Monteverde Institute: Tropical Ecology and Conservation

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  Heterogeneity of Lycopodium clavatum patches and the distribution and herbivory strategy of Notodontid moth larvae and their Ichneumonid parasites, September 2002

  Brad J. Oberle

  In this study, a novel system in which a notodontid moth larva (Family Notodontidae) uses Lycopodium clavatum (Family Lycopodiaceae), a cosmopotlitainly distributed clubmoss, as a hostplant. The larva and itself is host to no fewer than three parasitoid wasp species, including two ectoparasites, one of which is from the Ichneumonid genus Netelia. Distribution of larvae and damage to reproductive structures by larvae within the L. clavatum population are explained in terms of potential resource preference by the larvae. Larvae do not exhibit any measurable preference for reproductive structures with a given number of stobili, a character known to be associated with different cytotypes of this highly variable plant species.The findings indicate that distribution of larvae and their patterns of herbivory must be explained either using other characters of the host plant, or are due to other factors such as oviposition behavior of parent moths and parasitoids.

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  Hummingbird-mediated pollen flow across a cloud forest edge, September 2002

  Kate Freund

  Non-territorial hummingbirds that visit more than one species of flower in mixed order can deposit pollen on heterospecific stigmas as they forage. Pollen dispersed to incorrect species lowers the reproductive success of both the pollen donor and recipient plants. While highly specific relationships between some plants and their hummingbird pollinators probably evolved to reduce this type of heterospecific pollen flow, these relationships may break down in severely disturbed areas. This may lead to high rates of pollen deposition at inappropriate flowers. This study looked at hummingbird-mediated pollen flow across a primary cloud forest-pasture ecotone in Monteverde, Costa Rica. While virtually no plant species occur in both habitat types, almost two-thirds of the 89 pollen species observed were found on both sides of the forest-pasture edge, indicating that heterohabitat pollen transfer was occurring. In addition, pollen species shared between habitats was consistently high both within (pasture-pasture and forest-forest) and between (pasture-forest) habitats, suggesting that similarity of plant species is not a good predictor of similarity in deposited pollen species. If heterospecific pollen flow is acting as a major limiting factor of reproductive success for hummingbird-pollinated plants located along a forest edge, then even forest species that continue to be visited by their pollinators after fragmentation may be at risk, as specific pollinator plant interactions are disrupted.

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  Nest building behavior of the resplendent quetzal (Pharomachrus mocinno: Trogonidae), September 2002

  Emily S. Thaden

  Resplendent Quetzals (Pharomachrus mocinno: Trogonidae) form monogamous pairs during the breeding season (Johnsgard 2000). Both the male and female invest in nest building and the parental duties of egg incubation and chick rearing (Skutch 1944). I looked at the nest building behavior of two pairs of quetzals in Monteverde, Puntarenas, Costa Rica. This study quantitatively examined differences between the amount of time each sex spent excavating the nest as well as qualitatively described the behavior of the pair as they worked. The female of one of the pairs spent a significantly longer time working in the nest than the male (p < 0.05). The other pair did not show significant time differences. I describe in detail the tail flapping and soft calling behavior that is only briefly mentioned in other papers. Conservation of the quetzal depends on having accurate descriptions of their behavior so changing trends can be monitored over time.

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  Palatability and anti-predation strategies in Costa Rican butterflies, September 2002

  Genevieve Mauro

  Butterflies have evolved morphological and behavioral characteristics that are thought to inhibit predation. This study ties wing characteristics, flight patterns and speeds, and activity patterns of butterflies with their palatability. Wing loading, wing toughness, scale density, flight speed, sporadicity, wing flaps, and behaviors such as feeding, resting, flying, and chasing were all compared for palatable species and unpalatable species of butterflies in Costa Rica. Palatable butterflies were found to have faster flight and higher sporadicity than unpalatable butterflies. No significant trends were found with wing loading, wing toughness, or scale density. Also, three species that differ in natural history and defensive strategies were specifically examined (Heliconius clysonymus, Morpho peleides, and Caligo Memnon). Their behavior patterns were significantly different as well as their wing flaps per second, suggesting that butterflies engage in activities that enhance their defense strategies. Palatable butterflies spend more time resting than unpalatable butterflies, while the unpalatable butterflies spend most of their time flying and eating. These results suggest that selective pressures placed on butterflies by visual predators have affected the life strategies used by the butterflies.

