A field test of the directed deterrence hypothesis in two species of wild chili

The directed deterrence hypothesis posits that secondary metabolites in ripe fruit function to deter fruit consumption by vertebrates that do not disperse seeds, while not impacting consumption by those that do. We tested this hypothesis in two species of wild chilies (Capsicum spp.). Both produce fruits that contain capsaicinoids, the compounds responsible for the pungency of chilies. Previous work suggests seed-dispersing birds but not seed-destroying rodents consume chili fruits, presumably because rodents are deterred by capsaicin. However, fruit removal from chili plants by rodents and other mammals has not been previously explored. Because laboratory rodents can develop a preference for capsaicin, it is quite possible that wild rodents are natural consumers of chili fruits. We monitored the fate of 125 marked fruits of Capsicum chacoense and 291 fruits of Capsicum annuum. For both species, essentially all fruit removal occurred during the day, when rodents are inactive. Video monitoring revealed fruit removal only by birds, mostly by species known to disperse chili seeds in viable condition. Furthermore, these species are from taxonomic groups that tend to specialize on lipid-rich fruits. Both species of chili produce fruits that are unusually high in lipids (35% in C. chacoense, 24% in C. annuum). These results support the directed deterrence hypothesis and suggest that fruiting plants distinguish between seed predators and seed dispersers by producing fruits that repel the former and attract the latter.     

Phenology of fleshy fruits in a wet sclerophyll forest in southeastern Australia: are birds an important influence?

Summary The hypothesis that seasonality in the production of fleshy fruits in temperate regions is the result of selection by avian seed dispersal agents or avian seed predators was tested in a temperate wet sclerophyll forest in south-eastern Australia. I determined whether ten common fleshy-fruited species produced fruits when potential avian seed dispersers were most abundant or avian seed predators were least abundant. The season of fruit production was not correlated with avian disperser abundance nor with seasonal changes in avian seed predators. Peak fruiting occurred during autumn but fruit-eating birds were equally abundant from spring through to autumn. Avian seed predators (parrots) did not show any seasonal variation in abundance. If dispersers are influencing fruiting seasonality in wet sclerophyll forest, it is likely that changes in social behaviour and feeding patterns of dispersers during autumn, rather than increases in abundance, will be an important influence on fruiting patterns in wet sclerophyll forest. However, environmental and life history factors may also influence phenology.     

Signal convergence in fruits: a result of selection by frugivores?

The Dispersal Syndrome hypothesis remains contentious, stating that apparently nonrandom associations of fruit characteristics result from selection by seed dispersers. We examine a key assumption under this hypothesis, i.e. that fruit traits can be used as reliable signals by frugivores. We first test this assumption by looking at whether fruit colour allows birds and primates to distinguish between fruits commonly dispersed by birds or primates. Second, we test whether the colours of fruits dispersed by primates are more contrasting to primates than the colours of bird‐dispersed fruits, expected if fruit colour is an adaptation to facilitate the detection by seed dispersers. Third, we test whether fruit colour has converged in unrelated plant species dispersed by similar frugivores. We use vision models based on peak sensitivities of birds’ and primates’ cone cells. We base our analyses on the visual systems of two types of birds (violet and ultraviolet based) and three types of primates (trichromatic primates from the Old and the New Worlds, and a dichromatic New World monkey). Using a Discriminant Function Analysis, we find that all frugivore groups can reliably discriminate between bird‐ and primate‐dispersed fruits. Fruit colour can be a reliable signal to different seed dispersers. However, the colours of primate‐dispersed fruits are less contrasting to primates than those of bird‐dispersed fruits. Fruit colour convergence in unrelated plants is independent of phylogeny and can be better explained by disperser type, which supports the hypothesis that frugivores are important in fruit evolution. We discuss adaptive and nonadaptive hypotheses that can potentially explain the pattern we found.     

Frugivory and seed dispersal by vertebrates in the Oriental (Indomalayan) Region

Current knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non-marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger-seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.     

