On 2017 Apr 25, Jeffrey Ross-Ibarra commented:

In my 2007 paper I find a positive correlation between the number of crossovers per bivalent and genome size. I note that this correlation is weaker than linear, such that genome size increases faster than the number of crossovers per bivalent. This means that measures of recombination that include genome size (e.g. cM/Mb) will decrease with increasing genome size (because the denominator increases faster than the numerator). The findings reported here of a negative correlation between cM/Mb and genome size are thus consistent with those reported in my 2007 paper.

On 2017 Apr 25, Jeffrey Ross-Ibarra commented:

In my 2007 paper I find a positive correlation between the number of crossovers per bivalent and genome size. I note that this correlation is weaker than linear, such that genome size increases faster than the number of crossovers per bivalent. This means that measures of recombination that include genome size (e.g. cM/Mb) will decrease with increasing genome size (because the denominator increases faster than the numerator). The findings reported here of a negative correlation between cM/Mb and genome size are thus consistent with those reported in my 2007 paper.