Myrmecochorous Plants Research Articles

Native ants vary in their use of seeds from a recently introduced myrmecochorous exotic plant

AbstractMyrmecochory is a common mutualism between ants and plants benefiting both partners: ants obtain a nutrient-rich food source, while plants enjoy a host of benefits ranging from enhanced dispersal to protected germination sites. However, this mutualism can be exploited by invasive myrmecochores, where native ants spread invasive plant seeds, possibly to the detriment of native plant assemblages. With the recent introduction of a potentially invasive myrmecochorous plant (Thesium ramosum) in Alberta, Canada, we tested ant interest in T. ramosum. To evaluate both general interest in T. ramosum as a food source, and preference for T. ramosum over other food sources, we collected colonies of four commonly occurring native Formica species and conducted seed removal trials and food preference trials. We then evaluated interest in and preference for T. ramosum seeds through assessing mean rate of seed removal and food item removal, total number of seeds and food items removed, and trends in seed and food item removal through time. We found that while all ant species tested showed interest in T. ramosum, interest level varied among species, and additional factors such as colony size and presence of host species in socially parasitic species influenced interest in T. ramosum. Considering native ant interest in T. ramosum as a food source, it seems plausible that Formica species may act as a dispersal vector for T. ramosum, potentially enhancing its invasiveness.

Ant handling changes myrmecochore seed coat microbiomes and alters diversity of seed‐borne plant pathogenic fungi

Abstract The putative benefits to seeds in myrmecochory (ant‐mediated seed dispersal) are often cast in a reward context. However, microbes have been mostly overlooked as seed mortality agents in myrmecochory, as have potential treatments provided by ant‐handling. We investigated the effects of ant handling on the diversity of seed coat fungal communities of three myrmecochorous plant species. Ant‐handling altered measures of both alpha and beta diversity of fungal communities. Ant‐handled seeds harboured different overall fungal communities and plant pathogen communities than non‐ant‐handled seeds. The myrmecochore pathogenic fungal community showed high dissimilarity (high pairwise community turnover) between ant‐handled and control seeds, while beta diversity measures for ant‐handled seeds and seeds with manually removed elaiosomes were less dissimilar. Ant handling may offer an additional benefit to myrmecochorous seeds via the reduction in the seed coat pathogenic community, which may be driven by elaiosome removal or as a by‐product of ant cleaning behaviours and chemical secretions. Read the free Plain Language Summary for this article on the Journal blog.

Linking pollen limitation and seed dispersal effectiveness.

Seed production and dispersal are crucial ecological processes impacting plant demography, species distributions and community assembly. Plant-animal interactions commonly mediate both seed production and seed dispersal, but current research often examines pollination and seed dispersal separately, which hinders our understanding of how pollination services affect downstream dispersal services. To fill this gap, we propose a conceptual framework exploring how pollen limitation can impact the effectiveness of seed dispersal for endozoochorous and myrmecochorous plant species. We summarize the quantitative and qualitative effects of pollen limitation on plant reproduction and use Optimal Foraging Theory to predict its impact on the foraging behaviour of seed dispersers. In doing so, we offer a new framework that poses numerous hypotheses and empirical tests to investigate links between pollen limitation and seed dispersal effectiveness and, consequently, post-dispersal ecological processes occurring at different levels of biological organization. Finally, considering the importance of pollination and seed dispersal outcomes to plant eco-evolutionary dynamics, we discussed the implications of our framework for future studies exploring the demographic and evolutionary impacts of pollen limitation for animal-dispersed plants.

Evaluation of seed-dispersal services by ants at a temperate pasture: Results of direct observations in an ant suppression experiment.

