All networks are available from the Web of Life repository (www.web-of-life.es), with the exception of the Greenland plant-pollinator networks which are available from Data Dryad (Saavedra et al., 2016). Plant origin data for Mauritius networks was from Kaiser- Bunbury et al., 2009 Appendix II.
References
Albrecht, M., Padrón, B., Bartomeus, I., & Traveset, A. (2014). Consequences of plant invasions on compartmentalization and species’ roles in plant-pollinator
networks. Proceedings of the Royal Society B: Biological Sciences, 281, 20140773. doi:10.1098/rspb.2014.0773
Baker, N. J., Kaartinen, R., Roslin, T., & Stouffer, D. B. (2015). Species’ roles in food webs show fidelity across a highly variable oak forest. Ecography, 38(2), 130–139. doi:10.1111/ecog.00913
Bascompte, J., Jordano, P., Melián, C. J., & Olesen, J. M. (2003). The nested assembly of plant--animal mutualistic networks. Proceedings of the National Academy of Sciences, 100(16), 9383–9387.
Dáttilo, W., Guimarães, P. R., & Izzo, T. J. (2013). Spatial structure of ant-plant
mutualistic networks. Oikos, 122(11), 1643–1648. doi:10.1111/j.1600-0706.2013.00562.x Diestel, R. (2000). Graph Theory (Graduate Texts in Mathematics). Springer-Verlag
New York. doi:10.1109/IEMBS.2010.5626521
Emer, C., Memmott, J., Vaughan, I. P., Montoya, D., & Tylianakis, J. M. (2016). Species roles in plant–pollinator communities are conserved across native and alien ranges. Diversity and Distributions, 22(8), 841–852. doi:10.1111/ddi.12458
validated network of portfolio overlaps and systemic risk. Scientific Reports, 6. doi:10.1038/srep39467
Guillaume, J. L., & Latapy, M. (2004). Bipartite structure of all complex networks. Information Processing Letters, 90(5), 215–221. doi:10.1016/j.ipl.2004.03.007 Kaiser-Bunbury, C. N., Memmott, J., & Müller, C. B. (2009). Community structure of
pollination webs of Mauritian heathland habitats. Perspectives in Plant Ecology, Evolution and Systematics, 11(4), 241–254. doi:10.1016/j.ppees.2009.04.001
Kashtan, N., Itzkovitz, S., Milo, R., & Alon, U. (2004). Topological generalizations of network motifs. Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 70(3), 12. doi:10.1103/PhysRevE.70.031909 Kruskal, J. B. (1964). Multidimensional scaling by optimizing goodness of fit to a
nonmetric hypothesis. Psychometrika, 29(1), 1–27. doi:10.1016/B978-0-12-385157- 4.00313-4
Maruyama, P. K., Vizentin-Bugoni, J., Sonne, J., Martín González, A. M., Schleuning, M., Araujo, A. C., … Dalsgaard, B. (2016). The integration of alien plants in
mutualistic plant-hummingbird networks across the Americas: The importance of species traits and insularity. Diversity and Distributions, 22(6), 672–681.
doi:10.1111/ddi.12434
Milo, R., Shen-Orr, S., Itzkovitz, S., Kashtan, N., Chklovskii, D., & Alon, U. (2002). Network motifs: simple building blocks of complex networks. Science, 298(5594), 824–827.
