Flower size constrains reproductive potential in three Andean monkeyflower species

Plants exhibit contrasting flower morphologies depending on their reproductive strategy, with autogamous species typically having smaller flowers than allogamous ones. Flower size can restrict the reproductive potential of species, as the development among flower parts is interrelated. This can result in a constraint on ovary size in adult plants, reducing the number of ovules produced, particularly in autogamous species with small flowers, in contrast to allogamous species with larger flowers. To test this hypothesis, we studied the static allometric relationships (allometry measured at mature flowers) of monkeyflower species (Erythranthe) endemic to the Andean region, including an autogamous species (E. glabrata), two allogamous species (E. depressa and E. lutea), and hybrids obtained from E. depressa x E. lutea crosses. We measured flower traits, counted ovules, and determined the static allometric relationships among traits for all taxa. Our study revealed that static allometric relationships are highly maintained among studied Erythranthe, with flower length serving as a crucial indicator of the dimensions that different flower parts reach. This suggests that flower length is an important factor determining the maternal reproductive potential in Erythranthe, with both autogamous and allogamous species showing a positive relationship between flower length and ovule number. Overall, investigating allometric relationships in Erythranthe, including hybrids, can shed light on the complex interactions between flower morphology and reproductive strategies in plants.