动物对花楸树种实的取食与传播

花楸树是我国东北林区重要的非木质资源树种,其种实既有自然散布方式,也有动物散布方式.本文通过对花楸树种实散布过程中动物活动特点的研究,探索动物取食和传播花楸树种实的规律及其对花楸树天然更新的影响.在2008和2009年花楸树果实成熟期,通过定期观察取食花楸树果实的鸟类及其取食方式,确定对花楸树果实有拜访行为的鸟类有8种,其中食果肉鸟类斑鸫、灰喜鹊和白背啄木鸟对花楸树种实有传播作用,它们对花楸树果实的拜访频率分别为54%、12%和7%,取食后第一落点集中于距离母树5～10 m之间（占68.2%）,其次为距离母树5 m以内（占27.3%）,距离母树10 m以外的比例很小（占4.5%）.果实在鸟类消化道内的滞留时间可达20 min,表明潜在传播距离会很长.人工摆放果实和种子试验表明,在不同生境地面摆放的果实6～7 d内全部消失,果实的取食者主要是啮齿类和地面取食的鸟类,取食率均较高（50%～70%）;种子的取食者为啮齿类、地面取食的鸟类和蚁类,取食率均较低（1%～5%）.花楸树为多种动物提供食物,而动物为花楸树传播种子,动物的取食对花楸树的天然更新有重要影响.     

Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community

Summary Interactions between a large community of vertebrate frugivore-granivores (including 7 species of large canopy birds, 19 species of rodents, 7 species of ruminants, and 6 species of monkeys), and 122 fruit species they consume, were studied for a year in a tropical rainforest in Gabon.The results show how morphological characters of fruits are involved in the choice and partitioning of the available fruit spectrum among consumer taxa. Despite an outstanding lack of specificity between fruit and consumer species, consideration of simple morphological traits of fruits reveals broad character syndromes associated with different consumer taxa. Competition between distantly related taxa that feed at the same height is far more important than has been previously supposed. The results also suggest how fruit characters could have evolved under consumer pressure as a result of consumer roles as dispersers or seed predators. Our analyses of dispersal syndromes show that fruit species partitioning occurs more between mammal taxa than between mammals and birds. There is thus a bird-monkey syndrome and a ruminant-rodent-elephant syndrome. The bird-monkey syndrome includes fruit species on which there is no pre-dispersal seed predation. These fruits (berries and drupes) are brightly colored, have a succulent pulp or arillate seeds, and no protective seed cover. The ruminant-rodent-elephant syndrome includes species for which there is pre-dispersal predation. These fruits (all drupes) are large, dull-colored, and have a dry fibrous flesh and well-protected seeds.     

Within Flood Season Variation in Fruit Consumption and Seed Dispersal by Two Characin Fishes of the Amazon

Many Amazon River fishes consume fruits and seeds from floodplain forests during the annual flood season, potentially serving as important seed dispersers and predators. Using a participatory approach, this study investigated how within-season variation in flood level relates to fruit consumption and seed dispersal by two important frugivorous fish, Colossoma macropomum and Piaractus brachypomus , in two Lower Amazon River fishing communities in Brazil. Diets of both fish species were comprised of 78–98 percent fruits, largely dominated by a few species. Diets included fruits of 27 woody angiosperms and four herbaceous species from 26 families, indicating the importance of forest and Montrichardia arborescens habitat during peak flood. A correspondence between peak fruit species richness and peak flood level was observed in one of two communities, which may reflect higher forest diversity and/or differences in selection of fishing habitat. Both fishes are seed dispersers and predators, the relative role of which did not vary by flood level, seed size, or fish size, but may vary with seed hardness. Interspecific differences in diet volume and intact seeds suggest P. brachypomus are more effective seed dispersers than C. macropomum . Overall, the spatial and temporal variation in fruit species composition and richness demonstrate plasticity in fruit consumption in relation to flood level and locally available fruits. While such diets are adaptive to the dynamic changes of Amazon floodplain habitats, the high consumption of forest fruits and seeds from mid- and late-successional species suggests that floodplain forest degradation could disrupt seed dispersal and threaten local and regional fisheries.     

