Monteverde Institute: Tropical Ecology and Conservation

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  Seed toughness in Persea americana (Lauraceae) and Dioclea reflexa (Papilionaceae) and feeding behavior in agoutis (Dasyprocta punctata), 2007

  Maria Peterson

  Agoutis are a common study subject because of their caching behavior and for their role in seed dispersal in the tropics (Wainwright 2002). This study examined the relationship between the hardness of seed coats and their rate of consumption by conducting trials at eight known agouti territories in Monteverde, Costa Rica using softened and untreated seeds. Trials were conducted separately for each seed species. A significant difference was found between the number of hard and soft seeds of Persea americana and Dioclea reflexa left behind at the sites. According to statistical tests, agoutis seem to prefer softer seeds of P. americana over hard seeds (Wilcoxon Matched Pairs test, p = 0.0858) and no preference in D. reflexa (Wilcoxon Matched Pairs test, p = 0.715). This difference can be explained by the much more noticeable softening of P. Americana when compared to D. reflexa, which may have allowed a shorter seed handling time.

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  Variation in the abundance and diversity of Hymenoptera as an indicator of biodiversity across three tropical habitats in Monteverde, Costa Rica, August 2007

  Jessica Ramsel

  Loss of biodiversity is becoming increasingly evident and is receiving much attention. Fragmentation and conversion of natural forest into agricultural land in particular are increasingly detrimental to biodiversity. It has been stated that agroecosystems such as agroforestry provide a valuable contribution to the overall biodiversity of the landscape and may even be suitable for conservation efforts (Tylianakis et al. 2005; Klein et al. 2002). This study examined the relative abundance and diversity of Hymenoptera within three habitats: primary forest, an agricultural area, and an open area. This was done by placing yellow plates with honey and soap water in each of the three areas. The plates were left out for five hours and then all Hymenoptera were collected and analyzed to find relative abundance and diversity. It was found that there was no significant difference in the number of individuals or species between primary forest and the agricultural area (Student t-test: t = 3.04, df = 275, p = 0.164). In contrast, there was a significant difference between primary forest and the open area (Student t-test: t = 5.83, df = 53, p < 0.001) and the agricultural area and the open area (Student t-test: t = 7.80, df = 51, p = 0.009). The greatest numbers of individuals were found in the primary forest and the greatest number of species in the agricultural area. The fewest species and individuals were found in the open area. That there was no significant difference between numbers of species or individuals in primary forest versus agroforest may suggest that agroforest could be a suitable area in which to focus a conservation effort.

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  Allelopathic effects on leaf litter invertebrates under Dicksonia gigantea (Polypodiopsida: Dicksoniaceae) and Cyathea caracasana var. meridensis (Polypodiopsida: Cyatheaceae), May 2007

  Patricia A. Schmitt

  Allelopathic chemical release may affect many aspects of plant and soil ecology, including community composition, diversity, and richness (Ferguson 2003). The effects of allelopathic chemicals in tree ferns D. gigantea and C. caracasana var. meridensis on the biodiversity of leaf litter invertebrate communities were examined in the Monteverde Cloud Forest. In total, 15 sites were surveyed, where a paired sample of one tree fern and one non-fern tree were collected, filtered and invertebrates were analyzed to morphospecies. When examining the local communities under tree fern and non-fern trees, no significant difference in N, S, H', Smarg and E was found. However, there was a significant difference in the H' of tree fern and non-fern trees (Modified T-Test, t = -2.52, p < 0.05, df = 2075), as well as observed differences in N, S, Smarg and E, on the metacommunity level. All indices were found to be higher under non-fern trees. Seven invertebrate species were also observed having a ≥20 % change in abundance, suggesting that certain species may be more affected by the presence or absence of allelopathic chemicals. These include springtails (Order Collembola), one spider morpho species (Order Arachnida), one beetle morpho species \(Order Coleoptera), insect larvae (Class Insecta), silverfish (Order Zygentoma), angel insects (Order Zoraptera), and caterpillars (Order Lepidoptera). Allelopathic effects on bottom-up trophic level interactions are a plausible explanation as to why changes in the abundance, richness and diversity of leaf litter invertebrates may occur under tree ferns.

