Neglected seed dispersers: endozoochory by Javan lutungs (Trachypithecus auratus) in Indonesia

Leaf monkeys are known to be leaf eaters, and thus, their potential role as seed dispersers has been neglected. However, they do also feed on fruits. To examine the role of leaf monkeys as endozoochorous seed dispersers, we studied the Javan lutung (Trachypithecus auratus) in Indonesia. We compared multiple aspects of seed dispersal processes (amount and diversity of seeds ingested, dispersal distance, and germination rate) of lutungs with that of the sympatric long‐tailed macaque (Macaca fascicularis). Over the study period, 54 percent of the lutung feces contained intact seeds, which was equivalent to the macaque feces contained seeds (62%). Seeds of at least six plant species were detected in the lutung feces, which was less than those found in the macaque feces (>19 plant species). The main species of seeds defecated by both lutungs and macaques was Ficus spp. (seed size: 0.7 mm). Seed shadow, estimated from travel distance (range: 1–299 m) and gut passage rate (24–96 h), had a unimodal‐distribution with a peak at 51–100 m, and was shorter than that reported in published accounts of macaques and other similar and smaller sized frugivores. Finally, germination rates of Ficus spp. seeds ingested by both lutungs and macaques were lower than that of the control seeds. These results imply that the dispersal effectiveness of lutungs would be lower than that of the sympatric primate frugivores. However, at a population level, lutungs could play a significant role as seed dispersers for the small‐seeded species, and therefore, more research into their frugivorous habits is warranted.     

Carnivorous mammals as seed dispersers of Myrtus communis (Myrtaceae) in the Mediterranean shrublands

ABSTRACT

The role of carnivorous mammals as seed dispersers of Myrtus communis L. in the Mediterranean environment was studied. Seeds of M. communis were found in faeces of red fox (Vulpes vulpes L.) and carnivores from the genus Martes, at four sites on the Tyrrhenic coast of Southern Italy in the period autumn-winter 1993–1995. All the study sites are covered by Mediterranean shrublands with M. communis as one of the dominant species. Content analysis of fox scats showed that fruits of M. communis constitute a relevant component of the diet of these carnivores, although other food categories were also well represented. Further investigations on the effect of mammal digestion on seed germinability showed that carnivores not only moved the seeds away from the mother plant but also enhanced their germinability. This species was known to be bird- and ant-dispersed and the adaptive implications of a multi-vectorial seed dispersal process is discussed.     

Diaspore removal and potential dispersers of the rare and protected Paeonia officinalis L. (Paeoniaceae) in a changing landscape

Paeonia officinalis L., a rare and protected species, mostly occurs in open and semi‐open habitats and is often threatened by forest and shrubland spread. To explore the still undocumented dispersal features of this species, we address the following questions. What are the relative roles of ants, small rodents, and birds as diaspore removers in open habitat and woodland? Which animal groups constitute the potential disperser assemblage and how do they shape the spatial patterns of seed dispersal? Do diaspores fit the ornithochory syndrome or do they only mimic fleshy fruits? Two experiments were performed to quantify diaspore fall and diaspore removal by animal groups, above ground and on the ground. Ants did not contribute to dispersal. In open habitats, no seed removal was detected, either on follicles or once diaspores had fallen to the ground. In woodland, diaspores were weakly removed by vertebrates on follicles and were mainly removed by rodents on the ground. As a consequence, we suggest that long‐distance dispersal events are very rare, weakening the possible escape into space of populations subject to forest spread. Several traits indicate that diaspores fit the ornithochory syndrome, but other traits are strongly reminiscent of mimetic diaspores deceiving bird dispersers. © 2007 CNRS. Journal compilation © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154 , 13–25.     

Role of Brycinus lateralis (Teleostei: Alestidae) in dispersal and germination of Nymphaea nouchali (Angiospermae: Nymphaeaceae) seeds on a seasonal floodplain of the Okavango Delta,Botswana

Seed passage through the gut of vertebrates can be important for seed dispersal, but might influence seed viability. The ability of seeds to germinate after ingestion by seed-eating fish is important for the population dynamics of some plant species, and significant in the evolution of plant–fish interactions. Certain fish in the Okavango Delta, Botswana, are fruit- and seed-eaters and could act as seed dispersers. We sampled 14 fish species in 2013, finding Nymphaea nouchali var. caerulea seeds in the digestive tracts of eight, most commonly in the striped robber Brycinus lateralis. Seeds extracted from the gut of this species had an overall mean germination success of 11.7%. This fish species might well be a legitimate seed disperser, having a positive effect on seed dispersal from parent plants in the Okavango Delta. The current study represents one of the first investigations of the likelihood of seed dispersal by fish on the African continent.     

