Monteverde Institute: Tropical Ecology and Conservation

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  A comparison of moth diversity and abundance along an altitudinal gradient in Monteverde, Costa Rica, August 2004

  Katie Swartz

  Costa Rica has high moth (Lepidoptera) diversity, with relatively little known about its distribution (Hanson 2000). Insects tend to decrease in richness and abundance along an altitudinal gradient (Brehm and Fiedler 2003). Lepidopterans are important indicators of environmental health, important herbivores, vital prey species, and a large draw for the country’s main source of income, ecotourists. The purpose of this study was to compare moth diversity and abundance at varying altitudes. Moths were trapped using an ultra violet light and a sheet at three different altitudes (1530 m, 1639 m, and 1759 m) over six nights between July 26th and August 2nd, 2004, in the forest behind the Estación Biológica, Monteverde, Costa Rica. One hundred and seventy-one moths were caught, representing 76 morphospecies. The lowest elevation had the greatest species diversity as well as the greatest total number of moths (H’=1.553, 69 moths), followed by the highest elevation (H’=1.528, 67 moths). Both the lowest diversity (H’=1.318) and the lowest number of moth individuals (35 moths) were collected at the middle elevation. The diversity was significantly different between the lowest and the middle elevation (t=3.91, p=< 0.002) and between the middle and the highest elevation (t=3.33, p= < 0.002) and was not significantly different between the lowest and highest elevation. The largest amount of species overlap was found between the lowest and the middle elevations (J= 0.60). The study did not support the hypothesis that there would be less diversity and abundance of moths as elevation increased. It does, however, seem to indicate that there is a difference in the species found at each elevation. Additionally, the study seems to indicate that there were factors at the middle elevation that reduced the moth abundance and diversity relative to the highest and lowest elevations. Further studies are necessary to determine whether or not the distribution trends observed are specific to the sites, time of year, or sampling nights during this study.

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  Aggressive behavior of hummingbirds and their response to nectar concentrations, August 2004

  Emily Matheson

  As pollinators of many flowers in Costa Rica, the foraging behavior of hummingbirds has been studied many times in the past. The Monteverde area hosts many different hummingbird species all throughout the year. Over time, as the landscape changes and flower abundance fluctuates, it is necessary to study their competitive interactions as well as their abilities to respond to these changes. This particular study quantified aggressiveness in four hummingbird species at feeders in Monteverde. Response to a change in nectar concentration (30% to 10%) was also quantified and then compared between each species (Lampornis calolaema, Eupherusa eximia, Campylopterus hemilecurus, and Heliodoxa jacula). The purpose of this study was to determine if a positive relationship existed between hummingbird aggressiveness and response to nectar concentration. A chi-squared test determined which species were aggressively dominant over other species. Lampornis calolaema showed dominance over C. hemilecurus and H. jacula. Eupherusa eximia showed dominance only over L. calolaema. Simple regression lines were plotted with the number of visits over time by each species to the two nectar concentrations. The slopes of these lines were then compared to determine if certain species were more responsive than others to changes in nectar concentrations. Results showed that the more aggressive species were not more responsive to change.

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  A lesson on symbiotic interactions for the Centro de Educación Creativa, August 2004

  Melissa Reimer

  Symbiotic interactions represent the complexity of the functions of tropical ecosystems. Many of these symbiotic interactions are found in the cloud forest. In order to educate students about the importance of these interactions, research was conducted on symbiotic interactions found in the Monteverde area and a lesson plan was created. This lesson plan was created for Centro de Educación Creativa (C.E.C.) a private school in Monteverde, intended for integration into the 6th grade theme four titled “Ecosystem and Relationships in Nature.” It consists of a three-day series of lessons addressing the symbiotic interactions that occur in the cloud forest, including two PowerPoint presentations and various activities for the students. I expect that this lesson plan will help educate the students of C.E.C. about their own surrounding area and promote preservation of the cloud forest.

