Title

Quantifying the collapse of vertical stratification at Costa Rica forest edges

Poster Number

11C

Lead Author Major

Biological Sciences

Lead Author Status

Senior

Second Author Major

Biological Sciences

Second Author Status

Senior

Format

Poster Presentation

Faculty Mentor Name

Ryan Hill

Faculty Mentor Email

rhill@pacific.edu

Faculty Mentor Department

Biological Sciences

Abstract/Artist Statement

A striking pattern of community organization in the otherwise bewildering green diversity of tropical rainforests is vertical stratification. Stratification is important for maintaining spatial and temporal diversity patterns in these forest communities. In insects such as butterflies for example, vertical stratification affects their ability to accurately locate host plants, find a mate, and the duration of flight to complete these activities. However, it is not clear how these tropical butterflies maintain the stratification throughout the forest. DeVries (1988) predicted that differences in light intensity drive vertical distribution of butterflies in tropical rainforest communities based on his observations that some canopy flying species are observed lower at forest edges where the sparse canopy allows significant amounts of light to reach the forest floor. However, temperature also changes from the canopy to the understory, and this may also be a factor in butterfly stratification. To quantitatively validate stratification collapse and evaluate whether light or temperature is more important, a 15-month long trap study was conducted in Northeast Costa Rica at the same site as DeVries’ original study. A total of 32 trap sites were placed in edge, valley, and ridge habitats with canopy and understory traps in each that were fitted with data loggers recording temperature and light. Stratification was quantified in each habitat using beta diversity, percent similarity, and relative change in canopy presence at the edge. In total, 91 species were captured in 103 trapping days with 41 species identified as having a clear preference for the canopy. Our results confirm DeVries’ anecdotal observation that at forest edges, canopy species tend to be found relatively more in the understory compared to forest sites. Extensive data on light and temperature distribution in the different forest sites are summarized and discussed as to how they relate to the vertical distribution of nymphalids.

Location

DeRosa University Center, Ballroom

Start Date

28-4-2018 10:00 AM

End Date

28-4-2018 12:00 PM

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Apr 28th, 10:00 AM Apr 28th, 12:00 PM

Quantifying the collapse of vertical stratification at Costa Rica forest edges

DeRosa University Center, Ballroom

A striking pattern of community organization in the otherwise bewildering green diversity of tropical rainforests is vertical stratification. Stratification is important for maintaining spatial and temporal diversity patterns in these forest communities. In insects such as butterflies for example, vertical stratification affects their ability to accurately locate host plants, find a mate, and the duration of flight to complete these activities. However, it is not clear how these tropical butterflies maintain the stratification throughout the forest. DeVries (1988) predicted that differences in light intensity drive vertical distribution of butterflies in tropical rainforest communities based on his observations that some canopy flying species are observed lower at forest edges where the sparse canopy allows significant amounts of light to reach the forest floor. However, temperature also changes from the canopy to the understory, and this may also be a factor in butterfly stratification. To quantitatively validate stratification collapse and evaluate whether light or temperature is more important, a 15-month long trap study was conducted in Northeast Costa Rica at the same site as DeVries’ original study. A total of 32 trap sites were placed in edge, valley, and ridge habitats with canopy and understory traps in each that were fitted with data loggers recording temperature and light. Stratification was quantified in each habitat using beta diversity, percent similarity, and relative change in canopy presence at the edge. In total, 91 species were captured in 103 trapping days with 41 species identified as having a clear preference for the canopy. Our results confirm DeVries’ anecdotal observation that at forest edges, canopy species tend to be found relatively more in the understory compared to forest sites. Extensive data on light and temperature distribution in the different forest sites are summarized and discussed as to how they relate to the vertical distribution of nymphalids.