Table 1. Mean transition rate coefficients between the different forms of sperm conjugation.

Transition rates (per unit branch length) and Z-values are based on 50,000 observations from 10,000,000 iterations from each of three reversible jump-MCMC runs. Z-values indicate the percentage of times that the transition rate was assigned to zero, removing the pathway from the model of trait evolution. Evolutionary transitions are considered probable when rarely assigned to zero (e.g., the transition from rouleaux to single sperm are much more probable than those to paired sperm). If the outgroup taxa of Amphizoidae and Asidytidae are included in the analysis, a transition from single sperm to aggregates becomes probable (0.28 ± 0.20, Z% = 7.2) but other transitions are only slightly affected.

Evolutionary transition	mean rate	SD	Z%
Single to paired	0.14	0.16	43.7
Single to aggregated	0.13	0.16	47.5
Single to rouleaux	0.15	0.17	37.8
Paired to single	0.18	0.18	31.5
Paired to aggregated	0.17	0.19	33.8
Paired to rouleaux	0.16	0.18	35.3
Aggregated to single	0.16	0.14	29.7
Aggregated to paired	0.28	0.14	0.4
Aggregated to rouleaux	0.23	0.13	6.6
Rouleaux to single	0.23	0.11	0.6
Rouleaux to paired	0.04	0.08	75.7
Rouleaux to aggregated	0.20	0.10	3.7