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Vol. 53, 2014
Dietary variation and food selection by mayfly grazers in a
subtropical mountain stream
Yi-Li
Chuang1, Shu-Fen Yu1,2 and Hsing-Juh Lin1*
1Department
of Life Sciences and Research Center for Global Change Biology,
National Chung Hsing University, Taichung 40227, Taiwan
2Shei-Pa National Park, Conservation and Research
Section, Miaoli County 36443, Taiwan
Abstract
Background: The classification of
functional feeding groups of aquatic insects is often misleading in
tropical/subtropical streams because their feeding habits are assumed
to be the same as their temperate counterparts according to the
mouthpart structure and foraging behavior. This study aimed to examine
the diets and preferences of mayfly grazers (Baetis spp. and Rhithrogena ampla) in a subtropical mountain
stream in the dry and wet seasons.
Results: In the stream, epilithic algal
communities on insect-excluded bricks (as a grazer-excluded control)
were dominated by small adnate diatoms, most likely due to the high
current velocity. Both grazers preferred understory and small adnate
diatoms, Achnanthes spp. and Achnanthidium pyrenaicum, in both
seasons. However, the stalked diatoms Gomphonema
spp. were preferred only by Baetis,
but not by Rhithrogena, in
the dry season when the current velocity became relatively slower. The
results of pairwise tests further showed that the algal compositions on
the insect-excluded bricks coincided with the diets of both grazers in
the wet season but were distinct from those on the bricks in the dry
season. Seasonal variations in the algal compositions of the diets of Rhithrogena and on the
insect-excluded bricks were apparent, but not in the diets of Baetis.
Conclusions: The algal physiognomy
was most likely attributed to the impact of the high current velocity
in the stream. Our results suggest that the diet preference by mayfly
grazers in the stream is potentially influenced by algal availability.
Key words: Chesson's alpha; Diatoms; Food
availability; Gut content; Mouthpart; Physiognomy.
*Correspondence: E-mail:
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