Uningested Seeds Research Articles

The black-backed jackal as a seed disperser

Black-backed jackal Lupulella mesomelas consume fruits and their seeds, yet their seed dispersing ability is poorly understood. We extracted, identified and counted seeds from 150 jackal scat samples, and quantified the viability and germination capacity of ingested seeds, using tetrazolium viability tests and germination trials. We recovered 336 seeds of Grewia occidentalis, 1025 seeds of Pappea capensis, 362 seeds of Diospyros lycioides, 296 seeds of Vachellia karroo and 2 seeds of an unknown species from the scats. Seed viability and germination of three species tested (G. occidentalis, P. capensis and D. lycioides) were significantly lower than uningested seeds, but many seeds did survive ingestion by jackal and germinated successfully. Our study confirms that jackal do play a role in endozoochory and provides the first evidence of reduced germination of these dispersed seeds, broadening our understanding of the ecological role of this heavily persecuted mesopredator.

Seed recovery and germination rate after gut passage by Korean water deer (Hydropotes inermis argyropus)

AbstractLarge herbivores can disperse seeds over long distances through endozoochory. The Korean water deer (Hydropotes inermis argyropus), an internationally vulnerable species but locally considered a vermin, is a potential endozoochorous seed dispersal vector. In this study, feeding experiments were conducted to test the efficiency of seed dispersal through gut ingestion by the Korean water deer, its temporal pattern and the effect of gut passage on seed recovery and germination rate. Eight plant species, including species that formerly germinated from its faeces, were used to feed three Korean water deer. Once the deer had consumed all the provided seeds, their faeces were collected after 24, 48, 72 and 96 h. The collected faeces were air-dried, and the number of seeds retrieved from the faeces was counted every 24 h (0–24, 24–48, 48–72 and 72–96 h). Among the eight plant species, six species were retrieved with intact seeds.Panicum bisulcatumhad the highest recovery rate of 33.7%, followed byAmaranthus mangostanus(24.5%) andChenopodium album(14.4%). Most of the seeds were recovered within the 24–48 h time interval. Germination tests were conducted on the ingested and uningested seeds for the four species which had a sufficient recovery rate. The effects of gut passage on seed germination differed according to plant species. The germination rate substantially decreased after gut passage. The results suggest that the Korean water deer can disperse seeds, potentially over long distances albeit at a high cost of low seed recovery and germination rate.

Purple prairie clover seed viability and germinability after passing through the digestive tracts of yearling steers

Endozoochory by cattle has been considered an important method for population self-regeneration; however, the effects of cattle digestive tracts on the viability and germinability of purple prairie clover (Dalea purpurea Vent.), a native North American species, remain understudied. The experiment was conducted at the Agriculture and Agri-Food Canada Swift Current Research and Development Centre in the semiarid prairie of western Canada. Purple prairie clover seeds extracted from cattle dung pats were tested for germination and compared with uningested and scarified seeds from the same paddock. The germination percentage (within 200 d) of the ingested seeds was 16.5% ± 0.8%, two times higher after passing through digestive tracts than uningested seeds (8.3% ± 1.2%), while 76.6% ± 1.5% of ingested seeds remained dormant. As many as 92.4% ± 0.9% of purple prairie clover seeds survived digestion due to their high hard seed rate (90.5% ± 1.0%), which was lower than the uningested seeds by 6.9%. Therefore, cattle dispersing purple prairie clover seeds with high viability and germinability is a low-cost method to increase and rejuvenate purple prairie clover for late-season grazing pastures.

Diet of the endangered big-headed turtle Platysternon megacephalum.

Populations of the big-headed turtle Platysternon megacephalum are declining at unprecedented rates across most of its distribution in Southeast Asia owing to unsustainable harvest for pet, food, and Chinese medicine markets. Research on Asian freshwater turtles becomes more challenging as populations decline and basic ecological information is needed to inform conservation efforts. We examined fecal samples collected from P. megacephalum in five streams in Hong Kong to quantify the diet, and we compared the germination success of ingested and uningested seeds. Fruits, primarily of Machilus spp., were most frequently consumed, followed by insects, plant matter, crabs and mollusks. The niche breadth of adults was wider than that of juveniles. Diet composition differed between sites, which may be attributable to the history of illegal trapping at some sites, which reduced the proportion of larger and older individuals. Digestion of Machilus spp. fruits by P. megacephalum enhanced germination success of seeds by about 30%. However, most digested seeds are likely defecated in water in this highly aquatic species, which limits the potential benefit to dispersal. The results of our study can be used by conservation-related captive breeding programs to ensure a more optimal diet is provided to captive P. megacephalum.

