Effects of small-scale disturbances and elevation on the morphology, phenology and reproduction of a successful geophyte

Abstract

Aims We aimed to find out how a geophyte, Merendera montana, occupies a wide ecological, elevational and climatic range. This occurrence in that environmental array is outstanding not only among geophytes but also in the whole flora of the Iberian Peninsula, where only a very few plants show such an apparent success. Specifically, we compared morphological and reproductive traits, and frequency of different types of reproduction in disturbed and undisturbed grasslands. Furthermore, we have analyzed the phenology of this plant by trying to understand how it manages to spread in an exceptional elevational gradient of 2000 m, with contrasting climatic regimes between the mediterranean and the alpine regions. Methods We measured the plant density of M.montana populations in different types of Pyrenean grasslands either with or without small-scale disturbances at seven sites from the basal to the alpine belt (400– 2300 m a.s.l.). In each one of these populations, 100 individuals— 1200 in total—were uprooted to measure their morphological features as well as type and occurrence of reproduction. Phenology (flowering and fruiting dates and leaf lifespan) was estimated using 5 years of records in the studied areas and >200 herbarium sheets from the whole altitudinal rank and collected in the last 30 years. Differences in plant densities were analyzed with non-parametric Mann–Whitney U-test; differences in morphological traits, fruit and seed production associated with disturbance, with one-way analysis of covariance test (general linear model). Finally, linear regression analyses were used to determine the relationships between clonal reproduction and elevation and those between flowering, fruiting and senescence and date and elevation. Important Findings In all cases, plant density in disturbed grasslands was significantly higher than in undisturbed grasslands. Plant height and weight, bulb depth, leaf width and bulb and root weight were higher in disturbed plots. Disturbed and undisturbed plots were similar in most aspects of sexual reproduction, including fruiting percentage and seed production, but average seed weight was higher in the disturbed plots. Clonal reproduction and the synchrony of both types of reproduction were significantly higher in disturbed plots. Flowering and leaf emergence dates were not affected by disturbance but at the lowest elevations, they happened at least 2 months later than at the highest elevations. Summarizing, clonal reproduction, advantage in seedling establishment and an unusual but favorable phenology are the main factors in explaining the success of this geophyte colonizing disturbed soils that, in consequence, allow M.montana to settle in a wide range of climatic and ecological conditions.