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Why wait? Trait and habitat correlates of variation in germination speed among Kalahari annuals

  • Physiological ecology - Original Paper
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Abstract

The longer soil has to stay moist to allow germination the more likely that seedlings experience favourable moisture conditions. Since theory predicts that fitness variance-reducing traits will be negatively correlated, we tested the hypothesis that time to germination is negatively correlated with the ability of radicle growth to keep up with the drying front. We measured time to germination and root elongation rate (RER) in 14 Kalahari annuals. We controlled for habitat (canopy association and sand content), germinability, median base water potential for germination (ψ 50), seed mass and seed shape as a persistence surrogate. For species and phylogenetically independent contrasts (PICs), we did not find a relationship between time to germination and RER. However, we found a negative relationship of time to germination with RER for PICs when controlling for sand content and ψ 50. Seed shape increased with time to germination which can be explained by reduced opportunities for germination in slow-germinating species that select for persistence. We found a positive relationship between time to germination and ψ 50, suggesting a continuum of risky to cautious germination. ψ 50 was not correlated with RER suggesting that variation in ψ 50 reflects different drought-adapted traits. Probably the relationship of time to germination with RER is not mediated by seed mass, which was not correlated with time to germination as found by others, though RER was positively correlated with seed mass. Instead of the seed size-seed number trade-off, a trade-off with resource capture may explain variation in RER: more root hairs or rootlets may increase resource capturing surface while reducing RER. For habitat, we found a (positive) relationship with time to germination only for canopy association. This may be explained by maximization of resource capture at the expense of RER being favoured by the higher nutrient and water availability under canopies. Future studies should clarify which trade-offs govern variation in time to germination, focussing on a possible resource capture-RER trade-off.

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References

  • Alizai HA, Hulbert LC (1970) Effects of soil texture on evaporative loss and available water in semi-arid climates. Soil Sci 110:328–332

    Article  Google Scholar 

  • Baker HG (1972) Seed weight in relation to environmental conditions in California. Ecology 53:997–1010

    Article  Google Scholar 

  • Baskin CC, Baskin JM (1998) Seeds: ecology, biogeography, and evolution of dormancy and germination. Academic Press, San Diego

    Google Scholar 

  • Boeken B, Gutterman Y (1990) The effect of temperature on seed germination in three common bulbous plants of different habitats in the central Negev desert of Israel. J Arid Environ 18:175–184

    Google Scholar 

  • Bond WJ, Honig M, Maze KE (1999) Seed size and seedling emergence: an allometric relationship and some ecological implications. Oecologia 120:132–136

    Article  Google Scholar 

  • Brown JS, Venable DL (1986) Evolutionary ecology of seed-bank annuals in temporally varying environments. Am Nat 127:31–47

    Article  Google Scholar 

  • Chesson P (2000) Mechanisms of maintenance of species diversity. Annu Rev Ecol Syst 31:343–366

    Article  Google Scholar 

  • Choinski JS, Tuohy JM (1991) Effect of water potential and temperature on the germination of four species of African savannah trees. Ann Bot 68:227–233

    Google Scholar 

  • Daws MI, Burslem DFRP, Crabtree LM, Kirkman P, Mullins CE, Dalling JW (2002) Differences in seed germination responses may promote coexistence of four sympatric Piper species. Funct Ecol 16:258–267

    Article  Google Scholar 

  • Daws MI, Ballard C, Mullins CE, Garwood NC, Murray B, Pearson TRH, Burslem DFRP (2007) Allometric relationships between seed mass and seedling characteristics reveal trade-offs for Neotropical gap-dependent species. Oecologia 154:445–454

    Article  PubMed  Google Scholar 

  • Daws MI, Crabtree LM, Dalling JW, Mullins CE, Burslem DFRP (2008) Germination responses to water potential in Neotropical pioneers suggest large-seeded species take more risks. Ann Bot 102:945–951

    Article  PubMed  Google Scholar 

  • Dean WRJ, Milton SJ, Jeltsch F (1999) Large trees, fertile islands, and birds in arid savannas. J Arid Environ 41:61–79

    Article  Google Scholar 

  • Elberse WTh, Breman H (1989) Germination and establishment of Sahelian rangeland species. I. Seed properties. Oecologia 80:477–484

    Article  Google Scholar 

  • Facelli JM, Brock DJ (2000) Patch dynamics in arid lands: localized effects of Acacia papyrocarpa on soils and vegetation of open woodlands of South Australia. Ecography 23:479–491

