Histones are proteins that bind to DNA and form nucleosomes. There are several types of histones that differ in chromosome distribution and timing of their expression. In Drosophila, each canonical type histone is identical or highly similar in amino acid sequence to its corresponding replacement type histone; however, gene structure and codon usage differ between the two types of histones. Identification of the evolutionary changes responsible for the differences between these two histone types will lead to an understanding of the development of epigenetic regulation. Here, recent findings regarding codon usage for canonical and replacement types of histones are outlined for study of the evolution of these histone genes and their epigenetic regulation in Drosophila.

Genome is the nucleotide sequence of a haploid genome distributed among certain number of chromosomes. It controls the reproduction of unique features of a species. The relationship between Genome Size (GS) and Chromosome Number (CN) has been a paradox in biology partially because of the shortage in genome size records with detected chromosome number. Genome size databases provided a valuable source for this type of data allowing the study of this relationship in details. In this study, a number of 6052 genome size records with detected chromosome number were used to investigate the relationship between GS and CN and detect the location of human genome. Results showed that there is no correlation between GS and CN, yet CN is fluctuated with increasing GS values. Also, the relationship between Chromosome Number Sets (CNSs) and Average Genome Size (XGS), average Genome Size per Chromosome (GS/Ch), and the Upper Limit of Genome Size per Chromosome (ULGS/Ch) revealed lack of correlations with various degrees of fluctuation. These various types of interrelationships indicate the lack of evolutionary trend between genome size estimates and chromosome number. The human genome was located at 4/6 away from the controversial common ancestor genome and 2/6 away from the largest detected genome. Results of this study contradict the principle of Darwinian evolution from common ancestor and support the independent appearance of living organisms on earth. This will open the door for new explanations for the existence of living organisms on earth based on genome size.

Salvadora oleiodes is a tropical tree species belonging to the little-known family Salvadoraceae and distributed in the arid regions of Africa and Asia. Aims of our study were to trace the microevolutionary legacy of this tree species with the help of sequence-based multi-local phylogeography and to find the comparative placement of family Salvadoraceae within angiosperm clade malvids. A total 20 geographical isolates were collected from different regions of North India, covering a major part of its species range within the Indian Subcontinent. Sequence data from nuclear-encoded Internal Transcribed Spacer region (ITS1-5.8S-ITS2) and plastid-encoded trnL-F spacer region, were generated for this species for the first time in the world. ITS-based Bayesian phylogeographic analysis revealed the existence of four clades while trnL-F spacer based Bayesian analysis revealed one clade for this species distributed in the Indian subcontinent. Between these two loci, ITS revealed more distinct phylogeographic clades, indicating the phylogeographic utility of this locus for the systematics of Salvadoraceae. Interestingly, the ITS phylogeny indicated the existence of allopatric speciation in this tree species. Factors such as habitat destruction through agricultural expansion of plains might have forced the remaining population of this threatened tree species to isolated patches of thorn forest biotas, the ‘anthropogenic islands’, analogous to an archipelago. Phylogenetic analyzes based on trnL-F spacer suggested a synonymy of this species with Salvadora angustifolia. Maximum Likelihood gene tree based on ITS sequence data revealed that Salvadoraceae belongs to Sapindales rather than Brassicales. However, in the gene tree based on trnL-F spacer sequence, this family clustered within Brassicales. An evolutionary congruence of S. oleoides isolates across its range in North India is revealed in this study. Given the conflicting results on the relative placement of Salvadoraceae in Brassicales and Sapindales, the need for further phylogenetic analyses of malvids using supermatrix approach is highlighted.