Fragmentation, habitat composition and the dispersal/predation balance in interactions between the Mediterranean myrtle and avian frugivores

Human‐induced fragmentation and disturbance of natural habitats can shift abundance and composition of frugivore assemblages, which may alter patterns of frugivory and seed dispersal. However, despite their relevance to the functioning of ecosystems, plant‐frugivore interactions in fragmented areas have been to date poorly studied. I investigated spatial variation of avian frugivore assemblages and fruit removal by dispersers and predators from Mediterranean myrtle shrubs (Myrtus communis) in relation to the degree of fragmentation and habitat features of nine woodland patches (72 plants). The study was conducted within the chronically fragmented landscape of the Guadalquivir Valley (SW Spain), characterized by ~1% of woodland cover. Results showed that the abundance and composition of the disperser guild was not affected by fragmentation, habitat features or geographical location. However, individual species and groups of resident/migrant birds responded differently: whereas resident dispersers were more abundant in large patches, wintering dispersers were more abundant in fruit‐rich patches. Predator abundances were similar between patches, although the guild composition shifted with fragmentation. The proportion of myrtle fruits consumed by dispersers and predators varied greatly between patches, but did not depend on bird abundances. The geographical location of patches determined the presence or absence of interactions between myrtles and seed predators (six predated and three non‐predated patches), a fact that greatly influenced fruit dispersal success. Moreover, predation rates were lower (and dispersal rates higher) in large patches with fruit‐poor heterospecific environments (i.e. dominated by myrtle). Predator satiation and a higher preference for heterospecific fruits by dispersers may explain these patterns. These results show that 1) the frugivore assemblage in warm Mediterranean lowlands is mostly composed of fragmentation‐tolerant species that respond differently to landscape changes; and 2) that the feeding behaviour of both dispersers and predators influenced by local fruit availability may be of great importance for interpreting patterns of frugivory throughout the study area.     

黄檗的更新特点及食果实鸟类对其种子的传播

在帽儿山实验林场和哈尔滨实验林场 ,黄檗母树下没有幼苗分布 ,不能进行天然更新 ,需要靠食果实鸟类等将果实和种子传播至远离母树的其他林下。捕食黄檗果实的食果实鸟类有 9种。其中 6种是食果肉鸟类 ,吞入果实后 ,消化果肉 ,而种子完整地随粪便排出而得以传播。其余 3种是食种子鸟类 ,没有传播作用。果实在鸟类消化道内的滞留时间达 2 0～ 30min ,具有很长的潜在传播距离。将鸟类消化后的种子与完整果实和人为去果肉种子进行萌发对比实验 ,消化后种子的累计萌发率与其余二者之间均没有显著性差异 ,说明食果实鸟类的消化 (道 )过程对种子萌发没有明显影响 ,同时证明果肉对种子萌发率没有显著影响 ,果肉中不含萌发抑制物质。黄檗提供多种鸟类以食物 ,而鸟类也同时以多种肉质果植物为食物。因此食果实鸟类和肉质果植物 (包括黄檗 )之间形成了松散的互利共生关系     

Evolutionary ecology of climacteric and non-climacteric fruits

Fleshy fruits can be divided between climacteric (CL, showing a typical rise in respiration and ethylene production with ripening after harvest) and non-climacteric (NC, showing no rise). However, despite the importance of the CL/NC traits in horticulture and the fruit industry, the evolutionary significance of the distinction remains untested. In this study, we tested the hypothesis that NC fruits, which ripen only on the plant, are adapted to tree dispersers (feeding in the tree), and CL fruits, which ripen after falling from the plant, are adapted to ground dispersers. A literature review of 276 reports of 80 edible fruits found a strong correlation between CL/NC traits and the type of seed disperser: fruits dispersed by tree dispersers are more likely to be NC, and those dispersed by ground dispersers are more likely to be CL. NC fruits are more likely to have red–black skin and smaller seeds (preferred by birds), and CL fruits to have green–brownish skin and larger seeds (preferred by large mammals). These results suggest that the CL/NC traits have an important but overlooked seed dispersal function, and CL fruits may have an adaptive advantage in reducing ineffective frugivory by tree dispersers by falling before ripening.     

