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Vol. 51 No. 7, 2012
Shifts in Functional Traits of Aquatic Insects along a Subtropical Stream in Taiwan
Sen-Her Shieh1,*, Ling-Kuo Wang2, and Wen-Feng Hsiao2
1Department of Ecological Humanities, Providence University, 200, Sec. 7, Taiwan Boulevard, Shalu Dist., Taichung 433, Taiwan
2Department of Biological Resources, National Chiayi University, 300 University Road, Chiayi 600, Taiwan
Sen-Her Shieh, Ling-Kuo Wang, and Wen-Feng Hsiao (2012) Despite
an increasing interest in the study of functional diversity, there have
been no attempts to link aquatic insect traits, habitat variations, and
community structure in subtropical Asian streams. We examined
relationships between habitat characteristics and aquatic insect traits
at 7 sites along a subtropical stream in Taiwan by an RLQ analysis and
fourthcorner analysis. The habitat was described by the slope,
mineral substrate size, and water chemistry, while aquatic insect
traits were described using 40 categories of 9 functional traits.
The 1st axis of the RLQ analysis explained 96.5%, suggesting a strong
longitudinal environmental gradient structuring the characteristics of
sites and aquatic insect assemblages. The most influential
habitat variables were the slope, mineral substrate size, conductivity,
and alkalinity, which reflected both natural variations and human
impacts along the stream. The main covariations between traits
and habitat were a shift from organisms with combining features, such
as crawlers, a large body size, a flat body form, and low body
flexibility to organisms which are swimmers, possess high body
flexibility and a small body size, and feed on fine detritus and
microinvertebrates. In the results of the fourth-corner analysis,
18 of 40 trait categories were significantly correlated with
environmental variables. In particular, traits relating to flow,
such as body form, attachment to substrate, body flexibility, and food
type, showed the strongest correlations with environmental
variables. Longitudinal gradients of aquatic insect assemblages
corresponded to a gradual shift from aquatic insects that preferred
larger and more stable mineral substrates (rubble) to those that
preferred still waters in lowlands with finer substrates. The
results suggested that the low substrate heterogeneity and stability at
downstream sites led to a simpler but less stable functional
organization, and that functional traits should be sufficiently
sensitive to detect changes in environmental variables and can be used
for biomonitoring streams in Taiwan.
Key words: Life history traits, Habitat templet hypothesis, RLQ analysis, Fourth-corner analysis.
*Correspondence: E-mail:shshieh@pu.edu.tw
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