Historical Mortality Dynamics on the Baja California Peninsula : Marriage, Mining Booms, Migration, and Infectious Disease.

Historical demographic research shows that the factors influencing mortality risk are labile across time and space. This is particularly true for datasets that span societal transitions. Here, we seek to understand how marriage, migration, and the local economy influenced mortality dynamics in a rapidly changing environment characterized by high in-migration and male-biased sex ratios. Mortality records were extracted from a compendium of historical vital records for the Baja California peninsula (Mexico). Our sample consists of 1,201 mortality records spanning AD 1835-1900. Findings from Cox proportional hazard models indicate that (1) marriage was associated with a protective effect for both sexes; (2) residing in a mining town was associated with higher mortality for men, but not women; (3) migration was associated with decreased mortality risk for women, but not men; and (4) the risk of mortality increased in the face of infectious disease, but decreased over time. Despite the early initiation of reproduction for women, marriage had a protective effect, likely because marriage linked women to resources. Although mining boomtowns were associated with elevated risk factors generally, only men experienced greater mortality risk, likely due to dangerous working conditions that women did not experience. Last, female, but not male, migrants experienced greater longevity, possibly because exposure to harsh labor conditions eroded the protective effect of selection bias for men. Together, these results shed light on an understudied historical population and broaden our understanding of demographic dynamics in preindustrial settings.

Nuclear and chloroplast DNA phylogeography reveals high genetic diversity and postglacial range expansion in Quercus mexicana.

PREMISE: Phylogeographical studies are fundamental for understanding factors that influence the spatial distribution of genetic lineages within species. Population expansions and contractions, distribution shifts, and climate changes are among the most important factors shaping the genetic compositions of populations. METHODS: We investigated the phylogeography of an endemic oak, Quercus mexicana (Fagaceae), which has a restricted distribution in northeastern Mexico along the Sierra Madre Oriental and adjacent areas. Nuclear and chloroplast DNA microsatellite markers were used to describe the genetic diversity and structure of 39 populations of Q. mexicana along its entire distribution area. We tested whether population expansion or contraction events influenced the genetic diversity and structure of the species. We also modeled the historical distributional range of Q. mexicana (for the Mid Holocene, the Last Glacial Maximum, and the Last Interglacial) to estimate the extent to which climate fluctuations have impacted the distribution of this oak species. RESULTS: Our results revealed high genetic diversity and low genetic structure in Q. mexicana populations. Ecological niche models suggested historical fluctuations in the distributional range of Q. mexicana. Historical range changes, gene flow, and physical barriers seem to have played an important role in shaping the phylogeographic structure of Q. mexicana. CONCLUSIONS: Our study indicates that the genetic structure of Q. mexicana may have been the result of responses of oak trees not only to heterogeneous environments present in the Sierra Madre Oriental and adjacent areas, but also to elevational and latitudinal shifts in response to climate changes in the past.

Amazonian colonization from the Atlantic Forest: New perspectives on the connections of South American tropical forests.

An open and dry vegetation belt separates Amazonia (AM) and the Atlantic Forest (AF). Evidence from palaeoclimatic and phylogenetic studies suggests past connections between these forests during cycles of increased humidity through the formation of forest corridors. The distinctive northern AF avifauna is known to have affinities both with AM and the southern AF. Still, the extent of how these two regions contributed to the assemblage of this avifauna remains poorly understood. Using historical demographic analyses and comparative phylogeography based on sub-genomic genetic sampling, we assessed how past connections between AM and AF led to shared vicariance and colonization events in four avian AF endemic taxa. Our results supported the occurrence of humid forest corridors promoting the contact between AF and AM populations and suggested two vicariant events and two colonization events from AF to AM. Population divergences were mostly non-synchronous and occurred multiple times during the Pleistocene. Historical gene flow was prevalent across study groups, supporting migration flows after the initial separation between AM and AF - a pattern previously unknown in birds between these regions. Idiosyncratic histories and divergent demographic syndromes suggest that organisms' responses to climate-driven habitat shifts broadly depend on their ecological attributes. This study strengthened our knowledge of past connections between AM and AF and provided demographic scenarios amenable for testing in other groups of co-distributed organisms.

