Specialized Interaction Decreases in Tropical Latitudes

1. Specialized Interaction Decreases in Tropical Latitudes Benjamin Fields Julia Frederick Cecilia Ireland Christina Kirkman NeomiSanghrajka

2. Introduction • Latitudinal Specialization Debate • Tropics vs. Temperate Regions • Mutualism of plants and animal pollinators/seed dispersers • Specialization with regard to latitudes, contemporary vs. past climate, regional plant diversity • —Latitudinal specialization gradient reversed relative to latitudinal diversity gradient

3. Latitudinal Specialization Gradient • 1st Step: Gathering of global data set comprising a total of 282 quantitative pollination (red) and seed dispersal (blue) networks ranging in absolute latitude from 0° to 82°

4. 2nd Step: Comparison of the mutualistic interactions between the pollinators and seed dispersers and the plants they interact with. • Pollinators shown on top, plants on bottom generalized pollination network with functionally redundant pollinators specialized pollination network with functionally distinct pollinators

5. The specialization of the interacting species was estimated by assessing patterns of niche partitioning and resource overlap among pollinator or seed disperser species. • Recent advances in the analysis of quantitative interaction networks show that network-wide interactions are more specialized in species-rich tropical communities. This idea is challenged by the authors of this article and the reverse is proved about the mutualistic interactions involving mobile pollinators and seed dispersers in the tropics and non-tropics.

6. Effects of Climate & Plant Diversity • Past climate stability and contemporary climate have been thought to influence biotic specialization. • Past Climate Stability • reflects the temporal stability of local communities • shows the available time for coevolution • Contemporary Climate • Cumulative annual temperature is closely related to evapotranspiration. • Could be mediated by increases in plant diversity in warm climates because it would reduce relative abundances and densities of resource species

7. Seed dispersal networks increased with increasing climate-change velocity. • In regions with more stable climates seed dispersal systems have become more generalized • Pollination networks were not affected by the climate-change velocity. • Contemporary climate effect is much stronger than • that of past climate stability. • Current conditions have stronger influences associated among consumer and resource species in mutualistic networks. • Network specialization decreases with increasing plant diversity both regionally and locally.

8. The latitudinal gradient is even stronger than the overall plant diversity gradient with respect to the diversity of animal-pollinated flowers and animal dispersed fruits. • Increasing plant diversity in the tropics is associated with: • a wider range of resource traits • a larger number of distinct pollination systems • A key feature of the generalization of consumer species in mutualistic networks is high resource diversity.

9. Influence of Guild Structure • Guild: a group of species that use the same resources • Not necessarily in the same niche • Species in the tropics are of a different guild than those in temperate regions. • The inter-species relations of the tropics appear to be more generalized than those of temperate regions. • Because the way tropical communities function, more species interact with more species.

10. Influence of Guild Structure • Frugivores of the tropics disperse a more diverse group of seeds than do the omnivores of the temperate regions. • Fruit available year-round (due to the warm climate). • Diet of fruit has more species richness in the tropics. • Tropical pollinators live longer than those found in temperate climates. • They have a larger window of time to pollinate more kinds of plants. • Some pollination is redundant.

11. Conclusions Absolute latitude [degrees] Red: Pollination Blue: Seed dispersal

12. Conclusions • Evolution will cause • In the Tropical Ecosystems • In the Temperate Ecosystems • Relationship to the Graph

13. Take Home Message • The pattern found was that the specialization of both pollination and seed dispersal networks decreased as the regions got closer to the tropics.

14. Works Cited • Kissling, W.D., Bohning-Gaese, K., and Jetz, W. (2009). The global distribution of frugivory in birds. Glob. Ecol. Biogeogr. 18, 150–162. • Schleuninget al., Specialization of Mutualistic Interaction Networks Decreases toward Tropical Latitudes, Current Biology (2012), http://dx.doi.org/10.1016/j.cub.2012.08.015 • Scott Freeman. Biological Science, Fourth Edition. San Francisco: Pearson Education, Inc. 2011.