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  Ant (Formicidae) diversity, species richness, and abundance in response to different food sources, August 2004

  Sarah A. Wyatt

  More than 500 species of ants (family Formicidae: order Hymenoptera) have been found in Costa Rica (Gauld & Hanson 2000), and 46 of the 80 genera found in Costa Rica are known to live in the Monteverde area (Longino 2000). Some species of ants are known to exhibit food preferences for or against sugar and/or specific prey taxa (Dejean et al. 1999). The purpose of this study was to determine if species richness and diversity change in response to varying bait in traps. One hundred and twenty traps containing one of 6 kinds of bait (crustaceans, tuna, honey, peanut butter, and tuna/honey and peanut butter/honey mixtures) were left on the ground near the trails in the Bajo del Tigre area, Monteverde, Costa Rica. Captured ants were identified to morphospecies and their abundance was recorded for each trap. Crustacean bait attracted the greatest diversity of species (Shannon Weiner diversity index: H’ = 0.74) and tuna and peanut butter baits attracted the lowest diversity (Shannon Weiner diversity index: H’ = 0.33, 0.31). Peanut butter/honey bait attracted significantly more individuals than crustaceans, honey, tuna and tuna/honey (Fisher’s PLSD, P = 0.0010, 0.0009, 0.0360, 0.0037, respectively). This study demonstrated that there are significant differences in both the diversity and number of ants trapped when using different kinds of bait, and that researchers should be selective in choosing the bait that best suits the purpose of their study.

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  Bromeliad arthropod diversity in a regenerating pasture adjacent to a tropical montane forest, Costa Rica, August 2004

  Ann Willow Jorgenson

  Tank bromeliads (Bromeliaceae, Vriesea sp.) harbor diverse faunal communities. A total of 426 arthropods assigned to 62 different morphospecies were collected and identified to taxonomic order. The composition of bromeliad arthropod fauna was investigated in an open pasture to see whether arthropod diversity or richness correlated with distance from the forest edge. Neither arthropod richness nor diversity was found to significantly correlate with distance from the forest edge. These results are discussed in relation to island biogeography theory and the ecological implications of arthropod diversity are considered.

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  Changes in saprophytic fungal community structure in response to variations in moisture content, August 2004

  Jessica Gellings

  This study examined community structure of fungal species on dead wood substrates of different moisture contents in Monteverde, Puntarenas, Costa Rica. Forty-five different samples of dead wood substrate were located in the cloud forest and sampled for abundance of fungi individuals and number of fungal morphospecies. Penetrability as a measure of moisture content, surface area, and percent of epiphytic and lichen cover were also recorded for each sample of dead wood substrate. A total of 42 morphospecies were found, with only three of them overlapping between hard and soft substrates. Significant negative correlations were found between penetrability and abundance of fungi individuals (r2= .251, p = .0005), as well as between penetrability and fungal diversity (r2= .217, p = .0013). The negative correlations suggest that there is a moisture barrier-a certain substrate saturation- beyond which fungal growth is restricted. The low rate of species overlap between hard and soft substrates indicates that there is a difference in community structure depending on moisture content.

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  Dung beetle response in relationship to manure location, August 2004

  Margaret Quinn

  Dung beetle ecology is an integral part of nutrient cycling within ecosystems around the world. Farms benefit from the decomposer action of dung beetles from the nutrients imputed into the soil and the breakdown of helminthes parasites. This study analyzed the effects of varying dung location within pastures on dung beetle response. It was hypothesized that cow manure closer to forest edges would elicit a greater response than manure located further away. Also, manure located near an edge would elicit a greater beetle response overall when compared to manure in the middle of the pasture. Three pastures located in San Luis, Monteverde, Costa Rica were analyzed for beetle response. Two grid plots containing 30 2 X 2 meter squares were set up in each pasture, a corner plot and a middle plot, with eight-ounces of cow manure sample placed in each 2 X 2 square. An additional plot was set up in the forest. Using a simple linear regression it was found that the number of beetles did not correlate with distance from the forest. There were significantly less beetles located in 6-meters to 8-meters (ANOVA, p=0.005) and at 10-meters to 12-meters (ANOVA, p=0.004) groupings from the forest edge than in the woods. There were also significantly more beetles in the corner plots than in the middle plots (ANOVA, p = 0.0002). From these results, farms may be able to increase the amounts of beetles on their farms utilizing smaller fields with increased bordering forest, aiding in nutrient cycling and reduction of helminthes health risks.

