Insect-mediated apparent competition between mammals in a boreal food web.

While the important role of animal-mediated interactions in the top-down restructuring of plant communities is well documented, less is known of their ensuing repercussions at higher trophic levels. We demonstrate how typically decoupled ecological interactions may become intertwined such that the impact of an insect pest on forest structure and composition alters predator-prey interactions among large mammals. Specifically, we show how irruptions in a common, cyclic insect pest of the boreal forest, the spruce budworm (Choristoneura fumiferana), modulated an indirect trophic interaction by initiating a flush in deciduous vegetation that benefited moose (Alces alces), in turn strengthening apparent competition between moose and threatened boreal caribou (Rangifer tarandus caribou) via wolf (Canis lupus) predation. Critically, predation on caribou postoutbreak was exacerbated by human activity (salvage logging). We believe our observations of significant, large-scale reverberating consumer-producer-consumer interactions are likely to be common in nature.

Triple Thorpe-Ingold Effect in the Synthesis of 18-Membered C3 Symmetric Lactams Stacking as Endless Supramolecular Tubes.

Three C3 symmetric macrolactams were very efficiently cyclized from their linear precursors. Adequately located substituents are responsible for the enhancement of reactivity that is not observed in the unsubstituted parent. DFT calculations show that the properly folded cyclization precursor, the reactive conformer, is more populated than other conformers, leading to a decrease of free energy of activation. The crystal structure of the ring substituted with three very bulky esters indicates that tubular stacking is preserved.

Strong Host-Guest Dependence on the Emissive Properties of MOF-5 and [Zn2(BTTB)(DMF)2•(H2O)3]n.

3D-[Zn4O(1,4-BDC)3•x(solvent)]n (MOF-5; BDC = 1,4-benzodicarboxylate) and 3D-[Zn2(BTTB)(DMF)2•(H2O)3]n (MOF-D; BTTB = 4,4',4″,4‴-benzene-1,2,4,5-tetrayltetrabenzoate) have been investigated by means of steady-state UV-visible and fluorescence and time-resolved emission spectroscopy, as a function of solvent and power of the excitation irradiation. The low-temperature X-ray structures (173 K) were permitted to locate solvent molecules (here H2O) in the lattice. They were found distributed in the middle in the voids with no evidence of specific interactions (H-bond, coulombic, and dipole-dipole) with the framework. The fluorescence decays of the ligands (ππ* excited state), τF, for the host-guest composites MOF-5@solvent and MOF-D@solvent (solvent = air, MeCN, EtCN, MeOH, EtOH, and DMF) were found bi-exponential (short τF1 (ps), and long τF2 (ns)) with one important feature: upon cooling from 298 to 77 K, MOF-5's τF1 decreases and τF2 increases, while the opposite trend is generally observed in MOF-D. The low values for τF1 (ps) in MOF-5 are associated with the augmented probability of solvent-ligand collisions leading to nonradiative deactivation, which upon cooling to 77 K increases further as the scaffolding contracts. The augmentation in τF2 is readily associated with the increased rigidity of the ligands that are not submitted to this effect (at the surface of the MOF and as pendent groups). For the low emitter MOF-D, the reversed situation is noted but not as clearly due to the uncertainties in the data. Upon increasing the excitation flux, the fluorescence intensity increases linearly with the laser power indicating the absence of singlet-singlet annihilation, inferring the absence of efficient exciton migration. This observation is explained by the small absorptivity coefficients, which leads to a small J spectral overlap between absorption and fluorescence according to the Forster and Dexter theories, and consequently, a small rate for energy migration. This conclusion drastically changes the perception of the photocatalytic mechanism of MOF-5 and other MOFs exhibiting similar absorption features (i.e., no antenna effect).

Truxene-to-Fluorenone Energy Transfer in a Robust Mesoporous Zn-MOF.

