Living with aliens: Suboptimal ecological condition in semiaquatic snakes inhabiting a hot spot of allodiversity Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Luca Stellati, Nicolò Borgianni, Alessandra M. Bissattini, Vincenzo Buono, Phillip J. Haubrock, Paride Balzani, Elena Tricarico, Alberto F. Inghilesi, Lorenzo Tancioni, Marco Martinoli, Luca Luiselli, Leonardo Vignoli Abstract The presence of alien species can embody a form of disturbance for natural communities and the concomitant presence of alien species at different levels within the trophic chain may compromise ecosystem functionality. We studied the ecology of two species of snake (Natrix tessellata and N. natrix) in a system of five ponds with a high number of alien species at a Mediterranean area in central Italy. We evaluated the potential perturbations to ecological traits of snakes due to the presence of alien species, including their body size, population density, and food habits. We compared the studied populations' body size to that estimated in conspecific populations studied elsewhere, including populations at close distance from the study site. Distance sampling and Capture-Mark-Recapture techniques were used to calculate the population density. Diet was estimated using stomach contents and stable isotope ratios (δ15N and δ13C), using Bayesian stable isotope mixing models to estimate the contribution of food sources and species' isotopic niche spaces. Few prey items were found in the stomach contents of either species, with Ameiurus melas as the main prey. Based on isotope niche analyses, N. tessellata diet consisted of only alien species, and N. natrix diet mostly relied on alien species (>80%). Stomach contents revealed high overlap between the two species, although isotopes showed a random resource use (i.e. low isotopic niche space overlap). Overall, we caught a low number of individuals, indicating small population sizes. Moreover, snakes at the study site were comparatively smaller in size than most other populations found in the literature and almost all the recorded individuals were in very poor condition or injured by ingested alien prey. We suggest that the presence of rich allodiversity has negatively affected the snakes’ fitness by decreasing their foraging performance, increasing their risk of being preyed upon, or through other mechanisms.

Soil and topographic variation as a key factor driving the distribution of tree flora in the Amazonia/Cerrado transition Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Fernando Elias, Ben Hur Marimon Junior, Fagner Júnior Machado de Oliveira, José Carlos Antunes de Oliveira, Beatriz Schwantes Marimon Abstract We tested the hypothesis that topographic/soil gradient and ecological succession are the main factors driving the high tree diversity in a protected area in Amazonia/Cerrado transition. The gradient is a slope composed by savanna-like vegetation of rocky cerrado on the top, typical and dense savanna cerrado in the middle, and cerradão ecotonal forest in the bottom. The ecological succession is a result of Cerrado encroachment when protected from fire. The cerradão and dense cerrado were associated to higher values of clay, silt, Mg and organic matter, whereas the typical and rocky cerrado were the opposite, with highest sand, altitude and Al. The PCA analysis revealed 73% of the influence of such habitat conditions in the species distribution along the slope. The most important determinants of species distribution are the topography and soil properties, specially texture, organic matter and concentrations of Mg. The species richness was higher in the dense and typical cerrado (intermediate slope), probably due to the mutual influence of the top flora of rocky cerrado and the lower gradient flora of cerradão. The influences of topography and soil texture is probably related to the water availability, where the sandy soil and full drainage in the top of the slope provide less water supply to the vegetation (rocky cerrado) compared to the bottom (cerradão). Patches of fire-protected Cerrado encroachment are common in Bacaba Park, with forest and savanna species coexisting. The substitutions of species across space and time, corroborates our hypothesis about the successional and topographic/edaphic variations acting as the main determinant of high tree diversity in the protected area.

Previous experience and substrate matter: Plasticity in burrow digging in a South American wolf spider Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Gabriel A. De Simone, Fedra Bollatti, Anita Aisenberg, Alfredo V. Peretti Abstract Burrowing behavior can be affected by substrate conditions such as percentages of minerals, organic substances, granulometry, and biotic factors like densities of burrowing individuals, potential prey, and predators. Allocosa senex is a wolf spider that inhabits sandy areas next to rivers, lakes, and sandy coasts of the Atlantic Ocean in Argentina, Brazil, and Uruguay. This species shows reversal in sexual size dimorphism and sex roles, meaning that females are the smaller, more mobile and courting sex. Though all individuals dig burrows, the burrows of males are longer, and these are the sites where mating and oviposition occurs. The geographical distribution of this species includes coastal areas that differ in substrate granulometry, which could affect the characteristics of the burrows. Our objective was to test the occurrence of digging plasticity in A. senex in response to consecutive digging events and after sequential exposures to substrates with different granulometry. Males tended to enlarge their burrows after repeated digging events. Burrows were shorter on the fine substrate, and individuals showed greater weight loss after digging there. This could suggest that making a burrow in fine substrate is more energetically demanding than in coarse substrate. Individuals of A. senex are able to adapt their digging behavior according to substrate characteristics in order to maximize their fitness.