Ants disperse seeds of many plant species adapted to myrmecochory. While advantages of this ant-plant mutualism for myrmecochorous plants (myrmecochores) have been previously studied in temperate region mostly in forests, our study system was a pasture. Moreover, we used a unique combination of observing the effect of ant-activity suppression on ant dispersal and comparison of the contribution of ant and unassisted dispersal to the distance from mother plant. We established plots without and with ant-activity suppression (enclosures). We offered diaspores of a myrmecochorous (Knautia arvensis), and a non-myrmecochorous (Plantago lanceolata) species in a choice test and followed ants carrying diaspores during days and nights (focus of previous studies was on diurnal dispersal). We measured frequency and distances of ant dispersal and compared them with unassisted dispersal recorded using sticky trap method. The dispersal frequency was lower in enclosures (3.16 times). Ants strongly preferred diaspores of the myrmecochore to non-myrmecochore with 586 and 42 dispersal events, respectively (out of 6400 diaspores of each species offered). Ant dispersal resulted in more even and on average longer distances (maximum almost tenfold longer, 994 cm) in comparison to unassisted dispersal. Ant dispersal altered the distribution of distances of the myrmecochore from roughly symmetric for unassisted dispersal to positively skewed. Ants dispersed heavier diaspores farther. Ants dropped the majority of diaspores during the dispersal (which reduces clustering of seeds), while several (11%) were carried into anthills. Anthills are disturbed microsites presumably favorable for germination in competitive habitats. Ants provided non-negligible dispersal services to myrmecochorous K. arvensis but also, to a lesser extent, of non-myrmecochorous P. lanceolata.

Persistent effects of land-use history on myrmecochorous plant and epigeic ant assemblages across an ecoregional gradient in New York State

Persistent effects of land-use history on myrmecochorous plant and epigeic ant assemblages across an ecoregional gradient in New York State

What are elaiosomes for? Effects of elaiosomes on ant attraction, seed removal and germination in wild chaya (Cnidoscolusaconitifolius)

Seed dispersal by ants is common in arid lands. The seeds of myrmecochorous plants bears an elaiosome, an appendage that acts as a reward for ants. Once an ant identifies an elaiosome-bearing seed, it carries the diaspore to the nest, removes the elaiosome and discards the seed. During elaiosome removal, ants also scarify the seed, which may favor seed germination or facilitate pathogen attack. Some elaiosomes are hygroscopic and therefore, this could increase water intake and retention. We assessed the effect of elaiosome removal, seed scarification and fungal infection on germination in Cnidoscolus aconitifolius, a plant species common in the arid tropics of the Americas. The effects of elaiosome removal on ant attraction and seed removal were also assessed. According to the results, the elaiosome of C. aconitifolius increases the attractiveness of its seeds to ants, but did not affect seed removal or seed germination. Also, the elaiosome significantly increased the chance of pathogen attack on the seed. The benefits of elaiosome removal on seed germination were mediated by physical scarification, with greater germination in scarified seeds without elaiosomes. Seed scarification did not affect the likelihood of fungal attack.

Are seed-dispersing ants elaiosome-limited? An experimental test in a Connecticut forest dominated by myrmecochorous plants

Food-for-dispersal mutualisms are critical sources of energy flow in ecological networks. By providing a nutrient-rich reward in the form of a fruit or seed to an animal mutualist, plants gain directed dispersal. Myrmecochory is one form of animal-mediated seed dispersal in which ants are recruited to plant seeds by providing a nutrient rich appendage called an elaiosome. It is unclear to what impact nutrients provided by elaiosomes have on ants, and whether the mutualism can tolerate disruptions to this food source. In the Northeastern U.S. mixed deciduous forest ecoregion, a diverse assemblage of herbaceous plants are dispersed by Aphaenogaster ants. Since Aphaenogaster ants gain a significant nutrient subsidy from this mutualism, it is predicted that loss of these seeds could cause reductions in their population size. To test this hypothesis, I performed a long-term removal of elaiosome food sources for ants. All seeds were removed by hand from three 50m2 plots, each paired with control plots with no removal, and a supplementation plot from April to May, from 2010 to 2012. Five years following removal treatments, I collected data on coverage of ant-dispersed plants and the abundance of seed-dispersing Aphaenogaster ants. Removal of all sources of elaiosomes resulted in modest reductions in the proportional coverage of ant-dispersed plants relative to control plots. Ant forager abundance was not impacted by the treatments five years after the removal of elaiosomes. In sum, Aphaenogaster populations may not always be limited by the availability of elaiosomes or myrmecochorous plants produce can recover quickly (<5 years) to provide enough food for these ants. As long as surrounding populations of understory forest plants are maintained, it appears that both mutualistic ants may rebound from a short-term reduction in the production of elaiosomes.

