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Habitat preference of Leptonema sp. (Trichoptera: Hydropsychidae) on tropical waterfalls

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Title:
Habitat preference of Leptonema sp. (Trichoptera: Hydropsychidae) on tropical waterfalls
Translated Title:
Preferencia del hábitat de Leptonema sp. (Trichoptera: Hydropsychidae) en las cataratas tropicales ( )
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Book
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English
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Hamm, Aaron
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Subjects / Keywords:
Invertebrates   ( lcsh )
Waterfalls   ( lcsh )
Costa Rica--Puntarenas--Monteverde Zone--San Luis   ( lcsh )
Invertebrados
Cataratas
Costa Rica--Puntarenas--Zona de Monteverde--San Luis
Tropical Ecology Spring 2010
Ecología Tropical Primavera 2010
Genre:
Reports   ( lcsh )
Reports

Notes

Abstract:
According to Wiggins & Mackay (1978), most Trichoptera live in cases that they have made; there are several species that attach their cases to rocks and feed from the current and others that live in the gravel of the stream. Still, there are others that are located in the areas behind rocks where there is not as much current; most Trichoptera are restricted to cool lotic waters (Wiggins & Mackay 1978b). With such variability in habitat choices available for Trichoptera, it is evident that wherever a habitat is chosen it needs to be the right one. In this study a species of Trichoptera called Leptonema sp. are surveyed to find if water speed across the three different regions of a waterfall effect their distribution. There was no relationship found between Leptonema abundance and height of the waterfall. When the abundance of Leptonema per rock was regressed with the surface area of the rock (mm3) no significant difference was found. When the abundance means for each region were compared there was no significant difference between the above and below region, however both of those regions were marginally different from the crest, which had the most individuals. It was concluded that the Leptonema prefer the crest region because it is there that the fastest water flow occurs. This study is important because it allows an area of tropical stream ecology that has been studied little, to be investigated. The conservation implications of this study are long reaching. The ability to examine streams for the presence or absence of certain macroinvertebrates offers an opportunity to test the water quality of untrammeled lengths of stream, as certain kinds are useful as indicator species.
Abstract:
Según Wiggins & Mackay (1978), la mayoría de los Tricopteros viven en refugios que ellos mismos construyen, existen varias especies que adhieren sus refugios a rocas y se alimentan con las corrientes y otros que viven en el suelo de las quebradas. Además existen otras que se encuentran en las áreas detrás de las rocas en las cuales no hay mucha corriente; la mayoría de los Tricopteros están restringidos a las aguas frías loticas (Wiggins & Mackay 1978b). Con esta gran variabilidad en hábitats disponibles para los Tricópteros, es evidente que cada hábitat escogido debe ser el correcto. En este estudio la especie Leptonema sp. fue estudiada para determinar si la velocidad del agua en tres regiones diferentes en una cascada afecta su distribución. No hay relación entre la abundancia de Leptonema y el tamaño de la cascada. No se encontró relación entre la abundancia de Leptonema y el área de la roca. Cuando se comparó la abundancia entre las regiones de arriba y debajo de la catarata no se encontró ninguna diferencia, sin embargo ambas regiones son marginalmente diferentes de la cresta, la cual posee la mayoría de los individuos. Se concluye que Leptonema prefiere la región de la cresta porque es donde el agua fluye más rápido. Este estudio es importante debido a que abarca un área de la ecología de quebradas poco estudiadas con anterioridad. Las implicaciones conservacionistas de este estudio son de largo alcance. La capacidad de examinar la presencia o ausencia de ciertos macroinvertebrados ofrece una oportunidad de probar la calidad del agua en las quebradas, y ciertas especies son útiles como especies indicadoras.
Language:
Text in English.
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Born Digital