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  Altitudinal variation in Ithomiine (Nymphalidae) color patterns, May 2007

  Nicholas Sullender and Daniel Winokur

  Ithomiine butterflies contain several color complexes that fly at different heights in the forest, presumably in response to light conditions (Papageorgis 1975; Burd 1994). If so, these complexes should also respond to altitude, as light conditions in the forest change altitudinally. A previous study by Haber (1978) showed that color complexes do respond to altitude, but in a way inconsistent with light response. Either the previous study failed to incorporate forest conditions, like openness, which also alter light levels, or ithomiine color complexes are responding to altitude for different reasons, including the possibility that each color complex had a different center-of-origin corresponding with different elevations. We caught butterflies in closed forest conditions along both slopes of the continental divide in Monteverde, Costa Rica at seven different sites along an altitudinal gradient, from 800 m to 1600 m. Two of the three color complexes responded to altitude, but in ways inconsistent with our expected light response. Clearwings, which favor dark conditions, were more abundant at high altitudes while tiger stripe species, favoring strong, direct and sun-fleck light conditions, were only found at lower altitudes on both slopes. Pacific slope forests generally had more open canopies but the patterns were nearly symmetrical on both slopes. Therefore, we conclude that the change was more likely a result of color complexes evolving at different altitudes and secondarily migrating out of these altitudinal bands. Additionally, light and altitude seem to cause a more complicated relationship than expected, probably because of increased cloud cover and epiphytic growth with increased altitude.

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  Assessing the effects of new and old conservation policies in Costa Rica, May 2007

  Danielle Knight

  Cost[a] Rica’s national conservation policy was recast into SINAC (National System of Conservation Areas) about a decade ago (World Bank 2000). Major changes in the new policies include pairing the management of biodiversity and the management of sustainable development and resource use (SINAC website, 2007). This change sparked criticism and many worried that the shift might leave policy in favor of development instead of sheer protection for biodiversity. SINAC also changed the administrative structure of conservation management and condensed seventy-eight different territories into eleven conservation areas spanning all of Costa Rica’s territory (Evans 1999). Recent studies show that the state of conservation policy and its effectiveness in the country is less an effect of new policies than it is the way funding travels between the central government and Conservation Areas. These areas generate enough money to sustain the country’s conservation goals but the central government does not return enough of the generated revenue for these goals to be realized.

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  Atta cephalotes as a bioassay tool to identify the presence of polar secondary compounds in medicinal plants of Monteverde, Costa Rica, May 2007

  John Thurston

  Atta cephalotes has shown potential as a bioassay tool for antifungal characteristics of medicinal plants (Hubbel, et al. 1983). This experiment tests a variety of plants with differing secondary compounds to explore further uses of A. cephalotes as a bioassay tool. A polar solvent was used to make crude extractions of twelve different medicinal plants to test the preference of Atta for the extract compared to a control. It was predicted that A. cephalotes would show a negative preference towards plants with antifungal compounds. However, negative preference for Brugmansia suaveolens, a plant with no known antifungal compounds, deterred A. cephalotes the most.

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  Behavioral adaptability of calling in a species of cricket (Orthoptera: Anastostomatidae) based on an increase in interference from a heterospecific natural chorus in San Luis, Costa Rica, May 2007

  Lee Kaiser

  Orthoptera are among the first musicians on earth, and the deep evolutionary history of crickets involving acoustics has allowed them to greatly develop systems to produce and process such sensory information. This study attempts to contribute to the knowledge base of cricket behavioral biology through observation of changes in call characteristics of a species of cricket based on an induced increase in heterospecific natural chorus complexity in San Luis, Costa Rica. A chorus recording was used to induce such an increase in the complexity of the acoustic surroundings of the studied cricket in order to gain insight into how their call rates and song compositions are impacted. The results showed a decrease in calling activity(ANOVA: F = 3.09, df = 2, df Error = 126, P = 0.049), and a trend for the concentration of calls into fewer simple series of chirps during the period of increase in the complexity of their acoustic surroundings. This suggests the ability and inclination for crickets to adjust their calling behavior based on the calls of heterospecifics in order to most effectively and efficiently utilize singing activity, as sound production is very energetically expensive.