Myrmecochorous plants and their ant seed dispersers through successional stages in temperate cove forests

Anthropogenic disturbance can decrease woodland diversity in the species-rich herbaceous layer of eastern deciduous forests, and ant-dispersed (myrmecochorous) plants may be particularly affected due to their limited ability to re-colonise secondary forests. Consequently, we predicted that myrmecochorous plants and their keystone seed-dispersing ants would increase with time since the last disturbance, as reflected by young, middle or mature forest successional stage. Specifically, we hypothesized that myrmecochore abundance and richness would be relatively lowest in the youngest forests, moderate in middle-aged forests and highest in mature forests. We also hypothesized that experimentally introducing ant bait in a regular pattern, as might be expected from intact species-rich myrmecochore communities, would elicit greater ant foraging interest than intermittent baiting, as might be expected in recently disturbed depauperate myrmecochore communities. We found the highest myrmecochore plant abundance in mature forests, but we found the same for herbaceous plants overall. Moreover, regular and intermittent bait offerings elicited similar overall ant responses. The observational results suggested that myrmecochorous plants respond to forest successional stage as do other woodland plants, and our experimental results suggest that disrupted seed delivery by myrmecochores did not affect Aphaenogaster abundance or foraging behaviour. As such, the myrmecochore communities studied here appeared as resilient as other woodland herbs, and seed-dispersing ants did not appear dependent on myrmecochore plant communities. Indeed, given the relatively high myrmecochore richness and abundance across our study sites, forest type (e.g., rich cove forest) might better predict myrmecochore success than successional stage.

Seed Dispersal by Ants in Three Early-Flowering Plants.

Simple SummaryMyrmecochory is seed dispersal of numerous plant species mediated by ants. We investigate ant–plant interactions under field conditions across two study sites in Central Europe. Three obligatory myrmecocohrous plants are chosen for the experiments: snowdrop Galanthus nivalis, hollow root Corydalis cava and European wild ginger Asarum europaeum. We experimentally alter diaspore morphology and record seed removal rates across five treatments: elaiosomes without seeds, diaspore without elaiosome, 1/2 elaiosome + diaspore, 1/2 diaspore + elaiosome and control. Elaiosomes of European wild ginger constitute about 30% of diaspore weight, elaiosomes of snowdrop constitute 13% and elaiosomes of hollow root constitute only 7.5%. Diaspore/elaiosome removal rates are highest in European wild ginger (34%), followed by hollow root (26%) and snowdrop (10%). Only two ants interact with diaspores, the acorn ant Temnothorax crassispinus and the red ant Myrmica ruginodis. Ants respond to elaiosome/seed ratio by removing elaiosomes without diaspores most frequently, followed by 1/2 diaspore + elaiosome, control, diaspores without elaiosomes and 1/2 elaiosome with diaspore. Plants do not effectively manipulate ant behavior and no dispersal benefits from interactions with ants are observed.Interactions between ants and plants vary from being occasionally beneficial to neutral and negative. Ant-mediated dispersal of obligatory myrmecochorous plants is considered mutualistic interaction, providing benefits to plants in terms of seed dispersal. Ants are rewarded by providing elaiosome, sugar, lipid and protein-rich appendages attached to seeds (diaspores). We experimentally examine rates of diaspore removal rates among three species of plants (snowdrop Galanthus nivalis, hollow root Corydalis cava and European wild ginger Asarum europaeum) under field conditions in two study sites in Central Europe. Diaspore morphology is altered by manipulating both elaiosome and seed size. The small-sized acorn ant Temnothorax crassispinus interacts with the snowdrop and hollow root and the moderately-sized red ant Myrmica ruginodis interacts with European wild ginger. Experimental manipulation with elaiosomes yields largely non-significant results. Diaspore removal rates are generally low (snowdrop 10%, hollow root 26%, European wild ginger 34%) probably due to the small size of ants relative to heavy diaspores. Many ants are observed to consume elaiosomes in situ (cheating). We conclude that ant–plant relationships in this case are not mutualistic but rather neutral/slightly negative, because the plants do not obtain any apparent benefits from their interactions with ants.

