© 2007 The Authors Entomologia Experimentalis et Applicata 122: 165–170, 2007 Journal compilation © 2007 The Netherlands Entomological Society 165 DOI: 10.1111/j.1570-7458.2006.00509.x Blackwell Publishing Ltd Maternal effects on the life histories of bruchid beetles infesting Acacia raddiana in the Negev desert, Israel K. Or 1* & D. Ward 2 1 Mitrani Department of Desert Ecology, Blaustein Institute for Desert Research, Ben Gurion University of the Negev, Sede Boqer 84990, Israel, 2 School of Biological and Conservation Sciences, University of KwaZulu-Natal, P. Bag X01, Scottsville 3209, South Africa Accepted: 11 October 2006 Key words: seed beetles, plant stress, Caryedon palaestinicus, Coleoptera, Bruchidae Abstract Acacia trees (Leguminosae) in the Negev desert of Israel are in substantial danger of extinction as a result of high mortality, caused by anthropogenically induced water stress and very low recruitment, which is highly negatively affected by bruchid beetle infestation. Intensive seed infestation (up to 97%) by bruchids on Acacia species in the Negev desert has been described. We hypothesized that water-stressed trees would be less able to produce secondary defense compounds in their seeds to decrease seed herbivory and hence suffer higher infestation. Thus, there should be a negative cor- relation between the beetle’s fitness and the tree’s physiological state. We further hypothesized the mechanism of the correlation to be maternal effects on beetle quality. Thus, beetles whose mothers were reared on seeds of trees in a poor state should have higher fitness, regardless of the quality of the seeds in which they were reared. We reared F 1 generation Caryedon palaestinicus Southgate (Coleoptera: Bruchidae) in seeds of Acacia raddiana Savi (Leguminosae) trees in good and in poor physiological state. We then conducted a reciprocal infestation experiment enabling females to lay on seeds from both sources. We found maternal effects on offspring number but not on body mass. The major effect was the limited survival of maternal beetles on trees in good physiological state. However, contrary to our prediction, C. palaestinicus developing in seeds from Acacia raddiana in good physiological state had significantly higher body mass. Introduction Acacia trees (Leguminosae) in the Negev and Arava are in substantial danger of extinction because of high mortality levels (up to 60%) and very low recruitment (Ashkenazi, 1995; Ward & Rohner, 1997). The major cause for the lack of recruitment is infestation of Acacia seeds by bruchid beetles (Coleoptera: Bruchidae). Bruchid infestation rates described in the Negev desert for the last 30 years are very high. Halevy (1974) recorded infestation rates of Acacia raddiana , Acacia tortilis , and Acacia pachyceras to be 72, 99, and 64%, respectively. In 1999, Rohner & Ward recorded infestation rates of 97.6% for A. raddiana and 96.2% for A. tortilis . These infestation rates are much higher than those described for Acacia trees in Africa, which range between 25.2 and 68% (Lamprey et al., 1974; Coe & Coe, 1987; Miller, 1994a,b; Or & Ward, 2003). We examine here the hypothesis that the extraordinarily high levels of bruchid infestation experienced by Negev Acacia trees are a consequence of the disturbance in the water regime of the trees (Ward & Rohner, 1997). We hypothesized that the relationship between Acacia physio- logical state and bruchid fitness is based on maternal effects. Maternal effects occur when a mother’s phenotype influences her offspring’s phenotype independently of the female’s genetic contribution to her offspring (Mousseau & Fox, 1998). Thus, the quality of the individual, and col- lectively the population, is influenced by the environment of the previous generation (Rossiter, 1995). If an affected offspring trait is critical to survival or fecundity, then maternal effects are capable of influencing the population dynamics through their contribution to population size and growth potential (Rossiter, 1995). For herbivorous insects, the maternal host may have large effects on offspring, including adaptive effects on patterns of host suitability * Correspondence: D. Ward, School of Biological and Conservation Sciences, University of KwaZulu-Natal, P. Bag X01, Scottsville 3209, South Africa. E-mail: ward@ukzn.ac.za