This study aimed to better understand the role of rodents as seed predators and dispersers in the fynbos biome at De Hoop Nature Reserve, South Africa in May and June, 2013. Based on previous studies I hypothesised that the large, nut-like seeds of Ceratocaryum argenteum (Restionaceae) are scatter-hoarded by rodents and that rodent seed choices and seed fates are affected by seed size and hull thickness. Field trials using three seed types showed that smaller seeds with a high reward and low processing cost were consumed significantly(p<0.01) more than large, thick hulled seeds. Application of wire tags to facilitate discovery of relocated seeds had no significant influence on seed choice (p>0.05), but further research should be conducted to determine if spooling of C. argenteum seeds influences rodent seed choice. Smaller seeds with a high-reward and low processing cost showed a significantly greater percentage of usage (p<0.01) where seed stations were encountered and exploited. Rhabdomys pumilio was confirmed as being the most common murid at the study site, however, it seems unlikely that it scatter-hoards C. argenteum seeds, as no consumption or burial of seeds was observed. However, R. pumilio did show an interest in C. argenteum seeds and attempted to consume some seeds or carried seeds over distances not significantly different (p>0.05) from the observed distances between nearest neighbour C.argenteum plants before discarding them on the soil. Additionally, the maximum distance R. pumilio moved C. argenteum seeds was commensurate with the maximum distance between nearest neighbour C. argenteum stands, so the end fate of the seeds remains unknown. Further research should account for seasonal variability in scatter-hoarding behaviour.

Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment.

Primates have important ecological roles as seed dispersers and seed predators in tropical forests. Orangutans are large-bodied frugivores that consume a high diversity of plant species, however, relatively little is known about their ecological roles. Ecological interactions are critical processes for ecosystem dynamics, structures, and functions. This dissertation investigated Bornean orangutans’ (Pongo pygmaeus wurmbii) ecological roles by studying orangutan patterns of frugivory, seed dispersal, and seed predation, dispersed seed spatial patterns, and seed fate outcomes. This research was conducted at the Cabang Panti Research Station in Gunung Palung National Park, Borneo, Indonesia. Chapter 2 analyzes orangutan seed dispersal behavior using the seed dispersal effectiveness framework to identify which fruits orangutans are most effectively dispersing. Orangutans predated seeds more frequently than they spat or swallowed seeds. Additionally, the fruits preferred most by orangutans were highly predated. Despite the prevalence of seed predation, orangutans also frequently dispersed seeds, 71.8% of fecal samples contained seeds with a mean of 28 seeds (>2mm) per fecal sample. Chapter 3 models orangutan seed dispersal distances to understand how far orangutans are dispersing seeds across the landscape and if seeds are dispersed across habitat types. This study found orangutans dispersed seeds, on average, 400-650m. There were occasional long distance seed dispersal events, and the maximum dispersal distance was 2.2km. Both male and female orangutans dispersed seeds long distances (>1km). Unflanged male orangutans dispersed seeds the longest mean distances of the age-sex classes with the farthest mean maximum distances at the 80-hour gut retention time. In Chapter 4, the fate of seeds dispersed by orangutans is investigated along with the variation underlying the fate of dispersed seeds. Camera traps and seed tracking studies revealed the orangutan primary seed shadow was heavily reshaped post-dispersal. By 6-months post dispersal, most orangutan dispersed seeds (86-87%) had been removed, mostly by seed predators, and almost all of the remaining seeds (11-14%) had died. This dissertation reveals orangutans are involved in important ecological interactions. Orangutans disperse and predate high quantities of seeds from many plant genera, and the loss of the orangutan would likely negatively affect their natural ecosystems. / 2026-10-31T00:00:00Z

