Common barriers, but temporal dissonance: Genomic tests suggest ecological and paleo-landscape sieves structure a coastal riverine fish community.

Assessments of spatial and temporal congruency across taxa from genetic data provide insights into the extent to which similar processes structure communities. However, for coastal regions that are affected continuously by cyclical sea-level changes over the Pleistocene, congruent interspecific response will not only depend upon codistributions, but also on similar dispersal histories among taxa. Here, we use SNPs to test for concordant genetic structure among four codistributed taxa of freshwater fishes (Teleostei: Characidae) along the Brazilian Atlantic coastal drainages. Based on population relationships and hierarchical genetic structure analyses, we identify all taxa share the same geographic structure suggesting the fish utilized common passages in the past to move between river basins. In contrast to this strong spatial concordance, model-based estimates of divergence times indicate that despite common routes for dispersal, these passages were traversed by each of the taxa at different times resulting in varying degrees of genetic differentiation across barriers with most divergences dating to the Upper Pleistocene, even when accounting for divergence with gene flow. Interestingly, when this temporal dissonance is viewed through the lens of the species-specific ecologies, it suggests that an ecological sieve influenced whether species dispersed readily, with an ecological generalist showing the highest propensity for historical dispersal among the isolated rivers of the Brazilian coast (i.e., the most recent divergence times and frequent gene flow estimated for barriers). We discuss how our findings, and in particular what the temporal dissonance, despite common geographic passages, suggest about past dispersal structuring coastal communities as a function of ecological and paleo-landscape sieves.

Ancient DNA suggests modern wolves trace their origin to a Late Pleistocene expansion from Beringia.

Grey wolves (Canis lupus) are one of the few large terrestrial carnivores that have maintained a wide geographical distribution across the Northern Hemisphere throughout the Pleistocene and Holocene. Recent genetic studies have suggested that, despite this continuous presence, major demographic changes occurred in wolf populations between the Late Pleistocene and early Holocene, and that extant wolves trace their ancestry to a single Late Pleistocene population. Both the geographical origin of this ancestral population and how it became widespread remain unknown. Here, we used a spatially and temporally explicit modelling framework to analyse a data set of 90 modern and 45 ancient mitochondrial wolf genomes from across the Northern Hemisphere, spanning the last 50,000 years. Our results suggest that contemporary wolf populations trace their ancestry to an expansion from Beringia at the end of the Last Glacial Maximum, and that this process was most likely driven by Late Pleistocene ecological fluctuations that occurred across the Northern Hemisphere. This study provides direct ancient genetic evidence that long-range migration has played an important role in the population history of a large carnivore, and provides insight into how wolves survived the wave of megafaunal extinctions at the end of the last glaciation. Moreover, because Late Pleistocene grey wolves were the likely source from which all modern dogs trace their origins, the demographic history described in this study has fundamental implications for understanding the geographical origin of the dog.

Population turnover, behavioral conservatism, and rates of cultural evolution.

Cultural evolution facilitates behavioral adaptation in many species. The pace of cultural evolution can be accelerated by population turnover, where newcomers (immigrants or juvenile recruits) introduce adaptive cultural traits into their new group. However, where newcomers are naïve to the challenges of their new group, population turnover could potentially slow the rate of cultural evolution. Here, we model cultural evolution with population turnover and show that even if turnover results in the replacement of experienced individuals with naïve ones, turnover can still accelerate cultural evolution if (1) the rate of social learning is more than twice as fast as the turnover rate and (b) newcomers are more likely to learn socially than behaviorally conservative existing group members. Although population turnover is a relatively simple factor, it is common to all animal societies, and variation in the turnover rate may potentially play an important role in explaining variation in the occurrence and rates of adaptive cultural evolution across species.

Maximum stem diameter predicts liana population demography.

