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30 results for “divergence rate”
Data from: Divergent rates of change between tree cover types in a tropical pastoral region
Context: Forest cover change analyses have revealed net forest gain in many tropical regions. While most analyses have focused solely on forest cover, trees outside forests are vital components of landscape integrity. Quantifying regional-scale patterns of tree cover change, including non-forest trees, could benefit forest and landscape restoration (FLR) efforts. Objectives: We analyzed tree cover change in Southwestern Panama to quantify: 1) patterns of change from 1998-2014, 2) differences in rates of change between forest and non-forest classes, and 3) the relative importance of social-ecological predictors of tree cover change between classes. Methods: We digitized tree cover classes, including dispersed trees, live fences, riparian forest, and forest, in very high resolution images from 1998-2014. We then applied hurdle models to relate social-ecological predictors to the probability and amount of tree cover gain. Results: All tree cover classes increased in extent, but gains were highly variable between classes. Non-forest tree cover accounted for 21% of tree cover gains, while riparian trees constituted 31% of forest cover gains. Drivers of tree cover change varied widely between classes, with opposite impacts of some social-ecological predictors on non-forest and forest cover. Conclusions: We demonstrate that key drivers of forest cover change, including topography, road distance and historical forest cover, do not explain rates of non-forest tree cover change. Consequently, predictions from medium-resolution forest cover change analyses may not apply to finer-scale patterns of tree cover. We highlight the opportunity for FLR projects to target tree cover classes adapted to local social and ecological conditions.
Linked selection, differential introgression and recombination rate variation promote heterogeneous divergence in a pair of yellow croakers
<p><span>Understanding the mechanisms underlying heterogeneous genomic divergence is of particular interest in evolutionary biology. Highly differentiated genomic regions, known as genomic islands, often evolve between diverging lineages. These genomic islands may be related to selection promoting adaptation or reproductive isolation. Based on whole genome assembly and genome-wide RAD sequencing in a pair of yellow croakers (genus: <em>Larimichthys</em>), we investigated the evolutionary processes shaping genomic landscapes of divergence. Demographic modelling indicated that the two species diverged following a secondary contact scenario, where differential introgression and linked selection were suggested to be involved in heterogeneous genomic divergence. We identified reduced recombination rate in genomic islands and a relatively good conservation of both genetic diversity and recombination landscapes between species, which highlight the roles of linked selection and recombination rate variation in promoting heterogeneous divergence in the common ancestral lineage of the two species. In addition, we found a positive correlation between differentiation (F<sub>ST</sub>) and absolute sequence divergence (<em>D</em><sub>xy</sub>), and elevated </span><span><span><em>D</em><sub>xy</sub></span> in genomic islands, which were different from the patterns under linked selection. Restricted gene flow in highly differentiated regions has likely remodeled the landscape of heterogeneous genomic divergence. Moreover, genomic islands showed little evidence of overlapping within and between species, implying that high gene flow and divergent selection when colonizing new habitats have reshaped the patterns of intraspecific divergence. This study highlights that highly differentiated genomic regions can also be from linked selection and variation of recombination rate, and thus are not necessarily related to speciation islands or local adaptation. </span></p>
Linked selection, differential introgression and recombination rate variation promote heterogeneous divergence in a pair of yellow croakers
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Data from: Divergent rates of change between tree cover types in a tropical pastoral region
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Divergent evolution of mutation rates and biases in the long-term evolution experiment with Escherichia coli
Abstract All organisms encode enzymes that replicate, maintain, pack, recombine, and repair their genetic material. For this reason, mutation rates and biases also evolve by mutation, variation, and natural selection. By examining metagenomic time series of the Lenski long-term evolution experiment (LTEE) with Escherichia coli (Good, et al. 2017), we find that local mutation rate variation has evolved during the LTEE. Each LTEE population has evolved idiosyncratic differences in their rates of point mutations, indels, and mobile element insertions, due to the fixation of various hypermutator and antimutator alleles. One LTEE population, called Ara+3, shows a strong, symmetric wave pattern in its density of point mutations, radiating from the origin of replication. This pattern is largely missing from the other LTEE populations, most of which evolved missense, indel, or structural mutations in topA, fis, and dusB— loci that all affect DNA topology. The distribution of mutations in those genes over time suggests epistasis and historical contingency in the evolution of DNA topology, which may have in turn affected local mutation rates. Overall, the replicate populations of the LTEE have largely diverged in their mutation rates and biases, even though they have adapted to identical abiotic conditions.