Seed removal decrease by invasive Argentine ants in a high Nature Value farmland

Seed dispersal by ants is an important ecological process that maintains the structure anddiversity of natural communities, however, it is vulnerable to biological invasions. Argentine ants are one of the worst invasive ant species and cause severe changes in ecosystem processes and native ant biodiversity declines in invaded sites. Here, we studied seed removal by ants combining observations and a cafeteria experiment with seeds of four myrmecochorous plant species (Centaurea sphaerocephala, Rosmarinus officinalis, Silybum marianum, and Ulex australis) in two sites (invaded and uninvaded) located in the Mediterranean Montado ecosystem and classified as High Nature Value farmland (HNV). Significant differences in daily seed removal rates were found between the two study sites. In uninvaded sites, several native ant species were attracted to the seeds, resulting in all seeds being removed rapidly. The majority of seed removal events were carried out by two key seed disperses Pheidole pallidula (71%) and Aphaenogaster iberica (26%) with a clear preference for diaspored with larger and heavier elaiosome (i.e., C. sphaerocephala, S. marianum). By contrast, while the Argentine ant showed some interest (68% of seeds were interacted with), no seed removal events were observed. The extirpation of the local ant fauna by the Argentine ant and its inability to ensure seed dispersal services may lead to the interference and eventually to the collapse of seed dispersal of the four studied myrmecochorous plants in the invaded site in the future. We argue that these discrete but severe consequences of an invasive species on a key ecological process may strongly affect the functioning of the Montado ecosystem.

Seed germination of a myrmecochorous plant endemic to the Brazilian semiarid region: the wolf is not so bad

Studies about seed dispersal and germination are important to understand patterns of plant distribution and abundance, and help establish strategies for environmental conservation. We evaluated the role of two different dispersers, the ant Atta laevigata and the maned wolf Chrysocyon brachyurus, in the germination of Copaifera arenicola seeds, a characteristically myrmecochorous plant species. Germination was evaluated for seeds subjected to four treatments: (1) seeds manipulated by the ant, (2) seeds ingested by the maned wolf, (3) seeds that had the elaiosome removed manually, and (4) seeds with elaiosome (unmanipulated seeds). Seeds manipulated by the ant and seeds that had the elaiosome removed manually required less time to germinate and had higher germination percentages (98.6% and 95.8%, respectively) than the other treatments. However, seeds ingested by the maned wolf also had a high germination percentage (87.7%), above that of unmanipulated seeds (34.7%). Probably, elaiosomes of unmanipulated seeds and small remnants of this structure that resist digestion by maned wolf can decrease to some extent seed germination. We argue that dispersal of C. arenicola seeds by the ant and by the maned wolf result in different patterns of seed distribution in the environment and that they have complementary roles in structuring plant populations.

Testing the effects of ecologically extinct mammals on vegetation in arid Australia: A long‐term experimental approach

AbstractThe loss of species from ecosystems can have cascading impacts on species interactions and ecosystem function. Australia has experienced the greatest loss of mammals globally in the past 200 years, but we know little of how the loss of this suite of ecosystem engineers and herbivores has affected vegetation. We used a threatened mammal reintroduction sanctuary to investigate effects of ecologically extinct mammals on plant assemblages. First, we tested the net effects of mammals using a long‐term exclusion experiment within the sanctuary. Second, we used a three‐year disturbance experiment to determine the relative roles of herbivory and physical disturbance in driving changes in plant assemblages. Third, we compared outcomes inside and outside the sanctuary to determine how effects of reintroduced mammals differed from contemporary mammal assemblages. Plant species richness was greatest in mammal exclusion plots and declined across all treatments from 2011 to 2018, probably due to drought. Plant composition changed in response to mammal exclusion, with six species increasing significantly, shrubs and myrmecochorous plants becoming more common and large‐seeded species less common. Responses to experimental disturbance were less clear. Grass and resprouters were more common, and palatable and large‐seeded plants were less common outside the sanctuary (exposed to contemporary mammal assemblage). Our study shows that reintroductions of ecologically extinct mammals have substantial impacts on plant assemblages, both through ecosystem engineering and herbivory, and these impacts differ from those of contemporary mammal faunas, suggesting that pre‐European Australian ecosystems were markedly different from contemporary ecosystems.

Odor of achlorophyllous plants' seeds drives seed-dispersing ants.

