The tropics are the source of most biodiversity yet inadequate sampling obscures answers to fundamental questions about how this diversity evolves. We leveraged samples assembled over decades of fieldwork to study diversification of the largest tropical bird radiation, the suboscine passerines. Our phylogeny, estimated using data from 2389 genomic regions in 1940 individuals of 1287 species, reveals that peak suboscine species diversity in the Neotropics is not associated with high recent speciation rates but rather with the gradual accumulation of species over time. Paradoxically, the highest speciation rates are in lineages from regions with low species diversity, which are generally cold, dry, unstable environments. Our results reveal a model in which species are forming faster in environmental extremes but have accumulated in moderate environments to form tropical biodiversity hotspots.
The answers to the questions are: (a) yes; and (b) an initial moderate bottleneck, intensified by more recent historical events (isolation and inbreeding), can explain the current Amerindian pattern of diversity.
A total of 91 Ayoreo individuals previously studied for blood groups and protein markers, living in two Bolivian and one Paraguayan communities, were extensively investigated in relation to the hypervariable 1 segment of the control and eight coding regions of their mitochondrial DNA (mtDNA). They show an extremely reduced mtDNA variability, the observed haplotypes being classifiable in just two haplogroups (C and D). They were also variously studied in relation to six Alu insertions; in this case, however, the prevalences found did not depart markedly from those obtained in other populations of this ethnic group. To assess the Ayoreo position in relation to these populations, 11 other groups that had also been studied for these systems and for blood groups and proteins were selected. The dendrograms obtained with two of the three sets of markers showed distinct patterns, but the Ayoreo were placed in a central position in both the blood group + proteins and Alu insertions trees. Therefore, they are clearly distinct in relation to their mtDNA only, suggesting a strong founder effect and/or random loss of variability in this system.
The answer to the first question posed above is affirmative. However, the problem of whether the Aché derived from a Gê group that preceded the Guarani colonization of Paraguay, or are just a differentiated Guarani group, could not be answered with the genetic information available; the second hypothesis seems more likely at present, but the point to be emphasized is the striking genetic distinctiveness of the Aché as compared to other Amerindians.
Most Neotropical colubrid snakes belong to a single, well‐supported lineage. Relationships between the major constituents of this clade remain. Here, we explore the phylogenetic relationships of Mastigodryas and its affinities to other Neotropical colubrid genera by combining DNA and morphological data. Analyses demonstrate that the concatenation of multiple individuals into a single terminal can mask the detection of new taxa. Further, non‐random missing data and/or taxa in some empirical datasets can bias species tree analyses more than concatenation approaches. Our results place Mastigodryas in a strongly supported clade that includes Drymarchon, Rhinobothryum, Drymoluber, Simophis and Leptodrymus. Mastigodryas bifossatus is more closely related to species of Drymoluber and Simophis than to its congeners. Thus, we erect a new genus to accommodate it and recover a monophyletic Mastigodryas. We highlight the importance of the use of morphological characters to diagnose suprageneric clades by showing that some key external and hemipenial characteristics are phylogenetically informative.
The objectives of this study were to understand how genotype, storage time, and storage conditions affect cooking time of beans and to indicate storage techniques that do not affect the cooking time. The grains were subjected to five different storage periods and six different storage conditions. The cooking time was estimated using the Mattson Cooker. The data were subjected to analysis of variance and a subsequent adjustment of simple linear regression for deployment of the interactions between the factors. Contrasts were used to determine the best levels of the factor storage condition. Genotype did not impact cooking time when the storage time and storage conditions were considered. Time and storage conditions affect the cooking time of beans in a dependent manner, but time of storage had the biggest influence. The best conditions for long-term storage of beans ensuring a smaller increase in cooking time is plastic storage at low temperatures. Thus, plastic freezer storage is a practical alternative for consumers.
SummaryA total of 1558 base pairs in the 16p13.3 region were investigated in 98 individuals of Mongolian, Northern Arctic and Amerindian affiliation, and the results compared with those obtained in a previous worldwide study of the same genomic region. Fifty-five polymorphic sites could be classified into thirty-five haplotypes from the total data. A median joining network based on the haplotypes revealed two distinct clusters: one with low diversity, with haplotypes found in all five geographic-ethnic categories; while the other, with the most divergent haplotypes, was composed mainly of Africans and a few Amerindians. Almost all neutrality parameters yielded significantly negative values. Demographic simulations with the exclusively Amerindian dataset rejected all scenarios, including a bottleneck beginning more than 12,000 years ago. The demographic scenarios tested considering population growth were similar among the Amerindian and worldwide or Eurasian data sets. The results suggest that Amerindians are a representative sample of Eurasian populations, preserving the signal of demographic growth from the out of Africa exodus and, together with data from uniparental markers, support a scenario of a bottleneck of moderate intensity during the peopling of the New World.
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