1 Fungal community diversity and composition on logs in relation to log size and penetrability Janaki Patel Department of Integrative Biology, University of Illinois at Urbana Champaign ABSTRACT Very little is known about how macrofungal communities on l ogs vary depending on different log characteristics. This study tested whether macrofungal communities on logs in premontane wet secondary forest in Monteverde, Costa Rica, vary significantly with changes in log size and penetrability. Additionally, this study determined the regional species diversity and turnover of macrofungal communities on logs, and determined whether there were trends between groups of macrofungal species growing on logs of different degrees of penetrability. One hundred logs with m acrofungi were sampled randomly and measured for size and penetrability. The fungi on each were recorded according to morphospecies. A total of 57 morphospecies were found, with the shelf fungus Hexagonia papyracea being the most common. There were no s ignificant relationships between the number of species per log and log penetrability, or between the occurrence of H. papyracea and log penetrability. However, H. papyracea occurred on logs with smaller diameters, and the number of species per log increas ed as a function of log diameter. There were also trends indicating higher species turnover with higher penetrability. The results suggest possible community succession and host specificity among macrofungi that colonize logs, but further research is nec essary to determine which log characteristics are important to host specific macrofungi. RESUMEN Se sabe muy poco sobre cÃ³mo las comunidades de macrohongos que crecen en maderos varÃan dependiendo de diversas caracterÃsticas del tronco. Se estudiÃ³ la posi bilidad de que las comunidades de macrohongos en maderos del bosque secundario hÃºmedo premontano en Monteverde, Costa Rica, varÃen significativamente con los cambios de tamaÃ±o y penetrabilidad del madero. AdemÃ¡s, se determinÃ³ la diversidad de las especies y la sucesiÃ³n de comunidades de macrohongos en Ã¡rboles caÃdos. TambiÃ©n, se encontraron tendencias entre los grupos de especies de macrohongos creciendo en maderos con differentes grados de penetrabilidad. Se muestrearon al azar cien maderos con macrohong os de acuerdo a su tamaÃ±o y penetrabilidad y se clasificaron de acuerdo a su morfologÃa. Se encontrÃ³ un total de 57 especies morfolÃ³gicas, siendo el hongo de oreja ( Hexagonia papyracea ) el mÃ¡s comÃºn. No se encontraron relaciones significativas entre el nÃºm ero de especies de hongos por madero y la penetrabilidad del madero, o entre la ocurrencia de H. papyracea y la penetrabilidad del Ã¡rbol caÃdo. Sin embargo, H. papyracea fue en maderos con diametros mÃ¡s pequeÃ±os, y el nÃºmero de especies por madero en funci Ã³n del diÃ¡metro del madero fue significativo y sepresentaron tendencias indicando una sustituciÃ³n mayor conforme la penetrabilidad aumenta. Los resultados sugieren una posible cambio de comunidad y especificidad por el anfitriÃ³n entre los macrohongos que c olonizan los Ã¡rboles caÃdos, pero se necesitan investigaciones adicionales para determinar quÃ© caracterÃsticas del madero son importantes para la colonizaciÃ³n por los macrohongos. INTRODUCTION The Kingdom Fungi contains an estimated 1.5 million species, b ut to date only 72,000 to 100,000 have been described (Hawksworth and Rossman 1997). Environmentally, fungi play a major role as parasites, food sources, and in nutrient cycling as decomposers (Hawksworth 1991). Economically, they have many commercial us es in agriculture and consumer products, and medically they hold great potential as useful drugs (Rossman 1994). However, literature on fungal diversity is sparse due to lack of systematic species
2 inventories. This inadequate body of information on fungi necessitates further studies if their biological relevance is to be fully realized. In Costa Rica, there are an estimated 40,000 to 70,000 species of fungi, of which only 2,000 have been described. Several studies done in Costa Rica during the wet sea son have shown that fungal diversity decreases with altitude (Johnson 2001; Whitesides 1992) but few studies have been done on fungal diversity as it relates to substrate. Some fungi may have growth requirements that only certain types of substrate can pr ovide; for example, fresh logs may have more nutrients than older, more rotted logs. Log penetrability (the ability to be penetrated by a sharp object) may be higher in more rotted logs because they are softer and have less structure. If log penetrability is related to rottenness, then