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.; GIORGIS, M.; ASHWORTH, L

Congreso; V Seed Ecology Conference; 2016

Given that largerseeds are able to cope with adverse or competitive environmentslarger seeds are usually related to greater plant fitness.Accordingly, seeds are expected to become larger at higher elevationsto overcome the harsher environmental conditions that prevail athigher altitudes. However, plant fitness also depends directly on thenumber of seeds produced, and variability in both seed size andnumber should be considered to understand how elevation may modulateplant fitness. Here we addressed how individual seed mass, total seednumber per plant and germinability changed along an elevationgradient in Baccharis aliena, andanalyzed changes in multiplicative fitness to address how individualseed mass relates to fitness. Todo so, we tagged 10 female plants of B.aliena inpopulations located at 900, 1200,1600 and 2000 m ASL along the Sierras Grandes hills, CordobaProvince, Argentina. At flowering, we registered the completenumber of inflorescences produced by each plant. At fruiting, wecollected three inflorescences from each focal plant and registeredthe number of viable seeds/inflorescence, individual seed mass andgerminability. Multiplicative fitness was obtainedas follows: total number of inflorescences per plant*average numberof seeds per inflorescence*average seed germinability. Individualseed mass and germinability showed a U-shape relationship withelevation, and therefore seeds from 900 and 2000 m ASL had thelargest seeds and highest germination values. Total seednumber per plant increased with elevation but multiplicative fitnesswas similar along the gradient. A seed size-numbertrade-off has shown that B. alienais able to offset for a lower seed number with larger seeds. Tosummarize, our results do not support the hypothesis that harsherenvironmental conditions should necessarily increase plant fitness byproducing larger seeds in this species.