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Comparison of protist communities in native and exotic bromeliad species

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Comparison of protist communities in native and exotic bromeliad species
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Comparación de las comunidades protistas en especies de bromelias nativas y exóticas ( )
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Rhoney, Michelle, L
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Protista   ( lcsh )
Bromeliaceae   ( lcsh )
Microhabitats   ( lcsh )
Monteverde Biological Station   ( lcsh )
Protista
Bromeliaceae
Microhábitats
Estación Biológica de Monteverde (Costa Rica)
Tropical Ecology Fall 2004
Ecología Tropical Otoño 2004
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Abstract:
In this experiment, I compared protist community and composition found in the tanks, or phytotelmata, of a native bromeliad species, Vriesea werckleana, and an unidentified exotic species. This study was conducted in Monteverde, Costa Rica, near the Estación Biológica Monteverde, between October 22 and November 11, 2004. Samples were taken from 20 individuals of each native and exotic species. The protist species composition and abundance were determined for each individual bromeliad. Local, regional, and metacommunity composition were evaluated and compared. Local (alpha) richness was the average of the protist communities, whereas regional (gamma) richness (or metacommunity) was the sum of all species and diversity indices across all 20 tanks, either native or exotic. The results showed no significant difference between the local composition and diversity of protist communities in the native and exotic species of bromeliads: The average number of protist species (S), number of individuals (N), Shannon-Wiener Diversity Index (H’), and two other diversity indices were the same in both bromeliad species. On the contrary, the metacommunities of protists in the two bromeliad species were different in that the total number of individual protists, H’, Evenness (E) and two other diversity indices were higher for the exotic species. Therefore, exotic bromeliads have greater regional richness and can support larger, more diverse communities. One reason as to why exotic bromeliads harbor greater regional richness may be due to the exotics being closer to one another. The Unified Theory of Biodiversity (Hubbell) asserts that systems of communities are bi-directionally connected via immigration and emigration. Therefore, local communities affect each other and create metacommunities with connectivity. It is important, however, to further explore interactions between protist communities within native and introduced bromeliads because exotic protist species may disrupt native protist species interactions if they are dispersed to native protist communities.
Abstract:
En este experimento comparé las comunidades y las composiciones de protistas encontradas en los tanques, o fitotelmata, de una especie de bromelia nativa Vriesea werckleana y de una especie exótica. Este estudio fue conducido en Monteverde, Costa Rica, cerca de la Estación Biológica Monteverde, entre el 22 de octubre y el 11 de noviembre del 2004. Se recolectaron muestras de 20 individuos de cada especie nativa y exótica. Fue posible determinar el número de especies y el número de individuos por especies en cada bromelia individual. Por lo tanto, la composición local, regional y de la metacomunidad pudo ser evaluada y comparada. La riqueza local (Alfa) fue el promedio de las comunidades de protistas, mientras que la riqueza (Gama) regional (o metacomunidad) fue la suma de todas las especies e índices de diversidad en los 20 tanques, nativos o exóticas. Los resultados no mostraron ninguna diferencia significativa entre la composición (Alfa) y la diversidad local de las comunidades de protistas en la especie nativa y exótica de bromelias. El número promedio de las especies de protistas, el número de individuos, el índice de diversidad de Shannon-Wiener y otros dos indicies de diversidad fueron iguales en ambas especies de bromelias. Sin embargo, las metacomunides de protistas en las dos especies de bromelias fueron diferentes en que el número total de protistas individuales, H’, la uniformidad y otros dos índices de diversidad fueron más altos para la especie exótica. Por lo tanto, las bromelias exóticas presentaron una mayor riqueza regional y pueden apoyar a comunidades más grandes y diversas. Una posible explicación por la que las bromelias exóticas tienen más riqueza regional puede ser debido a que las exóticas están más cerca una de otra. La Teoría Unificada de la Biodiversidad (Hubbell) afirma que los sistemas de comunidades bidireccionales están conectados vía la inmigración y emigración. Por lo tanto, las comunidades locales se influencian unas a otras y crean metacomunides con conectividad. Se necesita, sin embargo, explorar más las interacciones entre las bromelias nativas e introducidas porque las bromelias exóticas pueden contender especies exóticas de protistas que interrumpen las interacciones de las especies de protistas si se dispersan a las comunidades nativas de protistas.
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1 Comparison of Protist Communities In Native and Exotic Bromeliad Species Michelle L. Rhoney Department of Biology, Santa Clara University ________________________________________________________________________ ABSTRACT In this experiment, I compared pro tist community and composition found in the tanks, or phytotelmata, of a native bromeliad species, Vriesea werckleana and an unidentified exotic species. This study was conducted in Monteverde, Costa Rica, near the Estacin Biolgica Monteverde, between O ctober 22 and November 11, 2004. Samples were taken from 20 individuals of each native and exotic species. The protist species composition and abundance were determined for each individual bromeliad. Local, regional, and metacommunity composition were eva luated and compared. Local (alpha) richness was the average of the protist communities, whereas regional (gamma) richness (or metacommunity) was the sum of all species and diversity indices across all 20 tanks, either native or exotic. The results showed n o significant difference between the local composition and diversity of protist communities in the native and exotic species of bromeliads: The average number of protist species (S), number of individuals (N), Shannon ther diversity indices were the same in both bromeliad species. On the contrary, the metacommunities of protists in the two bromeliad species were different in that the total ere higher for the exotic species. Therefore, exotic bromeliads have greater regional richness and can support larger, more diverse communities. One reason as to why exotic bromeliads harbor greater regional richness may be due to the exotics being closer to one another. The Unified Theory of Biodiversity (Hubbell) asserts that systems of communities are bi directionally connected via immigration and emigration. Therefore, local communities affect each other and create metacommunities with connectivity. It is important, however, to further explore interactions between protist communities within native and introduced bromeliads because exotic protist species may disrupt native protist species interactions if they are dispersed to native protist communities. RESUMEN En este experimento compar las comunidades y las composicin de protistas encontradas en los tanques, o fitotelmata, de una especie de bromelia nativa Vriesea werckleana y de una especie extica. Este estudio fue conducido en Monteverde, Costa Rica, cerca de la Estacin Biolgica Monteverde, entre el 22 de octubre y el 11 de noviembre del 2004. Se recolectaron muestras de 20 individuos de cada especie nativa y extica. Fue posible determinar el nmero de especies y el nmero de individuos por es pecies en cada bromelia individual. Por lo tanto, la composicin local, regional y de la metacomunidad pudo ser evaluada y comparada. La riqueza local (Alfa) fue el promedio de las comunidades de protistas, mientras que la riqueza (Gama) regional (o metaco munidad) fue la suma de toda las especie e ndices de diversidad en los 20 tanques, nativos o exticas. Los resultados no monstraron ninguna diferencia significativa entre la composicin (Alfa) y la diversidad locales de las comunidades de protistas en la especie nativa y extica de bromelias. El nmero promedio de las especies de protistas, el nmero de individuos, el ndice de diversidad de Shannon Wiener y otros dos indicies de diversidad fueron iguales en ambas especies del bromelias. Sin embargo, los m etacomunides de protistas en las dos especies de bromelias fueron diferentes ms altos para la especie extica. Por lo tanto, los bromelias extic as presentaron una mayor riqueza regional y pueden apoyar a comunidades ms grandes y diversas. Una posible explicacin por la que las