Terrestrial mammals affect numerous aspects of plant demography, colonization, and community structure in Neotropical forests. Granivorous mammals destroy seeds via seed predation and seedlings through herbivory, negatively affecting plant fitness. Mammals can also positively affect plants by dispersing or hoarding seeds. Seed fate outcomes are contingent on the interaction between mammal seed handling strategies and the intrinsic anti-predation defenses possessed by seeds. In field experiments at La Selva Biological Station, I investigated how collared peccaries (Pecari tajacu) and Central American agoutis (Dasyprocta punctata) affect five species of large seeds that have various defenses against predation. Overall, peccaries consumed and killed most non-defended and chemically-defended seeds but they could not destroy seeds with physical defenses. Agoutis killed non-defended and physically-defended seeds, but not seeds with chemical defenses. Using seeds of Mucuna holtonii, I investigated how chemical and structural defenses deter mammal and insect seed predation respectively. I also determined how endosperm removal by invertebrates affects seed germination and seedling biomass. Chemical defenses protected seeds from rodents, but not ungulates that digest seeds via pregastric fermentation. Physical defenses protected seeds from invertebrate seed predators, and removal of endosperm negatively affected both seed germination and seedling growth. To determine how scatter-hoarding by agoutis affects seed escape from seed predators, germination, and seedling growth, I created simulated agouti hoards. I also investigated how mammals affect young seedling survival. Hoarding enhanced seed survival, germination, and seedling growth for most species of seeds. Terrestrial mammals killed some seedlings via seed predation rather than by herbivory. Overall, large mammal activity in La Selva negatively affected seed and seedling survival and this likely influences many aspects of forest dynamics.

I studied the insect seed predator community on mesquite plants (Prosopis spp.) to investigate patterns of community composition in space and time, attempting to better understand the factors that led to the coexistence of many seed predator species on a single plant. This dissertation begins by testing the controversial species limits of Prosopis section Algarobía because hosts may act as environmental filters to insect seed predators. I found evidence for at least eight North American Prosopis species (section Algarobía). Second, I describe and add to the known natural history of 113 arthropod species among 315,174 individuals I collected from seedpod samples across the United States and Mexico. These samples included 187 trees from eight North American Prosopis species from section Algarobía and three from section Strombocarpa. Third, I examined reproductive timing in Prosopis and show that neighboring trees of the same species reproduce synchronously, whereas closely related species stagger reproduction. I found that photoperiod is the main cue that initiates flowering, but that multiple cues are involved. Thus, synchronous reproduction may act as an equalizing process that facilitates coexistence of seed predators in this system. Fourth, I tested for evidence of spatial and temporal niche partitioning among Prosopis seed predators. I found that the rank abundance of seed predators varies little over space and time, suggesting that this community exists in a homogeneous competitive environment. I also found that although a few species restrict the use of seeds to particular host plants or developmental stages of the pods, there is little evidence of niche partitioning. Finally, I looked for evidence of competition between seed predators and examined a number of factors that may allow for coexistence of these species. I found no evidence of interspecific competition or facilitation, suggesting that species somehow either avoid competition or that present patterns are the product of past competitive interactions. Natural enemies occur too sporadically to allow for apparent competition and I found no relationship between their occurrence or abundance and those of the seed predator species I studied. I found a positive correlation between rank abundance ability and fecundity, inconsistent with expectations of life-history or competitive-colonization trade-offs. Therefore, the only stabilizing process consistent with patterns found in this system is the niche regeneration hypothesis. I found that one seed predator species lays eggs most often away from both interspecific and intraspecific competitors, a pattern consistent with active avoidance as a second equalizing process within this system.

