UCB Moorea Class: Biology and Geomorphology of Tropical Islands

The River Continuum Concept (RCC) predicts that as the form of particulate organic matter available in streams and rivers varies longitudinally, so will the functional feeding groups (FFGs) of benthic macroinvertebrates. The RCC was developed based on data from continental streams; therefore, its applicability to the unique ecology of island streams is virtually untested. The purpose of this study was to discover if the RCC works in the small streams of Moorea, French Polynesia. Three sites along an elevational gradient were sampled for benthic macroinvertebrates in five streams of similar catchment size. Each sample was sorted and all taxa were assigned to a FFG. Species richness and FFG variation along a longitudinal gradient were compared to RCC predictions. Patterns in the longitudinal variation of crustacean/mollusc species richness and shredder, grazer, and predator percent composition were found to match RCC predictions. However, total species richness, insect species richness, and the percent composition of collecting organisms did not. Therefore, an alternative theoretical framework is needed to accurately describe FFG variation in tropical streams.

Tahitian legend states Fagraea berteriana is a gift of repentance from the god, Tane. The scientific community knows little more about this tree than its inter-island distribution in the South Pacific. I surveyed the island of Moorea to map an intra-island distribution of F. berteriana and quantify environmental characteristics surrounding the tree’s growth. I tested dispersal hypotheses by collecting bird observations and conducting seed germination experiments that included a numer of seed scarification treatments. The tree occurred in densities ranging from 44 to 244 trees/hectare and at elevations spanning from approximately 300 to 900 m. Density differed with significance between two sites, Tohiea and the Cross Island Trail. Tree density increased with greater elevations and more southerly aspects. Ninety-five percent of the trees sampled grew on slopes greater than 80%. There was no correlation between tree density and slope or between density and tree height. Tree density did not significantly differ between three substrate types: rock, rocky soil, and soil. I observed Silvereyes and Red-vented bulbuls consuming F. berteriana fruits and germination from seeds, although at a less than 1% rate. The germination success and bird observations served as a preliminary investigation of the dispersal of F. berteriana and fostered ideas concerning worthwhile future directions of study.

Previous studies of the feeding biology of Culcita novaeguineae Muller & Troschel in Hawai’i have shown that the cushion star prefers to prey on coral species of the genus Pocillopora over the genus Porites. Distribution and feeding biology studies of C. novaeguineae in Cook’s Bay on the island of Mo’orea, French Polynesia have shown that it habitats near Porites spp. coral in areas where Porites spp. coral is sparse, and prefers to prey on Acropora spp. coral. The purpose of this study was to further examine coral prey preference of C. novaeguineae in Mo’orea, using specimens from four areas on the island for better representation of its feeding ecology on Mo’orea, French Polynesia. My studies showed that C. novaeguineae in Mo’orea prefers Acropora spp. and Pocillopora spp., over Porites spp. (p=0.0046), and showed no preference for Acropora spp., over Pocillopora spp.. The study further determined that C. novaeguineae primarily feeds nocturnally, and moves persistently in search for food. As a coral predator, C. novaeguineae can affect abundance of certain coral species, and change the overall reef ecology in Mo’orea.

While water striders (Hemiptera: Gerridae) have a global distribution different species have adapted to very different habitat types. Freshwater water striders such as Limnogonus luctuosus live in areas along streams and rivers with little to no flow. Marine water striders, such as coastal species Halobates hawaiiensis, have adapted to life on the surface of the ocean. Since these types of water striders live in such different habitats, and face different environmental factors their food preference and behavior can be quite different. In this study, average density of L. luctuosus individuals was measured along the Opunohu River. Also, food preference, behavior, and the effects of increased density were tested in the laboratory for both L. luctuosus and H. hawaiiensis. Response time and frequency of approach to mobile and immobile prey items were recorded for H. hawaiiensis and L. luctuosus. H. hawaiiensis preferred immobile prey while L. luctuosus preferred mobile prey. Frequency of several behaviors (i.e. movements, moving away from others, approached by others, approaching others, attacking, being attacked, jumping, and cleaning) were compared between species, and within species at increasing densities. There were differences between species in the frequency of movements, approaching others, being approached, jumping, and cleaning. Density affected movements, moving away from others, jumping, and cleaning for H. hawaiiensis. Density affected movements, moving away from others, and cleaning behaviors for L. luctuosus. The different ecology of these two species can be used to explain why differences exist in both food preference and frequencyof behaviors.

Octopuses are known for the advanced behaviors and elaborate displays used in predator avoidance. Although studies have provided anecdotal evidence on the defense mechanisms of these animals, whether these behaviors vary under light and dark conditions is unknown. This study investigated the diurnal and nocturnal predator defense mechanism s of Octopus bocki (Adams, 1941) in Moorea, French Polynesia. Seven behaviors were identified as primary defense mechanisms for protection from fish predators during daylight and nighttime hours. Rates of occurrence and durations for defense behaviors significantly differed between diurnal and nocturnal conditions, as O. bocki frequently Crawled during the daylight hours , but sat still and Curled during the nighttime hours. Results indicate that O. bocki modifies predator defense behaviors for survival under light and dark conditions.