logs with different penetrabilities may support different fungal species, indicating succession. Herz (2004) found that the majority of macrofungi in the Monteverde area occurred on dead wood substrates that had penetrabili ties ranging from 0.5 to 3 cm. Whether there is a relationship between log characteristics and the fungal communities that grow on them is yet to be determined. The purpose of this study was to determine whether a relationship exists between macrofungal communities on logs within a given area and the diameter and penetrability of those logs. In addition, this study determined the total macrofungal species diversity and turnover between logs, as well as between groups of logs with different degrees of pen etrability. METHODS This study was conducted in patches of premontane wet secondary forest at the Rockwell farm in Monteverde, Costa Rica between October 24, 2004 and November 15, 2004. One hundred logs with macrofungi were randomly sampled. The lengt h and diameter of each log were measured and the fungi on each log were photographed with a digital camera and recorded according to morphospecies. The penetrability of each log was determined by placing a one meter long hollow PVC tube over the log, drop ping a weighted probe through the tube, and then recording the amount of probe that penetrated beneath the surface of the log. This was done three times for each log and from these values the mean penetrability of each log was calculated. The number of s pecies per log as a function of log penetrability and diameter were analyzed using simple linear regressions. The penetrability of logs with the most common fungus was compared with the penetrability of logs without the most common fungus using an unpaire d t test. The same test was also performed with diameter instead of penetrability. Logs were grouped into four penetrability categories: A (0 1 cm), B (1 2 cm) C (2 3 cm) and D (3 4 cm). Alpha , beta , and gamma diversity were determined for each catego (qualitative) was used to compare the species composition between the four penetrability categories. RESULTS On the 100 logs sampled, 57 morphospecies were present. The alpha divers ity for the entire community was 1.1 species per log, the beta diversity was 0.52 and the habitat breadth was 1.92 logs. The majority of logs (91) supported only one species of fungus (Fig. 1). A simple linear regression testing the total number of species per log as a
3 function of log penetrability found no significant relationship ( = .001; P = .993; n = 100), but the same test using diameter instead of penetrability showed significance ( = .199; P = .047; n = 100): as log diameter increases, the number of species occurring on the log also increases (Fig. 2). When considering the four penetrability categories as separate communities of logs, category D had the highest beta diversity (1.0), category B had the highest number of species (22), and all four c ategories had an alpha diversity of 1.1 (Table 1). Categories for all pairs of categories and ranged from 0.09 to 0.23 (Table 2). The two most commonly found fungi were the shelf fungus Hexagonia papyracea , which occurred on 24 logs, and Xylaria polymorpha which occurred on 12 logs. Out of the 24 logs with H. papyracea , only one had H. papyracea co occurring with another species (Fig. 3), while ou t of the 12 logs with X. polymorpha , three had a second species present (Fig. 5). An unpaired t test for the presence of H. papyracea as a function of penetrability showed no significance (P = .089), but the same test using diameter instead of penetrabili ty showed significance (P = .041): logs with H. papyracea had significantly smaller diameters than logs without it (Fig. 6). Additional Observations Hexagonia papyracea generally occurred in clusters on groups of logs that were near each other and that ap peared to have originated from the same tree. Xylaria polymorpha did not follow this pattern; rather, it seemed to occur randomly. It was also observed to have a high degree of morphological variation. TABLE 1. and diversity and number of logs for each penetrability category. There is a trend of higher species turnover ( diversity) with higher penetrability. A (0 1 cm) B (1 2 cm) C (2 3 cm) D (3 4 cm) 1.1 1.1 1.1 1.1 diversity 0.47 0.54 0.68 1 diversity 19 22 12 11 number of logs 37 37 16 10
4 FIGURE 1. Frequency of logs supporting one, two or three macrofungal species in premontane wet secondary forest in Monteverde, Costa Rica. The majority of logs supporte d only one species. FIGURE 2. The number of macrofungal species per log changes significantly with log diameter.
