A new paper in Current Zoology written in collaboration with Italian colleagues, and particularly Paolo Franchini (University of Konstanz) is finally out in its “advance access” version. The paper is part of a special column of the journal on “De-mystifying the Tangled Bank: Motors and Brakes of Phenotypic Evolution“.
The paper stems from a long-term collaboration (and in fact has been several years in the making) and addresses the question of what is the effect of chromosomal evolution on phenotypic integration using geometric morphometric analysis of mandibles in house mouse from a parapatric contact zone. This contact zone is in central Italy and comprises the normal standard race (diploid number 40), a highly derived chromosomal race (diploid number 22) and several “hybrids” with intermediate karyotypes between the two.
We test several hypotheses including whether there is a clear gradual trend of departure from “normal” patterns of integration as Robertsonian fusions accumulate. Above, you can see an unpublished figure which is a composite of some of the results in the paper.
Among other things, we find that:
1. the patterns of integration are indeed different between the two main races, but the strength of integration is similar;
2. (static) allometry (with the two main races having different allometric trajectories) is the main factor driving patterns of integration (see part B of figure above);
3. there is no gradual departure from “normal” patterns of integration;
4. individual-level deviation of the shape that each mouse actually has from the shape it “should have” if it followed the “normal” pattern of integration does not simply increase as the number of Robertsonian fusions increase (see part C of figure above).
The paper is open access on the publisher’s website. https://doi.org/10.1093/cz/zoaa035