Data from: Intraspecific genetic structure, divergence and high rates of clonality in an amphi-Atlantic starfish
Intraspecific genetic diversity and divergence have a large influence on the adaption and evolutionary potential of species. The widely distributed starfish, Coscinasterias tenuispina, combines sexual reproduction with asexual reproduction via fission. Here we analyse the phylogeography of this starfish to reveal historical and contemporary processes driving its intraspecific genetic divergence. We further consider whether asexual reproduction is the most important method of propagation throughout the distribution range of this species. Our study included 326 individuals from 16 populations, covering most of the species' distribution range. A total of 12 nuclear microsatellite loci and sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene were analysed. COI and microsatellites were clustered in two isolated lineages: one found along the south-western Atlantic and the other along the north-eastern Atlantic and Mediterranean Sea. This suggests the existence of two different evolutionary units. Marine barriers along the European coast would be responsible for population clustering: the Almeria-Oran Front that limits the entrance of migrants from the Atlantic to the Mediterranean, and the Siculo Tunisian strait that divides the two Mediterranean basins. The presence of identical genotypes was detected in all populations, although two monoclonal populations where found in two sites where annual mean temperatures and minimum values were the lowest. Our results based on microsatellite loci showed that intra-population genetic diversity was significantly affected by clonality whereas it had lower effect for the global phylogeography of the species, although still some impact on populations' genetic divergence could be observed between some populations.
The implications of lineage-specific rates for divergence time estimation
<p>Rate variation adds considerable complexity to divergence time estimation in molecular phylogenies. Here, we evaluate the impact of lineage-specific rates—which we define as among-branch-rate-variation that acts consistently across the entire genome. We compare its impact to residual rates—defined as among-branch-rate-variation that shows a different pattern of rate variation at each sampled locus, and gene-specific rates—defined as variation in the average rate across all branches at each sampled locus. We show that lineage-specific rates lead to erroneous divergence time estimates, regardless of how many loci are sampled. Further, we show that stronger lineage-specific rates lead to increasing error. This contrasts to residual rates and gene-specific rates, where sampling more loci significantly reduces error. If divergence times are inferred in a Bayesian framework, we highlight that error caused by lineage-specific rates significantly reduces the probability that the 95% highest posterior density includes the correct value, and leads to sensitivity to the prior. Use of a more complex rate prior—which has recently been proposed to model rate variation more accurately—does not affect these conclusions. Finally, we show that the scale of lineage-specific rates used in our simulation experiments is comparable to that of an empirical data set for the angiosperm genus Ipomoea. Taken together, our findings demonstrate that lineage-specific rates cause error in divergence time estimates, and that this error is not overcome by analyzing genomic scale multilocus data sets.</p>
Data from: Geography of speciation affects rate of trait divergence in haemulid fishes
Speciation and the interactions between recently diverged species are thought to be major causes of ecological and morphological divergence in evolutionary radiations. We explored the role of these factors in the diversification of New World haemulid fishes, a major radiation of shore fishes in the tropical West Atlantic and East Pacific that are key members of coral reef ecosystems in this region. A time calibrated molecular phylogeny of this group reveals 21 sister species pairs, of which 8 are fully sympatric and 13 are allopatric. We find no difference between sympatric and allopatric pairs in the rate of divergence in color pattern, overall body shape or functional morphological traits associated with locomotion or feeding. However, sympatric pairs show a significant decrease in the rate of divergence in all of these traits with increasing time since their divergence, consistent with an elevated rate of divergence at the time of speciation, the effect of which attenuates as divergence time increases. Our results are consistent with an important role for speciation driving phenotypic divergence of haemulids, but the lack of difference in divergence between sympatric and allopatric pairs indicates that the interactions between closely related species are not dominant drivers of this divergence.
Data from: Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix
Background: Life history traits like developmental time, age and size at maturity are directly related to fitness in all organisms and play a major role in adaptive evolution and speciation processes. Comparative genomic or transcriptomic approaches to identify positively selected genes involved in species divergence can help to generate hypotheses on the driving forces behind speciation. Here we use a bottom-up approach to investigate this hypothesis by comparative analysis of orthologous transcripts of four closely related European Radix species. Results: Snails of the genus Radix occupy species specific distribution ranges with distinct climatic niches, indicating a potential for natural selection driven speciation based on ecological niche differentiation. We then inferred phylogenetic relationships among the four Radix species based on whole mt-genomes plus 23 nuclear loci. Three different tests to infer selection and changes in amino acid properties yielded a total of 134 genes with signatures of positive selection. The majority of these genes belonged to the functional gene ontology categories "reproduction" and "genitalia" with an overrepresentation of the functions "development" and "growth rate". Conclusions: We show here that Radix species divergence may be primarily enforced by selection on life history traits such as (larval-) development and growth rate. We thus hypothesise that life history differences may confer advantages under the according climate regimes, e.g., species occupying warmer and dryer habitats might have a fitness advantage with fast developing susceptible life stages, which are more tolerant to habitat desiccation.
