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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
1Wet 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 fun gal diversity. Although very little is known about fungi, they are beneficial to humans in the medicinal fiel d and are also known to be important recyclers of nutrients in ecosystems. Their importance in our li ves justifies further research concerning fungal communities. The purpose of our study is to investi gate 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 mo rphological forms, substrate types and also compared species richness to canopy coverage, eleva tion, and pH level. A total of 40 morphospecies wer e 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 signif icant trend for lower species richness at higher elevatio ns (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 T est, Rho = -0.70, p = 0.08, n = 7). We found that as dis tance between transects increased, there was a tren d for lowered similarity in fungal species composition (S pearman Rank Test, Rho = 0.36, p = 0.11, n = 21). Variability in Caribbean slope fungal communities i s 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. RESUMEN A pesar de su pequeo tamao, Costa Rica alberga un a diversidad alta de hongos. Aunque se sabe muy poco acerca de los hongos, se sabe que son benefici osos para los seres humanos en el campo de la medic ina y son conocidos tambin por ser importantes recicl adores de nutrimentos en los ecosistemas. Su importancia en nuestras vidas justifica ms investi gacin con respecto a las comunidades de hongos. E l propsito de este estudio es investigar la composic in de la comunidad y la riqueza de especies en un bosque lluvioso montano bajo en la ladera Caribe de Monteverde, Costa Rica. Entre el mbito de 1550 m y 1850 m, se registr la abundancia de diferentes f ormas morfolgicas, tipos de sustrtatos y tambin s e compar la riqueza de especies con respecto a la co bertura del dosel, a la elevacin, y al nivel del p H. Se encontr un total de 40 morfoespecies, de las cuale s 50% fueron hongos tipo sombrilla. Adicionalmente se encontr que un 55% estaban creciendo en sustratos con suelo. No encontramos una correlacin sustanci al entre la cobertura del dosel y la riqueza de las es pecies. Hubo una tendencia estadsticamente signif icativa para una menor riqueza de especies en elevaciones a ltas (Test de Spearman Rank, Rho = -0.80, p = 0.03, n = 7), y una tendencia casi significativa para una r iqueza mayor de especies con niveles de pH en aumen to (Test de Spearman Rank, Rho = -0.70, p = 0.08, n = 7). Encontramos que entre ms aumenta la distancia entre los transectos, hubo una tendencia en la dism inucin de la similitud en la composicin de las es pecies de hongos (Test de Spearman Rank, Rho = 0.36, p = 0 .11, n = 21). La variabilidad en las comunidades d e hongos en la ladera Caribe es causada lo ms probab lemente por diferencias en factores abiticos ( e.g temperatura, suelo, pH, viento, disponibilidad de l uz) y biticos. Diferentes comunidades de rboles y/o condiciones volcnicas pueden controlar estos facto res.
2 INTRODUCTION Fungi are of great ecological and anthropocentric i mportance but are one of the most understudied kingdoms. Fungi, along with bacteria, are major recyclers within the environment. They are capable of taking complex or ganic compounds and breaking them down into less complex building blocks, which can t hen be utilized by other organisms. Without fungi and bacteria, nutrients in dead and o rganic matter would lay trapped in dead material (Aurora 1996). Mycorrhizal fungi have complex relationships crucial to nutrient uptake of tropical plants (Janos 1983). I n the medical world, fungi have been used in AIDS research, to combat cancer, and to pro duce penicillin (Mata 1999). Costs associated with wood rot and crop loss from fungi c an be astronomical (Alexopoulos 1996). To reap their benefits and control their damage, fu ngi must be first identified and their ecological relationships understood. There ar e approximately 100,000 identified species of fungi worldwide. This number is miniscu le when compared to the 1.5 million species that experts believe may exist (Hawksworth 1991). The most notably understudied areas of the world are tropical and su btropical regions (Alexopoulos 1996). In Costa Rica roughly two thousand species have bee n identified but an estimated 40,000 to 70,000 species are believed to inhabit this smal l 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 s tudies have been done on fungal communities along the Pacific slope (e.g., M cCracken 1995, Wales 1998, Ciocca 2000, Herz 2004). However, the Caribbean slope rem ains largely neglected and both abiotic and biotic components of this slope indicat e that fungal communities would differ from those found on the Pacific slope. On the Cari bbean slope rainfall is consistent throughout the year, creating a nearly aseasonal cl imate. 