Environmental variables change over elevational gradients and can isolate plant populations. Three varieties of Hibiscus tiliaceus L. exist on an elevational gradient in Moorea, French Polynesia. These variety’s morphological and chemical characteristics are associated with the differences between their environments. Leaf and flower morphological data were collected and analyzed and found significant differences in petal width and length, anther count, burgundy center color, and leaf width and length between the varieties, particularly between the coastal and mountain types. The increased rainfall and lower temperatures of the high mountains lowered net primary production for the mountain variety as compared to the coastal and mid-mountain varieties. The mid-mountain variety was found to have greater competition for light than the other varieties. These can be linked to the significant size differences in leaves and inflorescence. Chemical differences were analyzed using anti-microbial and anti-cancer bioscreens. Significant differences were found in the anti-microbial bioscreen between the mid-mountain variety, which showed little activity, and both the coastal and mountain varieties. The anti-cancer screen showed increased activity from the coastal and mountain leaves. Chemical differences are influenced by increased insolation and chemical protection from microbes in wet conditions. Anthropological uses of the varieties are linked to the greater size of the coastal type. The plant populations studied are associated with the differences in their environments.

Environmental Science Policy and Management, University of California, Berkeley, California 94720 USA Abstract. Interspecific mutualisms between ant and scale insect species have been well documented as symbiotic relationships that merit resource acquisition in exchange for protection. In this study, insect removal experiments were preformed on the branches of Psidium guajava in order to measure the effects that insect populations have on one another. Five ant removal, five scale removal and five control trees were treated. Data was taken daily over the course of 18 days. Ant activity was measured using a one-minute, unidirectional, point count and the number of scales per branch was determined by photographing a sample of five leaves per branch. Wilcoxon rank-sum tests found that ant populations differ significantly to that of controls in the absence of scale insects. Scale insect populations were not significantly affected by the removal of ants. Observational ant behavior data was also collected that supports possible tending behavior.

Shorebirds often feed in multispecies groups that display interesting niche dynamics. On Moorea, French Polynesia, the Wandering Tattler (Tringa incana) and Pacific Golden Plover (Pluvialis fulva) are the dominant shorebird species during the northern winter. These species’ feeding behavior was observed at the Temae estuary on the northeast side of the island. Relative abundance of the two species was determined using transect counts at the estuary and an adjacent beach. T. incana displayed more striking and sprinting behavior, while P. fulva displayed more picking and walking behavior. T. incana also consumed more crabs than P. fulva. The two species existed in relatively equal abundance in the estuary; T. incana was more common on the beach. Though these data suggest some differences in feeding niche, a great deal of overlap was observed. The degree of niche partitioning appears to be greater in this study than in similar studies conducted on these species’ breeding grounds.

Epiphytes are important in forest ecosystems because they contribute to species diversity and aid in nutrient cycling. Despite this, the ecology of tropical epiphytes, particularly nonvascular species, is not well understood. This study compared epiphyte richness, cover, diversity, and species distributions to host tree diameter, canopy cover, aspect, and height on the trunk. Thirty-two Metrosideros collina trees were sampled for epiphyte species every 0.5 centimeters along circumferential transects at 0, 0.75, and 1.5 meters off the ground. Host tree diameter at 0.5 meters was measured, as well as canopy cover at North, South, East, and West. Epiphyte cover was lowest at the bottom of the trunk and highest at 1.5 meters. Richness correlated positively with diameter and canopy cover, but it did not vary significantly with height or aspect, according to the Wilcoxon and Tukey tests. Epiphyte cover correlated positively with canopy cover, but it did not vary significantly with diameter or aspect. Moss and fern cover increased significantly with diameter but did not vary with height. Liverwort and lichen cover were not correlated with diameter, but they were lowest at the bottom of the trunk and highest at 1.5 meters. Diversity, calculated with the Shannon-Wiener index, correlated positively with epiphyte cover and tree diameter but did not vary significantly with height. Overall, epiphytes preferred habitats in the upper trunk region on trees with high canopy cover, and their distributions were correlated with every variable except aspect.

The various predator defense mechanisms possessed by shallow water sea cucumbers were surveyed in twelve different species and morphs. While many defense mechanisms such as the presence of Cuverian tubules, toxic secretions, and unpalatability have been identified in holothurians, I hypothesized that the possession of these traits as well as the degree to which they are utilized varies from species to species. The observed defense mechanisms were compared against a previously-derived phylogeny of the sea cucumbers of Moorea. Furthermore, I hypothesized that while the presence of such structures is most likely a result of the species’ placement on a phylogenetic tree, the degree to which they utilize such structures and their physical behavior are influenced by their individual ecologies. The presence of a red liquid secretion was restricted to individuals of the genus Holothuria (Linnaeus 1767) however not all members of the genus exhibited this trait. With the exception of H. leucospilota, which possessed both Cuverian tubules and a red secretion, Cuverian tubules were observed in members of the genus Bohadschia (Ostergren 1896). In accordance with the hypothesis, both the phylogenetics and individual ecology appear to influence predator defense mechanisms. However, even closely related species of similar ecology may differ considerably.