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2 bromelias exticas tienen ms riqueza regional puede ser debido a que las exticas estn ms cerca una de otra. La Teor a Unificada de la Biodiversidad (Hubbell) afirma que los sistemas de comunidades bidireccionales estn conectados va la imigracin y emigracin. Por lo tanto, las comunidades locales se influencian unas a otras y crean metacomunides con conectividad. Se ne cesita, sin embargo, explorar ms las interacciones entre las bromelias nativas e introducidas porque las bromlias exticos pueden contender especies exticas de protistas que interrumpen las interacciones de las especies de protistas si se dispersan a las comunidades nativas de protitas. INTRODUCTION Epiphytic tank bromeliads create important and unique habitats for other organisms because their leaves tightly overlap at the base, creating cisterns that trap rainfall and nutrients which can support aquat ic life. These reservoirs, also known as phytotelmata, not only provide drinking water for canopy animals, but also supply a habitat and place to breed for various organisms, thus creating tiny ecosystems. Many tropical forest frogs, for example, require t development (Utley and Burt Utley 1983). Additionally, the collected water contains microscopic protozoa, which are very important in sustaining these tiny ecosystems. Protozoa are unicell ular eukaryotes that obtain nutrients and energy by heterotrophy (Begon et al. 1990). They are important links in food webs because they can be predators of bacteria and small phytoplankton, prey for zooplankton, and mediators for recycling nutrients essen tial for phytoplankton and microbial growth (Carrias et al. 2001). Only recently have protozoa been considered essential contributors to the metabolism of both aquatic and terrestrial ecosystems (Patterson 1996). Few experiments have been conducted on t he effects of protist communities on metazoa (Kingdom Animalia) communities within epiphytic tanks. One experiment in French Guiana explored freshwater organism interactions within these tanks (ranging from algae, fungi, protozoa, and bacteria to frogs and insects) and found that protozoa are very essential to the functioning of aquatic ecosystems, including those habitats within tank bromeliads. Protozoa not only provide essential pathways for dissolved organic matter but also consume bacteria from the tan ks. Additionally, they found limited evidence that suggests that mosquito larvae, copepods and rotifers may be important predators of protozoa. The authors of this study further proposed that protozoa are even more essential than metazoa for the reminerali zation and release of nutrients that may be vital for bromeliad growth (Carrias et al. 2001). Bromeliads are being introduced to Monteverde gardens from different regions of the world. These plants are regarded as ideal ornamentals because they have low m aintenance requirements. Frequent watering is unnecessary because the phytotelmata provides sufficient water to the plant. But exotic bromeliad species in gardens may affect natural ecosystems and ecological processes, either by altering or reducing the in teractions between different species. For instance, exotic bromeliads may harbor exotic protists that compete with or prey upon native tank fauna. On the other hand, exotic bromeliads may supply additional habitat for tank dwelling microorganisms that are native to the area, possibly even ameliorating loss of native bromeliads during habitat destruction. According to The Unified Theory of Biodiversity (Hubbell), local communities are bi directionally connected via immigration and emigration and can create l arger, more diverse metacommunities. Therefore, exotic and native protist species

