Within-plant distribution of the Melaleuca quinquenervia biological control agent Lophodiplosis trifida

The gall-producing midge Lophodiplosis trifida Gagné (Diptera: Cecidomyiidae) is an established biological control agent of the exotic tree Melaleuca quinquenervia (Cav.) Blake, which invades wetland systems of Florida (USA). Host use patterns within the tree canopy were investigated. Plant height affected within-plant distribution of galls as L. trifida attack rates were greater in lower versus higher portions of the M. quinquenervia canopy. Nonetheless, galls occurred even at tree-top levels of 13 m.     

Wider sampling reveals a non‐sister relationship for geographically contiguous lineages of a marine mussel

The accuracy of phylogenetic inference can be significantly improved by the addition of more taxa and by increasing the spatial coverage of sampling. In previous studies, the brown mussel Perna perna showed a sister–lineage relationship between eastern and western individuals contiguously distributed along the South African coastline. We used mitochondrial (COI) and nuclear (ITS) sequence data to further analyze phylogeographic patterns within P. perna. Significant expansion of the geographical coverage revealed an unexpected pattern. The western South African lineage shared the most recent common ancestor (MRCA) with specimens from Angola, Venezuela, and Namibia, whereas eastern South African specimens and Mozambique grouped together, indicating a non‐sister relationship for the two South African lineages. Two plausible biogeographic scenarios to explain their origin were both supported by the hypotheses‐testing analysis. One includes an Indo‐Pacific origin for P. perna, dispersal into the Mediterranean and Atlantic through the Tethys seaway, followed by recent secondary contact after southward expansion of the western and eastern South African lineages. The other scenario (Out of South Africa) suggests an ancient vicariant divergence of the two lineages followed by their northward expansion. Nevertheless, the “Out of South Africa” hypothesis would require a more ancient divergence between the two lineages. Instead, our estimates indicated that they diverged very recently (310 kyr), providing a better support for an Indo‐Pacific origin of the two South African lineages. The arrival of the MRCA of P. perna in Brazil was estimated at 10 [0–40] kyr. Thus, the hypothesis of a recent introduction in Brazil through hull fouling in wooden vessels involved in the transatlantic itineraries of the slave trade did not receive strong support, but given the range for this estimate, it could not be discarded. Wider geographic sampling of marine organisms shows that lineages with contiguous distributions need not share a common ancestry.     

Allometric scaling relationship between above‐ and below‐ground biomass within and across five woody seedlings

Allometric biomass allocation theory predicts that leaf biomass (M_L) scaled isometrically with stem (M_S) and root (M_R) biomass, and thus above‐ground biomass (leaf and stem) (M_A) and root (M_R) scaled nearly isometrically with below‐ground biomass (root) for tree seedlings across a wide diversity of taxa. Furthermore, prior studies also imply that scaling constant should vary with species. However, litter is known about whether such invariant isometric scaling exponents hold for intraspecific biomass allocation, and how variation in scaling constants influences the interspecific scaling relationship between above‐ and below‐ground biomass. Biomass data of seedlings from five evergreen species were examined to test scaling relationships among biomass components across and within species. Model Type II regression was used to compare the numerical values of scaling exponents and constants among leaf, stem, root, and above‐ to below‐ground biomass. The results indicated that M_L and M_S scaled in an isometric or a nearly isometric manner with M_R, as well as M_A to M_R for five woody species. Significant variation was observed in the Y‐intercepts of the biomass scaling curves, resulting in the divergence for intraspecific scaling and interspecific scaling relationships for M_L versus M_S and M_L versus M_R, but not for M_S versus M_R and M_A versus M_R. We conclude, therefore, that a nearly isometric scaling relationship of M_A versus M_R holds true within each of the studied woody species and across them irrespective the negative scaling relationship between leaf and stem.     

Interaction effects between weather and space use on harvesting effort and patterns in red deer

Most cervid populations in Europe and North America are managed through selective harvesting, often with age‐ and sex‐specific quotas, with a large influence on the population growth rate. Less well understood is how prevailing weather affects harvesting selectivity and off‐take indirectly through changes in individual animal and hunter behavior. The behavior and movement patterns of hunters and their prey are expected to be influenced by weather conditions. Furthermore, habitat characteristics like habitat openness are also known to affect movement patterns and harvesting vulnerability, but how much such processes affect harvest composition has not been quantified. We use harvest data from red deer (Cervus elaphus) to investigate how weather and habitat characteristics affect behavioral decisions of red deer and their hunters throughout the hunting season. More specifically, we look at how sex and age class, temperature, precipitation, moon phase, and day of week affect the probability of being harvested on farmland (open habitat), hunter effort, and the overall harvest numbers. Moon phase and day of week were the strongest predictors of hunter effort and harvest numbers, with higher effort during full moon and weekends, and higher numbers during full moon. In general, the effect of fall weather conditions and habitat characteristics on harvest effort and numbers varied through the season. Yearlings showed the highest variation in the probability of being harvested on farmland through the season, but there was no effect of sex. Our study is among the first to highlight that weather may affect harvesting patterns and off‐take indirectly through animal and hunter behavior, but the interaction effects of weather and space use on hunter behavior are complicated, and seem less important than hunter preference and quotas in determining hunter selection and harvest off‐take. The consideration of hunter behavior is therefore key when forming management rules for sustainable harvesting.     

