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Composicin de la comunidad de colepteros en dos rangos de elevaciones diferentes
Community composition Coleopterans at two different elevational ranges
Digitized by MVI
The order Coleoptera is the most diverse among animals, composing 70- 80% of all described animals in the world. (White 1983) Even though this order is the most described in the world, there is still very little known about their composition in the canopy. Diversity and abundance of the canopy was investigated along elevational ranges attempting to find whether the increase in elevation played a factor in the Coleopteran composition within the canopy. Beetles were sampled at two different elevations in the Monteverde cloud forest at La Estacin Biolgica, Monteverde, Costa Rica. Diversity was found to be highest at the low elevation and the high elevation exhibited a higher abundance. These data suggest that diversity may closely follow a pattern stating that increases of the elevation produce decreases in diversity. Abundance has been found to follow this pattern also, but not as closely, leading to abundance functioning independently of this pattern.
El orden Coleptera es el ms diverso en el reino animal, comprendiendo del 70 al 80% de todos los animales descritos en el mundo (White 1983); aun cuando ese orden es el mejor descrito en el mundo, todava se sabe muy poco acerca de su composicin en el dosel. La diversidad y la abundancia del dosel fueron investigadas de acuerdo a mbitos altitudinales con el fin de determinar si el aumento en la elevacin afectaba la composicin de la comunidad de colepteros del dosel. Se colectaron escarabajos en dos elevaciones diferentes en el bosque nuboso en La Estacin Biolgica Monteverde, Costa Rica. La diversidad fue mayor en las elevaciones bajas y las elevaciones altas mostraron una abundancia ms alta. Los resultados sugieren que la diversidad puede seguir un patrn paralelo en el que el aumento en la elevacin conlleva una disminucin en la diversidad. La abundancia tambin sigue este patrn pero la relacin no es tan cercana, por lo que la abundancia funciona independientemente de este patrn.
Text in English.
Costa Rica--Puntarenas--Monteverde Zone
Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology Fall 2005
Ecologia Tropical Otono 2005
t Monteverde Institute : Tropical Ecology
Community Composition Coleopteran s at Two Different Elevation al Ranges Carrington Dahmer Department of Biology, High Point University ABSTRACT The order Coleoptera is the most diverse among animals , composing 70 80% of all described an imals in the world White 1983; e ven though this order is the most described in the world , there is still very little known about their composition in the canopy. Diversity and abundance of the canopy was investigated along elevation al ranges attem pt ing to find whether the increase in elevation played a factor in the Coleopteran composition within the canopy. Beetles were sam pled at two different elevations in the Monteverde cloud forest at La EstaciÃ³n BiolÃ³gica, Monteverde, Costa Rica. Diversity w as found to be highest at the low elevation and the high elevation exhibited a higher abundance. Th ese data suggest that diversity may closely follow a pattern stating that increase s of the elevation produce decrease s in diversity. A bundance has been fou nd to follow this pattern also , but not as closely, leading to abundance function ing independent ly of this pattern . RESUMEN El orden ColeÃ³ ptera es el mÃ¡s diverso en el reino animal, comprendiendo del 70 al 80% de todo s los animales descri t o s en el mundo White 1983; aun cuando ese orden es el mejor descri to en el mundo , todavÃa se sabe muy poco acerca de su composiciÃ³n en el dosel . La d iversidad y la abunda ncia del dosel fueron investiga das de acuerdo a Ã¡mbitos altitudinales con el fin de determinar si e l aumento en elevaciÃ³n afectaba la composiciÃ³n de la comunidad de coleÃ³pteros del dosel . Se colectaron e sc a rabajos a dos elevaciones diferentes en el bosque nuboso en La EstaciÃ³n BiolÃ³gica Monteverde, Costa Rica. La d iversid ad fue mayor a elevaciones baja s y las elevaciones altas mostraron una abundancia mÃ¡s alta. Los resultados sugieren que la diversidad puede seguir un patrÃ³n paralelo en el que el aumento en la elevaciÃ³n conlleva una disminuciÃ³n en la diversidad . La abundancia tambiÃ©n sigue este patrÃ³n pe ro la relaciÃ³n no es tan cercana , por lo que la abundancia funciona independientemente de este patrÃ³n . INTRODUCTION The order Coleoptera beetles is the most diverse of the animal kingdom with over 300,000 species described throughout the world Dal y et al 1998. Having 178 families throughout the world, Costa Rica houses 110 families. The Coleopteran s are present in a n array of habitats and feed on different forms of vegetation and animal material. Beetles can be found under decaying matter, on r otting carrion, and among fungal communities ; however, the largest number of individuals can be found within the canopy Solis 1999. If this is true then the canopy holds a vast amount of diversity of Coleopterans. To support this wide diversity of Cole opterans, a large amount of biomass must be present. A high number of Coleopteran species have been found to reside within the canopy because of the biomass conditions found in the crotches of trees are similar to