Genetic structure and historic demography of endangered unarmoured threespine stickleback at southern latitudes signals a potential new management approach.

Habitat loss, flood control infrastructure, and drought have left most of southern California and northern Baja California's native freshwater fish near extinction, including the endangered unarmoured threespine stickleback (Gasterosteus aculeatus williamsoni). This subspecies, an unusual morph lacking the typical lateral bony plates of the G. aculeatus complex, occurs at arid southern latitudes in the eastern Pacific Ocean and survives in only three inland locations. Managers have lacked molecular data to answer basic questions about the ancestry and genetic distinctiveness of unarmoured populations. These data could be used to prioritize conservation efforts. We sampled G. aculeatus from 36 localities and used microsatellites and whole genome data to place unarmoured populations within the broader evolutionary context of G. aculeatus across southern California/northern Baja California. We identified three genetic groups with none consisting solely of unarmoured populations. Unlike G. aculeatus at northern latitudes, where Pleistocene glaciation has produced similar historical demographic profiles across populations, we found markedly different demographics depending on sampling location, with inland unarmoured populations showing steeper population declines and lower heterozygosity compared to low armoured populations in coastal lagoons. One exception involved the only high elevation population in the region, where the demography and alleles of unarmoured fish were similar to low armoured populations near the coast, exposing one of several cases of artificial translocation. Our results suggest that the current "management-by-phenotype" approach, based on lateral plates, is incidentally protecting the most imperilled populations; however, redirecting efforts toward evolutionary units, regardless of phenotype, may more effectively preserve adaptive potential.

Phylogenomics of the world's otters.

Comparative whole-genome analyses hold great power to illuminate commonalities and differences in the evolution of related species that share similar ecologies. The mustelid subfamily Lutrinae includes 13 currently recognized extant species of otters,1-5 a semiaquatic group whose evolutionary history is incompletely understood. We assembled a dataset comprising 24 genomes from all living otter species, 14 of which were newly sequenced. We used this dataset to infer phylogenetic relationships and divergence times, to characterize patterns of genome-wide genealogical discordance, and to investigate demographic history and current genomic diversity. We found that genera Lutra, Aonyx, Amblonyx, and Lutrogale form a coherent clade that should be synonymized under Lutra, simplifying the taxonomic structure of the subfamily. The poorly known tropical African Aonyx congicus and the more widespread Aonyx capensis were found to be reciprocally monophyletic (having diverged 440,000 years ago), supporting the validity of the former as a distinct species. We observed variable changes in effective population sizes over time among otters within and among continents, although several species showed similar trends of expansions and declines during the last 100,000 years. This has led to different levels of genomic diversity assessed by overall heterozygosity, genome-wide SNV density, and run of homozygosity burden. Interestingly, there were cases in which diversity metrics were consistent with the current threat status (mostly based on census size), highlighting the potential of genomic data for conservation assessment. Overall, our results shed light on otter evolutionary history and provide a framework for further in-depth comparative genomic studies targeting this group.

Dinâmica comparada: fluxos dos escravizados africanos em São Paulo, Minas Gerais e Maranhão (1804-1848) / Comparative dynamics: flows of enslaved Africans in São Paulo, Minas Gerais and Maranhão (1804-1848) / Dinámica comparada: flujos de africanos esclavizados en São Paulo, Minas Gerais y Maranhão (1804-1848)

Analisamos comparativamente informes demográficos de qualidade aceitável acerca dos escravizados nascidos na África para Minas Gerais, São Paulo e Maranhão de 1804 a 1848. As parcelas dos nascidos na África em relação aos escravizados e às razões de sexo de todos os cativos, de acordo com as idades, auxiliaram-nos a remontar a dinâmica retrospectiva da chegada dos africanos às regiões. Supondo certas hipóteses e procedimentos, a partir das coortes etárias, estimamos as proporções de africanos e as razões de sexo da população cativa para os períodos anteriores aos das listas nominativas de habitantes. A dinâmica retrospectiva da introdução de africanos reconstruída mostrou-se bastante correlacionada à história econômica das diferentes regiões estudadas.

