Factors Promoting Coexistence between Endemic Ants and Invasive Wasps

<p>Invasive animals can alter the community composition of native ecosystems by means of competition and predation. In this study I investigated the factors that may facilitate coexistence between endemic ants and invasive wasps. Previous research has shown that entire communities can be impacted by invasions. Endemic species subject to pressure from invasive species may undergo a niche shift to enable coexistence and minimise the impact of this pressure. The invertebrate community composition of Nothofagus forests in the South Island of New Zealand has been altered by predation from Invasive Vespula wasps. Ants and wasps in this ecosystem coexist on the same trophic level; they simultaneously fill multiple trophic roles as primary predators, secondary predators, and primary consumers. The outcome of competition between species such as ants and wasps is not easy to predict, and may vary in different communities and with different densities of competitors. In this dissertation I aimed to determine the extent to which competition occurs between native ants and invasive Vespula wasps, and to investigate the impacts of invasion on the native invertebrate community. I quantified the invertebrate community composition of Nothofagus forests and then experimentally reduced wasp numbers to investigate any changes as a result of a reduction in predation or competition. The observed changes in community composition were as a result of differing abundances of taxonomic groups within my study sites. In order to more robustly determine the community effects of wasp removal it may be necessary to reduce wasp numbers by up to 90% for many years. Even under these conditions, species that are particularly vulnerable to wasp predation or competition may have already been permanently excluded from this system. I then investigated temporal niche shifts by native ants when faced with reduced competition for food resources from invasive wasps. There was an increase in the numbers of ants foraging on honeydew when I experimentally reduced wasp numbers. This increase may be due to increases in both the quantity and quality of the available honeydew. When densities of wasps were substantially reduced there was a difference in the foraging abundances of ants and wasps; however, there was no change in the overall temporal foraging pattern of ants. Isotope ratios and consequently trophic levels of native competitors may change in response to the removal of an invasive species. To test this I examined changes in isotope ratios as a result of removal of wasps. The observed changes in the trophic levels of both ants and wasps appear to be a result of natural seasonal variation in consumption related to the nutritional requirements of the colony. Finally, I examined behavioral interactions between native ants and invasive wasps during foraging. This study has indicated that wasps may find and access resources more readily when ants are present. Native ants may facilitate foraging by wasps, as demonstrated by the increase in wasp numbers when foraging in the presence of ants. Additionally, the impact of competition between wasps and ants is likely to be density dependant. Co-occurrence between endemic and invasive competitors is possible through two important mechanisms, niche separation and behavioural adaptations. Native ants in this system are able to forage in different temporal niches than invasive wasps, and their dominant behaviour serves to diminish competitive interactions. These findings have implications for the ecology of these forests in understanding the considerable impact that invasive species may have on native ecosystems and particularly those species which have similar resource requirements.</p>