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  Pollen loads of cloud forest nectarivorous bats, September 2002

  Rhett Miller

  The purpose of this study is to find out the degree of feeding specialization of three nectarivorous bats - Anouri geoffroyi, Glossophaga commissarisi, and Hylonycteris underwoodi - that occur in the Cloud Forest of Monteverde, Costa Rica. The bats were mist netted for a total of nine nights distributed evenly throughout a month, and pollen loads were taken from the chest, head, and back of each bat and placed onto individual slides for the different body parts where the pollen was extracted. The slides were examined to ascertain the types of pollen carried by the bats and some were referenced with a small pollen library and Pollen and Spores of Barro Colorado Island (Roubik and Moreno 1991). A total of 20 morphospecies was found. A two-way ANOVA found a significant difference between the sexes of the bats for pollen species richness (F = 4.247, P = 0.0437, DF = l). Male bats were found to be typically specialists in relation with their feeding habits while females were found to be generalists. Also, a general trend found was that the smaller bat species were found to have a higher abundance of pollen species.

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  The effect of varying forest disturbance on fruit and seed diversity, and black-faced solitaire (Myadestes melanops) abundance, September 2002

  Danielle Leah Wood

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  The effects of distance to the forest edge on avian communities at Ficus pertusa (Moraceae), September 2002

  Julie R. Gilbertson

  This study investigated the differences in bird diversity among 12 fruiting Ficus pertusa (Moraceae) trees at various distances from the forest edge in the Monteverde, Costa Rica region. Each of the 12 sites was observed for six nonconsecutive hours over a four-week study period. Bird diversity, abundance, evenness and similarity were calculated for each tree. A significant positive correlation was found between distance from the forest edge and bird diversity at the study sites (R² = 0.630; ANOVA f value = 17.036; p-value = 0.0021). Crop size was also found to have a significant relationship with diversity (R² = 0.776; ANOVA f-value = 15.630; p-value of distance = 0.0004; p-value of crop size = 0.0382). However, no correlation was found between diversity and diameter at breast height or diversity and crown size. High species turnover among trees was also observed. One species of bird, Turdus grayi (Clay-colored Robin), showed the greatest dominance.

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  The influence of light intensity of the moon on the calling behavior of the common pauraque (Nyctidromus albicollis) during moonlit and twilight hours, September 2002

  Kristin Bondo

  A study of the Common Pauraque (Nyctidromus albicollis) was conducted in an area of Costa Rica that has a pronounced dry season. The mean frequency of calls per minute, number of consecutive minutes of calls, and starting times of vocalizations at dusk were recorded. The mean frequency of Common Pauraque calls per minute, number of consecutive minutes of calls, and maximum number of calls per minute were not direct functions of percent moon face illumination, (Regression, R2 = 0.064, p = 0.1366; Regression, R2 = 0.257, p = 0.0269; Regression, R2 = 0.095, p = 0.2286) respectively. This suggests that weather, breeding, and insect populations may be involved, in relation with the moon, in influencing vocalizational patterns of the Common Pauraque. The number of consecutive calls was greatest on nights where the rising of the moon overlapped with dusk. The lengthening of time during which these birds could call, especially near the equator where dusk lasts at most for 39 minutes, may explain why early accounts have related calling with the phase and brightness of the moon.

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  The influence of remnant tree dispersal syndromes on the succession of a secondary forest, September 2002

  Scott A. Pattison

  A large portion of Neotropical forests are being or have been cleared for agriculture and pasture. Conserving biodiversity in these areas, therefore, will depend on efforts to restore degraded habitat. In order to examine the influence of remnant trees on regeneration in a secondary tropical forest in Costa Rica, this study compared the species composition of plants and seedlings beneath a bird dispersed tree species, Zanthoxylum fagara (Rutaceae), and a ballistically dispersed tree species, Croton draco (Euphorbiaceae), There was no statistical difference found between the two, but when both data were combined, a higher percentage of bird and bat dispersed species was seen in the study site than is typical for local forests. Based on the seedling pool, birds and bats were also the only significant dispersers of primary forest species into the area. These data suggest that dispersal limitations are affecting the species composition and succession processes of the forest.

