Does endosperm reduce intra-fruit competition among developing seeds?

The evolution of endosperm, the tissue that nourishes developing embryos, has remained an enigma owing to its unique genetic composition. Because it contains both maternal (generally 2 doses) and paternal (1 dose) genomes, it is suggested to have evolved as a compromising tissue between the evolutionary interests of the maternal parent and offspring over resource allocation. This argument implies that in species where endosperm is highly functional and persistent, it quenches competition among developing embryos for resources and facilitates an equitable resource allocation to the developing offspring. Based on this argument we predict the association of well developed endosperm with certain features of fruits such as high ovule number per ovary and low extent of seed abortion. In this paper, we provide evidence in support of these predictions by analysing the data from 1131 species from the Flora of Presidency of Madras. We show that persistent and functional endosperm is more frequent in multiovulated than in uniovulated species and in species with less seed abortion. Our results also suggest that species with well developed endosperm tend to have uni-carpelled ovaries. Our analyses show that these associations are less likely to be emerging due to phylogenetic constraints. We argue that the endosperm has evolved as a maternal strategy of quenching the extent of sibling rivalry