Determining population demographic rates is fundamental to understanding differences in species' life-history strategies and their capacity to coexist. Calculating demographic rates, however, is challenging and requires long-term, large-scale censuses. Body size may serve as a simple predictor of demographic rate; can it act as a proxy for demographic rate when those data are unavailable? We tested the hypothesis that maximum body size predicts species' demographic rate using repeated censuses of the 77 most common liana species on the Barro Colorado Island, Panama (BCI) 50-ha plot. We found that maximum stem diameter does predict species' population turnover and demography. We also found that lianas on BCI can grow to the enormous diameter of 635 mm, indicating that they can store large amounts of carbon and compete intensely with tropical canopy trees. This study is the first to show that maximum stem diameter can predict plant species' demographic rates and that lianas can attain extremely large diameters. Understanding liana demography is particularly timely because lianas are increasing rapidly in many tropical forests, yet their species-level population dynamics remain chronically understudied. Determining per-species maximum liana diameters in additional forests will enable systematic comparative analyses of liana demography and potential influence across forest types.

Demography: Fast and Slow.

Scientific ideas on the human population tend to be rooted in a "slow demography" paradigm, which emphasizes an inertial, predictable, self-contained view of population dynamics, mostly dependent on fertility and mortality. Yet, demography can also move fast. At the country level, it is crucial to empirically assess how fast demography moves by taking migratory movements into account, in addition to fertility and mortality. We discuss these ideas and present new estimates of the speed of population change, that is, country-level population turnover rates, as well as the share of turnover due to migration, for all countries in the world with available data between 1990 and 2020. Population turnover is inversely related to population size and development, and migratory movements tend to become important factors in shaping demography for both small and highly developed countries. Longitudinally, we analyze annual turnover data for Italy and Germany, documenting the changing speed of population change over time and its determinants. Accepting the "fast and slow" demography perspective has several implications for science and policy, which we discuss.

Early Alpine occupation backdates westward human migration in Late Glacial Europe.

Before the end of the Last Glacial Maximum (LGM, ∼16.5 ka ago)1 set in motion major shifts in human culture and population structure,2 a consistent change in lithic technology, material culture, settlement pattern, and adaptive strategies is recorded in Southern Europe at ∼18-17 ka ago. In this time frame, the landscape of Northeastern Italy changed considerably, and the retreat of glaciers allowed hunter-gatherers to gradually recolonize the Alps.3-6 Change within this renewed cultural frame (i.e., during the Late Epigravettian phase) is currently associated with migrations favored by warmer climate linked to the Bølling-Allerød onset (14.7 ka ago),7-11 which replaced earlier genetic lineages with ancestry found in an individual who lived ∼14 ka ago at Riparo Villabruna, Italy, and shared among different contexts (Villabruna Cluster).9 Nevertheless, these dynamics and their chronology are still far from being disentangled due to fragmentary evidence for long-distance interactions across Europe.12 Here, we generate new genomic data from a human mandible uncovered at Riparo Tagliente (Veneto, Italy), which we directly dated to 16,980-16,510 cal BP (2σ). This individual, affected by focal osseous dysplasia, is genetically affine to the Villabruna Cluster. Our results therefore backdate by at least 3 ka the diffusion in Southern Europe of a genetic component linked to Balkan/Anatolian refugia, previously believed to have spread during the later Bølling/Allerød event. In light of the new genetic evidence, this population replacement chronologically coincides with the very emergence of major cultural transitions in Southern and Western Europe.

Population turnover facilitates cultural selection for efficiency in birds.

Culture, defined as socially transmitted information and behaviors that are shared in groups and persist over time, is increasingly accepted to occur across a wide range of taxa and behavioral domains.1 While persistent, cultural traits are not necessarily static, and their distribution can change in frequency and type in response to selective pressures, analogous to that of genetic alleles. This has led to the treatment of culture as an evolutionary process, with cultural evolutionary theory arguing that culture exhibits the three fundamental components of Darwinian evolution: variation, competition, and inheritance.2-5 Selection for more efficient behaviors over alternatives is a crucial component of cumulative cultural evolution,6 yet our understanding of how and when such cultural selection occurs in non-human animals is limited. We performed a cultural diffusion experiment using 18 captive populations of wild-caught great tits (Parus major) to ask whether more efficient foraging traditions are selected for, and whether this process is affected by a fundamental demographic process-population turnover. Our results showed that gradual replacement of individuals with naive immigrants greatly increased the probability that a more efficient behavior invaded a population's cultural repertoire and outcompeted an established inefficient behavior. Fine-scale, automated behavioral tracking revealed that turnover did not increase innovation rates, but instead acted on adoption rates, as immigrants disproportionately sampled novel, efficient behaviors relative to available social information. These results provide strong evidence for cultural selection for efficiency in animals, and highlight the mechanism that links population turnover to this process.