We compare the surviving enslaved people present in demographic censuses of acceptable quality for Minas Gerais, São Paulo and Maranhão from 1804 to 1848. The share of those born in Africa in relation to slaves and the sex ratio of all captives according to their ages helped us find the retrospective dynamics of the arrival of Africans to these regions. When using age cohorts, we estimate, assuming certain hypotheses and procedures, the proportions of Africans and the sex ratios of the captive population for periods prior to those of the nominative lists of inhabitants. The retrospective dynamics of the reconstructed introduction of these Africans proved to be closely correlated with the economic history of the different regions analyzed.

Analizamos comparativamente a los sobrevivientes esclavizados presentes en los informes demográficos evaluados como de calidad aceptable para Minas Gerais, São Paulo y Maranhão entre 1804 y 1848. La proporción de los nacidos en África en relación con los esclavizados y la proporción de sexos de todos los cautivos, según las edades, nos ayudaron a trazar la dinámica retrospectiva de la llegada de africanos a estas regiones. Utilizando las cohortes de edad, estimamos, asumiendo ciertas hipótesis y procedimientos, las proporciones de africanos y las proporciones de sexos de la población cautiva para períodos anteriores a las listas nominativas de habitantes. La dinámica retrospectiva de la introducción reconstruida de africanos demostró estar altamente correlacionada con la historia económica de las diferentes regiones estudiadas.

Influence of Pleistocene climatic oscillations on the phylogeography and demographic history of endemic vulnerable trees (section Magnolia) of the Tropical Montane Cloud Forest in Mexico.

The Tropical Montane Cloud Forest (TMCF) is a highly dynamic ecosystem that has undergone frequent spatial changes in response to the interglacial-glacial cycles of the Pleistocene. These climatic fluctuations between cold and warm cycles have led to species range shifts and contractions-expansions, resulting in complex patterns of genetic structure and lineage divergence in forest tree species. In this study, we sequenced four regions of the chloroplast DNA (trnT-trnL, trnK5-matk, rpl32-trnL, trnS-trnG) for 20 populations and 96 individuals to evaluate the phylogeography, historical demography, and paleodistributions of vulnerable endemic TMCF trees in Mexico: Magnolia pedrazae (north-region), M. schiedeana (central-region), and M. schiedeana population Oaxaca (south-region). Our data recovered 49 haplotypes that showed a significant phylogeographic structure in three regions: north, central, and south. Bayesian Phylogeographic and Ecological Clustering (BPEC) analysis also supported the divergence in three lineages and highlighted the role of environmental factors (temperature and precipitation) in genetic differentiation. Our historical demography analyses revealed demographic expansions predating the Last Interglacial (LIG, ~125,000 years ago), while Approximate Bayesian Computation (ABC) simulations equally supported two contrasting demographic scenarios. The BPEC and haplotype network analyses suggested that ancestral haplotypes were geographically found in central Veracruz. Our paleodistributions modeling showed evidence of range shifts and expansions-contractions from the LIG to the present, which suggested the complex evolutionary dynamics associated to the climatic oscillations of the Pleistocene. Habitat management of remnant forest fragments where large and genetically diverse populations occur in the three TMCF regions analyzed would be key for the conservation of these magnolia populations.

The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes.

The climatic and geological changes that occurred during the Quaternary, particularly the fluctuations during the glacial and interglacial periods of the Pleistocene, shaped the population demography and geographic distribution of many species. These processes have been studied in several groups of organisms in the Northern Hemisphere, but their influence on the evolution of Neotropical montane species and ecosystems remains unclear. This study contributes to the understanding of the effect of climatic fluctuations during the late Pleistocene on the evolution of Andean mountain forests. First, we describe the nuclear and plastidic DNA patterns of genetic diversity, structure, historical demography, and landscape connectivity of Quercus humboldtii, which is a typical species in northern Andean montane forests. Then, these patterns were compared with the palynological and evolutionary hypotheses postulated for montane forests of the Colombian Andes under climatic fluctuation scenarios during the Quaternary. Our results indicated that populations of Q. humboldtii have high genetic diversity and a lack of genetic structure and that they have experienced a historical increase in connectivity from the last glacial maximum (LGM) to the present. Furthermore, our results showed a dramatic reduction in the effective population size followed by an expansion before the LGM, which is consistent with the results found by palynological studies, suggesting a change in dominance in Andean forests that may be related to ecological factors rather than climate change.

