Wright A.,German Center for Integrative Biodiversity Research iv |
Wright A.,University of Wisconsin - Milwaukee |
Schnitzer S.A.,University of Wisconsin - Milwaukee |
Reich P.B.,University of Minnesota |
Reich P.B.,University of Western Sydney
Ecology | Year: 2014
Recent work has demonstrated that competition and facilitation likely operate jointly in plant communities, but teasing out the relative role of each has proven difficult. Here we address how competition and facilitation vary with seasonal fluctuations in environmental conditions, and how the effects of these fluctuations change with plant ontogeny. We planted three sizes of pine seedlings (Pinus strobus) into an herbaceous diversity experiment and measured pine growth every two weeks for two growing seasons. Both competition and facilitation occurred at different times of year between pines and their neighbors. Facilitation was important for the smallest pines when environmental conditions were severe. This effect decreased as pines got larger. Competition was stronger than facilitation overall and outweighed facilitative effects at annual time scales. Our data suggest that both competition and the counter-directional effects of facilitation may be more common and more intense than previously considered. © 2014 by the Ecological Society of America.
Lentendu G.,University of Leipzig |
Lentendu G.,Helmholtz Center for Environmental Research |
Wubet T.,Helmholtz Center for Environmental Research |
Wubet T.,German Center for Integrative Biodiversity Research iv |
And 4 more authors.
Molecular Ecology | Year: 2014
To understand the fine-scale effects of changes in nutrient availability on eukaryotic soil microorganisms communities, a multiple barcoding approach was used to analyse soil samples from four different treatments in a long-term fertilization experiment. We performed PCR amplification on soil DNA with primer pairs specifically targeting the 18S rRNA genes of all eukaryotes and three protist groups (Cercozoa, Chrysophyceae-Synurophyceae and Kinetoplastida) as well as the ITS gene of fungi and the 23S plastid rRNA gene of photoautotrophic microorganisms. Amplicons were pyrosequenced, and a total of 88 706 quality filtered reads were clustered into 1232 operational taxonomic units (OTU) across the six data sets. Comparisons of the taxonomic coverage achieved based on overlapping assignment of OTUs revealed that half of the eukaryotic taxa identified were missed by the universal eukaryotic barcoding marker. There were only little differences in OTU richness observed between organic- (farmyard manure), mineral- and nonfertilized soils. However, the community compositions appeared to be strongly structured by organic fertilization in all data sets other than that generated using the universal eukaryotic 18S rRNA gene primers, whereas mineral fertilization had only a minor effect. In addition, a co-occurrence based network analysis revealed complex potential interaction patterns between OTUs from different trophic levels, for example between fungivorous flagellates and fungi. Our results demonstrate that changes in pH, moisture and organic nutrients availability caused shifts in the composition of eukaryotic microbial communities at multiple trophic levels. © 2014 John Wiley & Sons Ltd.
Jakob S.S.,Leibniz Institute of Plant Genetics and Crop Plant Research |
Rodder D.,Zoologisches Forschungsmuseum Alexander Koenig |
Engler J.O.,Zoologisches Forschungsmuseum Alexander Koenig |
Engler J.O.,University of Gottingen |
And 6 more authors.
Genome Biology and Evolution | Year: 2014
Studies of Hordeum vulgare subsp. spontaneum, the wild progenitor of cultivated barley, have mostly relied on materials collected decades ago and maintained since then ex situ in germplasm repositories. We analyzed spatial genetic variation in wild barley populations collected rather recently, exploring sequence variations at seven single-copy nuclear loci, and inferred the relationships among these populations and toward the genepool of the crop. The wild barley collection covers the whole natural distribution area from the Mediterraneanto Middle Asia. Incontrast to earlier studies, Bayesian assignment analyses revealed three population clusters, in the Levant, Turkey, and east of Turkey, respectively. Genetic diversity was exceptionally high in the Levant, while eastern populations were depleted of private alleles. Species distribution modeling based on climate parameters and extant occurrence points of the taxon inferred suitable habitat conditions during the ice-age, particularly in the Levant and Turkey. Together with the ecologically wide range of habitats, they might contribute to structured but long-term stable populations in this region and their high genetic diversity. For recently collected individuals, Bayesian assignment to geographic clusters was generally unambiguous, but materials from genebanks often showed accessions that were not placed according to their assumed geographic origin or showed traces of introgression from cultivated barley. We assign this to gene flow among accessions during ex situ maintenance. Evolutionary studies based on such materials might therefore result in wrong conclusions regarding the history of the species or the origin and mode of domestication of the crop, depending on the accessions included. © The Author(s) 2014.