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  Effect of Ficus tuerckheimii diameter, host tree presence, habitat and orientation on epiphyte diversity and abundance, August 2004

  Christina Tierno

  Ficus tuerckheimii, a species of strangler fig found in the cloud forests of Monteverde, is a keystone species for a multitude of animals as well as epiphytic plants. In the study, epiphyte richness on Ficus tuerckheimii was analyzed in order to determine if epiphyte species richness was related to elevation, circumference, hollowness, location, percent of area covered by epiphytes and compass point orientation. Thirty Ficus tuerckheimii were studied in pasture and forest areas between 1400-1500 m elevations. A significant relationship was found between epiphyte species richness in forest habitats versus open (Mann Whitney U=28, P=.0083). Significance was also found between species richness and percent area covered (P=.01). More species richness was found on hollow Ficus tuerckheimii, but was not proven significant. These findings suggest that conservation efforts to preserve older forested land may be most important for preserving epiphyte species richness as well as organism diversity associated with these trees.

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  Fruit species preference in mountain robins (Turdus plebejus), August 2004

  Leah Bomberger

  The Mountain Robin (Turdus plebejus, Turdidae) (in the Monteverde region in Costa Rica) is an opportunistic feeder and an important disperser for many plant species. This study examined fruit preference of the Mountain Robin between three species of plants: Viburnum costaricanum, Chamaedorea costaricana, and Chamaedorea pinnatifrons. A significant preference was found for C. costaricana over C. pinnatifrons (P = 0.040). These results indicate that C. costaricana offers a higher reward and may attract more dispersers than C. pinnatifrons or V. costaricana.

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  Nocturnal vs. diurnal insect diversity within tropical montane forest canopy, August 2004

  Michael Rosenthal

  Tropical forest canopies are unique environments with complex interactions, allowing for high levels of specialization for insects. The purpose of this study was to test whether increased specialization has created differences in species richness and diversity between nocturnal and diurnal canopy insects. To test this, insects were collected from six trees using suspended traps containing three types of bait (carrion, rotten fruit, and specific scents that attract euglossine bees). Diversity and species richness was quantified for diurnal and nocturnal traps of all three baits and for total number of insects collected diurnally and nocturnally. The results showed that on all accounts there was a significant difference in species richness and diversity for diurnal traps (H’ = 1.000) and nocturnal traps (H’ = 0.863) (P = 0.005).

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  Observational analysis of insect diversity, richness, and abundance on the fungus, Auricularia delicata (Basiodiomycata), August 2004

  Megan Scott

  Fungi are important to ecosystems because of their ability to release nutrients back into the environment and their relationships with insects. This study determined the diversity and richness of insects attracted to Auricularia delicata and related it to external conditions. Eleven colonies of Auricularia delicata were located near the Estación Biológica de Monteverde and observed to determine the morphospecies and abundance of insects present. The results illustrated that insect abundance significantly increased with species diversity (RS = 0.778, P = 0.0001.) Insect abundance significantly increased with colony surface area (RS = 0.659, P = 0.0371) and number of fruiting bodies present in a colony (RS = 0.487, P = 0.0171). Morphospecies richness significantly increased with surface area (RS= 0.693, P=0.0284), and with insect density (RS = 0.802, P < 0.0001). Diversity was compared to surface area and total number of fruiting bodies but was not found to be significant affected by either. This study indicates that important interactions take place between insects and Auricularia delicata.