terrestrial habitat s Nadkarni and Longino 1990. Having a large amount of biomass displays a high level of productivity , to which Coleopterans contribute. An example of contribution is composing a major pollen vector within the forest, especially the canopy , following only bees and moths Bawa 1 990. This is a possible reason for the large abundance of Coleopterans within the canopy of the rainforest. The Monteverde cloud forest holds a large portion of the Costa RicaÂ€s diversity, providing home for many native plants and animals . The Monteve rde area is renowned for efforts to preserve the tropical forests and the diversity it contains. Monteverde is composed of a broad elevation gradient ranging from less than 1000 meters to 1800 meters , comprising a mixtur e of diverse communities. Little is known about the factors that most influence the insect diversity in the tropics Lucky et al. 2002, and an even smaller amount about coleopterans. Elevation increase is found to have direct and indirect effects on invertebrate composition within a t ropical forest Holdridge 1967. Increasing elevation will affect the habitat because of changing abiotic factors. Rainfall and temperature are two of the most important abiotic factors that have an affect on habitat diversity and abundance. In tropical forests Huston 1994. From these data it can be proposed that the increase of elevation will cause a decrease in diversity and abundance. This study addresses this idea within a canopy setting. Past studies have been conducted on the order Coleoptera and how their composition in a terrestrial habitat was effected by an increase in elevation Massoud 1998. From this study a pattern was seen. This study was conducted to see if the same pattern occurs within the canopy coleopteran communities. It is p redicted that, in these two elevation al ranges , in the canopy coleopteran community diversity and abundance w ould decrease as the elevation increased . MATERIALS AND METHODS This study was conducted in the Monteverde cloud forest on La EstaciÃ³n BiolÃ³gic a trai ls. Samples were taken from at different elevatio nal ranges between 1500 1600 meters in the low portion of the cloud forest and between 1700 1800 meters in the elfin portion Fig. 1.. A total of ten trees were sampled at random , five in each el evation range . T rees var i ed in height and diameter at breast height, but all occupied space within the canopy. Trees were randomly selected to obtain a more accurate sample from the canopy. Beetles were sampled by using two modified light interception tr aps Fig. 2 that were rigged within the canopy. Each trap contained two black lights that were the main attraction f o r the beetles. Many beetles , active at night, have been observ ed to be attracted to light White 1983. The study ran during the rainy season on the nights of November 5 th , 7 th , 9 th , 10 th , and 11 th in which traps were set at both the low and high elevations in the same evening. Running traps at both locations, simultaneously, minimized variation in weather conditions. The lights were t urned on between 5:30pm to 7:30pm and left on the entire night. Having only one individual conducting the study it was necessary to vary the times in which traps were turned on. Times of turning on the traps varied so as to not bias the amount of time fo r sampling . This standardized the amount of time allowed for sampling
between elevations. Samples were taken from each test site and catalogued by the tree of origin . Classification of these beetles was accomplished by matching the species to the c oleop teran collection at La EstaciÃ³n BiolÃ³gica based on morphological characteristics. All were identified to the family level . The diversity of each elevation al range was determine d by families with the number of individuals from each. A bundance across th e elevation s was determined by taking the total number of individuals from each elevation range and comparing them to one another. Taking this information , the diversity and abundance were tested using Chi Square test s to see if there were any significant differences . Lastly, the diversity was taken from each elevational range and Sha n non Wiener indices calculated to see if there were difference s between elevation sites. Trap Design Two light interception traps were built in order to sample the beetles from the forest. Each was a board box; approximately one meter in height by one half meter in length by twenty centimeters in width , with attachment brackets both sides. Each bracket held one portable black light that was used in attracting the beetles. Attached to the top of the traps , rings were placed for a rope to pass through allowing it to be rigged within the canopy. The traps were also painted white in order to add to the brightness of the black lights when reflected upon . T he base of the trap composed of a large funnel, approximately 40cm in diameter , filter ing down into a three gallon bucket attached to the base of the trap Fig. 2.. RESULTS A total of 299 individuals were collected comprising 13 different families. A t the higher elevat ion al range the number of families found increased. The high elevational range showed a larger sample size 178 individuals, and a smaller s ample size from the low elevation gradient 121 individuals Fig. 3. Rarefaction was applied due to the differe nt sample sizes. This standardized the sample size, giving an expected number of families that would normally occur E S = 7.26 . Richness and evenness of the low elevation sites was higher HÂ€ = 1.88; E = 0.82, than the high elevation sites HÂ€ = 1.79 ; E = 0.75. However, the higher elevation sites showed a higher number of families than the low elevation sites Fig. 4 showing independence for abundance df = 1; abundance: X 2 = 10.87; richness: X 2 = 5. The sites also showed family difference s among the individual test sites. This showed the low elevation sites ga ve a higher difference between families than the hi gh elevation sites High: Â= 0.78; Low: Â=0.98. The low elevation sites displayed a larger average of occurring families than the high elevation sites High: Â‚=5.6; Low: Â‚= 6.4. Comparison of habitat breadths, the high elevation heights showed to have a broader range for which the individuals can be found High: 1/Â= 1.28; Low: 1/Â= 1.02 Table 1.
