Population connectivity and larval dispersal of the exploited mangrove crab Ucides cordatus along the Brazilian coast.

BACKGROUND: The mangrove crab Ucides cordatus is considered a key species for the ecological balance of mangrove forests and a major source of employment and income for traditional crab collectors in Brazil. Several studies evidenced weak genetic variation among populations due to an efficient larval transport. However, gene flow patterns of the species is poorly understood, with no information about migration rates. The influence of the two main Brazilian currents in larval dispersion is also not clear. In order to provide baseline information for conservation, planning and management of this important fishery resource, the present study aimed to estimate and evaluate spatial distribution of genetic diversity, migration rates and gene flow directivity among populations of U. cordatus in Brazil. METHODS: Nine microsatellites were used to resolve population structure of 319 crabs collected from six sites located along the Brazilian coast. The degree of geographical differentiation included estimates of genetic diversity, population structure and gene flow models, with spatial analysis of shared alleles (SAShA), isolation by distance tests, AMOVA, discriminant analysis of principal components (DAPC) and Bayesian clustering. We estimated the amount of ongoing gene flow between clusters using the coalescent-based method implemented in Migrate-N. RESULTS: Loci were highly polymorphic (average of 12.4 alleles per locus) evidencing high genetic variability. There was significant differentiation among localities, despite of the low value of FST (= 0.019; P < 0.001). FST and Jost's D indexes were also estimated in pairwise comparisons and showed significant differences between most of the surveyed site pairs (P < 0.05). Structure evidenced a single genetic group among samples, however SAShA pointed to a non-panmictic condition (P = 0.011). AMOVA detected four statistical significant clusters with low level of differentiation (FCT = 0.037; P = 0.023). The gene flow model that best described the population connectivity was the island model, with ∼24 crabs being exchanged among localities per generation. DISCUSSION: The high migration rates found among localities seem to be the main force acting to sustain the distribution of the genetic diversity of U. cordatus. Despite the high gene flow and the weak population structure among samples, the significant genetic differences found suggest that gene flow alone does not bypass the effects of genetic drift, natural selection and/or human exploitation. These findings are vital for the establishment of a database to be used in the development of conservation programs.

Migraciones en países de América Latina: Características de la población pediátrica / Migrations in Latin American countries: Characteristics of the pediatric population Abstract

Introducción: Las migraciones constituyen un fenómeno creciente en América Latina (AL), pero hay poca información sobre la magnitud en población pediátrica y asociación con variables sociodemográficas. Objetivo: Estudiar la asociación de variables sociodemográficas con la tasa de inmigración de población pediátrica en países de AL. Material y métodos: Se buscó información sobre migraciones en países de AL en: Organización Internacional para Migraciones, Organización Panamericana de la Salud y Programa de Naciones Unidas para el Desarrollo. Se efectuaron correlaciones o comparación entre países de variables económicas y demográficas: ingreso nacional bruto per cápita (INB), índice de desarrollo humano (IDH), coeficiente de desigualdad Gini (CG) y tasa de alfabetización (% adultos alfabetizados, TA), con tasa neta de migración por país (TNM) y de niños < 15 años (IN15). Resultados: La TNM fue positiva para Costa Rica, Panamá, Venezuela, Chile y Argentina. No observamos asociación entre TNM con: INB, IDH, CG y TA. Hubo una asociación de IN15 con CG (r = 0,668, p = 0,01), con INB (r = -0,720; p = 0,01), con TA (r = -0,755; p = 0,01) y con IDH (r = -0,799; p = 0,01). La IN15 fue más baja en países de AL con mayor INB vs. aquellos con menor INB (Fisher, p < 0,0001). Conclusiones: Hay una asociación inversa entre INB per cápita, IDH, TA y directa del CG, con la proporción de IN15 de cada país. No observamos una asociación entre TNM con IDH, TA, CG. Debe analizarse el impacto en salud de estas migraciones infantiles.

Introduction: Migration is a growing phenomenon among Latin American countries (LAC) as well as others; however, scarce information is available studying its impact on paediatric groups and its association with socioeconomic variables. Objective: To study the association among socioeconomic variables and the immigration rate of paediatric population in LAC. Material and methods: Official rates of migration of LAC were obtained from: International Organization for Migration, Pan American Health Organization, and United Nations Development Programme. Demographic and socioeconomic information was also obtained for: gross domestic product (GDP), human development index (HDI), Gini coefficient of inequality (GC), alphabetization rate for adults (AA), net migration rate (NMR), and immigration of children < 15 years (IM15). Description, linear correlations and analysis of differences between groups of countries were assessed. Results: The NMR was positive for Costa Rica, Panama, Venezuela, Chile and Argentina. No association among NMR and GDP, HDI, GC, AA was found. A correlation of IM15 was found with: GC (r = 0.668, P = .01), with GDP (r = -0.720; P = .01), AA (r = -0.755; P = .01) and with HDI (r = -0.799; P = .01). Rate of IM15 was lower in LA countries with advanced/medium development (GDP> median) vs those with low development (Fisher, P < .0001). Conclusions: There is a direct inverse association between GDP per capita, HDI, AA and GC and the proportion of each country IN15. We did not observe an association between NMR and HDI, AA, and GC. The health impact of these migrations should be analysed.

