CONSUMER–RESOURCE INTERACTIONS AND THE EVOLUTION OF MIGRATION

Theoretical studies have demonstrated that selection will favor increased migration when fitnesses vary both temporally and spatially, but it is far from clear how pervasive those theoretical conditions are in nature. Although consumer–resource interactions are omnipresent in nature and can generate spatial and temporal variation, it is unknown even in theory whether these dynamics favor the evolution of migration. We develop a mathematical model to address whether and how migration evolves when variability in fitness is determined at least in part by consumer–resource coevolutionary interactions. Our analyses show that such interactions can drive the evolution of migration in the resource, consumer, or both species and thus supplies a general explanation for the pervasiveness of migration. Over short time scales, we show the direction of change in migration rate is determined primarily by the state of local adaptation of the species involved: rates increase when a species is locally maladapted and decrease when locally adapted. Our results reveal that long‐term evolutionary trends in migration rates can differ dramatically depending on the strength or weakness of interspecific interactions and suggest an explanation for the evolutionary divergence of migration rates among interacting species.     

Benthic indicators of sediment quality associated with run-of-river reservoirs

Freshwater ecosystems have been fragmented by the construction of large numbers of dams. In addition to disruption of ecological continuity and physical disturbance downstream, accumulation of large amounts of sediment within run-of-river reservoirs constitutes a latent ecotoxic risk to aquatic communities. To date, run-of-river reservoirs and ecotoxic risks associated with contaminated sediment to the biodiversity and functioning of such systems are little studied. Therefore, the main objective of this study was to describe macroinvertebrate assemblages, and the functioning of these systems, and to propose indicators of sediment contamination to integrate in in-situ risk assessment methodology. To identify specific assemblages of run-of-river reservoirs, we first compared macroinvertebrate assemblages and their biotrait profiles (i.e. from a database of biological and ecological traits) in reservoirs (n = 6) and associated river sites (upstream and downstream of dams). Then, we compared responses of assemblages and biotrait profiles to sediment contamination of the banks and channels of reservoirs to select the most useful spatial scale to identify sediment contamination. Nineteen indicator taxa were observed to be specifically associated with channel habitats of reservoirs. Among these, the abundance of three taxa (Tanypodinae (Diptera), Ephemerella (Ephemeroptera) and Atherix (Diptera)) revealed the effect of metal sediment contamination. “Between-reservoirs” differences in their biotrait profile were found along the contamination gradient, with a shift of communities’ composition and functionality, and an increase in functional similarity. Many traits (response traits), for example “maximum size”, “transverse distribution”, “substrate preferences”, “saprobity”, “temperature”, “resistance forms”, and “locomotion”, were specifically linked to contamination of sediments by metals. This study indicates how sediment contamination can change the structural and functional composition of run-of-river reservoir assemblages. Indicator taxa and response traits identified in this study could improve current risk assessment methodology and potentially enable prediction of the risks of contaminated sediments stored in reservoirs in downstream ecosystems.     

Association of DNA Methylation at CPT1A Locus with Metabolic Syndrome in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) Study

In this study, we conducted an epigenome-wide association study of metabolic syndrome (MetS) among 846 participants of European descent in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN). DNA was isolated from CD4+ T cells and methylation at ~470,000 cytosine-phosphate-guanine dinucleotide (CpG) pairs was assayed using the Illumina Infinium HumanMethylation450 BeadChip. We modeled the percentage methylation at individual CpGs as a function of MetS using linear mixed models. A Bonferroni-corrected P-value of 1.1 x 10⁻⁷ was considered significant. Methylation at two CpG sites in CPT1A on chromosome 11 was significantly associated with MetS (P for cg00574958 = 2.6x10^-14 and P for cg17058475 = 1.2x10^-9). Significant associations were replicated in both European and African ancestry participants of the Bogalusa Heart Study. Our findings suggest that methylation in CPT1A is a promising epigenetic marker for MetS risk which could become useful as a treatment target in the future.     

E2-BRCA1 RING interactions dictate synthesis of mono- or specific polyubiquitin chain linkages

An E3 ubiquitin ligase mediates the transfer of activated ubiquitin from an E2 ubiquitin-conjugating enzyme to its substrate lysine residues. Using a structure-based, yeast two-hybrid strategy, we discovered six previously unidentified interactions between the human heterodimeric RING E3 BRCA1-BARD1 and the human E2s UbcH6, Ube2e2, UbcM2, Ubc13, Ube2k and Ube2w. All six E2s bind directly to the BRCA1 RING motif and are active with BRCA1-BARD1 for autoubiquitination in vitro. Four of the E2s direct monoubiquitination of BRCA1. Ubc13-Mms2 and Ube2k direct the synthesis of Lys63- or Lys48-linked ubiquitin chains on BRCA1 and require an acceptor ubiquitin attached to BRCA1. Differences between the mono- and polyubiquitination activities of the BRCA1-interacting E2s correlate with their ability to bind ubiquitin noncovalently at a site distal to the active site. Thus, BRCA1 has the ability to direct the synthesis of specific polyubiquitin chain linkages, depending on the E2 bound to its RING.     

