2001 Program
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The Abundance and Distribution of Amblypygids in the Luquillo Experimental Forest
Lee Cohnstaedt and Paul Klawinski
The physical and physiological restraints imposed upon an organism by abiotic factors limit that organism’s abundance, distribution and corresponding role in a food web. We identified the important abiotic factor (habitat structure) that limits the distribution of the amblypygid, Phrynus longipes one of the top predators in the Luquillo Experimental Forest. We also examined behavioral and morphological traits of this little studied species using a mark and recapture program. We were able to predict instar age and territorial area using the animal size and we observed some very unique behaviors, not previously reported about amblypygids.
Consistency among Primers Pairs in Amplified Fragment Length Polymorphisms
Barbara Rodríguez and Raymond Tremblay
AFLP’s are quickly becoming the tool of choice for many applications and organism. AFLP (amplified fragment length polymorphism) technique is one of a number of DNA fingerprinting procedures that takes advantages of the polymerase chain reaction to amplify a limited set of DNA fragments from a specific DNA sample. This technique is important and useful because it can be applied to a wide variety of organism. In a comparison of genetic variation among plants cultivars detected by RFLPs, AFLPs, SSRs and RAPDs, AFLP were found to give the highest diversity of polymorphism. This research attempt to establish which AFLP primer pairs are consistent and provide the optimize results in the hermaphroditic orchid Lepanthes rupestris.
Morphological Variation in Deceptive and Rewarding Flowers
David Hof and James D. Ackerman
Self-fertilization in plants can incur great fitness costs, and consequently a vast array of mechanisms has evolved in order to assure cross-pollination. Most commonly, animals are used as vectors to transfer pollen among individuals of a given species. Pollinator visitations do not come without a cost, and plants usually offer a reward. However, the flowers of some plant species offer no reward and deceive animals into visiting their flowers. Many studies have reported high levels variation within deceptive species, and suggest variation is maintained by frequency-dependent selection due to pollinator learning. However, no studies have compared the level of variation in deceptive species with rewarding species. In this study, we tested the hypothesis that morphological variation in pollinator attraction traits is greater in deceptive species than in rewarding species. We measured key floral components of available deceptive and rewarding species in Puerto Rico. A comparison of coefficients of variation indicated that deceptive species did show higher variation than rewarding species. However, the mechanism maintaining high variation in deceptive species remains unresolved.
Correlation between plant litter decomposition and earthworm abundance in a tropical wet forest
Jennifer Dechaine, Xiaoming Zou, Yaniria Sanchez, and Hong-Hua Ruan
Earthworms play an important role in influencing decomposition rates in tropical rain forests. In order to better understand this role, we examined the abundance and biomasses of earthworms as correlated to decomposition rates in riparian and upland zones of the forest. We attempted to answer the question of earthworms directly influencing decomposition rates vs. decomposition rates predicting the abundance and biomass of earthworms. We collected earthworms from sites in upland and riparian zones of the forest and 0-0.1m and 0.1-.25m depths. Earthworms were handsorted and weighed both fresh and dry. We found that earthworm abundance positively correlates with decomposition of local leaves in the upper 0.1m of the soil profile, earthworms are more abundant and have higher biomasses in the upland zone of the forest and the upper 0.1m of the soil, and ground litter removal has no effect on abundance and biomasses of earthworms. Our results when compared to similar studies done with earthworm removal suggest that earthworms more likely affect decomposition rates instead of decomposition rates affecting the abundance and biomasses of earthworms. They also suggest earthworms are influenced by variations in microclimate, plant community, and biotic activity between the two zones of the forest.
Association between species composition and environmental variables of Lepanthes along an elevational gradient in the Luquillo Experimental Forest
Jessica K. Schwarz and Dr. Elvia Meléndez-Ackerman
Patterns of dispersion together with apparent low levels of gene flow suggest that genetic drift may have been an important evolutionary force leading to population differentiation in Lepanthes within the island of Puerto Rico. An alternative but not mutually exclusive explanation is that habitat specialization is related to differentiation in Lepanthes. To test this hypothesis we studied the distribution of Lepanthes species along the elevational gradient of two streams within the Luquillo Mountains in Puerto Rico. We also measure environmental variables such as relative humidity and temperature to test whether or not elevational changes in these variables were associated with changes in relative species composition and diversity along the gradient. Our results indicated that elevation was not a good predictor of relative species composition or diversity and that composition and diversity was heterogeneous between streams. Minimum temperature was negatively associated with elevation on both streams, but the relationship between species composition, diversity, or dominance with elevation was not apparent. Except for the rare species in the dwarf forest our results do not support the hypothesis of habitat specialization at the landscape level, but specialization and the microhabitat levels can not be discarded.
Liana density and load at Luquillo Experimental Forest
Katherine Rice, Nicholas Brokaw and Jill Thompson
We recorded the density of lianas ≥ 1 cm dbh and the liana occupancy of trees ≥ 10 cm dbh in 8000 m2 of the Luquillo Experimental Forest, Puerto Rico. We found an average of 40.0 lianas per 0.1 ha and 26% of the trees supported lianas. These numbers are among the lowest reported from tropical forests. More disturbed plots had an average of 26.0 lianas per 0.1 ha, while the less disturbed plots averaged 54.0 lianas per 0.1 ha. Canopy occupancy varied among tree species and increased with tree size. Individual tree species did not vary in their canopy occupancy between more and less disturbed plots.
Living with the enemy: insect distribution among habitats in shrimp dominated streams
Luz Raquel Hernández Cruz and Alonso Ramírez
In this study we assessed the abundance and composition of aquatic insects in different stream habitats and the effects of macroconsumer predation on benthic insects in streams draining the Luquillo Experimental Forest. Two second-order streams, Prieta and Bisley, were used as study sites for their similarities in habitat composition, and contrasting amounts of macroconsumers. In both streams, insects were collected from different benthic habitats and the presence of macroconsumers was manipulated. Results provided information on the impact of macroconsumers on the density and composition of benthic insects. Insect assemblages in the study streams recognize two main habitats, rocks and riffle/pools. Low insect abundance in pools and riffles is a potentially the result of macroconsumers predation and competition.
Long-lasting sprouting in a subtropical wet Forest in the Luquillo Mountains of Puerto Rico
Marisa Santiago and Denny Fernández
Trees have evolved many responses to different kinds of damage or stress, promoting forest regeneration after disturbance. Forest trees may respond to damage or senecence either by producing new individuals (seedlings) or by sprouting from dormant buds below or above ground. Sprouting from dormant buds is an efficient mechanism for persistence in some forests after disturbances. This has now been shown to be an important mechanism for persistence in some forests after disturbances. The purpose of this study was to determine the contribution that sprounts make to regeneration dynamics of the forest and what are the factors that contribute to the production and establishment of these sprouts in damaged trees. Damaged and fallen trees inside ten 20x50 m transects were measured for the following variables: DBH, condition of the tree after disturbance and type of damage. Categorization of the sprouts was done measuring the DBH (10 cm from base), and sprout condition according to the leaves density and presence of roots. Manilkara bidentata, Guarea guidonea, Sloanea berteriana and Dypetes glauca showed that sprouting was an important mechanism involved in their regerneration process (13.79%). There were no significant correlations between amount and condition of sprouts and variables related to the physiological and physical characteristics of trees.