Chemical tradeoffs in seed dispersal: defensive metabolites in fruits deter consumption by mutualist bats

Although fleshy fruits function primarily to attract seed dispersers, many animal‐dispersed fruits contain potentially toxic secondary metabolites. These metabolites can provide defense against seed predators and pathogens, but their effects on dispersers are still poorly understood. In some cases plants may experience a tradeoff, where the metabolites that provide fruit defense also reduce seed disperser preferences. In other cases the bioactivity of fruit secondary metabolites may be directed primarily at pests with no negative effects on seed‐dispersing vertebrates. We tested the effects of amides, a group of nitrogen‐based defensive compounds common in the plant genus Piper (Piperaceae), in interactions with the primary seed dispersers of Piper in the neotropics – fruit‐feeding bats in the genus Carollia (Phyllostomidae). In a series of flight cage experiments, pure amides and amide‐rich fruit extracts reduced the preferences of bats for Piper fruit, affecting both the bats’ initial choices to remove Piper infructescences and the proportion of fruit consumed from individual infructescences once they were removed. However, the effects of amides varied considerably among three species of Carollia and among the specific individual amides and extracts tested. Overall, our results support the hypothesis that plants experience a tradeoff between seed dispersal and fruit defense, but the strength of this tradeoff and the overall fitness consequences may depend strongly on ecological context.     

The impact of consumption of fruit by vertebrate and invertebrate frugivores on the germination success of an Australian rainforest seed

Abstract The consumption of fruits by vertebrates and invertebrates can be both advantageous or detrimental to the survival of the seeds they contain. This study investigated the effect of fruit size and consumption of fruit pulp by rodents and beetles on the germination of the seeds of Acmena graveolens, a tropical rainforest canopy tree found in northern Australia. As fruit size increased, germination success and the amount of pulp remaining on the fruits was greater. When beetles were absent, germination success was highest when most of the pulp was removed by rodents, suggesting that they removed an inhibitor of germination. When beetles were present, germination success did not differ significantly across pulp categories, so beetles apparently enhanced germination in seeds with little pulp initially removed, possibly by further removal of fruit pulp. In this study, both rodents and beetles enhanced germination success of A. graveolens seeds by consumption of fruit pulp. Acting as facilitators of germination is a relatively unusual role for both these frugivores that are generally considered to act as seed predators or (in the case of rodents) dispersers.     

Does attraction to frugivores or defense against pathogens shape fruit pulp composition?

Fruit traits evolve in response to an evolutionary triad between plants, seed dispersers, and antagonists that consume fruits but do not disperse seeds. The defense trade-off hypothesis predicts that the composition of nutrients and of secondary compounds in fruit pulp is shaped by a trade-off between defense against antagonists and attraction to seed dispersers. The removal rate model of this hypothesis predicts a negative relationship between nutrients and secondary compounds, whereas the toxin-titration model predicts a positive relationship. To test these alternative models, we evaluated whether the contents of nutrients and secondary compounds can be used to predict fruit removal by mutualists and pathogens in 14 bird-dispersed plants on a subtropical island in São Paulo state, southeastern Brazil. We selected eight to ten individuals of each species and prevented fruit removal by covering four branches with a net and left fruits on four other branches available to both, vertebrate fruit consumers and pathogens. The persistence of ripe fruits was drastically different among species for bagged and open fruits, and all fruit species persisted longer when protected against seed dispersers. We found that those fruits that are quickly removed by vertebrates are nutrient-rich, but although the attack rate of pathogens is also high, these fruits have low contents of quantitative defenses such as tannins and phenols. Thus, we suggest that the fruit removal rate by seed dispersers is the primary factor selecting the levels of fruit defense. Likewise, nutrient-poor fruits have low removal of seed dispersers and low probability of attack by pathogens. These species retain ripe fruits in an intact condition for a prolonged period because they are highly defended by secondary compounds, which reduce overall attractiveness. However, this strategy might be advantageous for plants that depend on rare or unreliable dispersers.     

