BackgroundIt is well known that species richness and the structure of species assemblages change with latitude, elevation and disturbance. Individual species’ responses to such environmental gradients are unlikely to occur in isolation from other species with which they interact. However, little is known about how and if interaction networks shift with changes in latitude, elevation or disturbance.
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Studies investigating how antagonistic or mutualistic networks of interacting species vary across environmental gradients have used quantitative ‘bipartite’ networks. These networks are constructed from a matrix of antagonistic or mutualistic interactions that incorporates frequencies of occurrence of interactions between pairs of species. Metrics calculated from quantitative networks are less affected by differences in sampling intensity than qualitative networks and are therefore more appropriate for making comparisons across gradients. Quantitative interaction networks structure may change even when there are no accompanying changes in other measures such as species richness and assemblage composition.
The following quantitative network metrics are examples of the kinds often used to summarize interaction network structure:
1) generality - the number of lower level species interacted with by each upper level species
2) vulnerability - the number of upper level species interacted with by each lower level species
3) connectance - the proportion of the potential interactions between levels that are actually observed
4) interaction evenness - the degree to which the frequencies of interactions (counting only pairs of species that do interact) are evenly distributed
Recently, authors focused on review of diet breath (i.e. generality) of herbivorous insect from 13 sites in North, Central, and South America, Papua New Guinea, Japan, and central Europe, and focused on differences in diet breath in temperate and in tropics. They showed that the distribution of specialization shifts globally with latitude, which confirms the long-standing expectation that interactions are more specific at lower latitudes and contributes to our understanding of the latitudinal diversity gradient.
We aim to collect data matrices from all around the globe to investigate ecological networks involving a range of species interactions (e.g. host-parasitoid, plant-herbivore, plant-pollinator...) in relation to a range of different environmental gradients.
1) We will investigate how interaction networks change with latitude. We may expect the interaction networks to be less complicated and less connected in temperate than in tropical regions.
2) We will investigate the same patterns along elevational gradients where we expect the interaction networks to be more complicated in lowlands and less complicated at higher elevations. We expect the patterns observed along latitudinal gradients will be similar to those observed along elevational gradients
3) Finally, we will focus on interaction networks in various habitats that have been modified by humans. The disturbance may lead to less complicated interaction networks, since often species go locally extinct. However, disturbance does not always lead to increased generality as is observed in temperate regions. Therefore, the interaction between the effects of latitude and disturbance on network structure will be very interesting to investigate.
Useful links
If you'd like to read more about global interaction networks, here are some useful links for further reading:
Forister et al. 2015 The global distribution of diet breadth in insect herbivores
Valladares et al. 2006 Habitat Fragmentation Effects on Trophic Processes of Insect-Plant Food Webs
The following quantitative network metrics are examples of the kinds often used to summarize interaction network structure:
1) generality - the number of lower level species interacted with by each upper level species
2) vulnerability - the number of upper level species interacted with by each lower level species
3) connectance - the proportion of the potential interactions between levels that are actually observed
4) interaction evenness - the degree to which the frequencies of interactions (counting only pairs of species that do interact) are evenly distributed
Recently, authors focused on review of diet breath (i.e. generality) of herbivorous insect from 13 sites in North, Central, and South America, Papua New Guinea, Japan, and central Europe, and focused on differences in diet breath in temperate and in tropics. They showed that the distribution of specialization shifts globally with latitude, which confirms the long-standing expectation that interactions are more specific at lower latitudes and contributes to our understanding of the latitudinal diversity gradient.
We aim to collect data matrices from all around the globe to investigate ecological networks involving a range of species interactions (e.g. host-parasitoid, plant-herbivore, plant-pollinator...) in relation to a range of different environmental gradients.
1) We will investigate how interaction networks change with latitude. We may expect the interaction networks to be less complicated and less connected in temperate than in tropical regions.
2) We will investigate the same patterns along elevational gradients where we expect the interaction networks to be more complicated in lowlands and less complicated at higher elevations. We expect the patterns observed along latitudinal gradients will be similar to those observed along elevational gradients
3) Finally, we will focus on interaction networks in various habitats that have been modified by humans. The disturbance may lead to less complicated interaction networks, since often species go locally extinct. However, disturbance does not always lead to increased generality as is observed in temperate regions. Therefore, the interaction between the effects of latitude and disturbance on network structure will be very interesting to investigate.
Useful links
If you'd like to read more about global interaction networks, here are some useful links for further reading:
Forister et al. 2015 The global distribution of diet breadth in insect herbivores
Valladares et al. 2006 Habitat Fragmentation Effects on Trophic Processes of Insect-Plant Food Webs