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University of South Florida Library
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University of South Florida
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usfldc doi - M39-00303
usfldc handle - m39.303
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According to Wiggins & Mackay (1978), most Trichoptera live in cases that they have made; there are several species that attach their cases to rocks and feed from the current and others that live in the gravel of
the stream. Still, there are others that are located in the areas behind rocks where there is not as much current; most Trichoptera are restricted to cool lotic waters (Wiggins & Mackay 1978b). With such variability in habitat choices available for Trichoptera, it is evident that wherever a habitat is chosen it needs to be the right one. In this study a species of Trichoptera called Leptonema sp. are surveyed to find if water speed across the three different regions of a waterfall effect their distribution. There was no
relationship found between Leptonema abundance and height of the waterfall. When the abundance of Leptonema per rock was regressed with the surface area of the rock (mm3) no significant difference was
found. When the abundance means for each region were compared there was no significant difference between the above and below region, however both of those regions were marginally different from the crest, which had the most individuals. It was concluded that the Leptonema prefer the crest region because it is there that the fastest water flow occurs. This study is important because it allows an area of tropical stream ecology that has been studied little, to be investigated. The conservation implications of this study are long reaching. The ability to examine streams for the presence or absence of certain macroinvertebrates
offers an opportunity to test the water quality of untrammeled lengths of stream, as certain kinds are useful as indicator species.
Segn Wiggins & Mackay (1978), la mayora de los Tricopteros viven en refugios que ellos mismos construyen, existen varias especies que adhieren sus refugios a rocas y se alimentan con las corrientes y otros que viven en el suelo de las quebradas. Adems existen otras que se encuentran en las reas detrs de las rocas en las cuales no hay mucha corriente; la mayora de los Tricopteros estn restringidos a las aguas fras loticas (Wiggins & Mackay 1978b). Con esta gran variabilidad en hbitats disponibles para los Tricpteros, es evidente que cada hbitat escogido debe ser el correcto. En este estudio la especie Leptonema sp. fue estudiada para determinar si la velocidad del agua en tres regiones diferentes en una cascada afecta su distribucin. No hay relacin entre la abundancia de Leptonema y el tamao de la cascada. No se encontr relacin entre la abundancia de Leptonema y el rea de la roca. Cuando se compar la abundancia entre las regiones de arriba y debajo de la catarata no se encontr ninguna diferencia, sin embargo ambas regiones son marginalmente diferentes de la cresta, la cual posee la mayora de los individuos. Se concluye que Leptonema prefiere la regin de la cresta porque es donde el agua fluye ms rpido. Este estudio es importante debido a que abarca un rea de la ecologa de quebradas poco estudiadas con anterioridad. Las implicaciones conservacionistas de este estudio son de largo alcance. La capacidad de examinar la presencia o ausencia de ciertos macroinvertebrados ofrece una oportunidad de probar la calidad del agua en las quebradas, y ciertas especies son tiles como especies indicadoras.
546
Text in English.
650
Invertebrates
Waterfalls
Costa Rica--Puntarenas--Monteverde Zone--San Luis
4
Invertebrados
Cataratas
Costa Rica--Puntarenas--Zona de Monteverde--San Luis
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Ecologa Tropical Primavera 2010
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Habitat Preference of Leptonema sp. (Trichoptera: Hydropsychidae) on Tropical Waterfalls. Aaron Hamm Department of Outdoor Recreation, Central Michigan University ABSTRACT According to Wiggins & Mackay (1978), most Trichoptera live in cases that t hey have made; there are several species that attach their cases to rocks and feed from the current and others that live in the gravel of the stream. Still, there are others that are located in the areas behind rocks where there is not as much current; mos t Trichoptera are restricted to cool lotic waters (Wiggins & Mackay 1978b). With such variability in habitat choices available for Trichoptera, it is evident that wherever a habitat is chosen it needs to be the right one. In this study a species of Tricho ptera called Leptonema sp. are surveyed to find if water speed across the three different regions of a waterfall effect their distribution. There was no relationship found between Leptonema abundance and height of the waterfall. When the abundance of Lepto nema per rock was regressed with the surface area of the rock (mm 3 ) no significant difference was found. When the abundance means for each region were compared there was no significant difference between the above and below region, however both of those re gions were marginally different from the crest, which had the most individuals. It was concluded that the Leptonema prefer the crest region because it is there that the fastest water flow occurs. This study is important because it allows an area of tropica l stream ecology that has been studied little, to be investigated. The conservation implications of this study are long reaching. The ability to examine streams for the presence or absence of certain macroinvertebrates offers an opportunity to test the wat er quality of untrammeled lengths of stream, as certain kinds are useful as indicator species. RESUMEN Segn Wiggins & Mackay (1978), la mayora de los Tricopteros viven en refugios que ellos construyen, existen varias species que adhieren sus ref ugios a rocas y se alimentan con las Corrientes y otros que viven en el suelo de las quebradas. Adems existen otras que se encuentran en reas detrs de rocas en las cuales no hay mucha corriente; la mayora de los Tricopteros estn restringidos a aguas f ras lticas (Wiggins & Mackay 1978b). Con esta gran variabilidad en hbitats disponibles para los Tricpteros, es evidente que cada hbitat escogido debe ser el correcto. En este estudio la especie Leptonema sp. fue estudiada para determinar si la veloc idad del agua en tres regiones diferentes en una cascada afecta su distribucin. No hay relacin entre la abundancia de Leptonema y el tamao de la cascada. No se encontr relacin entre la abundancia de Leptonema y el rea de la roca. Cuando se comparo la abundancia entre las regiones de arriba y debajo de la catarata no se encontr ninguna diferencia, sin embargo ambas regiones son marginalmente diferentes de la cresta, la cual posee la mayora de los individuos. Se concluye que Leptonema prefiere la regin de la cresta porque es donde el agua fluye ms rpido. Este estudio es importante debido a que abarca un rea de la ecologa de quebradas poco estudiada con anterioridad. Las implicaciones conservacionistas de este estudio son de largo alcance. L a capacidad de examinar la presencia o ausencia de ciertos macroinvertebrados ofrece una oportunidad de probar la calidad del agua en las quebradas, y ciertas especies son tiles com especies indicadoras.

