Sex chromosome evolution and gene regulation are closely linked but remain understudied in many taxa. Young neo-sex chromosomes offer unique insights into these processes. We examine dosage compensation and sex-biased gene expression in Vandiemenella viatica grasshoppers by comparing the ancestral X chromosome in the P24X0 race with derived neo-sex chromosomes in the P24XY race. The P24XY neo-XY arose via X-autosome fusion: the XL arm represents the ancestral X and the XR arm a former autosome (chromosome 1 in P24X0) now part of the neo-X and homologous to the neo-Y. We first assess dosage compensation via male and female gene expression. In somatic tissues, male P24X0 X-linked and P24XY XL-linked genes are upregulated to match both female expression and autosomal levels, indicating near-complete dosage compensation. In testes, expression of X-linked and the XL-linked genes is reduced nearly 4-fold reflecting absent dosage compensation and the presence of meiotic X chromosome inactivation. We then analyze sex-biased gene expression across tissues and chromosomes. Gonads show stronger sex-biased gene expression than somatic tissues. Female-biased genes are concentrated on the P24X0 X and P24XY XL, whereas male-biased genes are enriched on autosomes and the XR arm of the neo-X. Overall, the ancestral X in P24X0 and the XL arm of the P24XY neo-X are hypertranscribed, while the XR arm retains autosomal expression, male-biased enrichment, and lacks dosage compensation. These patterns show that dosage compensation is regulated at levels of chromosome arms and illustrate how chromosome structure, gene regulation, and reproduction interact, shedding light on sex chromosome evolution in V. viatica.

Satellite DNAs (satDNAs), ubiquitous sequences in eukaryotic genomes, play a crucial role in genome organization, function, and evolution. The pea aphid Acyrthosiphon pisum is a major crop pest, and an emerging model for ecological, developmental, and evolutionary studies. This study characterizes the satellitome of the A. pisum to better understand its genomic organization and the evolutionary dynamics of satDNAs at the intraspecies level. The analysis of satDNAs across various host-plant adapted biotypes reveals a general sharing of the satellitome, with significative quantitative differences. We observe the amplification or contraction of specific satDNA families, even in the same biotype, consistent with the fast-evolutionary changes characteristic of these sequences. Rapid differential accumulation of repetitive elements among biotypes together with other factors may contribute to the origin of genetic incompatibilities. At the interspecific level, fluctuations in satDNA abundances, including the loss of certain families, are consistent with the library hypothesis, long-term conservation, and differential amplification of an ancestral satellitome. SatDNAs are considerably enriched in the heterochromatin of the chromosome X (Chr-X) and to a less extent, dispersed across the euchromatic region of all chromosomes. The enrichment of these sequences on Chr-X also features the elements that are most recently amplified and homogenized. This suggests that Chr-X could serve as a fountain of youth for satDNAs, contributing to the "fast-X" effect. Our findings provide valuable insights into genome structure, assembly, and the potential impact of satDNAs on species diversification, as well as the evolution of autosomes and Chr-X.

Grasshoppers represent true outliers in genome sizes, both within insects and within animals in general. Their genomes are large and generally variable in sizes and feature a high abundance of repetitive DNA sequences. This has hampered the assembly of grasshopper genomes to the chromosome level. Here we present a chromosome-level reference genome for the club-legged grasshopper (Gomphocerus sibiricus, Acrididae: Gomphocerinae) using PacBio HiFi long-read and Hi-C sequencing technologies. In male haploid cells, the species has a chromosome set of n = 9 with an X0 sex-determination system, characterized by an absence of a Y chromosome. Our assembly spans 9.57 Gb in total, with 8.87 Gb organized into 9 chromosomes-8 autosomes and the X chromosome. The final assembly has a scaffold N50 value of 1.58 Gb, covers 96.7% single copy Insecta orthologs, and contains 42,665 predicted protein-coding genes and 43,385 mRNA transcripts. We compiled a curated, nonredundant, species-specific repeat library and used it to annotate repetitive DNA, covering 81.69% of the genome, mostly DNA transposons, long-interspersed nuclear element and long-terminal repeat retrotransposons. The genome of the club-legged grasshopper shows high degree of synteny with the locusts Schistocerca gregaria and Locusta migratoria, and the analysis strongly indicates 3 autosome-autosome centric fusions in Gomphocerinae. The genome offers a valuable resource for grasshopper genomics and for exploring the genetic basis of a transspecies color polymorphism.