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  Associations and assembly rules of a vascular epiphyte community in Monteverde, Costa Rica, May 2002

  Ivan D. Welander

  The existence of "assembly rules" and the importance of deterministic versus stochastic processes in ecological communities have been important subjects of debate in community ecology for over 20 years. To add to the debate, I tested for associations in Zone Three vascular epiphyte communities of Ficus tuerckheimii in Monteverde, Costa Rica. Community composition of the 102 recorded species varied widely between trees but tended to be more similar between trees of similar height and location. Also, a negative association was found between epiphytic Araceae and Orchidaceae (P < 0.016), which I suggest is due to abiotic factors rather than interaction. The results are inconclusive in deciding the importance of stochastic versus deterministic processes but lay the foundation for future research.

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  Changes in sugar concentration and volume of nectar in Centropogon solanifolius (Campanulaceae), May 2002

  Jeffrey Benjamin Sanders

  Changes in both the sugar concentration and nectar volume produced by hummingbird-pollinated plants may be evolved features to dictate the actions of the pollinators to optimize reproductive success in the flower. This study attempts to determine the changes in sugar concentration and nectar volume produced over the lifespan of Centropogon solanifolius (Campanulaceae), a hummingbird-pollinated flower. Hummingbird mites (Ascidae) data was examined to look for correlations between colonization and nectar volume. Nectar volume and sugar concentration were recorded for bagged flowers rose early in the plants life and slowed as the chance of the flower already being pollinated increased. Mite colonization proportions mimic nectar volume accumulation patterns. The sugar concentration of nectar remained constant throughout the flowers life and no correlation was found between sugar concentration and nectar volume. A floral nectar production strategy is proposed for C. solanifolius to explain the patterns seen here.

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  Function and size optimization in Mucuna urens vexillum, May 2002

  Mark Macedo

  This study examines the role of the vexillum as an aural nectar guide in the species Mucuna urens. Field manipulations show that the vexillum of M. urens enhances visitation and pollen removal (X2 = 52.8, p<.001). Subsequent observational studies conducted on bat visited hummingbird feeders support this finding as well (X2 = 10.67, p< .005). Data also show an increase in vexillum size correlated with number of bats visits (X2 = 32.06, p < .001). Two explanations are offered for why M. urens and other bat pollinated flowers in the genus have not developed as large a vexillum as possible. Investment return optimization is one possible explanation. Niche partitioning of potential pollinators is another.

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  Insect biodiversity in Ficus tuerckheimii (Moraceae): Which model fits best?, May 2002

  Erin L. Kurten

  Understanding how biodiversity is maintained is important both for ecology and conservation biology. Models of biodiversity fall into two broad categories: resource-based models and deterministic models. Local communities of insects on Ficus tuerckheimii (Moraceae) in the Bullpen, Monteverde, Costa Rica were sampled in order to determine whether the predictions from a resource-based model or Hubbell's stochastic model better fit real data. Results could not conclusively support or disprove either model. Positive trends existed between diversity and resources as well as richness and resources; however these were not statistically significant. Species richness and evenness were not correlated, which does not support Hubbell's model. However, when comparing individual trees to the metacommunity, the incidence of common species in local communities was more similar to their incidence in the metacommunity than the incidence of rare species in local communities was to their incidence in the metacommunity. This is consistent with Hubbell's model.

