Victoria Werenkraut

Quality of basic data and method to identify shape affect richness–altitude relationships in meta-analysis

We compiled 109 species richness-altitude (SRA) relationships in arthropods to test the hypothesis that identification of shape and robustness of pattern are contingent on the selection of studies included in meta-analysis. We used attributes of their sampling design to distinguish three subsets of data according to stringent, intermediate, and lax selection criteria. We tested (1) whether uncertainty over identification of shape increases as the criteria of inclusion of studies relaxes and (2) whether studies that conform to stringent selection criteria show robustness in SRA patterns to variation in method used to identify shape. We identified the shape of each SRA relationship using statistical and visual methods; data sets that suggested several shapes as equally likely were sorted out by consensus. Arthropods suggested multiple forms in the SRA relationship, with predominance of hump-shaped patterns in the stringent subset. Uncertainty over identification of shape increased after application of intermediate and lax selection criteria. The method of analysis interacted with the quality of basic data to influence the relative distribution of patterns. We concluded that the gathering of large quantities of data is insufficient and that critical evaluation of literature is crucial to infer with confidence the general shape of ecological patterns in meta-analysis.

A meta-analysis of leaf-cutting ant nest effects on soil fertility and plant performance

1. Leaf‐cutting ants (LCAs) are considered as one of the most important agents of soil disturbances that affect vegetation patterns, but these assertions are based on isolated studies or anecdotal data. In this study, meta‐analysis techniques were used to quantitatively analyse the generality of these effects and determine some of their sources of variation.

The effects of ant nests on soil fertility and plant performance: a meta‐analysis

Ants are recognized as one of the major sources of soil disturbance world-wide. However, this view is largely based on isolated studies and qualitative reviews. Here, for the first time, we quantitatively determined whether ant nests affect soil fertility and plant performance, and identified the possible sources of variation of these effects. Using Bayesian mixed-models meta-analysis, we tested the hypotheses that ant effects on soil fertility and plant performance depend on the substrate sampled, ant feeding type, latitude, habitat and the plant response variable measured. Ant nests showed higher nutrient and cation content than adjacent non-nest soil samples, but similar pH. Nutrient content was higher in ant refuse materials than in nest soils. The fertilizer effect of ant nests was also higher in dry habitats than in grasslands or savannas. Cation content was higher in nests of plant-feeding ants than in nests of omnivorous species, and lower in nests from agro-ecosystems than in nests from any other habitat. Plants showed higher green/root biomass and fitness on ant nests soils than in adjacent, non-nest sites; but plant density and diversity were unaffected by the presence of ant nests. Root growth was particularly higher in refuse materials than in ant nest soils, in leaf-cutting ant nests and in deserts habitats. Our results confirm the major role of ant nests in influencing soil fertility and vegetation patterns and provide information about the factors that mediate these effects. First, ant nests improve soil fertility mainly through the accumulation of refuse materials. Thus, different refuse dump locations (external or in underground nest chambers) could benefit different vegetation life-forms. Second, ant nests could increase plant diversity at larger spatial scales only if the identity of favoured plants changes along environmental gradients (i.e. enhancing β-diversity). Third, ant species that feed on plants play a relevant role fertilizing soils, which may balance their known influence as primary consumers. Fourth, the effects of ant nests as fertility islands are larger in arid lands, possibly because fertility is intrinsically lower in these habitats. Overall, this study provide novel and quantitative evidence confirming that ant nests are key soil modifiers, emphasizing their role as ecological engineers.

Altitudinal variation in the taxonomic composition of ground‐dwelling beetle assemblages in NW Patagonia, Argentina: environmental correlates at regional and local scales

Abstract.  1. Altitudinal gradients offer a unique scenario to elucidate how the increase in harsh climatic conditions towards the top of the mountain interacts with other environmental factors at regional and local scale to influence the spatial variation in local species composition and biodiversity maintenance. We analysed the altitudinal variation in the taxonomic composition of epigaeic beetle assemblages across five mountains in north‐western Patagonia (Argentina) to address whether substantial change in species composition was associated (i) at regional spatial scale, with changes in vegetation types, and the presence of dry and moist mountains, and (ii) at local spatial scale, with variation in temperature, plant cover and richness and several soil characteristics.

