Comparative Feeding Ecology of Leaf Pack-Inhabiting Systellognathan Stoneflies (Plecoptera) in the Upper Little Missouri River, Arkansas

The feeding ecologies of leaf pack-associated systellognathan stoneflies were examined from 6 June 1980 21 May 1981. Species composition, seasonal abundance, nymphal growth, feeding habits and mouthpart morphology were determined for the eight dominant stonefly species. Prey preferences and predator-prey size relationships were also examined for omnivorous and carnivorous species. Foregut analysis from 2860 individuals indicated opportunistic feeding on the most abundant prey insects, usually in proportion to prey frequency. Feeding preference studies generally indicated random feeding on major prey groups. Prey and predator sizes were usually highly correlated (p<0.01), with predators expanding their prey size thresholds with growth. The potential for competition between sympatric stoneflies for prey is discussed

Litter Breakdown and Microbial Succession on Two Submerged Leaf Species in a Small Forested Stream

<div><p>Microbial succession during leaf breakdown was investigated in a small forested stream in west-central Georgia, USA, using multiple culture-independent techniques. Red maple (<i>Acer rubrum</i>) and water oak (<i>Quercus nigra</i>) leaf litter were incubated <i>in situ</i> for 128 days, and litter breakdown was quantified by ash-free dry mass (AFDM) method and microbial assemblage composition using phospholipid fatty acid analysis (PLFA), ribosomal intergenic spacer analysis (RISA), denaturing gradient gel electrophoresis (DGGE), and bar-coded next-generation sequencing of 16S rRNA gene amplicons. Leaf breakdown was faster for red maple than water oak. PLFA revealed a significant time effect on microbial lipid profiles for both leaf species. Microbial assemblages on maple contained a higher relative abundance of bacterial lipids than oak, and oak microbial assemblages contained higher relative abundance of fungal lipids than maple. RISA showed that incubation time was more important in structuring bacterial assemblages than leaf physicochemistry. DGGE profiles revealed high variability in bacterial assemblages over time, and sequencing of DGGE-resolved amplicons indicated several taxa present on degrading litter. Next-generation sequencing revealed temporal shifts in dominant taxa within the phylum <i>Proteobacteria</i>, whereas γ-<i>Proteobacteria</i> dominated pre-immersion and α- and β-<i>Proteobacteria</i> dominated after 1 month of instream incubation; the latter groups contain taxa that are predicted to be capable of using organic material to fuel further breakdown. Our results suggest that incubation time is more important than leaf species physicochemistry in influencing leaf litter microbial assemblage composition, and indicate the need for investigation into seasonal and temporal dynamics of leaf litter microbial assemblage succession.</p></div

Comparison of alpha diversity metrics calculated for maple and oak leaf litter bacterial assemblages from paired-end sequencing results following 0, 32, and 128 days instream incubation at an even sampling depth of 4260 sequences.

<p>Superscript letters beside metric values represent Tukey’s multiple comparison groupings for each metric (α = 0.05).</p><p>Comparison of alpha diversity metrics calculated for maple and oak leaf litter bacterial assemblages from paired-end sequencing results following 0, 32, and 128 days instream incubation at an even sampling depth of 4260 sequences.</p

Unifrac-based unweighted pair group method with arithmetic mean (UPGMA) clustering of maple and oak sequences following 0, 32, and 128 days of instream incubation.

<p>Values at nodes represent level of clustering support expressed as a decimal ranging from 0 to 1.0.</p

Mean (± 1SE) ash free dry mass (AFDM) remaining over time during breakdown of red maple (closed circles), water oak (open circles), and mixed litter (inverted solid triangle) leaf packs incubated for 128 d in Kings Mill Creek, GA, USA.

<p>Mean (± 1SE) ash free dry mass (AFDM) remaining over time during breakdown of red maple (closed circles), water oak (open circles), and mixed litter (inverted solid triangle) leaf packs incubated for 128 d in Kings Mill Creek, GA, USA.</p

Dendrogram of ribosomal intergenic spacer analysis (RISA) electropherograms displaying bacterial assemblage similarities calculated using Ward’s method based on Jaccard’s similarity coefficient.

<p>Dendrogram of ribosomal intergenic spacer analysis (RISA) electropherograms displaying bacterial assemblage similarities calculated using Ward’s method based on Jaccard’s similarity coefficient.</p

Mean (± 1SE) % relative abundance (%) of fungal lipid markers of red maple and water oak leaf packs over the 128-d incubation In Kings Mill Creek, GA, USA.

<p>(* = <i>p</i><0.001, ns = not significantly different).</p