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INTRODUCTION In the past, numerous s tudies on macro invertebrates have been conducted with an emphasis on habitat selection (Urbanic et al. 2005), habitat structure (Crisci Bispo et al. 2007), and even food preferences (Slack 1936). However, little is known on macroinvertebrate selection of habitat along waterfalls. Along the course of a river where a waterfall might be found with macroinvertebrates in it, there may be differences in the speed of the water flow. Chen and Zhang et al. (2004) noted that there are abrupt hydrological changes tha t occur at waterfalls. In agreement with Georgian & Thorp (1992), macroinvertebrates from the family Hydropsychidae have a reputation for preferring habitats with a firm and large substrate, and a high water flow velocity. The amount of dissolved ox ygen in the water also may play a role in where a macroinvertebrate prefers their habitat. According to Hauer & Resh (1996) nearly all stream organisms are sensitive to oxygen concentration. In a study by Connolly & Crossland (2004), examining the effects of dissolved oxygen levels on macroinvertebrates in tropical streams; it was found that in taxa other than mayflies, death occurred when the dissolved oxygen levels fell below 8% saturation. The macro invertebrate of focus for this study was Leptone ma sp. (Trichoptera: Hydropsychidae). Leptonema are a tropical species of the Caddisfly. Hydropsychidae can be found along the different surfaces of rocks in stream riffles; some of them roam across the rock while others stay in fixed shelters on the under side (Wiggins & Mackay 1978c). Overall, there is a wide range of habitats. Despite all the information that is known about the habitat location of Leptonema there has yet to be a study that I have found that examines the selection of habitat of Lepto nema the change in the speed of water flow along a waterfall affected the distribution of Leptonema. MATERIALS AND METHODS STUDY SITE This study was conducted in the San Luis Valley of Costa Rica during the end of the dry season, from the beginning of April to the beginning of May 2010. The site of the study was the Finca La Catarata at the San Luis River. The San Luis River is an ideal study site because it is compose d of rocky terraces with many waterfalls along its course. The San Luis River resides in an area of Premontane wet forest. According to Nadkarni & Wheelwright (2000), the Premontane life zone of the San Luis Valley is highly seasonal. The altitude of the s ection of river that was studied is between 1000 1200 m above sea level.