Seed Dispersal by the Sloth Bear (Melursus ursinus) in South India1

Previous studies have shown that sloth bears are mainly myrmecophagous, but in this study, 39 and 83 percent (wet and dry season, respectively) of scats surveyed in South India contained fruits. Seeds from three of six plant species collected from scats germinated faster than seeds not passing through bears; germination percentage was not higher in any of the six species. These results suggest that the sloth bear may play an important role in the population dynamics of fleshy‐fruited species of the region.     

Overcoming seed dormancy in ex situ plant germplasm conservation programmes; an example in the endemic Argyranthemum (Asteraceae: Anthemideae) species from the Canary Islands

Germplasm of 21 diverse Argyranthemum taxa was collected from contrasting ecological zones in the Canary Islands. Seed dormancy was considerable in the majority of taxa. Extensive investigations, based on a germination test procedure algorithm for Asteraceae, with achenes from ray and disc florets of five contrasting taxa identified a procedure to promote full (85%) germination of the seeds from both ray and disc florets of all five taxa; viz, excision of the seeds from the achenes, followed by testing at 15°C with 2.6×10^-3 m GA₃ co-applied. Subsequent tests showed that this regime was effective in promoting full germination in seeds from both ray and disc florets of the remaining 16 taxa. The results are discussed in the context of ex situ plant germplasm conservation.     

Seed dormancy and germination in three Crocus ser. Verni species (Iridaceae): implications for evolution of dormancy within the genus

The aim of this work was to examine whether seed ecophysiological traits in three closely related Crocus species were associated with ecological niche differentiation and species divergence. Seeds of the temperate tetraploid cytotype of Crocus neapolitanus, the sub‐Mediterranean C. etruscus and the Mediterranean C. ilvensis were placed either on agar in the laboratory under different periods of simulated seasonal conditions or in nylon mesh bags buried outdoors to examine embryo growth, radicle and shoot emergence. In agreement with the phenology observed outdoors, in the laboratory embryos required a cool temperature (ca. 10 °C) to grow to full size (embryo length:seed length, E:S ratio ca. 0.75) but only after seeds received a warm stratification; radicle emergence then followed immediately (November). Shoot emergence is a temporally separated phase (March) that was promoted by cold stratification in C. neapolitanus while in the other two species this time lag was attributed to a slow continuous developmental process. These species have similar embryo growth and radicle phenology but differ in their degree of epicotyl dormancy, which is related to the length of local winter. Conclusions from laboratory experiments that only consider root emergence could be misleading; evaluating the phenology of both root and shoot emergence should be considered in order to demonstrate ecologically meaningful differences in germination behaviour and to develop effective propagation protocols. Although these taxa resulted from recent speciation processes, the outcomes suggest an early onset of adaptation to local ecological factors and that phylogeny may represent a significant constraint in the evolution and expression of seed traits in Crocus.     

Morphology and anatomy of physical dormancy in Ipomoea lacunosa: identification of the water gap in seeds of Convolvulaceae (Solanales)

BACKGROUND AND AIMS: Convolvulaceae is the most advanced plant family (asterid clade) that produces seeds with physical dormancy (water-impermeable seed coat). There are several different opinions about the nature of the specialized structure ('water gap') in the seed coat through which water initially enters seeds of Convolvulaceae, but none of them has been documented clearly. The primary aim of the study was to identify the water gap in seeds of Ipomoea lacunosa (Convolvulaceae) and to describe its morphology, anatomy and function. METHODS: Light microscopy, scanning electron microscopy, tissue-sectioning, dye-tracking and blocking experiments were used to describe the morphology, anatomy and function of the water gap in seeds of I. lacunosa. KEY RESULTS: Dormancy-breaking treatments caused slits to form around the two bulges on the seed coat adjacent to the hilum, and dye entered the seed only via the disrupted bulges. Bulge anatomy differs from that of the rest of the seed coat. Sclereid cells of the bulges are more compacted and elongated than those in the hilum pad and in the rest of the seed coat away from the bulges. CONCLUSIONS: The transition area between elongated and square-shaped sclereid cells is the place where the water gap opens. Morphology/anatomy of the water gap in Convolvulaceae differs from that of taxa in the other 11 angiosperm plant families that produce seeds with physical dormancy for which it has been described.     