Seed dispersal by ants is an important means of migration for plants. Many myrmecochorous plants have specialized appendages in their seeds called elaiosome, which provides nutritional rewards for ants, and enable effective seed dispersal. However, some nonmyrmecochorous seeds without elaiosomes are also dispersed by ant species, suggesting the additional mechanisms other than elaiosomes for seed dispersal by ants. The seeds of the achlorophyllous and myco‐heterotrophic herbaceous plant Monotropastrum humile are very small without elaiosomes; we investigated whether odor of the seeds could mediate seed dispersal by ants. We performed a bioassay using seeds of M. humile and the ant Nylanderia flavipes to demonstrate ant‐mediated seed dispersal. We also analyzed the volatile odors emitted from M. humile seeds and conducted bioassays using dummy seeds coated with seed volatiles. Although elaiosomes were absent from the M. humile seeds, the ants carried the seeds to their nests. They also carried the dummy seeds coated with the seed volatile mixture to the nest and left some dummy seeds inside the nest and discarded the rest of the dummy seeds outside the nest with a bias toward specific locations, which might be conducive to germination. We concluded that, in M. humile seeds, volatile odor mixtures were sufficient to induce seed‐carrying behavior by the ants even without elaiosomes.

Do dispersers shape diaspore mass in vespicochory?

Vespicochory, defined as seed dispersal by wasps, was first reported by Pellmyr (1985). To date, vespicochory has only been documented in nine plant species belonging to five plant families, themselves dispersed by five wasp genera (Burge and Beck 2019; Chen et al. 2020). All known wasp-dispersed plants bear seeds with lipid-rich elaiosomes that are also thought to attract ants to disperse their seeds (myrmecochory) (Lengyel et al. 2010). A recent study revealed that Stemona tuberosa produces hydrocarbons that smell like prey to attract dispersing wasps (Chen et al. 2018). The data to date suggests that vespicochory evolved from myrmecochory and change in chemical cues are likely for the evolution of vespicochory. Wasps often transport diaspores (seed and elaiosome) from foraging plants to their nests, and consume lipid-rich elaiosomes but not seeds, representing an effective seed dispersal service, significantly longer distance dispersal, compared to dispersal by ants (Chen et al. 2017; Fig. 1). Since over 11,000 plant species produce diaspores with lipid-rich elaiosomes dispersed by ants (Lengyel et al. 2010), the potential for vespicochory might be significantly underestimated (Chen et al. 2020). Relying on wasps could be a strategy to increase seed dispersal occurrence and distance in myrmecochorous plants.

How common and dispersal limited are ant-dispersed plants in eastern deciduous forests?

Most plant diversity in eastern deciduous forests occurs in the understory herbaceous layer. Ant-dispersed plants (myrmecochores) reside within that layer, and they often are reported to be a substantial part of understory plant abundance and diversity that is particularly threatened by global change because of their relatively short dispersal distances. Indeed, they are often, but not always, reported to be lacking or absent from young forests where they may fail to re-colonize after extirpation due to their dispersal limitations. Our objective was to characterize the woodland myrmecochorous plant communities across the northern- and southernmost reaches of eastern deciduous forests using vegetation from 2687 plots in 44 U.S. National Parks. We asked whether (a) myrmecochorous plants are a substantial portion of understory herbaceous communities in eastern North American deciduous forests, and (b) if they are particularly dispersal limited relative to other understory herbaceous dispersal guilds. If myrmecochores are notable in abundance and extent in understory herbaceous communities, we expected that they would comprise ~ 30% of the species and ~ 55–60% of the abundance, as reported in the literature. If myrmecochores, as a guild, are more dispersal limited than other dispersal modes (anemochory, autochory, zoochory), we also expected that myrmecochore species richness would be more limited by park age and area than other dispersal guilds because they would take longer to re-colonize. In contrast with the published literature on myrmecochores, our data suggest that myrmecochorous plants are much less common as reported in eastern deciduous understory herbaceous communities (~ 9% of herbaceous species; ~ 12% of herbaceous abundance), but twice as common as the global percentage of myrmecochorous plants (~ 4.5%). We also found that they are not particularly impacted by forest size and fragmentation. Ants appear to disperse myrmecochorous seeds at 1/20th the distance of wind-dispersed plants, but the dispersal distances for myrmecochores are about the same as other animal-dispersed plants and slightly less than gravity-dispersed plants in these same forests. Moreover, our data also suggest that myrmecochores, particularly large-seeded myrmecochores, may not occur in enough abundance to contribute meaningful biomass toward ant diets. Of course, species abundance does not equal species importance, and many keystone species impact ecosystems more than their abundance might suggest. Ant-mediated seed dispersal is a model system for understanding ecological and evolutionary dynamics, and certainly contributes toward understanding the threats of fragmentation and climate change in eastern deciduous forest systems, but they may not be as abundance or threatened as previously reported.

