Hello, dear members!
As we’ve mentioned in one of our last posts, one of the new things LERN is bringing you this year is that every now and then we will be calling your attention to papers that we consider to be of general evolutionary interest.
In February, two papers caught our eyes:
- The PNAS paper by Kubinak et al: Experimental viral evolution to specific host MHC genotypes reveals fitness and virulence trade-offs in alternative MHC types. (http://www.pnas.org/content/109/9/3422.abstract?etoc).
A very interesting paper indeed, offering support to the leading hypothesis (Antagonistic coevolution or The Red Queen hypothesis) on how such a great diversity of polymorphisms in vertebrate MHC loci is maintained. Kubinak et al tested the Red Queen hypothesis assumptions by performing serial passage of Friend virus complex (a mouse-specific pathogen) through a series of genetically identical individuals from three MHC-congenic inbred mouse strains.
“Antagonistic coevolution predicts fitness trade-offs associated with pathogen adaptation. Adaptations that benefit pathogen fitness in one host MHC genotype must be costly to pathogen fitness when infecting hosts carrying other MHC genotypes (i.e., antagonistic pleiotropy)”.
Their results indicated a high positive correlation between increased pathogen fitness and high virulence. The adapted pathogens were also significantly more fit when infecting a familiar host genotype than when infecting an unfamiliar host genotype, conferring the necessary selective advantage to hosts carrying rare/unfamiliar MHC genotypes (confirming the assumption of the Red Queen hypothesis).
- The second one is the Proceedings of the Royal Society B paper by Schin-Ichi Fujiwara and John R. Hutchinson: Elbow joint adductor moment arm as an indicator of forelimb posture in extinct quadrupedal tetrapods. (http://rspb.royalsocietypublishing.org/content/early/2012/02/17/rspb.2012.0190.short?rss=1)
Fujiwara and Hutchinson developed a quantitative index to infer the forelimb posture of extinct quadrupedal tetrapods. Here is an extract from their paper:
“Evolutionary shifts of forelimb posture are considered to be major events in many lineages (e.g. in basal mammals, dinosaurs, archosaurs and crocodylomorphs). Reconstruction of limb orientation in any extinct taxon is important not only for reconstructing parameters relevant to their palaeoecology, such as locomotor behaviour, gait, and speed, (which might influence metabolic energy budgets and interactions with other individuals), but also for reliably estimating the timings of limb postural transitions in evolution.”
And if you are interested in evolutionary questions concerning morphology, locomotion and biomechanics, why not come to our talk next week (March 7th, see previous post for poster and details) by one of the very authors of this paper? Dr John R. Hutchinson will be joining us to discuss his ideas on ‘The evolutionary co-option of sesamoid bones for foot support in ‘six-toed’ elephants‘.We are looking forward to seeing you all next week!