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  Response to changes in location of nectar source by Xylophanes acrus (Sphyngidae) as a measure of “spatial memory”, August 2004

  James T. Murphy

  Moths in the family Sphyngidae are known to expend a considerable amount of energy in locating food resources. Considering the high investment of energy required to locate food resources within large areas, a valuable adaptation to aid in more efficiently locating resources might be the ability to “remember” resource locations in order to relocate them when necessary. The purpose of this study was to determine how Xylophanes acrus would respond to sensory cues and if these responses indicated an ability to develop a “spatial memory” for locations of nectar sources. Xylophanes acrus responses to artificial nectar sources were elicited using a natural flower attractant with an artificial nectar source attached. The presence of “spatial memory” was tested by manipulating the location of an artificial nectar source and recording visitation patterns of X. acrus within enclosures. The results indicated that X. acrus did show an ability to “remember” the location of nectar sources, as a significantly greater number of X. acrus individuals visited locations where nectar was located previously compared to new nectar sources in adjacent locations (P = 0.012). It would be highly adaptive if X. acrus could use this ability in a natural setting to more efficiently locate resources over large areas, thereby conserving energy that would otherwise be spent if relying solely on visual or olfactory sensory stimuli detection to relocate resources.

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  The effectiveness of the mountain robin (Turdus plebejus) as a seed disperser in the Monteverde area, August 2004

  Sean Brady

  Quantitative and qualitative factors are important in determining the effectiveness with which bird species disperse seeds. This study examined several factors that may influence the quantitative component of dispersal in the mountain robin. Regurgitation times of three common fruits in the area were examined. Additionally, the size at which seeds transition from being regurgitated to defecated was studied. Results show that regurgitation times between these three fruits do not differ significantly. However, there was a significant difference in the size of regurgitated (X = 5.97 mm ± 2.17 mm) and defecated seeds (X = 4.25 mm ± 2.55 mm) (t = -17.192, P < 0. 0001). This information may be important in determining the way in which seeds of different sizes are dispersed. Furthermore, if combined with future field studies documenting number of visits made to a fruiting tree and length of each visit, insight will be gained regarding the effectiveness of the mountain robin as a seed disperser.

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  The effect of abiotic factors on the distribution of Cerrorchestia hyloraina (Taltridae) above and below the Monteverde Cheese Factory, August 2004

  Vanessa Cervantes

  Taltrid amphipods are terrestrial crustaceans known to favor moist habitats and feed off of decaying matter. They have been found infesting caves, beaches, and garden leaf litter. Within the past three years, the Cerrorchestia hyloraina (Crustacea: Amphipoda: Taltridae) population local to the Monteverde area has exploded due to changes in unknown biotic and/or abiotic factors. Three abiotic factors (distance from river, soil moisture, and temperature) were tested at two different sites: one above and one below the Monteverde Cheese Factory (MCF). Taltrid density was significantly higher below (251.800 ± 170.811 taltrids/trap) the MCF than above (1.619 ± 1.910 taltrids/trap, Mann-Whitney U = 420.0, P < 0.0001) and soil moisture was the best predictor of taltrid density (Simple regression, R2= 0.158, P = 0.0102). Soil temperature was also a significant indicator of taltrid density (Simple regression, R2= 0.113, P = 0.0316), and distance from river showed no significant correlation with taltrid density, supporting that C. hyloraina is not water dependent. While abiotic factors are strong determinants of where C. hyloraina live, it may also be changes in the local environment resulting from unknown biotic interactions that may explain the recent highly localized proliferation of this species.

