Roe deer may markedly alter forest nitrogen and phosphorus budgets across Europe

Most forests in Europe are patchily distributed within the agricultural landscape. Therefore, forest biogeochemistry in Europe cannot be understood without considering the connectivity of nutrient cycles between forest patches and fertilized cropland. In this paper, we quantified the role of roe deer, the most widespread wild ungulate in Europe, as a vector of nitrogen and phosphorus from fertilized fields to forest patches, in a typical agricultural landscape of southwestern Europe. We derived a model of nutrient transfer from a data set on deer density, landscape‐use by individual deer, and nutrient content in feces. The model shows that the magnitude of nutrient transfer is highly sensitive to the proportion of forest patches within the landscape, and to the way deer use the landscape to feed and defecate. Hence, the magnitude of nutrient transfer varies substantially across the landscape. Locally, deer may significantly fertilize the forest, transferring the equivalent of almost 20% of the atmospheric deposition of nitrogen, and the equivalent of 0.13% of the total stock of phosphorus from cropland to forest patches each year. These inputs may markedly influence the biogeochemistry of forests in the long run, and the nitrogen to phosphorus ratio available to trees and forest plants. These results highlight the significant, but, heterogeneous, role of wild ungulates in forest biogeochemistry across Europe.     

Landscape fragmentation generates spatial variation of diet composition and quality in a generalist herbivore

Forest fragmentation may benefit generalist herbivores by increasing access to various substitutable food resources, with potential consequences for their population dynamics. We studied a European roe deer (Capreolus capreolus) population living in an agricultural mosaic of forest, woodlots, meadows and cultivated crops. We tested whether diet composition and quality varied spatially across the landscape using botanical analyses of rumen contents and chemical analyses of the plants consumed in relation to landscape metrics. In summer and non-mast winters, roe deer ate more cultivated seeds and less native forest browse with increasing availability of crops in the local landscape. This spatial variation resulted in contrasting diet quality, with more cell content and lower lignin and hemicellulose content (high quality) for individuals living in more open habitats. The pattern was less marked in the other seasons when diet composition, but not diet quality, was only weakly related to landscape structure. In mast autumns and winters, the consumption of acorns across the entire landscape resulted in a low level of differentiation in diet composition and quality. Our results reflect the ability of generalist species, such as roe deer, to adapt to the fragmentation of their forest habitat by exhibiting a plastic feeding behavior, enabling them to use supplementary resources available in the agricultural matrix. This flexibility confers nutritional advantages to individuals with access to cultivated fields when their native food resources are depleted or decline in quality (e.g. during non-mast years) and may explain local heterogeneities in individual phenotypic quality.     

Macroinvertebrate community loss as a result of headwater stream acidification in the Vosges Mountains (N-E France)

The relationships between water chemistry and aquatic macroinvertebrate communities of 41 headwater streams were studied in the Vosges Mountains (N-E of France) in an attempt to assess the impact of acidification on macroinvertebrate diversity. The taxa richness of macroinvertebrates decreased drastically in headwater streams which were characterized by low pH, low calcium and high aluminum content. All taxonomic groups were affected, but Molluscans, Crustaceans and Ephemeroptera disappeared totally from strongly acidified streams. Simple indices based on taxa richness such as the coefficient of community loss may provide accurate tools to quickly assess the impact of acidification on macroinvertebrate communities. Despite the reduction of atmospheric SO₂ emissions, acidification of freshwater in the Vosges Mountains continues to affect streams which were believed in the past to constitute refuge biotopes for numerous species. Consequently, acidification represents a real threat for numerous invertebrates. This study arises the question of the evolution in the future of headwater stream ecosystems. Urgent decisions and interventions are required to preserve non-acidified streams and to restore impacted ecosystems while awaiting spontaneous recovery.     

