No description available.

No description available.

Many of the world's tropical forests are under threat, with anthropogenic deforestation and degradation occurring at an alarming rate. Seed dispersal in an important process in forest restoration and regeneration, however seed rain is often low in degraded habitats, hindering reforestation efforts. Up to 90% of tropical fruit are dispersed by vertebrates, animal seed dispersers are incredibly important in maintaining forest health. Additionally, frugivores that disperse seeds into degraded areas may be of great importance in aiding natural reforestation. I therefore, investigated the potential role of the frugivorous monkey, Chlorocebus tantalus tantalus, in forest regeneration via seed dispersal. I assessed its patterns of habitat use, the quality and quantity of seed dispersal it provides, the effectiveness of current conservation management actions and the density of C. t. tantalus at Ngel Nyaki Forest Reserve. I found C. t. tantalus utilised forest, edge and grassland habitats, and dispersed seeds of 28 pioneer and forest edge species into these habitats. Moreover, the number of seeds dispersed per faeces was significantly higher in the grassland than the forest with means of 16.4 +/- 6.1 and 3.4 +/- 0.97 seeds >2 mm in these habitats respectively. Germination of C. t. tantalus dispersed seeds was highest in grazed grassland and lowest in grassland protected from grazing and fire, suggesting the current practice of fencing off grassland to protect from cattle grazing may not be sufficient on its own, due to seed-seedling conflict in habitat suitability. These findings combined with an estimated density of 28 +/- 10.8 C. t. tantalus individuals km⁻² suggests C. t. tantalus may benefit forest regeneration via its role as a seed disperser, provided appropriate management actions are implemented. This and other frugivorous species may play similar roles in other locations but such roles need to be investigated in order to implement management actions that ensure their seed dispersal benefits are maximised for forest restoration and regeneration.

Seed dispersal in aquatic habitats is often considered to be a complex multistage process, where initial seed shadows are redistributed by water (hydrochory). The roles of hydrochory in seed dispersal and influencing population genetic structure were examined in Helmholtzia glaberrima using both ecological and genetic techniques. Ecological experiments showed that water can redistribute seeds and seedlings over local scales and that hydrochory can provide the potential for very long distance seed and seedling dispersal. Patterns of seedling genetic structure were affected by micro-drainages that direct water flow within populations and influence water-borne seed dispersal on a local scale. Strong non-equilibrium dynamics and persistent founder effects were responsible for the patterns of genetic structure observed among established populations of H. glaberrima. Classical metapopulation models best described dispersal patterns, while water-borne seed dispersal could potentially explain patterns of genetic differentiation within a stream system, it could not explain the distribution of genetic variation among stream systems. The current study found that although hydrochory influenced seed dispersal and seedling genetic structure within a population, it had little effect on the spatial pattern of genetic variation among established populations of H. glaberrima. Moreover, even though prolonged buoyancy and viability in water provide the potential for long-distance hydrochory, results presented here do not support the hypothesis that flowing water is an effective long distance seed dispersal vector for H. glaberrima. Taken together, these results suggest that the relative importance of gene flow via water-born seed dispersal in H. glaberrima may be low compared with that of some other riparian species.

The rate of global urbanization is increasing at an alarming pace, as the human population has grown to over 7 billion people—from 1.6 billion people in the 1900s—, half of which reside in urban areas. This increase has necessitated the expansion of urban habitat and increased consumption of natural resources. While the effects of urbanization on species diversity is well-documented (increasing urbanization decreases species diversity), its effects on species interactions have been less studied. Plant-animal interactions, such as seed dispersal, may be especially sensitive to urbanization. For plants, animal-based seed dispersal depends on several aspects, including 1) the rate of interactions with seed dispersers, 2) the probability of seed dispersal from an interaction event, 3) the identity and the number of seed disperser species –especially regarding differential ability to scarify seeds through digestion, and 4) the probability of germination after seed dispersal. Urbanization may affect seed dispersal dynamics by altering the frequency of interactions and/or the identity and diversity of seed dispersers. Consequently, the probability of seed dispersal and the ability of seeds to germinate and survive after being dispersed may be negatively affected by urbanization. In this study we ask specifically: 1) Will birds visit T. radicans at a greater rate in urban or natural habitats? 2) Will the diversity of dispersers be higher in urban or natural habitats? 3) Do seeds from urban or natural sites have a greater probability of dispersal? 4) Will seeds from urban or natural habitat be more likely to germinate? To compare differences in rate of visitation and disperser diversity between urban and natural habitats, individual T. radicans plants in two urban and two natural sites were observed for interactions by birds. Dispersal probability was estimated by marking fruits with a UV fluorescent dye and estimating a proportion of dispersed seeds at the end of the season. Seeds dispersed = total fruits marked – number of recovered fruits. Germination success will be estimated by collecting defecated—thus scarified—seeds in natural and urban sites as well as collecting non-dispersed seeds (that will be treated with either water or sulfuric acid). Seeds will be cold stratified 90 days before planting in constant 28oC and 16:8 L:D conditions. Preliminary results indicate that the rate of visitation, species diversity, and probability of seed dispersal are all significantly higher in urban sites. This trend suggests that T. radicans in urban habitat may be more successful than in natural habitat, however further research is necessary to confirm this.