Genetic Diversity and Demographic History of the Shaggy Soft-Haired Mouse Abrothrix hirta (Cricetidae; Abrotrichini).

Genetic information on species can inform decision making regarding conservation of biodiversity since the response of organisms to changing environments depend, in part, on their genetic makeup. Territories of central-southern Chile and Argentina have undergone a varying degree of impact during the Quaternary, where the response of local fauna and flora was rather species-specific. Here, we focus on the sigmodontine rodent Abrothrix hirta, distributed from 35° S in Chile and Argentina to northern Tierra del Fuego. Based on 119,226 transcriptome-derived SNP loci from 46 individuals of A. hirta, we described the geographic distribution of the genetic diversity of this species using a maximum likelihood tree, principal component and admixture analyses. We also addressed the demographic history of the main intraspecific lineages of A. hirta using GADMA. We found that A. hirta exhibited four allopatric intraspecific lineages. Three main genetic groups were identified by a Principal Component Analysis and by Ancestry analysis. The demographic history of A. hirta was characterized by recent population stability for populations at the northernmost part of the range, while southern populations experienced a recent population expansion.

Genetic variation of the Chilean endemic long-haired mouse Abrothrix longipilis (Rodentia, Supramyomorpha, Cricetidae) in a geographical and environmental context.

Quaternary climate and associated vegetational changes affected the fauna of the Chilean Mediterranean ecosystem. Here we studied the genetic variation of the long-haired mouse, Abrothrix longipilis, a sigmodontine rodent endemic to this area. Within an environmentally explicit context, we examined the geographic distribution of the genetic diversity and demographic history of the species based on sequences of the mitochondrial Cytochrome-b gene of 50 individuals from 13 localities and a large panel of single nucleotide polymorphisms of 17 individuals from 6 localities. The gene genealogy of A. longipilis revealed three intraspecific lineages that are allopatric and latitudinally segregated (northern, central, and southern lineages) with an estimated crown age for the whole species clade of 552.3 kyr B.P. A principal component analysis based on 336,596 SNP loci is in line with the information given by the the mitochondrial gene genealogy. Along its complete distributional range, A. longipilis showed patterns of isolation by distance and also isolation by environment. The general pattern of historical demography showed stability for most intraspecific lineages of A. longipilis. Northern and central lineages showed signals of historical demographic stability, while the southern lineage showed contrasting signals. In agreement with this, the niche models performed showed that in the northern range of A. longipilis, areas of high suitability for this species increased towards the present time; areas of central range would have remained relatively stable, while southern areas would have experienced more change through time. In summary, our study shows three distinct allopatric lineages of A. longipilis, each showing slightly different demographic history.

High genetic diversity and stable Pleistocene distributional ranges in the widespread Mexican red oak Quercus castanea Née (1801) (Fagaceae).

The Mexican highlands are areas of high biological complexity where taxa of Nearctic and Neotropical origin and different population histories are found. To gain a more detailed view of the evolution of the biota in these regions, it is necessary to evaluate the effects of historical tectonic and climate events on species. Here, we analyzed the phylogeographic structure, historical demographic processes, and the contemporary period, Last Glacial Maximum (LGM) and Last Interglacial (LIG) ecological niche models of Quercus castanea, to infer the historical population dynamics of this oak distributed in the Mexican highlands. A total of 36 populations of Q. castanea were genotyped with seven chloroplast microsatellite loci in four recognized biogeographic provinces of Mexico: the Sierra Madre Occidental (western mountain range), the Central Plateau, the Trans-Mexican Volcanic Belt (TMVB, mountain range crossing central Mexico from west to east) and the Sierra Madre del Sur (SMS, southern mountain range). We obtained standard statistics of genetic diversity and structure and tested for signals of historical demographic expansions. A total of 90 haplotypes were identified, and 29 of these haplotypes were restricted to single populations. The within-population genetic diversity was high (mean h S = 0.72), and among-population genetic differentiation showed a strong phylogeographic structure (N ST = 0.630 > G ST = 0.266; p < .001). Signals of demographic expansion were identified in the TMVB and the SMS. The ecological niche models suggested a considerable percentage of stable distribution area for the species during the LGM and connectivity between the TMVB and the SMS. High genetic diversity, strong phylogeographic structure, and ecological niche models suggest in situ permanence of Q. castanea populations with large effective population sizes. The complex geological and climatic histories of the TMVB help to explain the origin and maintenance of a large proportion of the genetic diversity in this oak species.