The green-brown polymorphism in Orthoptera is a prominent example of the coexistence of multiple colour variants, especially since this polymorphism is shared by many species. The processes that maintain phenotypic polymorphisms depend on the underlying genetic and developmental regulation of body colouration, but these are not well understood for Orthoptera. Here we report on the inheritance of the green-brown polymorphism in the meadow grasshopper Pseudochorthippus parallelus, a species with four discrete colour morphs that differ in the distribution of green colouration across the body. We provide the most detailed analysis of the green-brown polymorphism to date using half-sib full-sib breeding and phenotyping of 4,300 offspring. The data strongly support a simple Mendelian control of the presence/absence of green colour in different regions of the body, involving four autosomal loci, two of which are genetically linked. However, estimation of population allele and haplotype frequencies using probabilistic simulations shows weak linkage disequilibrium in the population. The contrast between pedigree and population linkage suggests the presence of long-standing allelic variation and thus corroborates that long-term balancing selection is acting. Our study confirms and extends our understanding of inheritance patterns within the Chorthippus clade, providing unprecedented insights into the number and linkage of loci involved. The results have implications for the maintenance of polymorphisms and suggest that fluctuations in the phenotypic composition of populations can be generated by the segregation of genetic variants even in the absence of fluctuating selection.

Orthoptera provide a well-documented case of transspecies colour polymorphism, with green and brown morphs coexisting in many species. This colour polymorphism is likely under long-term balancing selection, but the genetic and molecular mechanisms underlying the variation remain poorly understood. Here, we used transcriptome data alongside a novel chromosome-level assembly to perform differential gene expression analysis in the club-legged grasshopper Gomphocerus sibiricus (Caelifera: Acrididae: Gomphocerinae), aiming to identify the specific genes involved in the differentiation between green and brown morphs. Since differential expression analyses are prone to false positives, we replicated the analysis using an independent sample of individuals of the same species. We found six genes consistently upregulated in green individuals across both datasets, all annotated as beta-carotene-binding proteins (βCBPs). βCBPs are known to play a key role in the colour regulation in both the migratory locust Locusta migratoria and the desert locust Schistocerca gregaria , although their exact role may differ in the club-legged grasshopper. The gene tree and chromosomal positions of βCBP copies in G. sibiricus , L. migratoria and S. gregaria indicate both ancestral (pre-speciation) and lineage-specific duplications. Our screening of publicly available orthopteran genomes revealed that homologues of the βCBP genes are largely absent from non-Caelifera species when using conservative homology thresholds. This restricted distribution suggests that βCBP-mediated pigmentation may represent a Caelifera-specific mechanism that is involved in the production of green body coloration, while other orthopteran lineages likely rely on distinct genetic pathways. Together, our findings provide new insights and lay the groundwork for understanding the evolutionary diversification of pigmentation mechanisms in Orthoptera.

Like other eukaryotes, insect genomes contain a large portion of repetitive sequences, particularly transposable elements and satellite DNAs. This review highlights key studies on repetitive DNAs and examines their structural, functional, and evolutionary impact on insect genomes. Repetitive sequences promote genetic diversification through mutations and large-scale rearrangements, playing a crucial role in shaping genomic architecture, aiding organismal adaptation, and driving speciation. We also explore the influence of repeats in genome size variation and species incompatibilities, along with their contribution to adaptive phenotypes and gene regulation. Studying repetitive DNA in insects not only provides insights into basic genomic features but also offers valuable information for conservation strategies, pest control, and advancements in genetics, ecology, and evolutionary biology.

