Clonal variation: birth order produces life-history diversity in the Greater Duckweed, Spirodela polyrhiza

Abstract

Evolutionary response to environmental variation is required for survival and may occur through adaptive tracking, phenotypic plasticity or bet hedging. Variable dormancy is a classical bet-hedging trait in literature, and enables survival through harsh conditions. Greater Duckweed, Spirodela polyrhiza, forms overwintering propagules called "turions". However, S. polyrhiza propagates clonally, and it is unknown how diversified dormancy behaviour is generated among genetically identical offspring. Here, I investigate sources of variation in turion formation in Spirodela polyrhiza. I tested whether turion production is stimulated by birth order, size and temperature under controlled conditions of a growth chamber and a thermogradient incubator. Parental birth order was found to have a significant effect on turion formation; furthermore, this effect is temperature-dependent. This study addresses fundamental questions on mechanisms generating diversity in dormancy behavior, and provides insight into the natural history of Spirodela polyrhiza, an emerging model organism for ecological studies.iii