Local persistence of Mann's soft-haired mouse Abrothrix manni (Rodentia, Sigmodontinae) during Quaternary glaciations in southern Chile.

Quaternary climatic oscillations have impacted Patagonian sigmodontine fauna, leaving traceable genetic footprints. In southern Chile, changes in the landscape included transitions to different vegetation formations as well as the extension of ice sheets. In this study, we focus on the Valdivian forest endemic and recently described sigmodontine species Abrothrix manni. We aim to assess the genetic structure of this species, testing for the existence of intraspecific lineages, and inferring the recent demographic history of the species. Analyses were based on the first 801 bp of the mitochondrial gene Cytocrhome-b from 49 individuals of A. manni collected at 10 localities that covers most part of its geographic distribution. Genealogical analyses recovered two main intraspecific lineages that are geographically segregated and present an intermediate site of secondary contact. Historical demography shows signal of recent population decrease. Based on these results, we proposed that current genetic diversity of A. manni differentiated in at least two distinct refugial areas in southern Chile. This scenario, in addition to be unique among those uncovered for the so far studied Valdivian forest rodents, is noteworthy because of the reduced geographic scale inhabited by the species.

Recent lineage diversification in a venomous snake through dispersal across the Amazon River

Identifying the evolutionary and ecological mechanisms that drive lineage diversification in the species-rich tropics is of broad interest to evolutionary biologists. Here, we use phylogeographical and demographic analyses of genome-scale RADseq data to assess the impact of a large geographical feature, the Amazon River, on lineage formation in a venomous pitviper, Bothrops atrox. We compared genetic differentiation in samples from four sites near Santarem, Brazil, that spanned the Amazon and represented major habitat types. A species delimitation analysis identified each population as a distinct evolutionary lineage while a species tree analysis with populations as taxa revealed a phylogenetic tree consistent with dispersal across the Amazon from north to south. Phylogenetic analyses of mitochondrial DNA variation confirmed this pattern and suggest that all lineages originated during the mid- to late Pleistocene. Historical demographic analyses support a population model of lineage formation through isolation between lineages with low ongoing migration between large populations and reject a model of differentiation through isolation by distance alone. The results provide a rare example of a phylogeographical pattern demonstrating dispersal over evolutionary timescales across a large tropical river and suggest a role for the Amazon River as a driver of in situ divergence both by impeding (but not preventing) gene flow and through parapatric differentiation along an ecological gradient.

Phylogeographic analyses of the pampas cat (Leopardus colocola; Carnivora, Felidae) reveal a complex demographic history

Abstract The pampas cat is a small felid that occurs in open habitats throughout much of South America. Previous studies have revealed intriguing patterns of morphological differentiation and genetic structure among its populations, as well as molecular evidence for hybridization with the closely related L. tigrinus. Here we report phylogeographic analyses encompassing most of its distribution (focusing particularly on Brazilian specimens, which had been poorly sampled in previous studies), using a novel dataset comprising 2,143 bp of the mitogenome, along with previously reported mtDNA sequences. Our data revealed strong population strutucture and supported a west-to-east colonization process in this species' history. We detected two population expansion events, one older (ca. 200 thousand years ago [kya]) in western South America and another more recent (ca. 60-50 kya) in eastern areas, coinciding with the expansion of savanna environments in Brazil. Analyses including L. tigrinus individuals bearing introgressed mtDNA from L. colocola showed a complete lack of shared haplotypes between species, indicating that their hybridization was ancient. Finally, we observed a close relationship between Brazilian/Uruguayan L. colocola haplotypes and those sampled in L. tigrinus, indicating that their hybridization was likely related to the demographic expansion of L. colocola into eastern South America.

