Plant assemblages are affected by connectivity and dispersal mode

Dandelion seed dispersal

Plant seeds are dispersed by numerous vectors, whose response to landscape connectivity can differ by habitat type.

Experimental corridors have shown that connectivity has a major impact on plant diversity in fragmented landscapes over the long term. However, empirical studies are not always as straight-forward; some show a positive effect of connectivity on richness or composition, while others show a neutral or even negative effect.  This may be in part due to the number of ways that connectivity can be measured (for example, functional vs. structural connectivity) or how values of connectivity are assigned.  For plants, the perception of connectivity and its benefits can be influenced by the numerous methods of dispersal as well.

A new study aims to examine how connectivity across three types of habitat (woodland, temporary grassland, and wheat cropland) affects plant assemblage according to their dispersal mode (animal, wind, and unassisted). Using resistance maps to calculate connectivity, the authors looked at plant assemblages in 25 patches of each habitat type scattered across the LTSER site “Zone Atelier Armorique” in Brittany, western France.  Within each patch, herbaceous plants were sampled across multiple quadrats and classified according to dispersal type.  Connectivity between patches was modeled using circuit theory.

Fields and Woodland near Bottomstead Farm

Plants may take advantage of more than one dispersal pathway in highly fragmented landscapes. (© Pam Brophy)

The surveys showed that plant assemblages in temporary grasslands and woodlands were dependent on landscape connectivity, but those in wheat croplands were not. Plant species that are animal-dispersed responded to connectivity, but wind-dispersed and unassisted species did not.  Interestingly, plant assemblage was affected via dispersal by connectivity provided by the same habitat type as well as connectivity provided by other habitat types.

This study influences the perspective of how plants assemble by suggesting that plants might supplement their dispersal through habitats of the same type by also using other types of habitats.  Landscape connectivity within and among different habitat types is significant for more than just species within each habitat type. In fragmented agricultural landscapes, understanding how plant populations stay connected across a diverse landscape can help maintain biodiversity through better connectivity.

Resources

Uroy, L., Mony, C. and Ernoult, A. 2019. Additive effects of connectivity provided by different habitat types drive plant assembly. Scientific Reports 9: 13952.

Damschen, E.I., Brudvig, L.A., Burt, M.A., Fletcher, R.J., Haddad, N.M., Levey, D.J., Orrock, J.L., Resasco, J. and Tewksbury, J.J. 2019. Ongoing accumulation of plant diversity through habitat connectivity in an 18-year experiment. Science 365(6460): 1478-1480.
2019-11-27T15:05:24-05:00 November 25th, 2019|

About the Author:

Heather Cayton
Heather Cayton is the Managing Director of ConservationCorridor.org and a Research Assistant at Michigan State University. She received her B.S. from the University of Virginia and her M.S. from Virginia Tech, and has spent over 10 years studying corridors and rare butterflies in North Carolina.