Table 3.

Test for treeness: f4 statistic.

Hp	f4 (X, Y; W, Z)
	X	Y	W	Z	Z-score	p-value	H-B
Series Ripariae	V. acerifolia	V. riparia	V. arizonica	V. rupestris	−1.21	n.s.	n.s.
	V. acerifolia	V. arizonica	V. rupestris	V. riparia	−2.93	3.4 x 10-03	*
	V. acerifolia	V. rupestris	V. arizonica	V. riparia	−3.40	6.7 x 10-04	**
Migration B	V. x slavinii	V. aestivalis var. lincecumii	V.girdiana	V. riparia	−6.73	1.7 x 10-11	****
				V. x novae-angliae	−0.35	n.s.	n.s.
Migration C	V. vulpina	V. mustangensis	V. popenoei	V. californica	−5.33	9.8 x 10-8	****
		V. shuttleworthii			−3.85	1.2 x 10-4	**
		V. mustangensis	V. nesbittiana		0.03	n.s.	n.s.
		V. shuttleworthii			−0.77	n.s.	n.s.
Migration E	V. popenoei	V. californica	V.girdiana	V. blancoi	−3.95	7.8 x 10-05	**
			V. arizonica		1.35	n.s.	n.s.
Migration F & Migration G	V. shuttleworthii	V. x champinii	V.girdiana	V. rupestris	3.11	1.87 x 10-3	*
				V. arizonica	1.36	n.s.	n.s.
		V. x doaniana		V. rupestris	3.17	1.5 x 10-3	*
				V. arizonica	1.85	n.s.	n.s.
				V. acerifolia	5.63	1.8 x 10-8	****
Migration H	V. popenoei	V. californica	V. biformis	V. bloodworthiana	2.10	0.035	n.s.
				V. monticola	1.86	n.s.	n.s.

Tested hypotheses are given in the first column (Hp). Migrations A–H refer to migration edges shown in Table 1 . When the parentage of a natural occurring hybrid is investigated, the name of the hybrid species is highlighted in bold. Z-scores computed using a block jackknifing procedure and their relative p-values are reported for each test. Statistical significance was further assessed according to Holm-Bonferroni (H-B) correction for multiple testing (n = 18). The interpretation of f4 test is described in Materials and Methods. n.s., not significant. *, p < 0.05; **, p < 0.01; ****, p<< 0.0001.