A new metal-organic framework (MOF; [Zn4O(hett)4/3(fluo)1/2(bdc)1/2]n; TFT-MOF) constructed on chromophoric ligands 5,5',10,10',15,15'-hexaethyltruxene-2,7,12-triacetate (hett), 9-fluorenone-2,7-dicarboxylate (fluo), terephthalate (bdc), and the Zn4O node has been prepared and identified by powder X-ray diffraction. This luminescent MOF exhibits large mesoporous pores of 2.7 nm based on computer modeling using density functional theory (DFT) calculations. The steady-state and time-resolved fluorescence spectra and photophysical parameters of TFT-MOF have been investigated and compared with those of the free ligands and their basic chromophores. All in all, TFT-MOF exhibits particularly efficient singlet-singlet energy-transfer processes described as 1(hett)* → (fluo) and 1(bdc)* → (fluo), leading to fluorescence arising for the fluo lumophore operating only through Förster resonance energy transfer (FRET) with an efficiency of transfer of up to >95%. This experimental conclusion was corroborated by DFT and time-dependent DFT (TDDFT). For the 1(hett)* → (fluo) process, the approximated overall rate constant of energy transfer was evaluated to be at most 2.04 × 1010 s-1 (using a Stern-Volmer approach of solution data and the relationship between distance and concentration). This process was analyzed using the Förster theory, where two intrapore energy transfer paths of center-to-center distances of 13 and 25 Å have been identified. TFT-MOF photosensitizes the formation of singlet oxygen (1O2 (1Σg)) as detected by its phosphorescence signal at 1275 nm.

Statistical Analysis of Copper(I) Iodide and Bis(Diphenylphosphino)alkane-Based Complexes and Coordination Polymers.

The prediction of the metal cluster within a coordination polymer or complex, as well as the dimensionality of the resulting polymer or complex (i.e., 0D, 1D, 2D, or 3D), is often challenging. This is the case for Ph2P(CH2)mPPh2 ligands (1 ≤ m ≤ 8) and CuX salts, particularly for X = I. This work endeavors a systematic statistical analysis combining studies in the literature and new data, mapping the nature of the resulting CuI aggregates with eight different diphoshphines in 2:1, 3:2, 1:1, 2:3, and 1:2 CuI:Ph2P(CH2)mPPh2 molar ratios as a function of m, which lead to either pure products or mixtures. Several trends are made relating stoichiometry and chain length to the CuI cluster formed (i.e., globular vs. quasi-planar). Four new X-ray structures were determined: [Cu3I2(L1)3]I, Cu3I3(L2)2, Cu2I2(L6)2, and Cu4I4(L8)2, where m is, respectively, 1, 2, 6, and 8, in which the CuxIy central aggregates adopt triangular bipyramid, diamond, rhomboid, and cubane shaped motifs, respectively. Photophysical measurements assisted the establishment of trends considering the paucity of the crystallographic structures. During this study, it was also found that the 0D-complex Cu2I2(Ph2P(CH2)5PPh2)2 exhibits thermally activated delayed fluorescence.

Chain Length Effect on the Structural and Emission Properties of the CuI/Bis((4-methoxyphenyl)thio)alkane Coordination Polymers.

A systematic chain length variation of the ligand para-MeOC6H4S(CH2)mSC6H4OMe (1 ≤ m ≤ 8) was performed to study its effect on the structures and photophysical properties of the coordination polymers (CP) when reacted with CuI. Indeed, direct correlations are noted between these features and m. When m is an odd number, the secondary building unit is systematically the common closed-cubane Cu4I4 cluster, rendering the material strongly luminescent (i.e., emission quantum yield, Φe > 20%), and the CP is one-dimensional (1D). However, when m is 2, 4, and 6, the SBUs exhibit rare polymeric motifs of (Cu2I2)n: staircase ribbon, fused poly(rhombic pseudo-dodecahedron), and accordion ribbon, respectively, and the emission intensities are either very weak (Φe < 0.001%) or of medium intensity (Φe ∼ 10% when m = 6). When m = 8 (i.e. the most flexible chain), the SBU is a closed-cubane Cu4I4 and the emission intensity is medium (Φe ∼ 10%). A special case was observed for m = 3, where a co-crystallization of the molecular cluster Cu4I4(NCCH3)4 is observed in the lattice, which turns out to be quite important for the stability of the network.

