Landscape Ecology

, Volume 27, Issue 2, pp 199–209 | Cite as

Determinants of actual functional connectivity for calcareous grassland communities linked by rotational sheep grazing

  • Yessica Rico
  • Hans Juergen Boehmer
  • Helene H. Wagner
Research Article


In fragmented landscapes, plant species persistence depends on functional connectivity in terms of pollen flow to maintain genetic diversity within populations, and seed dispersal to re-colonize habitat patches following local extinction. Connectivity in plants is commonly modeled as a function of the physical distance between patches, without testing alternative dispersal vectors. In addition, pre- and post-dispersal processes such as seed production and establishment are likely to affect patch colonization rates. Here, we test alternative models of potential functional connectivity with different assumptions on source patch effects (patch area and species occupancy) and dispersal (relating to distance among patches, matrix composition, and sheep grazing routes) against empirical patch colonization rates at the community level (actual functional connectivity), accounting for post-dispersal effects in terms of structural elements providing regeneration niches for establishment. Our analyses are based on two surveys in 1989 and in 2009 of 48 habitat specialist plants in 62 previously abandoned calcareous grassland patches in the Southern Franconian Alb in Bavaria, Germany. The best connectivity model S i , as identified by multi-model inference, combined distance along sheep grazing routes including consistently and intermittently grazed patches with mean species occupancy in 1989 as a proxy for pre-dispersal effects. Community-level patch colonization rates depended to equal degrees on connectivity and post-dispersal process. Our study highlights that actual functional connectivity of calcareous grassland communities cannot be approximated by structural connectivity based on physical distance alone, and modeling of functional connectivity needs to consider pre- and post-dispersal processes.


Colonization rates Species occupancy Regeneration niches Dispersal vector Incidence function model Germany 



This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grant; H. Wagner), the National Council on Science and Technology of Mexico (CONACYT; Y. Rico), the German Academic Exchange Service (DAAD; Y. Rico), and the Government of Central Franconia (baseline survey). We thank Karlheinz Dadrich, Doris Baumgartner, Bernd Raab Stefanie Haacke, Jens Sachteleben, and the shepherds Erich Beil, Erich Neulinger, and Alfred Grimm for valuable information, Henry Lehnert for management data collection, Hawthorne Bayer for GIS support, Marie-Josee Fortin, and two anonymous reviewers for comments on earlier versions of the manuscript, and the Landscape Genetics Working Group supported by NCEAS, a Center funded by NSF (Grant #EF-0553768), the University of California, Santa Barbara, and the State of California.