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  The effects of elevation on epiphyte richness and density on cloud forest tree ferns (Cyatheaceae and Dicksoniaceae), August 2004

  Chad Taylor

  Epiphytes play an integral role in nutrient cycling in tropical rainforests and are often found on the trunks of tree ferns. This study examined the role of elevation on epiphyte load on tree ferns. Ninety-six tree ferns were examined along an elevational gradient, and data were collected regarding the identity and dimensions of the trees as well as their elevations and the number and type of epiphytes on their trunks. Epiphyte abundance was not significantly correlated with elevation, but epiphyte load was significantly related to tree fern morphology. The Alsophila, whose spines likely provide a prime habitat for epiphytes, possessed a significantly larger epiphyte load than Cyathea, which does not possess spines (P = 0.0062). Further study regarding tree fern morphologies and epiphyte load should be conducted.

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  The effects of predator presence on nectarivorous bat foraging behavior, August 2004

  Rachael Heuer

  For many species, predator avoidance changes normal foraging behavior, altering optimal foraging strategies. In this study, foraging behavior of bats was examined by observing the number of feeding visits to control feeders in comparison to feeders with an artificial snake or owl in close proximity. Trials were also performed between snake and owl treatments to determine if one predator was more strongly avoided during feeding. Nectarivorous bats were found to exhibit predator avoidance behaviors for both snake and owl predators (P < 0.0001, P < 0.0001). There was no significant difference in trials comparing owl and snake avoidance, suggesting that bats do not fear one more than the other (P = 0.947). This study shows that predator presence must be taken into account along with search time, handling time, and caloric reward when evaluating optimal foraging models with necatarivorous bats.

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  An introductory lesson plan to the flora and fauna of the Monteverde Cloud Forest, December 2003

  Amanda Rocklet

  The result of this project is a mini-course lesson plan which can be used at the Cloud Forest School-Centro de Educación Creativa (C.E.C,). The mini course lesson plan will be used in seventh and eighth grade classes to teach the local taxa of Monteverde. Enclosed are six Power Point presentations, six interactive activity plans, six field guides, and a list of teacher resources. I expect this mini course to reinforce the C.E.C.'s environmental education curriculum while also taking into account teacher turnover and lack of resources.

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  A survey of the herpetofauna of the San Luis valley, Costa Rica, in three microhabitats, December 2003

  John Benjamin

  I surveyed reptile and amphibian diversity in three types of microhabitats in the San Luis valley, Puntarenas, Costa Rica, an area whose herpetofauna has not yet been thoroughly inventoried. I sampled species richness and abundance using nine line transects of 150 m in length around the Ecolodge and Biological Station San Luis, located all 1150 m in elevation. Three transects were in riparian habitat,three were in forest habitat, and three were in pasture habitat. I found 14 species within the transect areas, and a total of 23 species in San Luis including specimens that were encountered outside the transects. Some of these species (Bolitoglossa robusta, Sphenomporhus cherriei and Leptodiera annulata) were notable since they are not listed as being common in the Tropical Premontane Moist Forest life zone. No statistically significant difference in diversity was found between the habitats when their H' values were compared with a t-test, which was likely due to the small sample size and limited time frame of the study. However, H', S, and Smarg were all found to increase from pasture to riparian to forest microhabitat, revealing a general trend of highest diversity in the forest and lowest diversity in the pasture. Species composition similarity was found to be relatively high between the forest and rivers, moderate between the rivers and pasture, and low between the forest and pasture.

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  Contagion of mistletoe in a tropical Psidium guayaba pasture, December 2003

  Amish Patel

  Mistletoe is a plant parasite that is unusual in having a specialized dispersal mutualism. The behavior of its avian dispersers assures deposition on tree branches of its preferred hosts. In returning to the same plant, however, such behavior may cause centers of ever-increasing density, akin to contagion in other host-parasite systems. The purpose of this study was to determine if mistletoe species Antidaphne viscoidea or Phoradendron undulatum demonstrate contagious dispersion of their seeds. The study was conducted in a pasture of Psidium guayaba trees on a farm near Monteverde, Costa Rica. In each of 20 trees, I counted the number of fruiting individuals, non-fruiting individuals, seedlings, and defecated seeds of both species of mistletoe. Running simple regressions found positive correlations between the number of seeds and the number of fruiting individuals of P. undulatum (p<0.0001.) Similarly, there was a positive correlation between the numbers of adult individuals and seedlings for A. viscoidea (p=0.0003.) Therefore, there is a contagious dispersion of mistletoe seeds in P. guayaba; trees with numerous mistletoe parasites have more parasite seeds and seedlings than trees with few or none. Contagion in mistletoe creates a general problem in dispersal, in that genetic variability is likely to decrease (Reid et al. 1995), while competition and density-dependent mortality are likely to increase. How mistletoe counters these potential problems requires further study.