Genomic repetitive DNA sequences (Repeatomes, REPs) are widespread in eukaryotes, influencing biological form and function. In Cnidaria, an early-diverging animal lineage, these sequences remain largely uncharacterized. This study investigates sea anemone REPs (Cnidaria: Actiniaria) in a phylogenetic context. We sequenced and assembled de novo the genome of Actinostella flosculifera and analyzed a total of 38 nuclear genomes to create the first ActiniariaREP library (Actiniaria-REPlib). We compared Actiniaria-REPlib with Repbase and RepeatModeler2 libraries, and used dnaPipeTE to annotate REPs from genomic short-read datasets of 36 species for divergence landscapes. Our study assembled and annotated the mitochondrial genomes, including 27 newly assembled ones. We re-annotated 92

Bird genomes are among the most stable in terms of synteny and gene content across vertebrates. However, germline-restricted chromosomes (GRCs) represent a striking exception where programmed DNA elimination confines large-scale genomic changes to the germline. GRCs are known to occur in songbirds (oscines), but have been studied only in a few species of Passerides such as the zebra finch, the key model for passerine genomics. Their presence and evolutionary dynamics in most major passerine lineages remain largely unexplored, with suboscines entirely unexamined by cytogenetic or genomic methods. Here, we present the most comprehensive comparative analysis of GRCs to date, spanning 44 million years of passerine evolution. By generating the first germline reference genomes of an oscine and a suboscine, 22 novel germline draft genomes spanning nearly all major passerine lineages and a germline draft genome of a parrot outgroup, we show that the GRC is likely present in 6,700 passerine species. Our results reveal that the GRC evolves rapidly and distinctly from the standard A chromosomes (autosomes and sex chromosomes), yet retains functionally important, selectively maintained genes. We observed gene and repeat turnover occuring orders of magnitude faster than on the A chromosomes. Some GRC genes, such as cpeb1 and pim1, are widespread from an ancient duplication. In contrast, other GRC genes, like mfsd2b and bmp15, have been independently duplicated onto the GRC multiple times, suggesting adaptive constraints. The discovery of zglp1 on the zebra finch GRC, initially copied from chromosome 30 and subsequently lost from it, indicates functional replacement, where the GRC permits gene loss from the standard genome. As the GRC harbors the only zglp1 copy in most of the ~4000 Passerides species, GRC loss would compromise essential germline functions. Our findings establish the GRC as a genomic innovator driving rapid germline evolution. This fact highlights its evolutionary significance for passerine diversification and suggests that programmed DNA elimination may be an overlooked yet phylogenetically widespread mechanism in many understudied animal lineages.

Karyotype evolution might fuel speciation and can thereby contribute to species diversity. To test the hypothesis that speciation and karyotype change are linked, we estimated anagenetic and cladogenetic rates of karyotype evolution as well as speciation rates in Orthoptera. We compiled the male diploid chromosome number and the number of visible chromosome arms (the fundamental number) from published sources for 1,541 species. Chromosome-associated speciation rates were estimated by jointly modelling cladogenetic and anagenetic character evolution and the phylogenetic birth-death process in a Bayesian statistical framework using a subset of 516 species from 14 families. Our findings unveiled heterogeneity among orthopteran families in the pace of karyotype evolution and whether it was linked to speciation. In 6/14 clades, we found evidence supporting speciation-associated (cladogenetic) karyotype changes, while in 6/14 clades karyotype evolution was primarily anagenetic. The remaining clades (2/14) showed uncertainty in favour of either model. We further analyzed whether flightless phenotype, and thus less mobile species, showed higher rates of karyotype evolution. We showed that the flightless phenotype is associated with the rate of chromosome loss. The finding indicates contrasting patterns of karyotype evolution within specific orthopteran lineages, thus emphasizing substantial diversity in the pace of this evolutionary process. It also implies that substantial changes in chromosome number, arising from instances of chromosomal gains and losses, are recurring events in orthopterans that are associated with reproductive isolation and speciation, at least in some groups.

Morabine grasshoppers in the Vandiemenella viatica species group, which show karyotype diversity, have been studied for their ecological distribution and speciation in relation to their genetic and chromosomal diversity. They are good models for studying sex chromosome evolution as “old” and newly emerged sex chromosomes co-exist within the group. Here we present a reference genome for the viatica19 chromosomal race, that possesses the ancestral karyotype within the group. Using PacBio HiFi and Hi-C sequencing, we generated a chromosome-level assembly of 4.09 Gb in span, scaffold N50 of 429 Mb, and complete BUSCO score of 98.1%, containing 10 pseudo-chromosomes. We provide Illumina datasets of males and females, used to identify the X chromosome. The assembly contains 19,034 predicted protein-coding genes, and a total of 75.21% of repetitive DNA sequences. By leveraging HiFi reads, we mapped the genome-wide distribution of methylated bases (5mC and 6 mA). This comprehensive assembly offers a robust reference for morabine grasshoppers and supports further research into speciation and sex chromosome diversification within the group and its related species.