Reversal of hypoxia-induced decrease in human cardiac response to isoproterenol infusion

A decrease in heart rate response to isoproterenol (IP) infusion has been previously described in humans exposed to acute (2-3 days) or chronic (21 days) exposure to altitude hypoxia (J. Appl. Physiol. 65: 1957-1961, 1988). To evaluate this cardiac response in subacute (8 days) hypoxia and to explore its reversal with restoration of normoxia, six subjects received an IP infusion under normoxia (condition N), after 8 days in altitude (4,350 m, condition H8), on the same day in altitude after inhalation of O2 restoring normoxic arterial O2 saturation (SaO2, condition HO), and 6-11 h (condition RN) and 4-5 mo (condition ND) after the return to sea level. Cardiac chronotropic response to IP, evaluated by the mean increase in heart rate from base value (delta HR, min-1), was lower in condition H8 [mean 30 +/- 13 (SD)] than in condition N (50 +/- 14, P less than 0.03); it was slightly higher in condition HO (38 +/- 14) or condition RN (42 +/- 15) than condition H8 but still significantly different from condition N (P less than 0.03), despite normal values of SaO2. delta HR in condition ND (55 +/- 10) returned to base N value. These findings confirm the hypothesis of a hypoxia-induced decrease in cardiac chronotropic function. Two possible mechanisms are suggested: an O2-dependent one, rapidly reversible with recent restoration of normoxia, and a more slowly reversible mechanism, probably a downregulation of the cardiac beta-receptors.     

The CRL2LRR-1 ubiquitin ligase regulates cell cycle progression during C. elegans development

The molecular mechanisms that regulate cell cycle progression in a developmental context are poorly understood. Here, we show that the leucine-rich repeat protein LRR-1 promotes cell cycle progression during C. elegans development, both in the germ line and in the early embryo. Our results indicate that LRR-1 acts as a nuclear substrate-recognition subunit of a Cullin 2-RING E3 ligase complex (CRL2(LRR-1)), which ensures DNA replication integrity. LRR-1 contains a typical BC/Cul-2 box and binds CRL2 components in vitro and in vivo in a BC/Cul-2 box-dependent manner. Loss of lrr-1 function causes cell cycle arrest in the mitotic region of the germ line, resulting in sterility due to the depletion of germ cells. Inactivation of the DNA replication checkpoint signaling components ATL-1 and CHK-1 suppresses this cell cycle arrest and, remarkably, restores lrr-1 mutant fertility. Likewise, in the early embryo, loss of lrr-1 function induces CHK-1 phosphorylation and a severe cell cycle delay in P lineage division, causing embryonic lethality. Checkpoint activation is not constitutive in lrr-1 mutants but is induced by DNA damage, which may arise due to re-replication of some regions of the genome as evidenced by the accumulation of single-stranded DNA-replication protein A (ssDNA-RPA-1) nuclear foci and the increase in germ cell ploidy in lrr-1 and lrr-1; atl-1 double mutants, respectively. Collectively, these observations highlight a crucial function of the CRL2(LRR-1) complex in genome stability via maintenance of DNA replication integrity during C. elegans development.     

Mouse Testis Development and Function Are Differently Regulated by Follicle-Stimulating Hormone Receptors Signaling During Fetal and Prepubertal Life

It is currently admitted that Follicle-Stimulating Hormone (FSH) is physiologically involved in the development and function of fetal/neonatal Sertoli cells in the rat but not the mouse. However, FSH is produced by both species from late fetal life onwards. We thus reinvestigated the role of FSH in mouse testis development at day 0 (birth) 6, 8 and 10 post-partum (dpp) by using mice that lack functional FSH receptors (FSH-R^−/−). At birth, the number and proliferative index of Sertoli cells were significantly lower in FSH-R^−/− mice than in wild type neonates. Claudin 11 mRNA expression also was significantly reduced in FSH-R^−/− testes at 0 and 8 dpp, whereas the mRNA levels of other Sertoli cell markers (Transferrin and Desert hedgehog) were comparable in FSH-R^−/− and wild type testes. Conversely, AMH mRNA and protein levels were higher at birth, comparable at 6 dpp and then significantly lower in FSH-R^−/− testes at 8–10 dpp in FSH-R^−/− mice than in controls. Although the plasma concentration of LH and the number of Leydig cells were similar in FSH-R^−/− and control (wild type), testosterone concentration and P450c17 mRNA expression were significantly increased in FSH-R^−/− testes at birth. Conversely, at 10 dpp when adult Leydig cells appear, expression of the steroidogenic genes P450scc, P450c17 and StAR was lower in FSH-R^−/− testes than in controls. In conclusion, our results show that 1) like in the rat, signaling via FSH-R controls Sertoli cell development and function during late fetal life in the mouse as well; 2) paracrine factors produced by Sertoli cells are involved in the FSH-R-dependent regulation of the functions of fetal Leydig cells in late fetal life; and 3) the role of FSH-R signaling changes during the prepubertal period.     

