Table. S1.

Additional specimens of C. betulina and C. destructans examined.

Species	Isolatea	Perithecia diameter (μm)	Width of collar (μm) at base of perithecial neck	Length of perithecial neck (μm)	Ascospore s (μm)	Length of ostiolar hyphae (μm)	Flaskshaped conidiophor es (μm)	Cylindrical conidia (μm)	Widemouthed conidiophores (μm)	Doliifor m conidia (μm)	Aleurioconid ia (μm)
Ceratocystis betulina	C1709/CBS 144246	103–192	32–60	145–438	4.5–6 × 3–4	22–55	29–67 × Mouth 3–5 Base 2–6.5	10–19 × 2–3	14–33 × Mouth 3–5 Base 3–6	6–9 × 5–7	9–11 × 8–9
	C1770*	118–220	32–43	sparse or absent	not observed	not observed	43–86 × Mouth 3–4 Base 3.5–6	1–29 × 2.5–5	34–75 × Mouth 3–5 Base 3–6	8.5–12 × 5–8	8–14 × 8–13
Ceratocystis destructans	C578	119–298	39–98	198–757	4–6 × 2–3	30.5–73	20–48 × Mouth 2– 3.5 Base 4–6	12–19 × 2–4	not observed	not observed	10–14 × 9– 13
	C821	133–358	32–78	336–998	5–7 × 3–5	39–87	37–98 × Mouth 2–4 Base 4–6.5	13–21.5 × 2–4	38–69 × Mouth 2–4 Base 3–5	6.5–8 × 4–6.4	10–15 × 9– 12.5
	KARE1428/CBS 144247	122–208	44–64	381–626	4–5 × 3– 3.5	38–56	33–113 × Mouth 2–3 Base 3–5	12–26 × 2–3	26–69 × Mouth 3–4 Base 5–6	7–11 × 4–6	8–13 × 7–12
	KARE1610	133–320	41–98	253–795	4–6 × 3–4	26–74	33–75 × Mouth 3– 3.5 Base 3–5	12–19 × 3–4	34.5–66 × Mouth 3–4 Base 4–5	6–10 × 5.5–7	9–11 × 8– 10.5

^aIsolates in bold represent type specimens. Isolates with the prefix “C” are from the culture collection from T. C. Harrington at Iowa State University, isolates with the prefix “KARE” are from the culture collection at University of California Kearney Agricultural Research and Extension Centre.

*Sparse growth, many morphological features were infrequent or absent.