Allozymic and cytological evidence for hemiclonal, all‐paternal, and mosaic offspring of the hybridogenetic stick insect Bacillus rossius‐grandii grandii

Bacillus hybridogens represent the first example of hemiclonal reproduction among invertebrates and they were analyzed in the present study for comparison with vertebrate hybridogenetic complexes (Poeciliopsis and Rana). Experimental crosses of southeastern hybridogenetic B. rossius‐grandii grandii females with both the parental species and hybrid males were carried out to test the reproductive potential of hybridogens. Allozyme and chromosome markers indicated that hemiclonal females actually reproduced in a variety of ways. Hybridogenesis was the most common and the rossius unassorted haploset was passed to the progeny while the grandii haploset was discarded during meiosis and replaced by that of the fathering male. Andro‐genesis, which was much rarer, led to the production of two types of all‐paternal offspring: unipa‐rental progeny of both sexes and all‐male progeny with the same allozyme and chromosome structure as their father. Mosaics of two kinds were also produced: the “h + h” type, with two different hybridogenetic cell lines; and the “h + a” type, with one hybridogenetic and one androgenetic cell line. Mosaics evolved into intersexes when their cell lines were sexually discordant. Among the evolutionary outcomes of this wide array of reproductive ways seems to be a shift from hemiclonality to clonality. This possibility is supported by the well‐established parthenogen B. whitei and the occasional production of rare invariant specimens from the northwestern hybridogenetic form B. rossius‐grandii benazzii. Bacillus and other unisexuals provide evidence of numerous reproductive interactions between hybrids and their bisexual relatives: the occurrence of such interactions may play an important role in the persistence, diversification and evolution of unisexuals. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc., A Wiley Company