2004 Program
(Student name highlighted)
Land Use History Affects the Distribution of the Saprophytic Orchid Wullschlaegelia calcarata in Puerto Rico
Erin Bergman and James Ackerman
Manchester College
University of Puerto Rico, Rio Piedras campus
Human activities such as industrialization, agriculture, logging or urbanization, can have severe consequences on forest ecosystems. We wanted to determine the forests’ ability to recover biodiversity after logging and agriculture sixty years prior. To investigate recovery after anthropogenic alteration we studied spatial distribution of an understory saprophytic orchid, Wullschlaegelia calcarata in the Luquillo Forest Dynamics Plot (LFDP), a 16-ha plot of land located in the Luquillo Experimental Forest, Puerto Rico. The LFDP contains areas with different land use history, which is still apparent in present day tree species distribution. We recorded orchids in six 10 m wide, 500 m long transects across the LFDP that crossed four different land use areas termed as cover classes. We found that the orchid was not present in cover class 1 which was denuded of trees 60 years prior and was most abundant in cover class 4, which was minimally impacted by human disturbance. Since tree species composition varied among land use history types, we assessed leaf litter biomass and composition and found that orchids occurred more frequently in leaf litter composed primarily of Buchanavia tetraphylla and Dacryodes excelsa leaves. Forest development since human disturbance ceased have not masked the effects of historical land use in this tropical forest, and past land use has had an influence on orchid distribution. The least disturbed parts of the forest are acting as a reservoir for Wullschlaegelia calcarata and perhaps other species.
Drift patterns of shrimp and insect larvae in streams with contrasting fish assemblages
Rahiza De Thomas and Jorge Ortiz
Universidad del Turabo
University of Puerto Rico, Rio Piedras campus
Stream organisms are often transported downstream in the water column in substantial numbers. Larvae of amphidromous shrimps are released by females in streams and drift passively to estuaries, where they metamorphose before migrating back upstream. Among insect groups, many Ephemeroptera and Diptera are common components of drift. In this study we sampled drifting organisms for abundance, composition, and periodicity in two streams with contrasting fish assemblages located in the Luquillo Experimental Forest. Quebrada Prieta has a high shrimp abundance and Quebrada Bisley has a low abundance due to the presence of predaceous fish. Both streams were sampled using two different methods: drift nets and automatic ISCO samplers. Our hypothesis was that there will be a strong periodicity in Bisley, where benthic predators (i.e., shrimp) are more active during the night to avoid diurnal fish predators. In contrast, Prieta should have less periodicity because it lacks shrimp predators, and shrimp are active day and night.
Flow Regime and Riparian Vegetation in the Luquillo Mountains of Puerto Rico
Emmanuelle Humblet and Fred Scatena
University of Pennsylvania
Riparian zones are the interface between aquatic and terrestrial ecosystems, and thus present diverse, dynamic and complex biophysical processes. The occurrence of riparian vegetation depends on many factors, including light conditions, substrate and edaphic conditions, and the frequency of flooding. This study is focused on developing techniques to quantify relationship between stream flow and vegetation and investigates how the frequency of flooding is related to the type of riparian vegetation in the high gradient, tropical streams of the Luquillo Mountains, Puerto Rico. Our hypothesis was that different flood frequencies promote different vegetation types. Vegetation of the riparian zone was divided into 4 categories: moss, herbaceous, shrubby, and tree. The levels for each of these vegetation life forms were surveyed from transects at 6 USGS stream gauges. Two methods to calculate discharge were used and compared: Manning’s and a stage-discharge regression. The frequency of flooding for each vegetation level was then calculated by fitting USGS historical data distributed to a log-Pearson Type III distribution. Distinct vegetation levels were found where the heights of each followed the trend of trees > shrubs > herbaceous > moss. The average return periods for herbaceous, shrub, and tree vegetation was 2 months, 5.5 months, and 22 years, respectively.
Xiphocaris elongata and leaf litter decomposition in a tropical island stream system
Christine Mingione and Todd Crowl
University of Notre Dame
Utah State University
A major source of energy inputs into freshwater streams is comprised of allochthonous organic matter from riparian vegetation. This is especially important in the tropics where litter inputs are continuous and driven by disturbance. This study looked at the freshwater shrimp, Xiphocaris elongata, and its role in processing different species and types of leaves common to the Luquillo Experimental Forest in northeastern Puerto Rico. Consumption rates of fresh green leaves and senesced brown leaves of five native species and one exotic species of different successional stages were compared in laboratory feeding experiments. In addition, leaves of two species (Piper glaberescens and Cecropia schreberiana) with and without herbivory were compared a second experiment. With the exception of Dacryodes excelsa and Cecropia schreberiana, shrimp did not significantly increase breakdown rate of green leaves relative to microbial controls but did for brown leaves. Equal processing rates were seen for green and brown leaves of all species except for D. excelsa and C. schreberiana, which showed significantly faster consumption rates for green leaves. Green and brown leaves of the non-native Spathodea campanulata were processed faster than all the other species. No difference was seen in processing rates for leaves with and without herbivory for both P. glaberescens and C. schreberiana. Overall, I conclude that shrimp consume leaves containing the most value for them nutritionally and not necessarily because of successional stage, defensive chemicals or leaf toughness.
