Species-area and network-area relationships in host–helminth interactions

Abstract

The scaling relationship observed between species richness and the geographical area sampled (i.e. the species-area relationship (SAR)) is a widely recognized macroecological relationship. Recently, this theory has been extended to trophic interactions, suggesting that geographical area may influence the structure of species interaction networks (i.e. network-area relationships (NARs)). Here, we use a global dataset of host–helminth parasite interactions to test existing predictions from macroecological theory. Scaling between single locations to the global host–helminth network by sequentially adding networks together, we find support that geographical area influences species richness and the number of species interactions in host–helminth networks. However, species-area slopes were larger for host species relative to their helminth parasites, counter to theoretical predictions. Lastly, host–helminth network modularity—capturing the tendency of the network to form into separate subcommunities—decreased with increasing area, also counter to theoretical predictions. Reconciling this disconnect between existing theory and observed SAR and NAR will provide insight into the spatial structuring of ecological networks, and help to refine theory to highlight the effects of network type, species distributional overlap, and the specificity of trophic interactions on NARs.

Spatial scaling of soil microbial co‐occurrence networks in a fragmented landscape

“…Specifically, network size, total links, average degree, relative modularity, and the number of keystone OTUs were all significantly higher on larger islands. These results are consistent with studies of food webs and mutualism networks of macro-organisms 5,6,26,29 . For instance, Galiana et al found that the complexity (network size, links, and links per species) of food webs scaled positively with area in both theoretical simulations and empirical observations 4,6 .…”

Hierarchical compound topology uncovers complex structure of species interaction networks

“…Here, we analyse how networks vary in several properties simultaneously (Pinheiro et al, 2019; Thébault & Fontaine, 2010), without rescaling nestedness and modularity using null models that are based on the other network properties (Dallas & Jordano, 2021; Felix et al, 2022). This decision follows from the understanding that ecological and evolutionary processes shape interaction networks as a whole and that, by combining properties, we may achieve deeper insights into these processes (Guimarães, 2020; Segar et al, 2020).…”

Parasite species richness and host range are not spatially conserved

“…This is an inherent limitation, one which must be considered as how host–helminth associations change across the coarsely defined geographical range of host and parasite species. However, these data represent a herculean effort to compile, curate and distribute > 250,000 host–helminth associations distributed around the world (Gibson et al., 2005), creating opportunities to explore macroecological patterns in host–parasite associations (Dallas et al., 2018, 2019; Dallas & Becker, 2021; Dallas & Jordano, 2021b; Dallas & Poisot, 2018). Efforts are being made to aggregate and curate species interaction network data from individual studies at finer spatial scales (e.g., Poisot et al.…”

“…However, these data represent a herculean effort to compile, curate and distribute > 250,000 host-helminth associations distributed around the world (Gibson et al, 2005), creating opportunities to explore macroecological patterns in host-parasite associations (Dallas et al, , 2019Dallas & Becker, 2021;Dallas & Jordano, 2021b;Dallas & Poisot, 2018). Efforts are being made to aggregate and curate species interaction network data from individual studies at finer spatial scales (e.g., Poisot et al (2016)), but even these collections suffer from some of the same geographical coverage biases present in the host-helminth association data used here (Poisot et al, 2021).…”

“…Hence, we have included aquatic and marine locations in our analyses. For more information on the host-helminth interaction data, see Carlson et al (2020), Dallas (2016), Dallas et al (2019), Dallas and Jordano (2021b) and Gibson et al (2005).…”