The early evolution of sex chromosomes has remained obscure for more than a century. The Vandiemenella viatica species group of morabine grasshoppers is highly suited for studying the early stages of sex chromosome divergence and degeneration of the Y chromosome. This stems from the fact that neo-XY sex chromosomes have independently evolved multiple times by X-autosome fusions with different autosomes. Here, we generated new chromosome-level assemblies for two chromosomal races representing karyotypes with and without neo-sex chromosomes (P24XY and P24X0), and sequence data of a third chromosomal race with a different neo-XY chromosome system (P25XY). Interestingly, these two neo-XY chromosomal races are formed by different X-autosome fusions (involving chr1 and chrB, respectively), and we found that both neo-Y chromosomes have partly ceased to recombine with their neo-X counterpart. We show that the neo-XY chromosomes have diverged through accumulation of SNPs and structural mutations, and that many neo-Y-linked genes have degenerated since recombination ceased. However, the non-recombining regions of neo-Y chromosomes host non-degenerated genes crucial for sex determination, such as sex-lethal and transformer, alongside genes associated with spermatogenesis, fertility, and reproduction, illustrating their integrative role as a masculinizing supergene. Contrary to expectations, the neo-Y chromosomes showed (slightly) lower density of transposable elements (TEs) compared to other genomic regions. The study reveals the unique dynamics of young sex chromosomes, with evolution of recombination suppression and pronounced decay of (some) neo-sex chromosome genes, and provides a compelling case illustrating how chromosomal fusions and post-fusion mutational processes contribute to the evolution of supergenes.

Grasshoppers in the genus Ronderosia (divergence time < 5 Mya) provide a special opportunity to examine the impact of chromosome rearrangements (CRs) in evolution and speciation, because they exhibit extensively rearranged karyotypes involving autosome-autosome and autosome-X chromosomes, the latter leading to the formation of a neo-sex chromosome system (neo-SCS). Despite the potential role of CRs in speciation, the general patterns of karyotype changes resulting from CRs in Ronderosia are still unclear. Here we investigated karyotype evolution in eight Ronderosia species using cytogenetic and phylogenetic models of ancestral character reconstruction. The overall findings suggest a central role for CRs in generating variability in chromosome number and neo-SCS across Ronderosia grasshoppers. It also suggests that incipient species with little morphological change, such as those observed in Ronderosia species, could accumulate marked differences in their karyotypes contributing to post-zygotic reproductive isolation. Besides the evolution of chromosome number in the phylogeny of the genus, chromosome change due to centric fusion is coupled with the divergence pattern observed in the group. While a cladogenetic event could represent a case where karyotypic differences result in speciation, further in-depth genomic studies are needed to better understand how these dramatic restructurings of karyotypes may have occurred.

Pervasive convergent evolution and in part high incidences of hybridization distinguish wheatears (songbirds of the genus Oenanthe) as a versatile system to address questions at the forefront of research on the molecular bases of phenotypic and species diversification. To prepare the genomic resources for this venture, we here generated and annotated a chromosome-scale assembly of the Eastern black-eared wheatear (Oenanthe melanoleuca). This species is part of the Oenanthe hispanica complex that is characterized by convergent evolution of plumage coloration and high rates of hybridization. The long-read-based male nuclear genome assembly comprises 1.04 Gb in 32 autosomes, the Z chromosome, and the mitogenome. The assembly is highly contiguous (contig N50, 12.6 Mb; scaffold N50, 70 Mb), with 96% of the genome assembled at the chromosome level and 95.5% benchmarking universal single-copy orthologs (BUSCO) completeness. The nuclear genome was annotated with 18,143 protein-coding genes and 31,333 mRNAs (annotation BUSCO completeness, 98.0%), and about 10% of the genome consists of repetitive DNA. The annotated chromosome-scale reference genome of Eastern black-eared wheatear provides a crucial resource for research into the genomics of adaptation and speciation in an intriguing group of passerines.

