Seed tolerance to predation: Evidence from the toxic seeds of the buckeye tree (Aesculus californica; Sapindaceae)

Department of Biology, Stanford University, Stanford, California 94305-5020 USA.
American Journal of Botany (Impact Factor: 2.6). 07/2009; 96(7):1255-61. DOI: 10.3732/ajb.0800297
Source: PubMed


Tolerance, the capacity of plants to withstand attack by animals, as opposed to resistance, has been poorly examined in the context of seed predation. We investigated the role that the seed mass of the large-seeded endemic tree Aesculus californica plays as a tolerance trait to rodent attack by comparing, under greenhouse conditions, patterns of germination, and subsequent seedling growth, of seeds with a wide range of natural damage. Germination percentage was reduced by 50% and time to germination by 64% in attacked compared to intact seeds, and germination probability was negatively correlated with damage. Seedlings that emerged from intact seeds were taller and bore more leaves than those from damaged seeds. This species' large seed mass favors tolerance to damage because heavily damaged seeds are able to germinate and produce seedlings. This finding is significant given that seeds of this species are known to contain chemical compounds toxic to vertebrates, a resistance trait. We posit that this combination of tolerance and resistance traits might be a particularly effective antipredation strategy when seeds are exposed to a variety of vertebrate predators.

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Available from: Eduardo Mendoza, Oct 07, 2015
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    • "At the seed level, many seed traits can influence foraging decisions of hoarding animals. For example, high-tannin acorns can tolerate partial consumption by scatterhoarding rodents (e.g., gray squirrel, Sciurus carolinensis) and these partially-consumed acorns can become seedlings if their embryos are not damaged by the animals (Steele et al. 1993, Xiao et al. 2007, Mendoza and Dirzo 2009). Non-dormant seeds can transfer their energy and nutrients into indigestible taproots through rapid germination before hoarding animals recover them (Cao et al. 2011). "
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    ABSTRACT: Citation: Xiao, Z., and C. J. Krebs. 2015. Modeling the costs and benefits of seed scatterhoarding to plants. Ecosphere 6(4):53. http://dx. Abstract. Many plants interact with scatterhoarding animals as mutualists (seed dispersers) and antagonists (seed predators) simultaneously, but the net effects of scatterhoarding animals are rarely measured. In seed-dispersal mutualisms, plant benefits (recruitment) received from dispersal agents should outweigh the costs, resulting in a relative fitness gain. Otherwise, plant populations cannot be sustained and would go extinct. Here we present a framework to quantify costs and benefits of scatterhoarding for animal-dispersed plants and propose three models with the three separate scales (seed, tree and population) to quantify the costs and benefits for plants from scatterhoarding rodents. Since scatterhoarding is an adaptive dispersal strategy for many large-seeded plants, tree-and population-based models are needed to determine the costs and benefits for the plants. In the models presented here, all relevant parameters can be measured by regular surveys. Our tree-and population-based models can be extended to seed plants that have dispersal agents other than scatter hoarding rodents.
    Ecosphere 04/2015; 6(4). DOI:10.1890/ES14-00438.1 · 2.26 Impact Factor
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    • "Rapid germination of non-dormant seeds is used by tree species to reduce seed losses by rodents (Chang et al. 2009; Fox 1982; Hadj-Chikh et al. 1996), whereas in response, embryo-removal is used by some rodent species to stop or delay seed germination (Steele 2008; Steele et al. 2001; Xiao et al. 2009). Previous studies have demonstrated that, in general, embryo removal causes the failure of natural regeneration of seeds (Mendoza and Dirzo 2009; Steele 2008; Xiao et al. 2009). Multi-seeded acorns from some oak trees can germinate and develop into healthy seedlings when one seed is destroyed by squirrels (McEuen and "
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    ABSTRACT: Rapid germination of non-dormant seeds is one adaptation plants have evolved to counter seed predation by rodents. Some rodent species have evolved behaviors that prevent or slow the seed germination process through seed embryo removal or seed pruning; however, no plant species is known to have successfully escaped embryo removal or seed pruning by rodents. Here, we report that the non-dormant seeds of Pittosporopsis kerrii Craib in tropical rain forests in China have a high regeneration capacity to counter seed pruning by rodents. We found seed pruning, instead of embryo removal, was commonly used by rodents to increase food storage time by slowing down the seed germination process, but that P. kerrii seeds have a high regeneration capacity to escape seed predation by rodents: all pruned seeds, pruned roots and embryo-removed seeds by rodents or people retain the ability to develop into seedlings. Seeds of P. kerrii also have other capacities (i.e. rapid seed decomposition and indigestible dormant taproots) to escape predation by reducing the plant's attractiveness to rodents. The association between seed pruning behavior in rodents and high regeneration capacity of pruned seeds or roots in P. kerrii seeds are likely novel adaptation strategies adopted by seeds and rodents, respectively.
    Oecologia 02/2011; 166(4):997-1007. DOI:10.1007/s00442-011-1908-1 · 3.09 Impact Factor
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    ABSTRACT: Invasive rodents are among the most ubiquitous and problematic species introduced to islands; more than 80% of the world’s island groups have been invaded. Introduced rats (black rat, Rattus rattus; Norway rat, R. norvegicus; Pacific rat, R. exulans) are well known as seed predators but are often overlooked as potential seed dispersers despite their common habit of transporting fruits and seeds prior to consumption. The relative likelihood of seed predation and dispersal by the black rat, which is the most common rat in Hawaiian forest, was tested with field and laboratory experiments. In the field, fruits of eight native and four non-native common woody plant species were arranged individually on the forest floor in four treatments that excluded vertebrates of different sizes. Eleven species had a portion (3–100%) of their fruits removed from vertebrate-accessible treatments, and automated cameras photographed only black rats removing fruit. In the laboratory, black rats were offered fruits of all 12 species to assess consumption and seed fate. Seeds of two species (non-native Clidemia hirta and native Kadua affinis) passed intact through the digestive tracts of rats. Most of the remaining larger-seeded species had their seeds chewed and destroyed, but for several of these, some partly damaged or undamaged seeds survived rat exposure. The combined field and laboratory findings indicate that many interactions between black rats and seeds of native and non-native plants may result in dispersal. Rats are likely to be affecting plant communities through both seed predation and dispersal. KeywordsBlack rat–Captive feeding trials–Frugivory–Islands–Rodent–Seed size
    Biological Invasions 04/2011; 13(4):883-894. DOI:10.1007/s10530-010-9876-7 · 2.59 Impact Factor
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