Table 2 Dataset Pooled by Species with Levels of Phylogenetic Grouping Used in the Analysis Note that references given in Burt et al. [17] were not repeated here a K, kingdom. Numeric indicators in this column are: 1, Animalia; 2, Plantae b P, phylum. Numeric indicators in this column are: 1, Arthropoda; 2, Chordata; 3, Embryophyta; 4, Platyhelminthes c C, class. Numeric indicators in this column are: 1, Actinopterygii; 2, Amphibia; 3, Magnoliopsidae (subclass asterids); 4, Aves; 5, Coniferopsida; 6, Insecta; 7, Liliopsida; 8, Mammalia; 9, Magnoliopsidae (subclass rosids); 10, Trematoda; 11, Turbellaria d Data refers to linkage map (LM) or chiasma count (CC) e Male and female indicate the value for the chiasma count or map length for each sex f Ratio refers to male/female recombination rate g  Vsc refers to the presence or absence of sex chromosome (see Materials and Methods, “Sex chromosome effect”) h Data were obtained from maps DBNordic2 and NIAIJapan (http://www.genome.iastate.edu/pig.html) [54,55] ND, no data