Premating and Postmating Isolation among Populations ofMetaseiulus occidentalis(Nesbitt) (Acarina: Phytoseiidae)

Abstract

Differences in premating behavior patterns and timing, both within and between populations, were observed among reciprocal crosses of five populations of the western predatory mite, Metaseiulus occidentalis (Nesbitt). One population that was subjected to three selections for enhanced premating isolation showed no selection response. Postmating isolation in five of the eight pairs of reciprocal crosses of M. occidentalis colonies es resulted in the deposition of shriveled eggs and reduced numbers of apparently normal eggs. Reciprocal crosses usually exhibited different degrees of incompatibility; no apparent pattern with regard to geographic origin of the colonies was found in the degree of postmating isolation. The potential impact of postmating isolation on population dynamics was evaluated in reciprocal crosses of two populations using life table techniques. One colony was a strain that had been artificially selected in the laboratory for resistance to permethrin (Immature Selection-38), the other a population collected from a California pear orchard (McCall Pears). In the Immature Selection female (IS) X McCall Pear (MP) male cross, IS females produced fewer eggs than MP females in the reciprocal cross. Of the eggs deposited by the IS females mated to MP males, substantially more eggs shriveled than in the reciprocal cross. In addition, most of the surviving F1 progeny in the IS female X MP male cross were males. The net reproductive rate (R o) of the MP female X IS male cross was 10.58, but only 0.92 for the reciprocal cross. The intrinsic rate of increase (r m) of the MP female X IS male cross was 0.213 and zero for the reciprocal cross. The wide geographic distribution of M. occidentalis throughout western North America enhances the likelihood that genetically distinct populations have developed. The data pre-Continued inside back cover

Wolbachia and cytoplasmic incompatibility in the spider mites Tetranychus urticae and T. turkestani

“…Recently, Breeuwer & Jacobs (1996) reported on the widespread occurrence of Wolbachia in spider mites and predatory mites, which appears to parallel the situation in insects. Wolbachia-induced reproductive incompatibility has been postulated as a possible explanation for zygotic mortality (egg hatching failure) and male-biased sex ratios in crosses between geographical strains of the spider mite T. quercivorus (Gotoh et al, 1995) and in the predatory mite M. occidentalis (Hoy & Cave, 1988). This is the first study that shows that Wolbachia are indeed involved in unidirectional cytoplasmic incompatibility in the spider mites T. urticae and T. turkestani.…”

“…Recently, Tsagkarakou et al (1996) molecularly identified Wolbachia in a strain of T. urticae based on ftsZ and 16S ribosomal DNA sequence analysis. In predatory mites, Hoy & Cave (1988) observed nonreciprocal F 1 mortality and male-biased sex ratios among populations of the phytoseiid predatory mite Metaseiulus occidentalis. They suggested the possibility that unidirectional incompatibility might be mediated by microorganisms similar to those found in insects showing cytoplasmic incompatibility, based on earlier observations of rickettsialike microorganisms in this species (Hess & Hoy, 1982).…”

Morphological variation and reproductive incompatibility of three coconut-mite-associated populations of predatory mites identified as Neoseiulus paspalivorus (Acari: Phytoseiidae)

“…Bidirectional incompatibility is a rare phenomenon, as unidirectional incompatibilities are the most common in phytoseiid and tetranychid mite populations (Hoy and Cave 1988;Gotoh and Noguchi 1989;Gotoh et al 1995;Breeuwer 1997;Johanowicz and Hoy 1998;Vala et al 2000Vala et al , 2002Moraes 2002, 2004). Our results of bidirectional incompatibility among geographic populations of N. paspalivorus are therefore quiet exceptional, but are similar to those reported by Monetti and Croft (1996) with respect to crosses between the morphologically similar phytoseiid species Neoseiulus californicus (McGregor) and N. fallacis (Garman).…”

Compatibilidade Reprodutiva Entre Populações de Euseius citrifolius Denmark & Muma (Acari: Phytoseiidae)

“…Essa incompatibilidade pode ter causas exógenas, e estar relacionada com a presença de microrganismos simbiontes como bactérias do gênero Wolbachia, presentes no sistema reprodutivo causando efeitos em seus hospedeiros (Hoy & Cave 1988, Breeuwer & Jacobs 1996, Werren 1997, van der Geest et al 2000. Alguns estudos relatam a ocorrência de mortalidade do embrião e razão sexual em favor de machos quando de cruzamentos entre populações dos ácaros fitófagos Tetranychus neocaledonicus André, Amphitetranychus quercivorus (Ehara & Goth), Panonychus ulmi (Koch) e P. mori Yokoyama, e do fitoseídeo Galendromus occidentalis (Nesbitt) sugerindo a possibilidade de incompatibilidade devido à ocorrência de microrganismos (Hoy & Cave 1988, Breeuwer & Jacobs 1996, Johanowicz & Hoy 1999. É possível que a incompatibilidade reprodutiva entre populações e colônias de fitoseídeos, citada em vários estudos, seja conseqüência de diferenças genéticas entre seus simbiontes (Hoy 1985).…”