DISCUSSION Comparis on of the low elevation site to the high elevation site showed the low elevation having a slightly higher diversity value than the high elevation. Past studies have shown that the abundance of invertebrates decrease d as the elevation increased Massoud 1999; however, this study showed an opposite trend . T he high elevation al range displayed more abundance than the low elevation al ran ge . Nadkarni and Longino 1990 found that microclimatic factors such as temperat ure, moisture, and insulation, a ffect the invertebrates, especially of the canopy. They found that the smallest change in any of these abiotic factors can alter the enti re composition of the invertebrate community, including beetles. The factor of elevation increase plays a role in how these abiotic factors are presented to the community. More moisture and lower temperatures may be found at the high elevations, and the opposite can be found at low elevations having a different fauna composition Huston 1994 . This may play a role in the decrease of diversity with the increase of elevation . Certain families of Coleoptera may not be adapted for the different conditions f ound at higher elevations such as the elfin forest in MonteverdeÂ€s cloud forest. This study sampled more individuals from the high elevation than the low elevation. The canopy holds a vast amount of diversity and fauna that has not been researched in d etail . This difference from the proposed model may be due to the lack of study and also that the higher the altitude the more epiphytic fauna is found on the trees that compose the canopy. This in its self may house more species than originally thought; especially beetles. From the samples the e venness of both never achieved complete evenness . This states that no one family alone dominate s the canopy but instead showed to be evenly distributed across both ranges. This balance is crucial to the composi tion and interactions of the tropical forest ecosystem Erwin 1997. B alance may come in many forms, pollination, nutrient cycling, and population control are a few reasons that a balance in the distribution may occur within the Coleopteran order within t he canopy. Having a dominating family of coleopterans would cause a decrease in the fauna within the forest because specific interactions would not occur. Also low habitat breadth values signify that habitat ranges appear to be small. This may also be due to the trend advanced by Erwin 1997 . B eetles may be specific to a certain species of tree , limiting their range. Another important detail to recognize is that this study was done during the rainy season of Costa Rica. This could have had a major r ole in the composition and abundance of the beetles sampled. Different samples may be obtained if this experiment was to be repeated in the dry season. Many insects respond heavily to the fluctuation of the rainy and wet seasons found in Costa Rica Janz en 1984. Many insects arrive with the onset of the rainy season and continue to inhabit the forest well into the dry season. Sampling at this time may lead to a difference diversity and abundance level. Other families may be present in the dry seasons that are not present during the rainy season and thus adding to the diversity and abundance. Reviewing the results conclude that the diversity of the Coleopteran order closely followed the trend that the diversity decreases as the elevation gradient incre ases. The study did not follow the trend for abundance. The abundance showed to be independent of the trend having more individuals sampled at the high elevation gradients than the low
elevation gradients. Higher elevations may not be suitable for certa in beetle families . This support the diversity trend found in this study. However, the families inhabit ing higher elevations are able to flourish because there is a lack of competition allowing for abundance to remain constant . M ore studies need to be c onducted to see if there are certain patterns that o ccur within the c oleopteran communities in canopy habitats . ACKNOWLEDGEMENTS I want to take a little time to thank everyone who has helped me along this entire semester. T hanks t o Karen and Al an Master s f or their great passion and love for biology. To Javier MÃ© ndez for being a guidance during the project and the comments of ÂƒWhat do you want?!?