Thinking outside the patch: a multi-species comparison of conceptual models from real-world landscapes

Context

When modeling a species’ distribution, landscapes can alternatively be conceptualized following patch- or gradient-based approaches. However, choosing the most suitable conceptualization is difficult and methods for empirical validation are still lacking.

Objectives

To address the conditions under which a given conceptual model is more suitable, taking into account landscape context and species trait dependency effects. Patch- and gradient-based conceptualizations were built based on two structurally different landscapes: variegated and mosaic. We hypothesize that: (H1) gradient-based models better describe variegated landscapes while patch-based models perform better in mosaic landscapes; and (H2) gradient-based models will fit generalist species better while patch-based models will suit specialists better.

Methods

We modeled the distribution of eleven bird species in each landscape using each conceptualization. We determined the suitability of each conceptual model to fit statistical models by looking for cross-species responses and deviations from best models.

Results

We found no clear support for our hypotheses. Although patch-based models performed better in mosaic landscapes (H1), they also provided useful conceptualizations in variegated landscapes. However, when patches showed high heterogeneity, gradient-based approaches better fit specialist species (H2).

Conclusions

The suitability of a given conceptual model depends on the interaction between species habitat specialization, and the intrinsic spatial heterogeneity of the landscape and the ability of each conceptualization to capture it. Gradient-based models provide better information on resource allocation, while patch-based models offer a simplified perspective on landscape attributes. Future research should consider the nature of both species and landscapes in order to avoid bias from inadequate landscape conceptualizations.

     

Mineral salt intake effects on faecal-N concentration and the volume and composition of beef cattle urine

The effect of mineral salts on water ingestion and urine volume in cattle has been extensively studied. However, recently, this effect has been investigated as a potential mitigator of environmental aspects related to the nitrogen (N) cycle, such as nitrate (NO₃^?) lixiviation, ammonia (NH₃) volatilisation, and nitrous oxide (N₂O) emissions. The effect of mineral salts, particularly sodium chloride (NaCl), on urine-N concentration, urine volume, the proportion of N compounds in the urine, and faecal-N concentration has not yet been explored in field conditions with respect to environmental aspects of beef cattle production. The present study investigated the effect of dietary mineral salt rates on these parameters. A Latin square (5?×?5) experimental design was utilised with five concentrations of mineral salts in the diet: 0.0, 2.0, 4.0, 6.0, and 8.0 g based on dry matter (DM) ingestion (g/kg DM). The nitrogen concentration in the urine and urine volume increased linearly. The total N excreted (g/day) via urine did not vary with increasing mineral salt concentrations. When evaluated, the N compounds of urine (urea-N, allantoin-N, and hippuric acid-N) also reacted to the increased mineral salt concentrations, while creatinine-N did not. Urea-N, allantoin-N, and hippuric acid-N linearly increased their proportions in total N-urine. The N concentration in faeces was not affected by mineral salt concentrations. The urine volume, concentration of N, and proportion of N compounds in the urine affected N₂O emissions and NH₃ volatilisation. Therefore, mineral salt utilisation may be an option for mitigating N pollution from beef cattle, especially for grasslands in tropical countries.

     

Prevalence of lameness and hoof lesions in all year-round grazing cattle in Brazil

Lameness is a growing concern to the dairy industry worldwide. However, little is known about lameness and its causes in grazing cattle, especially in tropical climates. This study aimed to assess the prevalence of hoof lesions and lameness in dairy herds of all year-round grazing cattle under tropical condition, and to identify the main lesions associated with lameness. We visited 48 farms located in the Minas Gerais state, Brazil, equally divided into four groups based on daily milk production. All lactating cows in the visited farms were locomotion scored, and a representative sample was randomly chosen for hoof inspection. Among the 2267 lactating cows evaluated, 16% were scored as lame and 7% as severely lame. Nearly all cows presented at least one type of hoof lesion, of which heel horn erosion (90%), white line fissure (50%), and digital dermatitis (33%) were the most prevalent. Heel horn erosion was present in all farms and digital dermatitis was present in 96% of the farms. Sole ulcer was observed in a single animal. Additionally, digital dermatitis and white line fissure were correlated to a 2.5 times increase in the odds of a poor mobility score. Collectively, our results demonstrate that digital dermatitis and white line fissure are the main concern and the biggest cause of lameness in grazing cattle under tropical conditions.     

Low occurrence of pathogenic Yersinia enterocolitica in pig tonsils at slaughter in Southern Brazil

Tropical Animal Health and Production - Yersinia enterocolitica is a foodborne pathogen and pigs are the main reservoir of it in their tonsils. As Brazil is a large producer and exporter of pork...     

