This document discusses the role of network structure in community stability. It first notes that previous research found that nested network structures confer stability, but that species contributing most to nestedness are also more likely to go extinct. The document then outlines a plan to empirically evaluate these expectations using stability measures and analyses of nestedness contributions. It reviews different study designs and findings on pollinator responses to land use change. The goal is to map nestedness and extinction patterns worldwide to better understand what drives extinction order and how this relates to network structure.

1. An empirical evaluation of the role of
network structure for community stability
Ignasi Bartomeus
www.bartomeuslab.com
nacho.bartomeus@gmail.com
@ibartomeus

4. WHY?

6. 1) nestedness confer stability in mutualistic networks

7. Thebault and Fontaine 2006. Science, Lever et al. 2014 Ecol. Let.

17. 2) Species contributing most to nestedness
are more likely to go extinct

18. Saavedra et al. 2011 Nature; 2013 Nature comm.

19. Confront expectations with data!

20. How?

21. ? ?
?
?
?
? ?
?
?
?
300 to 3,000 m radius
a
b
? ?
Figure 3
Schematic showing the two study designs contrasted in this review. (a) Design focused on surrounding
landscape cover. Sampling is generally done within a fixed habitat type. In the most common design, sites
vary in the proportion of surrounding land cover composed of specific habitat types such as forest (dark green)
or agriculture ( yellow). The radius at which landscape cover is assessed varies across studies but is typically
between 300 and 3,000 m. Other designs, which we include in this category, vary either the linear distance to
the nearest habitat patch or the area of the habitat patch. (b) Design focused on local land-use type.These
studies compare pollinator communities among different habitat types. The surrounding landscape cover
and the spatial extent of the habitat type where pollinators are sampled are generally not reported.
Figure 4)]. Bees and butterflies both show strong negative responses to land-use change in extreme
systems, butmoremixed responses inmoderate systems (Supplemental Tables 2 and 3). Extreme
land use causes a strong decrease in abundance and/or richness (e.g., Aizen & Feinsinger 1994,
Koh & Sodhi 2004, Kremen et al. 2002, Ockinger & Smith 2006), whereas studies in moderately
anthropogenic landscapes find more varied responses (e.g., Bartomeus et al. 2010, Bergman et al.
2008).
Stability measures
(e.g. species loss speed)
Study designs that make comparisons across habitat types, rather than across landscape gra-dients,
find even fewer negative effects, and responses are predominantly positive for most taxa
(Supplemental Table 4). For bees, the ratio of negative-to-positive responses decreases from
8.2 for extreme landscape studies to 2.0 for moderate landscape studies, to 0.5 for across-habitat
comparisons. For butterflies, the ratios decrease from 6.0 to 3.0 to 1.1, respectively (Supple-mental
Tables 2–4). The responses of syrphid flies and vertebrates are difficult to interpret
due to the limited number of landscape-scale studies that have been conducted (Supplemental
Tables 2 and 3).
The reason why pollinator abundance and/or richness often decrease with increasing human
land use in the surrounding landscape, but increase with conversion of natural to anthropogenic
8 Winfree·Bartomeus ·Cariveau
Annu. Rev. Ecol. Evol. Syst. 2011.42:1-22. Downloaded from www.annualreviews.org
? ?
by 67.139.62.82 on 11/18/11. For personal use only.
?
?
?
?
?
?
300 to 3,000 m radius
a
b
Figure 3
Schematic showing the two study designs contrasted in this review. (a) Design focused on surrounding
landscape cover. Sampling is generally done within a fixed habitat type. In the most common design, sites
the proportion of surrounding land cover composed of specific habitat types such as forest (dark green)
agriculture ( yellow). The radius at which landscape cover is assessed varies across studies but is typically
between 300 and 3,000 m. Other designs, which we include in this category, vary either the linear distance to
nearest habitat patch or the area of the habitat patch. (b) Design focused on local land-use type.These
compare pollinator communities among different habitat types. The surrounding landscape cover
the spatial extent of the habitat type where pollinators are sampled are generally not reported.
Figure 4)]. Bees and butterflies both show strong negative responses to land-use change in extreme
systems, butmoremixed responses inmoderate systems (Supplemental Tables 2 and 3). Extreme
use causes a strong decrease in abundance and/or richness (e.g., Aizen & Feinsinger 1994,
& Sodhi 2004, Kremen et al. 2002, Ockinger & Smith 2006), whereas studies in moderately
anthropogenic landscapes find more varied responses (e.g., Bartomeus et al. 2010, Bergman et al.
2008).
Study designs that make comparisons across habitat types, rather than across landscape gra-dients,
find even fewer negative effects, and responses are predominantly positive for most taxa
Supplemental Table 4). For bees, the ratio of negative-to-positive responses decreases from
for extreme landscape studies to 2.0 for moderate landscape studies, to 0.5 for across-habitat
comparisons. For butterflies, the ratios decrease from 6.0 to 3.0 to 1.1, respectively (Supple-mental
Tables 2–4). The responses of syrphid flies and vertebrates are difficult to interpret
to the limited number of landscape-scale studies that have been conducted (Supplemental
Tables 2 and 3).
The reason why pollinator abundance and/or richness often decrease with increasing human
use in the surrounding landscape, but increase with conversion of natural to anthropogenic
·Bartomeus ·Cariveau

