Acculturation and depression are associated with short and long sleep duration among Mexican Americans in NHANES 2005-2018.

Acculturation and depression are linked to poor sleep quality and sleep problems that may explain ongoing health disparities for Hispanics/Latinos. We examined the associations of acculturation, depression, and sleep duration among the Mexican American population. We used a multinomial logistic regression model on cross-sectional data from the 2005-2018 National Health and Nutrition Examination Survey on 4,700 Mexican American adults aged ≥18 years old. The outcome of sleep duration was operationalized as short (≤6 h), optimal (7-8 h), and long (≥9 h). Acculturation was constructed using years living in the U.S. and language(s) spoken at home (majority Spanish, English and Spanish equally, majority English). Depression severity was assessed using the 9-item Patient Health Questionnaire. Covariates included gender, age, marital status, income, and U.S. citizenship. Speaking majority English (Adjusted Odds Ratio (AOR) = 1.23; 95% Confidence Interval (CI) = 1.00-1.52) and mild (AOR = 1.63; 95%CI = 1.32-2.01), moderate (AOR = 1.94; 95%CI = 1.43-2.63), and moderately severe/severe (AOR = 2.58; 95%CI = 1.72-3.88) levels of depression were significantly associated with short sleep duration. Living in the U.S. for ≥10 years (AOR = 1.61; 95%CI = 1.17-2.23) and moderately severe/severe depression (AOR = 2.30; 95%CI = 1.34-3.93) were significantly associated with long sleep duration. Our results provide additional evidence of a link between acculturation, depression, and short and long sleep duration among the Mexican American population. Understanding the sleep health of this population is important for informing future public health interventions and research. Additional investigation into the relationship between acculturation/depression and other sleep health measures among this population is warranted.

Temperature dependence of metabolic rate in tropical and temperate aquatic insects: Support for the Climate Variability Hypothesis in mayflies but not stoneflies.

A fundamental gap in climate change vulnerability research is an understanding of the relative thermal sensitivity of ectotherms. Aquatic insects are vital to stream ecosystem function and biodiversity but insufficiently studied with respect to their thermal physiology. With global temperatures rising at an unprecedented rate, it is imperative that we know how aquatic insects respond to increasing temperature and whether these responses vary among taxa, latitudes, and elevations. We evaluated the thermal sensitivity of standard metabolic rate in stream-dwelling baetid mayflies and perlid stoneflies across a ~2,000 m elevation gradient in the temperate Rocky Mountains in Colorado, USA, and the tropical Andes in Napo, Ecuador. We used temperature-controlled water baths and microrespirometry to estimate changes in oxygen consumption. Tropical mayflies generally exhibited greater thermal sensitivity in metabolism compared to temperate mayflies; tropical mayfly metabolic rates increased more rapidly with temperature and the insects more frequently exhibited behavioral signs of thermal stress. By contrast, temperate and tropical stoneflies did not clearly differ. Varied responses to temperature among baetid mayflies and perlid stoneflies may reflect differences in evolutionary history or ecological roles as herbivores and predators, respectively. Our results show that there is physiological variation across elevations and species and that low-elevation tropical mayflies may be especially imperiled by climate warming. Given such variation among species, broad generalizations about the vulnerability of tropical ectotherms should be made more cautiously.

Eco-Evolutionary Feedbacks Predict the Time Course of Rapid Life-History Evolution.

Organisms can change their environment and in doing so change the selection they experience and how they evolve. Population density is one potential mediator of such interactions because high population densities can impact the ecosystem and reduce resource availability. At present, such interactions are best known from theory and laboratory experiments. Here we quantify the importance of such interactions in nature by transplanting guppies from a stream where they co-occur with predators into tributaries that previously lacked both guppies and predators. If guppies evolve solely because of the immediate reduction in mortality rate, the strength of selection and rate of evolution should be greatest at the outset and then decline as the population adapts to its new environment. If indirect effects caused by the increase in guppy population density in the absence of predation prevail, then there should be a lag in guppy evolution because time is required for them to modify their environment. The duration of this lag is predicted to be associated with the environmental modification caused by guppies. We observed a lag in life-history evolution associated with increases in population density and altered ecology. How guppies evolved matched predictions derived from evolutionary theory that incorporates such density effects.

Thermal Acclimation Ability Varies in Temperate and Tropical Aquatic Insects from Different Elevations.