Restoration of dead wood in Basque stream channels: effects on brown trout population

Abstract – Streams in the Aiako Harria Natural Park (Basque Country, Spain) have excellent water quality, but are physically impoverished after centuries of snagging. In an attempt to restore channel complexity and ecosystem functioning, especially in‐channel retention of sediments and organic matter, large woody debris (LWD) was introduced into four mountain streams (channel width 3–13 m) following a before/after, control/impact (BACI) design. Logs were introduced by means of hand‐held machinery and located uncabled, mimicking the natural amount and disposition of LWD in streams. Floods disrupted most of the structures at the large stream, but caused little damage to those in the small ones. Only minnow and brown trout inhabit in the area. Before wood addition, trout densities were fairly high in the small streams, low in the large one, where recruitment seemed very poor. In the small tributaries, trout populations showed a strong imbalance towards young fish, adults being only found in the spawning season. Wood addition produced some interesting trends in trout, although statistical significance was low as a result of large environmental variability. Fish densities showed small changes, but biomass increased, especially in the spawning season. Also, there was a trend towards more aged 2⁺ or larger, thus suggesting wood addition improved adult habitat. Although restoring LWD is extremely unusual in Spain, the changes in physical habitat and the trends in fish populations detected in the present project suggest it is worth making more experiments, at least in safe settings where there is no risk of flooding or damaging properties.     

Early weaning of cuttlefish (Sepia officinalis,L.) with frozen grass shrimp (Palaemonetes varians) from the first day after hatching

The suitability of early weaning cuttlefish using frozen grass shrimp, and its effects on growth and mortality was determined in a 50‐day experiment. Three food groups were used. One group (C) was fed with live prey until 25th DAH and weaned with frozen prey until the end of the experiment. In the other two groups, weaning started at the fifth DAH (W5) and first DAH (W1), also with frozen diet. Significant differences were found between C and the remaining treatments (P < 0.05) for mean wet weight (MWW), instantaneous growth rate (IGR), biomass (B) and mortality at the 25th and the 50th DAH. Despite the lower growth (~1/3 of the achieved with live food) and higher mortality (3% obtained by C versus 23% in the W1 and W5 groups), C cuttlefish presented a similar weight gain tendency to W1 and W5 groups after weaning. This is the first record of early acceptance (at the first DAH) of frozen food by cuttlefish hatchlings. These differences could be related with digestive enzymes of cuttlefish and prey, changes in nutritional composition and amount of captured prey, etc. Future research should also address the effects of this early weaning on cuttlefish life cycle.     

Influence of steam heating on the properties of pine (<Emphasis Type="Italic">Pinus pinaster</Emphasis>) and eucalypt (<Emphasis Type="Italic">Eucalyptus globulus</Emphasis>) wood

Heat treatment of Pinus pinaster and Eucalyptus globulus woods, two important species in Portugal, was performed in the absence of air by steaming, inside an autoclave, for 2–12 h at 190–210°C. Mass losses increased with treatment time and temperature reaching 7.3% for pine and 14.5% for eucalypt wood. The wood behaviour with moisture was improved. The equilibrium moisture content decreased by 46% for pine and 61% for eucalypt, the dimensional stability increased (maximum anti-shrinking efficiency in the radial direction of 57 and 90% for pine and eucalypt, respectively) and the surface wettability was lowered. In relation to mechanical properties, the modulus of elasticity was little affected (maximum decrease of 5% for pine and 15% for eucalypt) but the bending strength was reduced (by 40% at 8% mass loss for pine and 50% at 9% mass loss for eucalypt wood). The variation of properties was related to treatment intensity and mass loss but significant improvements could already be obtained for a 3–4% mass loss without impairing the mechanical resistance. The response of eucalypt was higher than that of pinewood. Heat treatment of eucalypt wood shows an interesting potential to improve the wood quality for solid timber products.     

The Neurospora checkpoint kinase 2: a regulatory link between the circadian and cell cycles

The clock gene period-4 (prd-4) in Neurospora was identified by a single allele displaying shortened circadian period and altered temperature compensation. Positional cloning followed by functional tests show that PRD-4 is an ortholog of mammalian checkpoint kinase 2 (Chk2). Expression of prd-4 is regulated by the circadian clock and, reciprocally, PRD-4 physically interacts with the clock component FRQ, promoting its phosphorylation. DNA-damaging agents can reset the clock in a manner that depends on time of day, and this resetting is dependent on PRD-4. Thus, prd-4, the Neurospora Chk2, identifies a molecular link that feeds back conditionally from circadian output to input and the cell cycle.