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3 can presumably counter the effects of drift through connectivity, larger communities, and increased options for habitat (for example, a native protist inhabiting an exotic br omeliad). In Monteverde, there have been no experiments comparing the protozoa communities in exotic vs. native tank bromeliads, which is the focus of this study. Because protists are vital components of bromeliad tank ecosystems, it is important to see wh ether their composition, abundance, and diversity are dependent on the host species. I compared the protist communities found within tanks of an unidentified exotic bromeliad and tanks of a native bromeliad, Vriesea werckleana MATERIALS AND METHODS I conducted my experiment in Monteverde, Costa Rica in areas surrounded by Premontane Moist Forest ( Hartshorn) between October 22 and November 11, 2004. The exotic bromeliad species was located in below the Estatci n Biolgica Monteverde). This disturbed, open area was at an elevation of 1500 m and exposed to high amounts of sunlight. The native bromeliad species, V. werckleana was located in pasture behind the Estacin Biolgica Monteverde (1540 m). The native bro meliads were found either on a large, fallen tree or an enormous tree both largely exposed to sun. Water samples were taken from 20 medium sized (between .18 and .24 m in diameter) individuals of the native and exotic species, from a location with continu ous sun exposure. Each individual bromeliad was shaken at the base for at least ten seconds before a small amount (about five ml) of water from the bottom of the tank was collected with an eyedropper and placed in a vial. At the Estacin Biolgica Montever de lab, each vial containing the sample of water was shaken before being drawn with the eyedropper. Then a single drop of water was placed on a slide. Five different, random locations in the drop of water were examined under a Leitz Wetzlar dialux microsco pe (at X40) for about 10 minutes. At each location, every protist observed was sketched and the abundances of similar looking protists were recorded. I was able to determine the number of morpohological species and the number of individuals per species in each individual bromeliad. Each species was assigned a morphological name and individuals with similar morphological characteristics were grouped under the name. An average was computed for the number of protists found at each of the five, random locations in each drop of water. The average of individual protists, species, and diversity indices found in the bromeliad tanks, either native or exotic, represented the local (alpha) species richness. In other words, the protist communities in all 20 tanks, nativ e or exotic, were summed and divided by 20. The sum of all protist species, individuals, and diversity indices across all 20 tanks, either native or exotic, was the regional (gamma) richness. Regional richness is also referred to as a metacommunity.

