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togenetic mechanism and the hybrid structure of B. lyn- BULLINI, L., G. NASCETTI, and A. P. BIANCHI BULLINI. 1984. Downloaded from http://mbe.oxfordjournals.org/ by guest on April 9, 2016
ceorum: the former prevents possible exchange during A new stick-insect of hybrid origin: Bacillus lynceorum n.
meiosis, and the latter probably reduces the homogeniz- sp. (Cheleutoptera: Bacillidae). Atti Accad. Lincei Rend. Cl.
ing mechanism during the cell cycle. Furthermore, a re- Sci. Fis. Mat. Nat. Sez. VIII 75:169–176.
cent origin of the triploid could explain the low homog-
enization between atticus- and grandii grandii–like CHARLESWORTH, B., P. SNIEGOWSKI, and W. STEPHAN. 1994.
monomers. On the whole, it is evident that the two par- The evolutionary dynamics of repetitive DNA in eukary-
thenogens B. atticus and B. lynceorum share the same otes. Nature 371:215–220.
outcome of unisexual reproduction but behave differ-
ently in terms of genomic turnover mechanisms and CREASE, T. J., and M. LYNCH. 1991. Ribosomal DNA variation
rates mainly in relation to their different origins, with in Daphnia pulex. Mol. Biol. Evol. 8:620–640.
the automictic B. atticus representing a parthenogenetic
differentiation of an ancestral bisexual species and the DOVER, G. A. 1986. Molecular drive in multigene families:
apomictic B. lynceorum being an interspeciﬁc trihybrid how biological novelties arise, spread and are assimilated.
taxon. Yet, the very low p-distance value observed for Trends Genet 2:159–165.
the grandii grandii–like sequences of B. lynceorum
needs to be explained. It would be of interest to inves- DOVER, G. A., and D. TAUTZ. 1986. Conservation and diver-
tigate whether the level of variability of Bag320 satellite gence in multigene families: alternative to selection and
sequences in the diploid B. whitei—the other partheno- drift. Philos. Trans. R. Soc. Lond. B Biol. Sci. 312:275–
genetic hybrid of the genus—matches that of B. lynceo- 289.
rum grandii grandii–like monomers or that of pure B.
grandii grandii sequences. In the latter instance, a recent GODAY, C., A. P. BIANCHI BULLINI, G. NASCETTI, and L. BUL-
origin and/or the involvement of very few individuals LINI. 1981. Chromosome studies on Bacillus atticus, Bacil-
in the hybridization event(s) could explain the low value lus rossius and their hybrids (Cheleutoptera, Bacillidae).
found among grandii grandii–like monomers of B. lyn- Atti Accad. Lincei Rend. Cl. Sci. Fis. Mat. Nat. 71:126–
ceorum. 133.