Crop raiders in an ecological trap: optimal foraging individual-based modeling quantifies the effect of alternate crops.

Crop raiding is an increasing source of human-wildlife conflict that antagonizes humans and can lead to heightened killing of wildlife. Attraction to crops can trigger ecological traps, where animals prefer areas of their range that confer relatively low fitness. Food can be used to draw animals away from problematic areas, but an alternative considered less often is to replace high-quality food with poorer alternatives. In any case, managers often have no means of anticipating by how much such interventions should impact animal use of space. Optimal foraging theory predicts that foragers optimizing their diet should choose food items according to their relative profitability (i.e., digestible energy/ handling time), a theoretical prediction that can orient management actions. Accordingly, we developed an individual-based model (IBM) simulating movement through empirical rules under an optimal foraging framework. Our objective was to quantify the effect size of cultivating alternate crops to reduce crop raiding and the associated human-induced mortality driving an ecological trap for an energy maximizer, plains bison (Bison bison bison). Results showed that almost tripling the area of cultivation of crops of lower profitability (from 24.3% of the bison range outside the protected area in one management scenario to 70.3% in another) only led to a 25% additional decrease in the intensity of crop raiding (from a decrease of 40% in the first scenario to a decrease of 65% in the second). This suggests that localized interventions in the landscape are likely to have a stronger impact in mitigating crop raiding than broad actions ignoring spatial patterns in food distribution. However, we obtained no significant reduction in the number of simulated bison being harvested in the first scenario, and only a small reduction in the second, when the intervention was spatially broad. Our individual-based approach to animal movement informed by optimal foraging demonstrates that linking landscape configuration to mortality rates can help managers anticipate the effectiveness of manipulating food to keep animals away from problematic zones. Yet disarming ecological traps driven by human hunting appears to be a much more challenging undertaking.

A Platinum(II) Organometallic Building Block for the Design of Emissive Copper(I) and Silver(I) Coordination Polymers.

The tritopic organometallic ligand trans-MeSC6H4C≡CPt(PMe3)2(C≡N) (L1) was prepared from cis-PtCl2(PMe3)2 and p-ethynyl(methyl thioether)benzene. Its versatility was shown with the formation of [CuX(L1)]n coordination polymers (CPs) with CuX salts in MeCN (X = I (CP1), CN (CP2), SCN (CP3)). These CPs were characterized by X-ray crystallography, thermal gravimetric analysis (TGA), and IR and Raman spectroscopy. CP1 consists of a 1D head-to-tail chain formed by tricoordinated -C≡N-CuI(η2-C≡C)- linkages, whereas CP2 is built upon a central (CuCN)n zigzag chain bearing dangling L1s held by -C≡N-Cu bonds. Finally, CP3 exhibits 2D sheets secured by Cu-N≡C-/-(Me)S-Cu bondings and transversal Cu-S-C≡N-Cu bridges. Concurrently, the CPs formed with AgX (X = NO3- (CP4 and CP5), CF3CO2- (CP6) PF6- (CP7)) exhibits 2D sheets with guest molecules (anion, solvents) inside the tight pores or between layers. These new materials are emissive: L1 (λ0-0 ∼465 nm), CP1-CP7 (500 < λmax < 620 nm). Their photophysical properties (absorption and emission spectra, emission lifetimes (∼0.2 < τe < 120 µs), and quantum yields in the solid state at 77 and 298 K) were analyzed. The various natures of the emissive excited states were addressed by density functional theory (DFT) and time-dependent DFT (TDDFT) computations. For CP1, this state is a triplet halide or pseudohalide to ligand charge transfer 3XLCT (CT = charge transfer; X = I; L = L1) and for CP2, it is 3XLCT (X = CN; L = L1). However, for CP3, it is 3XLCT (X = SCN; L = L1). For CP4, the T1 state is described as a [MeSC6H4(η2-C≡C)-Ag(NO3)]2 → [Pt]/C≡CC6H4SMe CT.

From Short-Bite Ligand Assembled Ribbons to Nanosized Networks in Cu(I) Coordination Polymers Built Upon Bis(benzylthio)alkanes (BzS(CH2)nSBz; n = 1-9).

