Demographic Fluctuations Research Articles

Living through changing climates: Temperature and seasonality correlate with population fluctuations among Holocene hunter-fisher-gatherers on the west coast of Norway

The use of archaeological proxy records representative of population dynamics is paramount for a richer understanding of prehistoric cultural change, but its use require a dialectic assessment between proximate climatic drivers and ultimate cultural responses. Focusing on the Stone Age archaeological record of Western Norway (11,500–4300 cal. BP), this paper presents an exhaustive empirical curation and statistical testing between changing climates and demographic responses among coastal hunter-fisher-gatherers. The results connect long-term demographic fluctuations with changes in annual mean temperatures and seasonality and the results are discussed in relation changes in technology, subsistence and mobility. The paper also highlights the process of population decline and cultural loss towards the end of the Late Mesolithic (ca. 7000–6000 cal. BP) and emerging cultural novelties and population re-growth during the Early and Middle Neolithic (ca. 6000–4300 cal. BP). However, despite its strong correlation, the archaeological record of Western Norway lacks sufficient detail to ascribe an exclusive explanatory role to climate change, especially in episodes of significant population decline. This helps to emphasise that changing climates, while evidently central, form but a part of a larger system of interactions leading to demographic fluctuations and cultural change, the substantiation of which requires significant empirical improvements to the archaeological record.

Demographic fluctuations of an extravagant congregation in the capital of New Spain (1703-1753)

Los predicadores fueron asignados a la evangelización de la zona centro-sur, incluyendo el actual territorio de Oaxaca, constituyendo la provincia de San Hipólito mártir, dominando las lenguas de la región y favoreciéndolos ante las disputas con franciscanos y agustinos por el adoctrinamiento de los mixtecos y zapotecos avecindados en la capital novohispana, en jurisdicción de los frailes disputantes. Es así que, los dominicos fueron los encargados de impartirles los sacramentos a esta feligresía, reconocida canónicamente como extravagantes dada la falta de asiento fijo dentro de la capital novohispana, pero que lograron congregarse y erigir su capilla bajo la advocación rosariana. En tanto, este artículo reconstruye el perfil demográfico de los extravagantes empleando como principal corpus documental, los libros sacramentales de la capilla del Rosario del convento de Santo Domingo de México con fechas extremas de 1703-1753, mismas que delimitan la temporalidad del estudio.

Freshwater turtle populations as bioindicators following an oil spill: Delayed demographic changes reveal long-term impacts

Chronic, long-term impacts of oil spill disasters on wildlife often exceed short-term, highly visible mass mortalities and widespread oiling of individuals. Species with long lifespans, late maturation, and low recruitment rates are particularly vulnerable to long-term population-level impacts but can be useful as indicator species for ecosystem recovery. In 2010, one of the largest freshwater oil spills in the U.S. occurred in the Kalamazoo River, MI, when 3.2 million L of spilled oil impacted 56 km of river and associated wildlife. During cleanup and restoration efforts in 2010–2011, thousands of northern map turtles (Graptemys geographica) were captured, cleaned, and released. During 2019–2020 northern map turtles were captured to evaluate changes in the population size, demography, and size classes nine to ten years later.Population demography shifts occurred in the first few years after the spill in a species that otherwise exhibits minimal demographic fluctuation under “normal” conditions. In comparing demographic parameters at the time of the oil spill to values ∼ 10 years post-spill, a nearly 30% reduction in population size was detected, distribution of body size shifted to smaller males and females, and there was a shift in the population sex ratio between 2011 and 2019. There were also signals of failed recruitment in cohorts that would have hatched during the years immediately before and after the oil spill. These data suggest that beyond the direct mortality caused by the spill, declines in the estimated population size and shifts in the size distribution of northern map turtles are likely indicative of negative demographic impacts incurred following the 2010 oil spill and resulting cleanup.

Demographic fluctuations and selection during host-parasite co-evolution interactively increase genetic diversity.

