Differences in the fruit maturation stages at which oviposition occurs among insect seed predators feeding on the fruits of five dipterocarp tree species

The seeds of dipterocarp trees are the main food resources for many species of weevils, bark beetles and small moths; however, for most seed‐eating insects on dipterocarp tropical trees, seed utilization patterns remain poorly investigated. This study aimed to determine the fruit maturation stages at which eggs are laid by different insect seed predators feeding on the seeds or fruits of the following five dipterocarp species: Dipterocarpus globosus, Dryobalanops aromatica, Shorea beccariana, S. acuta and S. curtisii, which reproduced during the same period. We investigated the occurrence frequencies of the insect seed predators at various growth stages by collecting both unfallen and fallen fruit on several occasions during the period of seed/fruit maturation in a tropical rainforest in Borneo from September to December 2013. Weevils and bark beetles were the dominant insect seed predators of the five tree species. One or two weevil species of Alcidodes, Damnux and/or Nanophyes preyed on the seeds of each of the five tree species, and one bark beetle species, Coccotrypes gedeanus, preyed on the seeds of all five tree species. Many larvae, pupae and adults of each weevil species were found in pre‐dispersal (unfallen) fruit, whereas bark beetles at various growth stages were found in post‐dispersal (fallen) fruit. These results suggested that, among the dominant insect seed predators of the five dipterocarp species, weevil species oviposit on pre‐dispersal fruit and begin their larval growth before seed dispersal, whereas the oviposition and larval development of bark beetle species occurs in post‐dispersal fruit.     

Sex‐biased seed predation in gynodioecious Dianthus superbus var. longicalycinus (Capryophyllaceae) and differential influence of two seed predator species on the floral traits

Gynodioecy, the co‐occurrence of hermaphrodite and female individuals within a species, is maintained by differential reproductive success between sexes. Recently, researchers recognized that not only pollinators but also herbivores are important agents in the evolution and maintenance of gynodioecy, when herbivory is hermaphrodite biased. In this study, we investigated whether there is hermaphrodite‐biased herbivory in a gynodioecious plant, Dianthus superbus var. longicalycinus, and if so, what floral traits influenced hermaphrodite‐biased herbivory. We measured flower morphology (flower diameter, calyx tube length, corolla height and petal width) and phenology of flowers of female individuals, hermaphrodites and gynomonoecious individuals in a natural population. We also investigated seed predation and predator species. At the study site, Sibinia weevils (Curculionidae; Coleoptera) and Coleophora moths (Coleophoridae; Lepidoptera) were common pre‐dispersal seed predators in this species. The weevil appeared early in the flowering season, and weevil predation correlated with flower phenology. Because female individuals did not flower early in the season, weevil predation was less frequent in female individuals. Moth predation correlated with calyx length. The calyx length of flowers of female individuals was smaller than those of hermaphrodites, but a direct comparison of moth predation rates failed to find a significant difference among sex morphs. We found that the two seed predators had different effects on floral traits in D. superbus var. longicalycinus. We suggest that weevil predation contributes to the maintenance of gynodioecy because female individuals successfully escaped weevil predation by flowering late. It remains unclear why flower phenology is different among sex morphs.     

Density‐dependent pre‐dispersal seed predation and fruit set in a tropical tree

Negative density‐dependent demographic processes operating at post‐dispersal seed, seedling, and juvenile stages are the dominant explanation for the coexistence of high numbers of tree species in tropical forests. At adult stages, the effect of pollinators and pre‐dispersal fruit predators are often dependent on the density or abundance of flowers and fruit in the canopy, but each have opposite effects on individual realized reproduction. We studied the effect of density on total and mature fruit set and pre‐dispersal predation rates within individual tree canopies in a common canopy tree species, Jacaranda copaia in a 50‐ha forest census plot in central Panama. We sampled all reproductive sized trees in the plot (n = 188) across three years and estimated fruit set and predation rates. Population‐wide pre‐dispersal seed predation averaged between 6–37% across years. Using linear mixed effects models, we found that increased density and fecundity of conspecific neighbours increased focal tree fruit set, but also the rate of pre‐dispersal predation. An interaction between individual and neighbourhood fruit production predicted lower predation rates at high individual and neighbourhood fecundities, which suggests predator satiation at high fruit abundance levels. However, the rate at which fruit set increased with conspecific neighbour fruit production was greater than the rate at which fruit were lost to predation, resulting in an overall positive effect of neighbour density on mature fruit production in focal trees. Our results run counter to the expectation of a uniformly negative effect of density across all life stages in tropical trees and suggest further exploration of the role of spatial clumping, pollen dispersal limitation, and predation at pre‐dispersal adult stages in maintenance of species diversity in plant communities.     