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  Mist variation and epiphytic orchid abundance in a Monteverde Cloud Forest, May 2002

  Christopher Frohlich

  There has been an observed increase in the frequency of days with no mist during the dry season in Monteverde (Pounds et al. 1999). This trend towards an increasingly dry environment could have detrimental effects on epiphytic orchids. The purpose of this project was to investigate the effect of mist level as well as mist frequency and branch direction on orchid abundance in 12 Daphnopsis americana (Lauraceae) host trees. Mist collectors were placed on 24 sample branches within the first horizontal angle of primary branches and mist was collected for eight days from all directions. Abundance counts of total orchids as well as the subtribe Pleurothallidinae were conducted on the first 1.5 ms of all sample branches. Northeastern branches received the greatest mean amount of mist. A significant difference was not observed in abundance of orchids or pleurothallids on any direction of sample trees (Kruskal-Wallis test, H = 5.805 p > 0.05), however, a higher density of both orchids and pleurothallids was observed on northeasterly branches. Both pleurothallid and total orchid abundance was significantly affected by the number of days of recorded mist as well as the total amount of mist at the sample branches (Simple regression). This study shows that mist levels as well as frequency of mist may be determining factors in total orchid abundance. The increase in the number of dry days in Monteverde may result in the decrease in orchid abundance.

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  Role of driptips on Begonia involucrata (Begoniaceae), May 2002

  Ethan Householder

  This study examined the dual role of multiple driptips of Begonia involucrata (Begoniaceae) in shedding excess water and minimizing erosion beneath a plant. One hundred and twenty leaves, having between one and four driptips were tested both with and without driptips to determine: the amount of water each leaf retained when a given amount was applied to its surface, the volume of soil displaced by each leaf, and the distance the soil was thrown by the drops. When driptips are removed, the amount of water retained on the leaf increases and the mean volume of soil displaced per driptip increases. When driptips are intact, two and three-driptipped leaves experience a 2.5-fold decrease in amount of water retained on the leaf surface. Multiple driptips were shown in increase the amount of soil displaced, with three-driptipped leaves displacing the greatest total volume of soil. The relative abundance of each leaf morph can explained by the interplay of three selective forces: epiphyll growth, erosion underneath the plant, and leaf surface area (a larger surface area increases sunfleck capture). Two-driptipped leaves seem to strike a balance between these forces, and may explain their greater abundance (68%) at an elevation of 1,545 meters.

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  The effects of host species and substratum factors on the abundance and growth of epiphytic orchids, May 2002

  Anna Keller

  It has been observed that epiphytic orchids are less abundant on trees of the genus Quercus (Fagaceae) than on other Neotropical hosts. This study investigates this claim and attempts to link that pattern to substrate inhospitability. The results of orchid abundance counts on Quercus and non-Quercus hosts yielded statistically non-significant results, although the data appear to support this apparent distribution. Specklinia aristata were placed in six experimental treatments in order to examine the effects of pH, fissure depth, and water-holding capacity of the substrate on orchid growth. The results of these experiments also yielded no statistically significant differences between orchid growth on conditions mimicking oak and non-oak bark. However, average new leaf data implicates pH as the most inhibitory factor of orchid growth.

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  The population structure of hummingbird flower mites in Centropogon solanifolius (Campanulaceae), May 2002

  Shelly Gordon

  Hummingbird flower mites of the genus Rhinoseius (Mesostigmata: Ascidae) are nectar thieves of several species of cloud forest plants, including Centropogon solanifolius (Campanulaceae). Rhinoseius sp. disperses by riding on the bills of the hummingbirds that pollinate the flowers. The population size, flower colonization rate, and sex ratio of Rhinoseius sp. in C. solanifolius were examined in relation to flower age and the distance to the nearest open neighbor flower (NND) in Lower Montane Rain Forest in Monteverde, Costa Rica. Population size and the rate of flower colonization were not significantly influenced by the flower age or the NND. Flowers were colonized rapidly and the population size was highly variable. The interaction between flower age and NND did have a significant effect on the sex ratio of the mite population within a flower (Multiple Regression; F = 3.68, p = 0.039). This may be explained by the increased likelihood that female mites leave aging flowers, especially when there are open flowers nearby. There is also a trend toward a negative relationship between NND and the proportion of mature male mites in a flower, which may be explained by the theory of local mate competition.

