Lipid concentration in the embryo-endosperm fraction of seeds of Australian tropical lowland rainforest trees: relevance to defence and dispersal

The lipid concentration (LC) of the embryo-endosperm fraction was determined for the seeds of 60 species in 22 families from an Australian tropical lowland rainforest. It was negatively related to the mass of the embryo-endosperm across all species, but the relationship was not significant at P < 0.05. LC was significantly and positively correlated with N concentration when all species were considered, but not within the families represented by the most species (Lauraceae, 13; Sapindaceae, 9; Proteaceae, 6). LC was significantly and markedly higher in more heavily defended seeds (medians: 27 and 6.9%); there is evidence for the view that seeds rich in either lipid or nitrogen are markedly defended. Lipid concentration was also markedly higher, on average, in seeds taken by the scatter-hoarding Uromys caudimaculatus (white-tailed rat) than in seeds of comparable size not taken by Uromys, but not known to be protected by any toxin or irritant (medians: 35 and 3.7%, respectively). However, LC was not notably high in one major group of seeds taken by Uromys - the largest-seeded species of Beilschmiedia and Endiandra (Lauraceae). The comparisons mostly involved different phyletic lines, and were not consistently supported by contrasts within phyletic lines.