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  Body size and sexual selection in Heliconius charitonius and Heliconius melpomene (Lepidoptera: Nymphalidae), May 2007

  Megan Petrie

  The role played by body size in sexual selection was investigated in captive populations of Heliconius charitonius and Heliconius melpomene butterflies. Mean fore-wing lengths of the entire population were compared to those of individuals participating in mating and pre-mating behaviors. It was predicted that because fitness in butterflies often increases with size (Klingenberg and Spence 1997), Heliconius spp. should choose larger mates. Sexes did not differ in size for either species (H. charitonius: Males = 41.14 mm ± 2.41, n = 57; Females = 41.28 mm ± 3.40, n = 48. H. melpomene: Males = 36.29 mm ± 2.54, n = 30; Females = 36.01 ± 1.82, n = 38). Moreover, there were no differences in size for any of the precopulatory behaviors seen compared to those for the general populations. No evidence of assortative mating was found when comparing pairs of males and females in later stages of courtship (p = 0.622, R2 = 0.0193, n = 30). Matings were infrequent, but showed no size difference except for H. melpomene males, who were significantly smaller (34.45 mm ± 1.79, n = 13, t = 2.714, p =0.011, d.f. = 32). Therefore, mating in these two species of Heliconius seems to be independent of body size. Perhaps body size does not impact fitness, or other factors, such as chemical defense, agility or age are more important fitness indicators in these species.

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  Effect of colony size on age structure and behavior of Metabus gravidus (Araneidae) in the Monteverde Cloud Forest, May 2007

  Laura Peterson

  Metabus gravidus are semi-social orb-weaving spiders living in colonies of up to 70 individuals over slow moving water. Buskirk (1975a) found that the time budget of spider behaviors differs within colonies of various sizes. I recorded the frequency and time spent on orb maintenance, aggressive behavior, spider displacement, and prey capture for spiders of varying sizes. Spider and web sizes were measured and then I observed 21 spiders of each size for an hour to record the time and frequency of the four behaviors. In the twenty-four colonies studied, small spiders were more abundant. Small colonies had a greater number of small spiders and large colonies contained more large spiders. Length of behavior did not correspond with spider size in small, medium, or large colonies, but the frequencies show behavioral trends. A higher frequency of aggressive behavior was found in large spiders and a higher count for maintenance was found in small spiders. It is possible that small spiders are deterred from dispersing to large colonies with a greater number of large spiders because an increase of spider size correlates with an increase in aggressive behavior (Buskirk 1975a).

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  Effects of habitat on avian antipredator behavior, May 2007

  Jodi Anderson

  A variety of anti-predator behaviors have evolved in birds because of the far-reaching effects of predation risk. The use of anti-predator behavior is a trade off, as it can dissuade a predator, but it also depletes time and energy from foraging and other activities. Forests provide better protection from predators than do open field habitats. Birds were tested in both forest and open habitat to determine if habitat type had an effect on frequency or aggressiveness of anti-predator behavior. Calls of two different predators were played at different sites in each habitat type, where reactions of birds were observed and recorded. More birds exhibited anti-predator behavior in the open than in the forest (χ2 = 4.27, df = 1, p = 0.04). Birds that inhabited the open areas also reacted more aggressively (χ2 = 13.28, df = 4, p = 0.01). This study showed that the continual conversion of land from forest to non-forest may have serious impacts on bird populations as predation risk will continue to rise. Habitat fragmentation may ultimately cause suitable habitat patches to become too small and too isolated for viable populations to sustain themselves.

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  Evaluating windbreaks as a conservation strategy for pollinator communities in altered and fragmented landscapes, May 2007

  Anna Gouznova

  In Costa Rica, sustaining human population growth has required fragmentation and conversion of its Tropical landscape to an agricultural one. Such large scale land use changes decrease local abundance of species and disrupt important ecological relationships, including species richness and productivity within pollinator communities (Kearns et al. 1997). Pollinators are essential in maintaining stability of plant communities and their dependent consumers. Moreover, in specialized pollinator-host plant mutualisms, the loss of either will reduce or eradicate population of the other. To counter effects of habitat fragmentation, agricultural communities incorporated windbreaks into crop fields and pastures as a restorative effort. I evaluate the performance of windbreaks as repository for pollinators in the San Luis Valley of Puntarenas, Costa Rica by assessing richness and abundance of both pollinator and insect communities within three distinct windbreaks and a bordering secondary growth forest. Pollinator species richness was highest in the forest (H`= 3.72), along with superior numbers of families and individuals. Two species of non-insect pollinators, hummingbirds Amazilla tzacatl and Hylocharis eliciae, were never seen in the forest but regularly in two of the three windbreaks. The two sites, one in a shade grown, Coffea arabica (Rubiaceae) farm and the second, in a pasture, supported comparable species richness (H` = 2.65 and H` = 2.93), and while a slightly lower amount of individuals was collected in the farm site, it contained nine more families than the pasture. In the same pasture, the third windbreak exhibited lowest diversity (H` = 2.65), and nearly half the number of families and individuals found in the first, neighboring pasture site. Higher pollinator richness and abundance correlated with lower mean temperatures of about 26˚C and wind speeds in the range of 0.38 m/s - 0.9 m/s. Overall, structural attributes, including plant species composition, presence of bodies of water and abiotic conditions, determined a windbreak’s capacity to retain pollinators in an altered landscape.

