Ido Izhaki – Current Research Projects


The ecophysiological response of birds versus mammals to secondary metabolites in fruits



(with Profs. Zeev Arad, William Karasov and Denise Dearing)




Project description:


Plant secondary metabolites (PSMs) are considered as defences against pathogens or herbivores, mammalian herbivores use both behavioural and physiological strategies to limit their negative effects. As many plants rely on frugivores for seed dispersal and many vertebrates rely on fruits for their nutritional requirements, coevolution is often assumed. PSMs in fruit pulp likely result from selective pressures imposed by fruit-consumers. Our central hypothesis is that PSMs are mediators of the interactions between plants and seed dispersers (frugivores) as well as seed predators (granivores). We will examine key assumptions of current hypotheses (“Protein Assimilation Hypothesis”, “Directed Toxicity Hypothesis” and “Gut Retention Time Hypothesis”): (a) PSMs impose pre- and post-ingestive effects on fruit consumers (b) PSMs are toxic (or deterrents) for vertebrate seed predators, but have no or little toxic effect on seed-dispersing frugivores. We will compare the behavioral and physiological impact of fruit PSMs of a key desert plant (Ochradenus baccatus) on two seed dispersing birds versus two rodents which are seed predators. We will manipulate PSM concentration in artificial fruits and use them to determine whether PSMs differentially affect frugivores vs. granivores with respect to fruit choice, gut retention time, detoxification ability, energy and nitrogen balance, digestive processing of nutrients, and diet breadth. The project is multidisciplinary in approach, ranges from molecular to ecological levels, and offers promise for uncovering new natural products.


Ochradenus baccatus fruits (Photo: Alon Lotan)


Ochradenus baccatus plants in the Arava, Israel (Photo: Alon Lotan)


Tristram's grackle (Onichognathus tristrami)  – an important fruit consumer of Ochradenus baccatus in Israel.


This project is supported by the US-Israel Bi-National Science Foundation ($180,000;  2007-2011).