It has long been recognized that populations and species occupying different environments vary in their thermal tolerance traits. However, far less attention has been given to the impact of different environments on the capacity for plastic adjustments in thermal sensitivity, i.e., acclimation ability. One hypothesis is that environments characterized by greater thermal variability and seasonality should favor the evolution of increased acclimation ability compared with environments that are aseasonal or thermally stable. Additionally, organisms under selection for high heat tolerance may experience a trade-off and lose acclimation ability. Few studies have tested these non-mutually exclusive hypotheses at both broad latitudinal and local elevation scales in phylogenetically paired taxa. Here, we measure short-term acclimation ability of the critical thermal maximum (CTMAX) in closely related temperate and tropical mayflies (Ephemeroptera) and stoneflies (Plecoptera) from mountain streams at different elevations. We found that stream temperature was a good predictor of acclimation ability in mayflies, but not in stoneflies. Specifically, tropical mayflies showed reduced acclimation ability compared with their temperate counterparts. High elevation tropical mayflies had greater acclimation ability than low elevation mayflies, which reflected the wider temperature variation experienced in high elevation streams. In contrast, temperate and tropical stoneflies exhibited similar acclimation responses. We found no evidence for a trade-off between heat tolerance and acclimation ability in either taxonomic order. The acclimation response in stoneflies may reflect their temperate origin or foraging mode. In combination with previous studies showing tropical taxa have narrower thermal breadths, these results demonstrate that many lower elevation tropical aquatic insects are more vulnerable to climate warming than their temperate relatives.

Phenotypic plasticity changes correlations of traits following experimental introductions of Trinidadian guppies (Poecilia reticulata).

Colonization of novel environments can alter selective pressures and act as a catalyst for rapid evolution in nature. Theory and empirical studies suggest that the ability of a population to exhibit an adaptive evolutionary response to novel selection pressures should reflect the presence of sufficient additive genetic variance and covariance for individual and correlated traits. As correlated traits should not respond to selection independently, the structure of correlations of traits can bias or constrain adaptive evolution. Models of how multiple correlated traits respond to selection often assume spatial and temporal stability of trait-correlations within populations. Yet, trait-correlations can also be plastic in response to environmental variation. Phenotypic plasticity, the ability of a single genotype to produce different phenotypes across environments, is of particular interest because it can induce population-wide changes in the combination of traits exposed to selection and change the trajectory of evolutionary divergence. We tested the ability of phenotypic plasticity to modify trait-correlations by comparing phenotypic variance and covariance in the body-shapes of four experimental populations of Trinidadian guppies (Poecilia reticulata) to their ancestral population. We found that phenotypic plasticity produced both adaptive and novel aspects of body-shape, which was repeated in all four experimental populations. Further, phenotypic plasticity changed patterns of covariance among morphological characters. These findings suggest our ability to make inferences about patterns of divergence based on correlations of traits in extant populations may be limited if novel environments not only induce plasticity in multiple traits, but also change the correlations among the traits.

Parallelism isn't perfect: could disease and flooding drive a life-history anomaly in Trinidadian guppies?

Nonparallel evolution, where independent populations occupy similar environments but show phenotypic differences, can uncover previously ignored selective factors. We investigated a nonparallelism in the life-history strategy of a Trinidadian guppy population, a system famous for parallel adaptation to differences in predation risk. We tested the hypothesis that high mortality drives an observed fast life-history pattern (i.e., earlier maturation and more frequent reproductive events) that is atypical for a low-predation environment. Using mark-recapture techniques, we compared neighboring low-predation populations, finding significantly higher mortality rates in the population with atypical life-history traits. Mortality was elevated during the wet season, when flooding was common. Moreover, individuals from the anomalous population were more likely to transition from healthy to infected disease states. Our results stand out against previous patterns observed in this system, indicating that higher mortality caused by disease and flooding may have selected for a faster life history. Thus, we highlight that even in systems famous for parallel adaptation, variation in selective pressures can result in nonparallel phenotypic evolution.

Plasticity of parental care under the risk of predation: how much should parents reduce care?

Predation can be an important agent of natural selection shaping parental care behaviours, and can also favour behavioural plasticity. Parent birds often decrease the rate that they visit the nest to provision offspring when perceived risk is high. Yet, the plasticity of such responses may differ among species as a function of either their relative risk of predation, or the mean rate of provisioning. Here, we report parental provisioning responses to experimental increases in the perceived risk of predation. We tested responses of 10 species of bird in north temperate Arizona and subtropical Argentina that differed in their ambient risk of predation. All species decreased provisioning rates in response to the nest predator but not to a control. However, provisioning rates decreased more in species that had greater ambient risk of predation on natural nests. These results support theoretical predictions that the extent of plasticity of a trait that is sensitive to nest predation risk should vary among species in accordance with predation risk.

Predator-induced phenotypic plasticity in metabolism and rate of growth: rapid adaptation to a novel environment.

