Does multiple paternity affect seed mass in angiosperms? An experimental test inDalechampia scandens

Abstract

Flowers fertilized by multiple fathers may be expected to produce heavier seeds than those fertilized by a single father. However, the adaptive mechanisms leading to such differences remain unclear, and the evidence inconsistent. Here, we first review the different hypotheses predicting an increase in seed mass when multiple paternity occurs. We show that distinguishing between these hypotheses requires information about average seed mass, but also about within-fruit variance in seed mass, bias in siring success among pollen donors, and whether siring success and seed mass are correlated. We then report the results of an experiment on Dalechampia scandens (Euphorbiaceae), assessing these critical variables in conjunction with a comparison of seed mass resulting from crosses with single vs. multiple pollen donors. Siring success differed among males when competing for fertilization, but average seed mass was not affected by the number of fathers. Furthermore, paternal identity explained only 3.8% of the variance in seed mass, and siring success was not correlated with the mass of the seeds produced. Finally, within-infructescence variance in seed mass was not affected by the number of fathers. These results suggest that neither differential allocation nor sibling rivalry has any effect on the average mass of seeds in multiply sired fruits in D. scandens. Overall, the limited paternal effects observed in most studies and the possibility of diversification bet hedging among flowers (but not within flowers), suggest that multiple paternity within fruits or infructescence is unlikely to affect seed mass in a large number of angiosperm species.

Plant and Animal Reproductive Strategies: Lessons from Offspring Size and Number Tradeoffs

“…Importantly, the nutrient drawing ability (Uma Shaanker et al, 1995) of a seed is a function of its size: bigger seeds can invest more resources into resource drawing, and by doing so may overcome maternal controls and create a resource shortage for smaller seeds. When the offspring demands become overwhelming, the parent plant may selectively abort "inferior" embryos to ensure survival of a few offspring Pélabon et al, 2015; Figure 1B) and thus increase parental fitness (Haig, 1990;Vaughton and Carthew, 1993). Similarly, some animals selectively starve the weakest offspring when resources become limited after oviposition or birth (Lack, 1954;Ricklefs, 1965;Klopfer and Klopfer, 1973).…”

Rainfall seasonality predicts the germination behavior of a tropical dry‐forest vine

“…Such patterns are common for life‐history traits (Houle, ), but it is not entirely clear how this affects their evolutionary dynamics. Low additive genetic variance in seed size has been commonly reported (e.g., Schwaegerle & Levin, ; Pélabon, Albertsen, Falahati‐Anbaran, Wright, & Armbruster, ; Pélabon et al, ) and may constrain the evolution of germination behavior mediated by seed size.…”

Quantitative and qualitative consequences of reduced pollen loads in a mixed‐mating plant

“…For pollination, we used pollen from a freshly dehisced male flower from a randomly chosen pollen donor. Note that effects of paternal identity on seed mass are very limited in D. scandens (Pélabon, Albertsen, Falahati‐Anbaran, Wright, & Armbruster, ; Pélabon et al, ).…”

“…Note that effects of paternal identity on seed mass are very limited in D. scandens (Pélabon, Albertsen, Falahati-Anbaran, Wright, & Armbruster, 2015;Pélabon et al, 2016).…”

“…Previous studies of different taxa of the D. scandens complex showed that blossom size may affect seed mass (Opedal et al, 2015;Pélabon et al, 2015Pélabon et al, , 2016. To account for this source of variation, we measured the diameter of the peduncle of the pollinated blossoms with digital callipers (0.01 mm precision) and used this measure as a proxy for blossom size.…”