Residential churn moderates the relationship between economic deprivation and psychiatric admission: evidence from Wales.

BACKGROUND: There is a well-established link between area-level socioeconomic deprivation and psychiatric admission rates. Social capital has been proposed as a possible protective factor that may buffer economically deprived communities, but it may be disrupted in areas with high population turnover. This study aims to test whether population turnover, hereafter called churn, moderates the social gradient of psychiatric admissions. METHODS: Population churn rates, low income rates and psychiatric admission rates for 1909 lower super output areas in Wales were analysed using Poisson generalised linear mixed-effects models. Additional analyses explored the impact of deprivation measured more generally and the potential confound of population density. RESULTS: Population churn moderated the association between socioeconomic deprivation and psychiatric admission rates, such that greater social gradients in admission rates were found in areas with greater churn. Economic deprivation and churn were also found to be independently positively associated with admission rates. These relationships remained significant when using a broader measure of deprivation and after adjusting for population density. CONCLUSION: High churn appears to exacerbate the detrimental effects of economic deprivation on mental health as well as being a risk factor in its own right. Residential stability rates should be considered when designing and implementing policies which aim to understand, prevent and treat mental health problems in at-risk communities.

Gang membership between ages 5 and 17 years in the United States.

PURPOSE: This study determined the frequency, prevalence, and turnover in gang membership between ages 5 and 17 years in the United States. METHODS: Data were from the National Longitudinal Survey of Youth 1997, which is representative of youth born between 1980 and 1984. Age-specific patterns of gang joining, participation, and leaving are estimated based on youths (N = 7,335) self-reported gang membership at the baseline and eight subsequent interviews, which were combined with population age estimates from the 2010 U.S. Census to produce national estimates of gang membership. Sampling variance-adjusted bounds were estimated based on assumptions about missing cases and survey design effects. Demographic and socioeconomic variables are used to compare differences between gang and nongang youth. RESULTS: Youth gang members were disproportionately male, black, Hispanic, from single-parent households, and families living below the poverty level. We estimated that there were 1,059,000 youth gang members in the United States in 2010 (bounds ranging from 675,000 to 1,535,000). The prevalence of youth gang membership was 2.0% (1.2%-2.8%), peaking at age 14 years at 5.0% (3.9%-6.0%). Annually, 401,000 (204,000-639,000) juveniles join gangs and 378,000 (199,000-599,000) exit gangs, with a turnover rate of 36%. CONCLUSIONS: We discovered that significantly more people are involved with gangs than previous estimates would suggest. Clinicians and policy makers must recognize that youth gang members may not conform to popular perceptions of gang demographics. The patterns of youth gang membership observed in this study support prevention programs aimed at children before the teen years. This strategy is more likely to succeed than gang intervention or suppression strategies aimed at teens.

Reach specificity in sediment E. coli population turnover and interaction with waterborne populations.

Sediment-borne Escherichia coli can elevate waterborne concentrations through sediment resuspension or hyporheic exchange. This study sought to correlate hydrological, sediment transport, and water quality variables with: (i) the temporal stability of sediment E. coli populations [concentrations, strain richness and similarity (Raup-Crick index)]; and (ii) the contribution of sediment E. coli to the water column as defined through a library-dependent microbial source tracking approach that matched waterborne E. coli isolates to sediment E. coli populations. Three monitoring locations differing in their hydrological characteristics and adjacent upland fecal sources (dairy operation, low-density residential, and tile-drained cultivated field) were investigated. Sediment E. coli population turnover was influenced by sediment transport at upstream, high-energy reaches, but not at the downstream low-energy reach. Sediment contributions to the water column averaged 13% and 18%, and fecal sources averaged 17% and 21% at the upstream sites adjacent to dairy operations and low-density residential areas, respectively. Waterborne E. coli at the downstream site had low matches to E. coli from reach sediments (1%), higher matches to the upstream sediments (27% and 12%), and an average of 14% matches to the tile drained field. The percentage of waterborne E. coli matching sediment-borne E. coli at each stream reach varied in correlations to hydrological and sediment transport variables, suggesting reach-specific differences in the role of sediment resuspension and hyporheic exchange on E. coli transport.