From dropping to dropping: The contribution of a small primate to seed dispersal in Atlantic Forest Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Carla Cristina Gestich, Mariana B. Nagy-Reis, Christini Barbosa Caselli Abstract The dynamic interaction between animals and plants through frugivory and seed dispersal is one of several ecological processes that modulates tropical biodiversity. Here we evaluated the potential role of a highly-frugivorous Neotropical primate, the black-fronted titi monkey (Callicebus nigrifrons), as seed disperser. We studied two titi monkey groups in semideciduous Atlantic Forest remnants. Each group fed on over 49 zoochorous plant species in about one year and ingested seeds from nearly a half of them, especially those with small seeds (<0.5 cm). The groups of titi monkeys defecated a large number of seeds, reaching over 300 seeds per day (1–305). More than half of the total deposited seeds and seed species germinated after gut passage, however gut passage reduced germination success in three of five evaluated species. Feces were deposited in small clumps distributed across groups’ home range. We suggest that the observed distribution pattern of feces may enhance plant reproductive fitness by increasing the probability of seeds being deposited far from parent plants, in novel and favorable sites. We concluded that the seed handling and deposition behavior of black-fronted titi monkey make this primate an important agent for Atlantic forest regeneration.

A battle of the sexes? Sex ratio and performance at small scales in dioecious Mercurialis perennis Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Tanja Pfeiffer, Leander Schmidt, Anna M. Roschanski, Martin Schnittler Abstract Mercurialis perennis is a dioecious clonal woodland herb. Its male-biased shoot sex ratio may result from differential selection (with skewed genet sex ratio) and/or differential performance (fairly even genet sex ratio but skewed shoot sex ratio since male clones grow more vigorously or have a higher flowering propensity). To test both scenarios, a total of 1024 shoots were mapped and excavated in five 1 m2 plots in an old-growth forest in northeastern Germany. SSR genotyping revealed a less skewed intrinsic male:female shoot sex ratio (1.6) and a nearly even genet sex ratio. The sexes showed intermingling rather than sexual niche segregation. Most of the 36 genets found split into numerous independent units (merigenets). A slight sexual size dimorphism (SSD) was found: male clones possess on average more shoots, have longer stolons and a higher proportion of flowering shoots. Analyses of resource allocation patterns showed 1.5–2.8 times higher costs for sexual reproduction (dry mass, nitrogen) for females. Males invest surplus resources into leaves and stolons, accentuating the SSD; although for genets the difference may be smaller due to the higher flowering rate of males (53% vs. 34%). Photosynthetic performance, deduced from rapid light curves measured with a portable fluorometer, was similar for both sexes, especially in spring; the main challenge being the transformation from light to shade plant with tree foliation. Our data indicate that differential performance accounts for the male bias in shoot sex ratio; competition between sexes is unlikely given the strongly intermingled clones.

Soil bacterial communities in the Brazilian Cerrado: Response to vegetation type and management Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Maria Regina Silveira Sartori Silva, Alinne Pereira de Castro, Ricardo Henrique Krüger, Mercedes Bustamante Abstract Pasture degradation in the Brazilian Cerrado, the second largest biome in South America, is a widespread problem that leads to serious environmental consequences. Thus pasture restoration is crucial, not only because of the economic importance of meat production in Brazil, but also for mitigation of soil erosion and the effects of climate change. Furthermore, ecosystem productivity depends on nutrient cycling and organic matter transformation in soils, highlighting the need to better understand the biological functioning of soil in natural and managed systems. Soil microbiota can be analyzed to monitor changes in soil functions, thereby serving as an indicator of ecological restoration. In the present study, we used a barcoded pyrosequencing approach to assess soil bacterial communities under three different conditions: a native cerrado area, an active pasture, and a degraded pasture that was planted with native tree species. In the three study areas, Acidobacteria was dominant phylum (20–38%), followed by Proteobacteria (8–13%), AD3 (4–12%), Verrucomicrobia (3–11%), and Firmicutes (3–8%). However, the results demonstrated a clear differentiation of soil microbial communities under native vegetation cover and pasture regardless of rainfall seasonality. The higher abundance of AD3 in the native cerrado area was an important variable differentiating natural and managed areas. Comparing the two pasture areas, the pasture under restoration treatment differed from the active pasture in terms of abundance of the most dominant phyla in the rainy period but not in the dry period. Proteobacteria was lower in the degraded pasture planted with native trees than in the active pasture, while the relative abundance of Acidobacteria showed the opposite trend. Changes in the abundance of main bacterial phyla even in the initial phases of the restoration process, point out for the relevance of microbiological parameters as additional indicators in the monitoring of degradation recovery.

