Were ancient foxes far more carnivorous than recent ones?-Carnassial morphological evidence

Crown shape variation of the first lower molar in the arctic (Vulpes lagopus) and red foxes (Vulpes vulpes) was analyzed using five groups of morphotypes. Carnassial morphologies were compared between the species and between spatially and temporally distant populations: one Late Pleistocene (n = 45) and seven modern populations of the arctic fox (n = 259), and one Late Pleistocene (n = 35) and eight modern populations of the red fox (n = 606). The dentition of Holocene red foxes had larger morphotype variability than that of arctic foxes. The lower carnassials of the red fox kept have some primitive characters (additional cusps and stylids, complex shape of transverse cristid), whereas the first lower molars of the arctic fox have undergone crown shape simplification, with the occlusal part of the tooth undergoing a more pronounced adaptation to a more carnivorous diet. From the Late Pleistocene of Belgium to the present days, the arctic fox’s crown shape has been simplified and some primitive characters have disappeared. In the red fox chronological changes in the morphology of the lower carnassials were not clearly identified. The phyletic tree based on morphotype carnassial characteristics indicated the distinctiveness of both foxes: in the arctic fox line, the ancient population from Belgium and recent Greenland made separate branches, whereas in the red foxes the ancient population from Belgium was most similar to modern red foxes from Belgium and Italy.

Error propagation across levels of organization: from chemical stability of ribosomal RNA to developmental stability

My hypothesis integrates molecular and whole-organism levels of development. A physico-chemical property of nucleotides (their dipole moment), confers structural thermostability on double-stranded sequences, and decreases chemical stability of single-stranded sequences. According to this approach, low ribosomal RNA stability should decrease the precision of protein synthesis and whole-organism developmental stability. Indeed, substitution frequencies in pseudogenes are proportional to the subtraction of the dipole moment of the substituting nucleotide from that of the substituted one, and developmental instability, estimated by morphological fluctuating asymmetry (FA), correlates with mammal 12s rRNA base content of loop (but not stem) regions. In lizards, fit to the single-strand rationale of sequence chemical stability decreases with the level of poikilothermy of the investigated lizard family, suggesting interactions between changes in body temperature, ribosomal structure and developmental instability. Results confirm the hypothesis (less than for 12s rRNA) in: third codon positions of cytochrome B, probably because, unlike rRNAs, specific mRNAs affect only the protein they code; and 16s rRNA, apparently because its base composition is more affected by genome-wide mutational biases than that of 12s rRNA.

Assessing non-metric skeleton characters as a morphological tool

The appearance of non-metric skeletal characters in vertebrates results mainly from basic genetic control, as proved and documented for house mice and humans. Although the heritability of non-metric traits, mainly the presence of foramina and similar structures for blood vessels and nerves or dental occlusal variants, have been evaluated as rather low, the simultaneous consideration of several traits allows estimation of epigenetic variation in time and space as a result of genetic relationship. Thus, the main use of non-metric characters has been aimed at assessing epigenetic variability and divergence among populations. Applications extend from the problem of genetic isolation of populations, the lack of reproductive contact, detection of genetic drift, systematic studies to clarify species taxonomy, to phylogenetic interpretation. Additionally, non-directional deviations from bilateral symmetry in non-metric characters, e.g. fluctuating asymmetry, could be caused by current environmental conditions in general. Fluctuating asymmetry is regarded as a measure of developmental instability to indicate the presence of genomic changes or the influence of contamination and/or habitat deterioration, and is also used as a further population parameter with integrated information. However, standpoints on the use of fluctuating asymmetry are quite inconsistent, fluctuating themselves between considering it a powerful biomonitoring tool to being merely a curious scientific toy.