Factors Promoting Coexistence between Endemic Ants and Invasive Wasps

<p>Invasive animals can alter the community composition of native ecosystems by means of competition and predation. In this study I investigated the factors that may facilitate coexistence between endemic ants and invasive wasps. Previous research has shown that entire communities can be impacted by invasions. Endemic species subject to pressure from invasive species may undergo a niche shift to enable coexistence and minimise the impact of this pressure. The invertebrate community composition of Nothofagus forests in the South Island of New Zealand has been altered by predation from Invasive Vespula wasps. Ants and wasps in this ecosystem coexist on the same trophic level; they simultaneously fill multiple trophic roles as primary predators, secondary predators, and primary consumers. The outcome of competition between species such as ants and wasps is not easy to predict, and may vary in different communities and with different densities of competitors. In this dissertation I aimed to determine the extent to which competition occurs between native ants and invasive Vespula wasps, and to investigate the impacts of invasion on the native invertebrate community. I quantified the invertebrate community composition of Nothofagus forests and then experimentally reduced wasp numbers to investigate any changes as a result of a reduction in predation or competition. The observed changes in community composition were as a result of differing abundances of taxonomic groups within my study sites. In order to more robustly determine the community effects of wasp removal it may be necessary to reduce wasp numbers by up to 90% for many years. Even under these conditions, species that are particularly vulnerable to wasp predation or competition may have already been permanently excluded from this system. I then investigated temporal niche shifts by native ants when faced with reduced competition for food resources from invasive wasps. There was an increase in the numbers of ants foraging on honeydew when I experimentally reduced wasp numbers. This increase may be due to increases in both the quantity and quality of the available honeydew. When densities of wasps were substantially reduced there was a difference in the foraging abundances of ants and wasps; however, there was no change in the overall temporal foraging pattern of ants. Isotope ratios and consequently trophic levels of native competitors may change in response to the removal of an invasive species. To test this I examined changes in isotope ratios as a result of removal of wasps. The observed changes in the trophic levels of both ants and wasps appear to be a result of natural seasonal variation in consumption related to the nutritional requirements of the colony. Finally, I examined behavioral interactions between native ants and invasive wasps during foraging. This study has indicated that wasps may find and access resources more readily when ants are present. Native ants may facilitate foraging by wasps, as demonstrated by the increase in wasp numbers when foraging in the presence of ants. Additionally, the impact of competition between wasps and ants is likely to be density dependant. Co-occurrence between endemic and invasive competitors is possible through two important mechanisms, niche separation and behavioural adaptations. Native ants in this system are able to forage in different temporal niches than invasive wasps, and their dominant behaviour serves to diminish competitive interactions. These findings have implications for the ecology of these forests in understanding the considerable impact that invasive species may have on native ecosystems and particularly those species which have similar resource requirements.</p>

Foraging Behaviour of Heterotrigona itama (Apidae: Meliponini) in Residential Areas

This study aims to investigate the foraging behaviour of Heterotrigona itama in exploiting food resources at a residential area, and the viability of this species to adapt to urban microclimatic conditions. Heterotrigona itama prefers to forage at areas closer to their nesting site, where diverse food sources are found. The marked bees of H. itama prefer to forage on various resources available at a 500-metre radius from the house yard. The obtained results indicate that the active foraging pattern of H. itama is negatively correlated to the time phases of a day (p < 0.05). This phenomenon was contributed by the three peaks of foraging hours, which reached a peak in the early morning (6:30 to 8:00 a.m.), moderately peaked towards the evening (2:30 to 3:30 p.m.), and was greatest towards the afternoon (10:30 a.m. to 12:00 p.m.). The ambient temperature and relative humidity were not the primary factors influencing the average number of foragers exiting from and returning to the hives (temperature, p > 0.05; and humidity, p > 0.05). There was a difference between the varieties of content resources collected by the bees (p < 0.05). The nectar or water sources was the highest material (51.39%) that was brought back to the hive by foragers, followed by resin (34.73%) and pollen (13.87%). There was a significant difference in foraging time phases by returning foragers for collecting resin (p < 0.05) and nectar or water (p < 0.02), but there was no significant difference in foraging time phases found for pollen (p > 0.05). We concluded from the results that H. itama is able to withstand urban microclimate conditions, and successfully incorporated pollen, nectar or water, and resin obtained from floral and non-floral resources into their diet.

Risk-sensitive foraging strategy of flower visitors in Serjania caracasana

Production of nectar can play a fundamental role in the foraging behaviour of floral visitors through its availability and distribution. The aim of this study was to understand the foraging pattern of floral visitors in Serjania caracasana. The field study observed the strategy of nectar production and the foraging behaviour of the floral visitors of Serjania caracasana, carried out through an experiment that evaluated the amount of nectar produced by flowers, species richness and frequency of visits. The data analysis showed that there is no significant correlation between any of the variables analysed. The unstable nectar between the flowers and the unpredictability during the hours of the day suggest a risk-foraging strategy of risk-prone type of the species of floral visitors. The data from this study suggests that Serjania caracasana has potential to understand the theory of risk-sensitive foraging in relation to its reproductive success.