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  Factors influencing dispersal and population structure of phoretic mites in Centropogon solanifolius (Campanulaceae) and Columnea spp. (Gesneriaceae), May 2007

  Emily Davis

  Phoretic hummingbird flower mites of the genus Rhinoseius are nectar thieves of Centropogon solanifolius (Campanulaceae) and Columnea spp. (Gesneriaceae) at Monteverde. Dispersal by phoresy is a rare and risky, but nonetheless critical, event in the lives of hummingbird mites (Colwell and Naeem 1994). This study investigates factors that influence phoretic dispersal by R. colwelli (Mesostigmata: Ascidae), by comparing dispersal from C. solanifolius and Columnea spp. Additionally, this study explores the relationships between mite population size and structure in the two plant species. Flower age, mite population density, sex ratio, and nectar availability were considered as possible influences on dispersal and population structure. Artificial phoresy experiments were performed in the field and collected flowers were analyzed for nectar volume and mite populations. Population size was significantly, positively correlated to dispersal in both flowers (p < 0.000001, R2 = 0.229 for C. solanifolius; p < 0.000001, R2= 0.57 for Columnea), whereas nectar availability and flower age had no significant effect on dispersal. Population size had a significant, negative effect on proportion of males in a flower for both flowers (C. solanifolius: p = 0.0041, R2 = 0.236; Columnea: Spearman’s Rank p = 0.0002, Rho = -0.9328). This may be a result of the increasing tendency for male mites to disperse as population size grows, in order to find flowers with more unmated females. The haystack model of group selection might be implicated in the mite population structure of these two plant species.

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  Habitat and diversity of cloud forest invertebrates, May 2007

  Matthew S. McClure

  This study addresses the effects of abiotic conditions on canopy soil macro-invertebrate diversity by examining five Pacific and five Atlantic slope trees near the Biological Station in Monteverde, Costa Rica. Trees were sampled using single rope climbing technique, and macro-invertebrate were separated from soil samples in Berlese funnels the same day of collection. The meta-community, both slopes as one community showed that Coleoptera, Hymenoptera, and Hemiptera:Homoptera are the major taxa present. The two communities failed to show significant differences in their diversity (modified t-test = 1.03, p > 0.05), richness, and evenness from abiotic conditions. Biotic conditions must be the dominating factor controlling species overlap (8 species) between slopes. This is most likely due to interspecific interaction of invertebrates with plants. Random assortment probably controls most of the invertebrate assemblage for each individual tree.

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  Hemoparasite load in bats with varying roost size in San Luis, Costa Rica, May 2007

  Robin Miller

  Bats, as well as most other mammals, are host to many endoparasites that can damage or even cause death in their host (Baron 1996). I surveyed blood parasites from 28 bats in San Luis, Costa Rica. This study focused on six different species of bats with varying roosting behaviors to determine the amount and type of blood parasites differs between bat species. I identified four different types of blood parasites as well as a gram-negative bacterium. Using a proportion between the total number of parasites and the number of individuals caught per species, I found Myotis keaysi, which roosts in groups of over 500 individuals, to have more total average parasites (x2 = 28.47, p = 0.00424, df = 4, p < 0.0001). I also found significance difference between each individual species of parasite and the different species of bats (x2 = 42.70091393, p = 7.88447E-70, df = 8, p < 0.0001). Although data indicates that bats roosting in extremely large groups have more average blood parasites, more data is needed, in terms of sample size, in order to make further conclusions.

