Page 5 - Scani_et_al1995

EVOLUTION OF HYBRID STICK-INSECTS 63

(continued) BREP

Locus Genotypes BATT BGGR BGBS BGBL BGMA BREB

Downloaded by [31.185.101.124] at 08:47 23 March 2016Adk-2 96/100 1.00 1.00 1.00 1.00 1.00 0.01
Pgm 100/100 0.74 0.37 1.00 0.99
107/107 0.26 1.00 0.21 1.00 0.89
Fh 96/103 0.25 0.92 0.07
Mpi 99/103 0.75 0.08 0.07 0.11
Pgi 100/100 0.07
0.89 1.00 0.14 0.03
100/103 0.11 1.00 0.07 1.00 0.97
100/105 1.00 1.00
103/103 0.43 1.00 0.88 1.00
105/105 0.57 0.12 0.02
118/118 1.00 1.00 0.98 1.00
118/122 0.37
86/90 1.00 0.57 1.00 1.00
0.04
90/90 0.06 0.08
93/93 0.04
95/95
100/100 0.68
104/104 0.16
100/100 1.00

103/103
103/108
112/112
112/116
116/116
76/76
76/80
76/84
78/84
80/80
80/84
84/84
84/89

89/89
97/100
100/100

a: P<0.001; b: 0.01<P<0.001; c: 0.05<P<0.02.

allozymes have evolved to a great extent. The ability of tilization, the present day gene-pools have evolved to the
easily accepting heterospeciflc partners obviously has point that no fertile rossius x grandii or atticus x rossius
been of paramount importance in originating specific hybrids are produced any more, although, in the past,
hybrids - both diploid and triploid - and in maintaining they repeatedly occurred in nature.
the hemiclonal systems.
CYTOLOGY OF HYBRID GAMETOGENESIS
The low specificity in mate-recognition does not seem
to be peculiar to Bacillus species among stick-insects, When viable interspecific hybrids are produced, the
since some Australian phasmids appear to share a similar first main constraint they face, in view of their persisten-
trait: a male Extatosoma tiaratum copulated in the field ce, is the production of balanced gametes. In accordance
with a female Didymuria violescens (V. Scali, personal with the majority of both vertebrate and invertebrate
observation). systems, in natural hybrids oí Bacillus the females are fer-
tile, while the males are sterile (Haldane rule). Male
In Bacillus this peculiar feature has been checked also specimens can be produced at low frequency by
experimentally through an extensive hybridization hybridogenetic females (about 10 from B. rossius-g.
programme. It has been clearly shown that matings are benazzii x B. g. benazzii crosses, Mantovani & Scali,
easily obtained but specific hybrids of both sexes are 1992; about 15 from B. rossius-g. grandii x B. g. gran-
sterile, with the only exception of some atticus/grandii dii, Tinti, 1993a) and, most rarely, by clonal par-
females (unpublished). On the whole, our experimental
hybridizations further suggest that, while the mate-
recognition system still allows copulation and fer-