Species traits and interaction rules shape a species‐rich seed‐dispersal interaction network

Species phenotypic traits affect the interaction patterns and the organization of seed‐dispersal interaction networks. Understanding the relationship between species characteristics and network structure help us understand the assembly of natural communities and how communities function. Here, we examine how species traits may affect the rules leading to patterns of interaction among plants and fruit‐eating vertebrates. We study a species‐rich seed‐dispersal system using a model selection approach to examine whether the rules underlying network structure are driven by constraints in fruit resource exploitation, by preferential consumption of fruits by the frugivores, or by a combination of both. We performed analyses for the whole system and for bird and mammal assemblages separately, and identified the animal and plant characteristics shaping interaction rules. The structure of the analyzed interaction network was better explained by constraints in resource exploitation in the case of birds and by preferential consumption of fruits with specific traits for mammals. These contrasting results when looking at bird–plant and mammal–plant interactions suggest that the same type of interaction is organized by different processes depending on the assemblage we focus on. Size‐related restrictions of the interacting species (both for mammals and birds) were the most important factors driving the interaction rules. Our results suggest that the structure of seed‐dispersal interaction networks can be explained using species traits and interaction rules related to simple ecological mechanisms.     

Trading heat and hops for water: Dehydration effects on locomotor performance,thermal limits,and thermoregulatory behavior of a terrestrial toad

Due to their highly permeable skin and ectothermy, terrestrial amphibians are challenged by compromises between water balance and body temperature regulation. The way in which such compromises are accommodated, under a range of temperatures and dehydration levels, impacts importantly the behavior and ecology of amphibians. Thus, using the terrestrial toad Rhinella schneideri as a model organism, the goals of this study were twofold. First, we determined how the thermal sensitivity of a centrally relevant trait—locomotion—was affected by dehydration. Secondly, we examined the effects of the same levels of dehydration on thermal preference and thermal tolerance. As dehydration becomes more severe, the optimal temperature for locomotor performance was lowered and performance breadth narrower. Similarly, dehydration was accompanied by a decrease in the thermal tolerance range. Such a decrease was caused by both an increase in the critical minimal temperature and a decrease in the thermal maximal temperature, with the latter changing more markedly. In general, our results show that the negative effects of dehydration on behavioral performance and thermal tolerance are, at least partially, counteracted by concurrent adjustments in thermal preference. We discuss some of the potential implications of this observation for the conservation of anuran amphibians.     

Quantitative conservation genetics of wild and managed bees

Quantitative genetic traits provide insights into the evolutionary potential of populations, as heritability estimates measure the population’s ability to respond to global changes. Although wild and managed bees are increasingly threatened by the degradation of natural habitats and climate change, risking plant biodiversity and agriculture production, no study has yet performed a systematic review of heritability estimates across the group. Here we help fill this knowledge gap, gathering all available heritability estimates for ants, bees, and wasps, evaluating which factors affect these estimates and assessing the reported genetic correlations between traits. Using a model selection approach to analyze a dataset of more than 800 heritability estimates, we found that heritability is influenced by trait type, with morphological traits exhibiting the highest heritability estimates, and defense and metabolism-related traits showing the lowest estimates. Study system, sociality degree, experimental design, estimation type (narrow or broad-sense heritability), and sample size were not found to affect heritability estimates. Results remained unaltered when correcting for phylogenetic inertia, and when analyzing social bees separately. Genetic correlations between honeybee traits revealed both positive coefficients, usually for traits in the same category, and negative coefficients, suggesting trade-offs among other traits. We discuss these findings and highlight the importance of maintaining genetic variance in fitness-related traits. Our study shows the importance of considering heritability estimates and genetic correlations when designing breeding and conservation programs. We hope this meta-analysis helps identify sustainable breeding approaches and conservation strategies that help safeguard the evolutionary potential of wild and managed bees.     