A população do Rio Grande de São Pedro pelos mapas populacionais de 1780 a 1810 / The population of Rio Grande de São Pedro according to population maps from 1780 to 1810

O objetivo deste artigo é apresentar os resultados de um exercício metodológico explorando as potencialidades e os limites dos mapas de população relativos ao Rio Grande de São Pedro, entre finais do século XVIII e início do XIX. Essa documentação, produzida por demanda da coroa portuguesa, foi elaborada para diversas capitanias e incluía, em formato de quadro ou tabela, informações relativas à população segundo sexo, condição jurídica, idade, cor/etnia. No caso do Rio Grande de São Pedro estão disponíveis sete desses "mapas", cuja análise permite conhecer as características gerais da população dessa capitania, situada no extremo sul da América portuguesa. Nesse sentido, a partir de uma caracterização geral da documentação utilizada, buscou-se estabelecer indicadores demográficos da população naquele território na passagem do século XVIII para o século XIX, por meio das estatísticas produzidas para 1780, 1791, 1798, 1808, 1805, 1807 e 1810. Entre os resultados, destacam-se o predomínio da população branca, o desequilíbrio na razão de sexos, especialmente entre a população escrava, e a variação do peso da distribuição da população pelo território, mostrando a ocupação em direção às áreas de fronteira.

The aim of this article is to present the results of a methodological exercise exploring potentials and limitations of population maps related to Rio Grande de São Pedro, between the late eighteenth and early nineteenth centuries. This documentation, produced at request of the Portuguese crown, was prepared for several captaincies and included, in charts or tables, information on the population based on sex, legal status, age and color/ethnicity. In the case of Rio Grande de São Pedro, seven of these "maps" are available and from their analysis, it is possible to know the general characteristics of the population of Rio Grande de São Pedro, a captaincy located in the extreme south of Portuguese America. In this regard, upon a general characterization of the documentation used, demographic indicators of the population in that territory in the passage from the eighteenth century to the nineteenth century were established, through statistics produced for the years 1780, 1791, 1798, 1808, 1805, 1807 and 1810. The most significant results include a clear predominance of white population, sex ratio imbalance, especially among the slave population, and a variation in the weight of population distribution by territory, which shows occupation towards the border areas.

El objetivo de este artículo es presentar los resultados de un ejercicio metodológico que explora las potencialidades y los límites de los mapas de población relativos a Rio Grande de São Pedro entre finales del siglo XVIII y principios del XIX. Esta documentación, producida a demanda de la corona portuguesa, fue elaborada para diversas capitanías e incluía, en formato de cuadro o tabla, informaciones sobre la población en relación con sexo, condición jurídica, edad, color/etnia. En el caso de Rio Grande de São Pedro están disponibles siete de esos «mapas¼ y, a partir de su análisis, es posible conocer las características generales de la población de esta capitanía, situada en el extremo sur de la América portuguesa. En ese sentido, a partir de una caracterización general de la documentación utilizada se buscó establecer indicadores demográficos de la población en aquel territorio en el pasaje del siglo XVIII hacia el XIX, a través de las estadísticas producidas para los años 1780, 1791, 1798, 1808, 1805, 1807 y 1810. Entre los resultados, se destaca el predominio de la población blanca, el desequilibrio en la razón de los sexos, especialmente entre la población esclava, y la variación del peso de la distribución de la población en el territorio, con mayor ocupación hacia las regiones fronterizas.

High genetic connectivity and Population Expansion of Scomber japonicus in the Northern Humboldt Current System revealed by mitochondrial control region sequences

The chub mackerel, Scomber japonicus supports an important fishery in the Southeast Pacific, however, its population genetics is currently unknown. In the present study, we examined the genetic structure, the gene flow and the historical demography of this species in the Northern Humboldt Current System. Samples were collected during summer of years 2013-2014 from three fishing points (Paita, Ventanilla and Ilo), covering 12 degrees of latitude along the coast of Peru. A 532 bp segment of the mitochondrial control region was sequenced in 72 individuals, which allowed us to detect a total of 29 polymorphic sites, 35 haplotypes, moderate-to-high levels of haplotype diversity (0.793 - 0.969) and very low levels of nucleotide diversity (0.004 - 0.008). Gene flow analysis showed high levels of connectivity among populations in the sampling areas. Analysis of molecular variance (ФST = 0.00868, P = 0.1837), population pairwise ФST comparisons and genetic differentiation tests confirmed the lack of genetic structuring among the three localities. These analyses suggest that sampling sites analyzed can be considered as a single gene pool. Migratory behavior, the high dispersal potential of early stages and the lack of oceanographic barriers may explain its genetic homogeneity along the Peruvian sea. Historical demography was also examined. Neutrality tests, mismatch distribution and Bayesian skyline plot suggested a population expansion scenario that took place during the Late Pleistocene. This study provides novel information on population genetics of the chub mackerel in the Southeast Pacific.