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TESTING AND SITE SELECTION Waterfalls were examined for the presence or absence of Leptonema Waterfalls were defined as areas along the stream where water was f alling with a vertical incline. At the base there needed to be frothing water that was all or partially white. Three regions were tested at each waterfall. The first region was below the waterfall. The second region was at the crest of the waterfall. The crest of the waterfall was the area that the water fell from into the below region. The third region was above the waterfall. Waterfalls along the river were selected based on whether or not they possessed all three regions. In addition, each region ha d to be large enough to allow for a one meter transect to be placed along the river bottom. Each region had to be accessible on foot and contain at least four lift able rocks of at least 3 cm by 4 cm. METHODOLOGY Upon selecting a study site, a 1m t ransect was placed horizontally across the river bottom. Any rock that touched the transect line, was lift able, and larger than roughly 3 ruler. Each rock was then visually inspected for the presence or absence of Leptonema If the shelter of a Leptonema was found with nothing inside it, it was assumed that the Leptonema was away but would return and it was still noted. A full measurement of waterfall height was record ed from the crest region (the uppermost point of where the water fell), to the surface of the frothing water below. Microsoft Excel and a statistics program called JUMP were used for graphing and data processing. RESULTS A total of 60 Leptonema sp were located in 21 waterfalls over an approximate river gradient of 2.5 km. In all, 447 rocks were measured for their length and width. The smallest rock found in terms of surface area was 47.88 cm 3 The largest rock found in terms of surface area was 339. 13 cm 3 There was no relationship found between the number of Leptonema on a rock and the surface area of a rock (figure 1). The highest mean abundance of Leptonema was found in the crest (figure 2). For the above, crest, and below regions of the wate rfalls, the counts of Leptonema found were: above 17, crest 29, below 14. The tallest waterfall tested was 1m, while the smallest waterfall tested was 22 cm. When the abundance of the below regions of the waterfalls was regressed with the height of the wa terfalls, there was no significant relationship between the two variables (figure 3).

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Figure 1. Total Leptonema found per rock to the surface area of the rock (cm 3 ) for 21 waterfalls in the San Luis River, San Luis, Costa Rica. Linear Regression, F = 0. 017, p = 0.90. Figure 2. Mean abundance of Leptonema (+/ 1 SD) to waterfall zones from 21 waterfalls in the San Luis River, San Luis, Costa Rica. Asterisks above, the above and below regions indicate that these regions were not significantly differen t from each other, however they were marginally significant from the crest. (K W: chi= 5.82 df = 2, p = 0.05)

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Figure 3. Abundance of Leptonema for region below the waterfall (N = 21), in the San Luis River, San Luis, Costa Rica. Linear Regression, F = 0 .52, p = 0.48. DISCUSSION There were more Leptonema sp. found in the crest region of all the waterfalls than any other region. Something about the crest of the waterfalls caused a larger abundance of Leptonema Abundance of Leptonema was not related to the surface area of the rocks found in the waterfalls. The abundance of Leptonema in the below region was not related to the height of the waterfalls. The fact that more Leptonema were found in the crest region than any other region suggests that an un determined variable such as water speed, could explain why this occurred. The observations that were made in the field suggest subject to the laws of gravity as it falls downwards. According to Chen & Zhang et al. (2004), water velocity and the exchange between air and water increase greatly at waterfalls. This could explain why the Leptonema choose to procure a habitat in the crest region. Due to higher speed s of water flow they view this region as a possibility to gather more food. In a study examining the effects of microhabitat selection on feeding rates of Hydropsychidae (Georgian & Thorp 1992), it was found that areas of high water flow were chosen by 96% of Hydropsychid larvae as habitat in colonizing artificial moss substrates. Another study that examined three species of Trichoptera in a stream in Canada, found that they preferred shallow and fast moving water with large moss covered rocks (Williams & H ynes 1973). The implications of this study can serve as a scientific endowment in a very specific area of ecology that seems to have not been studied very much. It can also serve as a