Linking frugivores to the dynamics of a fruit color polymorphism

Although fruit color polymorphisms are a widespread phenomenon, the role of frugivores in their maintenance is unknown. Selection would require that frugivores interact differentially with fruit color morphs to alter their relative fitnesses, but such a pattern has yet to be demonstrated. In a 3-yr field study, the interactions of ants and birds with Acacia ligulata, an Australian shrub with a red/yellow/ orange aril color polymorphism, were examined. Bird species fell into three feeding guilds: seed dispersers, seed predators, and aril thieves; ant species acted either as seed dispersers or aril thieves. While there was no evidence of morph bias in ants, in some years birds fed more frequently on the yellow and orange morphs. Based on patterns of seedling survival and juvenile recruitment in seed deposition sites, bird seed dispersers increased the fitness of yellow and orange morphs (relative to red) in some populations, but decreased their relative fitness in others. Bird seed predators uniformly reduced relative fitness of yellow and orange morphs, while bird aril thieves had unknown effects. Altogether, consumer biases produced spatiotemporal variability in the relative fitness of A. ligulata color morphs, a pattern qualitatively consistent with maintenance of the polymorphism.     

Correlated evolution of fig size and color supports the dispersal syndromes hypothesis

The influence of seed dispersers on the evolution of fruit traits remains controversial, largely because most studies have failed to account for phylogeny and or have focused on conservative taxonomic levels. Under the hypothesis that fruit traits have evolved in response to different sets of selective pressures by disparate types of seed dispersers (the dispersal syndromes hypothesis), we test for two dispersal syndromes, defined as groups of fruit traits that appear together more often than expected by chance. (1) Bird syndrome fruits are brightly colored and small, because birds have acute color vision, and commonly swallow fruits whole. (2) Mammal syndrome fruits are dull-colored and larger on average than bird syndrome fruits, because mammals do not rely heavily on visual cues for finding fruits, and can eat fruits piecemeal. If, instead, phylogenetic inertia determines the co-occurrence of fruit size and color, we will observe that specific combinations of size and color evolved in a small number of ancestral species. We performed a comparative analysis of fruit traits for 64 species of Ficus (Moraceae), based on a phylogeny we constructed using nuclear ribosomal DNA. Using a concentrated changes test and assuming fruit color is an independent variable, we found that small-sized fruits evolve on branches with red and purple figs, as predicted by the dispersal syndromes hypothesis. When using diameter as the independent variable, results vary with the combination of algorithms used, which is discussed in detail. A likelihood ratio test confirms the pattern found with the concentrated changes test using color as the independent variable. These results support the dispersal syndromes hypothesis.     

Weak interactions between avian and insect frugivores: the case of Pistacia terebinthus L. (Anacardiaceae)

Vertebrate frugivores often feed on fruits upon or within which insects also feed, yet little information exists on the potential magnitude of interactions between these consumers. The Mediterranean shrub Pistacia terebinthus, the birds that consume its fruits, and the wasps that feed upon its seeds are examined in this study. P. terebinthus produces a highly variable fraction of final-sized red fruits that never become mature (green-colored). Red fruits can be immature, parthenocarpic, aborted, or attacked by wasps, and their pulp is much less nutritious than that of mature fruits. A total of 20 bird species consumed the fruits in the study area. Legitimate dispersers accounted for 39% of the total fruit removal, while pulp eaters and seed predators accounted for the remainder. Birds strongly preferred the mature fruits (only 4% of the fruits consumed were red). The incidence of wasps in the seeds ranged from 0 to 42% of the crop in 1989 and from 0 to 24% in 1990. The influence of avian and insect frugivore guilds on each other appears to be quite low because of the narrow overlap in resource utilization by birds and wasps, and an overall low intensity of wasp seed predation. From an evolutionary perspective, the possible ability of wasps to preclude fruit maturation appears not to be attributable to the present interaction with avian frugivores.     

Crop size is more important than neighborhood fruit availability for fruit removal of <Emphasis Type="Italic">Eugenia uniflora</Emphasis> (Myrtaceae) by bird seed dispersers