Non‐verbal mate retention behaviour in women and its relation to couple's relationship adjustment and satisfaction

The function of mate retention strategies is to preserve the bond between romantic partners and to prevent desertion, which is also why such behaviours are often elicited by the presence of a potential rival. Most existing studies on mate retention are based on self‐reports, which are prone to various biases. In this study, we observed non‐verbal behaviour of 47 long‐term romantic heterosexual couples during their interview with a female experimenter, whom the women in the couples may have perceived as a potential rival. We measured non‐verbal displays of mate retention tactics (direct guarding, intimacy inducement, appearance enhancement, and love and care display), as well as relationship maintenance strategies of openness and positivity. We expected that relationship quality as reported by both partners in the couple would be positively associated with ‘benefit‐provisioning’ mate retention behaviours and negatively associated with a ‘cost‐inflicting’ mate retention tactic (direct guarding). Relationship quality was assessed by Spanier's Dyadic Adjustment Scale using both the total score of dyadic adjustment and a Dyadic Satisfaction subscale. We found a significant association between both partners' dyadic adjustment and satisfaction and woman's appearance enhancement behaviours (such as self‐touch, hair flip and primp) in the presence of her partner and a potential rival. We also found a negative association between partner's dyadic adjustment and woman's direct guarding of partner using short looks, and a positive association between woman's intimacy‐inducing behaviour using long gaze and her own dyadic satisfaction and her partner's dyadic adjustment. Our results highlight the specific role of female attractiveness in later stages of romantic relationships within the context of mate retention and draw attention to the significance of the use of observational techniques in addition to self‐reports.     

LOCOMOTOR PERFORMANCE AT LOW TEMPERATURE AND THE EVOLUTION OF NOCTURNALITY IN GECKOS

Nocturnal geckos are active at body temperatures 10–35°C below the thermal optima for maximum rate of aerobic metabolism of diurnal lizards. Therefore, given ancestral (diurnal) lizard physiology, nocturnality causes a substantial thermal handicap in locomotor performance. In prior studies, we hypothesized that a low minimum cost of locomotion (C_min) in geckos was an adaptation that increased locomotor endurance capacity at low, nocturnal temperatures. However, C_min is only part of an integrated system that, in conjunction with the maximum rate of oxygen consumption, sets the maximum speed that can be sustained aerobically (termed the maximum aerobic speed or MAS). We conducted the first phylogenetic analysis of MAS and lizards and found that the greatest changes in MAS, C_min and (at activity temperatures) in the evolutionary history of lizards all coincided with the evolution of nocturnality in geckos. Geckos active at 15–25°C did not become optimized for nocturnal temperatures, or fully offset the thermal effects of nocturnality by evolving maximal rates of oxygen consumption comparable to diurnal lizards active at 35°C. Geckos did evolve MAS twice that of diurnal lizards running at low temperatures by evolving a remarkably low C_min. Allometric analysis and phylogenetically independent contrasts of , C_min, and MAS indicate a 72% evolutionary decrease in , (at activity temperatures) and a 50% evolutionary decrease in C_min concordant with the evolution of nocturnality in geckos. Experimental measurements show that decreased C_min in six species of gecko increased MAS by 50–120% compared to diurnal lizards at low temperatures. Thus, geckos sufficiently overcame the near paralyzing effects of nocturnal temperatures, but only offset about 50% of the decrease in MAS resulting from the low maximum rate of oxygen consumption. Although the nocturnal environment remains severely suboptimal, the evolution of a low cost of locomotion in the ancestor of geckos was highly adaptive for nocturnality. We also present a generalized approach to ecophysiological evolution that integrates phylogeny with the causal relationships among environment, physiology, and performance capacity. With respect to a clade, two hypotheses are central to our integrative approach: (1) a change of an environmental variable (e.g., temperature) causes a performance handicap; and (2) evolution of a physiological variable (e.g., minimum cost of locomotion [C_min]) increases performance in the derived environment. To test the hypothesis that evolution of a physiological variable is adaptive in nature, we suggest determining if individuals in nature perform at levels exceeding the performance capacity of their hypothetical ancestors and if this additional performance capacity is due to the evolution of the physiological variable in question.