Is Evolution of Mating Preferences Inevitable? Random Mating in the Multisex System of Tetrahymena thermophila

Table 1

T. thermophila strains. All strains are whole-genome homozygotes and carry the mat-2 allele at the sex determination locus [12].

Parental strain^a	Progeny strain^b	Mating type (sex)	Drug resistance marker in germline (in soma)^c
CU438.1		IV	Pm-r (Pm-s)
	CU438.1-2	II	Pm-r (Pm-r)
	CU438.1-4	IV	Pm-r (Pm-r)
	CU438.1-5	V	Pm-r (Pm-r)
	CU438.1-7	VII	Pm-r (Pm-r)
CU428.2		VII	Mp-r (Mp-s)
	CU428.2-2	II	Mp-r (Mp-r)
	CU428.2-4	IV	Mp-r (Mp-r)
	CU428.2-5	V	Mp-r (Mp-r)
	CU428.2-7	VII	Mp-r (Mp-r)
CU427.4		VI	Cy-r (Cy-s)
	CU427.4-2	II	Cy-r (Cy-r)
	CU427.4-4	IV	Cy-r (Cy-r)
	CU427.4-5	V	Cy-r (Cy-r)
	CU427.4-7	VII	Cy-r (Cy-r)

^aStrains obtained originally from the Tetrahymena stock center are derived from the inbred strain B upon mutagenesis (P. Bruns, pers. comm.). These strains were used to construct drug resistant progeny strains of various mating types.
^bProgeny strains were generated using genomic exclusion [13]. All progeny strains show resistance to the respective drug owing to the resistance alleles they inherited from the germline of their parental strain.
^cDrugs are abbreviated: Pm: paromomycin, Mp: 6-methylpurine, Cy: cyclohexamide. Resistant phenotypes are indicated by “-r” and sensitive phenotypes by “-s”.