    Article  Google Scholar 

  • Facelli J, Chesson P, Barnes N (2005) Differences in seed biology of annual plants in arid lands: a key ingredient of the storage effect. Ecology 86:2998–3006

    Article  Google Scholar 

  • Felsenstein J (1985) Phylogenies and the comparative method. Am Nat 125:1–15

    Article  Google Scholar 

  • Fenner M (1983) Relationships between seed weight, ash content and seedling growth in twenty-four species of Compositae. New Phytol 95:697–706

    Article  Google Scholar 

  • Figueroa JA, Lusk CH (2001) Germination requirements and seedling shade tolerance are not correlated in a Chilean temperate rain forest. New Phytol 152:483–489

    Article  Google Scholar 

  • Flores J, Jurado E (2003) Are nurse-protégé interactions more common among plants from arid environments? J Veg Sci 14:911–916

    Article  Google Scholar 

  • Friedman J, Stein Z, Rushkin E (1981) Drought tolerance of germinating seeds and young seedlings of Anastatica hierochuntica L. Oecologia 51:400–403

    Article  Google Scholar 

  • Garland TJ, Dickerman AW, Janis CM, Jones JA (1993) Phylogenetic analysis of covariance by computer simulation. Syst Biol 42:265–292

    Google Scholar 

  • Goldberg DE, Turkington R, Olsvig-Whittaker L, Dyer AR (2001) Density dependence in an annual plant community: variation among life history stages. Ecol Monogr 71:423–446

    Article  Google Scholar 

  • Grime JP (2001) Plant strategies, vegetation processes, and ecosystem properties, 2nd edn. Wiley, Chichester

    Google Scholar 

  • Grime JP, Mason G, Curtis AV, Rodman J, Band SR, Mowforth MAG, Neal AM, Shaw S (1981) A comparative study of germination characteristics in a local flora. J Ecol 69:1017–1059

    Article  Google Scholar 

  • Grubb PJ (1977) The maintenance of species-richness in plant communities: the importance of the regeneration niche. Biol Rev 52:107–145

    Article  Google Scholar 

  • Gutterman Y (1993) Seed germination in desert plants. Springer, Berlin

    Google Scholar 

  • Gutterman Y, Edine L (1988) Variations in seed germination of Helianthemum vesicarium and H. ventosum from populations of two different altitudes in the Negev highlands, Israel. J Arid Environ 15:261–267

    Google Scholar 

  • Harvey PH, Pagel MD (1991) The comparative method in evolutionary biology. Oxford University Press, Oxford

    Google Scholar 

  • Joffre R, Rambal S (1988) Soil water improvement by trees in the rangelands of southern Spain. Acta Oecol 9:405–422

    Google Scholar 

  • Jurado E, Westoby M (1992) Germination biology of selected Central Australian plants. Aust J Ecol 17:341–348

    Article  Google Scholar 

  • Jurado E, Aguirre O, Flores J, Navar J, Villalón H, Wester D (2000) Germination in tamaulipan thornscrub of north-eastern Mexico. J Arid Environ 46:413–424

    Article  Google Scholar 

  • Kikuzawa K, Koyama H (1999) Scaling of soil water absorption by seeds: an experiment using seed analogues. Seed Sci Res 9:171–178

    Google Scholar 

  • Köchy M, Tielbörger K (2007) Hydrothermal time model of germination: parameters for 36 Mediterranean annual species based on a simplified approach. Basic Appl Ecol 8:171–182

    Article  Google Scholar 

  • Kos M (2007) Vegetation patterns in the Kalahari affected by Acacia erioloba: the importance of the regeneration niche. PhD thesis. University of Regensburg, Regensburg

  • Kos M, Poschlod P (2007) Seeds use temperature cues to ensure germination under nurse-plant shade in xeric Kalahari savannah. Ann Bot 99:667–675

    Article  PubMed  Google Scholar 

  • Kos M, Poschlod P (2008) Correlates of inter-specific variation in germination response to water stress in a semi-arid savannah. Basic Appl Ecol 9:645–652

    Article  Google Scholar 

  • Leishman MR, Westoby M (1994) The role of large seeds in seedling establishment in dry soil conditions–experimental evidence from semi-arid species. J Ecol 82:249–258