The effect of audience on intrasexual interaction in the male fiddler crab, <Emphasis Type="Italic">Uca maracoani</Emphasis> (Latreille 1802–1803, Decapoda,Ocypodidae)

Animal communication occurring in wide networks can involve signals sent to several receivers. The animals composing the audience may affect how individuals display during an interaction and may change the message that is sent. In this study, we investigated whether the presence of a conspecific affected the intensity of agonistic interaction between male fiddler crabs, Uca maracoani. Pairs of males of the same size were observed when in the presence of a male, a female or no crab as audience. We found that if there is a female audience, males became more aggressive and interacted the most. Also, the female audience leads to an increase in incidence of male foaming, possibly indicating predisposition for mating. If the audience was a male or if there was no audience, there was no significant difference in interaction. These results indicate that the presence of an audience affects the way male fiddler crabs interact and the type of displays they show. Therefore, the context seems to guide the fiddler crab behavior in terms of how they perform in order to send information about themselves to conspecifics.     

The first evidence of osteomyelitis in a sauropod dinosaur

Osteomyelitis is reported for the first time in a sauropod dinosaur. The material (MCS‐PV 183) comes from the Anacleto Formation (Campanian, Late Cretaceous), at the Cinco Saltos locality, Río Negro Province, Argentina. The specimen consists of 16 mid and mid‐distal caudal vertebrae of a titanosaur sauropod. Evidence of bacterial infection is preserved in all of these vertebrae. The main anomalies are as follows: irregular ‘microbubbly’ texture of bone surfaces produced by periosteal reactive bone, abscesses on the rims of the anterior articular surfaces of two centra, numerous pits on centra anterior articulation surfaces, erosions on the anterior articulation of the vertebral centra, a vertical groove in posterior articular face of all the centra and disruption of the prezygapophysis and postzygapophysis (mainly the articular face) from the vertebra 19 and beyond. The last anomaly is increasingly pronounced in more distal elements of the series. Thin sections reveal that the anomalous cortical tissue is composed of avascular and highly fibrous bone matrix. The fibres of the bone matrix are organized into thick bundles oriented in different directions. Both morphological and histological abnormalities in the MCS‐PV 183 specimen are pathognomonic for osteomyelitis.     

Alpha-adrenoceptor-mediated coronary vasoconstriction is augmented during exercise in experimental diabetes mellitus.

This study tested whether alpha-adrenoceptor-mediated coronary vasoconstriction is augmented during exercise in diabetes mellitus. Experiments were conducted in dogs instrumented with catheters in the aorta and coronary sinus and with a flow transducer around the circumflex coronary artery. Diabetes was induced with alloxan monohydrate (n = 8, 40 mg/kg i.v.). Arterial plasma glucose concentration increased from 4.7 +/- 0.2 mM in nondiabetic, control dogs (n = 8) to 21.4 +/- 1.9 mM 1 wk after alloxan injection. Coronary blood flow, myocardial oxygen consumption (MVo(2)), aortic pressure, and heart rate were measured at rest and during graded treadmill exercise before and after infusion of the alpha-adrenoceptor antagonist phentolamine (1 mg/kg iv). In untreated diabetic dogs, exercise increased MVo(2) 2.7-fold, coronary blood flow 2.2-fold, and heart rate 2.3-fold. Coronary venous Po(2) fell as MVo(2) increased during exercise. After alpha-adrenoceptor blockade, exercise increased MVo(2) 3.1-fold, coronary blood flow 2.7-fold, and heart rate 2.1-fold. Relative to untreated diabetic dogs, alpha-adrenoceptor blockade significantly decreased the slope of the relationship between coronary venous Po(2) and MVo(2). The difference between the untreated and phentolamine-treated slopes was greater in the diabetic dogs than in the nondiabetic dogs. In addition, the decrease in coronary blood flow to intracoronary norepinephrine infusion was significantly augmented in anesthetized, open-chest, beta-adrenoceptor-blocked diabetic dogs compared with the nondiabetic dogs. These findings demonstrate that alpha-adrenoceptor-mediated coronary vasoconstriction is augmented in alloxan-induced diabetic dogs during physiological increases in MVo(2).