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Los hongos de la estacin lluviosa de la vertiente del Caribe en Monteverde, Costa Rica
Wet season macrofungi of the Caribbean slope in Monteverde, Costa Rica
Despite its small size, Costa Rica harbors high fungal diversity. Although very little is known about fungi, they are beneficial to humans in the medicinal field and are also known to be important recyclers of nutrients in ecosystems. Their importance in our lives justifies further research concerning fungal communities. The purpose of our study is to investigate the community composition and species richness in a lower montane rain forest on the Caribbean slope at Monteverde, Costa Rica. Between the range of 1550 m and 1850 m, we recorded abundance of different morphological forms, substrate types and also compared species richness to canopy coverage, elevation, and pH level. A total of 40 morphospecies were found, of which 50% were toadstools. Additionally, 55% were found growing on soil substrates. We found no substantial correlation between canopy cover and species richness. There was a statistically significant trend for lower species richness at higher elevations (Spearman Rank Test, Rho = -0.80, p = 0.03, n = 7), and a nearly significant trend for greater species richness with increasing pH levels (Spearman Rank Test, Rho = -0.70, p = 0.08, n = 7). We found that as distance between transects increased, there was a trend for lowered similarity in fungal species composition (Spearman Rank Test, Rho = 0.36, p = 0.11, n = 21). Variability in Caribbean slope fungal communities is most likely caused by differences in abiotic (e.g. temperature, soil pH, wind, light availability) and biotic factors. Different tree communities and/or volcanic conditions of the area may control these factors.
A pesar de su pequeo tamao, Costa Rica alberga una diversidad alta de hongos. Aunque se sabe muy poco acerca de los hongos, se sabe que son beneficiosos para los seres humanos en el campo de la medicina y son conocidos tambin por ser importantes recicladoras de nutrientes en los ecosistemas. Su importancia en nuestras vidas justifica ms investigacion con respecto a las comunidades de los hongos. El propsito de este estudio es investigar la composicin de la comunidad y la riqueza de especies en un bosque lluvioso montano bajo en la vertiente del Caribe en Monteverde, Costa Rica.
Text in English.
Fungal communities--Costa Rica--Puntarenas--Monteverde Zone
Forest fungi--Costa Rica
Cloud forest ecology--Costa Rica
Comunidades de hongos--Costa Rica--Puntarenas--Zona de Monteverde
Hongos del bosque--Costa Rica
Ecologa del bosque nuboso--Costa Rica
Tropical Ecology 2006
Ecologa Tropical 2006
t Monteverde Institute : Tropical Ecology
1 Wet season macrofungi of the Caribbean slope in Monteverde, Costa Rica Oliver Herbst Aldis Kurmis Department of Environmental Science, University of Colorado at Boulder Department of Geography, University of Minnesota ABSTRACT Despite its small size, Costa Rica harbors high fungal diversity. Although very little is known about fungi, they are beneficial to humans in the medicinal field and are also known to be important recyclers of nutrients in ecosystems. Their importance in our lives justifies furth er research concerning fungal communities. The purpose of our study is to investigate the community composition and species richness in a lower montane rain forest on the Caribbean slope at Monteverde, Costa Rica. Between the range of1550 m and 1850 m, we recorded abundance of different morphological forms, substrate types and also compared species richness to canopy coverage, elevation, and pH level. A total of 40 morphospecies were found, of which 50% were toadstools. Additionally, 55% were found growing on soil substrates. We found no substantial correlation between canopy cover and species richness. There was a statistically significant trend for lower species richness at higher elevations Spearman Rank Test, Rho = 0.80, p = 0.03, n = 7, and a nearly significant trend for greater species richness with increasing pH levels Spearman Rank Test, Rho = 0.70, p = 0.08, n = 7. We found that as distance between transects increased, there was a trend for lowered similarity in fungal species composition Spea rman