Anthropogenic habitat disturbance is the leading cause of global biodiversity decline. Urbanization in particular is one of the most drastic forms of habitat disturbance, and it is associated with a decrease in both plant and animal diversity. Changes in biodiversity can affect the interactions between the remaining species within an ecosystem, which can, in turn, affect the provision of essential ecosystem services such as seed dispersal and pollination. Despite the wealth of studies examining the effects of urbanization on biodiversity, however, relatively few studies have investigated how urbanization impacts the interactions between species and the ecosystem services provided by them. Seed dispersal is one such ecosystem service which provides an ideal study system for investigating these effects. The goal of this study was to assess the impact of urbanization on avian seed dispersal networks in southern Appalachia. Specifically, we investigated the impact on species richness, interaction richness, and several network metrics related to ecosystem function (H2, interaction evenness, and weighted nestedness). The study was conducted across two fall – winter observation periods to coincide with the period of peak fruit production, from September – January in 2021-2022 and 2022-2023. Data was collected from 9 study sites during multiple visits via direct observation of bird-fruit interactions, with a total of 635 interactions recorded from 32 bird species on 18 fruiting plant species. Although data analysis is currently ongoing, initial results seem to indicate that there is no significant difference in species richness or interaction richness between natural and urban sites. This has interesting implications, as it suggests that plant-frugivore networks are relatively robust to disturbance caused by urbanization, which is promising for the continued provision of ecosystem services in urban areas.

No description available.

This study investigated primary seed dispersal of !nara (Acanthosicyos horridus) by Blackbacked Jackals (Canis mesomelas) and secondary seed dispersal by scatter-hoarding hairyfooted gerbils (Gerbilliscus (Gerbillurus) spp.) in the central Namib Desert. This was accomplished by examining visitation rates and fruit removal of !nara melons, primarily by jackals. In addition, I determined the viability and germination rate of !nara seeds collected from jackal scat. The results indicate that jackals were the dominant species to visit !nara (93.3%) and the only !nara frugivores recorded by camera traps over two !nara fruiting seasons. There was no difference in the viability of ingested seeds and control seeds, but germination rates of ingested !nara seeds were significantly higher (50.4%) than control !nara seeds (34%). This component of the study suggests that Black-backed Jackals are the main primary dispersers of !nara seeds in the central Namib Desert. I furthermore examined secondary seed dispersal by tracking !nara seeds to determine whether scatter-hoarding hairyfooted gerbils were caching or consuming seeds. I recorded the distance moved, depth of seed burial, recovery rate and the habitats in which seeds were buried in three habitat types. Hairyfooted gerbils removed 100% !nara seeds from experimental sites and cached 60.3 % of all the !nara seeds removed. The gerbils frequently retrieved the buried caches within two days (77% of the time) and re-cached them elsewhere. The majority of caches were in the open areas (83%) and only consisted of one (39%) or two seeds (45%). Only 1.7% of the cached seeds were not retrieved by the gerbils during the 30-day observation periods. !Nara seeds were moved an average distance of 29.1±1.6 m and buried at an average depth of 4±0.2 cm. Although there is high probability of cache retrieval, some of the cached seeds survived. As gerbil caches are at favourable locations for plant establishment, and as it is more likely that buried seeds will survive until suitable conditions for germination and seedling establishment, seed dispersal by hairy-footed gerbils is advantageous to !nara plants. Therefore, hairy-footed gerbil species in the central Namib Desert contributed to secondary seed dispersal of !nara. The combined interaction of endozoochory by Black-backed Jackals (Canis mesomelas) and synzoochory by hairy-footed gerbils (Gerbillurus spp.) in dispersing seeds of !nara plants (Acanthosicyos horridus) in the central Namib Desert suggest diplochory is highly likely.

Gopher tortoises (Gopherus polyphemus) are keystone species mainly due to their burrow construction. Gopher tortoises can also impact the plants around them, but it is rarely quantifiable due to constraints in dispersal studies including time period and seasonality of fruit. The objective of this study was to measure the effect gut-passage has on a native Florida stone-pitted shrub, the cocoplum bush (Chrysobalanus icaco), as well as to attempt to model the relationship between the gopher tortoise and the plant using our unique field site. This study shows that gut-passage has a significant effect on the germination rate of the cocoplum, allowing it to germinate faster than control groups. This study also found that a model involving covariates relating to tortoise movement as a predictor for cocoplum intensity was favored over a homogeneous null model. We believe the pattern of plants is nonrandom and relates to the gopher tortoise’s seed dispersal. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

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.