Minchin, P. R. (1987). An evaluation of the relative robustness of techniques for ecological ordination. Vegetatio, 69(1–3), 89–107. doi:10.1007/BF00038690 Newman, M. E. . (2010). Networks. An introduction. Oxford University Press.
doi:10.1111/j.1468-5922.2010.01872_2.x
Oksanen, J., Blanchet, F. G., Friendly, M., Kindt, R., Legendre, P., McGlinn, D., … Wagner, H. (2016). vegan: Community Ecology Package. R package version 2.4-0. Olesen, J. M., Bascompte, J., Elberling, H., & Jordano, P. (2008). Temporal dynamics in
a pollination network. Ecology, 89(6), 1573–1582. doi:10.1890/07-0451.1
Ordonez, A., Wright, I. J., & Olff, H. (2010). Functional differences between native and alien species: A global-scale comparison. Functional Ecology, 24(6), 1353–1361. doi:10.1111/j.1365-2435.2010.01739.x
Poisot, T., & Stouffer, D. (2016). How ecological networks evolve. BioRxiv. Retrieved from http://biorxiv.org/content/early/2016/08/29/071993.abstract
Rodríguez-Rodríguez, M. C., Jordano, P., & Valido, A. (2017). Functional consequences of plant-animal interactions along the mutualism-antagonism gradient. Ecology, 98(5), 1266–1276. doi:10.1002/ecy.1756
Saavedra, S., Rohr, R. P., Olesen, J. M., & Bascompte, J. (2016). Data from: Nested species interactions promote feasibility over stability during the assembly of a pollinator community. Ecology and Evolution. Dryad Digital Repository. doi:doi:10.5061/dryad.3pk73
Saracco, F., Di Clemente, R., Gabrielli, A., & Squartini, T. (2015). Randomizing bipartite networks: the case of the World Trade Web. Scientific Reports, 5, 10595. Retrieved from http://dx.doi.org/10.1038/srep10595
Saracco, F., Di Clemente, R., Gabrielli, A., & Squartini, T. (2016). Detecting early signs of the 2007-2008 crisis in the world trade. Scientific Reports, 6.
doi:10.1038/srep30286
Simmons, B. I., Cirtwill, A. R., Baker, N. J., Wauchope, H. S., Dicks, L. V., Stouffer, D. B., & Sutherland, W. J. (2018). Motifs in bipartite ecological networks: uncovering indirect interactions. Oikos, (in press). doi:10.1111/oik.05670
Simmons, B. I., Sutherland, W. J., Dicks, L. V, Albrecht, J., Farwig, N., García, D., … González-Varo, J. P. (2018). Moving from frugivory to seed dispersal:
incorporating the functional outcomes of interactions in plant-frugivore networks. Journal of Animal Ecology.
Vázquez, D. P., Morris, W. F., & Jordano, P. (2005). Interaction frequency as a
surrogate for the total effect of animal mutualists on plants. Ecology Letters, 8(10), 1088–1094. doi:10.1111/j.1461-0248.2005.00810.x
Discussion
The projects in this thesis were mostly conducted independently, rather than as part of a sequential progression, and thus it is useful to first summarise the key findings of each chapter.
Chapter 1: A large proportion of interactions in plant-frugivore visitation networks are non-mutualistic. These networks are a good proxy for true seed dispersal networks when considering whole-network structure, but less so for species-level structure.
Chapter 2: The widespread positive relationship between abundance and generalisation in mutualistic networks appears to be unidirectional, with abundance driving generalisation rather than the other way round. Despite the importance of morphological matching in governing plant-hummingbird interactions, neutral effects also play a role.
Chapter 3: The mutualistic interactions which are most vulnerable to extinction are also those which contribute most to the stability of a network. Moreover, for many interactions, vulnerability and contribution to stability are determined by the identity of the taxa involved in the interaction, rather than ecological context. This means that the vulnerability and contribution to stability of an interaction is similar across different networks, implying a form of evolutionary conservatism.
Chapter 4: Indices are a useful tool to characterise network structure and species roles within networks, but we need to be aware of their limitations. Other methods of characterising network structure, like motifs, are less lossy and could be particularly useful for questions concerning interaction turnover or species roles.
Chapter 5: Counting motifs in bipartite networks, or counting the number of times species occur in unique positions within motifs, can be done quickly in R, MATLAB and Python. There is preliminary evidence that invasive species may occupy a single ‘invader role’ in mutualistic networks.