Plant density can increase invertebrate postdispersal seed predation in an experimental grassland community

Janzen–Connell effects are negative effects on the survival of a plant's progeny at high conspecific densities or close to its conspecifics. Although the role of Janzen–Connell effects on the maintenance of plant diversity was frequently studied, only few studies targeted Janzen–Connell effects via postdispersal seed predation in temperate grassland systems. We examined effects of conspecific density (abundance of conspecific adult plants) on postdispersal seed predation by invertebrates of three grassland species (Centaurea jacea, Geranium pratense, and Knautia arvensis) in experimental plant communities. Additionally, we examined the impact of plant species richness and different seed predator communities on total and relative seed predation (= seed predation of one plant species relative to others). We offered seeds in an exclusion experiment, where treatments allowed access for (1) arthropods and slugs, (2) arthropods only, (3) small arthropods only, and (4) slugs only. Treatments were placed in plots covering a gradient of abundance of conspecific adults at different levels of plant species richness (1, 2, 3, 4, 8 species). Two of the plant species (C. jacea and K. arvensis) experienced higher rates of seed predation and relative predation with increasing abundance of conspecific adults. For C. jacea, this effect was mitigated with increasing plant species richness. Differences in seed predator communities shifted seed predation between the plant species and changed the magnitude of seed predation of one plant species relative to the others. We exemplify density‐dependent increase in seed predation via invertebrates in grassland communities shaping both the total magnitude of species‐specific seed predation and seed predation of one species relative to others. Further differences in seed predator groups shift the magnitude of seed predation between different plant species. This highlights the importance of invertebrate seed predation to structure grasslands via density‐dependent effects and differing preferences of consumer groups.     

Seed predation of Copaifera langsdorffii (Fabaceae): a tropical tree with supra‐annual fruiting

Seed predation is an important ecological and evolutionary force that directly affects the distribution of plant species. Copaifera langsdorffii is a tropical tree species with supra‐annual fruiting, which has its seeds predated by a specialist endogenous insect (Rynochenus brevicollis: Curculionidae) in the Brazilian savanna. Three hypotheses were addressed: (i) the predator satiation hypothesis, (ii) the resource concentration hypothesis and (iii) the larger seed predation hypothesis. A total of 112 individual C. langsdorffii were monitored monthly from January to August during four consecutive years (from 2008 to 2011) to determine the presence of fruits on each plant. All trees produced fruits in the year 2008, whereas none of them produced flowers or fruits in 2009 or 2010. Moreover, only 65 individuals (58%) marked in 2008 produced fruits in 2011. The number of fruits per plant was approximately 21% greater in 2008 than in 2011, while the percentage of seed predation was 76% greater in 2011, thereby supporting the predator satiation hypothesis. The percentage of seeds predated was not affected by the number of fruits per plant. Therefore, our data did not support the resource concentration hypothesis. Plants producing large seeds experienced more seed predation by R. brevicollis, supporting the larger seed predation hypothesis. In addition, we also observed a positive relationship between seed volume and adult R. brevicollis weight. This study demonstrates the importance of supra‐annual fruiting for increasing survivorship of C. langsdorffii seeds both at the individual and the population level, and suggests that seed predators select plants producing large seeds as a way of increasing the number of offspring.     