To test the hypothesis that high speciation rate in groups is coupled with high rate of karyotype evolution but also that younger groups having a higher rate of karyotypic diversity, I estimated rates of speciation and rates of karyotype evolution in 1,177 species belonging to 26 families in the insect order Orthoptera. Rates of karyotype evolution were estimated using the diploid number and the number of chromosome arms (fundamental number) from published karyotypes of Orthoptera. Rates of speciation were quantified considering the number of species examined karyotypically in each family, the most recent common ancestor of each family and the information about extinction rate. The rate of speciation was strongly correlated with rate of karyotype evolution and the average rates of speciation was nearly ~177 times higher than the background rate estimated for Orthoptera based on acoustic communication using phylogenomic data, as well as 8.4 and 35.6 times higher than the estimated speciation rate in vertebrates and bivalve mollusks respectively, indicating that Orthoptera has evolved very fast at chromosomal level. The findings supported the hypothesis of a high speciation rate in lineages with high rate of chromosomal evolution but there were not evidences that younger groups tended to have higher rate of karyotypic diversity. Furthermore, rates of karyotype evolution most closely fitted the punctuational evolutionary model indicating the existence of long periods of stasis of karyotype change with most karyotype change occurring quickly over short evolutionary times. I discussed genetic drift, divergent selection and meiotic drive as potential biological mechanisms to explain karyotype evolution allowing or impeding for the fixation of chromosomal rearrangements and in turn speciation in orthopterans lineages.

It is a broadly observed pattern that the non-recombining regions of sex-limited chromosomes (Y and W) accumulate more repeats than the rest of the genome, even in species like birds with a low genome-wide repeat content. Here, we show that in birds with highly heteromorphic sex chromosomes, the W chromosome has a transposable element (TE) density of greater than 55% compared to the genome-wide density of less than 10%, and contains over half of all full-length (thus potentially active) endogenous retroviruses (ERVs) of the entire genome. Using RNA-seq and protein mass spectrometry data, we were able to detect signatures of female-specific ERV expression. We hypothesize that the avian W chromosome acts as a refugium for active ERVs, probably leading to female-biased mutational load that may influence female physiology similar to the 'toxic-Y' effect in Drosophila males. Furthermore, Haldane's rule predicts that the heterogametic sex has reduced fertility in hybrids. We propose that the excess of W-linked active ERVs over the rest of the genome may be an additional explanatory variable for Haldane's rule, with consequences for genetic incompatibilities between species through TE/repressor mismatches in hybrids. Together, our results suggest that the sequence content of female-specific W chromosomes can have effects far beyond sex determination and gene dosage. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.

Given their copy number differences and unique modes of inheritance, the evolved gene content and expression of sex chromosomes is unusual. In many organisms the X and Y chromosomes are inactivated in spermatocytes, possibly as a defense mechanism against insertions into unpaired chromatin. In addition to current sex chromosomes, Drosophila has a small gene-poor X-chromosome relic (4th) that re-acquired autosomal status. Here we use single cell RNA-Seq on fly larvae to demonstrate that the single X and pair of 4th chromosomes are specifically inactivated in primary spermatocytes, based on measuring all genes or a set of broadly expressed genes in testis we identified. In contrast, genes on the single Y chromosome become maximally active in primary spermatocytes. Reduced X transcript levels are due to failed activation of RNA-Polymerase-II by phosphorylation of Serine 2 and 5.

In Acridoidea grasshoppers, chromosomal rearrangements are frequently found as deviations from the standard acrocentric karyotype (2n = 23♂/24♀, FN = 23♂/24♀) in either phylogenetically unrelated species or shared by closely related ones, i.e. genus. In the South American subfamily Ommexechinae, most of the species show a unique karyotype (2n = 23♂/24♀, FN = 25♂/26♀) owing to the occurrence of a large autosomal pair (L1) with submetacentric morphology. In the early 1960s, Alejo Mesa proposed the hypothesis of an ancestral pericentric inversion to explain this karyotype variation. Furthermore, in Ommexechinae, extra chromosomal rearrangements (e.g. centric fusions) are recorded between the ancestral X chromosome and autosomes that originated the so-called neo-sex chromosomes. However, the evolutionary significance of the pericentric inversions and centric fusions in Ommexechinae remains poorly explored. Aiming for a better understanding of chromosomal evolution in Ommexechinae, we performed a detailed cytogenetic analysis in five species. Our findings support the hypothesis about the occurrence of an early pericentric inversion in the ancestor of Ommexechinae. Moreover, our results show a complex karyotype diversification pattern due to several chromosome rearrangements, variations in heterochromatin and repetitive DNA dynamics. Finally, the chromosomal mapping of U2 snDNA in L1 provided new insights about the morphological evolution of this autosomal pair and revealed unnoticed chromosome reorganizations.

