided by the seed, or both factors. The roles of these mechanisms remain inconclusive without further study.     

Three–way interactions between Acacia, large mammalian herbivores and bruchid beetles - a review

Large mammalian herbivores are both predators and dispersers of Acacia seeds. While some of the seeds are destroyed during passage through the herbivore's digestive tract, others are defecated unharmed. Ingestion by large herbivores facilitates germination by scarification of the seed coat. The extent of the influence of herbivores on seed dispersal and germination depends on seed retention time and tooth size, which are both positively correlated with body size. Infestation by bruchid beetles (Bruchidae) reduces Acacia germination. Herbivores may reduce bruchid infestation in several ways. Larvae in recently infested seeds are killed by stomach acids penetrating the seed through the larval entry hole. Seeds that are partly excavated by burrowing larvae in more advanced stages may be crushed by the herbivore's teeth. Lastly, but probably most crucially, herbivores simply remove seeds from the natal tree prior to infestation or at least prior to reinfestation. The timing and magnitude of herbivory is crucial for both the reduction of bruchid infestation and Acacia seedling establishment. Although it is widely agreed that a three–way interaction exists between bruchid beetles, Acacia trees and large mammalian herbivores, it is also apparent that the relationship is highly complex and is not yet completely understood.     

The role of chemical cues in host finding and acceptance by Callosobruchus chinensis

We studied the response of female Callosobruchus chinensis to chemical cues emitted by cowpea seeds at different stages of bruchid infestation (uninfested, egg carrying, L1-, and L4-infested). Olfactory attractiveness was determined in Y-tube olfactometer assays by testing individual seed categories against either clean air or uninfested seeds. Oviposition preferences between uninfested and infested seeds were determined in petri-dish choice-experiments. The olfactometer assays revealed that weevils discriminate between seeds containing different stages of developing bruchids on the basis of olfactory cues. While odors from uninfested and egg-carrying seeds acted as attractants, odors from L1- and L4-infested seeds failed to induce a positive response by the bruchids. When given a choice between uninfested and infested seeds in the olfactometer, weevils preferred uninfested seeds over L1- and L4-infested seeds, but failed to distinguish between uninfested and egg-carrying seeds. In the oviposition experiment as well, bruchids showed a distinct preference for uninfested seeds when offered in combination with L1- and L4-infested seeds. This experiment further showed a reduced acceptance of egg carrying seeds. Our results indicate that C. chinensis females use chemical information during both host searching and host acceptance. Volatiles from uninfested or egg carrying seeds act as attractants, while deterrence increases as development of bruchid immature stages progresses.     

Secondary seed dispersal by ants in Neotropical cerrado savanna: species‐specific effects on seeds and seedlings of Siparuna guianensis (Siparunaceae)

1. Most woody plant species in tropical habitats are primarily vertebrate‐dispersed, but interactions between ants and fallen seeds and fruits are frequent. This study assesses the species‐specific services provided by ants to fallen arillate seeds of Siparuna guianensis, a primarily bird‐dispersed tree in cerrado savanna. The questions of which species interact with fallen seeds, their relative contribution (versus vertebrates) to seed removal, and the potential effects on seedling establishment are investigated. 2. Seeds are removed in similar quantities in caged and control treatments, suggesting that ants are the main dispersers on the ground. Five ant species attended seeds. Pheidole megacephala (≈0.4 cm) cooperatively transported seeds, whereas the smaller Pheidole sp. removed the seed aril on spot. Large (> 1.0 cm) Odontomachus chelifer, Pachycondyla striata, and Ectatomma edentatum individually carried seeds up to 4 m. Bits of aril are fed to larvae and intact seeds are discarded near the nest entrance. 3. Overall, greater numbers of seedlings were recorded near ant nests than in control plots without nests. This effect, however, was only detected near P. megacephala and P. striata nests, where soil penetrability was greater compared with controls. Soil nutrients did not differ between paired plots. 4. This study confirms the prevalence of ant–seed interactions in cerrado and shows that ant‐derived benefits are species‐specific. Ant services range from seed cleaning on the spot to seed displacement promoting non‐random spatial seedling recruitment. Although seed dispersal distances by ants are likely to be shorter than those by birds, our study of S. guianensis shows that fine‐scale ant‐induced seed movements may ultimately enhance plant regeneration in cerrado.     