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4 RE SULTS To evaluate community composition at the regional (gamma) level, the total number of protist species and the abundance of individuals in each species were compared between the native and exotic bromeliads. Each protist species was ranked according t o its relative abundance. The native and exotic bromeliad species contained almost identical relative abundances of protist species, although the native bromeliad had 27 protist species and the exotic had 24 (Figure 1). The most widespread protist specie s found in the exotic bromeliads were species A, I, N, F, H, S, and T. Species A and I were also the most abundant species. For the native bromeliads, protist species A, I, J, and T were both most widespread and most abundant (Table 1). Therefore, the mo st common protist species found in both native and exotic bromeliads were protist species A, I, and T. There was overlap in protist species composition in the two bromeliads: Seventeen species were found in both the native and exotic bromeliad species. Sev en species of protists were solely found in the exotic tanks, whereas ten protist species were found only in the native bromeliad species. Overall, the native bromeliad species contained more protist species but with fewer individuals per species. The sum of individual protists found in the two bromeliad species, native and exotic, were used to compare the protist metacommunities (gamma richness). N early twice as many individual protists were found in the exotic bromeliads compared to the native. Other comp arisons of metacommunity diversity were made using a Jack knifed species richness (JackS), Boot Shannon slightly higher values for all of these measures than the native bromeliad species (Table 2). There was no significant difference b bromeliad species (t = 1.37; p > 1.96; N = 20 for each bromeliad species)(Magurran 1988). The statistical progr am JMP and a modified t test (Magurran) were used to assess whether the average protist species richness (S), Boot strapped species richness (BootS), Jack knifed species richness (JackS), Shannon Alpha, and number of i ndividuals (N) differed significantly between the native and exotic bromeliad species. Results showed no significant difference in the average number of species found in the native and exotic bromeliad species (f = .9277; p < .05; N = 20). The richness as assessed by BootS richness and JackS richness was not different (f = Shannon species, number of individuals, Shannon found in each species, native or exotic, were also graphed to demonstrate no difference in local communities between the two bromeliads (Figure 2). DISCUSSION This study is the first in which protist communities within native and exotic tank bromeliads are compared in Monteverde, Costa Rica. There were no significant differences in the diversity and richness indices between the protist community

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5 composition of the native bromeliad species, Vri esea werckleana and the exotic species on the local (alpha) level, although there was variation between the two species on the regional (gamma) level. The exotic and native tanks had equal average diversity, richness, and number of individuals. This sugge sts that the average exotic bromeliad species does not differ from the average native bromeliad, in terms of how diverse the community is. However, the exotic protist metacommunity, or regional (gamma) richness, was higher in every parameter measured (incl uding total number of individuals community. One reason as to why exotic bromeliads harbor greater regional richness may be due to the exotics being closer to one another The Unified Theory of Biodiversity (Hubbell) asserts that systems of communities are bi directionally connected via immigration and emigration. Therefore, local communities affect each other and create metacommunities with connectivity. This theory also stresses that random processes, eventually common species become more common while rare species become rarer. Local community richness is determined by the rate of drift, but drift is slower when local communities are large and have high connectivity and speciation rates. Therefore, because exotic bromeliads are grouped together in tighter vicinities, it promotes migration and thwarts random walks to extinction, helping to mai ntain high richness, diversity, and evenness. Protist presumably colonize tanks by either being carried by small animals that live or breed in these micro ecosystems, by being splashed in or out of tanks, or by being transported by wind. Dispersal among lo cal communities influences and alters species composition and abundance (Kneitel and Miller 2003). Therefore, since exotic bromeliad species are close together, dispersal may be efficient and allow them to easily inhabit other exotic bromeliads near by. An other reason for greater regional richness in exotic bromeliads may be that exotic species are larger than natives. Larger areas (or tanks) allow more individuals and species to co exist, and therefore slow the processes of drift. However, further studies are necessary to determine if exotic bromeliad species are commonly larger than natives, because I only noticed the exotic bromeliad species to be slightly larger. For whatever reason, it is important that exotic bromeliad species harbor larger and more d iverse communities of protists. Perhaps as forests are replaced with homes and gardens containing exotic bromeliads, these introduced plants will provide additional habitat and larger, more complex interactions between protist species, which can, in turn, create more diverse (meta) communities at the regional level. bromeliad protists. Exotic bro meliads may contain exotic protist species that disrupt species interactions if they are dispersed to native protist communities. Rare, native protists may be lost, or even perhaps common species, due to disrupted interactions that can result in a decrease of native fauna diversity. An experiment conducted at Washington University's Tyson Research Center manipulated the availability of resources, predator density, and disturbance levels to observe protozoan and rotifer richness, community structure, and spe cies abundance. Their results showed that the effects of both predators and disturbances drastically changed protist abundance,

