dataFig2a_3

Influence of the migration rate eta on the equilibrium percentage of sexual females in the 20 patches for varying resource diversity L (simulated electronically), eta=0.0

dataFig2b_3

Influence of the migration rate eta on the equilibrium percentage of sexual females in the 20 patches for varying mortality strength 1/n (simulated electronically), eta=0.0

Response of oribatid mite species.

<p>Detrended correspondence analysis of oribatid mite species and subgroups (given in different colours; see small graph in figure) with sampling time included as supplementary variable not affecting the ordination (time 1 = 2 weeks, time 2 = 10 weeks, time 3 = 20 weeks, time 4 = 44 weeks). Bold names indicate sexual reproduction. <i>Ache cole</i>  =  <i>Achipteria coleoptrata</i>, <i>Bank lanc</i>  =  <i>Banksinoma lanceata, Bern sigm</i>  =  <i>Berniella sigma</i>, <i>Brac berl</i>  =  <i>Brachychthonius berlesei</i>, Brachych  =  Brachychthoniidae, <i>Cara femo</i>  =  <i>Carabodes femoralis</i>, <i>Cara orna</i>  =  <i>Carabodes ornatus</i>, <i>Cult bicu</i>  =  <i>Cultroribula bicultrata</i>, <i>Diss orna</i>  =  <i>Disshorina ornata, Enio minu</i>  =  <i>Eniochthonius minutissimus, Galu lanc</i>  =  <i>Galumna lanceata</i>, <i>Lioc</i> spec  =  <i>Liochthonius</i> sp., <i>Mala grac</i>  =  <i>Malaconothrus gracilis, Medi subp</i>  =  <i>Medioppia subpectinata, Medi minu</i>  =  <i>Microppia minus, Minu semi</i>  =  <i>Minunthozetes semirufus</i>, <i>Nanh coro</i>  =  <i>Nanhermannia coronata, Nanh nana</i>  =  <i>Nanhermannia nana, Noth silv</i>  =  <i>Nothrus silvestris</i>, <i>Ophi tect</i>  =  <i>Ophidiotrichus tectus, Oppi nova</i>  =  <i>Oppiella nova, Orib tibi</i>  =  <i>Oribatula tibialis</i>, Phthirac  =  Phthiracaridae, <i>Rhys dupli</i>  =  <i>Rhysotritia duplicata</i>, <i>Sell hone</i>  =  <i>Sellnickochthonius honestus</i>, <i>Suct</i> spec  =  <i>Suctobelbella</i> sp., <i>Suct subc</i>  =  <i>Suctobelbella subcornigera, Suct subt</i>  =  <i>Suctobelbella subtrigona, Tect mino</i>  =  <i>Tectocepheus minor</i>.</p

Carbon mineralization.

<p>(a) Average daily carbon mineralization as affected by resource manipulation (control, reduced litter quality, glucose addition) and temperature (10, 15, 20°C), and (b) cumulative carbon mineralization during 34 weeks of incubation in the respective treatments. “ctr” =  control (solid line), “−” =  reduced litter quality (broken line), “+” =  glucose addition (dashed line).</p

Stability of community productivity as affected by bacterial genotypic and functional diversity.

<p>Effects of bacterial genotypic (a, b) and functional diversity (c, d) on the stability of community productivity in varied resource environments (1/coefficient of variation of 14 resource treatments) (a, c) and invader treatments (no invader, <i>Pseudomonas putida</i> and <i>Serratia liquefaciens</i> as model invaders) (b, d). Each circle represents the stability of productivity of a given bacterial community in varied abiotic (a, c) or biotic environments (b, d).</p

dataFig1b

Average equilibrium percentage of sexual females in dependence of intrinsic growth rate of resources G (simulated electronically), here no migration is allowed, i.e., migration rate eta=

dataFig2b_1

Influence of the migration rate eta on the equilibrium percentage of sexual females in the 20 patches for varying mortality strength 1/n (simulated electronically), eta=0.0

dataFig1c

Average equilibrium percentage of sexual females in dependence of mortality strength 1/n (simulated electronically), here no migration is allowed, i.e., migration rate eta=

Resource Availability as Driving Factor of the Reproductive Mode in Soil Microarthropods (Acari, Oribatida)

<div><p>The availability of high quality resources is an important factor driving community structure and reproductive mode of animals. Parthenogenetic reproduction prevails when resources are available in excess, whereas sexuality correlates with resource shortage. We investigated the effect of resource availability on the community structure of oribatid mites in a laboratory experiment. Availability of food resources was increased by addition of glucose to leaf litter and reduced by leaching of nutrients from leaf litter. Experimental systems were incubated at three different temperatures to establish different regimes of resource exploitation. Community structure of oribatids and numbers of eggs per female were measured over a period of ten months. We expected the density of oribatid mites to decline in the reduced litter quality treatment but to increase in the glucose treatment. Both effects were assumed to be more pronounced at higher temperatures. We hypothesized sexual species to be less affected than parthenogenetic species by reduced resource quality due to higher genetic diversity allowing more efficient exploitation of limited resources, but to be outnumbered by parthenogenetic species in case of resource addition due to faster reproduction. In contrast to our hypotheses, both sexual and parthenogenetic oribatid mite species responded similarly with their densities declining uniformly during incubation. The parthenogenetic Brachychthoniidae and <i>Tectocepheus</i> dominated early in the experiment but were replaced later by parthenogenetic Desmonomata and <i>Rhysotritia</i>. In parthenogenetic species the number of eggs per female increased during the experiment while the number of eggs in sexual females remained constant or decreased slightly; in general, egg numbers were higher in sexual than in parthenogenetic species. The results indicate that for sustaining oribatid mite populations other resources than litter and associated saprotrophic microorganisms are needed. They also indicate that there are two groups of parthenogenetically reproducing species: exploiters of easily available resources and consumers of leaf litter associated resources.</p></div

Bacterial Diversity Stabilizes Community Productivity

<div><h3>Background</h3><p>Stability is a crucial ecosystem feature gaining particular importance in face of increasing anthropogenic stressors. Biodiversity is considered to be a driving biotic force maintaining stability, and in this study we investigate how different indices of biodiversity affect the stability of communities in varied abiotic (composition of available resources) and biotic (invasion) contexts.</p> <h3>Methodology/Principal Findings</h3><p>We set up microbial microcosms to study the effects of genotypic diversity on the reliability of community productivity, defined as the inverse of the coefficient of variation of across-treatment productivity, in different environmental contexts. We established a bacterial diversity gradient ranging from 1 to 8 <em>Pseudomonas fluorescens</em> genotypes and grew the communities in different resource environments or in the presence of model invasive species. Biodiversity significantly stabilized community productivity across treatments in both experiments. Path analyses revealed that different aspects of diversity determined stability: genotypic richness stabilized community productivity across resource environments, whereas functional diversity determined stability when subjected to invasion.</p> <h3>Conclusions/Significance</h3><p>Biodiversity increases the stability of microbial communities against both biotic and abiotic environmental perturbations. Depending on stressor type, varying aspects of biodiversity contribute to the stability of ecosystem functions. The results suggest that both genetic and functional diversity need to be preserved to ensure buffering of communities against abiotic and biotic stresses.</p> </div