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  Distribution patterns of the tree ferns Alsophila erinacea and A. polystichoides (Cyatheaceae) in cloud forests of Monteverde, Costa Rica, December 2003

  Stephen Gottschalk

  The effects of elevation on the tree ferns Alsophila erinacea and A. polystichoides (Cyatheaceae) distributions were examined between 1550 m and 1800 m in Monteverde, Costa Rica. Alsophila erinacea and A. polystichoides prefer similar habitat types and overlap almost completely in their elevational ranges, making them ideal species for comparison. Six transects were made in each of five-50 m elevational blocks between 1550 m and 1800 m for a total of 30 transects. Transects along a ridge trail were compared with those on a trail on the side of a slope and were found to contain considerably less Alsophila tree ferns at all elevations (a total of 5 individuals on six ridge transects compared with 36 individuals on four slope transects). There was a slight decrease in these two species' abundances on an increasing elevational gradient. Both species of fern were found to be patchy based on an index of dispersion, Poisson comparison, and Chi-squared tests (X2 = 710 and 33063; df = 9 and 18; P = 0.001 and 0.001 for A. erinacea and A. polystichoides respectively). Finally, microclimate variations likely did more to influence A. erinacea and A. polystichoides distributions than did elevation.

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  Effect of climate change on four species of Azteca in Monteverde, Puntarenas, Costa Rica, December 2003

  Paul Mazzei

  There has been extensive, research in the Monteverde area that has shown that both the abundance and range of lizards, amphibians, and birds have been affected global warming (Pounds (1999). Although there have been studies showing changes in abundance of arctic and temperate invertebrates, there have not been any studies that have shown invertebrate response to climate change in Monteverde. The four species of Azteca ants (xanthochroa, constructor, coeruleipennis, and alfari) were collected along roads in Monteverde and nearby Santa Elena and San Luis at elevations ranging from 700-1500m. The altitudinal ranges from this study were compared to ranges obtained by Longino in 1985 to determine if these four species have shifted upward in elevation (Longino 1989). A one way analysis of variance compared the elevations of the four species to one another and found that all four were statistically different in the elevations that they occupy except for A. xanthochroa and A. constructor which are both high elevation species. This data agrees with previous research by Longino that has shown that these four species occupy different altitudinal bands. A. coeruleipennis was shown to be a strictly low elevation species and A. alfari occupies low to mid-elevations. When the mean values for elevation from this study were compared with Longino’s 1985 mean elevations using a one sample t-test A. xanthochroa and A. constructor the results were significantly different (P = .0033 and P = .0342 respectively). The mean values for A. alfari were not statistically significant (P = .1462) in the one sample t-test, but this is most likely due to small size in comparison to Longino’s findings. In conclusion three of the four species of Azteca that were studied showed evidence of an upward shift in elevation. When interpreted in conjunction with the previous studies on lizards, amphibians and birds, the upward shift in range of Azteca spp. provides even more evidence that global warming is having a dramatic effect on altitudinal distributions in Monteverde.