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 slo pes, 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 eve rgreen (Haber 2000). Vegetation may regulate the amount and type of resources available for fungal communities, and influence topsoil properties. Fungal communities a re also sensitive to variations in precipitation, for example Polypores are less susce ptible to desiccation than other fungal species (Hering 1966, Watling 1981, Guzmn 1994, Lo reau 2000, all in: Munguia et al. 2005, Ciocca 2006). These differences are likely la rge enough to create differences in fungal community composition. It is because of thi s variation that we think a study of fungal communities on the Caribbean slope is worthw hile. The purpose of our study is to investigate the com munity composition and species richness in a lower montane rain forest on the Cari bbean slope at Monteverde, Costa Rica. We link our community parameters to elevatio nal gradients, pH level, species richness, and canopy coverage. By looking at eleva tional gradients in relation to species richness, soil pH levels and canopy coverage, we ca n investigate possible correlations between them. In addition to the above, we provide basic descriptions of the Caribbean
3 fungal community in terms of the morphological form s, and the substrates used by these fungi. MATERIALS AND METHODS Starting from the Monteverde Biological Station, we walked along the Sendero Principal in the direction of the SquatterÂ’s Shack, located o n 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 transe cts were drawn at approximately a constant elevation. For each transect we recorded c anopy coverage with a spherical densiometer, and soil pH level using a pH meter. An y macrofungi encountered within two meters on either side of the transect was photo graphed, 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 cros sing of transects or repeat specimens recorded. Sets of transects were walked on opposit e sides of the trail to further insure there was no crossover between data sets. Transect s were laid every fifty-meters, up to 1850 m above sea level. In total, data were taken a t seven different elevations. We calculated beta diversity between all possible pairs of transects. The equation we used was: g = a b number of habitats, where g = total number of species in two transects, a = the average species in the two transects, and th e number of habitats is two transects. RESULTS A total of 40 morphospecies 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 growing on three different substrates: dea d wood, soil, and leaf litter (Figure 2). Fourteen morphospecies were found on dead wood, twe nty-two on soil and four on leaf litter. We compared species richness per transect (elevati on) to canopy coverage, elevation and pH level. We found a positive trend f or greater species richness with more canopy cover, although it was not significant (Spea rman Rank Test, Rho = -0.58, p = 0.17, n = 7, Figure 3). There was a statistically s ignificant relationship between species richness and elevation (Spearman Rank Test, Rho = 0.80, p = 0.03, n = 7, Figure 4). As elevation increased, species richness decreased. Th ere was also nearly a statistically significant negative correlation between species co mposition and pH level (Spearman 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 funga l communities compared to distance between elevations. We found that as dista nce between transects increased, there was a trend for lowered similarity in fungal specie s composition (Spearman Rank Test, Rho = 0.36, p = 0.11, n = 21, Figure 5). These resu lts were not statistically significant. DISCUSSION
4 In our study we found 40 morphospecies of macrofung i in total. The most common morphological type was toadstool fungus, which comp rised 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 sp ecimens to be shelf fungi. This difference could be understood by the fact that Cio cca conducted her study during the dry season in Monteverde; shelf fungi are better adapte d to drier conditions, which could explain why she would have found a larger proportio n of these compared to other fungal morphologies on the Pacific slope. In contrast, fun gi on the aseasonal Caribbean slope, which has a relatively higher amount of precipitati on, would not harbor such a large fraction of desiccation-resistant growth forms. The fungal community of the Caribbean slope was ob served mainly on soil substrates (55% of our specimens), which differed f rom past studies on both the Pacific and Atlantic slopes. Williams (2006) found the majo rity of her specimens, 83.3%, growing on dead wood substrate. Her study was condu cted 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 bee n restricted to moisture-absorbent, dead wood substrates (Haber 2000). Another past stu dy, conducted by Herz (2004) on the Caribbean slope, found only 10% of the recorded spe cimens on soil substrate, and 58% on dead wood. This pattern could be explained by a variation in the amount of dead wood available 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, thu s providing macrofungi with a larger amount of dead wood substrate than available during our survey. We also found species richness to vary greatly bet ween transects, with anywhere from three to eleven species at each. We did not fi nd this variation to be significantly related to canopy coverage. This differs from a pas t study in which a trend for greater species richness in forested areas as opposed to li ght gaps was observed (McCracken 1995). An explanation could be that McCracken was