2007 Program
(Student name highlighted)
Preliminary assessment of bee abundance and species diversity in different forest and coastal habitats in Puerto Rico
Lourdes Carballo Crespo and Jose Fumero
Universidad de Puerto Rico, Mayaguez
Universidad de Puerto Rico, Rio Piedras
The pollination of plants mediated by animals is a critical ecosystem service as most flowering plants need the service of pollinators for sexual reproduction. Among the different pollinator types bees are often the most important pollinators because their life cycle is closely related to plants. Our main goal was to study the abundance and species diversity of bees with emphasis on solitary bee species in the coast and rain forest by habitat. Data were collected using visual census and this data were combined with active hand netting and passive using pan trapping methods. The chosen habitats were The Luquillo experimental Forest at El Verde Field Station including the canopy level, undesrtory with close and open canopy, forest edge and the riparian zone. In the coastal site at Piñones, we gathered information of two kinds of habitats: close to the sea shore with less vegetation and away from the shore were is more vegetation. We found 6 native species and observed more abundance of species at the forest edge in El Verde than any other site. Piñones did not have many bee individuals as we expected. The exotic Honeybees were presents in the two study sites. Environmental factors such as maximum wind speed were negatively correlated with the number of bees for one study site. We found no relationship between the number of flowers and the number of bee individual per site. More data on the abundance and diversity of bees is needed to get a better picture of the local bee fauna.
Hydrological significance of moss lines in montane streams of the Luquillo Experimental Forest
Christina Catanese and Fred Scatena
University of Pennsylvania
This project seeks to address the question of whether microhabitat features can be linked to larger ecological and hydrological conditions, particularly moss lines in montane streams of the Luquillo Experimental Forest, Puerto Rico. Using ecological features as indicators of flow levels is potentially useful in managing water withdrawls, as well as indicating the impacts of disturbances, particularly at streams that do not have extensive or frequent monitoring and measurement. We hypothesized and found that the occurrence of moss lines are correlated with chronic environmental conditions reflecting streamflow, rather than short term pulses showing the scour line of the most recent storm. Moss lines at the study sites did not show significant growth, shrinkage, or erosion during the study period, indicating their stability as channel indicators. Through systematic field studies of various streams in the LEF, the key variables for moss line formation were identified: stable boulder substrate and channel morphology in a moist sheltered or protected environment with a low percentage of incident light. Moss levels were also related to long-term flow records to associate them with a particular flow frequency. On average, the moss levels occur at Q95 frequencies, indicating that only the largest 5% of stream flows actually cover the mosses. These channel indicators of the high flow level of a stream are potentially useful in water management practices, giving insight into the local conditions of a channel, an extremely useful tool in assessing ungaged streams without a long-term hydrological record of stream flow.
The distribution of the invasive, terrestrial orchid, Oeceoclades maculata: Does land use history, soil or slope of the terrain matter?
Ian M. Cohen and Jim Ackerman
University of Tennessee, Chattanooga
Universidad de Puerto Rico, Rio Piedras
Oeceoclades maculata is a rapidly spreading invasive species originating from the tropical regions of Africa. Discovered in 1829 in Brazil, O. maculata has managed to colonize a large portion of the Neotropics from Florida (U.S.A.), throughout the Caribbean, and large portions of Central and South America. We conducted Six 10 x 500 m south to north running transects in June 2007 on the 16-ha Luquillo Forest Dynamic Plot (LFDP), located in the Luquillo Experimental Forest (LEF) in Puerto Rico, to determine if prior land use history had an affect on its distribution and abundance. We also surveyed two native orchids, Wullschlaegelia calcarata and Prescottia stachyodes, to compare their distributions and abundance to O. maculata and for use in future studies, and we also looked at the affects of soil and slope on its distribution. Oeceoclades maculata was the most abundant of the three orchids surveyed, and it was found in all four cover classes. It was most abundant in Cover Class 3 (50-80% forest cover in 1936) where 192 of 343 plants were found with a mean of 0.48 plants/ 5 x 5 m subplot. The distributions of both native orchids were negatively correlated with the distribution of O. macualta, which may be a sign that it is out competing both native orchids. Over 93% of the 1200 subplots surveyed were composed of Zarzal or Cristal soil types, and O. maculata was nearly evenly distributed in both. The results for slope showed that it clearly preferred flat terrain which is no surprise since it has a short root stock. The distribution of O. macualata throughout Puerto Rico shows the high invasibility of tropical islands and that prior land use has made the understory of both secondary forests and old growth forest prime targets for invasion.