Germination and establishment of forest sedges (Carex, Cyperaceae): tests for home-site advantage and effects of leaf litter

We investigated aspects of germination and seedling establishment that might influence the distribution and diversity of Carex species growing in the forest understory. We tested the ability of Carex communis and C. platyphylla to germinate and establish at plots where adult individuals of one of these two species, or one of two other Carex species (C. backii and C. plantaginea), occurred in an old-growth forest in southern Québec, Canada. We also tested for effects of leaf litter on germination and establishment of these sedges. From a series of experiments in the field and in a lath house, we found no evidence of home-site advantage with respect to germination or seedling establishment. Leaf litter had a negative effect on germination and establishment. The results emphasize the importance of dispersal and colonization events in determining local diversity and distribution of Carex species in upland forests. High frequency of occurrence of C. communis at our study site may result from relatively wide dispersal provided by ants, and a suite of traits associated with ant dispersal in some understory Carex species.     

A reassessment of the relations in Malaysia between ants (Crematogaster) on trees (Leptospermum and Dacrydium) and epiphytes of the genus Dischidia (Asclepiadaceae) including 'ant-plants'

Three species of epiphytic Dischidia have been investigated in terms of their relationship to ants on trees. Two species, D. parvifolia and D. astephana , are associated with ants and trees in montane areas. A clear association has been found between ants of the genus Crematogaster and the tree Leptospermum flavescens. This relationship is complex and probably both organisms benefit from the association. The ants live in tunnels in the wood of the major branches and the trunk, and the entire tree is occupied by one ant colony. Trees occupied by ants are maintained by the ants substantially clear of epiphytes other than the two species of Dischidia. The potential benefits to the tree and to the ants of this association are noted. The roots of D. astephana and D. parvifolia penetrate into the cavities of these ant nests and presumably gain nutrients from waste in the ant nests. Both Dischidia species are effectively scavenging upon the waste material from the ant-tree association. The leathery dome-shaped leaves of D. astephana are not vital to the development of the scavenging habit as D. parvifolia has lens-shaped leaves, but may offer some advantage to D. astephana by the uptake of nutrients from waste deposited by the ants under the dome-shaped leaves by interception of stem flow and by uptake of gaseous waste. Ants do not nest under these leaves. Seeds of these species of Dischidia are taken by ants into the central woody area of the ant nest where they germinate. Both Leptospermum and Dischidia can be visualized as showing adaptations to a nutient-deficient tropical montane environment. These adaptations are discussed as is the need for reassessment in this genus of the term 'ant-plant', and the need for wider recognition of the 1ant-tree' relationship between Crematogaster and Leptospermum.     

Photoinhibition of radish (Raphanus sativus L) seed germination: control of growth potential by cell-wall yielding in the embryo

The biophysical mechanism underlying photoinhibition of radish (Raphanus sativus L.) seed germination was investigated using three cultivars differing in sensitivity to continuous irradiation with far-red light (high-irradiance reaction of phytochrome). Sensitivity of germination to the inhibitory action of light was assessed by probing germination under osmotic stress (incubation in media of low water potentials adjusted with polyethylene glycol 6000) and expressed in terms of ‘germination potential’ (positive value of the water potential at which germination is inhibited by 50%). Far-red light decreases the germination potential to various degrees in the different cultivars, reflecting the light-sensitivity of germination in water. Removal of the seed coat increases the germination potential by a constant amount in darkness and light. It is concluded that germination depends on the expansive force of the embryo which can be drastically diminished by far-red light. Seed-coat constraint and expansive force of the embryo interact additively on the level of the germination potential. Photoinhibition of germination was accompanied by an inhibition of water uptake into the seed. Analysis of seed water relations showed that osmotic pressure and turgor assumed higher levels in photoinhibited seeds, compared to seeds germinating in darkness, while the water potential was close to zero under both conditions. Far-red light produced a shift (to less negative values) in the curve relating water-uptake rate to external water potential, i.e. a reduction in the driving force for water uptake. It is concluded that photoinhibition of germination results from the maintenance of a high threshold of cell-wall extensibility in the embryo.     