Interaction between ungulates and bruchid beetles and its effect on <Emphasis Type="Italic">Acacia</Emphasis> trees: modeling the costs and benefits of seed dispersal to plant demography

Integrative studies of plant–animal interactions that incorporate the multiple effects of interactions are important for discerning the importance of each factor within the population dynamics of a plant species. The low regeneration capacity of many Acacia species in arid savannas is a consequence of a combination of reduction in seed dispersal and high seed predation. Here we studied how ungulates (acting as both seed dispersers and herbivores) and bruchid beetles (post-dispersal seed predators) modulate the population dynamics of A. raddiana, a keystone species in the Middle East. We developed two simulation models of plant demography: the first included seed ingestion by ungulates and seed predation by bruchids, whereas the second model additionally incorporated herbivory by ungulates. We also included the interacting effects of seed removal and body mass, because larger ungulates destroy proportionally fewer seeds and enhance seed germination. Simulations showed that the negative effect of seed predation on acacia population size was compensated for by the positive effect of seed ingestion at 50 and 30% seed removal under scenarios with and without herbivory, respectively. Smaller ungulates (e.g., <35 kg) must necessarily remove tenfold more seeds than larger ungulates (e.g., >250 kg) to compensate for the negative effect of seed predation. Seedling proportion increased with seed removal in the model with herbivory. Managing and restoring acacia seed dispersers is key to conserving acacia populations, because low-to-medium seed removal could quickly restore their regeneration capacity.     

Unexpected relationships and valuable mistakes: non‐myrmecochorous Prosopis dispersed by messy leafcutting ants in harvesting their seeds

Abstract Ants generally disperse seeds while feeding on fruits or structures attached to the seed. Seed dispersal as a by‐product of seed predation (dyszoochory) was recognized in specialized harvester ants, but not in ants predating seeds opportunistically. Leafcutting ants are the main herbivores in much of the Neotropics, and they have been reported to remove fruits and seeds, but their role as seed predators and dispersers has not been acknowledged. Prosopis flexuosa D.C. (Fabaceae, Mimosoideae) is the most abundant tree species in the central Monte Desert, Argentina, and it is likely to depend on secondary animal dispersal. Mammalian frugivores are usually considered its main dispersers, but the opportunity for dispersal may be small since the removal of fruits and seeds by seed predators is very intense. The objective of this study was to identify which ant species interact with P. flexuosa fruits and to evaluate their relative importance as seed predators and dispersers. In a field experiment, whole and segmented pods were offered and several ant species exploiting the fruits were identified. Additionally, all pod segments remaining around nests of the three ant species able to remove them (the leafcutters Acromyrmex lobicornis Emery and Acromyrmex striatus Roger, and Pheidole bergi Mayr) were examined during and after the P. flexuosa primary dispersal season. Up to 753 pod segments and 90 sound seeds were found accumulated in a circle of 1 m radius over nests of A. lobicornis, and even more in an examined trail. Acromyrmex striatus left a smaller proportion of sound seeds and P. bergi left a smaller number of pod segments. All tendencies were similar during shorter known periods of accumulation. Leafcutting ants are acting as important seed predators, and ‘by mistake’ may be dispersing a key non‐myrmecochorous tree. This is an unexplored path in the seed dispersal cycle of P. flexuosa that challenges the tendency to predict interactions based on classifications made with other goals.     

Aphid infestation promotes survival of a seed predator: observations and experiments on a tritrophic community module

