Linking intraspecific seed mass variability to fitness along an elevational gradient: a test with Baccharis aliena.

CALVIÑO A., VENIER A.C., SCHINQUEL V., ZEBALLOS S. R., GIORGIS M.A. & ASHWORTH L.

Caeté

Conferencia; Seed Ecology V, seeds in the web of life.; 2016

the International Society for Seed Science (ISSS)

Given that larger seeds are able to cope with adverse or competitive environments, a larger seed size is usually related to a greater plant fitness. Accordingly, seeds are expected to become larger at higher elevations to overcome the harsher environmental conditions that prevail at higher altitudes. However, plant fitness also depends directly on the number of seeds produced, and variability in both seed size and number should be considered to understand how elevation may modulate plant fitness. Here we addressed how individual seed mass, total seed number per plant and germinability change along an elevation gradient in Baccharis aliena, and analysed changes in multiplicative fitness to address how individual seed mass relates to fitness. To do so, we tagged 10 female plants of B. aliena in populations located at 900, 1200, 1600 and 2000 m asl along the Sierras Grandes hills, Cordoba province, Argentina. At flowering, we registered the complete number of inflorescences produced by each plant. At fruiting, we collected three inflorescences from each focal plant and registered the number of viable seeds/inflorescence, individual seed mass and germinability. Multiplicative fitness was obtained as: total number of inflorescences per plant*mean number of seeds per inflorescence*average seed germinability. Individual seed mass and germinability showed an U-shape relationship with elevation, and therefore seeds from 900 and 2000 m asl had the largest seeds and highest germination values. Total seed number per plant increased with elevation but multiplicative fitness was similar along the gradient. A seed size-number trade-off showed that B. aliena is able to offset for a lower seed number with larger seeds. Overall, our result do not support the hypothesis that harsher enviromental conditions associated with an increasing elevation should increase plant fitness by producing larger seeds in this species.