With the objective to establish a correlation between the spacer distance and halide dependence on the structural features of coordination polymers (CPs) assembled by the reaction between CuX salts (X = Cl, Br, I) and dithioether ligands BzS(CH2)nSBz (n = 1-9; Bz = benzyl), a series of 26 compounds have been prepared and structurally investigated. A particular attention has been devoted to the design of networks with extremely long and flexible methylene spacer units between the SBz donor sites. Under identical conditions, CuI and CuBr react with BzSCH2Bz (L1) affording respectively the one-dimensional (1D) CPs {Cu(µ2-I)2Cu}(µ-L1)2]n (CP1) and {Cu(µ2-Br)2Cu}(µ-L1)2] (CP2), which incorporate Cu(µ2-X)2Cu rhomboids as secondary building units (SBUs). The hitherto unknown architecture of two-dimensional (2D) layers obtained with CuCl (CP3) differs from that of CP1 and CP2, which bear inorganic -Cl-Cu-Cl-Cu-Cl- chains interconnected through bridging L1 ligands, thus forming a 2D architecture. The crystallographic characterization of a 1D CP obtained by reacting CuI with 1,3-bis(benzylthio)propane (L2) reveals that [{Cu(µ2-I)2Cu}(µ-L2)2]n (CP4) contains conventional Cu2I2 rhomboids as SBUs. In contrast, unusual isostructural CPs [{Cu(µ2-X)}(µ2-L2)]n (CP5) and (CP6) are obtained with CuX when X = Br and Cl, respectively, in which the isolated Cu atoms are bridged by a single µ2-Br or µ2-Cl ion giving rise to infinite [Cu(µ2-X)Cu]n ribbons. The crystal structure of the strongly luminescent three-dimensional (3D) polymer [{Cu4(µ3-I)3(µ4-I)(µ-L3)1.5]n (CP7) issued from reacting 2 equiv of CuI with BzS(CH2)4SBz (L3) has been redetermined. CP7 features unusual [(Cu4I3)(µ4-I)]n arrays securing the 3D connectivity. In contrast, mixing CuI with an excess of L3 provides the nonemissive material [{Cu(µ2-I)2Cu}(µ-L3)2]n (CP8). Treatment of CuBr and CuCl with L3 leads to [{Cu(µ2-Br)2Cu}(µ-L3)2]n (CP9) and the 0D complex [{Cu(µ2-Cl)2Cu}(µ-L3)2] (D1), respectively. The crystallographic particularity for CP9 is the coexistence of two topological isomers within the unit cell. The first one, CP9-1D, consists of simple 1D ribbons running along the a axis of the unit cell. The second topological isomer, CP9-2D, also consists of [Cu(µ2-Br)2Cu] SBUs, but these are interconnected in a 2D manner forming 2D sheets placed perpendicular to the 1D ribbons. Four 2D CPs, namely, [{Cu4(µ3-I)4}(µ-L4)2]n (CP10), [{Cu(µ2-I)2Cu}(µ-L4)2]n (CP11), [{Cu(µ2-Br)2Cu}(µ-L4)2]n (CP12), and [{Cu(µ2-Cl)2Cu}(µ-L4)2]n (CP13), stem from the self-assembly process of CuX with BzS(CH2)6SBz (L4). A similar series of 2D materials comprising [{Cu4(µ3-I)4}(µ-L5)2]n (CP14), [{Cu(µ2-I)2Cu}(µ-L5)2]n (CP15), [{Cu(µ2-Br)2Cu}(µ-L5)2]n (CP16), and [{Cu(µ2-Cl)2Cu}(µ-L5)2]n (CP17) result from the coordination of BzS(CH2)7SBz (L5) on CuX. Ligation of CuX with the long-chain ligand BzS(CH2)8SBz (L6) allows for the X-ray characterization of the luminescent 2D [{Cu4(µ3-I)4}(µ-L6)2]n (CP18) and the isostructural 1D series [{Cu(µ2-X)2Cu}(µ-L6)2]n CP19 (X = I), CP20 (X = Br) and CP21(X = Cl). Noteworthy, BzS(CH2)9SBz (L7) bearing a very flexible nine-atom chain generated the crystalline materials 2D [{Cu4(µ3-I)4}(µ-L7)2]n (CP22) and the isostructural 1D series [{Cu(µ2-X)2Cu}(µ-L6)2]n CP23 (X = I), CP24 (X = Br), and CP25 (X = Cl), featuring nanometric separations between the cubane- or rhomboid-SBUs. This comparative study reveals that the outcome of the reaction of CuX with the shorter ligands BzS(CH2)nSBz (n = 1-4) is not predictable. However, with more flexible spacer chains BzS(CH2)nSBz (n = 6-9), a clear structural pattern can be established. Using a 1:1 CuX-to-ligand ratio, [{Cu(µ2-X)2Cu}(µ-L4-7)2] CPs are always formed, irrespectively of L4-L7. Employing a 2:1 CuX-to-ligand ratio, only CuI is able to form networks incorporating Cu4(µ3-I)4 clusters as SBUs. All attempts to construct polynuclear cluster using CuBr and CuCl failed. The materials have been furthermore analyzed by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis, and the photophysical properties of the emissive materials have been studied.