La caballa, Scomber japonicus soporta una pesquería importante en el Pacífico Sudeste, sin embargo, su genética de poblaciones se desconoce actualmente. En el presente estudio se examinó la estructura genética, el flujo génico y la demografía histórica de esta especie en la parte norte del Sistema de la Corriente de Humboldt. Las muestras fueron colectadas en los veranos del 2013 y 2014 en tres puntos de desembarco de pesca (Paita, Ventanilla e Ilo) cubriendo 12 grados de latitud frente a la costa peruana. Se secuenció un segmento de 532 pb de la región control mitocondrial en 72 individuos, el cual permitió detectar un total de 29 sitios polimórficos, 35 haplotipos, niveles moderados altos de diversidad haplotípica (0.793 - 0.969) y muy bajos niveles de diversidad nucleotídica (0.004 - 0.008). El análisis de flujo génico mostró altos niveles de conectividad entre las poblaciones en las áreas de muestreo. El análisis de varianza molecular (ФST = 0.00868, P = 0.1837), las comparaciones ФST a pares de poblaciones y las pruebas de diferenciación genética confirmaron la carencia de estructuración genética entre las tres localidades. Estos análisis sugieren que los sitios de muestreo analizados pueden ser considerados como un solo grupo genético. El comportamiento migratorio, el alto potencial de dispersión de los estadios tempranos de desarrollo y la ausencia de barreras oceanográficas pueden explicar su homogeneidad genética a lo largo del mar peruano. También se examinó la demografía histórica. Las pruebas de neutralidad, la distribución mismatch y el Bayesian Skyline Plot sugirieron un escenario de expansión poblacional que tuvo lugar durante el Pleistoceno Superior. Este estudio provee información nueva con respecto a la genética de poblaciones de la caballa en el Pacífico Sudeste.

Phylogeographic structure of Canthon cyanellus (Coleoptera: Scarabaeidae), a Neotropical dung beetle in the Mexican Transition Zone: Insights on its origin and the impacts of Pleistocene climatic fluctuations on population dynamics.

Canthon cyanellus is a roller dung beetle with a wide distribution range in the tropical forests of the New World. In Mexico, it inhabits the Pacific and the Gulf coasts, the Yucatan Peninsula and the south mainly in the State of Chiapas. This species shows a wide geographical variation in cuticle color, which has been used as defining trait for subspecies. In this study we analyzed the phylogeographic and demographic history of the Mexican populations of C. cyanellus using DNA sequences of the nuclear ITS2, and the mitochondrial COI and 16S genes. We found that not all the current valid subspecies are supported by the molecular analysis. The populations are genetically and geographically structured in five lineages. The diversification events that gave origin to the main lineages within this species complex occurred during the Pleistocine in a time range of 1.63-0.91Myr. The demographic history of these lineages suggests post-glacial expansions toward the middle and the end of the Pleistocene. The combined data of mitochondrial and nuclear DNA suggest that the phylogeographic structure and demographic history of the C. cyanellus populations are the result of: the geological and volcanic activity that occurred from the end of the Pliocene to the Pleistocene; and the contraction and expansion of tropical forests due to the glacial and inter-glacial cycles during the Pleistocene. Landscape changes derived from historical events have affected the demographic history of the populations of this species. The results presented here point to the need to review the taxonomic status and delimitation of the lineages encompassed in the Canthon cyanellus complex.

Tropical rainforests that persisted: inferences from the Quaternary demographic history of eight tree species in the Guiana shield.