  1. Adriaens D, Honnay O, Hermy M (2006) No evidence of a plant extinction debt in highly fragmented calcareous grasslands in Belgium. Biol Conserv 133:212–224CrossRefGoogle Scholar
  2. Aguilar R, Quesada M, Ashworth L, Herrerias-Diego Y, Lobo J (2008) Genetic consequences of habitat fragmentation of plant populations: susceptible signals in plant traits and methodological approaches. Mol Ecol 17:5177–5188PubMedCrossRefGoogle Scholar
  3. Bender O, Boehmer HJ, Jens D, Schumacher KP (2005) Analysis of land-use change in a sector of Upper Franconia (Bavaria, Germany) since 1850 using land register records. Landscape Ecol 20:149–163CrossRefGoogle Scholar
  4. Bisteau E, Mahy G (2005) Vegetation and seed bank in a calcareous grassland restored from a Pinus forest. Appl Veg Sci 8:167–174CrossRefGoogle Scholar
  5. Boehmer HJ (1994) Die Halbtrockenrasen der Fränkischen Alb - Strukturen, Prozesse, Erhaltung. Mitteilungen der Fraenkischen Geographischen Gesellschaft 41:323–343Google Scholar
  6. Boehmer HJ, Janeck L, Steidler S, Raab B (1990) Verbundsystem Halbtrockenrasen. Trittstein- und Refugialbiotope im östlichen Landkreis Weissenburg-Gunzenhausen. Bayerisches Landesamt für Umweltschutz, LfU, MunichGoogle Scholar
  7. Bolli JC (2009) A multiscale assessment of plant dispersal: How functional traits and landscape characteristics interact. Dissertation Nr. 18380, Swiss Federal Institute of Technology, ETH Zurich.
  8. Bruckmann SV, Krauss J, Steffan-Dewenter I (2010) Butterfly and plant specialist suffer from reduced connectivity in fragmented landscapes. J Appl Ecol 47:799–809CrossRefGoogle Scholar
  9. Bruun HH, Fritzbøger B (2002) The past impact of livestock husbandry on dispersal of plant seeds in the landscape of Denmark. Ambio 31:425–431PubMedGoogle Scholar
  10. Calabrese JM, Fagan WF (2004) A comparison shoppers’ guide to connectivity metrics: trading off between data requirements and information content. Front Ecol Environ 2:529–536CrossRefGoogle Scholar
  11. Clobert J, Ims RA, Rousset F (2004) Causes, mechanism and consequences of dispersal. In: Hanski I, Gaggiotti OE (eds) Ecology genetics and evolution of metapopulations. Elsevier Academic Press, Amsterdam, pp 307–335CrossRefGoogle Scholar
  12. Coulson SJ, Bullock JM, Stevenson MJ, Pywell RF (2001) Colonization of grassland by sown species: dispersal versus microsite limitation in response to management. J Appl Ecol 38:204–216CrossRefGoogle Scholar
  13. Dolek M, Geyer A (2002) Conserving biodiversity on calcareous grasslands in the Franconian Jura by grazing: a comprehensive approach. Biol Conserv 104:351–360CrossRefGoogle Scholar
  14. Ellenberg H (1996) Vegetation Mitteleuropas mit den Alpen, 5th edn. Ulmer, StuttgartGoogle Scholar
  15. Erik SJ, Priya S (2003) A broader ecological context to habitat fragmentation: why matrix habitat is more important than we thought. J Veg Sci 14:459–464CrossRefGoogle Scholar
  16. Fagan WF, Calabrese JM (2006) Quantifying connectivity: balancing metric performance with data requirements. In: Crooks KR, Sanjayan MA (eds) Connectivity conservation. Cambridge University Press, Cambridge, pp 297–317CrossRefGoogle Scholar
  17. Fenner M, Thompson (2005) The ecology of seeds. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  18. Fischer J, Lindenmayer DB (2007) Landscape modification and habitat fragmentation: a synthesis. Glob Ecol Biogeogr 16:265–280CrossRefGoogle Scholar
  19. Fischer SF, Poschlod P, Beinlich B (1996) Experimental studies on the dispersal of plants and animals on sheep in calcareous grasslands. J Appl Ecol 33:1206–1222CrossRefGoogle Scholar
  20. Frakham R (2005) Genetics and extinction. Biol Conserv 126:131–140CrossRefGoogle Scholar
  21. Geertsema W (2005) Spatial dynamics of plant species in an agricultural landscape in the Netherlands. Plant Ecol 178:237–347CrossRefGoogle Scholar
  22. Hanski I (1994) A practical model of metapopulation dynamics. J Anim Ecol 63:151–162CrossRefGoogle Scholar
  23. Herrera JM, Garcia D, Morales JM (2011) Matrix effects on plant frugivore and plant-predator interactions in forest fragments. Landscape Ecol 26:125–135CrossRefGoogle Scholar
  24. Johst K, Brandl R, Eber S (2002) Metapopulation persistence in dynamic landscapes: the role of dispersal distance. Oikos 98:263–270CrossRefGoogle Scholar
  25. Joshi J, Stoll P, Rusterholz HP, Schmid B, Dolt C, Baur B (2006) Small-scale experimental habitat fragmentation reduces colonization rates in species rich-grasslands. Oecologia 148:144–152PubMedCrossRefGoogle Scholar
  26. Kahmen S, Poschlod P, Friedrich-Schreiber K (2002) Conservation management of calcareous grasslands. Changes in plant species composition and response of functional traits during 25 years. Biol Conserv 104:319–328CrossRefGoogle Scholar
  27. Keller LF, Waller DM (2002) Inbreeding effects in wild populations. Trends Ecol Evol 17:230–241CrossRefGoogle Scholar