Palatability of leaf litter conditioned by white-rot vs. non-white-rot fungi to leaf shredders in a freshwater stream
Michelle De Jesús and Jean Lodge
Universidad de Puerto Rico, Humacao
US Forest Service
Freshwater stream invertebrates that consume leaf litter (i.e., litter shredders) often prefer leaves that have been previously conditioned (colonized and partly decomposed) by fungi and other microorganisms. This study differed from previous research on litter shredders in streams by addressing possible differences in palatability between leaves conditioned by white-rot vs. other types of rot. White-rot fungi soften litter by degrading lignin, and concentrate nutrients. We used both an in situ trial in the Quebrada Buruquena and a microcosm experiment using a shrimp, Xiphocaris elongata to determine through paired trials whether conditioning by white- vs. non-white-rot influences palatability of leaf litter to stream invertebrates. We compared leaf area and mass loss of leaf discs of two leaf species (high lignin – Inga vera; lower lignin – Manilkara bidentata) conditioned either by a white-rot basidiomycete, Collybia johnstonii vs. paired discs cut from the same leaves with non-white-rot organisms that are exposed to leaf shredders. Using paired t-tests, both percent mass loss and percent leaf area loss were greater in white- than in brown-rot in the microcosms. In the stream, however, only mass loss was significantly faster in the white-rot treatment in I. vera. The preference of litter shredders for leaves conditioned by white-rot, especially leaves with high lignin, was consistent with our main hypothesis. Thus, the preferences in the stream were apparently based on an interaction of the type of rot (white- versus a mixture of non-white-rots) with leaf species, and may also reflect responses from mixtures of leaf shredders with differing preferences.
Who eats more in tropical streams: shrimp or insects?
Nelmarie Landrau Giovannetti and Alonso Ramirez
Universidad de Puerto Rico, Humacao
Universidad de Puerto Rico, Rio Piedras
Consumers play an important role decomposing leaf litter in streams. However, we know little about their individual roles. Our objectives for this research were to determine the role of macro invertebrates (shrimp and insects) in the process of leaf decay and to determine whether the availability of nutrients affects the role that biota plays in the process of leaves decomposition. The hypotheses for this research were: (1) nutrients accelerate leaf breakdown and lead to high rates of decomposition when macro invertebrates are also present; (2) shrimp will have a higher rate of decomposition than insects. The study was conducted in an artificial stream facility for three weeks and applying the following treatments: nutrients and leaves with shrimp (Xiphocaris) and no nutrients with leaves and shrimp (Xiphocaris); nutrients and leaves with aquatic insect (Ephemeroptera) and no nutrients with leaves and aquatic insect (Ephemeroptera) and the controls were leaves with nutrients and only leaves without nutrients. The leaves used were Cecropia, which were pre-conditioned for different amounts of time before starting the treatments. We measured leaf weight changes for each treatment. Leaves exposed to shrimps with and without nutrients had the highest effects on leaf weight change by day. Mayfly effects were larger than shrimp effects for both nutrient treatments by biomass of organism.