Host-parasite interactions can cause strong demographic fluctuations accompanied by selective sweeps of resistance/infectivity alleles. Both demographic bottlenecks and frequent sweeps are expected to reduce the amount of segregating genetic variation and therefore might constrain adaptation during co-evolution. Recent studies, however, suggest that the interaction of demographic and selective processes is a key component of co-evolutionary dynamics and may rather positively affect levels of genetic diversity available for adaptation. Here, we provide direct experimental testing of this hypothesis by disentangling the effects of demography, selection and their interaction in an experimental host-parasite system. We grew 12 populations of a unicellular, asexually reproducing algae (Chlorella variabilis) that experienced either growth followed by constant population sizes (three populations), demographic fluctuations (three populations), selection induced by exposure to a virus (three populations), or demographic fluctuations together with virus-induced selection (three populations). After 50 days (~50 generations), we conducted whole-genome sequencing of each algal host population. We observed more genetic diversity in populations that jointly experienced selection and demographic fluctuations than in populations where these processes were experimentally separated. In addition, in those three populations that jointly experienced selection and demographic fluctuations, experimentally measured diversity exceeds expected values of diversity that account for the cultures' population sizes. Our results suggest that eco-evolutionary feedbacks can positively affect genetic diversity and provide the necessary empirical measures to guide further improvements of theoretical models of adaptation during host-parasite co-evolution.

Using the radiocarbon dates of Central Africa for studying long-term demographic trends of the last 50,000 years: potential and pitfalls

ABSTRACT This paper presents the first review of biases impacting Pleistocene and Holocene radiocarbon dates from Central Africa. Based on the pooling of the research expertise of the co-authors, twenty-four biases are listed, explained and documented and their impact on any radiocarbon date corpus demonstrated. To achieve this, a new corpus has been created of 1764 radiocarbon and TL assays from 601 archaeological sites published in the literature. Each date has been checked for its context. The irregular dynamics of research in space and time seriously impact the end result of previous analyses aiming to achieve a regional understanding of past demographic fluctuations. While peaks in the number of dates from the late Holocene seem to correspond to a positive demographic trend, it is suggested that the declines identified cannot be of any such use for the time being and that today’s picture does not presently support claims of a population “crash” at a regional or local level for any time period. The numbers are obscured by overall research deficits identifiable throughout the region. The maps of the dated sites presented offer good evidence of this and illustrate the vast expanses where no archaeological research has yet been carried out. The number of radiocarbon dates in Central Africa is more an indicator of the effort archaeologists have put into understanding a settlement than it is of ancient demographics. Successive waves of incoming people since c. 3500–3000 cal. BP, the two most important ones known since the 1990s, have created a cultural mosaic of coexisting technological groups. The last 40 years of research have revealed the inner complexity of these waves, some of which avoided parts of the region for centuries, thereby creating an irregular cultural mosaic of land use that is outlined by patterning in the radiocarbon dates.

Microbial population dynamics decouple growth response from environmental nutrient concentration

How the growth rate of a microbial population responds to the environmental availability of chemical nutrients and other resources is a fundamental question in microbiology. Models of this response, such as the widely used Monod model, are generally characterized by a maximum growth rate and a half-saturation concentration of the resource. What values should we expect for these half-saturation concentrations, and how should they depend on the environmental concentration of the resource? We survey growth response data across a wide range of organisms and resources. We find that the half-saturation concentrations vary across orders of magnitude, even for the same organism and resource. To explain this variation, we develop an evolutionary model to show that demographic fluctuations (genetic drift) can constrain the adaptation of half-saturation concentrations. We find that this effect fundamentally differs depending on the type of population dynamics: Populations undergoing periodic bottlenecks of fixed size will adapt their half-saturation concentrations in proportion to the environmental resource concentrations, but populations undergoing periodic dilutions of fixed size will evolve half-saturation concentrations that are largely decoupled from the environmental concentrations. Our model not only provides testable predictions for laboratory evolution experiments, but it also reveals how an evolved half-saturation concentration may not reflect the organism's environment. In particular, this explains how organisms in resource-rich environments can still evolve fast growth at low resource concentrations. Altogether, our results demonstrate the critical role of population dynamics in shaping fundamental ecological traits.

Migratory behaviour is positively associated with genetic diversity in butterflies.