Soil macrofauna as an indicator for evaluating soil based ecosystem services in agricultural landscapes Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): E. Velasquez, P. Lavelle Abstract Soils participate in the provision of numerous ecosystem services of great importance for the maintenance of ecosystems and human societies. Physical and chemical soils properties sustain supporting ecosystem services like plant production and the infiltration and provision of clean water. Carbon sequestration is a regulating ecosystem service important for climate regulation. Soils are also home of a large biodiversity whose participation in soil processes is critical for their sustainable use. Evaluating these functions to assess the provision of ecosystem services is an important challenge for which simple and accurate tools and methodologies are requested. In this work, the relationship of the soil macro-fauna with some soil-based ecosystem services was evaluated in three different regions of Colombia, Brazil and Nicaragua with rather contrasted conditions of soils and management options. In each country, we calculated a set of sub-indicators of physical quality, chemical fertility, organic matter accumulation, soil macro aggregation and macro-invertebrate communities abundance and diversity. The combination of these sub indicators in a General Indicator of Soil Quality (GISQ) provided an overall assessment of the quality of the soil and associated ecosystem services. The strong relationship observed between macrofauna indicators and soil physical, chemical and organic matter characteristics makes it a powerful tool for evaluating and monitoring soil quality.

Carabid community stability is enhanced by carabid diversity but reduced by aridity in Chinese steppes Publication date: August 2019 Source: Acta Oecologica, Volume 99 Author(s): Noelline Tsafack, Letizia Di Biase, Yingzhong Xie, Xinpu Wang, Simone Fattorini Abstract Carabids (Coleoptera, Carabidae) are an important arthropod component of grassland ecosystems, where they are involved in many important ecosystem services. Grasslands are the most widespread ecosystems in China, where they are under increasing degradation that turn productive grasslands into desert. We studied the relationships between carabid community stability and various community parameters (richness, diversity, dominance, evenness, and proportion of the most dominant species) in three types of steppes characterized by a different degree of aridity (desert, typical and meadow) in northern China. Carabid community stability was lowest in the most arid environment (i.e. the desert steppe). In the less arid steppe (i.e. the meadow steppe) stability was correlated positively with richness, diversity, and equitability, and negatively with dominance and proportion of the most abundant species. This supports the diversity hypothesis (i.e. that high levels diversity lead to higher levels of stability, possibly by increasing niche complementation) and falsifies the mass ratio hypothesis (i.e. that ecosystem processes, and hence their stability, are strongly influenced by the most dominant species). Current transformation of productive grasslands into arid lands will reduce carabid community stability and this might compromise ecosystem functioning even at moderate levels of degradation, as observed in the typical steppe.

The effects of grassland ecosystem afforestation on avian phylogenetic diversity, taxonomic diversity and evolutionary distinctiveness Publication date: August 2019 Source: Acta Oecologica, Volume 99 Author(s): Lucilene I. Jacoboski, André L. Luza, Raquel K. Paulsen, Angelo M. Pezda, Sandra M. Hartz Abstract Forest plantations are among the main threats to the grassland ecosystems of southeastern South America. One key question is whether such plantations affect the evolutionary diversity of bird communities, since previous studies have shown a reduction in taxonomic and functional diversity. High levels of phylogenetic diversity can ensure the conservation of communities, and high evolutionary potential to adapt to environmental changes. Taking this into account we investigated whether the conversion of native grasslands into forest plantations impacted the evolutionary and taxonomic diversity of bird communities, through an analysis of the different dimensions of diversity. Our investigations took place in southern Brazil where native grasslands predominate, however many have been afforested in recent years. We collected data from bird communities in native grassland and forest habitats, as well as from eucalyptus plantations. Our results did not detect a reduction in phylogenetic diversity in the planted areas but did demonstrate the taxonomic impoverishment of bird communities. Furthermore, we registered a reduction in the evolutionary distinctiveness of bird communities in forest plantations and a variation of phylogenetic composition among habitats. This indicates the evolutionary adaptations of species to their habitat, whether it is forest or grassland. Riparian forest lineages appeared more capable of colonizing forest plantations, while grassland lineages appeared unfit to do so. Afforestation of grassland ecosystems may represent a future threat to the maintenance of evolutionarily distinct bird species, as well as to strict grassland species which have been shown to be evolutionarily unable to colonize forest plantations. We recommend the maintenance of forest plantations only in areas that have already been converted or degraded. Additionally, we emphasize the importance of practicing non-intensive economic activities in these areas, for example, cattle production in low-intensity. Such activities in low-intensity have been shown to be beneficial for the maintenance of the evolutionary and taxonomic diversity of bird communities.

Low fruit-crop years of Carapa oreophila drive increased seed removal and predation by scatterhoarding rodents in a West African forest Publication date: August 2019 Source: Acta Oecologica, Volume 99 Author(s): Biplang G. Yadok, Pierre-Michel Forget, Daniel Gerhard, Hazel Chapman