Pre‐dispersal seed predators and fungi differ in their effect on Luehea seemannii capsule development,seed germination,and dormancy across two Panamanian forests

Pre‐dispersal seed predation can greatly reduce crop size affecting recruitment success. In addition, non‐fatal damage by seed predators may allow infection by fungi responsible for post‐dispersal seed losses. The objectives of this study were (1) to quantify pre‐dispersal seed predation and fungal infection in a Neotropical tree species, Luehea seemannii, that produces dehiscent fruits and wind‐dispersed seeds, and (2) to link pre‐dispersal effects on seed quality to seed survival in the soil. To examine how seed predators and fungi influence seed losses, mesh exclosures, fungicide, and the combination of both treatments were applied to separate branches in the canopy of trees in Gamboa and Parque Natural Metropolitano (PNM), Panama. To determine if treatments affect seed viability and survival in the soil, half of the seeds collected from each treatment were buried for 4 weeks in forest soils and subsequently allowed to germinate before and after the breaking of dormancy. Overall, 24 percent of developing fruit were lost to insect attack. In contrast, fungi infected only 3 percent of seeds at the pre‐dispersal stage. For seeds germinated directly after collection, fungicide significantly increased germination in the wetter site (Gamboa) but decreased germination in the drier site (PNM). The pre‐dispersal insect exclosure treatment increased the fraction of seeds that remained dormant after burial in the soil. This result suggests that exposure to insect predators may cause physical damage to seeds that results in the loss of physical dormancy but does not necessarily increase the susceptibility of seeds to pathogen attack in the soil.     

Masting behaviour in a Mediterranean pine tree alters seed predator selection on reproductive output

• Context‐dependency in species interactions is widespread and can produce concomitant patterns of context‐dependent selection. Masting (synchronous production of large seed crops at irregular intervals by a plant population) has been shown to reduce seed predation through satiation (reduction in rates of seed predation with increasing seed cone output) and thus represents an important source of context‐dependency in plant‐animal interactions. However, the evolutionary consequences of such dynamics are not well understood.
• Here we describe masting behaviour in a Mediterranean model pine species (Pinus pinaster) and present a test of the effects of masting on selection by seed predators on reproductive output. We predicted that masting, by enhancing seed predator satiation, could in turn strengthen positive selection by seed predators for larger cone output. For this we collected six‐year data (spanning one mast year and five non‐mast years) on seed cone production and seed cone predation rates in a forest genetic trial composed by 116 P. pinaster genotypes.
• Following our prediction, we found stronger seed predator satiation during the masting year, which in turn led to stronger seed predator selection for increased cone production relative to non‐masting years.
• These findings provide evidence that masting can alter the evolutionary outcome of plant‐seed predator interactions. More broadly, our findings highlight that changes in consumer responses to resource abundance represent a widespread mechanism for predicting and understanding context dependency in plant‐consumer evolutionary dynamics.

     

Functional responses of contrasting seed predator guilds to masting in two Mediterranean oak species

The predator satiation hypothesis poses that synchronous and variable seed production during masting events increases seed escape through seed predator satiation. The success of this strategy depends upon the type of consumer functional response, in this case defined as the change in seed consumption rate by a predator as a function of change in seed density. Type II (where the proportion of seed consumed is highest at low levels of seed availability) and type III (where the proportion of seed consumed is highest at some intermediate level of seed availability and then declines towards zero) functional responses describe negative density‐dependence and indicate predator satiation. The type of function response should be contingent upon herbivore traits: type II responses are predicted for dietary specialist predators with low mobility, and type III responses are predicted for highly mobile, dietary generalist predators. Surprisingly, most studies have not evaluated whether functional responses vary among seed predator guilds. Here we describe the functional responses at population and individual tree level of highly mobile generalist (birds and rodents) and less mobile specialist (insects) pre‐dispersal seed predators attacking acorns of two sympatric oaks (Quercus suber and Q. canariensis) over a 10‐year period. Our results showed that in most cases specialist seed predators exhibited the predicted type II functional response at both the individual tree and population level for both oak species. However, generalist seed predators did not exhibit the predicted type III response; instead, they also exhibited a type II response at the individual tree and population level for both oak species. By independently assessing the effects of multiple seed predators associated with the same host tree species, our work highlights the influence of herbivore traits on the outcome of plant–seed predator interactions in masting species, and thus furthers our understanding of the ecological and evolutionary mechanisms underlying masting behaviour.     