Migration is typically associated with risk and uncertainty at the population level, but little is known about its cost-benefit trade-offs at the species level. Migratory insects in particular often exhibit strong demographic fluctuations due to local bottlenecks and outbreaks. Here, we use genomic data to investigate levels of heterozygosity and long-term population size dynamics in migratory insects, as an alternative to classical local and short-term approaches such as regional field monitoring. We analyse whole-genome sequences from 97 Lepidoptera species and show that individuals of migratory species have significantly higher levels of genome-wide heterozygosity, a proxy for effective population size, than do nonmigratory species. Also, we contribute whole-genome data for one of the most emblematic insect migratory species, the painted lady butterfly (Vanessa cardui), sampled across its worldwide distributional range. This species exhibits one of the highest levels of genomic heterozygosity described in Lepidoptera (2.95 ± 0.15%). Coalescent modelling (PSMC) shows historical demographic stability in V. cardui, and high effective population size estimates of 2-20 million individuals 10,000 years ago. The study reveals that the high risks associated with migration and local environmental fluctuations do not seem to decrease overall genetic diversity and demographic stability in migratory Lepidoptera. We propose a "compensatory" demographic model for migratory r-strategist organisms in which local bottlenecks are counterbalanced by reproductive success elsewhere within their typically large distributional ranges. Our findings highlight that the boundaries of populations are substantially different for sedentary and migratory insects, and that, in the latter, local and even regional field monitoring results may not reflect whole population dynamics. Genomic diversity patterns may elucidate key aspects of an insect's migratory nature and population dynamics at large spatiotemporal scales.

Population Genomics for Insect Conservation.

Insects constitute vital components of ecosystems. There is alarming evidence for global declines in insect species diversity, abundance, and biomass caused by anthropogenic drivers such as habitat degradation or loss, agricultural practices, climate change, and environmental pollution. This raises important concerns about human food security and ecosystem functionality and calls for more research to assess insect population trends and identify threatened species and the causes of declines to inform conservation strategies. Analysis of genetic diversity is a powerful tool to address these goals, but so far animal conservation genetics research has focused strongly on endangered vertebrates, devoting less attention to invertebrates, such as insects, that constitute most biodiversity. Insects' shorter generation times and larger population sizes likely necessitate different analytical methods and management strategies. The availability of high-quality reference genome assemblies enables population genomics to address several key issues. These include precise inference of past demographic fluctuations and recent declines, measurement of genetic load levels, delineation of evolutionarily significant units and cryptic species, and analysis of genetic adaptation to stressors. This enables identification of populations that are particularly vulnerable to future threats, considering their potential to adapt and evolve. We review the application of population genomics to insect conservation and the outlook for averting insect declines.

Effect of compositional fluctuation on the survival of bet-hedging species

Understanding the coexistence of diverse species in a changing environment is an important problem in community ecology. Bet-hedging is a strategy that helps species survive in such changing environments. However, studies of bet-hedging have often focused on the expected long-term growth rate of the species by itself, neglecting competition with other coexisting species. Here we study the extinction risk of a bet-hedging species in competition with others. We show that there are three contributions to the extinction risk. The first is the usual demographic fluctuation due to stochastic reproduction and selection processes in finite populations. The second, due to the fluctuation of population growth rate caused by environmental changes, may actually reduce the extinction risk for small populations. Besides those two, we reveal a third contribution, which is unique to bet-hedging species that diversify into multiple phenotypes: The phenotype composition of the population will fluctuate over time, resulting in increased extinction risk. We compare such compositional fluctuation to the demographic and environmental contributions, showing how they have different effects on the extinction risk depending on the population size, generation overlap, and environmental correlation.

Growth instabilities shape morphology and genetic diversity of microbial colonies

Cellular populations assume an incredible variety of shapes ranging from circular molds to irregular tumors. While we understand many of the mechanisms responsible for these spatial patterns, little is known about how the shape of a population influences its ecology and evolution. Here, we investigate this relationship in the context of microbial colonies grown on hard agar plates. This a well-studied system that exhibits a transition from smooth circular disks to more irregular and rugged shapes as either the nutrient concentration or cellular motility is decreased. Starting from a mechanistic model of colony growth, we identify two dimensionless quantities that determine how morphology and genetic diversity of the population depend on the model parameters. Our simulations further reveal that population dynamics cannot be accurately described by the commonly-used surface growth models. Instead, one has to explicitly account for the emergent growth instabilities and demographic fluctuations. Overall, our work links together environmental conditions, colony morphology, and evolution. This link is essential for a rational design of concrete, biophysical perturbations to steer evolution in the desired direction.