Seed viability and germination success of Acacia tortilis along land-use and aridity gradients in the Eastern Sahara.

Our study focuses on the keystone species Acacia tortilis and is the first to investigate the effect of domestic ungulates and aridity on seed viability and germination over an extensive part of the Eastern Sahara. Bruchids infest its seeds and reduce their viability and germination, but ingestion by ruminant herbivores diminishes infestation levels and enhances/promotes seed viability and germination. The degree of these effects seems to be correlated with animal body mass. Significantly reduced numbers of wild ruminant ungulates have increased the potential importance of domestic animals and pastoral nomadism for the functionality of arid North African and Middle Eastern ecosystems. We sampled seeds (16,543) from A.tortilis in eight areas in three regions with different aridity and land use. We tested the effect of geography and sampling context on seed infestation using random effects logistic regressions. We did a randomized and balanced germination experiment including 1193 seeds, treated with different manure. Germination time and rates across geography, sampling context, and infestation status were analyzed using time-to-event analyses, Kaplan-Meier curves and proportional hazards Cox regressions. Bruchid infestation is very high (80%), and the effects of context are significant. Neither partial infestation nor adding manure had a positive effect on germination. There is a strong indication that intact, uningested seeds from acacia populations in the extremely arid Western Desert germinate more slowly and have a higher fraction of hard seeds than in the Eastern Desert and the Red Sea Hills. For ingested seeds in the pastoralist areas we find that intact seeds from goat dung germinate significantly better than those from camel dung. This is contrary to the expected body-mass effect. There is no effect of site or variation in tribal management.

Behavior of kestrels feeding on frugivorous lizards: implications for secondary seed dispersal

Secondary seed dispersal is a multistep system that includes 2 or more dispersal processes that can increase the distance from which seeds arrive. This phenomenon is relatively common in some habitats of subtropical oceanic islands due to the frequent frugivore‐ predator interactions found in them. In this study, we describe how the Eurasian Kestrel is an effective disperser of plants in the secondary seed dispersal process, through interaction with frugivorous lizards. Experiments using captive wild kestrels, along with field data, showed that predation of kestrels on lizards leads to a secondary seed dispersal with 2 possible outcomes: 1) most seeds (89%) are not consumed by kestrels because they reject the lizards’ digestive tracts and so receive only the gut treatment of lizards and 2) a small fraction of seeds (11%) appeared inside the kestrel pellets as a result of indirect ingestion by this raptor, thus undergoing double gut treatment. So, 2 different seed dispersal distances may result from this interaction: 1) when the kestrels capture the lizard and transport it to a perch where the seed-containing guts are discarded and 2) when they indirectly ingest a few seeds from lizards, consequently increasing the dispersal distance. Seeds from the Macaronesian plant species Rubia fruticosa were tested, finding that those passed through kestrels had a lower germinability than those that remained inside the rejected lizards’ digestive tracts, which had similar germination rates to those from control plants (uningested seeds). The kestrel can be considered an important and effective long-distance seed disperser due to the high abundance of frugivorous lizards in their diet, their stereotyped consumption behavior, and the effectiveness of their seed dispersal. Key words: Canary Islands, diplochory, endozoochory, frugivorous lizards, long-distance seed dispersal, predatory behavior, seed germination. [Behav Ecol]

Secondary seed dispersal systems, frugivorous lizards and predatory birds in insular volcanic badlands

Summary 1 Secondary seed dispersal occurs whenever a seed is dispersed in two or more different dispersal events, so that different dispersal agents (e.g. animal frugivores or invertebrates) contribute to different events. Three secondary seed dispersal systems, in which lizards and predatory birds participate, are studied in Lanzarote (Canary Islands). 2 Seeds from all three plant species studied (Lycium intricatum, Rubia fruticosa and Asparagus nesiotes) were found with the remains of lizards (Gallotia atlantica) when they appeared inside shrike (Lanius meridionalis) and kestrel (Falco tinnunculus) pellets. This suggests that these two avian predators might secondarily disperse these plants by incidentally ingesting seeds when they prey upon the frugivorous lizards. 3 Lycium and Rubia seeds dispersed by Falco had significantly thinner seed coats compared to the other treatments (Gallotia and Lanius) and to uningested seeds. Correlated with this result, seed hardness increased from Lycium (the softest coat), to Rubia (intermediate values), to Asparagus. 4 Seed viability was high in all three species, although both viability and germination were significantly reduced in seeds of Lycium and Rubia dispersed by Falco. 5 The seed distribution was markedly different, Gallotia being an important disperser in the open ground microhabitats, Lanius in hillocks and Falco in hills. Because all three plant species were present in all these microhabitats, our observations suggest that the dispersal of these plants might be associated with the differential use of the habitat by the different dispersers. 6 Synthesis: Contrary to some long-distance seed dispersal (LDD) paradigms, the complex seed dispersal systems we describe are common and affect an important number of seeds that are moved each year to particular microhabitats. Finally, the simultaneous ecological factors analysed in this study support the hypotheses that diplochory by double endozoochory could have played a more important role in LDD events than is currently recognized, both in recent volcanic areas (lowlands) and also probably in the colonization of other subtropical islands.