Pre‐dispersal seed predation of bayberry Myrica rubra by Thiotricha pancratiastis (Lepidoptera: Gelechiidae) on Yakushima Island,Japan

We investigated pre‐dispersal seed predation by insects in a bayberry Myrica rubra Sieb. et Zucc. (Myricaceae) on Yakushima Island, Japan. To clarify the patterns of seed fate and predation, all fruit that fell into seed traps were collected to allow any insect larvae within the fruit to emerge, and the fruit were finally dissected to determine whether or not they had been attacked by insect predators. Two lepidopteran species, Thiotricha pancratiastis (Meyrick) (Gelechiidae) and Neoblastobasis spiniharpella Kuznetzov & Sinev (Blastobasidae), emerged from the fruits. Thiotricha pancratiastis is the major seed predator of M. rubra, attacking the fruits intensively during the primary stage of fruit development. Thiotricha pancratiastis had been known as a foliage feeder (leaf miner) of M. rubra, but we revealed that the insect is also an important seed predator of the bayberry.     

Entrapped carrion increases indirect plant resistance and intra‐guild predation on a sticky tarweed

Many plants employ indirect defenses against herbivores; often plants provide a shelter or nutritional resource to predators, increasing predator abundance, and lessening herbivory to the plant. Often, predators on the same plant represent different life stages and different species. In these situations intraguild predation (IGP) may occur and may decrease the efficacy of that defense. Recently, several sticky plants have been found to increase indirect defense by provisioning predatory insects with entrapped insects (hereafter: carrion). We conducted observational studies and feeding trials with herbivores and predators on two sticky, insect‐entrapping asters, Hemizonia congesta and Madia elegans, to construct food webs for these species and determine the prevalence of IGP in these carrion‐provisioning systems. In both systems, intraguild predation was the most common interaction observed. To determine whether IGP was driven by resource abundance, whether it reduced efficacy of this indirect defense and whether stickiness or predator attraction was induced by damage, we performed field manipulations on H. congesta. Carrion supplementation led to an increase in predator abundance and IGP. IGP was asymmetric within the predator guild: assassin bugs and spiders preyed on small stilt bugs but not vice versa. Despite increased IGP, carrion provisions decreased the abundance of the two most common herbivores (a weevil and a mealybug). Overall seed set was driven by plant size, but number of seeds produced per fruit significantly increased with increasing carrion, likely because of the reduction in the density of a seed‐feeding weevil. Observationally and experimentally, we found that carrion‐mediated indirect defense of tarweeds led to much intraguild predation, though predators effectively reduced herbivore abundance despite the increase in IGP.     

Increased Productivity and Reduced Seed Predation Favor a Large‐seeded Palm in Small Atlantic Forest Fragments

Large‐seeded plants are especially vulnerable to the loss of seed dispersers in small forest fragments. The palm Attalea humilis goes against this trend by reaching high abundances in small remnants. Productivity, seed dispersal and seed predation of A. humilis were investigated in two large (2400 and 3500 ha) and three small (19, 26 and 57 ha) Atlantic Forest fragments in southeastern Brazil. Palms in the small fragments produced more female inflorescences, resulting in a higher fruit production in these places. Seed dispersal rates were higher in the large fragments, where scatter hoarding was more frequent. Scolytine beetles were the main seed predators and damaged a larger number of seeds in small fragments, but predation by rodents and bruchine beetles was low irrespective of fragment size. As scolytines do not necessarily kill the seeds, low predation by bruchines and rodents, together with its own high productivity, allow A. humilis to be more abundant in small fragments despite the scarcity of its main dispersers. This increased abundance, by its turn, can increase competitive interactions between A. humilis and other plants in small fragments. Thus, abundance patterns of A. humilis are a good example of fragmentation affecting the balance of ecological interactions in a complex way, emphasizing the role of preserving ecological processes for conserving biodiversity in fragmented tropical landscapes. Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp .     