We investigated whether aphid presence and abundance influence the survival of an endophagous pre-dispersal seed predator of the same host plant. We studied a terrestrial community module consisting of one plant (Laburnum anagyroides) and four insect species/groups (an aphid, Aphis cytisorum, a pre-dispersal seed predator bruchid, Bruchidius villosus, aphid-attending ant species, and parasitoids of the bruchid). Two complementary investigations were carried out in parallel: (a) a plant-aphid-ant complex was experimentally manipulated by excluding aphids, ants, or both for 5 years to assess their impacts on the seed predator’s survival and parasitism rate; and (b) different aphid infestation levels on randomly selected infructescences were correlated with plant traits, nutrient allocation pattern, and variables of seed predator’s survival, such as the number of eggs laid and adults emerged influenced by parasitoid activity, for 7 years. We found that ants did not affect bruchid oviposition negatively, but egg-parasitism was significantly decreased by their presence. Plant traits, such as the number of seeds and seed mass, as well as seed predator performance were negatively affected by heavy aphid infestation. Seed predator -infested seeds had no effect on the mass of remaining seeds in the pods. This study suggests that aphids were nevertheless promoting bruchid abundance and survival, depending on their infestation rate.     

The Influence of Ants on the Foraging Behavior of Birds in an Agroforest1

Ants limit bird foraging success via interference or exploitative competition. We compared bird foraging (number and duration of visits, bird species visiting) on ant (Azteca instabilis)‐infested and ant‐free tropical trees (Inga micheliana and Alchornea latifolia). Ants did not affect the number of bird visits or the number of species visiting. Ant presence shortened visit duration (overall and for insectivores) only on A. latifolia where ant activity was higher. Ants may thus hinder bird foraging on some tropical trees potentially shaping how predators affect arthropod communities; yet ant effects depend on bird foraging guild and ant activity.     

Pogonomyrmexcunicularius as the keystone disperser of elaiosome‐bearing Jatropha excisa seeds in semi‐arid Argentina

Myrmecochory or seed dispersal by ants is often described as a diffuse mutualism, because many of the ant species that function as partners are considered to be similar in terms of the frequency and consequences of their interactions. In this work, we test this assumption by conducting ant community surveys and seed removal experiments in six study sites located within a semi‐arid region of northwest Argentina. At each site, we characterized the ant assemblage that interacted with the seeds of Jatropha excisa Griseb. (Euphorbiaceae), an ant‐dispersed native shrub. Our results demonstrate that seed removal was dominated by one species, Pogonomyrmex cunicularius Mayr (Hymenoptera: Formicidae: Myrmicinae), which was responsible of 84% of the observed seed removal events. Although several ant species were attracted to the elaiosome‐bearing seeds of J. excisa, seed removal did not depend on ant community composition (species richness and ant activity) but was significantly influenced by the abundance of P. cunicularius. Its physical, behavioral, and ecological attributes are common with other ant species that have been characterized as keystone seed dispersers in other regions of the world. Nest feeding with marked seeds revealed that once P. cunicularius ants consume the elaiosomes, seeds are left inside the nests undamaged and at an appropriate depth for emergence. Our results support the hypothesis that myrmecochory is often an unevenly diffuse mutualism (i.e., one partner species is particularly important) and that at a local scale P. cunicularius is the keystone seed disperser of J. excisa.     

Bottom-up and top-down effects in a pre-dispersal seed predation system: are non-predated seeds damaged?

Seed predators that severely affect seed germination rates are well known for many plant species. Here, we hypothesised that due to differences in resource allocation within fruits, seed predation can negatively affect non-predated seeds in infested fruits when predation occurs during fruit maturation (a ‘top-down’ effect). We addressed this question using a system of bruchid beetles on Mimosa trees and we also investigated whether seed quality (nitrogen concentration) affects beetle body mass, which would have implications for adult fitness (‘bottom-up’ effect). To assess spatial variation, bottom-up and top-down effects were investigated in two plant populations. Nitrogen concentration was significantly higher in seeds from non-infested fruits than from infested fruits. This supports the hypothesis that resource allocation may differ between seeds from infested and non-infested fruits. Germination experiments showed that seeds from non-infested fruits germinated better than non-predated seeds from infested fruits. It was also confirmed that seed quality affected bruchid body mass. There was also evidence that more resources were taken from well-developed seeds. These results showed that seed predation can damage non-predated seeds.     