Seed dispersal by small herbivores and tidal water: are they important filters in the assembly of salt‐marsh communities?

Summary Characteristics of internal seed dispersal (endozoochory) by European Brown Hares were compared with similar dispersal by Brent Geese. Hares deposited more seeds of mid‐successional, perennial, high‐marsh species than did geese, which deposited more seeds of early successional, annual, low‐marsh species. Seed survival and germination of salt‐marsh species were higher after ingestion and passage through the digestive system of hares compared with geese. Both hares and geese had a negative effect on the percentage of seeds that germinated in comparison with uningested seeds. Small herbivores (hares and geese) dispersed two orders of magnitude fewer seeds than those dispersed by tidal water. Thus these herbivores are not likely to be important filters (constraints) in community assembly at this salt‐marsh site on a coastal island in the Netherlands.

Effects of macaque ingestion on seed destruction and germination of a fleshy‐fruited tree, Eurya emarginata

Effects of macaque ingestion were examined on both seed destruction during passage through the gut and germination enhancement after defecation, using typically endozoochorous fruits of Eurya emarginata. Mechanical and chemical actions associated with the ingestion were also examined. A fruit‐feeding experiment found that 4.4% of ingested seeds could pass intact through the gut of Japanese macaques. No significant difference was detected between the seed passage percentages of six Eurya emarginata trees despite individual variation in seed weight and hardness, implying that mastication is a major factor in the severe seed mortality during the gut passage. Seeds in intact fruits showed lower germination percentage and longer germination delay than seeds with the flesh removed artificially. In contrast, no enhancement in germination was observed after passage through the gut. A series of seed treatment experiments indicated that seed abrasion did not affect germination percentage, though acid and heat‐exposure enhanced the germination. The two factors, severe seed destruction and germination enhancement by flesh removal, opposed each other. With the survival proportion of uningested seeds taken as 1.0, the survival proportion of ingested seeds was estimated as 0.49 with the 95% confidence interval of 0.14–1.46, which indicated no significant difference between the proportions of ingested‐ and uningested‐seeds.

Effect of passage through duck gut on germination of fennel pondweed seeds

Vertebrates are important seed dispersers for many plants. In addition to transport of seeds, ingestion often affects the proportion or rate of seed germination. We present one of the first studies comparing the effects of different waterbird species on the seeds of a subcosmopolitan pondweed, Potamogeton pectinatus . We also pre- sent the first comparison of the effects of by ducks (mallard Anas platyrhyn- chos, shoveler A. clypeata and wigeon A. penelope) and physical-chemical simulation of digestion on pondweed seed germination. In two experiments differing in the length of the preceding stratification period, two to three individuals per duck species were force-fed 150 seeds each. Average retrieval, total germination and germination rate did not differ significantly between duck species. Germination rate was higher for duck ingested seeds, intermediate for scarified seeds (i.e. after mechanical removal of the epicarp+mesocarp) and lowest for the controls and acid treated seeds, independ- ently of the length of the stratification period. Total germination, however, did not dif- fer significantly among duck-ingested, scarified, control and acid treated seeds. Conse- quently the changes in germination rate after ingestion by ducks seem related to the grinding treatment in the gut and unrelated to exposure to acidic conditions. The co- existence of ingested and uningested seeds within a given seed cohort will increase the diversification of seed germination patterns, which can favour the colonisation of habi- tats characterised by unpredictable environmental conditions.