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primer for conservation of streams and rivers in the tropics. Acc ording to Goodnight (1973), when an aquatic organism is present it can provide indications of the condition of the stream. As deforestation continues in Central America, though it is not as much as in the Amazon, the importance of being able to monitor str eams and rivers for water quality testing for human consumption will likely rise. ACKNOWLEDGEMENTS Miriam Salazar my Tico Mother, helped to make this study possible by providing me with a lunch every day for my field work. My gratitude goes to the Finca la Cattarata for allowing me to conduct research on their land several days a week. Also, to Pablo Allen for being the advisor of this project and helping me conduct the statistics and form the basic methodology. LITERATURE CITED Chen, J., D.D. Zhang, S. Wang T. Xiao and R. Haung. 2004. Factors Controlling Tufa Deposition in Natural Waters at Waterfall Sites. Journal of Sedimentary Geology: 166: 353 366. Clarke, A., R.M. Nally, N. Bond and P.S Lake. 2008. Macroinvertebrate Diversity in Headwater Streams a Review. Journal of Freshwater Biology: 53: 1707 1721. Connolly, N.M. and M.R. and Crossland. 2004. Effect of Low Dissolved Oxygen on Survival, Emergence, and Drift of Tropical Stream Macroinbvertabrates. Journal of the North American Benthological Society. 23 : 251 270. Crisci Bispo, V. L., P. C. Bispo and C. G Froehlich. 2007. Ephemeroptera, Plecoptera and Trichoptera assemblages in a mountain stream of the Atlantic Rainforest from Southeastern Brazi l. Revista Brasileira de Zoologia 24: 545 551. Georgian, T. and J. H. Thorp. 1992. Effects of Microhabitat Selection on Feeding Rates of Net Spinning Caddis Fly Larvae. Journal of Ecology: 73: 229 240. Goodnight, C.J. 1973. The Use of Aquatic Macroi nvertebrates as Indicators of Stream Pollution. Transactions of the American Microscopical Society. Haber, W.A. 2000. Plants and Vegetation. In: Monteverde N.M., Nadkarni and N.T., Wheelwright, eds. Oxford University Press, New York, pp 42 43 Hauer, R. F. and V. H. Resh. 1996. Benthic Macroinvertebrates. In: Methods in Stream Ecology, R. F. Hauer and G. A. Lamberti, eds. Academic Press, San Diego, CA, pp 342 343. Hilsenhoff, W. 1991. Diversity and Classification of Insects a nd Collembola. In: Ecology and Classification of North American Freshwater Invertebrates, J.P., Thorp and A.P., Covich, eds. Academic Press, San Diego, CA, p 609. Slack, H. D. 1936. The Food of Caddis Fly (Trichoptera) Larvae. Journal of Animal Ecology 5: 105 115. Urbanic, G.,M. J. Toman and C. Krusnikz. 2005. Microhabitat Type Selection of Caddisfly Larvae (Insecta: Trichoptera) in a shallow stream. Hydrobiologia 541: 1 12. Wiggins, B.G. and Mackay, J.M. 1978. Some Relationship s between Systematics and Trophic Ecology in Neartic Aquatic Insects, with Special Reference to Trichoptera. Ecology 59: 1211 1220.