22. ? ?
? ?
? ?
+ + =
Metaweb
?
?
?
?
?
?
300 to 3,000 m radius
a
b
Figure 3
Schematic showing the two study designs contrasted in this review. (a) Design focused on surrounding
landscape cover. Sampling is generally done within a fixed habitat type. In the most common design, sites
vary in the proportion of surrounding land cover composed of specific habitat types such as forest (dark green)
or agriculture ( yellow). The radius at which landscape cover is assessed varies across studies but is typically
between 300 and 3,000 m. Other designs, which we include in this category, vary either the linear distance to
the nearest habitat patch or the area of the habitat patch. (b) Design focused on local land-use type.These
studies compare pollinator communities among different habitat types. The surrounding landscape cover
and the spatial extent of the habitat type where pollinators are sampled are generally not reported.
Figure 4)]. Bees and butterflies both show strong negative responses to land-use change in extreme
systems, butmoremixed responses inmoderate systems (Supplemental Tables 2 and 3). Extreme
land use causes a strong decrease in abundance and/or richness (e.g., Aizen & Feinsinger 1994,
Koh & Sodhi 2004, Kremen et al. 2002, Ockinger & Smith 2006), whereas studies in moderately
anthropogenic landscapes find more varied responses (e.g., Bartomeus et al. 2010, Bergman et al.
2008).
Study designs that make comparisons across habitat types, rather than across landscape gra-dients,
find even fewer negative effects, and responses are predominantly positive for most taxa
(Supplemental Table 4). For bees, the ratio of negative-to-positive responses decreases from
8.2 for extreme landscape studies to 2.0 for moderate landscape studies, to 0.5 for across-habitat
comparisons. For butterflies, the ratios decrease from 6.0 to 3.0 to 1.1, respectively (Supple-mental
Tables 2–4). The responses of syrphid flies and vertebrates are difficult to interpret
due to the limited number of landscape-scale studies that have been conducted (Supplemental
Tables 2 and 3).
The reason why pollinator abundance and/or richness often decrease with increasing human
land use in the surrounding landscape, but increase with conversion of natural to anthropogenic
8 Winfree·Bartomeus ·Cariveau
Annu. Rev. Ecol. Evol. Syst. 2011.42:1-22. Downloaded from www.annualreviews.org
? ?
by 67.139.62.82 on 11/18/11. For personal use only.
?
?
?
?
?
?
300 to 3,000 m radius
a
b
Figure 3
Schematic showing the two study designs contrasted in this review. (a) Design focused on surrounding
landscape cover. Sampling is generally done within a fixed habitat type. In the most common design, sites
the proportion of surrounding land cover composed of specific habitat types such as forest (dark green)
agriculture ( yellow). The radius at which landscape cover is assessed varies across studies but is typically
between 300 and 3,000 m. Other designs, which we include in this category, vary either the linear distance to
nearest habitat patch or the area of the habitat patch. (b) Design focused on local land-use type.These
compare pollinator communities among different habitat types. The surrounding landscape cover
the spatial extent of the habitat type where pollinators are sampled are generally not reported.
Figure 4)]. Bees and butterflies both show strong negative responses to land-use change in extreme
systems, butmoremixed responses inmoderate systems (Supplemental Tables 2 and 3). Extreme
use causes a strong decrease in abundance and/or richness (e.g., Aizen & Feinsinger 1994,
& Sodhi 2004, Kremen et al. 2002, Ockinger & Smith 2006), whereas studies in moderately
anthropogenic landscapes find more varied responses (e.g., Bartomeus et al. 2010, Bergman et al.
2008).
Study designs that make comparisons across habitat types, rather than across landscape gra-dients,
find even fewer negative effects, and responses are predominantly positive for most taxa
Supplemental Table 4). For bees, the ratio of negative-to-positive responses decreases from
for extreme landscape studies to 2.0 for moderate landscape studies, to 0.5 for across-habitat
comparisons. For butterflies, the ratios decrease from 6.0 to 3.0 to 1.1, respectively (Supple-mental
Tables 2–4). The responses of syrphid flies and vertebrates are difficult to interpret
to the limited number of landscape-scale studies that have been conducted (Supplemental
Tables 2 and 3).
The reason why pollinator abundance and/or richness often decrease with increasing human
use in the surrounding landscape, but increase with conversion of natural to anthropogenic
·Bartomeus ·Cariveau
Overall structure
(e.g. nestedness)
Stability measures
(e.g. species loss speed)

