Figure 5. Scientific Data Darlington  and Michael JD White. Hawaiian natural history, ecology, and evolution.
Proceedings of the National Academy of Sciences The nuclear genes contained many indels within coding regions, so following the removal of introns, pattern sex chromosomes karyotype in Thornton exon regions were aligned against the respective alignment of amino acid sequences using ClustalW as implemented in DAMBE 4.
The phylogenetic distribution of sex-chromosome systems Marin and Baker ; Rai and Black and the patterns of X-chromosome evolution Toups and Hahn suggest that both the common ancestor of all dipterans and the more recent common ancestor of mosquitoes had homomorphic sex chromosomes.
This allowed clusters on the same chromosome to be counted as a single orthologous comparison point but avoided ambiguous clusters where peptides were present on different chromosomes in the same species. Etges WJ, Levitan M: Paleoclimatic variation, adaptation and biogeography of inversion polymorphisms in natural populations of Drosophila robusta.
Correlated variation and population differentiation in satellite DNA abundance among lines of Drosophila melanogaster. OrthoDB v sampling the diversity of animal, plant, fungal, protist, bacterial and viral genomes for evolutionary and functional annotations of orthologs.
X chromosomes, in contrast, retain most of their ancestral genes but have evolved unique features to face their unusual challenges relative to autosomes. As the X chromosome becomes demasculinized, this eventually results in the transcriptional inactivation of the X during spermatogenesis Although the consensus topology obtained here is consistent with a single fusion of the sex chromosomes within the melanica species group, thus agreeing with the phylogeny of the melanica group initially proposed by Stalker [ 44 ], this topology was weakly supported by the analysis.
We are therefore confident that element A is indeed sex-linked in horn fly. This is consistent with the idea that dominant, male-beneficial genes are accumulating on the Z because they are being selected more often in males than females.
Under the background selection model, strongly deleterious variants are eliminated from a population in a deterministic fashion; without recombination, only chromosomes free of deleterious mutations can survive in the long run
Accelerated pseudogenization on the neo-X chromosome in Drosophila miranda. To independently confirm our results using pairwise orthology assignments, we downloaded ortholog relationships between all pairs of the species considered here from the InParanoid database Ostlund et al.
These observations are consistent with a model where, at roughly the same time as the neo-X formation, the original D. Nature : — This process leaves a signature of accumulated deleterious mutations and gene loss, acquired repetitive sequences and heterochromatinization.