Space Use and Leadership Modify Dilution Effects on Optimal Vigilance under Food-Safety Trade-Offs.

Dilution of predation risk within groups allows individuals to be less vigilant and forage more while still facing lower risk than if they were alone. How group size influences vigilance when individuals can also adjust their space use and whether this relationship differs among individuals contributing differently to space use decisions remain unknown. We present a model-based study of how dilution affects the optimal antipredator behavior of group members in groups where all individuals determine their vigilance level while group leaders also determine space use. We showed that optimal vigilance did not always decrease with group size, as it was sometimes favorable for individuals in larger groups to use riskier patches while remaining vigilant. Followers were also generally less vigilant than leaders. Indeed, followers needed to acquire more resources than leaders, as only the latter could decide when to go to richer patches. Followers still benefit from dilution of predation risk compared with solitary individuals. For leaders, keeping their leadership status can be more important than incorporating new group members to increase dilution. We demonstrate that risk dilution impacts both optimal vigilance and space use, with fitness reward being tied to a member's ability to influence group space use.

Unusual triplet-triplet annihilation in a 3D copper(i) chloride coordination polymer.

A new coordination polymer (CP) defined as [Cu2Cl2(EtS(CH2)4SEt)4]n (CP2) was prepared by reacting EtS(CH2)4SEt with CuCl in acetonitrile in a 1 : 2 stoichiometric ratio. The X-ray structure reveals formation of non-porous 3D material composed of parallel 2D-[Cu2Cl2S2]n layers of Cl-bridged Cu2(µ-Cl)2 rhomboids assembled by EtS(CH2)4SEt ligands. A weak triplet emission (Φe < 0.0001) is observed in the 400-500 nm range with τe of 0.93 (298 K) and 3.5 ns (77 K) as major components. CP2 is the only 2nd example of emissive thioether/CuCl-containing material and combined DFT/TDDFT computations suggest the presence of lowest energy M/XLCT excited states. Upon increasing the photon flux (i.e. laser power), a triplet-triplet annihilation (TTA) is induced with quenching time constants of 72 ps (kQ = 1.3 × 1010 s-1) and 1.0 ns (kQ = 7.1 × 108 s-1) at 298 and 77 K, respectively, proceeding through an excitation energy migration operating via a Dexter process. Two distinct (Io)1/2 (Io = laser power) dependences of the emission intensity are depicted, indicating saturation as the observed emission increases with the excitation flux. These findings differ from that previously reported isomorphous CP [Cu2Br2(µ-EtS(CH2)4SEt)4]n (CP1), which exhibits no TTA behaviour at 77 K, and only one (laser power)2 dependence at 298 K. The ∼18-fold increase in kQ upon warming CP2 from 77 to 298 K indicates a temperature-aided TTA process. The significant difference between the presence (slower, CP2) and absence (CP1) of TTA at 77 K is explained by the larger unit cell contraction of the former upon cooling. This is noticeable by the larger change in inter-rhomboid CuCu separation for CP2.

