Transcript Impacts of Forest Types on Formicadae Biodiversity, Native vs Alien

Impacts of Forest Types on Formicadae Biodiversity:
Native vs Alien Species
A Comparison of Secondary Forest versus Eucalyptus Forest in Southern
Brazil
Maryani P. Rasidjan
CERC @ Columbia University
116 St. and Broadway
New York, NY
[email protected]
Introduction
The introduction of allien species, specifically forest tree
plantations, is a controversial topic in conservation
biology. While it is often assumed that introduction of
exotic species would eventually deplete the native fauna,
certain introductions such as recolonization of past tree
species is accepted. At present, in the severely
endangered Atlantic forest of Brazil, an estimated 7.3%
of the biome’s original surface is left. Of this small
amount only 2% are of native forest. Because
Eucalyptus plantations are a source of sustainable
income for local farmers, they have served as a popular
replacement for agricultural deforestation. In Brazil,
there are over 3 million hectares of Eucalyptus
plantations, and exotic tree species.
• ?Question?: Is there a relationship between the
exotic Eucalyptus forest and native formicadae
diversity
• Null Hypothesis: There would be no difference in
ant diversity collected in the Secondary forest and
the Eucalyptus forest
• Expected Hypothesis: There would be more ant
diversity in the Secondary forest because it
contains native tree species
• Alternative Hypothesis: There would be more ant
diversity in the Eucalyptus Forest
Methods
Study Area:Bairro do Moinho, Nazare, Sao Paulo State, S.EBrazil
~ Secondary Forest: *3 strata (2, 7, 11 meters)
*dense canopy cover
* heterogeneous tree species
}both were ~20 years old
~ Eucalyptus Forest: *2 strata (5 and 10 meters)
*open canopy
* homogeneous species (Eucalyptus)
The ants in the canopy and litter samples were collected with an aspirator and then
classified by morphotype. Colection was conducted during the day between the
hours of 11am and 5pm, during the month of June, winter season.
In both study sites the edges were avoided.
~ Data Collection:
*pitfalls (1/site and left over a 24 hour period) *litter extractions
*15 min tree trunk observations *10 canopy samples (trees 2-5 meters in height)
Results
• Eucalyptus forest :
*21 total species
*51 individuals
*60% represented by 1 individual
* 1%was a dominant species
Shannon-Weiner and Evenness Indices indicated greater ant diversity
H-value= 2.58
Evenness=.846
• Secondary forest:
*16 total species
*51 individuals
*70% represented by 1 individuls *less than 1% was dominant species
Shannon-Weiner and Eveness Indices indicated less ant diversity
H-value=1.70
Evenness=0.513
Sorenson Coefficient= 4% overlap; 2 species overlap *worker leaf-cutter
* terminator
Conclusions
• The expected hypothesis was disproven as there was more formicade
diversity in the Eucalyptus forest
• This would discount the expected negative influence of the physical and
chemical alterations that the Eucalyptus forest would cause
• Since the open canopy of the Eucalyptus forest would expose more
surrounding plants, possibly high level shade plants, to direct sunlight,
there would be less dense vegetation. In addition, the reduced plant
species might provide more room for ant habitat. This may be why two
ant mounds were observed in the Eucalyptus forest and none in the
Secondary forest.
• Moreover the greater open canopy caused drier ground litter, which
may indicate why more arboreal ants were found in the
• Also in order to ensure rapid growth of the Eucalyptus trees, the
plantation would most likely have greater soil quality and support a
greater ant population
• lack of predator habitat (anteater) could also enhance ant population in
the Eucalyptus forest
~ Statistical Analysis:
•Shannon-Weiner Index
•Eveness Index
•Sorenson Coefficient