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6 diversity, and community structure, a finding also common in other taxa and communities (Kneitel and Chase 2004). Therefore, int roduced bromeliad species may contain exotic protists that are preditors or competators who will disrupt native protist interactions, and ultimately cause the loss of rare, native protist species. Although it is unknown whether protists found in native bro meliads are the original colonizers or if they came from exotic bromeliads we can hypothesize that the species involved will be (1) the ones unique to the exotics and (2) the ones unique to the natives. Particularly, future studies should watch the fate o f rare (or unique) native bromeliads and see if they are influenced by introduced bromeliad species. Research should also focus on other species of native bromeliads to see whether those exotic protists are truly exotic Observations of the kinds of specie s exotic bromeliads originally bring in their phytotelmata need to be compared to what they have 5, 10, etc. years later, because it is imperative to learn more about the origin of those rare protists that are unique to exotic tanks. ACKNOWLEDGMENTS Tre mendous thanks to Karen Masters for assistance in the field, support and ideas, and all the hours she spent helping me with statistics. I am also grateful to Allen Masters who provided this project idea and gave support and opinions for this experiment. I could not have accomplished this research without them. Thanks to Ollie and Javier who put up with my ridiculous questions and offered great advice and help. Special thanks to Matt who not only helped me extensively on the results and conclusions of this e xperiment, but he also managed to climb an enormous tree just to obtain a couple samples of bromeliad tank water. When my leg was injured, Sonja Rodriguez, my Mama Tica, provided transportation to the gh. Thank you to Joanna who helped develop my ideas and thoughts about the results of this experiment. Thanks also extended to the Estacin Biolgica Monteverde for providing equipment and a place to examine the microorganisms. ___________________________ ___________________________________________________________ LITERATURE CITED Begon, M., J. Haper, and C. Townsend. 1990. Ecology: 2 nd edition Blackwell Scientific Publications Boston: pp. 366 367. Carrias, J F., M E. Cussac, and B. Corbara. 2001. A Prel iminary study of freshwater protozoa in tank bromeliads. Journal of Tropical Ecology 17: 611 617. Chase, J. M., and J. M. Kneital. 2004. Disturbance, predator, and resource interaction alter container community composition. Ecology 85: 2088 2093. Hartsh orn, G. S., 1983. 7 Plants: Introduction. In: Costa Rican Natural History, D. H> Janzen ed. The University of Chicago Press, Chicargo IL, pp. 119 123. Hubbell, S. P. 2001. The Unified Neutral Theory of Biodiviseity and Biogeography Princeton University P ress New Jersey: pp. 76 116. Kneitel, J. M., T. E. Miller. 2003. Dispersal rates affect species composition in metacommunities of Sarracenia purpurea Inquilines. American Naturalist 162: 165 172. Margurran, Anne E., 1988. Ecological Diversity and Its Me asurement Princeton University Press New

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7 Jersey. (pg 35) Patterson, D.J. 1996. Free Living Freshwater Protozoa Manson Publishing Ltd London: pp. 9 10. Utley, J. F. and Burt Utley K. 1983. Bromeliads (Pia silvestre, Piuelas, Chiras, Wild Pineapple). In: Costa Rican Natural History, D. H> Janzen, ed. The University of Chicago Press, Chicago IL, pp. 197 200.

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8 ________________________________________________________________________ Figure 1. Rank abundanc e for a native bromeliad, Vriesea werckleana and an exotic bromeliad species, in Monteverde, Costa Rica. Twenty individual tank bromeliads were sampled in each species, native and exotic, between October 22 and November 11, 2004. The native bromeliad spec ies had 27 species of protists, and the exotic bromeliad species had 24 protist species.

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9 ________________________________________________________________________ Table 1. Number of exotic and native bromeliads that contained a certain pr otist species, and number of individuals found in that species, in Monteverde, Costa Rica. A total of 24 protist species were found in the exotic bromeliad species whereas the native bromeliad, Vriesea werckleana contained 27 protist species. Twenty brome liads, in both native and exotic, were sampled between October 22 and November 11, 2004.