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  Light exposure affects secondary compound diversity in Lichen communities in Monteverde, Costa Rica, May 2007

  Bonnie Waring

  Most lichen produce secondary compounds that have a variety of functions, including pathogen resistance, deterrence of herbivory, and protection from irradiance. In lichen, production of a given secondary compound is a species-specific trait. Thus, community composition may be strongly affected by ultraviolet light exposure, since certain species are able to produce UV-screening compounds while others cannot. To determine the effect of UV exposure on lichen communities, lichen morphospecies were sampled in pasture, forest edge, and forest interior environments and assayed for the presence of UV-absorbing secondary compounds. The Shannon-Weiner diversity index of UV-screening compounds was significantly higher in the pasture (H’ = 1.98) than in the forest edge (H’ = 1.60) (t = 2.79, p < 0.05) and than in the forest interior (H’ = 1.60) ( t = 3.66 , p < 0.05). However, the forest edge and interior communities did not differ significantly from one another with respect to diversity of UV-protective compounds (t = 0.01, p > 0.05). This is persuasive evidence that UV exposure is a significant factor in determining the species composition of lichen communities.

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  Mycorrhizal abundance in aerial versus terrestrial roots among the climbing Araceae of the Monteverde Cloud Forest, May 2007

  Sydney Glassman

  Climbing plants of the family Araceae are a prominent feature of the Monteverde Cloud Forest in Costa Rica. Aerial and terrestrial roots were collected from two species of climbing aroids Syngonium sp A (n = 15) and Philodendron aurantifolium (n = 17) and analyzed for mycorrhizae presence and abundance. Evidence of mycorrhizae infection was found in every plant sampled, and percent abundance of mycorrhizae in the aerial roots of Syngonium sp A ranged from 7.9-90%, while the mycorrhizal cover ranged from 5.3-38% in terrestrial roots. Mycorrhizal cover in the aerial roots of P. aurantifolium ranged from 8.2-57%, and from 4-33% in terrestrial roots. While a significant difference was not found between the aerial and terrestrial roots of P. aurantifolium (Paired t-test, t = 1.74, p = 0.10), mycorrhizae was significantly more abundant in the aerial roots of Syngonium sp A than in the terrestrial roots (Paired t-test, t = 3.11, p = 0.008). Additionally, individuals of the species Syngonium sp A experienced on average a greater percentage of mycorrhizal infections in their aerial roots than did P. aurantifolium individuals (Unpaired t-test, t = 2.19, p = 0.036). No difference in mycorrhizal infection was detected in terrestrial roots (Unpaired t-test, t = 0.19, p = 0.849). This report confirms the presence of mycorrhizae in two species of tropical climbing aroids, and suggests that aerial roots of an individual climbing plant may harbor on average more mycorrhizal infections than their respective terrestrial roots.

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  Population abundance, sexual expression, and gender ratios of Marchantia sp. along an elevational gradient in Monteverde, Costa Rica, May 2007

  Laura Garrison

  Fisher’s theory on sex ratios states that a 1:1 ratio of males to females typically will result when both sexes are equally expensive to produce. Many bryophytes, however, tend to express female sex biases. I took two population censuses of Marchantia sp. during dry season and the transition from wet to dry season along the Sendero Principal in Monteverde, Costa Rica, to determine population abundance and sex ratios. Elevation did not significantly correlate with population abundance (Spearman rank correlation census one: rho = -0.213, P = 0.372; census two: rho = -0.118, P = 0.409). I found local female proportions to vary at different sites in both censuses (Chi-squared test for independence census one: χ2 = 175.861, df = 7, P < 0.0001; census 2: χ2 = 292.349, df = 7, P < 0.0001) and, although non-significant, I noticed a trend towards increasing gemmae presence with elevation in census two (Spearman rank correlation rho = 0.405, P = 0.28). Finally, I found a strong female meta-population bias to become more pronounced as the rainy season progressed. Small dispersal ranges of Marchantia sp. are likely preventing higher abundance; its ability to colonize an area can be attributed more to micro-habitat resource availability than elevational conditions, although trends of gemmae increase are likely due to stable moist conditions at high elevations. Marchantia sp. may display a higher proportion of females in the meta- and local populations due to higher male nutrient requirements, prompting local mate competition to act between males for limited resources in micro-habitats.