Phylogeography of the mesic-adapted striped mouse, Rhabdomys dilectus chakae (Rodentia: Muridae) in forest margins of the Eastern Cape and southern KwaZulu-Natal provinces of South Africa

Abstract Rhabdomys is a genus that occupies a variety of habitats, including forest margins. Among the Rhabdomys taxa, Rhabdomys dilectus chakae has a distribution that covers the eastern seaboard of South Africa, with a poorly defined divergence date from its sister taxon Rhabdomys dilectus dilectus. Here, we study three mitochondrial markers (cytochrome b, cytochrome c oxidase I and partial control region) of R. d. chakae across the Eastern Cape and KwaZulu-Natal forests of South Africa, aiming to determine the cladogenesis (molecular dating) and effective population size of this subspecies through time, in addition to its cladogenesis in relationship to other species within the genus. A phylogenetic analysis revealed six clades within Rhabdomys, confirming that our study area is occupied solely by R. d. chakae, to the exclusion of other recognized sibling species. A fossil-calibrated Bayesian relaxed molecular clock estimated a recent split between R. d. chakae and R. d. dilectus ~1.4 ± 0.35 Mya and between two Rhabdomys pumilio groups, coastal A and B, at 1.16 ± 0.44 Mya. Coalescent Bayesian skyline plots revealed a stable population of R. d. chakae in the study area that was in slow decline until 2500 years ago, when there was an expansion in the late Holocene. Radiation within Rhabdomys dates as far back as 4.27 Mya, and subsequent demographic fluctuations primarily reflect palaeoclimatic changes.

Jerusalem 1099

On 15 July 1099, after more than four and a half centuries of Muslim rule, Jerusalem fell to the army of the First Crusade and for the next 88 years it became once again a Christian city. At that time, the city’s population may have numbered hundreds rather than the thousands of earlier periods, but it seems to have grown afterwards. The size of the late 12th century population may therefore have been closer to that of the mid-11th century, perhaps around 20,000–30,000, that is to say roughly the same size as Acre, Tyre, Florence or London in the same period. Along with these demographic fluctuations and the reduction of the area defended by city-walls, this paper analyses the impact of Christian rule on the town structures. From the conversion of the former Aqṣā Mosque as a royal palace, and then as the Temple’s headquarters, to the renovation of the Citadel as a small triangular-shaped fortress, and mostly to the important changes made in the Holy Sepulchre, with the enlargement of the church and the addition of an adjoining monastic cloister.

A Review of The Current Status of Migratory Wild Birds in Iraq and Syria

Iraq and Syria are among the countries that are frequented by wild birds in great numbers and species due to the abundance of water, green spaces, moderate climate in winter and the lack of predators. The two countries fall under the migration line of birds that stretches between East Asia and East Africa. The results of the survey, which were conducted nearly twenty years ago, indicated that there are at least 400 species of migratory birds coming to Iraq and Syria (The majority are from the Accipitres (Accipitridae) and passerines (Passeriformes)). In Iraq, the marshes (Al-Ahwar) are inhabited by species of birds that are rare in other parts of the world like the Iraq Babbler (Turdoides squamiceps) and the rocking reed of Basra (Acrocephalus griseldis). The rare endangered Namaqua Dove (Oena Capensis) was seen in the Syrian Badia. Recently, the status of the deputed birds has decreased in terms of numbers and species due to a set of reasons, the most important of which is the phenomenon of over-hunting, which has negatively affected the numbers of birds, especially birds that are threatened with extinction and included in the red list such as the Ferruginous duck (Aythya nyroca) and the Eurasian teal (Anas Crecca). The demographic fluctuation and war conditions have led to the reluctance of some species to come to Iraq and Syria and change the course of their migration to other places. The emergence of some non-traditional methods of hunting by bird hunters, such as the establishment of artificial waterbodies to attract waterfowl, led to an unprecedented decline in the numbers of these birds. The lack of legal oversight, lack of accountability, and the tendency of bird hunters to hunt in uncontrolled areas increased the great damage to wild birds in particular and to wildlife in general.

Unveiling the Mycodrosophila projectans (Diptera, Drosophilidae) species complex: Insights into the evolution of three Neotropical cryptic and syntopic species.