Characteristics and metabolic patterns of soil methanogenic archaea communities in the high‐latitude natural forested wetlands of China

Soil methanogenic microorganisms are one of the primary methane‐producing microbes in wetlands. However, we still poorly understand the community characteristic and metabolic patterns of these microorganisms according to vegetation type and seasonal changes. Therefore, to better elucidate the effects of the vegetation type and seasonal factors on the methanogenic community structure and metabolic patterns, we detected the characteristics of the soil methanogenic mcrA gene from three types of natural wetlands in different seasons in the Xiaoxing''an Mountain region, China. The results indicated that the distribution of Methanobacteriaceae (hydrogenotrophic methanogens) was higher in winter, while Methanosarcinaceae and Methanosaetaceae accounted for a higher proportion in summer. Hydrogenotrophic methanogenesis was the dominant trophic pattern in each wetland. The results of principal coordinate analysis and cluster analysis showed that the vegetation type considerably influenced the methanogenic community composition. The methanogenic community structure in the Betula platyphylla–Larix gmelinii wetland was relatively different from the structure of the other two wetland types. Indicator species analysis further demonstrated that the corresponding species of indicator operational taxonomic units from the Alnus sibirica wetland and the Betula ovalifolia wetland were similar. Network analysis showed that cooperative and competitive relationships exist both within and between the same or different trophic methanogens. The core methanogens with higher abundance in each wetland were conducive to the adaptation to environmental disturbances. This information is crucial for the assessment of metabolic patterns of soil methanogenic archaea and future fluxes in the wetlands of the Xiaoxing''an Mountain region given their vulnerability.     

Use of ring recoveries to predict habitat suitability in small passerines

Aim Abundance of small passerines may be distributed over large wintering areas according to geographical patterns that are difficult to detect. This may prevent the identification and conservation of the most suitable sectors, or the detection of local and regional features affecting the species during winter. In this paper, we explore the usefulness of ring recoveries to predict bird distribution in wintering grounds by using Maxent, one of the presence‐only techniques available for modelling species distributions. We test whether suitability indices obtained in 2.5 × 2.5 km UTM squares from ring recoveries were positively correlated with the actual abundance of robins (Erithacus rubecula) and blackcaps (Sylvia atricapilla) inside the squares. Location Spain. Methods We used 686 and 1139 localities across the country in which blackcap and robin ring recoveries were recorded by the Spanish Office of Migratory Species to generate the suitability maps. In addition, we sampled bird abundance inside 70 control squares independent of ring recovery localities along a belt crossing mountains, highlands and lowlands of the Iberian Peninsula during January from 2006 to 2011. Results Suitability indices predicted by Maxent were positively correlated with robin (r = 0.42, n = 70, P < 0.001) and blackcap (r = 0.52, n = 70, P < 0.001) abundances in the 70 control squares along the belt crossing the Iberian Peninsula. Main conclusions These results suggest that the use of distribution models with ring recoveries may be used to describe the habitat suitability of the winter ranges of small, common passerines. This also means that the huge number of ring recoveries stored in national and transnational data banks could be used to explore the factors shaping bird ranges and to forecast the geographical distribution of suitable wintering areas of migratory birds in large, poorly known regions. This may be useful in biogeography and conservation.     

Precipitation manipulation experiments--challenges and recommendations for the future

Climatic changes, including altered precipitation regimes, will affect key ecosystem processes, such as plant productivity and biodiversity for many terrestrial ecosystems. Past and ongoing precipitation experiments have been conducted to quantify these potential changes. An analysis of these experiments indicates that they have provided important information on how water regulates ecosystem processes. However, they do not adequately represent global biomes nor forecasted precipitation scenarios and their potential contribution to advance our understanding of ecosystem responses to precipitation changes is therefore limited, as is their potential value for the development and testing of ecosystem models. This highlights the need for new precipitation experiments in biomes and ambient climatic conditions hitherto poorly studied applying relevant complex scenarios including changes in precipitation frequency and amplitude, seasonality, extremity and interactions with other global change drivers. A systematic and holistic approach to investigate how soil and plant community characteristics change with altered precipitation regimes and the consequent effects on ecosystem processes and functioning within these experiments will greatly increase their value to the climate change and ecosystem research communities. Experiments should specifically test how changes in precipitation leading to exceedance of biological thresholds affect ecosystem resilience and acclimation.     

Subsampling Herbarium Collections to Assess Geographic Diversity Gradients: A Case Study with Endemic Orchidaceae and Rubiaceae in Cameroon

We compiled herbarium specimen data to provide an improved characterization of geographic patterns of diversity using indices of species diversity and floristic similarity based on rarefaction principles. A dataset of 3650 georeferenced plant specimens belonging to Orchidaceae and Rubiaceae endemic to Atlantic Central Africa was assembled to assess species composition per half‐degree or one‐degree grid cells. Local diversity was measured by the expected number of species (S_k) per grid cell found in subsamples of increasing size and compared with raw species richness (S_R). A nearly unbiased estimator of the effective number of species per grid cell was also used, allowing quantification of ratios of ‘true diversity’ between grid cells. Species turnover was measured using a presence/absence‐based similarity index (Sørensen) and an abundance‐based index that corrects for sampling bias (NNESS). Our results confirm that the coastal region of Cameroon is more diverse in endemic species than those more inland. The southern part of this coastal forest is, however, as diverse as the more intensively inventoried northern part, and should also be recognized as an important center of endemism. A strong congruence between Sørensen and NNESS similarity matrices lead to similar delimitations of floristic units. Hence, heterogeneous sampling seems to confer more bias when measuring patterns of local diversity using raw species richness than species turnover using Sørensen index. Overall, we argue that subsampling methods represent a useful way to assess diversity gradients using herbarium specimens while correcting for heterogeneous sampling effort. Abstract in French is available in the online version of this article.