Relationship Among Phenolic Contents,Seed Predation,and Physical Seed Traits in <Emphasis Type="Italic">Mimosa bimucronata</Emphasis> Plants

Phenolic contents were compared between Mimosa bimucronata seeds from infested and non-infested fruits to assess induced defense response. By measuring leg length of the bruchid beetle Acanthoscelides schrankiae, we verified whether phenolic contents affected bruchid body size. In addition, the relationship between physical seed traits and phenolic contents was examined. Results showed that seeds from infested fruits had significantly greater phenolic contents than seeds from non-infested fruits, which suggested induced defense. Body size variation in A. schrankiae was marginally nonsignificant according to phenolic contents among plants (negative trend), indicating that phenols may interfere directly with bruchid performance. Seeds that were more irregularly shaped had significantly greater phenolic contents than those that were more uniform. Therefore, the most perfectly spherical seeds may be more vulnerable to seed predation, and our results suggest that the production of phenolic compounds was increased in infested fruits, which in turn may affect A. schrankiae development.     

Large African herbivores,bruchid beetles and their interactions with Acacia seeds

This study investigated the interactions of large African herbivores and bruchid seed beetles with Acacia seeds. The germination of bruchid-infested and uninfested seeds was compaed. The effects of pod consumption by large herbivores on bruchid infestation and seed germination was also assessed. Bruchid-infested seeds did germinate, and the germination of bruchid-infested and uninfested A. tortilis, A. nilotica and A. hebeclade seeds did not differ. Pod ingestion by large herbivores lowered the bruchid infestation of consumed and defaecated seeds compared to uningested seeds. Uninfested, ingested and voided A. tortilis seeds germinated seeds. Furthermore, infested A. tortilis seeds egested by giraffe, kudu and ostrich germinated better than infested, uningested seeds. Pod ingestion by large herbivores may reduce bruchid infestation, increase Acacia seed germination and therefore increase potential Acacia seedling recruitment.     

The role of Rhytidoponera metallica (Hymenoptera,Formicidae) in facilitating post‐fire seed germination of three ant‐dispersed legume species

The fire avoidance hypothesis proposes that a benefit of seed dispersal by ants (myrmecochory) is to protect seeds from being killed during fire and to facilitate post‐fire germination of seeds that require heat shock to break their physical dormancy. The aim of this study was to quantify the effect of fire and seed burial by a predominant seed‐dispersing ant, Rhytidoponera metallica (subfamily: Ectatomminae) on germination levels of three ant‐dispersed legume species (Pultenaea daphnoides, Acacia myrtifolia and Acacia pycnantha). Experimental burial of seeds within aluminium cans at a site prior to being burnt and at an adjacent unburnt site showed that fire increased germination levels, particularly for seeds buried at 1‐ and 2‐cm deep and that overall, germination levels differed among the three plant species. To quantify seed burial depths and post‐fire germination levels facilitated by R. metallica ants, seeds were fed to colonies prior to fire at the burnt and unburnt sites. Of the seeds buried within nests that were recovered, between 45% and 75% occurred within the upper 6 cm of the soil profile, although unexpectedly, greater percentages of seeds were recovered from the upper 0–2 cm of nests in the unburnt site compared with nests in the burnt site. Germination levels of buried seeds associated with R. metallica nests ranged from 21.2% to 29.5% in the burnt site compared with 3.1–14.8% in the unburnt site. While increased seed germination levels were associated with R. metallica nests following fire, most seeds were buried at depths below those where optimal temperatures for breaking seed dormancy occurred during the fire. We suggest that R. metallica ants may provide fire avoidance benefits to myrmecochorous seeds by burying them at a range of depths within a potential germination zone defined by intra‐ and inter‐fire variation in levels of soil heating.     

Assessment of the Biological Control Impact of Seed Predators on the Invasive Shrub Acacia nilotica (Prickly Acacia) in Australia