23. Map worldwide.

24. 2) Species contributing most to nestedness
are more likely to go extinct

25. Each node nestedness
contribution
Permutation of the
node values

26. Each node nestedness
contribution Each node real loss order
Permutation of the Rank of extinction
node values
Sites
Pollinators
ES42CH01-Winfree ARI 26 September 2011 12:49
ES42CH01-Winfree ARI 26 September 2011 12:49
? ?
300 to 3,000 m radius
a
b
? ?
?
?
?
?
?
?
300 to 3,000 m radius
a
b
Figure 3
Schematic showing the two study designs contrasted in this review. (a) Design focused on surrounding
landscape cover. Sampling is generally done within a fixed habitat type. In the most common design, sites
vary in the proportion of surrounding land cover composed of specific habitat types such as forest (dark green)
or agriculture ( yellow). The radius at which landscape cover is assessed varies across studies but is typically
between 300 and 3,000 m. Other designs, which we include in this category, vary either the linear distance to
the nearest habitat patch or the area of the habitat patch. (b) Design focused on local land-use type.These
studies compare pollinator communities among different habitat types. The surrounding landscape cover
and the spatial extent of the habitat type where pollinators are sampled are generally not reported.
Figure 4)]. Bees and butterflies both show strong negative responses to land-use change in extreme
systems, butmoremixed responses inmoderate systems (Supplemental Tables 2 and 3). Extreme
land use causes a strong decrease in abundance and/or richness (e.g., Aizen & Feinsinger 1994,
Koh & Sodhi 2004, Kremen et al. 2002, Ockinger & Smith 2006), whereas studies in moderately
anthropogenic landscapes find more varied responses (e.g., Bartomeus et al. 2010, Bergman et al.
2008).
Study designs that make comparisons across habitat types, rather than across landscape gra-dients,
find even fewer negative effects, and responses are predominantly positive for most taxa
Annu. Rev. Ecol. Evol. Syst. 2011.42:1-22. Downloaded from www.annualreviews.org
by 67.139.62.82 on 11/18/11. For personal use only.
+ +

27. For deciduous forests in US:
Rachael Winfree

28. What drives extinction order then?

29. What drives extinction order then?
More in Winfree et al. 2014 Am. Nat.

30. 1) nestedness confer stability

31. Nestedness
Relative nestedness (NODF)

32. Nestedness % Links lost at
50% habitat destruction
50% habitat loss
% links loss
Relative nestedness (NODF)
+ +

33. link loss at 50% habitat loss

34. ?
link loss at 50% habitat loss

35. This project is been possible thanks to...
Data providers: Rachael Winfree, Dan Cariveau, Laura Burkle,
Marie Winsa, Marcelo Aizen, Jennifer Wickens, Andrea Holzchuh,
Juanpe Gonzalez-Varo, …
but also to theory developers.
Thank you @ibartomeus
www.bartomeuslab.com
nacho.bartomeus@gmail.com

36. ?
Thank you @ibartomeus
www.bartomeuslab.com
nacho.bartomeus@gmail.com

38. What models do not take into account: Complexity!
Species have different levels of dependencies on its partners
Species may be regulated by other factors (e.g. nest sites)
…
Not a critique to the models/mechanisms,
but to its relevance in real ecosystem.

39. What empirical data does not takes into account:
Sampling artefacts
Lack of measures of stability
…
(But see Bartomeus 2013 PLoS ONE)
Not a critique to the observational studies,
but to its ability to detect the signal.