A critique of using epitaxial criterion to discriminate between protogenetic and syngenetic mineral inclusions in diamond

Distinguishing syngenetic from protogenetic inclusions in natural diamonds is one of the most debated issues in diamond research. Were the minerals that now reside in inclusions in diamonds born before the diamond that hosts them (protogenesis)? Or did they grow simultaneously and by the same reaction (syngenesis)? Once previously published data on periclase [(Mg,Fe)O] and magnesiochromite (MgCr2O4) inclusions in diamond have been re-analysed, we show that the main arguments reported so far to support syngenesis between diamond and its mineral inclusions, definitely failed. Hence: (a) the epitaxial relationships between diamond and its mineral inclusion should no longer be used to support syngenesis, because only detecting an epitaxy does not tell us which was the nucleation substrate (there are evidences that in case of epitaxy, the inclusion acts as a nucleation substrate); (b) the morphology of the inclusion should no longer be used as well, as inclusions could be protogenetic regardless their shapes. Finally, we advance the hypothesis that the majority of inclusions in diamonds are protogenetic, e.g., they are constituent of rocks in which diamonds were formed and not products of reactions during diamond growth.

Continuity and discontinuity in evolutionary processes with emphasis on plants

The present work is aimed to review the concepts of continuity and discontinuity in the reproductive processes and their impact on the evolutionary outcome, emphasizing on the plant model. Let be stated that evolutionary changes need to pass down generation after generation through the cellular reproductive mechanisms, and these mechanisms can account for changes from single nucleotide to genome-wide mutations. Patterns of continuity and discontinuity in sexual and asexual species pose notorious differences as the involvement of the cellular genetic material from single or different individuals, the changes in the ploidy level, or the independence between nuclear and plastid genomes. One relevant aspect of the plant model is the open system for pollen donation, which can be driven from every male flower to every female flower in the neighborhood, as well as the facilitated seed dispersal patterns, that may break or restore the contact between populations. Three significative processes are distinguishable, syngenesis, anagenesis, and cladogenesis. The syngenesis refers to the reproduction between individuals, either if they pertain to the same species, from different populations or even from different species. The anagenesis refers to the pursuit of all the possible rearrangements of genes and alleles pooled in a population of individuals, and the cladogenesis represents the absence of reproduction that leads to differentiation. Recent developments on the genomic analysis of single cells, single chromosomes and fragments of homologous chromosomes could bring new insights into the processes of the evolution, in generational time and in a broad spectrum of spatial/geographic extents.