Emerging Ecosystems Change the Spatial Distribution of Top Carnivores Even in Poorly Populated Areas

Humans affect biological diversity and species distribution patterns by modifying resource availability and generating novel environments where generalist species benefit and specialist species are rare. In particular, cities create local homogenization while roads fragment habitat, although both processes can increase food availability for some species that may be able to take advantage of this new source. We studied space use by birds of prey in relation to human construction, hypothesizing that these birds would be affected even in poorly populated areas. We worked in Northwestern Patagonia, Argentina, which is experiencing a high population growth, but still having very large unpopulated areas. We related the presence of raptors with different sources of human disturbance and found that both the abundance and richness of these birds were positively associated with anthropogenic environments. These results are driven mostly by a strong association between the medium-sized generalist species and these novel environments (mainly roads and cities). This may create an imbalance in intra-guild competitive abilities, modifying the normal structures of top carnivore hierarchies. Indeed, the structure of raptor communities seems to be changing, even in poorly populated areas, with anthropogenic constructions seemingly producing changes in wild areas more promptly than thought, a cause for concern in ecosystems conservation issues.

New species and phylogenetic relationships of the spider genus Coptoprepes using morphological and sequence data (Araneae: Anyphaenidae)

We present evidence from the standard cytochrome c oxidase subunit I (COI) barcoding marker and from new collections, showing that the males and females of C. ecotono Werenkraut & Ramírez were mismatched, and describe the female of that species for the first time. An undescribed male from Chile is assigned to the new species Coptoprepes laudani, together with the female that was previously thought as C. ecotono. The matching of sexes is justified after a dual cladistics analysis of morphological and sequence data in combination. New locality data and barcoding sequences are provided for other species of Coptoprepes, all endemic of the temperate forests of Chile and adjacent Argentina. Although morphology and sequences are not conclusive on the relationships of Coptoprepes species, the sequence data suggests that the species without a retrolateral tibial apophysis may belong to an independent lineage.

Phenotypic plasticity in Drosophila cactophilic species: the effect of competition, density and breeding sites.

Changes in the environmental conditions experienced by naturally occurring populations are frequently accompanied by changes in adaptive traits allowing the organism to cope with environmental unpredictability. Phenotypic plasticity is a major aspect of adaptation and it has been involved in population dynamics of interacting species. In this study, phenotypic plasticity (i.e., environmental sensitivity) of morphological adaptive traits were analyzed in the cactophilic species Drosophila buzzatii and Drosophila koepferae (Diptera: Drosophilidae) considering the effect of crowding conditions (low and high density), type of competition (intraspecific and interspecific competition) and cacti hosts (Opuntia and Columnar cacti). All traits (wing length, wing width, thorax length, wing loading and wing aspect) showed significant variation for each environmental factor considered in both Drosophila species. The phenotypic plasticity pattern observed for each trait was different within and between these cactophilic Drosophila species depending on the environmental factor analyzed suggesting that body size‐related traits respond almost independently to environmental heterogeneity. The effects of ecological factors analyzed in this study are discussed in order to elucidate the causal factors investigated (type of competition, crowding conditions and alternative host) affecting the election of the breeding site and/or the range of distribution of these cactophilic species.

La leña como vía para la introducción de insectos. ¿Cuáles son los riesgos de las invasiones de hormigas en la Patagonia?

Firewood can act as a long-distance dispersal vector for wood-infesting insects both within and among countries. Recently, we detected the alien carpenter ant Camponotus mus in firewood transported from central Argentina to Patagonia. This species generates significant economic losses in its native range and has invader potential. Moreover, global warming and the increasing anthropogenic disturbance in Patagonian ecosystems make them highly susceptible to insect invasions. This is especially alarming considering the current lack of sanitary controls of incoming goods into the region. To prevent insect introductions via firewood, it is crucial to implement a joint effort among the scientific community, control organisms, government and end user.https://doi.org/10.25260/EA.17.27.2.0.478