Seed dispersal in New Zealand relies on a different guild from the one present before the arrival of humans into the islands. Post-dispersal biotic and abiotic filters have also changed due to the introduction of seed predators and herbivores. The aim of this thesis was to evaluate the actual contribution of seed dispersers to the patterns of seed fall and to understand the effects of biotic (seed density, predators, distance from conspecifics) and abiotic (pH, canopy openess, etc) factors on seed and seedling survival. I expected that tree species with different fruit sizes would be selected by different assemblages of dispersers, therefore being deposited and recruiting differentially on the forest floor. I analyzed the changes in small-scale seed diversity with the use of seed traps during two seasons in two 0.36 ha plots in a mixed broadleaf-podocarp temperate forest. The diversity of seeds was lower for in-fruit seeds (1.40 species per grid-cell) than for bird-dispersed seeds (2.62). The dominant species D. cupressinum was dispersed towards con- and heterospecific canopies (wind-dispersed trees Weinmannia racemosa and Metrosideros umbellata), giving a probable mechanism for the observed increase in finescale seed diversity. Then, using a 12-year dataset on seed fall I analyzed the changes in ground-level seed heterogeneity generated by bird-dispersed seed rain (propagule-scale) relative to the canopy composition (adult-scale) on six tree species. A Non Metric Multidimensional Scaling analysis demonstrated that the differences in species composition between sampling points (seed traps) were larger for tree canopies than for dispersed seeds. Different tree species acted as seed importers and/or exporters, although these patterns were not explained by fruit size or the richness of the disperser assemblages. I also investigated the effects of seed and seedling density on seed predation, seedling emergence and seedling survival to 12 months of five tree species. Seed predation increased with seed size, and it was higher at high density only for the largest-seeded species Beilschmiedia tawa and Prumnopitys ferruginea. Access of seed and seedling predators to the propagules was the main factor affecting seedling emergence and seedling survival. Abiotic variables were important for germination and seedling survival of the two small-seeded species, but only biotic predictors (mammalian exclosure and density) were important for medium and large-seeded species. Finally, using a split-plot experimental design I measured the effects of (a) the presence of conspecific canopy, (b) high conspecific seed densities and (c) introduced (or invasive) mammal access on seedling emergence and seedling survival (Janzen-Connell effects). Distance effects were stronger than density effects, and mediated by native and exotic predators. Final survival under conspecifics was strongly reduced in both species, with zero survival of B. tawa under conspecifics, and near zero (2/896) under D. dacrydioides. Seed dispersal service in New Zealand is still enough to produce changes in the spatial pattern of seed deposition in the forest. Post-dispersal processes such as seed predation and herbivore are having strong impacts on the survival and potential recruitment of plant species. Large-seeded trees are the most affected in terms of the impact of introduced mammals on seed predation, but seedling survival is affected independent of seed size. However, it is unknown how different these ecological processes are from the original situation without pests in New Zealand. The results of my research can contribute with valuable information for future research trying to understand the consequences of seed dispersal for recruitment, as well as inform complex models that try to predict the long-term impacts of the exotic mammals introduced in New Zealand.