Rank Test, Rho = 0.36, p = 0.11, n = 21. Variability in Caribbean slope fungal communities is most likely caused by differences in abiotic e.g. temperature, soil pH, wind, light availability and biotic factors. Different tree communities and/or vol canic conditions of the area may control these factors. RESUMEN A pesar de su pequeÃ±o tamaÃ±o, Costa Rica alberga una diversidad alta de hongos. Aunque se sabe muy poco acerca de los hongos, se sabe que son beneficiosos para los seres humanos en el campo de la medicina y son conocidos tambiÃ©n por ser importantes recicladores de nutrimentos en los ecosistemas. Su importancia en nuestras vidas justifica mÃ¡s investigaciÃ³n con respecto a las comunidades de hongos. El propÃ³sito de este estudio es investigar la composiciÃ³n de la comunidad y la riqueza de especies en un bosque lluvioso montano bajo en la ladera Caribe de Monteverde, Costa Rica. Entre el Ã¡mbito de 1550 m y 1850 m, se registrÃ³ la abundancia de diferentes for mas morfolÃ³gicas, tipos de sustra tos y tambiÃ©n se comparÃ³ la riqueza de especies con respecto a la cobertura del dosel, a la elevaciÃ³n, y al nivel del pH. Se encontrÃ³ un total de 40 morfoespecies, de las cuales 50% fueron hongos tipo sombrilla. Adicionalmente, se encontrÃ³ que un 55% estaban creciendo en sustratos con suelo. No encontramos una correlaciÃ³n sustancial entre la cobertura del dosel y la riqueza de las especies. Hubo una tendencia estadÃsticamente significativa para una menor riqueza de especies en elevaciones altas Test de Spe arman Rank, Rho = 0.80, p = 0.03, n = 7, y una tendencia casi significativa para una riqueza mayor de especies con niveles de pH en aumento Test de Spearman Rank, Rho = 0.70, p = 0.08, n = 7. Encontramos que entre mÃ¡s aumenta la distancia entre los transeptos , hubo una tendencia en la disminuciÃ³n de la similitud en la composiciÃ³n de las especies de hongos Test de Spearman Rank, Rho = 0.36, p = 0.11, n = 21. La variabilidad en las comunidades de hongos en la ladera Caribe es causada lo mÃ¡s probable mente por dife rencias en factores abiÃ³ticos e.g. temperatura, suelo, pH, viento, disponibilidad de luz y biÃ³ticos. Diferentes comunidades de Ã¡rboles y/o condiciones volcÃ¡nicas pueden controlar estos factores.
2 INTRODUCTION Fungi are of great ecologica l and anthropocentric importance but are one of the most understudied kingdoms. Fungi, along with bacteria, are major recyclers within the environment. They are capable of taking complex organic compounds and breaking them down into less complex building blocks, which can then be utilized by other organisms. Without fungi and bacteria, nutrients in dead and organic matter would lay trapped in dead material Aurora 1996. Mycorrhizal fungi have complex relationships crucial to nutrient uptake of tropical plants Janos 1983. In the medical world, fungi have been used in AIDS research, to combat cancer, and to produce penicillin Mata 1999. Costs associated with wood rot and crop loss from fungi can be astronomical Alexopoulos 1996. To reap their ben efits and control their damage, fungi must be first identified and their ecological relationships understood. There are approximately 100,000 identified species of fungi worldwide. This number is miniscule when compared to the 1.5 million species that exp erts believe may exist Hawksworth 1991. The most notably understudied areas of the world are tropical and subtropical regions Alexopoulos 1996. In Costa Rica roughly two thousand species have been identified but an estimated 40,000 to 70,000 species are believed to inhabit this small country Mata 1999. With the numerous benefits associated with fungi, it is not difficult to justify further research concerning fungal communities. In the Monteverde area of Costa Rica a number of studies have bee n done on fungal communities along the Pacific slope e.g., McCracken 1995, Wales 1998, Ciocca 2000, Herz 2004. However, the Caribbean slope remains largely neglected and both abiotic and biotic components of this slope indicate that fungal communities w ould differ from those found on the Pacific slope. On the Caribbean slope rainfall is consistent throughout the year, creating a nearly aseasonal climate. This differs from the Pacific slope weather system, which includes a five to