Novel environments often impose directional selection for a new phenotypic optimum. Novel environments, however, can also change the distribution of phenotypes exposed to selection by inducing phenotypic plasticity. Plasticity can produce phenotypes that either align with or oppose the direction of selection. When plasticity and selection are parallel, plasticity is considered adaptive because it provides a better pairing between the phenotype and the environment. If the plastic response is incomplete and falls short of producing the optimum phenotype, synergistic selection can lead to genetic divergence and bring the phenotype closer to the optimum. In contrast, non-adaptive plasticity should increase the strength of selection, because phenotypes will be further from the local optimum, requiring antagonistic selection to overcome the phenotype-environment mismatch and facilitate adaptive divergence. We test these ideas by documenting predator-induced plasticity for resting metabolic rate and growth rate in populations of the Trinidadian guppy (Poecilia reticulata) adapted to high and low predation. We find reduced metabolic rates and growth rates when cues from a predator are present during development, a pattern suggestive of adaptive and non-adaptive plasticity, respectively. When we compared populations recently transplanted from a high-predation environment into four streams lacking predators, we found evidence for rapid adaptive evolution both in metabolism and growth rate. We discuss the implications for predicting how traits will respond to selection, depending on the type of plasticity they exhibit.

Genetically and environmentally mediated divergence in lateral line morphology in the Trinidadian guppy (Poecilia reticulata).

Fish and other aquatic vertebrates use their mechanosensory lateral line to detect objects and motion in their immediate environment. Differences in lateral line morphology have been extensively characterized among species; however, intraspecific variation remains largely unexplored. In addition, little is known about how environmental factors modify development of lateral line morphology. Predation is one environmental factor that can act both as a selective pressure causing genetic differences between populations, and as a cue during development to induce plastic changes. Here, we test whether variation in the risk of predation within and among populations of Trinidadian guppies (Poecilia reticulata) influences lateral line morphology. We compared neuromast arrangement in wild-caught guppies from distinct high- and low-predation population pairs to examine patterns associated with differences in predation pressure. To distinguish genetic and environmental influences, we compared neuromast arrangement in guppies from different source populations reared with and without exposure to predator chemical cues. We found that the distribution of neuromasts across the body varies between populations based on both genetic and environmental factors. To the best of our knowledge, this study is the first to demonstrate variation in lateral line morphology based on environmental exposure to an ecologically relevant stimulus.

Local adaptation and the evolution of phenotypic plasticity in Trinidadian guppies (Poecilia reticulata).

Divergent selection pressures across environments can result in phenotypic differentiation that is due to local adaptation, phenotypic plasticity, or both. Trinidadian guppies exhibit local adaptation to the presence or absence of predators, but the degree to which predator-induced plasticity contributes to population differentiation is less clear. We conducted common garden experiments on guppies obtained from two drainages containing populations adapted to high- and low-predation environments. We reared full-siblings from all populations in treatments simulating the presumed ancestral (predator cues present) and derived (predator cues absent) conditions and measured water column use, head morphology, and size at maturity. When reared in presence of predator cues, all populations had phenotypes that were typical of a high-predation ecotype. However, when reared in the absence of predator cues, guppies from high- and low-predation regimes differed in head morphology and size at maturity; the qualitative nature of these differences corresponded to those that characterize adaptive phenotypes in high- versus low-predation environments. Thus, divergence in plasticity is due to phenotypic differences between high- and low-predation populations when reared in the absence of predator cues. These results suggest that plasticity might initially play an important role during colonization of novel environments, and then evolve as a by-product of adaptation to the derived environment.

Experimental studies of evolution in guppies: a model for understanding the evolutionary consequences of predator removal in natural communities.

Guppies (Poecilia reticulata) in Trinidadian streams are found with a diversity of predators in the lower reaches of streams, but few predators in the headwaters. These differences have caused the adaptive evolution of guppy behaviour, morphology, male colouration and life history. Waterfalls often serve as barriers to the upstream distribution of predators and/or guppies. Such discontinuities make it possible to treat streams like giant test tubes by introducing guppies or predators to small segments of streams from which they were previously excluded. Such experiments enable us to document how fast evolution can occur and the fine spatial scales over which adaptation is possible. They also demonstrate that the role predators play in structuring this ecosystem resembles many others studied from a more purely ecological perspective; in these streams, as elsewhere, predators depress the numbers of individuals in prey species which in turn reduces the effects of the prey species on other trophic levels and hence the structure of the ecosystem. A focus on predators is important in conservation biology because predators are often the organisms that are most susceptible to local extinction. Their selective loss occurs because large predators have been deliberately exterminated and/or are more susceptible to environmental disturbances. Furthermore, we will argue that predator re-introductions might be destabilizing if, in the absence of predators, their prey have evolved in a fashion that makes them highly susceptible to predation, even after time intervals as short as 50-100 years. A better understanding of the evolutionary impacts of top predators will be critical goal for the policy and practice of large carnivore restoration in the future.