Orientador: Wesley Rodrigues Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-25T04:47:26Z (GMT). No. of bitstreams: 1 Azevedo-Niero_IaraRoberta_M.pdf: 2884673 bytes, checksum: a3db764152d8b49c5c45f5689a19fb39 (MD5) Previous issue date: 2014 / Resumo: Araras-azuis (Anodorhynchus hyacinthinus) são especialistas alimentares, sendo que a população que ocorre no Pantanal se alimenta prioritariamente do endosperma de sementes de acuri (Attalea phalerata) e bocaiuva (Acrocomia sp.). Mesmo considerando o alto valor nutricional e energético das sementes, estudos apontam que araras-azuis passariam por períodos de déficit proteico durante o período de muda de penas e oviposição. É comum as araras-azuis se alimentarem destes itens no solo, onde também ocorre a predação dessas sementes por larvas de besouros bruquíneos, do gênero Pachymerus. Tais larvas são três vezes mais proteicas que o endosperma das sementes. Considerando a possibilidade de araras-azuis, ao se alimentarem no solo, se depararem com sementes já predadas por larvas de besouro, e tendo em vista algumas variações que seu alimento pode apresentar no ambiente, o intuito deste trabalho foi estudar seleção e preferências alimentares das araras-azuis em relação à oferta de alimento, além de averiguar se as larvas de besouro são utilizadas em sua dieta. As sementes de acuri e bocaiuva estão disponíveis às araras-azuis durante todo o ano. O período seco apresentou maior proporção de sementes predadas por bruquíneos do que o período úmido, para as duas espécies de palmeiras. Áreas fechadas tiveram mais sementes predadas por bruquíneos do que áreas abertas, com exceção às sementes de acuris no período seco, quando a predação foi semelhante. Independentemente da espécie da palmeira, da área, ou do período, sementes coletadas sem exocarpo estavam mais predadas por bruquíneos do que sementes com exocarpo, e sementes velhas mais predadas por bruquíneo que as novas. Sementes que continham larvas de besouro possuíam tamanhos semelhantes, porém eram mais leves que as que não continham. Araras-azuis selecionaram sementes com quatro e cinco lóculos e preferiram sementes sem exocarpo, mas não apresentaram preferências entre sementes com e sem larvas de bruquíneo. Aparentemente as araras não expeliram ou rejeitaram larvas encontradas nas sementes. Restos de larvas não foram encontrados após inspeção dos locais onde ocorreram os experimentos. Considerando que um indivíduo cativo ingeriu larvas, é possível inferir que araras de vida-livre podem ingerir larvas de bruquíneo quando as encontram. Mesmo sendo especialistas, araras-azuis exibem preferências por determinados itens alimentares. A preferência por sementes sem exocarpo corrobora estudos anteriores, que demonstraram menor tempo de manipulação, mas também maior probabilidade de predação por larvas de bruquíneo para estas sementes. Araras-azuis podem não saber discriminar entre sementes com e sem larvas de bruquíneo ou apenas podem não preferir uma em detrimento da outra. Sementes com mais lóculos talvez otimizem o aporte energético do endosperma em relação ao custo para quebrá-las, ou ainda favoreçam a chance de encontro de larvas de bruquíneo contra sementes com menos lóculos. Alimentar-se de sementes no solo pode representar um aporte adicional de proteína às araras, especialmente durante o período seco, enquanto as larvas de bruquíneos se desenvolvem em adultos. Esta estratégia representaria uma adaptação alimentar importante para a arara-azul no Pantanal, suprindo uma dieta proteica previsível no tempo e no espaço, e reduzindo os riscos de períodos de deficiência nutricional / Abstract: Hyacinth macaws (Anodorhynchus hyacinthinus) are food specialists and the population that occurs in the Pantanal feeds mainly on the endosperm of acuri (Attalea phalerata) and bocaiúva (Acrocomia sp.). Even considering the high values of energy and nutrients of those seeds, studies suggest that Hyacinth macaws undergo periods with lack of protein during moult and oviposition. Hyacinth macaws regularly feed on seeds on the ground, where Bruchinae beetle larvae of the genus Pachymerus also attack the seeds. Those larvae have three times more protein than the endosperm of the seeds. Considering that Hyacinth macaws can find seeds attacked by larvae while feeding on the ground, as well as some variations their food may present in the habitat, the aim of this work was to study the food selection and dietary preferences of the Hyacinth macaws in relation to their food supply, and to verify whether bruchid larvae are part of their diet. Acuri and bocaiuva seeds are available to macaws throughout the year. For both palm species, the dry period showed a higher proportion of seeds attacked by bruchids than the wet period. Forested areas had more seeds attacked by bruchids than open areas, except for acuris during the dry season, when predation was similar. Regardless of the kind of seed, area, or period, seeds collected without exocarp were more predated by bruchids than seeds with exocarp, and old seeds most predated than new ones. Seeds containing bruchid larvae showed similar size and lighter weight than those not containing. Hyacinth macaws selected seeds with four and five locules and preferred seeds without exocarp, but showed no preference between seeds with and without larvae. Seemingly, Hyacinth macaws not expelled or rejected larvae found in the seeds. Remains of larvae were not found after inspection of the sites where the experiments occurred. Since a captive Hyacinth macaw ingested larvae, it is possible to infer that the free-living ones can also ingest them. Even being food specialists, Hyacinth macaws exhibit preferences for certain food items. The preference for seeds without exocarp supports previous studies that demonstrate less handling time, but also higher probability of predation by bruchid larvae for those seeds. Hyacinth macaws may not be able to distinguish between seeds with and without bruchid larvae or may just not prefer one to the other. Seeds with more loci may optimize the energy intake by the endosperm regarding the costs to break it, or even favor the chance of encountering bruchid larvae against seeds with less locules. Feeding on seeds on the ground may represent an extra intake of protein to Hyacinth macaws, especially during the dry season, while bruchid larvae undergo their development into adults. This strategy would represent an important feeding adaptation to Hyacinth macaw in the Pantanal, providing a predictable protein diet in time and space, and reducing the risk of periods of nutritional deficiency / Mestrado / Ecologia / Mestra em Ecologia

No description available.

