Aphis triglochinis and A. grossulariae clones from southern Poland produced fertile hybrid eggs under experimental conditions. Established hybrid clones expressed normal parthenogenetic reproduction but bisexual generations were obtained only in three hybrid clones out of twenty six. Fertile F1 hybrid eggs were obtained in one hybrid clone. Morphological and host-specificity features of A. grossulariae dominated in the majority of hybrid clones. The present results do not exclude the possibility of natural hybridisation of studied aphid species. Natural hybrids may be difficult to detect because of their "pure" morphological and host-specificity features.
A. schneideri and A. grossulariae clones from southern Poland produced fertile hybrid eggs under experimental conditions. Established hybrid clones expressed normal parthenogenetic reproduction but bisexual generations were not obtained, though a few sexuales developed in some cases. Morphological features of A. schneideri and host-specificity of A. grossulariae tended to dominate in the majority of hybrid clones. Independent inheritance of the studied morphological characters and host specificity can therefore be presumed.
Present results do not exclude the possibility of natural hybridisation of studied aphid species. Natural crosses might cause taxonomic and currant pest management problems., Rimantas Rakauskas, and Lit
A review of the literary data on the life cycles and host plant relationships of Aphis grossulariae Kaltenbach, A. schneideri (Börner) and A. triglochinis Theobald is presented. Morphometric analysis of the three species revealed insufficient discriminative value of the majority of characters commonly used in the keys. A modified key to fundatrices, apterous and alate viviparous females, gynoparous and oviparous females and males is presented.
Morphometric analysis of 176 natural samples of A. grossulariae Kaltenbach, 1843 and A. schneideri (Börner, 1940) was performed, using 308 alate and 750 apterous viviparous females from 25 countries altogether. Morphologically intermediate specimens of presumably hybrid origin were noticed in 63 (35.79%) samples, comprising 12.67% of all apterous and 4.87% of all alate viviparae studied. 31 sample originating from 11 countries had 50% or more intermediate specimens of one or both morphs. "Rich" samples (having 4 or more specimens of the same morph) with the prevailing numbers of hybrid morphotypes were from the Netherlands, Russia (Moscow and Stavropol regions), Moldova, Turkey (Ankara) and Tajikistan (Dushanbe). Present data are discussed in the context of possible natural hybridisation between A. grossulariae and A. schneideri (see also Rakauskas, 1999a, 1999b). Canonical discrimination functions are being advocated as more powerful tools for separating between the two species when compared with single morphological characters or ratios commonly used in the keys.