How Quaternary climatic and geological disturbances influenced the composition of Neotropical forests is hotly debated. Rainfall and temperature changes during and/or immediately after the last glacial maximum (LGM) are thought to have strongly affected the geographical distribution and local abundance of tree species. The paucity of the fossil records in Neotropical forests prevents a direct reconstruction of such processes. To describe community-level historical trends in forest composition, we turned therefore to inferential methods based on the reconstruction of past demographic changes. In particular, we modelled the history of rainforests in the eastern Guiana Shield over a timescale of several thousand generations, through the application of approximate Bayesian computation and maximum-likelihood methods to diversity data at nuclear and chloroplast loci in eight species or subspecies of rainforest trees. Depending on the species and on the method applied, we detected population contraction, expansion or stability, with a general trend in favour of stability or expansion, with changes presumably having occurred during or after the LGM. These findings suggest that Guiana Shield rainforests have globally persisted, while expanding, through the Quaternary, but that different species have experienced different demographic events, with a trend towards the increase in frequency of light-demanding, disturbance-associated species.

Evolución demográfica del Camp de Tarragona (Cataluña, España) 1570-1880: las grandes crisis de mortalidad

El Camp de Tarragona (España) participó con fuerza en la revolución comercial de la época moderna y la evolución de su población fue constante y creciente.OBJETIVO: analizar si fueron las graves crisis de mortalidad y la falta de salud lo que incentivó la evolución de la población en la zona, y el papel que estas tuvieron.MÉTODOS: con registros parroquiales y censos se construye durante casi tres siglos y medio la evolución demográfica. Se presentan aspectos significativos de la mortalidad por crisis a través del método Dupâquier y Flinn.RESULTADOS: la sequía es el indicador indirecto del stress económico y la salud. Las mayores defunciones ocurrían en años de malas cosechas, guerra o infección. Durante uno o varios años la mortalidad se elevó por encima de su nivel normal (nivel 4-5 determina graves crisis con el método Dupâquier). El Camp lo alcanzó cuatro veces: la primera vez, a principios del siglo XVII debido al factor determinante de la sequía, luego por enfermedad y las otras por guerra. Posteriormente, se dieron crisis urbanas y rurales.CONCLUSIONES: la influencia de estas graves crisis sobre el crecimiento demográfico y económico era importante cuando la capacidad del hombre era limitada. El Camp supo mantener una hegemonía demográfica y económica importante en esta época. Graves crisis de mortalidad afectaron con dureza menguando la población. Como conclusión, el papel de la mortalidad por graves crisis no es determinante, aunque estas tuvieron un papel importante en la recuperación de los habitantes del Camp.

Camp de Tarragona (Spain) participated strongly in the commercial revolution of the modern era and its population grew steadily.OBJECTIVE: to analyze whether the serious mortality crisis and lack of health stimulated the evolution of the population in the area and what role these crisis played in them.Methods: demographic change is reconstructed with parish registers and census from nearly three centuries. Significant aspects of mortality by crisis are presented through the Dupâquier and Flinn method.RESULTS: Drought is the indirect indicator of economic stress and health. Deaths increased in years of bad harvests, war or infection. For one or more years mortality rose above its normal level (level 4-5 determines serious crisis with the Dupâquier method). Camp reached this level on four times: in the early seventeenth century with drought as a determining factor, another time by disease and the other by war. It was succeeded by urban and rural crisis.CONCLUSIONS:The influence of these serious crisis on the population and economic growth was important when man's capacity was limited. The Camp was able to maintain an important demographic and economic hegemony at this time. Severe mortality crisis severely dwindled the population. As a conclusion, it is found that the role of mortality does not appear decisive for serious crisis but played an important role in the recovery momentum of the residents of Camp.

Spatial and temporal genetic homogeneity of the Monterey Spanish mackerel, Scomberomorus concolor, in the Gulf of California.

The genetic homogeneity of the Monterey Spanish mackerel Scomberomorus concolor population in the Gulf of California was confirmed using nine nuclear microsatellite loci in combination with mitochondrial cytochrome b gene sequences. Samples were collected from the upper and central Gulf areas, representing the two main biogeographical regions of the Gulf. The analyses support the existence of a single panmictic population of S. concolor inhabiting the Gulf of California which in terms of fishery management represents a single genetic stock. Additionally, the contemporary effective population size estimated for the S. concolor population (Ne = 3056.9) was high and similar to another pelagic species. The gene flow seems to be bidirectional between the upper and central Gulf, which coincides with the seasonal movements between both regions related to spawning and feeding activities. A population expansion event was detected, which agrees with a colonization-expansion hypothesis of the S. concolor population in the Gulf.