The fungus-growing ant Cyphomyrmex minutus: impact of a parasitoid wasp on colony demography and behavior
Angel Perez and Jess Zimmerman
University of Puerto Rico
While dipteran parasitoids of leaf cutting ants have been well described, wasp parasitoids have never been found in leaf-cutting ants or their tribe, the Attini. This study describes for the first time a wasp parasitoid (Betula sp.) of an attine ant, Cyphomyrmex minutus. We determined levels of larval parasitism in four sites in northeastern Puerto Rico, finding that about 53.19% of colonies were parasitized with no significant difference in % parasitism among sites. Comparing parasitized and unparasitized colonies, we found no significant difference in colony size, however, there was some indication, using regression analysis, that parasitoids were selecting colonies with high rates of larval production. Experimental studies showed that while C. minutis readily distinguished nest mates from conspecific non-nest mates and workers of Wasmania auropuntata, they were often unable to detect the presence of the parasitoid in the colony. Thus, in contrast to some bird species where parasite recognition is an important defense, these attine ants do appear able to behaviorally defend themselves from parasitism.
What are the Ephemeroptera using as substrate to feed on in the rivers in El Yunque?
Karina Robles and Alonso Ramirez
University of Puerto Rico, Humacao
University of Puerto Rico, Rio Piedras
Our study determined the substrate type used by Ephemeroptera (mayfly) larvae in the rivers in El Yunque Rainforest. We used leaves, sediment, rocks and wood as substrates and compared the biomass increase in mayfly larvae in each of these substrates. Ten replicates were made for each treatment. We estimated growth by obtaining the mean change in biomass during a 7-day period. Growth rate means in the treatments increased in the following order: Sediment, rock, non-colonized leaves, wood debris and colonized leaves. The Tukey-Kramer HSD test showed that growth rates in the colonized leaves were significantly higher from all the other treatments. Our study indicates that growth rates on sediments were also significantly different from wood debris. Ephemeroptera larvae in the river can be affected by different factors like predators (e.g. shrimp, crabs, other invertebrates), river floods, adults mating and breeding success, anthropogenic disturbance and river contamination. Nevertheless, this experiment helps us predict the effects it could have in the mayfly populations the alteration of the river habitat and food availability.
Marine Freshwater Linkages: Importance of Larval and Post-larval Freshwater Shrimp in the Diet of Fish in Two Tropical Estuaries
Zoe Rodriguez, Katherine Smith and Catherine Pringle
University of New Orleans
University of Georgia
[Abstract missing]
The Effect of Decomposer Functional Groups on Decomposition Rates
Michael Strickland and Paul Klawinski
William Jewell College
[Abstract missing]
Effects of freshwater shrimp on the life history of mayflies (Ephemeroptera) in Luquillo Experimental Forest Streams
Ceidy Torres and Alonso Ramirez
University of Puerto Rico, Ponce
University of Puerto Rico, Rio Piedras
[New abstract here]
This study identifies the life history of mayflies in the presence and absent of shrimp. The study sites were Prieta and Bisley streams in Luquillo Experimental Forest. These streams differ in their shrimp density; Prieta has higher density than Bisley. The shrimp species Atya lanipes decreases sediment accumulation in the stream bottom while foraging, thus creating better habitats for mayfly grazing. Bisley stream has low densities of shrimp therefore the sediment is accumulated in the bottom. The objective for this study was to determine if shrimp enhance food resource availably for Ephemeroptera larvae and determine how larvae respond to those resources. We expected mayfly larvae and adults to reach largest body sizes in streams with high shrimp density (e.g., due to high food resources). We measured chlorophyll concentrations in both streams. In the presence of shrimp there was more chlorophyll due to the reduced sediment cover. Mayfly growth rates were also measured on both streams. Growth rates were higher in Prieta, potentially due to high amounts of algae. Finally, adult mayfly were found to be ...
Reproductive effort and distribution in different soil type for Wullschlaegelia calcarata Benth (Orchidaceae)
Christian Torres and James Ackerman
University of Puerto Rico, Mayaguez
University of Puerto Rico, Rio Piedras
Los tipos de suelos no tienen efecto directo en la distribución de la orquídea terrestre Wullschlaegelia calacarata. Tiene un crecimiento limitado porque necesita un hongo endomycorriza al que parasita en el suelo y hojarasca. Su distribución es bastante frecuente para 3 de 5 tipos de suelos que ocurren en las montañas de Luquillo pero es más abundante en los suelos Zarzal que constituyen 67.3% de las LFDP Parcelas Dinámicas del Bosque de Luquillo (LFPD). La altura de la orquídea predice el número de flores y frutas de W. Calcarata. El esfuerzo reproductivo de W. calcarata se afecta significativamente con los tipos de suelos. El tipo suelo Zarzal tiene un contenido de materia orgánica de 16.8% y la alta humedad que se crea en las montañas de Luquillo le implanta un ambiente favorable para descomposición de materia orgánica por los hongos que saprofito que W. calcarata parasita. Este hongo pertenece al género de Rhizoctonia solani. El tipo de suelo Zarzal afecta el esfuerzo reproductivo de la planta significativamente.