TY  - JOUR
A1  - Metz, Johannes
A1  - Freundt, Hanna
A1  - Jeltsch, Florian
T1  - Stable germination behavior but partly changing seed-seed interactions along a steep rainfall gradient
JF  - Basic and applied ecology : Journal of the Gesellschaft für Ökologie
N2  - Germination marks a critical transition in plant life that is prone to high mortality. Strong selection pressure is therefore expected to finely tune it to environmental conditions. Our study on the common Mediterranean grass Brachypodium hybridum assessed whether germination behavior changes systematically along a steep natural rainfall gradient ranging from harsh desert to rather mild mesic-Mediterranean conditions, We specifically tested hypotheses that germination behavior confers greater risk-spreading in populations from drier, unpredictable environments, and that seeds from wetter populations are better competitors. In 14 populations (spanning 114-954 mm annual rainfall) we assessed three alternative key parameters of germination in a greenhouse experiment: between-year dormancy, days to emergence within a season, and temporal spread. Addition of neighbor seeds accounted for competition as another crucial environmental factor. In six of the 14 populations, we also compared seeds originating from corresponding north (more mesic) and south (more arid) exposed hill slopes to test whether germination patterns along the large-scale rainfall gradient are paralleled at this smaller scale. B. hybridum exhibited generally high germination fractions and rapid emergence with very little temporal spread, indicating overall little risk-spreading germination. Surprisingly, none of the three parameters changed systematically with increasing aridity, neither at large scale along the rainfall gradient nor at small scale between north and south exposures. Neighbor seeds, however, mildly suppressed germination. Germination of neighbor seeds, in turn, was more strongly suppressed by B. hybridum seeds from drier populations, and this effect was stronger for forb than for grass neighbor species. Our results provide strong evidence that increased risk-spreading germination is not a universal, essential strategy to persist in increasingly dry, unpredictable environments. They also highlight that competition with neighbors occurs even at the earliest plant life stage. Since neighbor effects were species-specific, competition among seeds can affect community composition at later plant stages.
KW  - Aridity gradient
KW  - Bet-hedging germination
KW  - Brachypodium hybridum
KW  - Density dependence
KW  - Dormancy
KW  - Emergence time
KW  - Riskspreading
KW  - Seed competition
KW  - Slope exposure
KW  - Temporal spread
Y1  - 2018
U6  - https://doi.org/10.1016/j.baae.2018.01.004
SN  - 1439-1791
SN  - 1618-0089
VL  - 28
SP  - 5
EP  - 16
PB  - Elsevier
CY  - Jena
ER  -