Effects of 5-day hypoxia on cardiac adrenergic neurotransmission in rats

Chronic hypoxiainduces an overall sympathetic hyperactivation associated with amyocardial -receptor desensitization. The mechanismsinvolved in this desensitization were evaluated in 32 male Wistar ratskept in a hypobaric pressure chamber(PO₂ = 40 Torr, atmospheric pressure = 450 Torr) for 5 days. In hypoxic compared with normoxic conditions,plasma norepinephrine (NE) levels were higher (2.1 ± 0.7 vs. 0.6 ± 0.2 ng/ml) with no difference in the plasma epinephrine levels(2.2 ± 0.7 vs. 1.8 ± 0.3 ng/ml). In hypoxia neuronal NE uptakemeasured by [³H]NE wasdecreased by 32% in the right ventricle (RV) and by 35% in the leftventricle (LV), and[³H]mazindol in vitrobinding showed a decrease in uptake-1 carrier protein density by 38%in the RV and by 41% in the LV. In vitro binding assays with[³H]CGP-12177 indicate-adrenoceptor density reduced by 40% in the RV and by 32% in theLV, and this was due to reduced₁-subtype fraction (competitionbinding experiments with practolol). Hypoxia reduced the production ofcAMP induced by isoproterenol (36% decrease in the RV and 41%decrease in the LV), 5'-guanylylimododiphosphate (40% decreasein the RV and 42% decrease in the LV), and forskolin (39% decrease inthe RV and 41% decrease in the LV) but did not alter the effect ofMnCl₂ and NaF. Quantitation ofinhibitory G-protein -subunit by immunochemical analysis showed a46% increase in the cardiac-specific isoformG_i2 inhypoxic hearts. The present data demonstrate that in rats 5-day hypoxialeads to changes in pre- and postsynaptic myocardial adrenergicfunction. The myocardial desensitization associated with both areduction in externalized ₁-adrenoceptor and an increasein inhibitory G-protein subunit may be caused by increased synaptic NElevels due to impaired uptake-1 system.

     

Pedigree‐free quantitative genetic approach provides evidence for heritability of movement tactics in wild roe deer

Assessing the evolutionary potential of animal populations in the wild is crucial to understanding how they may respond to selection mediated by rapid environmental change (e.g. habitat loss and fragmentation). A growing number of studies have investigated the adaptive role of behaviour, but assessments of its genetic basis in a natural setting remain scarce. We combined intensive biologging technology with genome‐wide data and a pedigree‐free quantitative genetic approach to quantify repeatability, heritability and evolvability for a suite of behaviours related to the risk avoidance‐resource acquisition trade‐off in a wild roe deer (Capreolus capreolus) population inhabiting a heterogeneous, human‐dominated landscape. These traits, linked to the stress response, movement and space‐use behaviour, were all moderately to highly repeatable. Furthermore, the repeatable among‐individual component of variation in these traits was partly due to additive genetic variance, with heritability estimates ranging from 0.21 ± 0.08 to 0.70 ± 0.11 and evolvability ranging from 1.1% to 4.3%. Changes in the trait mean can therefore occur under hypothetical directional selection over just a few generations. To the best of our knowledge, this is the first empirical demonstration of additive genetic variation in space‐use behaviour in a free‐ranging population based on genomic relatedness data. We conclude that wild animal populations may have the potential to adjust their spatial behaviour to human‐driven environmental modifications through microevolutionary change.