An impact assessment study was undertaken to determine seed predation rates by two bruchid beetles, Bruchidus sahlbergi Schilsky and Caryedon serratus Olivier, on the invasive shrub Acacia nilotica (L.) Willd. ex Del. The former bruchid was released as a biological control agent for A. nilotica, whereas the latter is naturalized in Australia. We attempted to determine the dynamics and magnitude of bruchid predation, following a number of differing reports of their effectiveness. To investigate the importance of seed availability on bruchid numbers, we compared seed death in high- and low-seed-density habitats, both before and after pods had dropped from tree branches. Bruchid predation was initially low (<2%) in pods on tree branches in both habitats, but increased abruptly to 12% in riparian and 32% in nonriparian exclosures by the third collection date. Bruchid numbers then crashed to below 2% in both habitats, when pods dropped to the ground. B. sahlbergi predation later increased markedly (up to 65%) again at high-pod-density sites. No further increase in predation took place beyond this level. Seed predation by C. serratus was found to be minimal (<5% of seeds infested) throughout the monitoring period. We suggest that seed predation by the bruchids, prior to pod drop and removal by cattle, is insufficient to cause major impacts on A. nilotica populations. Bruchid seed damage is likely to be significant only in situations with low cattle numbers, where cattle cannot remove the majority of fallen seed pods or where cattle are excluded. Exclusion of cattle from some areas within A. nilotica-invaded landscapes to potentially increase bruchid effectiveness is proposed. The demographic impact of optimal A. nilotica seed losses is discussed.     

Dispersal for distance? Acacia ligulata seeds and meat ants Iridomyrmex viridiaeneus

Abstract Ant seed dispersal distances are typically small, averaging less than 1 m in published studies. Here, a new record (180 m) for ant seed dispersal distance is reported, and preliminary observations are made on the interaction between meat ants Iridomyrmex viridiaeneus Viehmeyer (Hymenoptera: Formicidae) and diaspores of the sandhill wattle, Acacia ligulata A. Cunn. ex Benth. (Fabaceae) in Kinchega National Park, New South Wales (NSW), Australia. Iridomyrmex viridiaeneus moved diaspores over distances of 7–180 m (mean 93.9 m) from the source trees to their nests, removed the arils underground and discarded the seeds over a 3000‐m² area surrounding the nest. A germination trial determined that the viability of discarded seeds was 40%, with 80% of the viable seeds in a dormant condition. Although the cumulative effects of I. viridiaeneus on A. ligulata recruitment require further investigation, this study and others raise the possibility that myrmecochorous systems in the Australian arid zone may be characterized by longer dispersal distances than those in other parts of the world. Long‐distance seed movement by ants lends credence to the hypothesis that distance dispersal (in contrast to directed dispersal) could be of benefit to myrmecochorous plants.     

Effect of an exotic Acacia (Fabaceae) on ant assemblages in South African fynbos

Ant assemblages in South African fynbos invaded by Acacia saligna were compared with ant assemblages in undisturbed fynbos to determine whether ant assemblages change under exotic plants that produce ant‐dispersed seeds. Overall, no differences in the species richness of ants were found between weed‐infested and native sites but there were differences in both ant abundance and the composition of the ant assemblage. Ants were much less abundant in weed‐infested sites. To investigate whether changes in ant assemblages in weed‐infested areas could be due to a preference for native seeds over exotic seeds, seeds of a range of species were offered to ants and ants that handled seeds were identified. Thirteen species of ants handled A. saligna seeds and there was no evidence to suggest that the ant assemblage as a whole preferred native seeds to A. saligna seeds. Hypotheses that may account for this pattern are discussed.     

The production, storage and viability of seeds of Acacia karroo and A. nilotica in a grassy savanna in KwaZulu-Natal, South Africa

African Acacias are often major contributors to the progressive increase in the woody component of savannas, a phenomenon commonly referred to as bush encroachment. They produce large quantities of seed and may have large soil‐stored seed banks. In Hluhluwe–Umfolozi Park, the number of adult Acacia nilotica trees per hectare far exceed that of A. karroo adults. The relative dominance is reversed in the juvenile stage with A. karroo outnumbering A. nilotica threefold outside closed woodlands. Acacia karroo trees were smaller than A. nilotica trees on average, but produced more seeds for a given basal diameter size class. Acacia karroo showed less bruchid infestation than A. nilotica at all stages of pod development. Unlike A. nilotica, a proportion of A. karroo seeds was able to germinate after bruchid attack. We detected no difference between the two species in the soil‐stored seed bank or in the viability of seeds found in the seed bank.     