Land Use and Elevation Effects on Spider Species Composition in the Luquillo Mountains, Puerto Rico
Mackenzie Malloch and Paul Klawinski
Western Washington University
William Jewell College
We examined spider community composition of four elevationally distributed old growth forest types, and two abandoned pastures in the Luquillo Mountains, Puerto Rico. Data for the four undisturbed sites was collected from 1999-2007. The abandoned pastures and an additional old growth site were added to the survey in 2007. We identified the collected spiders then analyzed the data using non-metric multidimensional scaling. We found that spider species richness was not necessarily higher in old growth Tabonuco forests in comparison to abandoned pastures. In addition, we found that both pastures were more similar one another than to any other forest. The pastures were also more similar to the lowest elevation undisturbed forest than that forest was to a higher elevation forest of the same type (tabonuco), It is likely that both elevation and land use history play a role in determining spider community structure however data from a broader range of ages of abandoned pastures will probably be necessary fully examine the relative importance of these two driver of community structure.
Earthworm abundance and species composition: comparison of teak plantations (Tectona grandis) and secondary forests in Puerto Rico
Esther Morales Vega and Grizelle Gonzalez
Universidad de Puerto Rico, Humacao
IITF
Earthworms are the most important soil macrofauna in tropical ecosystems because they are involved in the regulation of soil process. The purpose of this study is to compare the patterns of earthworm abundance (density and fresh weight) and species composition in teak plantations with the naturally regenerated secondary forest in Puerto Rico. The hypotheses of this study was: (1) There are higher density and biomass of earthworms will be found in the secondary forest than in the teak plantations; (2) Native earthworms will be most abundant in the secondary forest than in the teak plantations; (3) Exotic earthworms will be most abundant in the teak plantations than in the secondary forest; specifically, we expect the exotic earthworm Pontoscolex corethurus will be most abundant in the teak plantations; (4) In teak plantations, we expect to find more endogeic earthworms than epigeic or anecic earthworms; (5) In the secondary forest, we expect to find the three ecological classes of earthworms: endogeic, anecic and epigeic. We founded the highest density and biomass of earthworms in secondary forest than in teaks plantations. The exotic earthworm is the most abundance in teak plantation and secondary forest. The highest density of native earthworms was in teaks plantations than in secondary forest. Meanwhile, the highest density of exotic earthworms was in secondary forest than in teaks plantations. We founded only two of the ecological classification of earthworm in teak plantation and secondary forest: endogeic and anecic earthworm. In secondary forest we founded the highest abundance endogeic earthworm. Meanwhile, the highest abundance of anecic earthworm was founded in teak plantation.
Abundance and diversity of hummingbird flower mites in Heliconia caribaea
Ivette Peterson and Elvia Melendez-Ackerman and Ariel Diaz
Universidad de Puerto Rico, Humacao
The genus Heliconia includes many species that are abundant in subtropical and tropical zones (Maas and Westra, 1993). They are commercially distributed as ornamental plants because of their colorful and distinct inflorescence. These plants are closely associated with hummingbirds for their reproduction. Hummingbirds can offer the plant pollination services, but they could also bring some other effects like pathogens, no to useful or beneficial to the plant, or flower mites (Lara & Ornelas 2002). Flower mites affect the plant by eating its nectar and its pollen also (Colwell 1973, 1979, Dobkin 1984, 1985, 1987, Heyman et al 199, Naskrecki & Colwell 1998, Lara & Ornelas 2002). There is one endemic species of Heliconia in Puerto Rico, Heliconia caribaea. Although we may assume that Puerto Rican endemic Heliconia will show the presence of flower mites (Carolyn Cabrera unpublished), the phenomenon has not been completely studied on the island. I continued previous work attempting to identify the mites and their population dynamics on the island. Four patches of Heliconia caribea were marked at the Luquillo Experimental Forest and visited intensively during four weeks. New flowers were collected daily and preserved in 70% ethanol. Flowers were examined for the presence of flower mites and mites found were collected and mounted on slides. A total of 36 samples were collected and a total of 180 flower mites were identified by sex and life stage. Regression analysis was used to analyze the pooled data of season 1(summer 2006) and season 2 (summer 2007). We found that the number of flower mites is independent of the number of inflorescence within a patch, the number of bracts within an inflorescence and the number of flowers by bract. The abundance of flower mites does not change in a significant way in time.