Data from: Positive selection in development and growth rate regulation genes involved in species divergence of the genus Radix
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Data from: Geography of speciation affects rate of trait divergence in haemulid fishes
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Data from: Age specific survival rates of Steller sea lions at rookeries with divergent population trends in the Russian Far East
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Data from: Initial disturbance intensity affects recovery rates and successional divergence on abandoned ski slopes
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Data from: Intraspecific genetic structure, divergence and high rates of clonality in an amphi-Atlantic starfish
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Divergent evolution of mutation rates and biases in the long-term evolution experiment with Escherichia coli
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The implications of lineage-specific rates for divergence time estimation
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Data from: Rates of genomic divergence in humans, chimpanzees and their lice
The rate of DNA mutation and divergence is highly variable across the tree of life. However, the reasons underlying this variation are not well understood. Comparing the rates of genetic changes between hosts and parasite lineages that diverged at the same time is one way to begin to understand differences in genetic mutation and substitution rates. Such studies have indicated that the rate of genetic divergence in parasites is often faster than that of their hosts when comparing single genes. However, the variation in this relative rate of molecular evolution across different genes in the genome is unknown. We compared the rate of DNA sequence divergence between humans, chimpanzees and their ectoparasitic lice for 1534 protein-coding genes across their genomes. The rate of DNA substitution in these orthologous genes was on average 14 times faster for lice than for humans and chimpanzees. In addition, these rates were positively correlated across genes. Because this correlation only occurred for substitutions that changed the amino acid, this pattern is probably produced by similar functional constraints across the same genes in humans, chimpanzees and their ectoparasites.
Data from: Fine-Scale Mapping of Recombination Rate in Drosophila Refines its Correlation to Diversity and Divergence
Regional rates of recombination often correlate with levels of nucleotide diversity, and either selective or neutral hypotheses can explain this relationship. Regional recombination rates also correlate with nucleotide differences between human and chimpanzee, consistent with models where recombination is mutagenic; however, a lack of correlation is observed in the Drosophila melanogaster group, consistent with models invoking natural selection. Here, we revisit the relationship among recombination, diversity, and interspecies difference by generating empirical estimates of these parameters in Drosophila pseudoobscura. To measure recombination rate, we genotyped 1,294 backcross hybrids at 50 markers across the largest assembled linkage group in this species. Genome-wide diversity was estimated by sequencing a second isolate of D. pseudoobscura at shallow coverage. Alignment to the sequenced genome of the closely related species, Drosophila persimilis, provided nucleotide site orthology. Our findings demonstrate that scale is critical in determining correlates to recombination rate: fine-scale cross-over rate estimates are far stronger predictors of both diversity and interspecies difference than broad-scale estimates. The correlation of fine-scale recombination rate to diversity and interspecies difference appears to be genome-wide, evidenced by examination of an X-linked region in greater detail. Because we observe a strong correlation of cross-over rate with interspecies difference, even after correcting for segregating ancestral variation, we suggest that both mutagenic and selective forces generate these correlations, the latter in regions of low crossing over. We propose that it is not cross-overs per se that are mutagenic, but rather repair of DNA double-strand break precursors via crossing over and gene conversion.
Data from: Divergent selection on, but no genetic conflict over, female and male timing and rate of reproduction in a human population
The sexes often have different phenotypic optima for important life-history traits, and because of a largely shared genome this can lead to a conflict over trait expression. In mammals, the obligate costs of reproduction are higher for females, making reproductive timing and rate especially liable to conflict between the sexes. While studies from wild vertebrates support such sexual conflict, it remains unexplored in humans. We used a pedigreed human population from preindustrial Finland to estimate sexual conflict over age at first and last reproduction, reproductive lifespan and reproductive rate. We found that the phenotypic selection gradients differed between the sexes. We next established significant heritabilities in both sexes for all traits. All traits, except reproductive rate, showed strongly positive intersexual genetic correlations and were strongly genetically correlated with fitness in both sexes. Moreover, the genetic correlations with fitness were almost identical in men and women. For reproductive rate, the intersexual correlation and the correlation with fitness were weaker but again similar between the sexes. Thus, in this population, an apparent sexual conflict at the phenotypic level did not reflect an underlying genetic conflict over the studied reproductive traits. These findings emphasize the need for incorporating genetic perspectives into studies of human life-history evolution.
Supplementary material 1 from: Gavrilov VM, Golubeva TB, Bushuev AV (2023) Metabolic rate, sleep duration, and body temperature in evolution of mammals and birds: the influence of geological time of principal groups divergence. ZooKeys 1148: 1-27. https://doi.org/10.3897/zookeys.1148.93458
Mammalian Basal metabolic rate (BMR) dafrom Genoud et al. (2017)
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Allen Brain Atlas
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