Multigene families are essential components of eukaryotic genomes and play key roles either structurally and functionally. Their modes of evolution remain elusive even in the era of genomics, because multiple multigene family sequences coexist in genomes, particularly in large repetitive genomes. Here, we investigate how the multigene families 18S rDNA, U2 snDNA, and H3 histone evolved in 10 species of Schistocerca grasshoppers with very large and repeat-enriched genomes. Using sequenced genomes and fluorescence in situ hybridization mapping, we find substantial differences between species, including the number of chromosomal clusters, changes in sequence abundance and nucleotide composition, pseudogenization, and association with transposable elements (TEs). The intragenomic analysis of Schistocerca gregaria using long-read sequencing and genome assembly unveils conservation for H3 histone and recurrent pseudogenization for 18S rDNA and U2 snDNA, likely promoted by association with TEs and sequence truncation. Remarkably, TEs were frequently associated with truncated copies, were also among the most abundant in the genome, and revealed signatures of recent activity. Our findings suggest a combined effect of concerted and birth-and-death models driving the evolution of multigene families in Schistocerca over the last 8 million years, and the occurrence of intra- and interchromosomal rearrangements shaping their chromosomal distribution. Despite the conserved karyotype in Schistocerca, our analysis highlights the extensive reorganization of repetitive DNAs in Schistocerca, contributing to the advance of comparative genomics for this important grasshopper genus.

A common characteristic of sex chromosomes is the accumulation of repetitive DNA, which accounts for their diversification and degeneration. In grasshoppers, the X0 sex-determining system in males is considered ancestral. However, in some species, derived variants like neo-XY in males evolved several times independently by Robertsonian translocation. This is the case of Ronderosia bergii, in which further large pericentromeric inversion in the neo-Y also took place, making this species particularly interesting for investigating sex chromosome evolution. Here, we characterized the satellite DNAs (satDNAs) and transposable elements (TEs) of the species to investigate the quantitative differences in repeat composition between male and female genomes putatively associated with sex chromosomes. We found a total of 53 satDNA families and 56 families of TEs. The satDNAs were 13.5% more abundant in males than in females, while TEs were just 1.02% more abundant in females. These results imply differential amplification of satDNAs on neo-Y chromosome and a minor role of TEs in sex chromosome differentiation. We showed highly differentiated neo-XY sex chromosomes owing to major amplification of satDNAs in neo-Y. Furthermore, chromosomal mapping of satDNAs suggests high turnover of neo-sex chromosomes in R. bergii at the intrapopulation level, caused by multiple paracentric inversions, amplifications, and transpositions. Finally, the species is an example of the action of repetitive DNAs in the generation of variability for sex chromosomes after the suppression of recombination, and helps understand sex chromosome evolution at the intrapopulation level.

Satellite DNA (satDNA) is an abundant class of tandemly repeated noncoding sequences, showing high rate of change in sequence, abundance, and physical location. However, the mechanisms promoting these changes are still controversial. The library model was put forward to explain the conservation of some satDNAs for long periods, predicting that related species share a common collection of satDNAs, which mostly experience quantitative changes. Here, we tested the library model by analyzing three satDNAs in ten species of Schistocerca grasshoppers. This group represents a valuable material because it diversified during the last 7.9 Myr across the American continent from the African desert locust (Schistocerca gregaria), and this thus illuminates the direction of evolutionary changes. By combining bioinformatic and cytogenetic, we tested whether these three satDNA families found in S. gregaria are also present in nine American species, and whether differential gains and/or losses have occurred in the lineages. We found that the three satDNAs are present in all species but display remarkable interspecies differences in their abundance and sequences while being highly consistent with genus phylogeny. The number of chromosomal loci where satDNA is present was also consistent with phylogeny for two satDNA families but not for the other. Our results suggest eminently chance events for satDNA evolution. Several evolutionary trends clearly imply either massive amplifications or contractions, thus closely fitting the library model prediction that changes are mostly quantitative. Finally, we found that satDNA amplifications or contractions may influence the evolution of monomer consensus sequences and by chance playing a major role in driftlike dynamics.