The Zygothrica genus group has been shown to be speciose, with a high number of cryptic species. DNA barcoding approaches have been a valuable tool to uncover cryptic diversity in this lineage, as recently suggested for the Neotropical Mycodrosophila projectans complex, which seems to comprise at least three different species. The aim of this study was to confirm the subdivision of the M. projectans complex while shedding some light on the patterns and processes related to its diversification. In this sense, the use of single and multi-locus datasets under phylogenetic, distance, coalescence, and diagnostic nucleotide approaches confirmed the presence of at least three species under the general morphotype previously described as M. projectans. Only a few subtle morphological differences were found for the three species in terms of aedeagus morphology and abdominal color patterns. Ecologically, sympatry and syntopy seem to be recurrent for these three cryptic species, which present widely overlapping niches, implying niche conservatism. This morphological and ecological similarity has persisted though cladogenesis within the complex, which dates back to the Miocene, providing an interesting example of morphological conservation despite ancient divergence. These results, in addition to contrasting patterns of past demographic fluctuations, allowed us to hypothesize patterns of allopatric or parapatric diversification with secondary contact in Southern Brazil. Nevertheless, genetic diversity was generally high within species, suggesting that migration may encompass an adaptive response to the restrictions imposed by the ephemerality of resources.

PECLIARITIES OF SPATIAL-TERRITORIAL ORGANIZATION OF MEDICAL-REHABILITATION CENTERS OF POLITRAUMA

The article considers the main urban issues related to the location of health care facilities, including medical rehabilitation centers, in the city structure. The general structure of the system of health care institutions is analyzed. Proposals for the spatial and territorial organization of medical rehabilitation centers, which has a direct impact on the functional and planning organization and the formation of spatial solutions of medical institutions of this type. Currently in Ukraine in most cases rehabilitation centers are located in adapted buildings and structures, due to which there is a lack of its own adjacent territory, and their functional and planning structure almost does not meet international requirements and standards, they have a broken communication scheme that does not allow patients of the institution in full. Due to the hostilities in the East, the last few years have been a difficult test for the rehabilitation and rehabilitation sectors, which were not prepared for such challenges due to the deterioration and obsolescence of domestic medical rehabilitation centers. The network of health care facilities was mostly formed during the Soviet era and, of course, needs thorough renewal and modernization, because the rapid development of medical technology requires flexibility in architectural and spatial planning of the treatment environment, able to quickly adapt to new technological processes, innovative medical equipment, changes in the prevailing diseases, demographic fluctuations, etc. Thus, on the basis of the conducted research the characteristics of types of placement in the urban fabric and spatial-territorial organization of zones for medical rehabilitation centers of polytrauma are formulated.

A chromosome-level genome of the human blood fluke Schistosoma japonicum identifies the genomic basis of host-switching.

The evolution and adaptation of S.japonicum, a zoonotic parasite that causes human schistosomiasis, remain unclear because of the lack of whole-genome data. We construct a chromosome-level S.japonicum genome and analyze it together with 72 samples representing six populations of the entire endemic region. We observe a Taiwan zoophilic lineage splitting from zoonotic populations ∼45,000 years ago, consistent with the divergent history of their intermediate hosts. Interestingly, we detect a severe population bottleneck in S.japonicum, largely coinciding with human history in Asia during the last glacial maximum. We identify several genomic regions underlying natural selection, including GATAD2A and Lmln, both showing remarkable differentiation among different areas. RNAi knockdown suggests association of GATAD2A with parasite development and infection in definitive hosts, while Lmln relates to the specificity of the intermediate hosts. Our study provides insights into the evolution of S.japonicum and serves as a resource for further studies.

DNA barcoding and phylogeography of the Hoplias malabaricus species complex

Hoplias malabaricus (Bloch, 1794) is a carnivorous fish species widely distributed from northern to southern South America. This taxon is believed to be a good model for the investigation of biogeographic events that shape the ichthyofauna evolution in the Neotropical freshwater systems. However, many studies have revealed that H. malabaricus hides a species complex that hampers its taxonomic identity and limit its practical value for evolutionary and biogeographic studies. In this paper, we used the mitochondrial gene cytochrome c oxidase subunit I (COI) to delimit cryptic species and explore the phylogeography of H. malabaricus sensu stricto. We found genetic evidence for putative new species in the genus Hoplias and showed that H. malabaricus (Bloch, 1794) is a major clade assigned to barcode index number (BIN) BOLD:ABZ3047. This species is structured in six subpopulations differentiated by high Fst values and restricts gene flow. The subpopulations of the São Francisco/East Atlantic/Eastern Northeast Atlantic/Parnaíba/Itapecuru River basins and Tapajós River Basin were the most differentiated and showed demographic fluctuations. The present distributional pattern is most likely explained through a scenario from the Pleistocene.

