Sexual modulation in a polyploid grass: a reproductive contest between environmentally inducible sexual and genetically dominant apomictic pathways

KARUNARATHNE, PIYAL; GLÜCKSBERG, ADRIANA; HOJSGAARD, DIEGO H.; SCHEDLER, MARA; HONFI, ANA I.; REUTEMANN, ANNA V.; MARTÍNEZ, ERIC J.

Scientific Reports

Springer Nature

Año: 2020 vol. 10

In systems alternating between sexual and asexual reproduction, sex increases under unfavorableenvironmental conditions. In plants producing sexual and asexual (apomictic) seeds, studies on theinfluence of environmental factors on sex are equivocal. We used Paspalum intermedium to studyenvironmental effects on the expression of sexual and apomictic developments, and on resultingreproductive fitness variables. Flow cytometric and embryological analyses were performed tocharacterize ploidy and reproductive modes, and effects of local climatic conditions on sexual andapomictic ovule and seed frequencies were determined. Seed set and germination data were collected and used to estimate reproductive fitness. Frequencies of sexual and apomictic ovules and seeds were highly variable within and among populations. Apomictic development exhibited higher competitive ability but lower overall fitness. Frequencies of sexual reproduction in facultative apomictic plants increased at lower temperatures and wider mean diurnal temperature ranges. We identified a twofold higher fitness advantage of sexuality and a Tug of War between factors intrinsic to apomixis and environmental stressors promoting sexuality which influence the distribution of sex in apomictic populations. This points toward a crucial role of local ecological conditions in promoting a reshuffling of genetic variability that may be shaping the adaptative landscape in apomictic P. intermedium plants.