  28. Krauss J, Klein AM, Steffan-Dewenter I, Tscharntke T (2004) Effects of habitat area, isolation, and landscape diversity on plant species richness of calcareous grasslands. Biodivers Conserv 13:1427–1439CrossRefGoogle Scholar
  29. Kuiters AT, Huiskes HPJ (2010) Potential of endozoochorous seed dispersal by sheep in calcareous grasslands: correlation with seed traits. Appl Veg Sci 13:163–172CrossRefGoogle Scholar
  30. Legendre P, Legendre L (1998) Numerical ecology, 2nd English edn. Elsevier Science BV, AmsterdamGoogle Scholar
  31. Manzano P, Malo J (2006) Extreme long-distance seed dispersal via sheep. Front Ecol Environ 4:244–248CrossRefGoogle Scholar
  32. Moilanen A, Hanski I (2006) Connectivity and metapopulation dynamics in highly fragmented landscapes. In: Crooks KR, Sanjayan MA (eds) Connectivity conservation. Cambridge University Press, Cambridge, pp 44–71CrossRefGoogle Scholar
  33. Moussie AM, Lengkeek W, Van Diggelen R (2005) Estimating adhesive seed dispersal distances: field experiments and correlated random walks. Funct Ecol 19:478–486CrossRefGoogle Scholar
  34. Murphy HT, Lovett-Doust J (2004) Context and connectivity in plant metapopulations and landscape mosaics: does the matrix matter? Oikos 105:3–14CrossRefGoogle Scholar
  35. Nathan R, Muller-Landau HC (2000) Spatial patterns of seed dispersal, their determinants and consequences for recruitment. Trends Ecol Evol 15:278–285PubMedCrossRefGoogle Scholar
  36. Nathan R, Schurr FM, Spiegel O, Steinitz O, Trakhtenbrot A, Tsoar A (2008) Mechanisms of long-distance seed dispersal. Trends Ecol Evol 23:638–646PubMedCrossRefGoogle Scholar
  37. Orrock JL, Levey DJ, Danielson BJ, Damschen EI (2006) Seed predation, not seed dispersal, explains the landscape-level abundance of an early-successional plant. J Ecol 94:838–845CrossRefGoogle Scholar
  38. Ovaskainen O, Hanski I (2004) Metapopulation dynamics in highly fragmented landscapes. In: Hanski I, Gaggiotti OE (eds) Ecology genetics and evolution of metapopulations. Elsevier Academic Press, Amsterdam, pp 73–104CrossRefGoogle Scholar
  39. Panell JR, Dorken ME (2006) Colonisation as a common denominator in plant metapopulations and range expansions: effects on genetic diversity and sexual systems. Landscape Ecol 21:837–848CrossRefGoogle Scholar
  40. Poschlod P, WallisDeVries MF (2002) The historical and socioeconomic perspective of calcareous grasslands—lessons from the distant and recent past. Biol Conserv 104:361–376CrossRefGoogle Scholar
  41. Poschlod P, Kleyer M, Jackel AK, Dannemann A, Tackenberg O (2003) BIOPOP—a database of plant traits and internet application for nature conservation. Folia Geobot 38:263–271CrossRefGoogle Scholar
  42. Reitalu T, Johansson LT, Sykes MT, Hall K, Prentice HH (2010) History matters: village distances, grazing and grassland species diversity. J Appl Ecol 47:1216–1224CrossRefGoogle Scholar
  43. Rusch G, Fernandez-Palacios JM (1995) The influence of spatial heterogeneity on regeneration by seed in a limestone grassland. J Veg Sci 6:417–426CrossRefGoogle Scholar
  44. Soons MB, Nathan R, Katul GG (2004) Human effects on long-distance wind dispersal and colonization by grassland plants. Ecology 85:3069–3079CrossRefGoogle Scholar
  45. Sork V, Smouse PE (2006) Genetic analysis of landscape connectivity in tree populations. Landscape Ecol 21:821–836CrossRefGoogle Scholar
  46. Taylor PD, Fahrig L, Henein K, Merriam G (1993) Connectivity is a vital element of landscape structure. Oikos 68:571–573CrossRefGoogle Scholar
  47. Taylor PD, Fahrig L, With KA (2006) Landscape connectivity: a return to the basics. In: Crooks KR, Sanjayan MA (eds) Connectivity conservation. Cambridge University Press, Cambridge, pp 31–43Google Scholar
  48. WallisDeVries MF, Poschlod P, Willems JH (2002) Challenges for the conservation of calcareous grasslands in northwestern Europe: integrating the requirements of flora and fauna. Biol Conserv 104:265–273CrossRefGoogle Scholar
  49. Whitlock MC, McCauley DE (1990) Some population genetic consequences of colony formation and extinction: genetic correlations within founding groups. Evolution 44:1717–1724CrossRefGoogle Scholar
  50. Willems JH, Bik LPM (1998) Restoration of high species density in calcareous grassland: the role of seed rain and soil seed bank. Appl Veg Sci 1:91–100CrossRefGoogle Scholar
  51. Wagner HH, Lehnert H, Rico Y, Boehmer HJ (submitted) Ecological network increases functional connectivity of calcareous grasslandsGoogle Scholar
  52. Young AC, Clarke GM (2000) Genetics. demography and viability of fragmented populations, Cambridge University Press, CambridgeGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Yessica Rico
    • 1
  • Hans Juergen Boehmer
    • 2
    • 3
  • Helene H. Wagner
    • 1
  1. 1.Department of Ecology and Evolutionary BiologyUniversity of TorontoMississaugaCanada
  2. 2.Department of Ecology and Ecosystem Management, LOEKTechnical University of MunichFreising-WeihenstephanGermany
  3. 3.Interdisciplinary Latin America Center (ILZ)University of BonnBonnGermany

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