Seasonal variation in the foraging activity of desert argali (Ovis ammon) in Mongolia

Debate remains whether energy maximization or time minimization strategies best explain foraging in ungulates. It has also been hypothesized that the capacity of an animal to dissipate body heat regulates animal activity. We investigated these hypotheses while measuring the daily activity of desert argali (Ovis ammon (Linnaeus,1758)) for 12 months and relating the activity pattern to environmental seasonality. We found significant seasonal cycles in argali activity, with the greatest proportion of daytime in winter spent foraging and the greatest proportion of daytime in summer spent bedding. Consistent with an energy maximization strategy, argali reduced all behaviors during the winter in favor of foraging, compensating for the increased energy demands of winter at a time of low forage quality. Consistent with a time minimization strategy, argali in summer significantly reduced foraging and spent more time bedding in shaded areas to avoid hyperthermia due to high ambient temperatures. Both optimal foraging and heat dissipation can be used to explain the observed foraging pattern. Foraging behavior in argali is best described by the extent to which the animals schedule their activities to meet their physiological demands, the way these demands are affected by environmental variables, and the time that is available to accomplish them.

Feeding ecology of the marsupial Thylamys macrurus (Olfers 1818) (Mammalia, Didelphidae) in woodland patches of Cerrado, central-western Brazil

Knowledge about the feeding ecology of didelphid marsupials remains incipient, especially in environments with marked seasonality in resource supply, such as in the Cerrado. We analysed the diet composition of Thylamys macrurus in Cerrado patches in central-western Brazil. We also evaluated seasonal and sexual variation in the species’ diet, as well as if the accumulation of fat in the tail shows a seasonal pattern. We obtained 87 captures of 68 T. macrurus specimens and 29 faecal samples. Six categories of food items (Hymenoptera, Isoptera, Coleoptera, Arachnida, Blattodea and seeds) were identified. Arthropods were recorded in all samples and seeds in 10.3%. The species showed seasonal variation in diet, consuming primarily of arthropods throughout the year but incorporating a higher proportion of fruits during the wet season. Males and females also differed in diet composition; males consumed a wider range of items in the dry season. Although more detailed analyses are still needed to better understand the T. macrurus food consumption pattern, our results indicate a possible relationship between dietary variation and local availability of resources, suggesting an opportunistic foraging pattern. The accumulation of fat in the tail also presents a seasonal pattern, with a larger tail diameter in the dry season.

Apis mellifera pollen loads to understand the pollen foraging pattern used for apicultural practice in a potentially agricultural belt in Bengal, India

For accurate determination of polleniferous taxa vis-a-vis floral fidelity of Apis mellifera L. in North 24 Pargana, West Bengal, we carried out pollen analyses of individual corbicular pollen loads collected from four apiaries during 2015-2016. Among the 2 434 analyzed loads, 72.97 % were unifloral type, 19.0 % bifloral and 8.10 % were multifloral in pollen composition. We identified 43 different types of palynomorphs belonged to 28 botanical families. Major polleniferous plant species include: Alangium salviifolium, Borassus flabellifer, Brassica nigra, Coriandrum sativum, Croton bonplandianum, Cyanotis axillaris, Luffa cylindrica, Neolamarckia cadamba, Phoenix sylvestris, Poa gangetica, Sesamum indicum and Trema orientalis. Among them, T. orientalis is newly reported from West Bengal especially during June to August (monsoon season). The plant family provided maximum number of loads was Arecaceae (20.91 %), followed by Brassicaceae (16.2 %), Poaceae (6.70 %), Pedaliaceae (6.38 %), Apiaceae (6.16 %) and Fabaceae (5.38 %). Month wise highest number of pollen diversity were obtained during March (13 pollen types) and a minimum of 6 types in November. The present investigation will help the beekeepers to maintain their hives in the region for sustainable apicultural practices.

Food Reward and Distance Influence the Foraging Pattern of Stingless Bee, Heterotrigona itama

Beekeeping with stingless bee provides new opportunities to improve the incomes of many households in Malaysia through the sale of honey and other bee products. While Heterotrigona itama is one of the most commonly cultured species of stingless bees, its behavior is not very well understood. Hence, we conducted this study to investigate the behavior of H. itama in exploiting food sources by ascertaining the nectar sugar concentration preferred by the bee. We also aimed to determine the preferred distance of food source from the beehive. Our results suggest that H. itama prefers high sugar concentrations of 35% and above, and most of the bees preferred to forage close to their hive to collect food. We discuss how nectar concentration, food distance, and abiotic factors influence the number of bees exploiting food sources and the overall foraging pattern of H. itama.