Cristian S. Dambros

Will the real Syrrhopodon leprieurii please stand up? The influence of topography and distance on phenotypic variation in a widespread Neotropical moss

Abstract Infra-specific variation in phenotypes of bryophytes is rarely shown to be spatially or ecologically structured. By using a morphometrics approach based on more than 2,300 measurements of nine gametophyte characters taken from 63 specimens across the global range of Syrrhopodon leprieurii Mont. (Calymperaceae), we demonstrate through partial and total Mantel analyses that phenotypes vary significantly over distance and elevation. Furthermore, S. leprieurii specimens of montane and spatially isolated (island) regions (such as the Andes and Cuba) exhibit disproportionately greater morphological differentiation over relatively shorter distances when compared to those from lowland rainforests of the greater Amazon basin. Structured morphological variation among bryophyte populations is uncommon and we suggest that, in light of results from studies of other Neotropical plant taxa, more pronounced differentiation in niche structure in this region may account for such variability.

In defense of P values: comment on the statistical methods actually used by ecologists.

In recent years, a persuasive argument has been made for the use of information criterion (IC) model selection in place of null hypothesis significance testing (NHST) based on P values (Johnson 1999, Burnham and Anderson 2002, Johnson and Omland 2004). In this issue, Murtaugh (2014) questions the basis for this argument. We comment on this paper from the perspective of early-career ecologists and present the results of an informal survey of our colleagues on their choice of statistical methods. Specifically, we ask to what extent the IC approach has supplanted traditional hypothesis testing. Finally, we address issues related to the use and interpretation of P values, the Akaike information criterion (AIC), and effect sizes in ecological studies.

Soil mesofauna in differents systems of land use soil in upper River Solimões, AM, Brazil

The mesofauna has an important function in the soil and it is represented mainly by Acari Oribatida and Collembola. We report the first data on the density and diversity of the soil mesofauna in Benjamin Constant, Amazonas State, Brazil. The following systems were evaluated: primary forest, secondary forest, agroforestry system, cultivated areas and pastures. A total of 101 samples were collected 100 m apart from each other and specimens were collected by using Berlese-Tullgren method. The highest density was registered in secondary forest (29,776 specimens.m-2). Acari Oribatida was the dominant group (7.072 specimens.m-2) in the pasture, suggesting that mites show higher capacity of adaptation to disturbed environments and/or due to the presence of gregarious species. The density of Collembola (5,632 specimens.m-2) was higher in secondary forest. Formicidae was the dominant group (27,824 specimens.m-2) and its highest density occurred in the secondary forest (12,336 specimens.m-2). Seven species and ten morphospecies of Isoptera and three species of Symphyla were identified. The highest density and diversity were found in secondary forest. One supposes that the low density of mesofauna found in all of the studied systems is being influenced by soil structure and composition as well as litter volume. For SUT, the composition of taxonomic groups in the cultivated areas is similar to the one found in primary forest, while the groups found in the agroforestry system are similar to those in the pasture, which may help to decide on land use strategies.

Isolation by distance, not rivers, control the distribution of termite species in the Amazonian rain forest

The spatial distribution of species is affected by dispersal barriers, local environmental conditions and climate. However, the effect of species dispersal and their adaptation to the environment across geographic scales is poorly understood. To investigate the distribution of species from local to broad geographic scales, we sampled termites in 198 transects distributed in 13 sampling grids in the Brazilian Amazonian forest. The sampling grids encompassed an area of 271,500 km2 and included the five major biogeographic regions delimited by Amazonian rivers. Environmental data for each transect were obtained from local measurements and remote sensing. Similar to previous studies, termite species composition at the local scale was mostly associated with measures of soil texture and chemistry. In contrast, termite species composition at broad geographic scales was associated with soil nutrients, and the geographic position of the transects. Between 17% and 30% of the variance in termite species composition could be attributed exclusively to the geographic position of the transects, but could not be attributed to measured environmental variables or the presence of major rivers. Isolation by distance may have strong effects on termite species composition due to historic processes and the spatially structured environments along distinct geological formations of Amazonia. However, in contrast to many taxa in Amazonia, there is no evidence that major rivers are important barriers to termite dispersal. This article is protected by copyright. All rights reserved.

Effects of neutrality and productivity on mammal richness and evolutionary history in Australia

Explaining how heterogeneous spatial patterns of species diversity emerge is one of the most fascinating questions of biogeography. One of the great challenges is revealing the mechanistic effect of environmental variables on diversity. Correlative analyses indicate that productivity is associated with taxonomic, phylogenetic, and functional diversity of communities. Surprisingly, no unifying body of theory have been developed to understand the mechanism by which spatial variation of productivity affects the fundamental processes of biodiversity. Based on widely discussed verbal models in ecology about the effect of productivity on species diversity, we developed a spatially explicit neutral model that incorporates the effect of primary productivity on community size and confronted our model’s predictions with observed patterns of species richness and evolutionary history of Australian terrestrial mammals. The imposed restrictions on community size create larger populations in areas of high productivity, which increases community turnover and local speciation, and reduces extinction. The effect of productivity on community size modeled in our study causes higher accumulation of species diversity in productive regions even in the absence of niche-based processes. However, such a simple model is not capable of reproducing spatial patterns of mammal evolutionary history in Australia, implying that more complex evolutionary mechanisms are involved. Our study demonstrates that the overall patterns of species richness can be directly explained by changes in community sizes along productivity gradients, supporting a major role of processes associated with energetic constraints in shaping diversity patterns.

Termite species list in a terra firme and ghost forest associated with a hydroelectric plant in Presidente Figueiredo, Amazonas, Brazil

Termites are among the most important groups to maintain tropical forests but despite their importance they are poorly studied. Termites were sampled in the trunks left over from the flood period in the Balbina Hydroelectric plant (UHB). The trunks are in the water and just partially submersed without contact with the mainland. We compared the species composition with the surrounding terra firme forest. This is the first list of species provided for this area from a standardized sampling and we provide some insights into how these degraded areas can be important to study species distribution and have potential for the discovery of new species of termites. We found that the change in the environment can drastically change the species composition and some rare species in the natural landscape can be more easily detectable in these areas.