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  Altitudinal effects on leaf morphology and their implications of plasticity in Piper species, November 2001

  Rachel Chambers

  Leaf morphology is affected by environmental conditions and has therefore been studied in response to many environmental factors, including altitudinal gradients, which can be used to show responses to climatic changes of temperature and moisture. The ability of a plant to respond morphologically to its environment should influence the extent of its range along a gradient of changing environmental conditions. This study shows changes in width/length ratios, surface area, toughness, and petiole length of both young and old leaves within three Piper species along an altitudinal gradient. The ranges of two species, P. amalago and P. dotanum, extend to the end of the premontane wet forest in San Luis, Costa Rica, while the third species, P. hispidum extends into the lower montane wet forest in the Monteverde Cloud Forest Preserve. As expected, P. hispidum shows greater morphological response to climatic changes with altitude, especially in width/length ratios (2-way ANOVA; p = 0.0012) and toughness (2-way ANOVA; p = <0.0001). This plasticity may therefore be the reason for P. hispidum's presence in the lower montane wet forest, where the other two species are not found.

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  Bat morphology and pollinator specificity in a Neotropical cloud forest, November 2001

  Kiva Rice

  This study explores the degree of specialization of nectarivorous bat species and the plants they visit by examining pollen loads. The bat species involved are Anoura geoffroyi, Glossophaga commissarisi, and Hylonycteris underwoodi, all of which feed on nectar and are found in the cloud forests of Monteverde. Five nights were spent mist-netting and pollen samples were taken from the head, fore-body and back of each individual caught. These were placed on slides that were observed under a microscope and pollen morphospecies were counted. Twenty-two pollen morphospecies were found and a few were identified. A 1-way ANOVA test was conducted to compare the mean pollen species richness for each bat species. No significant differences were found (F = 0.243, P = 0.785, DF = 2,33). A cumulative catch curve determined that sampling was nearly exhaustive. A Sorenson index of similarity was conducted to compare the pollen species found on each bat species. Pollen morphospecies overlap was found to be similar between all bat species (A. geoffroyi vs. G. commissarisi = 0.615, A. geoffroyi vs. H. underwoodi = 0.583, G. commissarisi vs. H. underwoodi = 0.545). A few plant species were only visited by species with long snouts, suggesting specialization beyond the general syndromes of glossophagine bats and bat flowers in the Neotropics.

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  Distribution and host species ranges of Umbonia ataliba and Umbonia crassicornis and the potential for Interspecific competition, November 2001

  Charles A. Hernick

  Umbonia crassicornis and Umbonia ataliba (Homoptera: Membracidae) elevational ranges and host tree ranges were studied in Monteverde, Costa Rica. Umbonia crassicornis was known to exist at elevations below 1000 m, while U. ataliba was known to exist at 1300 -1500 m. The possibility of interspecific competition or possible future competition was investigated in light of recent local and global warming trends and observed population shifts in birds and herps by Pounds et al. (1999). A census of Umbonia species and host plants was conducted along an elevational gradient, in addition to an experimental test, which examined U. crassicornis survivorship on U. ataliba hosts. Umbonia crassicornis and U. ataliba were not found to coexist at any elevation. However, signature egg and feeding scars were found on Inga mortoniana, a plant commonly used by U. ataliba, in this case found at elevations likely to be used by U. crassicornis. Complete survivorship by U. crassicornis on Acacia angustissima, a known U. crassicornis host, and Inga mortoniana, a known U. atliba host, was observed, proving I. mortoniana to be an equally suitable U. crassicornis host, at higher elevations. Host species I. mortoniana was found to exist at all elevations studied, while other known hosts for U. crassicornis and U. ataliba were limited to lower and higher elevations respectively. If warming trends affect Umbonia species ranges, thereby expanding U. crassicornis populations to higher elevations, interspecific competition may occur over I. mortoniana.