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  Precipitation variation and its effects on the reproductive success and survival of Lepanthes jimenezii (Orchidaceae), May 2007

  Katherine McCall

  Tropical cloud forests like that found in Monteverde, Costa Rica rely heavily on daily precipitation in the form of mist during the misty-windy and dry seasons. Studies have shown that this mist is occurring less frequently due to climate change (Pounds et al. 1999). This field study examines the effects of increased precipitation frequency, to mimic that found in the 1970s, on a specific member of the Orchidaceae family, Lepanthes jimenezii (Pounds et al. 1999). Additionally it compares such effects with those that L. jimenezii experiences in current conditions and those that may occur in the future. I divided a group of 83 orchids into three different sample groups. The first was exposed to ambient (and contemporary) conditions, the second to supplemented mist (1970s conditions) and the third to conditions that decreased the frequency of current precipitation (potential future conditions), although not volume. An ANCOVA test of covariance determined that average leaf change was positive only in the supplemented orchids showing that higher reproductive success is more common in orchids with more frequent precipitation (F = 56.59, p < 0.0001). With 82% mortality in the orchid group with restricted precipitation frequency, 64 % mortality in the ambient orchids, and only 10% mortality in the group of orchids given supplemented mist, results suggest that L. jimenezii is negatively impacted by current and future conditions with more variable precipitation, and that the mistier 1970s conditions provide an adequate habitat for the orchids.

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  Re-establishing recycling in Monteverde, Costa Rica, May 2007

  Sydney Funsinn

  As consumer culture continues to expand on a global scale, the importance for responsible waste management also becomes increasingly important (Assadourian et al. 2004). In Monteverde, Costa Rica a recycling program was sustained from 1996 until 2003, successfully diverting 78 tons of waste from local landfills (Friends of the Monteverde Cloud Forest, 2007). In order to evaluate the former program, identify the current obstacles restricting its re-establishment and to identify key aspects of a successful future program I performed interviews and surveys of its main constituents within the community. This included interviews with the organizations involved in both past and future programs, talking with businesses and tourists in the area and conducting a survey of local residents. A combined effort between the Municipality and Tropical Science Center is currently working on its re-establishment and broad support from all potential users of the community was found to exist. However, raising the needed $20,000 – 40,000 dollars to build a local recycling center is a very large obstacle for the community. Through analysis of the information I collected in both surveys and interviews I make some recommendations and suggestions for what would constitute a successful future recycling program for the Monteverde area.

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  Riparian microhabitat selection by Norops oxylophus (Polychrotidae) in San Luis, Costa Rica, May 2007

  David S. Steinberg

  Microhabitat studies of anoline lizards have traditionally measured small-scale characteristics, such as perch height and perch diameter. Riparian anoles, however, may inhabit a more complex environment, since they are in direct contact with rivers or streams; thus, a broader spectrum of variables, particularly those related to river qualities, may be necessary to garner a greater understanding of microhabitat choice in these lizards. In this study, I examine microhabitat selection by Norops oxylophus in relation to both traditional variables and three river variables in the San Luis Valley, Costa Rica. Results show that male lizards prefer higher perches (mean = 0.900 ± 0.301 m, N = 12) than do females (mean = 0.192 ± 0.152 m, N = 13) or juveniles (mean = 0.338 ± 0.337 m, N = 31), while females prefer wider perches (mean = 0.138 ± 0.067 m; N = 5) than do other lizards. Also, N. oxylophus in general seem to prefer riverside sites that are wider and deeper (meanwidth = 3.077 ± 1.375 m, meandepth = 0.183 ± 0.062 m, N = 56) than are unoccupied riverside sites (mean width = 1.852 ± 0.748 m, meandepth = 0.138 ± 0.137 m, N = 56). This study supports the hypothesis that factors related to rivers influence riparian anole microhabitat selection.

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  Species specific Müllerian body production and anti-herbivore defense in the Azteca- Cecropia mutualism, May 2007

  Eric Lawyer

  In Monteverde Costa Rica there are five species of Azteca (Formicidae) that inhabit Cecropia (Cecropiaceae) in a facultative ant-plant mutualism (Longino 1989). Azteca provide Cecropia protection from herbivory while Cecropia provide a home for Azteca in trunk internodes as well as glycogen and protein-rich Müllerian bodies (Janzen 1973). Because some Azteca show more aggressive behavior when Cecropia is disturbed (Longino 1996), it would be expected that their host Cecropia would suffer lower herbivory than Cecropia inhabited by less aggressive Azteca. In this study, herbivory and Müllerian body production were examined in Cecropia with their Azteca mutualists. Although correlations between Azteca species and herbivory and Müllerian body production were not found to be statistically significant, the trends shown by the data indicate that the differential production does indeed occur in that Cecropia with lower herbivory produce comparatively more Müllerian bodies than Cecropia that have received more herbivory . The data presented in this study indicate niche partitioning wherein Azteca that are more heavily invested in Cecropia protection are rewarded in higher Müllerian body production on the host Cecropia.

