Pre-tests, Two-sample t test, Welch-test, Wilcoxon-U test,
Mutualism, whereby species interact to their mutual benefit, is extraordinary in a competitive world. To recognize general patterns of origin and maintenance from the plethora of mutualistic associations proves a persisting challenge. The simplest situation is believed to be that of a single mutualist specific to a single host, vertically transmitted from one host generation to the next. We characterized ascomycete fungal associates cultured for nest architecture by the ant subgenera Dendrolasius and Chthonolasius. The ants probably manage their fungal mutualists by protecting them against fungal competitors. The ant subgenera display different ant-to-fungus specificity patterns, one-to-two and manyto-one, and we infer vertical transmission, in the latter case overlaid by horizontal transmission. Possible evolutionary trajectories include a reversal from fungiculture by other Lasius subgenera and inheritance of fungi through life cycle interactions of the ant subgenera. The mosaic indicates how specificity patterns can be shaped by an interplay between host life-cycles and transmission adaptations.insect fungiculture ͉ Lasius ants ͉ mutualism ͉ social insects C ooperation is improbable (1, 2) and it is only through evolution that these interactions become reliable for the players. Cooperation is needed to forge new levels of organization, from genomes to human society (2). Mutualism, species interactions beneficial for all players, offers some of the most arresting cases of evolution (3). These cases stimulated the development of theoretical frameworks on the why and how of mutualism (e.g., refs. 3-7), but true life examples are needed to test any hypothesis (8). Finding suitable model systems is not a trivial task (9). Only a fraction of the extant associations have been studied (10), with the number and identities of the players often unknown.Insect fungiculture provides prime systems for studying mutualism (11). The New World attine ants (Myrmicinae: Attini) that cultivate fungi for food have especially served as models for investigating host-use specificity and transmission patterns (12-15). Another ant-fungus association has been less investigated: Old World Lasius ants (Formicinae) of the subgenera Dendrolasius and Chthonolasius nourish fungi with honeydew to bind shredded wood or soil into a composite building material (16,17). The fungi are used for reinforcement of the nest walls, which allows building stable nests in tree and soil cavities. Little has been known about the associations' phylogenetic and ecological specificities, and the transmission mode, but it has been generally accepted (18) that the Lasius-fungi associations are simple with each of the two subgenera culturing a single fungus (19)(20)(21)(22). Chthonolasius and Dendrolasius are both obligate temporary social parasites, i.e., young queens enter an established colony of another Lasius subgenus and replace the queen. Dendrolasius is confined to the Palearctic and hyperparasitizes Chthonolasius (16). Chthonolasius exhibits complexity wit...
Plant root systems have a key role in ecology and agronomy. In spite of fast increase in root studies, still there is no classification that allows distinguishing among distinctive characteristics within the diversity of rooting strategies. Our hypothesis is that a multivariate approach for “plant functional type” identification in ecology can be applied to the classification of root systems. The classification method presented is based on a data-defined statistical procedure without a priori decision on the classifiers. The study demonstrates that principal component based rooting types provide efficient and meaningful multi-trait classifiers. The classification method is exemplified with simulated root architectures and morphological field data. Simulated root architectures showed that morphological attributes with spatial distribution parameters capture most distinctive features within root system diversity. While developmental type (tap vs. shoot-borne systems) is a strong, but coarse classifier, topological traits provide the most detailed differentiation among distinctive groups. Adequacy of commonly available morphologic traits for classification is supported by field data. Rooting types emerging from measured data, mainly distinguished by diameter/weight and density dominated types. Similarity of root systems within distinctive groups was the joint result of phylogenetic relation and environmental as well as human selection pressure. We concluded that the data-define classification is appropriate for integration of knowledge obtained with different root measurement methods and at various scales. Currently root morphology is the most promising basis for classification due to widely used common measurement protocols. To capture details of root diversity efforts in architectural measurement techniques are essential.
A spatially based, river type-specific approach was used to develop an ecological assessment method for European rivers based on existing sampling data. The methodology comprised two main steps: (1) description of a river and fish assemblage typology based on minimally or slightly impacted sites and (2) analyses of impacted conditions for each type. Hierarchical cluster analysis of fish species assemblages identified 15 homogeneous groups in 11 European ecoregions. Discriminant analyses, based on abiotic characteristics, were used to predict fish types at impacted sites. The latter encompassed both regional (geographic position in Europe) and local factors (longitudinal zonation) influencing the distribution of riverine fishes. To assess ecological status, the responses of more than 400 metrics (species composition, abundance and age-length structure) to human pressures were tested for each river type separately. A maximum of 10 metrics per river type was selected using discriminant analysis. The density of intolerant species and feeding guilds had the highest capacity to predict the intensity of perturbation.K E Y
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