Switching roles from antagonist to mutualist: a harvester ant as a key seed disperser of a myrmecochorous plant

1. Harvester ants are major seed predators in arid environments. However, given that many harvester ants are partly omnivorous and therefore potentially attracted to the elaiosomes of myrmecochorous seeds, it is unclear if these ants act as predators or dispersers when removing myrmecochorous seeds.2. We describe the outcomes of interactions between the harvester ant,Pogonomyrmex naegelii, and myrmecochorous plant,Microstachys serrulata, in a Brazilian savanna. We: (i) evaluated the role of elaiosome in seed removal byP. naegelii; (ii) investigated the fate and viability of removed seeds; (iii) tested if soils associated withP. naegeliinests are nutrient‐enriched; (iv) compared seedling survival; and (v) the density of seedling and adultM. serrulatanearby toP. naegeliinests compared with those away from these nests (i.e. controls).3. Rates of removal ofM. serrulataseeds were two‐fold higher with elaiosomes than without. The ant attractant oleic acid was the dominant fatty acid in elaiosomes, but it was absent from seeds. Removed seeds are taken into nests, and Tetrazolium tests indicated that 95% of seeds remain viable. Soils associated withP. naegeliinests were not nutrient‐enriched, and seedling survival was similar nearby toP. naegeliinests compared with control areas. However, densities of both seedling and adultM. serrulatawere higher nearby toP. naegeliinests than in control areas.4. Our findings show thatP. naegeliiswitches its role from seed predator for most plant species to be the dominant seed disperser forM. serrulata, playing a key role in the distribution of adult plants.

Can Disruption of an Ant–Plant Mutualism Explain a Lack of Recovery of Forest Herbs in Post-Agricultural Forests of New York?

A substantial proportion New York's forests regenerated following agricultural abandonment around the turn of the 20th century. Many myrmecochorous (ant-dispersed) plant species are lacking in these forests decades after land abandonment despite being present in residual stands. To determine if disruption to this ant–plant mutualism can partially explain the current distribution patterns of myrmecochorous plants, we quantified the proportion of seeds removed by ants while accounting for predation by rodents in residual and post-agricultural forests. We experimentally manipulated ant access and controlled for rodent access to seeds of 3 myrmecochorous understory herbs in 3 paired residual and post-agricultural forests in central New York. We identified Aphaenogaster rudis as the primary seed disperser. We found no difference in mean (± 1 SE) proportion of seeds removed by ants between residual stands (73.7% ± 7.7%) and post-agricultural stands (75.8% ± 7.9%). Rodents removed few to no seeds (5.3% ± 1.5%), but an invasive slug, Arion subfuscus (Dusky Arion), was observed removing elaiosomes from seeds in both stand types. Our data indicated neither a lack of ant-dispersal activity nor excessive rodent predation would be limiting to dispersal of myrmecochorous seeds in post-agricultural forests during the period of our study. Given the presence of A. rudis in post-agricultural stands, programs to assist plant migration will likely be sufficient to reestablish this ant–plant mutualism in degraded sites.

Effects of seed morphology and elaiosome chemical composition on attractiveness of five Trillium species to seed-dispersing ants.

