Table 1 Karyotypic composition of 16 Cytoraces along with their parental crosses and the contribution of parental chromosomes in the evolution of the nasuta-albomicans complex of Drosophila. The superscripts 'n' and 'a' indicate the chromosomes derived from 'D. n. nasuta' and ' D. n. albomicans' parents respectively. O = Okinawan and T = Thailand strains of D. n. albomicans. (Roman numbers in bracket denote the Cytorace groups based on number of chromosomes contributed by D. n. nasuta and D. n. albomicans).

D. n. nasuta (N)

♂ - 2n = 8 - 2ⁿ2ⁿ Xⁿ Yⁿ 3ⁿ 3ⁿ 4ⁿ 4ⁿ ♀ - 2n = 8 - 2ⁿ 2ⁿ Xⁿ Xⁿ 3ⁿ 3ⁿ 4ⁿ 4ⁿ

16

0

D.n. albomi cans (A)

♂ - 2n = 6 - 2^a2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2^a 2^a X3^a X3^a 4^a 4^a

0

12

N♂ X A(O)♀

Cytorace 1 (C 1)

♂ - 2n = 7 - 2ⁿ 2^a X3^a Yⁿ 3ⁿ 4ⁿ 4ⁿ ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4ⁿ 4ⁿ

8

5 (I)

A(O)♂ X N♀

Cytorace 2 (C 2)

♂ - 2n = 6 - 2ⁿ 2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

2

10 (II)

N♂ X A(T)♀

Cytorace 3 (C 3)

♂ - 2n = 8 - 2ⁿ 2^a Xⁿ Yⁿ 3ⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a4^a

10

6 (III)

A(T)♂ X N♀

Cytorace 4 (C 4)

♂ - 2n = 7 - 2ⁿ 2^a Y3^a Xⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a 4^a

8

7 (IV)

C1♂ X A(T)♀

Cytorace 5 (C 5)

♂ - 2n = 7 - 2ⁿ 2^a X3^a Yⁿ 3ⁿ4^a4^a ♀ - 2n = 6-2ⁿ2^a X3^a X3^a4^a4^a

4

9 (V)

C4♂ X C1♀

Cytorace 6 (C 6)

♂ - 2n = 7 - 2ⁿ 2^a Y3^a Xⁿ 3ⁿ 4ⁿ 4ⁿ ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4ⁿ 4ⁿ

12

3 (VI)

C1♂ X C2♀

Cytorace 7 (C 7)

♂ - 2n = 7 - 2ⁿ 2^a X3^a Yⁿ 3ⁿ4^a4^a ♀ - 2n = 6 -2ⁿ2^a X3^a X3^a4^a4^a

4

9 (V)

C1♂ X C4♀

Cytorace 8 (C 8)

♂ - 2n = 7 - 2ⁿ 2^a X3^a Yⁿ 3ⁿ 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

4

9 (V)

C2♂ X N♀

Cytorace 9 (C 9)

♂ - 2n = 6 - 2ⁿ 2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

2

10 (II)

C3♂ X N♀

Cytorace 10 (C 10)

♂ - 2n = 8 - 2ⁿ 2^a Xⁿ Yⁿ 3ⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a 4^a

10

6 (III)

C2♂ X A♀

Cytorace 11 (C 11)

♂ - 2n = 6 - 2ⁿ 2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

2

10 (II)

A♂ X C1♀

Cytorace 12 (C 12)

♂ - 2n = 6 - 2ⁿ 2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

2

10 (II)

A♂ X C2♀

Cytorace 13 (C 13)

♂ - 2n = 6 - 2ⁿ 2^a X3^a Y3^a 4^a 4^a ♀ - 2n = 6 - 2ⁿ 2^a X3^a X3^a 4^a 4^a

2

10 (II)

C4♂ X C3♀

Cytorace 14 (C 14)

♂ - 2n = 7 - 2ⁿ 2^a Y3^a Xⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a 4^a

8

7 (IV)

C3♂ X C4♀

Cytorace 15 (C 15)

♂ - 2n = 8 - 2ⁿ 2^a Xⁿ Yⁿ 3ⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a 4^a

10

6 (III)

N ♂ X C3♀

Cytorace 16 (C 16)

♂ - 2n = 8 - 2ⁿ 2^a Xⁿ Yⁿ 3ⁿ 3ⁿ 4^a 4^a ♀ - 2n = 8 - 2ⁿ 2^a Xⁿ Xⁿ 3ⁿ 3ⁿ 4^a 4^a

10

6 (III)