Managing Genetic Diversity and Extinction Risk for a Rare Plains Bison (Bison bison bison) Population.

Unfenced plains bison are rare and only occur in a small number of locations throughout Canada and the United States. We examined management guidelines for maintenance of genetic health and population persistence for a small and isolated population of plains bison that occupy the interface between a protected national park and private agricultural lands. To address genetic health concerns, we measured genetic diversity relative to other populations and assessed the potential effects of genetic augmentation. We then used individual-based population viability analyses (PVA) to determine the minimum abundance likely to prevent genetic diversity declines. We assessed this minimum relative to a proposed maximum social carrying capacity related to bison use of human agricultural lands. We also used the PVA to assess the probability of population persistence given the limiting factors of predation, hunting, and disease. Our results indicate that genetic augmentation will likely be required to achieve genetic diversity similar to that of other plains bison populations. We also found that a minimum population of 420 bison yields low probability of additional genetic loss while staying within society-based maxima. Population estimates based on aerial surveys indicated that the population has been below this minimum since 2007. Our PVA simulations indicate that current hunting practices will result in undesirable levels of population extinction risk and further declines in genetic variability. Our study demonstrates that PVA can be used to evaluate potential management scenarios as they relate to long-term genetic conservation and population persistence for rare species.

A "Flexible" Rigid Rod, trans-Pt(PMe3)2(C≡CC6H4CN)2 (L1), to Form 2D [{Cu2(µ2-X)2}2(µ4-L1)] n Polymers (X = Br, I) Exhibiting the Largest Bathochromic Emissions.

The trans-Pt(PMe3)2(C≡CC6H4CN)2 organometallic ligand L1, which is prepared from 4-ethynylbenzonitrile and cis-Pt(PMe3)2Cl2, binds CuX salts to form two strongly luminescent two-dimensional coordination polymers (CPs) [{Cu2(µ2-X)2}2(µ4-L1)] n (X = I, CP1; X = Br, CP2). The emission quantum yields, Φe ≈ 30% at 298 K, are the largest ones for all CPs built upon the trans-Pt(PMe3)2(C≡CC6H4X)2 motifs (X = SMe, CN). X-ray crystallography reveals that, to accommodate these layered CPs, L1 must undergo major distortions of the C≡C-C angles (∼159°) and significant rotations about the Pt-CC bonds, so that the dihedral angles made by the two aromatic planes is 90° in a quasi-identical manner for both CPs. Together, these two features represent the largest distortion for trans-Pt(PMe3)2(C≡CC6H4X)2 complexes among all of the CPs built upon this type of ligand (2 of 16 entries). Concurrently, CP1 and CP2 also exhibit the most red-shifted emissions (λmax = 650 and 640 nm, respectively) known for this type of chromophore at room temperature. The {Cu2(µ2-X)2} rhomboids adopt the trans- (X = I, common) and cis-geometries (X = Br, extremely rare) making them "isomers" if excluding the fact that the halides are different. Density functional theory (DFT) and time-dependent DFT suggest that the triplet emissive excited state is metal/halide-to-ligand charge transfer in both cases despite this difference in rhomboid geometry.

Control of Structures and Emission Properties of (CuI) n 2-Methyldithiane Coordination Polymers.

A structurally unique and strongly luminescent nonporous 3D coordination polymer (CP) [Cu8I8(methyldithiane)4] n, CP3, has been prepared in a quasi-anticipated manner from 2-methyl-1,3-dithiane, L1, and CuI. This CP incorporates an unprecedented Cu8I8 cluster built upon two side-fused open cubanes. The crystal structure of CP3 has been determined at 100, 150, 200, 250, 300, 350, and 400 K to study the temperature dependence of the Cu···Cu distances. Two other topological 1D and 2D CPs isomers of formula [{Cu2I2}(L1)2] n featuring dinuclear {Cu2(µ2-I)2} rhomboids were also obtained independently by control of the reaction conditions. These two CPs convert into CP3 in hot PrCN, thus indicating that this latter material is the thermodynamic product. While CP1 and CP2 are not emissive, CP3 exhibits an intense luminescence due to the incorporation of the octanuclear Cu8I8 clusters as secondary building units within the network. The photophysical properties of CP3 have been investigated and rationalized by means of DFT and TDDFT computing. Furthermore, the thermal stability of these materials has been studied by ATG and DSC analyses. The Raman spectra of CP1-3 have been recorded in the solid state in the 50-500 cm-1 region.