The decline in range and density of frugivorous birds worldwide could have consequences for the functioning of ecosystem processes such as seed dispersal. I endeavoured to determine the effects of bird declines on seed dispersal and assess the current status of dispersal in New Zealand. My first aim was to determine whether decreased bird density can reduce competitive interactions between birds, leading to birds concentrating on higher-reward fruit species. I measured fruit removal rates and fruit preferences of birds in Canterbury forest remnants with high (Hay and Prices) and low (Lords and Kaituna) bird densities. Removal rates of Melicytus ramiflorus and Coprosma spp. were lower at low-bird sites, and the size of this effect was greater for low-reward plant species. Coprosma areolata (a low-sugar fruit) had limited dispersal at Kaituna (59% fruit removed by end of 2012 season), compared with 92% removal at Hay, whereas 99-100% of M. ramiflorus and C. robusta (higher-sugar) fruits were removed at both sites. My second aim was to determine whether seed dispersal by introduced possums (Trichosurus vulpecula) can compensate for bird declines. I analysed seeds present in possum and bird faecal samples collected at Kowhai Bush, Kaikoura. Possums dispersed <3% of the total seeds, much less than bellbirds (21%), silvereyes (16%), song thrushes (33%) and blackbirds (28%). Possums also destroyed approximately 15% of seeds found in faeces, reduced the germination of gut-passed C. robusta seed to half of that from bird faeces (30% vs. 60-70%), and did not swallow fruits any larger than those moved by the much smaller birds (c. 7 mm diameter). My third aim was to determine the relationship between percentage of fruits dispersed and distance from parent tree for three large-seeded trees; Beilschmiedia tawa, Elaeocarpus dentatus, and Prumnopitys ferruginea. I fitted dispersal kernels to the observed dispersal distances out to 50 m for both undispersed whole fruits and seeds consumed by a bird, and found that dispersal quantity below the parent tree strongly underestimates total dispersal quantity. The average percentage dispersed overall was 81% for B. tawa, 75% for E. dentatus and 91% for P. ferruginea, and for all species finding only 11-18% clean seeds under the parent tree would correspond to an overall percent dispersed of at least 50% of the whole seed crop. My final aim was to determine the consequences of dispersal failure for recruitment in three plant species; Elaeocarpus hookerianus, Ripogonum scandens, and C. robusta. I compared the fate of dispersed and undispersed seeds in a manipulative field experiment. Exclusion of mammals plus removal of fruit pulp had the greatest effect on survival, while the combined effects of dispersal failure (under parent, high density, whole fruit) and inclusion of mammals decreased the number of live seedlings present at the final count by 75-92%. Overall, most native plants were receiving adequate dispersal and there was little evidence for strong risks to plant regeneration from dispersal failure, despite the reduced bird densities and ongoing negative effects of introduced mammals in New Zealand.

Positive frequency-dependent predation (FDP) has been proposed as a species coexistence mechanism and theoretical models have shown how it may function. In positive FDP a rare species receives a temporary reprieve from predation pressure allowing an increase to its population growth rate and a chance for it to recover from rarity. This study tests for frequency-dependent foraging by granivorous desert rodents on the seeds of three species of winter annual plants that grow in the Sonoran Desert. While the preference for one species is much higher than the other two, preferences for each species are higher when common than when rare showing an asymmetric form of positive FDP. This study is the first empirical test for positive FDP on winter annual plants and by granivorous desert rodents and one of few to use more than two prey species, native prey species, or asymmetrically preferred prey species.