six month dry season. There is also variation in the vegetation harbored on the two slopes, as species composition differs profoundly. Also, while the Pacific slope has a mix of evergreen species and deciduous trees, the trees of the Caribbean slope are all evergreen Haber 20 00. Vegetation may regulate the amount and type of resources available for fungal communities, and influence topsoil properties. Fungal communities are also sensitive to variations in precipitation, for example Polypores are less susceptible to desiccati on than other fungal species Hering 1966, Watling 1981, GuzmÃ¡n 1994, Loreau 2000, all in: Munguia et al. 2005, Ciocca 2006. These differences are likely large enough to create differences in fungal community composition. It is because of this variation that we think a study of fungal communities on the Caribbean slope is worthwhile. The purpose of our study is to investigate the community composition and species richness in a lower montane rain forest on the Caribbean slope at Monteverde, Costa Rica. W e link our community parameters to elevational gradients, pH level, species richness, and canopy coverage. By looking at elevational gradients in relation to species richness, soil pH levels and canopy coverage, we can investigate possible correlations be tween them. In addition to the above, we provide basic descriptions of the Caribbean fungal community in terms of the morphological forms, and the substrates used by these fungi.
3 MATERIALS AND METHODS Starting from the Monteverde Biological Station, we walked along the Sendero Principal in the direction of the Squatter s Shack, located on the ridge of the Continental Divide. From there an unmarked trail was followed down the Caribbean slope. At 1550 m on the Caribbean slope, four separate, twenty meter t ransects were drawn at approximately a constant elevation. For each transect we recorded canopy coverage with a spherical densitometer , and soil pH level using a pH meter. Any macrofungi encountered within t wo meters on either side of the transect was phot ographed, and information such as morphological form and substrate type were recorded. Transects were studied in pairs parallel to one another to insure there was no crossing of transects or repeat specimens recorded. Sets of transects were walked on opp osite sides of the trail to further insure there was no crossover between data sets. Transects were laid every fifty meters, up to 1850 m above sea level. In total, data were taken at seven different elevations. We calculated beta diversity between all possible pairs of transects. The equation we used was: Ã°g = Ã°a * Ã°b * number of habitats, where Ã°g = total number of species in two transects, Ã°a = the average species in the two transects, and the number of habitats is two transects. RESULTS A total of 40 m orphospecies were found on the seven transects. We found seven different growth forms and recorded the relative abundance of each Figure 1. Toadstools and shelf fungi were the most common, comprising 1/3 of the total data set. Macrofungi were observed gr owing on three different substrates: dead wood, soil, and leaf litter Figure 2. Fourteen morphospecies were found on dead wood, twenty two on soil and four on leaf litter. We compared species richness per transect elevation to canopy coverage, elevat ion and pH level. We found a positive trend for greater species richness with more canopy cover, although it was not significant Spearman Rank Test, Rho = 0.58, p = 0.17, n = 7, Figure 3. There was a statistically significant relationship between specie s richness and elevation Spearman Rank Test, Rho = 0.80, p = 0.03, n = 7, Figure 4. As elevation increased, species richness decreased. There was also nearly a statistically significant negative correlation between species composition and pH level Spea rman Rank Test, Rho = 0.70, p = 0.08, n = 7, Figure 4. As elevation increased, pH level also increased. Lastly, we measured beta diversity values of fungal communities compared to distance between elevations. We found that as distance between transects increased, there was a trend for lowered similarity in fungal species composition Spearman Rank Test, Rho = 0.36, p = 0.11, n = 21, Figure 5. These results were not statistically significant.