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  Effects of habitat disturbance on the territorial response of the gray-breasted Wood-Wren, Henicorhina leucophrys, December 2003

  Blake Audsley

  Habitat fragmentation and disturbance have become integral aspects of the neotropical landscape, impacting a variety of ecological factors. Here I attempt to quantify the relationship of bird territory size and habitat disturbance by observing the effects of habitat disturbance on avian response to conspecific playback in the Gray-breasted Wood-wren, Henicorhina leucophrys. Mean distance traveled to follow playback increased along a gradient of increasing disturbance (F = 4.435, p-value = .0165, s.d. = 27.256; 47.283; 49.094). Edge habitat birds showed significantly greater response than birds in primary and secondary growth (p-values = 0.0051; 0.0479). Variation in response also differed between habitats. These results may be due to a variety of factors that varying along a disturbance gradient, including prey abundance, predation risks, structural characteristics, and territory shape and distribution.

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  Effects of tree buttresses on nutrient availability and macroinvertebrate species richness, December 2003

  Alyson P. Mack

  This study tested the hypothesis that buttress microhabitats collect more leaf litter and have greater macroinvertebrate species richness, thereby increasing the leaf decomposition rate and providing more nutrient rich soil for the tree. Leaf litter deposition and decomposition rates, soil fertility (pH, [N], [P], |K]), and macroinvertebrate species richness (S, Smarg) were compared between microhabitats in buttressed and nonbuttressed trees and open areas in the lower montane cloud forest of Monteverde, Costa Rica. Results showed no significant difference between microhabitat types for soil pH levels (Kruskall-Wallis test, H= 3.188), soil [N] (Kruskall-Wallis test, H= 3.388), soil [P] (Kruskall-Wallis test, H= 6.215), soil [K] (Kruskall-Wallis test, H= 4.304), deposition rates (Kruskall-Wallis test, H= 3.599), or decomposition rates (Kruskall-Wallis test, H = 1.746). There was no significant difference in species richness (S) between buttressed trees and non-buttressed trees (Kruskall-Wallis post hoc, q = 1.72) or between non-buttressed trees and open areas (Kruskall-Wallis post hoc, q = 2.64). However, the difference in S between buttressed trees and open areas was significant (Kruskall-Wallis post hoc, q = 4.36). Results suggest that increased leaf litter biomass in buttresses is due to their functioning as collection cavities. Similarities in soil fertility and decomposition rates may be attributed to edaphic and leaf litter heterogeneity within microhabitats. It is apparent that buttress microhabitats are unique in structure, microclimate, and macroinvertebrate community complexity; however results of this study are inconclusive as to whether buttresses actually provide the tree with more nutrients. The role of buttresses in improving local soil quality needs to be further examined, with more consideration given to spatial heterogeneity within microhabitats.

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  Family composition of vascular epiphytes varies by directional quadrant, December 2003

  David N. Bums

  Vascular epiphytes are an extremely diverse and prevalent plant-form of neotropical cloud forests, and are strongly affected by abiotic factors including light and moisture. The goal of this study was to determine whether the family composition and diversity of vascular epiphytes living on pasture tree trunks differed by quadrant (northeast, northwest, southeast, and southwest). It was hypothesized that the northeast quadrant would exhibit the greatest diversity due to the mist-laden trade winds blowing from that direction. Twenty trees in a pasture surrounded by lower montane wet forest in Monteverde, Puntarenas, Costa Rica were divided into four quadrants and sampled for vascular epiphytes (N = 597 plants), which were tallied by family. A Chi-squared analysis revealed that there was a nonrandom frequency of families across quadrants (x2 = 29.445, df = 12, P = 0.0034). The family diversity of the northeast (H’ = 2.067) was significantly higher than the diversity of the southwest (H’ = 1.817; t = 2.497, df = 263.04). Additionally, there were more bromeliads in the northeast than expected (54 observed, 34.7 expected), and less than expected in the southeast (15 observed, 22.1 expected) and southwest (7 observed, 18.4 expected). Also, there were more Pteridophytes in the southwest than expected (45 observed, 36.8 expected) and less than expected in the northeast (54 observed, 69.5 expected). These differences may be due to a combination of abiotic and biotic factors related to moisture acquisition by the epiphytes.