Invertebrate Seed Predators are not all the Same: Seed Predation by Bruchine and Scolytine Beetles Affects Palm Recruitment in Different Ways

Because most invertebrate seed predators are host‐specific, they are usually expected to produce Janzen–Connell patterns. This expectation was fulfilled for Astrocaryum but not for Allagoptera, depending on the effects of bruchine and scolytine predators on the seeds of these palms. Thus, the mere existence of invertebrate predation is not sufficient for generating Janzen–Connell; what matters is seed mortality, which varies between predators and between plant species for the same predator.     

Forest cover,hunting pressure,and fruit availability influence seed dispersal in a forest‐savanna mosaic in the Congo Basin

Forest fragmentation, reduced forest cover, and hunting pressure are the main threats affecting animal‐mediated seed dispersal. However, their combined effects on seed dispersal rates have been simultaneously investigated only rarely, and never in Africa. We aimed to disentangle the effects of forest cover, hunting pressure, frugivore abundance, and fruit availability at the local and landscape scales on the seed dispersal rates of Staudtia kamerunensis (Myristicaceae). To estimate the percentages of seed dispersal failure (undispersed seeds), we quantitated fruit remains below fruiting trees distributed across five contrasting sites in a semi‐natural forest‐savanna mosaic in the Democratic Republic of Congo. We used statistical analyses accounting for spatial autocorrelation and found that forest cover in the surrounding landscape, hunting level, the associated abundance of dispersers, and fruit availability all had significant effects on the percentage of seed dispersal failure. The combination of high fruit availability and reduced abundance of seed dispersers could accelerate seed disperser satiation, causing the seed dispersal system to be saturated. Our study highlights how two major factors associated with anthropogenic activities, forest cover and hunting, affect seed dispersal by animals. These findings could have far‐reaching implications for our understanding of tree‐frugivore interactions and the conservation of tropical communities.     

Mast-seeding in the cycad genus Encephalartos: a test of the predator satiation hypothesis

Mast-seeding behaviour was monitored in 18 populations of eight species of the African cycad genus Encephalartos between 1988 and 1991. The coefficient of variation (V) in annual cone production for each population ranged between 88 and 200, indicating large fluctuations in reproductive effort between years. Data were collected to determine whether mast-seeding reduced levels of predispersal seed predation by satiating seed predators in mast years and whether it resulted in a reproductive advantage over plants which reproduced more frequently. Masting intensity was greatest in those populations in which individual plants suffered the highest levels of predispersal seed predation in years when only a few plants produced seeds. The principal seed predators were two congeneric weevil species, Antliarhinus zamiae and A. signatus, which develop exclusively on cycad seeds. The lowest intensity of mast-seeding was recorded for cycad populations with low levels of seed predation and in which A. zamiae and A. signatus occurred only in low numbers or were entirely absent. Larger seed crops appeared to result in lower levels of seed predation by A. zamiae and A. signatus in four populations of E. altensteinii, and differences in seed crop size accounted for 48–66% of variation in levels of seed predation in populations of five cycad species. In one population of E. altensteinii, lower levels of seed predation in plants reproducing periodically resulted in a reproductive advantage over plants reproducing more frequently. These results are consistent with the predator satiation hypothesis. However, in most cycad populations, numbers of seed predators did not appear to decrease significantly after a period of 2–8 years between reproductive episodes and, in two of three populations examined, periodic reproduction did not increase the number of seeds surviving to dispersal over a 4-year period. These results are interpreted to mean that periodic reproduction has not evolved in response to selection imposed by seed predators, but that selection may favour those plants which experience lower levels of seed predation by coning in synchrony with the majority of plants in the population.     

