| | ||||
| | | | | |
| BACK TO PROJECT LIST | |||||
Comparison of fauna diversity in bromeliads in the garden and in the secondary forest at Las Cruces
Kim Walsh,
David Lesley,
David Fletcher.
July 19,2001
Bromeliads are numerous and diverse in the Costa Rica. Also, within the bromeliads, there is a microecosystem of organisms . There is interest to determine any differences in fauna diversity between the bromeliads in the garden, which are exposed to human impact, compared to the secondary forest. Our limited results indicated no significant difference in diversity, including richness and abundance. More studies are recommended to acquire more conclusive findings.
Introduction: Bromeliads can be found throughout Wilson Garden as well as into the secondary forest at Las Cruces. Bromeliads serve an important role as a ‘nursery’ habitat for many insect larvae. The insects, in turn can aid the bromeliads by bringing in organic matter and nutrients as they collect food. Also, by protecting ant nests, for example, the ants also protect the bromeliad from herbivores. We believe that a diversity of organisms in the bromeliad cups contributes to the health of the forest ecosystem. We hypothesize that if the bromeliads in the garden show comparable biological diversity to the bromeliads in the forest, then this indicates their successful ecological function within a garden ecosystem.
Procedure: Between 8-9 am, three bromeliads were collected from the secondary forest at FT13, Forest Trail, 0.65 km from the gate. These represent the "natural " samples. Three bromeliads from Wilson Garden were collected from the bromeliad trail. These represent the sample exposed to environmental change due to human impact. All samples were genus Guzmania . Forest samples were measured and were approximately the same size and were at approximately the same height on the tree (family Rubiaceae) The samples were rinsed and passed through a sieve. The smaller organisms were discarded. Organisms in the bromeliad cups were examined and identified to determine the diversity. The pH of the liquid in the cups was also measured.
Results and Analysis:
Garden samples Forest samples
Average bromeliad leaf length: 40 cm 36 cm
pH 7.0 8.5
Richness (# categories) 10 8
*Shannon-Weaver Diversity Index: .49762 .42491
Our results suggest greater richness in the garden samples. Ants and insect larvae were the most abundant organism in the forest bromeliads, while cladocerans were the most abundant organism in the garden bromeliads. The Shannon-Wiener index indicates no significant difference in the diversity of the samples. According to our results, the forest and garden bromeliad fauna samples contained a wide variety of life.
* Shannon-Weiner diversity index: H’= - sum pi log pi
References:
Gentry, A. 1996. Woody Plants of Northwest South America. University of Chicago Press.
Zar, J. 1999. Biostatistical Analysis. Prentice Hall.