Big Fish are the Best: Seed Dispersal of Bactris glaucescens by the Pacu Fish (Piaractus mesopotamicus) in the Pantanal, Brazil

We studied the potential role as seed disperser of the pacu fish (Piaractus mesopotamicus, Characidae) in the Pantanal of Brazil. The most important food item in the diet of the pacu in the wet season was fruits of the palm Bactris glaucescens found in the guts of 73 percent of all fishes collected (N= 70). We found a positive relationship between fish length, weight, and gape size and the number of intact seeds in their gut. Therefore, large pacus are especially important in dispersing B. glaucescens seeds within the studied system. Since the best seed dispersers are the largest fishes, which are preferred by commercial fisheries, we predict that the ongoing over fishing in freshwater ecosystems will have major impacts on the dispersal system of fish‐dependent plants. We suggest that it is paramount to change the attitudes in fisheries management of fruit‐eating fishes and urgent to evaluate the impact of fishing on forest regeneration.     

Seed dispersal effectiveness of the western lowland gorilla (Gorilla gorilla gorilla) in Gabon

The quantitative and qualitative aspects of seed dispersal by the western lowland gorilla (Gorilla gorilla gorilla) were investigated in Gabon. Fresh faeces were collected and washed to identify and count the seeds. Seed germinability after gut passage was estimated with trials in a nursery at the study site. To assess the impact of gut passage on germination success and delay, comparative trials were run with four treatments: (i) gut passed seeds cleaned of faeces, (ii) gut passed seeds within a faecal matrix, (iii) seeds from fresh fruits surrounded by pulp, and (iv) seeds from fresh fruits cleaned of pulp. The analysis of 180 faecal units resulted in the identification of 58 species of seed. Germination trials were realized for 55 species and the mean germination success reached 46%. The impact of gut passage was investigated for Santiria trimera and Chrysophyllum lacourtianum; both species displayed higher germination success after ingestion. This study shows that gorillas effectively disperse seeds of numerous plant species, many of which provide timber or nontimber forest products or are typical of Gabonese forests. Considering the high‐quality of gorilla deposition sites, gorillas is thought to play a unique role in the dynamics of Central African forest.     

Mechanisms affecting the fate of Prosopis flexuosa (Fabaceae,Mimosoideae) seeds during early secondary dispersal in the Monte Desert,Argentina

Abstract The fate of seeds during secondary dispersal is largely unknown for most species in most ecosystems. This paper deals with sources of seed output of Prosopis flexuosa D.C. (Fabaceae, Mimosoideae) from the surface soil seed‐bank. Prosopis flexuosa is the main tree species in the central Monte Desert, Argentina. In spite of occasional high fruit production, P. flexuosa seeds are not usually found in the soil, suggesting that this species does not form a persistent soil seed‐bank. The magnitude of removal by animals and germination of P. flexuosa seeds was experimentally analysed during the first stage of secondary dispersal (early autumn). The proportion of seeds removed by granivores was assessed by offering different types of diaspores: free seeds, seeds inside intact endocarps, pod segments consisting of 2–3 seeds, and seeds from faeces of one herbivorous hystricognath rodent, the mara (Dolichotis patagonum). The proportion of seeds lost through germination was measured for seeds inside intact endocarps, seeds inside artificially broken endocarps, and free seeds. Removal by ants and mammals is the main factor limiting the formation of a persistent soil seed‐bank of P. flexuosa: >90% of the offered seeds were removed within 24 h of exposure to granivores in three of four treatments. Seeds from the faeces of maras, on the other hand, were less vulnerable to granivory than were other types of diaspores. These results suggest that herbivory might be an indirect mechanism promoting seed longevity in the soil (and likely germination) by discouraging granivore attack. On the other hand, germination did not seem to have an important postdispersal impact on the persistence of P. flexuosa seeds in the soil. Both direct and indirect interactions between vertebrate herbivores and plants may foster P. flexuosa's seed germination in some South American arid zones.