For a plant with bird-dispersed seeds, the effectiveness of seed dispersal can change with fruit availability at scales ranging from individual plants to neighborhoods, and the scale at which frugivory patterns emerge may be specific for frugivorous species differing in their life-history and behavior. The authors explore the influence of multispecies fruit availability at two local spatial scales on fruit consumption of Eugenia uniflora trees for two functional groups of birds. The authors related visitation and fruit removal by fruit gulpers and pulp mashers to crop size and conspecific and heterospecific fruit abundance to assess the potential roles that facilitative or competitive interactions play on seed dispersal. The same fruiting scenario influenced fruit gulpers (legitimate seed dispersers) and pulp mashers (inefficient dispersers) in different ways. Visits and fruit removal by legitimate seed dispersers were positively related to crop size and slightly related to conspecific, but not to heterospecific fruit neighborhoods. Visits and fruit consumption by pulp mashers was not related to crop size and decreased with heterospecific fruit availability in neighborhoods; however, this might not result in competition for dispersers. The weak evidence for facilitative or competitive processes suggest that interaction of E. uniflora with seed dispersers may depend primarily on crop size or other plant’s attributes susceptible to selection. The results give limited support to the hypothesis that spatial patterns of fruit availability influence fruit consumption by birds, and highlight the importance of considering separately legitimate and inefficient dispersers to explain the mechanisms that lie behind spatial patterns of seed dispersal.     

Impact of habitat structure and fruit abundance on avian seed dispersal and fruit predation

So far, it is poorly understood how differential responses of avian seed dispersers and fruit predators to changes in habitat structure and fruit abundance along land-use gradients may translate into consequences for the seed dispersal of associated plants. We selected a gradient of habitat modification (forest, semi-natural, and rural habitat) characterized by decreasing tree cover and a high variation in local fruit availability. Along this gradient we quantified fruit removal by avian seed dispersers and fruit predators from 18 Sorbus aucuparia trees. We analyzed the relative importance of tree cover and fruit abundance in explaining species richness, abundance and fruit removal rates of both guilds from S. aucuparia trees. Species richness and abundance of seed dispersers decreased with decreasing tree cover, whereas fruit removal by seed dispersers decreased with decreasing fruit abundance independent of tree cover. Both variables had no effect on species richness, abundance and fruit removal by fruit predators. Consequently, seed dispersers dominated relative fruit removal in fruit-rich sites but the dispersal/predation ratio shifted in favor of predation in fruit-poor habitat patches. Our study demonstrates that variation in local habitat structure and fruit abundance can cause guild-specific responses. Such responses may result in a shift in fruit removal regimes and might affect the dispersal ability of dependent fruiting plants. Future studies should aim at possible consequences for plant recruitment and guild-specific responses of frugivores to disturbance gradients on the level of entire plant–frugivore associations.     

The Role of Arboreal Seed Dispersal Groups on the Seed Rain of a Lowland Tropical Forest1

Most tropical plants produce fleshy fruits that are dispersed primarily by vertebrate frugivores. Behavioral disparities among vertebrate seed dispersers could influence patterns of seed distribution and thus forest structure. This study investigated the relative importance of arboreal seed dispersers and seed predators on the initial stage of forest organization–seed deposition. We asked the following questions: (1) To what degree do arboreal seed dispersers influence the species richness and abundance of the seed rain? and (2) Based on the plant species and strata of the forest for which they provide dispersal services, do arboreal seed dispersers represent similar or distinct functional groups? To answer these questions, seed rain was sampled for 12 months in the Dja Reserve, Cameroon. Seed traps representing five percent of the crown area were erected below the canopies of 90 trees belonging to nine focal tree species: 3 dispersed by monkeys, 3 dispersed by large frugivorous birds, and 3 wind‐dispersed species. Seeds disseminated by arboreal seed dispersers accounted for ca 12 percent of the seeds and 68 percent of the seed species identified in seed traps. Monkeys dispersed more than twice the number of seed species than large frugivorous birds, but birds dispersed more individual seeds. We identified two distinct functional dispersal groups, one composed of large frugivorous birds and one composed of monkeys, drop dispersers, and seed predators. These groups dispersed plants found in different canopy strata and exhibited low overlap in the seed species they disseminated. We conclude it is unlikely that seed dispersal services provided by monkeys could be compensated for by frugivorous birds in the event of their extirpation from Afrotropical forests.     

Seed dispersal: the blind bomb maker

A recent study shows that a desert shrub uses a 'mustard oil bomb' to regulate the behaviour of seed-predating rodents - transforming these predators into mutualistic seed dispersers.