Endozoochorous seed dispersal by martens ( Martes foina, M. martes) in two woodland habitats

Summary Endozoochorous seed dispersal by stone and/or pine martens ( Martes foina , M. martes ) was investigated throughout the main fruiting period (July through October) in two contrasting forest areas (acid soil and mesic) in Brandenburg, Germany. The amount of seeds dispersed by martens was determined by counting the seeds per scat, and seed dispersal was related to plant abundance in the study areas. In addition, the germinability of dispersed seeds was tested. For the three most commonly dispersed seeds percent germination of ingested and uningested seeds was compared. In the acid-soil forest, ten species and more than 4,000 seeds per 10 g of dry mass faeces were recovered, whereas the faeces from the mesic forest yielded only seven species and less than 500 seeds per 10 g. Almost all endozoochorous seeds were from fleshy-fruited species growing in the forest stands; very few seeds were transported from adjacent settlements into the woodlands. Seeds of Vaccinium myrtillus predominated in faeces from the acid-soil forest where it was one of the most abundant herb layer species, followed by Rubus idaeus . In the mesic forest, Rubus caesius/fruticosus agg. and Vaccinium myrtillus seeds were most abundant in marten scats, while Liliaceae species with toxic berries lacked endozoochorous transport by martens despite being abundant in the study area. Ten of the 12 dispersed species germinated from scat samples. In contrast to seeds of Rubus idaeus and Rubus caesius/fruticosus agg., those of Vaccinium myrtillus showed a germination enhancement after having passed through the digestive tracts of martens, possibly due to abrasion of their soft seed coat. Both martens are considered to be important dispersal vectors for fleshy-fruited plants inhabiting the understorey of Central European forests.

Germination Rates of Tree Seeds Ingested by Coyotes and Raccoons

The effect of ingestion by coyotes (Canis latrans) and raccoons (Procyon lotor) on seed germination was investigated for four tree species in Illinois. The germination rate of persimmon (Diospyros virginiana) seeds ingested by raccoons was significantly higher than the rate for uningested seeds. Both were significantly higher than the rate for coyote-ingested seeds. Among coyote-ingested seeds, germination rates of persimmon were significantly higher when seeds were protected by undigested fruit pulp or intact seed sheaths thus reducing the exposure of seeds to gastrointestinal enzymes. American plum (Prunus americana) seeds ingested by coyotes had a significantly lower germination rate compared to uningested seeds, whereas germination of pawpaw (Asimina triloba) seeds was similar between coyote-ingested and uningested seeds. Germination was significantly lower for hackberry (Celtis occidentalis) seeds ingested by raccoons compared to uningested seeds. Ingestion improved germination only for persimmon seeds consumed by raccoons, but tree species may realize other benefits from dispersal by coyotes and raccoons (e.g., decreased parental competition).

Evidence for a Role in Seed Dispersal by Two Tropical Herbivorous Turtles

The capacity for seed dispersal by two herbivorous turtles, the aquatic Rhinoclemmys funerea and the terrestrial R. annulata, was investigated in the vicinity of Tortuguero, Costa Rica. Defecated seeds of several riparian plant species from R. funerea feces and defecated seeds of several terrestrial plant species, mainly characteristic of treefall areas, from R. annulata feces germinated as well as uningested seeds with which they were compared. The Rhinoclemmys funerea habit of regularly emerging from water to forage and defecate on river banks may contribute to the establishment of riparian species such as Dieffenbachia longispatha and Ficus glabrata. Rhinoclemmys annulata forages through tropical wet forest habitats, spending a disproportionate amount of time feeding in treefall areas. Its movement between these areas and defecation of seeds while foraging in them may contribute to the establishment of the distinctive flora of these small, disjunct habitats.

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

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

Differential Germination of Two Closely Related Species of Solanum in Response to Bird Ingestion

This study evaluated the effect which ingestion of seeds of Solanum nigrum and S. luteum by bulbuls (Pycnonotus xanthopygos) and blackbirds (Turdus merula) had on their germination, and tried to reveal the ecological implications of such endozoochory. Those closely related plant species are often sympatrical but whereas S. nigrum is a noxious weed invariably associated with human disturbed habitats, S. luteum may also occur in natural plant associations. Our data indicated that germination of seeds of S. nigrum was not affected by ingestion by either bulbuls or blackbirds. On the contrary, germination of the seeds of S. luteum was significantly (p < 0.01) improved by their ingestion by either bird species. Comparative scanning electron micrographs of the seeds showed that seed coat sculpture of S. nigrum was not affected by ingestion. In contrast, in ingested seeds of S. luteum, the sculpture of the seed coat was abraded compared with the uningested seeds; here, also, in the seeds ingested by the bulbuls, the intracellular contents disappeared, and in most of those ingested by blackbirds, there was destruction of the cell wall as well. Assumedly abrasion of the seed coat sculpture of S. luteum increases the seed coat permeability and consequently germination. It would seem that germination and dispersal of this more arid species which grows in unstable habitats is mediated largely by birds, whereas the germination of S. nigrum seeds is not affected by avian ingestion; for this weed, birds serve only as dispersal agents.