View Full Version : A mitochondrial genetic divergence proxy predicts the reproductive compatibility of m

06-04-2020, 07:38 AM
I found this study (https://royalsocietypublishing.org/doi/10.1098/rspb.2020.0690) interesting.


Some pieces of information:

We first explicitly defined two dichotomous categories along the spectrum of hybrid incompatibility. Category 1 is defined by mammalian species pairs capable of producing fertile F1 offspring of both sexes that can reproduce without backcrossing with a parent species (even if there are observed asymmetries in gene flow and variation in male fertility among the hybrids) (electronic supplementary material, table S1). category 2 is defined by pairs of species that can produce viable F1 offspring, but follow Haldane's Rule, and thus only female F1s can reproduce by backcrossing with a parent species. category 2 also includes species pairs whose hybrids are infertile (electronic supplementary material, table S1).

The category 1 pair with the greatest divergence value was a pair of guinea pig species that were 8.0% divergent, and the category 2 pair with the lowest divergence was a pair of vole species that were 7.2% divergent. Several pairs of species fall within this 0.8% overlapping region suggesting that this level of CYTB distance is the zone where some F1 mammalian offspring begin to require a backcross to generate an F2.

Towards the upper end of distance values between species pairs, both the male and female hybrid offspring of domestic pig (Sus domesticus) babirusa (Babyrousa celebensis) (12.9%) were shown to be infertile [24]. In addition, controlled, exhaustive efforts failed to produce any viable hybrids between mountain hares and European rabbits (17.3%) [25] (figure 1). The large distance values between these species pairs corroborates previous studies showing that along the continuum of speciation, infertility in both sexes evolves prior to inviability [2628].

Specifically, distances between domestic cats and jungle cats, leopard cats and servals (7.5%, 10.9% and 11.3%, respectively) are consistent with both the observed minimum (2, 3 and 4, respectively) and average (3, 4 and 5, respectively) number of backcrosses with domestic cats required for hybrid males to acquire fertility [31]. These results are also consistent with an early hybrid experiment using guinea pigs in which hybrids between Cavia fulgida and Cavia porcellus (8.0% CYTB distance) were able to regain male fertility after three generations of backcrossing [32] (electronic supplementary material, table S1).

Our analysis places the distance values between AMH and chimpanzees (11.0%), and AMH and bonobos (10.8%) within category 2, suggesting that even if hybrids could be produced, they would probably follow Haldane's Rule (figure 1; electronic supplementary material, figure S1).

The distance values for all of the pairings of three Homo groups (Sima de los Huesos, Neanderthals and AMH) occupy the bottom of the category 1 range. The distance values for Neanderthals and modern and ancient AMH specifically (1.6%) fall below all the mammalian pairs in this study including polar bears and brown bears (2.4%), and between subspecific crosses of M. musculus (2.3%) (figure 1; electronic supplementary material, figure S1 and table S1). When placed within this context, our data predict that ancient hominin lineages were probably not sufficiently divergent from each other to expect a significant biological impediment to the generation of fertile offspring.

Supplementary material: https://royalsocietypublishing.org/action/downloadSupplement?doi=10.1098%2Frspb.2020.0690&file=rspb20200690supp1.pdf