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  Survival and reproductive fitness of two species of Pleurothallid orchids along a changing climatic gradient, May 2007

  Kerry Kemp

  Increasing periods of consecutive dry days, upward altitudinal shifts in orographic cloud formation, and increasing minimum daily temperatures occurring due to global climate change are rapidly changing the climatic parameters of cloud forests in Monteverde, Costa Rica, where hundreds of diminutive orchids thrive. In order to analyze the affect of changing microclimate on orchid fitness, two species of Pleurothallid orchids, Lepanthes eximia (Range: 1100-2050 m) and Lepanthes monteverdensis (Range: 1400-1550 m) were transplanted to plots at 1530 m, 1645 m, 1800 m. They were monitored daily for leaf, flower, and fruit production and leaf thickness. The microclimatic conditions at each site were significantly affected by elevation (ANOVA with block design; min. temp vs. elevation: F = 8.43, p = 0.001; max temp. vs. elevation: F = 0.88, p = 0.45; precipitation vs. elevation: F = 8.16, p = 0.002). Lepanthes monteverdensis responded to this changing climatic gradient with significantly higher leaf thickness (ANOVA; F = 11.67, p < 0.0001) and a positive change in plant size (ANCOVA; F = 5.71, p = 0.001). Flowering in L. monteverdensis directly mirrored days with measurable precipitation as well, with these displays of increased fitness most prevalent at the mid-elevation site. A trend towards increasing mortality in L. eximia was predominant at lower elevation sites. Both species responded to microclimatic variables, suggesting that these factors are important in their survival and reproduction. With changing climatic conditions, higher elevations may now serve as a climate refuge for Pleurothallid species.

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  Two Agaonid pollinators of Ficus tuerckheimii (Moraceae): parasitism and interspecific competition within an obligate mutualism, May 2007

  Marissa Jones

  The pollinating and non-pollinating wasp fauna of the strangler fig, Ficus tuerckheimii, provide a unique suite of biological relationships in which to observe potential species interactions. Nearly all of the 750 fig species worldwide are pollinated by a single, species-specific agaonid wasp. Pollinated by two congeneric species of fig wasps, Ficus tuerckheimii is a rare exception. I investigated the relationship between the two foundress pollinators as well as the cohort of pollinating and non-pollinating (interloper) wasps that emerge from fig syconia on one tree in Monteverde, Costa Rica. The pollinating species appeared to colonize syconia randomly (R2 = 0.0126, F = 1.234, df = 1.97, p = 0.269). Although interloper wasps were significantly less abundant than pollinating species, there was no association between interlopers and either pollinator or fig seed production (ANOVA, F = 15.568, p < 0.001; LSD, p < 0.001). This study provides evidence to suggest that the overall strength of species interactions in the fig-pollinator-interloper system may not be as strong as ecological models suggest.

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  Wing color and mating preferences of Heliconius sara, May 2007

  Emily Loew

  Convergence in aposematic coloration of chemically-protected butterflies, or Müllerian Mimicry, improves advertisement of unpalatability to predators. Heliconius sara (Heliconiinae) has two races in Costa Rica, each matching a different Müllerian model, one with and the other without a yellow stripe on the bottom edge of the hindwing. Color switching in Heliconius spp. is common but may involve a conflict between natural selection for convergence to models and sexual selection for maintenance of the original color pattern. Here, I manipulate the color pattern of H. sara to determine the degree to which sexual selection constrains color pattern switching. This study was conducted in the Monteverde Butterfly Garden in Monteverde, Costa Rica and looked at mating behaviors of 75 Atlantic race H. sara, which have uniformly black hindwings. Newly- emerged individuals were painted with a stripe of yellow or black on the bottom edge of the hindwing. Mating behavior was observed over 11 days. Males did not show a preference for female wing color for approach, chasing, courtship or rejection (Chi- squared test, df = 3, p < 0.05). However, females seemed to prefer black painted males for approach, chasing and courtship (Chi-squared test, df = 3, p < 0.05). If black is the ancestral condition, these results suggest that color pattern switching in H. sara is constrained by female mate choice.