Intensity of pre‐dispersal seed predation in the invasive legume Leucaena leucocephala is limited by the duration of pod retention

Abstract The intensity of seed predation the invasive tropical legume Leucaena leucocephala by the bruchid Acanthoscelides macropthalmus was investigated in south‐eastern Queensland, Australia. The number of seeds damaged by A. macropthalmus as a proportion of total seeds available was found to increase the longer the pods remained on the tree. Seed predation ranged from a mean of 10.75% of seeds on pods that remained on the plant for 1 month and increased to 53.54% for pods that remained of the plant for 4 months. The low bruchid populations at high pod densities results in ‘predator satiation’. However, pods dehisce over time and the proportion of pods available over time to the bruchid correspondingly declines. By the time bruchid densities build up, most pods have dehisced and the seeds consequently escape predation. As a result the number of seeds lost to bruchid damage increases only marginally over time. Despite the levels of seed predation observed over the course of the study, the number of seeds in the soil seedbank almost doubled over time increasing from 8.5 seeds m^?3 to 15.5 seeds m^?3 over a 4‐month period. Levels of seed predation and addition of seeds to the soil seedbank were not correlated. The taxonomic (subspecies) status and apparency of host plants as measured by plant and patch traits (average plant height, density of podding plants and patch size) did not influence levels of seed predation. Pre‐dispersal seed predation studies need to take into account the pod/seed retention behaviour of the plant. The ability of the bruchid to regulate the invasiveness of Leucaena through influencing its demography is likely to be diminished if the insect populations cannot increase rapidly enough to use the seeds before pod dehiscence.     

Production and Application of Syringomycin E as an Organic Fungicide Seed Protectant against Pythium Damping‐off

Syringomycin E (SRE) is a cyclic lipodepsinonapeptide with potent antifungal activity and is produced by certain strains of Pseudomonas syringae pv. syringae. In this study, its potential as an organic‐compatible agrofungicide and vegetable seed treatment against the soilborne pathogen Pythium ultimum var. ultimum was examined. A variant of P. syringae pv. syringae strain B301D with enhanced SRE‐producing capabilities was isolated and grown in a bioreactor with SRE yields averaging 50 mg/l in 40 h. SRE was extracted and purified through a large‐scale chromatography system using organic‐compatible processes and reagents. The minimum concentrations of the purified product required to inhibit 50 and 90% of P. ultimum oospore germination were determined as 31.3 and 250 μg/ml, respectively. Drench treatment of cucumber seeds in P. ultimum‐infested potting medium (500 oospores/g) with 50 μg/ml SRE or water with no SRE resulted in 90.2 ± 4.5% and 65.7 ± 4.6% germination rates, respectively. Seed coating with 0.03% (w/w) SRE allowed 65.7 ± 4.6% seedlings to germinate on naturally infested soil while 100.0 ± 0.0% of non‐coated seeds were unable to germinate due to Pythium infection. Organic‐compatible and scalably produced SRE is potentially a novel organic fungicide seed protectant.     

Seed removal in a tropical North American desert: an evaluation of pre‐ and post‐dispersal seed removal in Stenocereus stellatus

• To determine seed removal influence on seed populations, we need to quantify pre‐ and post‐dispersal seed removal. Several studies have quantified seed removal in temperate American deserts, but few studies have been performed in tropical deserts. These studies have only quantified pre‐ or post‐dispersal seed removal, thus underestimating the influence of seed removal. We evaluated pre‐ and post‐dispersal seed removal in the columnar cactus Stenocereus stellatus in a Mexican tropical desert.
• We performed selective exclosure experiments to estimate percentage of seeds removed by ants, birds and rodents during the pre‐ and post‐dispersal phases. We also conducted field samplings to estimate abundance of the most common seed removers.
• Birds (10–28%) removed a higher percentage of seeds than ants (2%) and rodents (1–4%) during pre‐dispersal seed removal. Melanerpes hypopolius was probably the main bird removing seeds from fruits. Ants (62–64%) removed a higher percentage of seeds than birds (34–38%) and rodents (16–30%) during post‐dispersal seed removal. Pogonomyrmex barbatus was probably the main ant removing seeds from soil.
• Birds and ants are the main pre‐ and post‐dispersal seed removers in S. stellatus, respectively. Further studies in other S. stellatus populations and plants with different life forms and fruit types will contribute to evaluate seed removal in tropical American deserts.