s tudying more extreme differences in canopy cover conditions (complete canopy cover v ersus completely open light gaps), while our canopy coverage ranged from 54 to 82 %. H ence the difference in results between the two studies could be accounted for by d ifferences in the range of canopy coverage considered. We did, however, find a significant relationship b etween species richness and elevation, with fewer species at higher elevations. Herz (2004) ruled out the possibility of variability in dead wood characteristics (e.g. deca y and moisture of fallen logs) at different elevations on the Caribbean slope as bein g 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 correl ation between species richness and elevation. However, our results suggest that soil p H could influence how many species are fruiting at any given time. As elevation increa sed, pH increased and species richness decreased. Possible explanations for why soil acidi ty would decrease with increasing elevation include variable forest composition and p atchiness of volcanic ash. Different species of trees, which have varying elevational ra nges, have diverse effects on soil chemistry. It is possible that lower elevations con tain assemblages of trees that increase the acidity of the soil. Volcanoes in close proximi ty to Monteverde, such the highly
5 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 surro unding 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 in creasing variability in communities would most likely be caused by greater differences in abiotic (e.g. temperature, soil pH, wind, light availability) and biotic (e.g. tree com munities) 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 sam ple size is essential for drawing any definitive conclusions. Future studies concerning t he 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 inexha ustible patience, and Tom for providing us with mental reprieves when they were needed most. We wou ld also like to give a special thanks to Karen Masters for her guidance, support, and incredible a mount of work in formatting and carrying out this project. Lastly, we would like to thank Carmen Roja s for her advice and translation skills. LITERATURE CITED ALEXOPOULOS, C.J., MIMS, C.W., BLACKWELL, M. 1996. Introductory Mycology 4th ed. John Wiley & Sons, Inc., Toronto, pg. 6. ARORA, D. 1986. Mushrooms Demystified: A Comprehens ive Guide to the Fleshy Fungi Ten Speed Press, Berkeley, California, pg. 6. CIOCCA, E. 2000. Fungal species richness on an elev ational and longitudinal gradient on the continenta l 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 Univ ersity Press, Oxford, New York, pg. 41. HAWKSWORTH, D. 1991. The Fungal Dimension of Biodiv ersity: Magnitude, Significance and Conservation. Mycol. Res. 95: pp. 641-655. HERING, T.F. 1966. 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 Atla ntic slope. Spring 2004. CIEE Tropical Biology Program, pp. 98-107. JANOS, D.P. 1983. Tropical Mycorrhizae, Nutrient Cy cles and Plant Growth. In: Tropical Rainforest Diversity and Management Sutton, S.L., Whitmore, T.C. and Chadwick, A.C. e ds. Blackwell Scientific Publications, Oxford, England, pg. 498. LOREAU, M. 2000. Biodiversity and ecosystem functio ning: recent theoretical advances. Oikos 91 : 3-17. MATA, M. 1999. Macrohongos de Costa Rica Vol. 1. INBio, Santo Domingo de Heredia, Costa Ri ca, pp. 11, 16-17. McCRACKEN, T. 1995. Diversity of fleshy fungi in ga ps and forests. Spring CIEE Tropical Biology Program, pp. 237-244. MUNGUIA, P., GUZMAN, G., RAMIREZ-GUILLEN. 2005. Sea sonal community structure of macromycetes in Veracruz, Mexico. Ecography 28 : 1-9. WALES, M. 1998. Fungal abundance, species richness, and diversity of five life zones of Monteverde during two seasons. Fall CIEE Tropical Biology Prog ram, pp. 113-120.
6WATLING, R. 1981. Relationships between macromycete s and the development of higher plant communities. The fungal community. Its organization and role in the ecosystem Wicklow, D.T. and Carroll, G.C. eds. Dekker, New York, pp. 427-45 8. WILLIAMS, S. 2006. Dry season macrofungi of the Mon teverde Reserve. Spring CIEE Tropical Biology Program, pp. 1-5. nrr r nr
7 Figure 1. The number of specimens found of each mo rphological form on the Caribbean slope of the Continental Divide near Monteverde, Co sta Rica from 1550 Â– 1850 m. Toadstools comprised 50% of the 40 morphospecies fo und. nn n Figure 2. Frequency of fungi species found on vario us substrates on the Caribbean slope of the Continental Divide near Monteverde, Costa Ri ca from 1550 Â– 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. nn
8 Figure 3. Fungal species richness compared to perce nt canopy coverage on the Caribbean slope. There was a positive trend for greater speci es richness with more canopy cover. " nr !# # # Figure 4. Elevation compared to fungal species rich ness 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 between species richness and elevation. There was nearly a statistically significant negati ve correlation between species composition and pH level. # # # # #" #" # !n !nr
9 Figure 5. Beta diversity values of fungal communiti es compared to distance between elevations. As distance increases between elevation s, the lower the similarity in fungal species composition.