Is cladogenesis heritable?

The heritability of speciation rates and extinction risks is a crucial parameter in models of macroevolution, but little direct evidence has been available to assess the occurrence, strength, or generality of this heritability. We tested for heritability using correlations between ancestral and descendent branch lengths in phylogenetic trees, an approach first applied to a bird phylogeny by Harvey et al. (1991, pages 123-137 in Genes in ecology [R. J. Berry et al., eds.], Blackwell Scientific, Oxford). We applied Harvey et al.'s test to some of the largest DNA sequence-based phylogenetic analyses published to date for plants, insects, fungi, and bacteria. If one of two parent lineages splits first and if this is the case for any heritable reason, then on average we expect its daughter lineages to also split first. We also used a randomization procedure to assess significance of branch length heritability. Using maximum parsimony and maximum likelihood branch lengths and trees made ultrametric after nonparametric rate smoothing or by enforcing a molecular clock, we found a pattern for most clades consistent with heritable net cladogenesis. Heritability of cladogenesis may be a general phenomenon, detectable across a large number of lineages and a broad range of taxa.