Seiferling I.,University of Quebec at Trois - Rivieres |
Proulx R.L.,University of Quebec at Trois - Rivieres |
Wirth C.,University of Leipzig |
Wirth C.,German Center for Integrative Biodiversity Research iv
Ecology | Year: 2014
Decades of study have attempted to define a generalized environmentalheterogeneity- biodiversity (EH-BD) relationship, with the traditional MacArthurian nichebased hypothesis remaining as the dominant reference point; i.e., increasing heterogeneity promotes biodiversity by increasing resource opportunities. However, studies have frequently reported negative or nonsignificant relationships. In a vast majority of them, environmental heterogeneity was defined along a gradient of increasing randomness, toward complete disorder. A new conceptual framework could help to reconcile the array of observed relationships. Using an extensive literature review, we test a conceptual framework proposing that the direction of environmental-heterogeneity-biodiversity relationships is contingent on the level of human footprint to which an ecosystem is subjected (the anthropocline). The results reveal that highly modified and seminatural ecosystems are characterized by a dominance of positive and negative EH-BD relationships, respectively, whereas natural ecosystems show mixed responses. Out of this novel framework arises the revised perspective that natural ecosystems are typified, not by maximal or minimal, but by intermediate levels of environmental heterogeneity. © 2014 by the Ecological Society of America.
Freyhof J.,German Center for Integrative Biodiversity Research iv |
Sayyadzadeh G.,Shiraz University |
Esmaeili H.R.,Shiraz University |
Geiger M.,Leibniz Institute for Animal Biodiversity
Ichthyological Exploration of Freshwaters | Year: 2015
The Iranian species of Paraschistura are reviewed, and diagnoses are presented for all eleven recognized species. Paraschistura bampurensis, P. cristata, P. kessleri, P. nieiseni and P. turcmenica are considered valid; P. sargadensis is a synonym of P. kessleri and P. turcomanus is a synonym of P. turcmenica. Six new species are described. Paraschistura abdolii, new species, from the Sirjan basin and the western tributaries of the Hamun-e Jaz Murian basin is distinguished by having a very slender body and scales restricted to the caudal peduncle and to the back in front of the dorsal-fin origin in few individuals. Paraschistura aredvii, new species, from the Zohreh drainage, is distinguished by having scales on the back, no suborbital flap and the pelvic-fin origin posterior to the dorsal-fin origin. Paraschistura hormuzensis, new species, from the Minab drainage, is distinguished by having scales on the back, a pointed snout and a triangular suborbital flap in males. Paraschistura naumanni, new species, from the Kol drainage, the Mond drainage and the Lake Maharlo basin, is distinguished by having scales on the back, no suborbital flap in males and the pelvic-fin origin below the dorsal-fin origin. Paraschistura pasatigris, new species, from the Karun and Karkheh drainages, is distinguished by having scales on the back and a suborbital flap in males pointed downwards. Paraschistura susiani, new species, from the Jarahi drainage, is distinguished by having scales on the back and a roundish suborbital flap in males. The presence of an additional undescribed species is suggested from the Mond River drainage by the molecular data presented. All species, except unstudied P. kessleri are also characterized by fixed diagnostic nucleotide substitutions in the mtDNA COI barcode region. Paraschistura Prokofiev, 2009 is given precedence over Metaschistura Prokofiev, 2009. © 2015 by Verlag Dr. Friedrich Pfeil, München, Germany.