4 DISCUSSION In our study we found 40 morphospecies of macr ofungi in total. The most common morphological type was toadstool fungus, which comprised 50% of our specimens, while shelf fungi only comprised 25%. This differs from a previous study done by Ciocca 2000, where she found approximately 37% of her specime ns to be shelf fungi. This difference could be understood by the fact that Ciocca conducted her study during the dry season in Monteverde; shelf fungi are better adapted to drier conditions, which could explain why she would have found a larger proportion of these compared to other fungal morphologies on the Pacific slope. In contrast, fungi on the seasonal Caribbean slope, which has a relatively higher amount of precipitation, would not harbor such a large fraction of desiccation resistant growth forms. The fungal community of the Caribbean slope was observed mainly on soil substrates 55% of our specimens, which differed from past studies on both the Pacific and Atlantic slopes. Williams 2006 found the majority of her specimens, 83.3%, growing on dea d wood substrate. Her study was conducted during the dry season, a period that receives little wind borne mist on the Pacific slope, which would explain why a higher percentage of her specimens might have been restricted to moisture absorbent, dead wood su bstrates Haber 2000. Another past study, conducted by Herz 2004 on the Caribbean slope, found only 10% of the recorded specimens on soil substrate, and 58% on dead wood. This pattern could be explained by a variation in the amount of dead wood availabl e to fungal communities at different times. Tree falls are both spatially and temporally patchy. For example, a storm that caused an unusual amount of tree falls could have occurred previous to the Herz study, thus providing macrofungi with a larger amount of dead wood substrate than available during our survey. We also found species richness to vary greatly between transects, with anywhere from three to eleven species at each. We did not find this variation to be significantly related to canopy coverage. This differs from a past study in which a trend for greater species richness in forested areas as opposed to light gaps was observed McCracken 1995. An explanation could be that McCracken was studying more extreme differences in canopy cover conditions complete canopy cover versus completely open light gaps, while our canopy coverage ranged from 54 to 82 %. Hence the difference in results between the two studies could be accounted for by differences in the range of canopy coverage considered. We did, h owever, find a significant relationship between species richness and elevation, with fewer species at higher elevations. Herz 2004 ruled out the possibility of variability in dead wood characteristics e.g. decay and moisture of fallen logs at different elevations on the Caribbean slope as being the cause of this relationship. She found that the amount of decay and moisture content of fallen logs did not vary with changes in elevation. Ciocca 2000 found no correlation between species richness and eleva tion. However, our results suggest that soil pH could influence how many species are fruiting at any given time. As elevation increased, pH increased and species richness decreased. Possible explanations for why soil acidity would decrease with increasing elevation include variable forest composition and patchiness of volcanic ash. Different species of trees, which have varying elevational ranges, have diverse effects on soil chemistry. It is possible that lower elevations contain assemblages of trees that increase
5 the acidity of the soil. Volcanoes in close proximity to Monteverde, such the highly active Arenal, may also have an effect on pH level. After an eruption, volcanic ash, which is basic, would fall on the tops of the surrounding mountains, thereby changing the soil pH of that area. Lastly, we found that as distance increases between transects, there is less similarity in fungal community composition. This increasing variability in communities would most likely be caused by greater differences in abi otic e.g. temperature, soil pH, wind, light availability and biotic e.g. tree communities factors. However, Ciocca 2000 did not find a similar trend in her study of the Caribbean slope. One possible reason for this is that she conducted her study ove r a longer period of time and was able to collect a larger sample size. Adding to this sample size is essential for drawing any definitive conclusions. Future studies concerning the variability of species