The effect of limited visibility on vigilance behaviour and speed of predator detection: implications for the conservation of granivorous passerines

Ants have been traditionally considered either as predators or dispersers of seeds, but not both. That is, ant dispersal is restricted to myrmecochorous seeds, while almost all seeds removed by seed‐harvesting ants are eaten. However, harvesting ants might be simultaneously antagonistic and mutualistic towards seeds. This study analyzes the predation–dispersal relationship between seed‐harvesting ants and seeds of Lobularia maritima, a non‐myrmechorous perennial herb, in order to disentangle the dual role of ants as dispersers and predators of L. maritima seeds. The results obtained confirm the role of harvesting ants as both predators and dispersers of the non‐myrmechorous seeds of L. maritima. The removal activity of Messor bouvieri on L. maritima seeds is very important, particularly in autumn, which is the flowering and fruiting peak of this plant. It can be estimated that harvesting ants collect more than 85% of seeds, and almost 70% of them are effectively lost to predation. However, these granivorous ants also have drawbacks as seed dispersers. There is a relatively small percent of seeds collected by ants that escape predation, either because they are dropped on the way to the nest (16.4% of seeds harvested), or because they are mistakenly rejected on the refuse pile (0.9%). Abiotic dispersal of L. maritima seeds in the absence of ants occurs over very short distances from the plant stem. As seeds dispersed by ants reach a considerably greater distance than that obtained by gravity, this might represent a real advantage for the species, because it reduces intraspecific adult competition for seedlings, which directly influences seedling survivorship. These results challenge the generalization that seed removal by ants generally leads to successful seed dispersal if done by legitimate seed dispersers, or seed loss if done by seed consumers that eat them, and confirm that harvesting ants might have a dual role as both predators and dispersers of nonmyrmechorous seeds.     

Adaptive advantages of myrmecochory: the predator-avoidance hypothesis tested over a wide geographic range

The predator‐avoidance hypothesis states that once released from the parent plant, myrmecochorous seeds are rapidly taken by ants to their nests, where they are protected from predators. Previous studies conducted to test this hypothesis have frequently neglected two major aspects necessary for its verification: 1) the influence of processes acting after the seed release and 2) the spatial evenness of such processes. Thus, large‐scale variations in the mechanisms acting beyond seed release, and possibly influencing seed escape from predators, remain poorly documented. Here, we present the results of a post‐dispersal seed‐removal experiment on the myrmecochorous herb Helleborus foetidus, aimed at verifing the predator‐avoidance hypothesis by considering two key post‐release aspects of seed fate: seed destination (dispersed or nondispersed) and seed burial (buried or not buried). Experiments were performed in four different regions in the Iberian Peninsula. After three days of exposure of seeds to the main predator (fieldmice Apodemus sylvaticus), ca 30% of the seeds were removed. Seed destination affected the proportion of seeds escaping predation, but the sign, magnitude and statistical significance of the effect varied among the geographical regions. In the southern region (Cazorla), seeds dispersed in ant nests or intermediate destinations suffered scarcely any predation, but seeds under reproductive‐age plants experienced losses ca 50%. Conversely, in the northern region (Caurel), seeds in nests suffered significantly greater losses than seeds under plants or intermediate destinations, suggesting that nests were especially unsafe destinations. Seed burial had a strong impact on seed escape from predators, and its effect was highly consistent among geographical regions. In view of the consistency of its effect at different spatial scales, seed burial was a more general mechanism for predation avoidance than seed relocation to ant nests, which was habitat‐ and/or ant‐species‐dependent. Our results thus only partially support the predator‐avoidance hypothesis for the evolution of myrmecochory.     