[Migrations in Latin American countries. Characteristics of the pediatric population]. / Migraciones en países de América Latina. Características de la población pediátrica.

INTRODUCTION: Migration is a growing phenomenon among Latin American countries (LAC) as well as others; however, scarce information is available studying its impact on paediatric groups and its association with socioeconomic variables. OBJECTIVE: To study the association among socioeconomic variables and the immigration rate of paediatric population in LAC. MATERIAL AND METHODS: Official rates of migration of LAC were obtained from: International Organization for Migration, Pan American Health Organization, and United Nations Development Programme. Demographic and socioeconomic information was also obtained for: gross domestic product (GDP), human development index (HDI), Gini coefficient of inequality (GC), alphabetization rate for adults (AA), net migration rate (NMR), and immigration of children<15 years (IM15). Description, linear correlations and analysis of differences between groups of countries were assessed. RESULTS: The NMR was positive for Costa Rica, Panama, Venezuela, Chile and Argentina. No association among NMR and GDP, HDI, GC, AA was found. A correlation of IM15 was found with: GC (r=0.668, P=.01), with GDP (r=-0.720; P=.01), AA (r=-0.755; P=.01) and with HDI (r=-0.799; P=.01). Rate of IM15 was lower in LA countries with advanced/medium development (GDP>median) vs those with low development (Fisher, P<.0001). CONCLUSIONS: There is a direct inverse association between GDP per capita, HDI, AA and GC and the proportion of each country IN15. We did not observe an association between NMR and HDI, AA, and GC. The health impact of these migrations should be analysed.

Host switching in cowbird brood parasites: how often does it occur?

Avian obligate brood parasites lay their eggs in nests of host species, which provide all parental care. Brood parasites may be host specialists, if they use one or a few host species, or host generalists, if they parasitize many hosts. Within the latter, strains of host-specific females might coexist. Although females preferentially parasitize one host, they may occasionally successfully parasitize the nest of another species. These host switching events allow the colonization of new hosts and the expansion of brood parasites into new areas. In this study, we analyse host switching in two parasitic cowbirds, the specialist screaming cowbird (Molothrus rufoaxillaris) and the generalist shiny cowbird (M. bonariensis), and compare the frequency of host switches between these species with different parasitism strategies. Contrary to expected, host switches did not occur more frequently in the generalist than in the specialist brood parasite. We also found that migration between hosts was asymmetrical in most cases and host switches towards one host were more recurrent than backwards, thus differing among hosts within the same species. This might depend on a combination of factors including the rate at which females lay eggs in nests of alternative hosts, fledging success of the chicks in this new host and their subsequent success in parasitizing it.

Geographic determinants of gene flow in two sister species of tropical Andean frogs.

Complex interactions between topographic heterogeneity, climatic and environmental gradients, and thermal niche conservatism are commonly assumed to indicate the degree of biotic diversification in montane regions. Our aim was to investigate factors that disrupt gene flow between populations and to determine if there is evidence of downslope asymmetric migration in highland frogs with wide elevational ranges and thermal niches. We determined the role of putative impediments to gene flow (as measured by least-cost path (LCP) distances, topographic complexity, and elevational range) in promoting genetic divergence between populations of 2 tropical Andean frog sister species (Dendropsophus luddeckei, N = 114; Dendropsophus labialis, N = 74) using causal modeling and multiple matrix regression. Although the effect of geographic features was species specific, elevational range and LCP distances had the strongest effect on gene flow, with mean effect sizes (Mantel r and regression coefficients ß), between 5 and 10 times greater than topographic complexity. Even though causal modeling and multiple matrix regression produced congruent results, the latter provided more information on the contribution of each geographic variable. We found moderate support for downslope migration. We conclude that the climatic heterogeneity of the landscape, the elevational distance between populations, and the inability to colonize suboptimal habitats due to thermal niche conservatism influence the magnitude of gene flow. Asymmetric migration, however, seems to be influenced by life history traits.