Ecological processes determining the distribution dynamics of vole populations during forest succession.

The size and distribution of animal populations may vary drastically over time following a disturbance event. While both competition and predation can control the size of animal populations, changes in the relative importance of these two density-dependent processes remain poorly documented during ecological succession. Here, we combined habitat selection and optimal foraging theory to identify the processes that can explain the increase in red-backed voles (Myodes gapperi) during post-logging forest succession in boreal ecosystems. Specifically, we assessed the extent to which changes in intra- and interspecific competition and in predation risk can explain variation in abundance and distribution of voles during post-harvest forest succession. We estimated the abundances of the red-backed vole and of its main competitor, the deer mouse (Peromyscus maniculatus), in adjacent pairs of logged (5-66 years old) forest stands and uncut stands (> 120 years old). We found that voles increased their preference for uncut stands with increasing conspecific density. Foraging experiments revealed that in early-seral forest stands, voles increased their feeding effort in the presence of deer mice, particularly in safer food patches. This behaviour is expected from foraging theory when interspecific competitors increase predation risk. Apparent competition would thus limit the density of red-backed voles, and changes in the relative strength of this process during forest succession would control patterns of distribution and abundance of the species.

21st century United States emissions mitigation could increase water stress more than the climate change it is mitigating.

There is evidence that warming leads to greater evapotranspiration and surface drying, thus contributing to increasing intensity and duration of drought and implying that mitigation would reduce water stresses. However, understanding the overall impact of climate change mitigation on water resources requires accounting for the second part of the equation, i.e., the impact of mitigation-induced changes in water demands from human activities. By using integrated, high-resolution models of human and natural system processes to understand potential synergies and/or constraints within the climate-energy-water nexus, we show that in the United States, over the course of the 21st century and under one set of consistent socioeconomics, the reductions in water stress from slower rates of climate change resulting from emission mitigation are overwhelmed by the increased water stress from the emissions mitigation itself. The finding that the human dimension outpaces the benefits from mitigating climate change is contradictory to the general perception that climate change mitigation improves water conditions. This research shows the potential for unintended and negative consequences of climate change mitigation.

Collective decision-making promotes fitness loss in a fusion-fission society.

While collective decision-making is recognised as a significant contributor to fitness in social species, the opposite outcome is also logically possible. We show that collective movement decisions guided by individual bison sharing faulty information about habitat quality promoted the use of ecological traps. The frequent, but short-lived, associations of bison with different spatial knowledge led to a population-wide shift from avoidance to selection of agricultural patches over 9 years in and around Prince Albert National Park, Canada. Bison were more likely to travel to an agricultural patch for the first time by following conspecifics already familiar with agricultural patches. Annual adult mortality increased by 12% due to hunting of bison on agricultural lands. Maladaptive social behaviour accordingly was a major force that contributed to a ~50% population decline in less than a decade. In human-altered landscapes, social learning by group-living species can lead to fitness losses, particularly in fusion-fission societies.

Functional responses in animal movement explain spatial heterogeneity in animal-habitat relationships.

