How do primates affect seed germination? A meta‐analysis of gut passage effects on neotropical plants

Biotic seed dispersal is a key process maintaining biodiversity in tropical forests where most trees produce vertebrate‐dispersed seeds. Existing meta‐analyses suggest an overall positive effect of vertebrate gut passage on seed germination, but no significant effects for non‐flying mammals. However, previous meta‐analyses combined rodents (seed predators) and primates (seed dispersers) into the non‐flying mammals category, which may confound specific effects of each group on seed germination. However positive effects of monkeys on germination had previously been found in some studies. Here we disentangle the role of Neotropical primates as contributors to seed dispersal in tropical forests by running a meta‐analysis to determine the overall magnitude of gut passage effects on seed germination percentage and mean time to germination. We also compare effect sizes as a function of different feeding guilds, gut complexities, and seed size. Our results show a strong, positive effect of primates on seed germination percentage and on the number of days to first germination. Strictly frugivorous monkeys, the group most threatened by extinction, showed the highest dispersal quality, increasing germination percentage by 75%. Primates that include insects in their diets had no average effect on germination percentage or time. Gut passage had different outcomes on seeds with different sizes; both large and small seeds showed similar increases in germination percentages after gut passage, but only large seeds germinated faster than control seeds after gut passage. Our results show a relevant role for primates in providing high seed dispersal quality and as drivers of forest regeneration. The combined effects of defaunation and forest fragmentation may result in decreased regeneration of trees, which has the potential to affect negatively both forest structure and ecosystem processes. Finally, we provide general guidelines for standardizing research on seed dispersal by primates. Synthesis Consuming fleshy fruits and dispersing seeds is the main ecological service provided by vertebrates to plants. Vertebrate increases seed germination due to treatment given during digestive system passage. Previous meta‐analyses suggest an overall positive effect of vertebrate gut passage on germination, but no insights are available on its variation among different functional groups of mammals. Our analyses indicated that gut passage by Neotropical primates increased seed germination. Strict frugivores, the ones most threatened by extinction, were the most efficient. Our results show a relevant role for primates in providing high seed dispersal quality and as drivers of forest regeneration, which can be meaningful for conservation in a community scale.     

Phenotype Matching and Early Social Conditions Affect Shoaling and Exploration Decisions

Early social conditions are vital for the establishment of future social interactions. Less, however, is known about how differences in early social conditions contribute to the process of individual recognition and subsequently in the decision of associating and exploring behaviours. In this study, we address this gap in the Trinidadian guppy Poecilia reticulata and test the prediction that fish would show a higher tendency to recognize and associate with individuals of similar phenotype. This prediction was tested by comparing the likelihood of association and latency to explore a novel area in males and females when in the presence of individuals that were familiar (reared together but from different populations), from the same population of origin (from the same population but deprived of interaction with each other), or were unfamiliar (different population and have never interacted). Both early social conditions and population of origin (phenotype matching) affected the tendency to shoal and explore. Females, but not males, exhibited identical preference to associate either with unfamiliar females as with familiar females from a different population. Importantly, female preference did not occur with unfamiliar individuals from a different population. In contrast with our prediction, tendency to shoal did not predict exploration propensity. Males always start exploration before the group whenever unfamiliar males composed the group. Females on the other hand only moved to the novel area after seeing the group doing so, revealing sexual dimorphism in exploratory behaviour. Our results provide evidence for a familiarity and phenotypic matching recognition mechanism at the population level and also highlight the importance of accounting for differences between sexes when investigating the effects of early social conditions.     

Brain-derived neurotrophic factor and early-life stress: Multifaceted interplay

The brain-derived neurotrophic factor (BDNF) is a key regulator of neural development and plasticity. Long-term changes in the BDNF pathway are associated with childhood adversity and adult depression symptoms. Initially, stress-induced decreases in the BDNF pathway were found in some studies, but subsequent reports indicated the relationship between stress and BDNF to be much more complex, and the concept was significantly revised. In the present mini-review, we focus on the structure and regulation of the Bbnf gene as well as on the stress–BDNF interactions under early-life adverse conditions.     

Expression of Arabidopsis Bax Inhibitor‐1 in transgenic sugarcane confers drought tolerance

The sustainability of global crop production is critically dependent on improving tolerance of crop plants to various types of environmental stress. Thus, identification of genes that confer stress tolerance in crops has become a top priority especially in view of expected changes in global climatic patterns. Drought stress is one of the abiotic stresses that can result in dramatic loss of crop productivity. In this work, we show that transgenic expression of a highly conserved cell death suppressor, Bax Inhibitor‐1 from Arabidopsis thaliana (AtBI‐1), can confer increased tolerance of sugarcane plants to long‐term (>20 days) water stress conditions. This robust trait is correlated with an increased tolerance of the transgenic sugarcane plants, especially in the roots, to induction of endoplasmic reticulum (ER) stress by the protein glycosylation inhibitor tunicamycin. Our findings suggest that suppression of ER stress in C₄ grasses, which include important crops such as sorghum and maize, can be an effective means of conferring improved tolerance to long‐term water deficit. This result could potentially lead to improved resilience and yield of major crops in the world.     

Phytomass change in natural phytocenosis as an indicator of technogenic pollution of soils with heavy metals

This study considered the possibility of using plant community phytomass for the assessment of soil pollution with heavy metals (HM) from industrial wastes. The three-year-long field experiment was run under the regional natural meadow vegetation; the polymetallic galvanic slime was used as an industrial waste contaminant. It is shown that soil contamination primarily causes decrease of phytomass in the growing phytocenosis. The vegetation experiments determined nonlinear dependence of cultivated and wild plant biomass on the level of soil contamination; it is described by the equations of logistic and Gaussian regression. In the absence of permanent contaminants, the soil is self-cleaned over time. It reproduces phytomass mainly due to the productivity increase of the most pollution-tolerant species in the remaining phytocenosis. This phenomenon is defined as environmental hysteresis. Soil pollution by industrial waste leads to the loss of plant biodiversity. The research shows that the study of the HM impact on ecosystems is expedient given the consideration of the “soil–phytocenosis–pollutant” complex in the “dose–response” aspect. The reaction of phytocenosis on HM showing decline in phytomass leads to serious limitations in the choice of accumulating plants, because the adsorbed HM are rejected through phytomass.     

Oxygen consumption and ammonia excretion of juvenile pink shrimp (Farfantepenaeus paulensis) in culture: temperature effects

We evaluated oxygen consumption and ammonia excretion by juveniles of the pink shrimp Farfantepenaeus paulensis at three different temperatures (15, 20 and 25 °C). The shrimp were collected in the coastal region of Cananéia, São Paulo State, Brazil. The selected temperatures are the limits recorded in aquaculture tanks in the coastal region of Cananéia. We measured oxygen consumption and ammonia excretion as proxies for metabolic activity. Oxygen consumption and ammonia excretion increased with increasing temperature, but no change was observed at 15 and 20 °C. It is possible that within this temperature range, there is thermal independence in juvenile F. paulensis do not need to allocate additional energy to compensate for temperature changes because they are physiologically adapted for this range.