Â„ and for sharing several cigars with me through the course. To Ollie Hyman for helping me in any situation es pecially hiking my trap up to the TV towers , and having the worst ideas on how to get a Nalgene bottle out of a tree. To Maria Jost for the laughs and pictures you decided to take for the great calendar, maybe we should get it published . A nd try to move ou t of the way of flying , OHH HEADS UP!!!! A s I was saying , the way of flying objects. To all the people that came before me to build this program and leaving behind their information for me to use and glean from. Everyone in the group for the great friend ships that I hope will last forever. Greta if yo u ever need a climbing buddy! A shout out to the Ca Ã± itas group and the fun that we had out there and my host family that were always there to help me feel like I was at home that helped more than you will ev er know . And most of all to my family back home that have been nothing less than supportive, and to my Lord and Savior Jesus Christ for giving me the strength to make it through an unforgettable semester. It will stay with me for the rest of my life. LIT ATURE CITED Bawa, K.S.. 1990. Plant Pollinator interactions in Tropical Rain Forests. Annual Review Ecology Systems 21: 405 Daly, H., J. Doyen, A.H. Purcell III. 1998. Introduction to Insect Biology and Diversity. Oxford University Press. New York, Ne w York. Erwin, T.L.. 1997. Biodiversity at Its Utmost: Tropical Forest Beetles. In: Biodiversity II , Reaka Kudla, M., E.O. Wilson, D. Wilson, eds. Joseph Henry Press, Washington, D.C., pp.28. Huston, M.A. 1994 Biological Diversity: The coexistence o f species on a changing landscape. Cambridge University Press, New York, New York. Janzen, D. H.. 1984. Insects. In: Costa Rican Natural History, D.H. Janzen, ed. The University of Chicago Press, Chicago, Il, pp. 623. Lucky, A., T. L. Erwin, and T. D. Wit man. 2002 Temporal and spatial diversity and distribution of arboreal Cabaridae Coleoptera in a western Amazonian rain forest. Biotropica 2002, 343: 376 386. Massoud, V. 1999. Species Richness and abundance of Beetles Coleoptera at Three Different El evations in Primary Forest in the Monteverde Area. UCEAP IMV Monteverde Tropical Biology. Nadkarni, N., J. Longino. 1990. Invertebrates in Canopy and Ground Organic Matter in a Neotropical Montane Forest, Costa Rica. Biotropica 22:286 287. Solis, A. 200 2. Escrabajos de Costa Rica. 2 nd ed. Instituto Nacional de Bioversidad, Costa Rica. White, R. 1983. Beetles. Houghton Mifflin Company, New York, New York.
Figure 1. Map of the trails at La EstaciÃ³n BiolÃ³gica. Blue circles indicate test sites of the low elevation gradient. Red circles indicate the high elevation gradient test sites. Sites of lowest and highest elevation were tested first and the elevation gradient moved towards the central elevation gradients with each new test day. Te sting was conducted in the Monteverde cloud forest at La EstaciÃ³n BiolÃ³gica in Monteverde , Costa Rica , 5 th 11 th of November, 2005 . N
Figure 2. The configuration of the trap from a side view view #1 and a front vi ew of the trap view #2. Monteverde, Costa Rica , 5 th 11 th of November, 2005. Figure 3. Sites at each elevation gradient for each test day and the abundance that were sampled from each. Samples were taken from the Monteverde cloud forest at La EstaciÃ³n BiolÃ³gi ca, Monteverde, Costa Rica the 5 th 11 th of November, 2005. High elevation: N= 178; Low elevation N=121. 0 10 20 30 40 50 60 70 80 1 2 3 4 5 Test Site At Each Elevation # of Individuals High Elevation 1700m-1800m Low Elevation 1500m-1600m Li ght Light Bucket Funnel Approx. 20 cm Approx. 0.5 m Approx. 1m
Figure 4. The number of individuals found from each family at each elevation al range . Diversity has found to be higher at the low elevation gradient in c omparison to the high elevational range Low: HÂ€ = 1.88; E = 0.82; High: HÂ€ = 1.79; E = 0.75. Each elevation al range was shown to be independent from one another in abundance and richness df = 1; abundance: X 2 = 10.87 , p<0.05 ; richness: X 2 = 5 , p<0.05 . Samples taken from the Monteverde cloud forest at La EstaciÃ³n BiolÃ³gica , Monteverde Costa Rica, 5 th 11 th of November, 2005. Table 1. A comparison of the average number of familie s within an elevation al range , Â‚, the number of families total sampled from each elevation al range , Â…, the difference among the families at each elevation al range , Â, and the habitat range that the families display at each elevation al range , 1/Â. Analyzed for c oleopteran samples take n from the cloud forest at La EstaciÃ³n BiolÃ³gica, Monteverde, Costa Rica , 5 th 11 th of November, 2005 . 0 10 20 30 40 50 60 Scarabaeidae Cantharidae Oedemeridae Curculionidae Ptilodactylidae Chrysomelidae Elateridae Cerambycidae Lycidae Silphidae Carabidae Tenebrionidae Hydroscaphidae Coleopteran Family # of Individuals High Elevation 1700m-1800m Low Elevation 1500m-1600m Location Â‚ Â… Â Habitat Breadth 1/Â High 5.6 11 0.78 1.28 Low 6.4 10 0.98 1.02