Strong and lasting impacts of past global warming on baleen whales and their prey.

Global warming is affecting the population dynamics and trophic interactions across a wide range of ecosystems and habitats. Translating these real‐time effects into their long‐term consequences remains a challenge. The rapid and extreme warming period that occurred after the Last Glacial Maximum (LGM) during the Pleistocene–Holocene transition (7–12 thousand years ago) provides an opportunity to gain insights into the long‐term responses of natural populations to periods with global warming. The effects of this post‐LGM warming period have been assessed in many terrestrial taxa, whereas insights into the impacts of rapid global warming on marine taxa remain limited, especially for megafauna. In order to understand how large‐scale climate fluctuations during the post‐LGM affected baleen whales and their prey, we conducted an extensive, large‐scale analysis of the long‐term effects of the post‐LGM warming on abundance and inter‐ocean connectivity in eight baleen whale and seven prey (fish and invertebrates) species across the Southern and the North Atlantic Ocean; two ocean basins that differ in key oceanographic features. The analysis was based upon 7032 mitochondrial DNA sequences as well as genome‐wide DNA sequence variation in 100 individuals. The estimated temporal changes in genetic diversity during the last 30,000 years indicated that most baleen whale populations underwent post‐LGM expansions in both ocean basins. The increase in baleen whale abundance during the Holocene was associated with simultaneous changes in their prey and climate. Highly correlated, synchronized and exponential increases in abundance in both baleen whales and their prey in the Southern Ocean were indicative of a dramatic increase in ocean productivity. In contrast, the demographic fluctuations observed in baleen whales and their prey in the North Atlantic Ocean were subtle, varying across taxa and time. Perhaps most important was the observation that the ocean‐wide expansions and decreases in abundance that were initiated by the post‐LGM global warming, continued for millennia after global temperatures stabilized, reflecting persistent, long‐lasting impacts of global warming on marine fauna.

Quasi-neutral evolution in populations under small demographic fluctuations

We study an eco-evolutionary dynamics in finite populations of two haploid asexually reproducing allelic types. We focus on the quasi-neutral case when individual types differ only in their intrinsic birth and death rates but have the same expected lifetime reproductive output. We assume that the population size can fluctuate stochastically. We solve the Kolmogorov forward equation in the population whose size fluctuates only minimally and show that the fixation probability is decreasing with the increasing turnover rate. We also show that when the mutant’s turnover is small enough, selection favors the mutant replacing residents. Similarly, when the turnover is high enough, selection opposes the replacement. This basic result has previously been demonstrated numerically for the contact process and shown analytically for the Moran process; the current paper extends this analysis to provide an analytical proof for the contact process. We also demonstrate numerically that our results extend for general fluctuating populations and beyond the quasi-neutral case.

Strong selection and high mutation supply characterize experimental Chlorovirus evolution.

Characterizing how viruses evolve expands our understanding of the underlying fundamental processes, such as mutation, selection and drift. One group of viruses whose evolution has not yet been extensively studied is the Phycodnaviridae, a globally abundant family of aquatic large double-stranded (ds) DNA viruses. Here we studied the evolutionary change of Paramecium bursaria chlorella virus 1 during experimental coevolution with its algal host. We used pooled genome sequencing of six independently evolved populations to characterize genomic change over five time points. Across six experimental replicates involving either strong or weak demographic fluctuations, we found single nucleotide polymorphisms (SNPs) at sixty-seven sites. The occurrence of genetic variants was highly repeatable, with just two of the SNPs found in only a single experimental replicate. Three genes A122/123R, A140/145R and A540L showed an excess of variable sites, providing new information about potential targets of selection during Chlorella–Chlorovirus coevolution. Our data indicated that the studied populations were not mutation-limited and experienced strong positive selection. Our investigation highlighted relevant processes governing the evolution of aquatic large dsDNA viruses, which ultimately contributes to a better understanding of the functioning of natural aquatic ecosystems.