composition as a factor of distance would be useful in determining which abiotic/biotic factors, if any, influence fungal communities. ACKNOWLEDGEMENTS Foremost, we would like to thank Cam for her inexhaustible patience and Tom for providing us with mental reprieves when they were needed most. We would also like to give a special thanks to Karen Masters for her guidance, support, and incredible amount of work in formatting and carrying out this project. Lastly, we would like to thank Carmen Rojas for her advice and translation skills. LITERATURE CITED ALEXOPOULOS, C.J., MIMS, C.W., BLACKWELL, M. 1996. Introductory Mycology , 4 th ed. John Wiley & Sons, Inc., Toronto, pg. 6. ARORA, D. 1986. Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi . Ten Speed Press, Berkeley, California, pg. 6. CIO CCA, E. 2000. Fungal species richness on an elevational and longitudinal gradient on the continental divide. Spring. CIEE Tropical Biology Program, pp. 1 11. HABER, W.A. 2000. Chapter 3: Plants and Vegetation. In: Monteverde: Ecology and Conservation of a Tropical Cloud Forest . Nadkarni, N. and Wheelwright, N. eds. Oxford University Press, Oxford, New York, pg. 41. HAWKSWORTH, D. 1991. The Fungal Dimension of Biodiversity: Magnitude, Significance and Conservation. Mycol. Res. 95: pp. 641 655. HERING, T.F. 1 966. The terricolous higher fungi of four Lake District Woodlands. Trans. British Mycol. Soc. 49 : 369 383. HERZ, K. 2004. Fungal species richness in relation to substrate penetrability and moisture on the Atlantic slope. Spring 2004. CIEE Tropical Biology Program, pp. 98 107. JANOS, D.P. 1983. Tropical Mycorrhizae, Nutrient Cycles and Plant Growth. In: Tropical Rainforest Diversity and Management . Sutton, S.L., Whitmore, T.C. and Chadwick, A.C. eds. Blackwell Scientific Publications, Oxford, England, pg. 49 8. LOREAU, M. 2000. Biodiversity and ecosystem functioning: recent theoretical advances. Oikos 91 : 3 17. MATA, M. 1999. Macrohongos de Costa Rica , Vol. 1. INBio, Santo Domingo de Heredia, Costa Rica, pp. 11, 16 17. McCRACKEN, T. 1995. Diversity of fleshy f ungi in gaps and forests. Spring CIEE Tropical Biology Program, pp. 237 244. MUNGUIA, P., GUZMAN, G., RAMIREZ GUILLEN. 2005. Seasonal community structure of macromycetes in Veracruz, Mexico. Ecography 28 : 1 9.
6 WALES, M. 1998. Fungal abundance, species ric hness, and diversity of five life zones of Monteverde during two seasons. Fall CIEE Tropical Biology Program, pp. 113 120. WATLING, R. 1981. Relationships between macromycetes and the development of higher plant communities. The fungal community. Its organ ization and role in the ecosystem . Wicklow, D.T. and Carroll, G.C. eds. Dekker, New York, pp. 427 458. WILLIAMS, S. 2006. Dry season macrofungi of the Monteverde Reserve. Spring CIEE Tropical Biology Program, pp. 1 5.
7 0 5 10 15 20 25 Toadstool Cup Shelf Puffball Hanging Bell Coral Club Morphological Form Number of Specimens Figure 1. The number of specimens found of each morphological form on the Caribbean slope of the Continental Divide near Monteverde, Costa Rica from 1550 1850 m. Toadstools comprised 50% of the 40 morphospecies found. 0 5 10 15 20 25 dead wood soil leaf litter Substrate Type Number of Specimens Figure 2. Frequency of fungi species found on various substrates on the Caribbean slope of the Continental Divide near Monteverde, Costa Rica from 1550 1850 m. More species were found on soil and dead wood substrates than leaf litter. Out of the 40 morphospecies, 55% were found on soil substrate.
8 0 2 4 6 8 10 12 50 55 60 65 70 75 80 85 Canopy Coverage % Species Richness Figure 3. Fungal species richness compared to percent canopy coverage on the Caribbean slope. There was a positive trend for greater species richness with more canopy cover. 2 3 4 5 6 7 8 9 10 11 12 1500 1550 1600 1650 1700 1750 1800 1850 1900 Elevation m Species Richness 3 3.5 4 4.5 5 5.5 6 pH Level Figure 4. Elevation compared to fungal species richness and pH level. Solid line and empty circles refer to species richness and dashed line and solid squares refer to pH level. There was a statistically significant relationship betw een species richness and elevation. There was nearly a statistically significant negative correlation between species composition and pH level.
9 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 0 100 200 300 Distance Between Elevations m Beta Value Figure 5. Beta diversity values of fungal communities compared to distance between elevations. As distance incr eases between elevations, the lower the similarity in fungal species composition.