Morphological and chemical attributes of diaspores in myrmecochorous plants have been shown to affect seed dispersal by ants, but the relative importance of these attributes in determining seed attractiveness and dispersal success is poorly understood. We explored whether differences in diaspore morphology, elaiosome fatty acids, or elaiosome phytochemical profiles explain the differential attractiveness of five species in the genus Trillium to eastern North American forest ants. Species were ranked from least to most attractive based on empirically‐derived seed dispersal probabilities in our study system, and we compared diaspore traits to test our hypotheses that more attractive species will have larger diaspores, greater concentrations of elaiosome fatty acids, and distinct elaiosome phytochemistry compared to the less attractive species. Diaspore length, width, mass, and elaiosome length were significantly greater in the more attractive species. Using gas chromatography–mass spectrometry, we found significantly higher concentrations of oleic, linoleic, hexadecenoic, stearic, palmitoleic, and total fatty acids in elaiosomes of the more attractive species. Multivariate assessments revealed that elaiosome phytochemical profiles, identified through liquid chromatography–mass spectrometry, were more homogeneous for the more attractive species. Random forest classification models (RFCM) identified several elaiosome phytochemicals that differed significantly among species. Random forest regression models revealed that some of the compounds identified by RFCM, including methylhistidine (α‐amino acid) and d‐glucarate (carbohydrate), were positively related to seed dispersal probabilities, while others, including salicylate (salicylic acid) and citrulline (L‐α‐amino acid), were negatively related. These results supported our hypotheses that the more attractive species of Trillium—which are geographically widespread compared to their less attractive, endemic congeners—are characterized by larger diaspores, greater concentrations of fatty acids, and distinct elaiosome phytochemistry. Further advances in our understanding of seed dispersal effectiveness in myrmecochorous systems will benefit from a portrayal of dispersal unit chemical and physical traits, and their combined responses to selection pressures.

When the company does not matter: High‐quality ant seed‐disperser does not drive the spatial distribution of large‐seeded myrmecochorous plants

AbstractMutualisms are one of the main forces shaping species spatial patterns at all geographic scales. In generalised mutualisms, however, the dependence among partners is highly variable in time and space, and therefore, the effect of diffuse mutualisms on species geographic distributions is unclear. Myrmecochorous seeds in Brazilian semi‐arid vegetation are dispersed by several ant species. However, large‐seeded species are especially dependent on dispersal by the giant ant Dinoponera quadriceps, which is the main disperser of such diaspores and the species that provide the longest dispersal distance among ant species in this system. Hence, we hypothesise that the presence of D. quadriceps shapes the distribution of large‐seeded, but not the distribution of small‐seeded myrmecochorous plant species. To evaluate this hypothesis, we modelled the potential distribution of two large‐seeded (which are predominantly dispersed by D. quadriceps) and two small‐seeded (which are barely dispersed by D. quadriceps) Euphorbiaceae species and the potential distribution of D. quadriceps. We analysed the relationship between the occurrence suitability of D. quadriceps and the occurrence suitability of plant species. We found that the potential distribution of both large‐seeded and small‐seeded myrmecochorous plants was unrelated to D. quadriceps occurrence suitability. It means that the disproportional benefits provided by high‐quality disperser at local scales may not emerge at broader geographical scales. In Caatinga vegetation, diaspores are submitted to strong abiotic filters that constraint seed germination and establishment after the dispersal phase. Such abiotic filters may dilute the initial benefit provided by long‐distance dispersers. Therefore, we suggest that in dry environments like the Caatinga, the benefits of long‐distance removals should be outweighed by the risk of reach new habitats with unfavourable conditions for germination and establishment.

An Ant-Plant Mesocosm Experiment Reveals Dispersal Patterns of Myrmecochorous Plants

For Central European herbs, ants are one common dispersal vector acting at relatively small spatial scales. Though extensively studied concerning the different benefits to plants, specific dispersal patterns mediated by ants have been reportedly very sparsely and without any validation. Thus, we studied the seed dispersal pattern of a set of myrmecochorous plant species in a novel mesocosm experiment. We examined the seed dispersal distances of four forest herbs (Hollow Root–Corydalis cava (L.) Schweigg. &amp; Körte, Alpine Squill–Scilla bifolia L., and Common Dog-violet–Viola riviniana Rchb. and the annual Ivy-leaved Speedwell–Veronica hederifolia L.) by the red ant Myrmica ruginodis Nylander in 8.25 m² large plots under natural conditions with and without ants. In the presence of Myrmica ants, the bulb geophytes C. cava and S. bifolia showed a significantly higher fraction of dispersed seedlings and a maximum dispersal distance of 322 cm. Estimated by nearest neighbor analyses, distances between single C. cava seedlings were significantly higher in ant plots than in exclosures without ants. The annual species Veronica hederifolia showed a few dispersed seedlings in ant plots only, while the diplochorous hemicryptophyte Viola riviniana germinated in a widely scattered manner with distances up to 241 cm due to ballochorous dispersal in both ant and exclosure plots, but with a maximum of 324 cm only by means of ants. Our results indicate the escape from the mother plant and dispersal for distance as an important benefit for myrmecochorous species, potentially accompanied by benefits through reduced competition.