To summarize, Bag320 sequence analysis of B. lyn- HILLIS, D. M., C. MORITZ, C. A. PORTER, and R. J. BAKER.
ceorum has deﬁnitively demonstrated its trihybrid ori- 1991. Evidence for biased gene conversion in concerted
gin, showing this molecular approach to be a taxonomic evolution of ribosomal DNA. Science 251:308–310.
tool of basic importance. Moreover, present results,
while supporting bisexuality as a driving force in variant KIMURA, M. 1980. A simple method for estimating evolution-
ﬁxation, show that the origin and gametogenetic pro- ary rate of base substitutions through comparative studies
cesses of unisexuals may be mirrored in different ge- of nucleotide sequences. J. Mol. Evol. 16:111–120.
nomic turnover rates.
KUMAR, S., K. TAMURA, and M. NEI. 1993. MEGA: molecular
Acknowledgments evolutionary genetics analysis. Version 1.01. The Pennsyl-
vania State Univesity, University Park.
This research was funded by Italian Ministero
Universita` e Ricerca Scientiﬁca e Tecnologica and by LA VOLPE, A. 1994. A repetitive DNA family, conserved
Consiglio Nazionale delle Ricerche. I wish to thank all throughout the evolution of free-living nematodes. J. Mol.
the ‘‘stick insect’’ group: Prof. V. Scali and Drs. S. Man- Evol. 39:473–477.
aresi, O. Marescalchi, M. Passamonti, and F. Tinti. Spe-
cial thanks to Prof. S. Cavicchi for statistical help and MANARESI, S., O. MARESCALCHI, and V. SCALI. 1993. The tri-
to the two anonymous referees who, together with C. hybrid genome constitution of Bacillus lynceorum (Insecta
Moritz, helped me in revising the manuscript. My work Phasmatodea) and its structural-cytogenetic variations. Ge-
is dedicated to the memory of Prof. C. Garavini and A. nome 36:317–326.
Mantovani.
MANTOVANI, B., R. BATISTONI, I. NARDI, and V. SCALI. 1993.
LITERATURE CITED A centromeric satellite DNA of the unisexual Bacillus at-
ticus (Insecta Phasmatodea). Insect Mol. Biol. 2:141–147.
BACHMANN, L., and D. SPERLICH. 1993. Gradual evolution of
a speciﬁc satellite DNA family in Drosophila ambigua, D. MANTOVANI, B., and V. SCALI. 1993. Genetic structure and
tristis and D. obscura. Mol. Biol. Evol. 10:647–659. phyletic relationships of eastern mediterranean Bacillus at-
ticus Brunner (Insecta Phasmatodea): a biochemical study.
BACHMANN, L., F. VENANZETTI, and V. SBORDONI. 1996. Tan- Biochem. Genet. 31:343–362.
demly repeated satellite DNA of Dolichopoda schiavazzii:
a test for models on the evolution of highly repetitive DNA. MANTOVANI, B., V. SCALI, and F. TINTI. 1992. New morpho-
J. Mol. Evol. 43:135–144. logical and allozymic characterization of Bacillus whitei
and B. lynceorum hybrid complexes (Insecta Phasmatodea).
BADARACCO, G., G. TUBIELLO, R. BENFANTE, F. COTELLI, D. Biol. Zentbl. 111:87–103.
MAIORANO, and N. LANDSBERGER. 1991. Highly repetitive
DNA sequence in parthenogenetic Artemia. J. Mol. Evol. MANTOVANI, B., F. TINTI, L. BACHMANN, and V. SCALI. 1997.
32:31–36. The Bag320 satellite DNA family in Bacillus stick insects
(Phasmatodea): different rates of molecular evolution of
BULLINI, L. 1994. Origin and evolution of animal hybrid spe- highly repetitive DNA in bisexual and parthenogenetic taxa.
cies. Trends Ecol. Evol. 9:422–426. Mol. Biol. Evol. 14:1197–1205.

MANTOVANI, B., F. TINTI, and V. SCALI. 1995. Genetic structure
and similarity relationships of the unisexual Cyprian Bacil-
lus (Insecta Phasmatodea). Biol. Zentbl. 114:299–306.

MARESCALCHI, O., L. P. PIJNACKER, and V. SCALI. 1991. Cy-
tology of parthenogenesis in B. whitei and B. lynceorum
(Insecta Phasmatodea). Invertebr. Reprod. Dev. 20:75–81.
. 1993. Automictic parthenogenesis and its genetic con-
sequence in Bacillus atticus atticus (Insecta Phasmatodea).
Invertebr. Reprod. Dev. 24:7–12.

MARESCALCHI, O., and V. SCALI. 1997. Chromosomal and
NOR patterns in the polyclonal stick insect Bacillus atticus
atticus (Insecta; Phasmatodea). Genome 40: 261–270.

PREISS, A., D. A. HARTLEY, and S. ARTAVANIS-TSAKONAS.
1988. Molecular genetics of enhancer of split, a gene re-

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