    Article  Google Scholar 

  • Leishman MR, Wright IJ, Moles AT, Westoby M (2000) The evolutionary ecology of seed size. In: Fenner M (ed) Seeds: The ecology of regeneration in plant communities, 2nd edn. CAB International, Wallingford

    Google Scholar 

  • Leistner OA (1967) The plant ecology of the southern Kalahari. Mem Bot Surv S Afr 38:1–172

    Google Scholar 

  • Leistner OA, Werger MJA (1973) Southern Kalahari phytosociology. Vegetatio 28:353–399

    Article  Google Scholar 

  • Martin AC (1946) The comparative internal morphology of seeds. Am Midl Nat 36:513–660

    Article  Google Scholar 

  • Milberg P, Andersson L, Thompson K (2000) Large-seeded species are less dependent on light for germination than small-seeded ones. Seed Sci Res 10:99–104

    Article  Google Scholar 

  • Nicotra AB, Babicka N, Westoby M (2002) Seedling root anatomy and morphology: an examination of ecological differentiation with rainfall using phylogenetically independent contrasts. Oecologia 130:136–145

    Google Scholar 

  • Padilla FM, Pugnaire FI (2007) Rooting depth and soil moisture control Mediterranean woody seedling survival during drought. Funct Ecol 21:489–495

    Article  Google Scholar 

  • Parker VT, Muller CH (1982) Vegetational and environmental changes beneath isolated live oak trees (Quercus agrifolia) in a California annual grassland. Am Midl Nat 107:69–81

    Article  Google Scholar 

  • Pearson TRH, Burslem DFRP, Mullins CE, Dalling JW (2002) Germination ecology of Neotropical pioneers: interacting effects of environmental conditions and seed size. Ecology 83:2798–2807

    Article  Google Scholar 

  • Purvis A, Rambaut A (1995) Comparative analysis by independent contrasts (CAIC): an Apple Macintosh application for analysing comparative data. Comput Appl Biosci 11:247–251

    CAS  PubMed  Google Scholar 

  • Rees M (1994) Delayed germination of seeds: a look at the effects of adult longevity, the timing of reproduction, and population age/stage structure. Am Nat 144:43–64

    Article  Google Scholar 

  • Stevens P F (2001 onwards) Angiosperm phylogeny website. Version 9, June 2008. http://www.mobot.org/MOBOT/research/APweb/

  • Templeton AR, Levin DA (1979) Evolutionary consequences of seed pools. Am Nat 114:232–249

    Article  Google Scholar 

  • Thompson K, Band SR, Hodgson JG (1993) Seed size and shape predict persistence in the soil. Funct Ecol 7:236–241

    Article  Google Scholar 

  • Venable DL, Brown JS (1988) The selective interactions of dispersal, dormancy, and seed size as adaptations for reducing risk in variable environments. Am Nat 131:360–384

    Article  Google Scholar 

  • Verdú M, Traveset A (2005) Early emergence enhances plant fitness: a phylogenetically controlled meta-analysis. Ecology 86:1385–1394

    Article  Google Scholar 

  • Wright IJ, Westoby M (1999) Differences in seedling growth behaviour among species: trait correlations across species, and trait shifts along nutrient compared to rainfall gradients. J Ecol 87:85–97

    Article  Google Scholar 

Download references

Acknowledgments

This study was carried out within the BIOTA Africa project funded by the German Federal Ministry of Education and Research (BMBF Förderkennzeichen 01 LC 0024 FuE Trockensavanne). We thank Northern Cape Nature Conservation for permission to collect and export seeds; the Department of Transport, Roads and Public Works for allowing us to collect seeds in the road reserve; Naas and Alida Mouton, Prof. Anne Rasa and Lena and Henry Snyders for allowing us to collect seeds on their farms; and Fernando Valladares, Carol Baskin, Jerry Baskin and three anonymous reviewers for their comments on previous versions of this manuscript. The authors declare that the experiments comply with the current laws of Germany and South Africa.

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  1. Institute of Botany, University of Regensburg, Universitätsstraße 31, 93040, Regensburg, Germany

    Martijn Kos & Peter Poschlod

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  1. Martijn Kos
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  2. Peter Poschlod
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Correspondence to Martijn Kos.

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Communicated by Fernando Valladares.

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Kos, M., Poschlod, P. Why wait? Trait and habitat correlates of variation in germination speed among Kalahari annuals. Oecologia 162, 549–559 (2010). https://doi.org/10.1007/s00442-009-1472-0

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