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  Effect of altitude on cyanide concentration, leaf toughness, and herbivory in Passiflora biflora (Passifloraceae), November 2001

  Matthew S. Martin

  Insect herbivore diversity and abundance often decreases with increasing elevation due to greater extremes in temperature and climate (Janzen 1983; Hanson 2000). As a result, herbivore pressure on plants found at high altitude is lower. Thus, one might expect a reduction in the levels of antiherbivore defenses such as secondary metabolites or high fiber at higher altitudes. To test this, leaves from the tropical vine Passiflora biflora (Passifloraceae) were sampled in the Monteverde area of Costa Rica, from 800-1600m. Leaves were tested for cyanide levels, toughness, and percent herbivory. Cyanide in the leaves of P. biflora was found to increase with increasing altitude (P < 0.0001), while leaf toughness decreased with altitude (P = 0.0407). Increasing leaf toughness was associated with decreasing cyanide levels (P=0.0015). Percent herbivory was constant across altitude, and overall was quite low (1-3% on average); (P = 0.2381). These results may be due to the different climatic environments at high and low altitude: high altitude being colder, wetter, and less sunny. Such conditions inhibit photosynthesis, which may increase costs to toughen leaves. As a result, high altitude plants may be compensating by investing more heavily in cyanide. These trends may also indicate that a greater percentage of total herbivory on P. biflora at lower elevations is by the highly coevolved Heliconius larvae.

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  Is traffic organized on trails of the leaf cutting ant Atta cephalotes?, November 2001

  Angela C. Rao

  The leaf cutting tribe Attini (Formicidae: Myrmicinae) shows numerous adaptations that increase foraging efficiency. Such adaptations are seen in their highly polymorphic caste systems, trails branching from many different exit holes, clearing and maintenance of foraging trails, and pheromonal signaling and recruitment. It is reasonable to assume that mechanisms exist that would reduce incidence of collisions, traffic jams, etc., on foraging trails. This hypothesis was tested by recording trail density and time, linear distance, and direction of ant travel on the trails of Atta Cephalotes and looking for certain trends. Ants traveling towards the nest were not found to vary much from those traveling away from the nest. Because of this and the lack of distance and speed dependence on ant density or direction, it was concluded that some form of organization may exist on foraging trails. The most likely explanation for this is the presence of some organization method such as pheromone trails with a maximum trail width and yielding of ants traveling towards the foraging source to ants carrying leaves.

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  A comparison of moss-dwelling invertebrates along an altitudinal gradient, September 2001

  Lauren Afsahi

  Moss abundance and the invertebrates that inhabit moss differ with varying elevations. The purpose of this study was to determine if there was a significant difference in diversity and morphospecies composition of moss-dwelling invertebrates between three different elevations on the Pacific slope (1550 m, 1650 m, and 1750 m) along a tropical wet cloud forest. This study also examined if there was a significant difference between the diversity and morphospecies composition between the Atlantic and the Pacific slopes at an altitude of 1750 m. Eighty-one samples of one morphospecies of moss were collected from trees in a tropical wet cloud forest in Monteverde, Costa Rica in order to study the invertebrates that inhabit moss. The highest elevation (1750 m) had the highest species richness (44), species abundance (284), and the highest Shannon-Weiner diversity index (H’ = 3.34) which can be explained by increased trade wind exposure, moisture availability, and moss abundance for the moss-dwelling invertebrates. The abundance of the order Diptera was significantly higher in all four sites (x2, df = 3, t = 92.25, p < .0001), and this finding can help explain the similar evenness values for the sites.

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  Agricultural land use and butterfly communities, September 2001

  Anne Baptiste

  Forest habitat in the tropics is being converted at an alarming rate into agricultural lands. The result is loss of global biodiversity at accelerating rates. Butterflies are common indicator species of how biodiversity responds to changing land use. Here butterflies were used to examine the potential impact of different agricultural practices in Monteverde, Costa Rica. Butterflies were trapped in forest, banana, coffee, and pasture. This study found that coffee plantations support significantly greater species diversity (x2 P < 0.005), than banana or pasture. The forest patch was found to support the greatest number of forest dependent species although numbers of these indicator species were comparably high in coffee and banana as well. Forest species were almost absent in pasture and along edge. This suggests that there are crops, which better approximate forest conditions, while drastic land transformations have a large detrimental impact on biodiversity.