5 category. Compari sons with Category D resulted in the lowest three values. Category combination Sorenson's Index_____ B:C 0.23 A:B 0.19 A:C 0.19 C:D 0.15 A:D 0.09 B:D 0.09 FIGURE 3. Frequency of logs with Hexagonia pap yracea occurring solitarily and paired (with another macrofungal species) in Monteverde, Costa Rica. Ninety six percent of Hexagonia papyracea occurred solitarily.
6 FIGURE 4. The number of logs supporting macrofungi in eac h penetrability category. Categories are ranges of log penetrability (cm): A (0 1), B (1 2), C (2 3) and D (3 4). FIGURE 5. Frequency of logs with Xylaria polymorpha occurring solitarily and paired (with another macrofun gal species) in Monteverde, Costa Rica. Seventy five percent of X. polymorpha occurs solitarily.
7 FIGURE 6. Mean diameter of logs with and without H. papyracea. Logs with H. papyracea had significantly smaller diameters th an logs without it. DISCUSSION The relationship between log penetrability and the number of species per log was not significant. One possible explanation for this is that a fungus colonizes and dominates a log, preventing another species from establish ing on the log. This could also explain why the relationship between log diameter and number of species on the log was significant, because logs with larger diameters have more surface area which might allow more than one species to colonize that space. A beta diversity of 0.52 and a habitat breadth of 1.92 logs for the entire community indicate a relatively high species turnover between logs; for penetrability categories, Table 1 shows a trend of increasing beta diversity with increasing penetrability. This high turnover is possibly due to size constraints allowing very few species per log as described above. However, there is evidence that another factor is Indices cal culated for all combinations of penetrability categories were all between 0.09 and 0.23, indicating strong dissimilarity in species composition between the four categories (Table 2). The three least similar pairs were A: D, B: D and C: D. The fact that t he three lowest similarity indices were always a result of comparisons with category D suggests that logs with high penetrability can support fungi that are very different from the fungi that are supported by logs with lower penetrability. It is likely th at logs with very high penetrability have a structure and nutrient composition that only certain types of fungi can grow on. Category A was also very different from the other categories (though to a lesser extent). This indicates that fresh logs and rott en logs support very different communities from each other (contributing to the observed high turnover) and from intermediately decomposed logs, suggesting that community succession might be taking place.
8 Among the four penetrability categories, categories A and B contained 74% of the logs, which indicates that fungi tend to colonize logs with lower penetrability. Logs with lower penetrability tend to have a lower moisture content (Herz 2004) and generally have more structure and nutrients because they are not far along in the decomposition process. This may provide the ideal habitat for many kinds of macrofungi and may be the reason the majority of fungi was found on logs with low penetrability. The observation of the shelf fungus Hexagonia papyracea be ing very common and clustered agrees with current literature which describes H. papyracea as gregarious, fruiting during the wet season and occurring only on decomposing wood (Mata 1999). Hexagonia papyracea significantly occurred on logs with smaller diam eters but did not vary significantly with changes in penetrability. This suggests possible substrate specialization based on size. However, several times it was observed to occur in groups of logs that appeared to originate from one species (e.g. a tree fall). Therefore, another possibility is that it colonizes logs based on factors that were not measured in this study, such as the nutrient composition or species of the log itself. Some fungi species are known to only colonize wood from specific plant s pecies (Mata 2003). Unlike H. papyracea , X. polymorpha did not seem to follow any pattern of occurrence. The logs were widely spaced and thus were less likely to belong to the same host species. However, it is difficult to draw conclusions about substra te specificity because there were only 12 samples of this species. The results of this study suggest trends which need to be investigated by further research. Fungi are an integral part of ecosystems, they hold great economic and medical potential and ye t they are poorly studied. Developing our knowledge of fungi is essential if we are to truly understand biodiversity and conserve it. ACKNOWLEDGEMENTS I would like to thank my advisor, Karen Masters, for all of her guidance, encouragement and enthusias m; the Rockwell family for allowing me to work on their beautiful farm; Richard LaVal for introducing me to my study; Ollie Hyman and Matt Gasner for their endless patience in answering questions, and Alan Masters for being a constant source of inspiration . LITERATURE CITED Hawksworth, D. L. 1991. The fungal dimension of biodiversity: magnitude, significance, and conservation. Mycol. Res. 95: 641 655. Hawksworth, D. L. and Amy Rossman. 1997. Where are all the undescribed fungi? American Phytopath ological Society 87: 888 891. Herz, K. 2004. Fungal species richness in relation to substrate penetrability and moisture on the Atlantic slope. CIEE, Spring. Johnson, V. 2001. The effect of elevation on fungal community species richness and composit ion in Monteverde, Costa Rica. CIEE, Fall. Mata, M. 1999. Macrohongos de Costa Rica. Vol. 1. Instituto Nacional de Biodiversidad. Mata, M. 2003. Macrohongos de Costa Rica. Vol. 2. Instituto Nacional de Biodiversidad. Rossman, Amy. 1994. A strat egy for an all taxa inventory of fungal biodiversity. Biodiversty and Terrestrial Ecosystems 14: 169 194. Whitesides, A. 1992. A comparison of tropical mushroom communities at two elevations: taxonomy and substrate. CIEE, Summer.