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10 _______________________________________________________________________ Table 2. Total number of individual protists (N), Jack knifed species richness, Boot strap Evenness (E) found in the native bromeliad Vriesea werckleana and the exotic species; Summations were based on twenty samples (one sample per bromeliad) from the native and e xotic species between October 22 and November 11, 2004, in Monteverde, Costa Rica. N JackS BootS Alph H' E Exotics (total) 1280 22.75 20.49 2.96 0.65 0.20 Natives (total) 621 14.75 11.83 1.69 0.57 0.17

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11 ________________________________________________________________________ Figure 2a d. Average number with error bars of individual protists (a), Shannon Wiener Diversity Index (b), protist species (c), and Evenness (d) found in the phytotelmata of a native bromeliad, Vriesea werckleana and an exotic bromeliad species, in Monteverde, Costa Rica. Twenty individual tank bromeliads of each species, native and exotic, were sampled betwee n October 22 and November 11, 2004.


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In this experiment, I compared protist community and composition found in the tanks, or phytotelmata, of a native bromeliad species, Vriesea werckleana, and an unidentified exotic species. This study was conducted in Monteverde, Costa Rica, near the Estacin Biolgica Monteverde, between October 22 and November 11, 2004. Samples were taken from 20 individuals of each native and exotic species. The protist
species composition and abundance were determined for each individual bromeliad. Local, regional, and metacommunity composition were evaluated and compared. Local (alpha) richness was the average of the
protist communities, whereas regional (gamma) richness (or metacommunity) was the sum of all species and diversity indices across all 20 tanks, either native or exotic. The results showed no significant
difference between the local composition and diversity of protist communities in the native and exotic species of bromeliads: The average number of protist species (S), number of individuals (N), Shannon-Wiener Diversity Index (H), and two other diversity indices were the same in both bromeliad species. On the contrary, the metacommunities of protists in the two bromeliad species were different in that the total number of individual protists, H, Evenness (E) and two other diversity indices were higher for the exotic species. Therefore, exotic bromeliads have greater regional richness and can support larger, more diverse communities. One reason as to why exotic bromeliads harbor greater regional richness may be due to the exotics being closer to one another. The Unified Theory of Biodiversity (Hubbell) asserts that systems of communities are bi-directionally connected via immigration and emigration. Therefore, local communities
affect each other and create metacommunities with connectivity. It is important, however, to further explore interactions between protist communities within native and introduced bromeliads because exotic protist
species may disrupt native protist species interactions if they are dispersed to native protist communities.
En este experimento compar las comunidades y las composiciones de protistas encontradas en los tanques, o fitotelmata, de una especie de bromelia nativa Vriesea werckleana y de una especie extica. Este estudio fue conducido en Monteverde, Costa Rica, cerca de la Estacin Biolgica Monteverde, entre el 22 de octubre y el 11 de noviembre del 2004. Se recolectaron muestras de 20 individuos de cada especie nativa y extica. Fue posible determinar el nmero de especies y el nmero de individuos por especies en cada bromelia individual. Por lo tanto, la composicin local, regional y de la metacomunidad pudo ser evaluada y comparada. La riqueza local (Alfa) fue el promedio de las comunidades de protistas, mientras que la riqueza (Gama) regional (o metacomunidad) fue la suma de todas las especies e ndices de diversidad en los 20 tanques, nativos o exticas. Los resultados no mostraron ninguna diferencia significativa entre la composicin (Alfa) y la diversidad local de las comunidades de protistas en la especie nativa y extica de bromelias. El nmero promedio de las especies de protistas, el nmero de individuos, el ndice de diversidad de Shannon-Wiener y otros dos indicies de diversidad fueron iguales en ambas especies de bromelias. Sin embargo, las metacomunides de protistas en las dos especies de bromelias fueron diferentes en que el nmero total de protistas individuales, H, la uniformidad y otros dos ndices de diversidad fueron ms altos para la especie extica. Por lo tanto, las bromelias exticas presentaron una mayor riqueza regional y pueden apoyar a comunidades ms grandes y diversas. Una posible explicacin por la que las bromelias exticas tienen ms riqueza regional puede ser debido a que las exticas estn ms cerca una de otra. La Teora Unificada de la Biodiversidad (Hubbell) afirma que los sistemas de comunidades bidireccionales estn conectados va la inmigracin y emigracin. Por lo tanto, las comunidades locales se influencian unas a otras y crean metacomunides con conectividad. Se necesita, sin embargo, explorar ms las interacciones entre las bromelias nativas e introducidas porque las bromelias exticas pueden contender especies exticas de protistas que interrumpen las interacciones de las especies de protistas si se dispersan a las comunidades nativas de protistas.
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