The effects of seed abundance on seed predation and dispersal by rodents in <Emphasis Type="Italic">Castanopsis fargesii</Emphasis> (Fagaceae)

Based on the animal dispersal hypothesis and the predator satiation hypothesis, we examined the effects of seed abundance at both population (i.e., mast seeding) and community levels on seed predation and dispersal of Castanopsis fargesii (Fagaceae), a rodent-dispersed mast species in Eastern Asia. In a subtropical evergreen broadleaved forest in the Dujiangyan region of Sichuan Province, China, individual seeds with coded tin tags were tracked in two contrasting stands (seed-poor and seed-rich) over two years (2000, a low-seed year; 2001, a high-seed year). Our results showed that: (1) small rodents did not harvest the tagged seeds of C. fargesii more rapid in the high-seed year than in the low-seed year in either stand. But, seed harvest was significantly faster in the seed-rich stand than in the seed-poor stand. (2) The removal proportion was significantly lower in the high-seed year than in the low-seed year for either stand, but the removal proportion was slightly higher in the seed-poor stand than in the seed-poor stand. This indicates that high seed abundance decreases seed removal (predator satiation hypothesis). (3) There were only small differences about seed caching, seed survival and seedling establishment of C. fargesii between years and stands. During the survey, no cached seeds survived to geminate in the spring for both stands and years. (4) Mean dispersal distances of the cached seeds are much shorter in the high-seed year (3.1 m) than in the low-seed year (8.1 m) in the seed-rich stand, though similar trend is not examined in the seed-poor stand. Our results indicate that seed predation and dispersal of C. fargesii are influenced by both mast seeding and community-level seed abundance, which is not completely consistent with either the animal dispersal hypothesis or the predator satiation hypothesis, but seems more related to the predator satiation hypothesis.     

Genetic variation in flowering phenology and avoidance of seed predation in native populations of Ulex europaeus

The genetic variation in flowering phenology may be an important component of a species’ capacity to colonize new environments. In native populations of the invasive species Ulex europaeus, flowering phenology has been shown to be bimodal and related to seed predation. The aim of the present study was to determine if this bimodality has a genetic basis, and to investigate whether the polymorphism in flowering phenology is genetically linked to seed predation, pod production and growth patterns. We set up an experiment raising maternal families in a common garden. Based on mixed analyses of variance and correlations among maternal family means, we found genetic differences between the two main flowering types and confirmed that they reduced seed predation in two different ways: escape in time or predator satiation. We suggest that this polymorphism in strategy may facilitate maintain high genetic diversity for flowering phenology and related life‐history traits in native populations of this species, hence providing high evolutionary potential for these traits in invaded areas.     

Distance-dependence in two Amazonian palms: effects of spatial and temporal variation in seed predator communities

Animals aid population growth and fitness in tropical forest communities through dispersal and negatively impact populations through seed predation. The interaction between dispersal and seed predation can produce distance- or density-dependence; powerful mechanisms for maintaining species diversity incorporated in the Janzen–Connell model. Large mammals, the highest biomass seed predators of intact Amazonian communities and at risk due to human disturbance, are potentially central to these interactions. This study tests the Janzen–Connell model and investigates the impact of mammalian seed predators on seedling recruitment and maintenance of tree diversity. Patterns of both vertebrate and invertebrate seed predation and seedling recruitment were studied in the two most abundant canopy tree species in western Amazonia (Arecaceae: Astrocaryum murumuru and Iriartea deltoidea). We specifically examined effects of both spatial and temporal variation of the highest biomass seed predator in southwest Amazonian forests, the white-lipped peccary (Tayassu pecari), on recruitment through disturbed and undisturbed sites and through a fortuitous 12 year natural extinction and recolonization event of T. pecari. Distance-dependent seedling recruitment was found in Astrocaryum and Iriartea at both sites. However, the median distance of seedlings was ~1.5× farther from reproductive adults in both palms at the undisturbed site. The number of Iriartea seeds escaping predation increased 6,000% in both space and time due to the decline of T. pecari abundance. The results demonstrate that Janzen–Connell effects are stronger in intact ecosystems and tie these mechanistically to changes in seed predator abundance. This study shows that anthropogenic changes in mammal communities decrease the magnitude of Janzen–Connell effects in Amazonian forests and may result in decreases in tree diversity.