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Diversidad de la comunidad fngica y la composicin de los troncos en relacin con el tamao del tronco y la penetrabilidad
Fungal community diversity and composition on logs in relation to log size and penetrability
Very little is known about how macrofungal communities on logs vary depending on different log characteristics. This study tested whether macrofungal communities on logs in premontane wet secondary forest in Monteverde, Costa Rica, vary significantly with changes in log size and penetrability.
Additionally, this study determined the regional species diversity and turnover of macrofungal communities on logs, and determined whether there were trends between groups of macrofungal species growing on logs
of different degrees of penetrability. One hundred logs with macrofungi were sampled randomly and measured for size and penetrability. The fungi on each were recorded according to morphospecies. A total
of 57 morphospecies were found, with the shelf fungus Hexagonia papyracea being the most common. There were no significant relationships between the number of species per log and log penetrability, or between the occurrence of H. papyracea and log penetrability. However, H. papyracea occurred on logs with smaller diameters, and the number of species per log increased as a function of log diameter. There were also trends indicating higher species turnover with higher penetrability. The results suggest possible community succession and host specificity among macrofungi that colonize logs, but further research is
necessary to determine which log characteristics are important to host-specific macrofungi.
Se sabe muy poco sobre cmo las comunidades de macrohongos que crecen en maderos varan dependiendo de diversas caractersticas del tronco. Se estudi la posibilidad de que las comunidades de macrohongos en maderos del bosque secundario hmedo premontano en Monteverde, Costa Rica, varen significativamente con los cambios de tamao y penetrabilidad del madero. Adems, se determin la diversidad de las especies y la sucesin de comunidades de macrohongos en rboles cados. Tambin, se encontraron tendencias entre los grupos de especies de macrohongos creciendo en maderos con diferentes grados de penetrabilidad. Se muestrearon al azar cien maderos con macrohongos de acuerdo a su tamao y penetrabilidad y se clasificaron de acuerdo a su morfologa. Se encontr un total de 57 especies morfolgicas, siendo el hongo de oreja (Hexagonia papyracea) el ms comn. No se encontraron relaciones significativas entre el nmero de especies de hongos por madero y la penetrabilidad del madero, o entre la ocurrencia de H. papyracea y la penetrabilidad del rbol cado. Sin embargo, H. papyracea fue en maderos con dimetros ms pequeos, y el nmero de especies por madero en funcin del dimetro del madero fue significativo y se presentaron tendencias indicando una sustitucin mayor conforme la penetrabilidad aumenta. Los resultados sugieren un posible cambio de comunidad y especificidad por el anfitrin entre los macrohongos que colonizan los rboles cados, pero se necesitan investigaciones adicionales para determinar qu caractersticas del madero son importantes para la colonizacin por los macrohongos.
Text in English.
Costa Rica--Puntarenas--Monteverde Zone
Diversidad de especies
Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology Fall 2004
Ecologa Tropical Otoo 2004
t Monteverde Institute : Tropical Ecology