Understanding why heterogeneity exists in animal-habitat spatial relationships is critical for identifying the drivers of animal distributions. Functional responses in habitat selection - whereby animals adjust their habitat selection depending on habitat availability - are useful for describing animal-habitat spatial heterogeneity. However, they could be yielded by different movement tactics, involving contrasting interspecific interactions. Identifying functional responses in animal movement, rather than in emergent spatial patterns like habitat selection, could disentangle the effects of different movement behaviours on spatial heterogeneity in animal-habitat relationships. This would clarify how functional responses in habitat selection emerge and provide a general tool for understanding the mechanistic drivers of animal distributions. We tested this approach using data from GPS-collared woodland caribou (Rangifer tarandus), a prey species under top-down control. We tested how caribou selected and moved with respect to a key resource (lichen-conifer stands) as a function of the availability of surrounding refuge land-cover (closed-conifer stands), using step selection functions. Caribou selected resource patches more strongly in areas richer in refuge land-cover - a functional response in habitat selection. However, adjustments in multiple movement behaviours could have generated this pattern: stronger directed movement towards resource patches and/or longer residency within resource patches, in areas richer in refuges. Different contributions of these behaviours would produce contrasting forager spatial dynamics. We identified functional responses in both movement behaviours: caribou were more likely to move towards resource patches in areas richer in refuge land-cover, and to remain in these patches during movement steps. This tactic enables caribou to forage for longer in safer areas where they can rapidly seek refuge in dense cover when predators are detected. Our study shows that functional responses in movement can expose the context-dependent movement decisions that generate heterogeneity in animal-habitat spatial relationships. We used these functional responses to characterise anti-predator movement tactics employed by a large herbivore, but they could be applied in many different scenarios. The movement rules from functional responses in movement are well-suited to integration in spatial explicit individual-based models for forecasting animal distributions in landscapes undergoing environmental change.

Many places called home: the adaptive value of seasonal adjustments in range fidelity.

The vast majority of animal species display range fidelity, a space-use behaviour enhancing familiarity with local habitat features. While the fitness benefits of this behaviour have been demonstrated in a variety of taxa, some species or populations rather display infidelity, displacing their home range over time. Others, such as many ungulate species, show seasonal adjustments in their range fidelity to accommodate changes in the dominance of limiting factors or in the distribution of resources. Few empirical studies have explored the adaptive value of seasonal adjustments in range fidelity. Using boreal populations of woodland caribou (Rangifer tarandus caribou) as a biological model, we evaluated how range fidelity impacted individual performance during two seasons where juvenile and adult survival are limited by different predation pressures. Between 2004 and 2013, we monitored the survival, reproductive success, habitat selection and range fidelity of female caribou in the boreal forest of eastern Canada. Using resource selection functions, we assessed how seasonal range fidelity was linked to two fitness correlates: calf survival in summer and adult female survival in winter. Females displayed season-specific space use tactics: they selected previously used areas during calving and summer, but tended to shift their winter range from 1 year to the next. During calving and summer, range fidelity yielded relatively high fitness benefits, as females that did not lose their calf displayed stronger fidelity than females that did. In winter, however, adult survival was negatively linked to range fidelity, as females that survived selected areas further away from their seasonal range of the previous year than females that died. We provide one of the first evidences that making seasonal adjustments in range fidelity can be an adaptive behaviour influencing the spatial distribution of a threatened species. Assessing the seasonal nature of range fidelity tactics may improve our predictions of space use and associated fitness implications for species displaying this behaviour.

Platinum Complexes of N,N',N″,N‴-Diboronazophenines.

Azophenine, (α-C6H5NH)2(C6H5-N═C6H2═N-C6H5), well known to be non-emissive, was rigidified by replacing two amine protons by two difluoroboranes (BF2+) and further functionalized at the para-positions of the phenyl groups by luminescent trans-ArC≡C-Pt(PR3)2-C≡C ([Pt]) arms [Ar = C6H4 (R = Et), hexa(n-hexyl)truxene) (Tru; R = Bu)]. Two effects are reported. First, the linking of these [Pt] arms with the central azophenine (C6H4-N═C6H2(NH)2═N-C6H4; Q) generates very low energy charge-transfer (CT) singlet and triplet excited states (3,1([Pt]-to-Q)*) with absorption bands extending all the way to 800 nm. Second, the rigidification of azophenine by the incorporation of BF2+ units renders the low-lying CT singlet state clearly emissive at 298 and 77 K in the near-IR region. DFT computations place the triplet emission in the 1200-1400 nm range, but no phosphorescence was detected. The photophysical properties are investigated, and circumstantial evidence for slow triplet energy transfers, 3Tru* → Q, is provided.