Latitudinal variation in plant–herbivore interactions in European salt marshes

Abstract

Ecological interactions often vary geographically. Work in salt marshes on the Atlantic Coast of the United States has documented community-wide latitudinal gradients in plant palatability and plant traits that may be driven in part by greater herbivore pressure at low latitudes. To determine if similar patterns exist elsewhere, we studied six taxa of saltmarsh plants (Atriplex , Juncus , Limonium , Salicornia , Spartina and Suaeda ) at European sites at high (Germany and the Netherlands) and low (Portugal and Spain) latitudes. We conducted feeding assays using both native and non-native consumers, and documented patterns of herbivore damage in the field. As in the United States, high-latitude plants tended to be more palatable than low-latitude plants when offered to consumers in paired feeding assays in the laboratory, although assays with grasshopper consumers were less consistent than those with crab consumers, and plants in the field at low-latitude sites tended to experience greater levels of herbivore pressure than plants at high-latitude sites. Similarly, high-latitude leaf litter was more palatable than litter from low-latitude plants when offered to consumers in paired feeding assays in the laboratory. Latitudinal gradients in plant palatability and herbivore pressure may be a general phenomenon, and may contribute to latitudinal gradients in decomposition processes.

Do Spur-Throated Grasshoppers, Melanoplus spp. (Orthoptera: Acrididae), Exert Top-Down Control on Smooth Cordgrass Spartina alterniflora in Northern New England?

“…These results contrast the results of the southeast Atlantic marshes of the US that demonstrate strong consumer control of S. alterniflora (Silliman and Zieman 2001;Silliman and Bertness 2002). Similarly, a latitudinal gradient exists in plant palatability in the marshes of Europe and the US where northern plants are more palatable (more nitrogen content, less chemical defenses) than southern plants because of historically greater herbivore pressure at lower latitudes (Pennings et al , 2007Siska et al 2002). Pennings and Silliman (2005) suggest that a latitudinal gradient exists along the Atlantic coast of the US where impacts of leaf-chewing herbivores on S. alterniflora are stronger at lower than higher latitudes.…”

Is There a Latitudinal Gradient in the Importance of Biotic Interactions?

“…In the case of Spartina alterniflora, southern plants also suffer more herbivore damage, although the diversity and density of dominant leaf-chewing consumers changed little with latitude (Pennings & Silliman 2005). Trends similar to those observed in the United States were also found in European salt marshes (Pennings et al 2007). …”

Weevils and camellias in a Darwin's race: model system for the study of eco‐evolutionary interactions between species

“…For example, intertidal gastropods are exposed to more severe predation pressure in tropics than in temperate seas (Vermeij 1977;Bertness et al 1981) and hence various defensive features of gastropod shells have evolved at lower latitudes (Vermeij 1974(Vermeij , 1976. Likewise, across the coastal latitudinal gradients in North America and Europe, saltmarsh plants are exposed to greater herbivore pressure at lower latitudes (Pennings and Silliman 2005;Pennings et al 2007) and the plants were less palatable to herbivores at lower latitudinal regions (Pennings et al 2001). Thus, considering that the weevil-camellia interaction was also characterized by the existence of greater armament at lower latitudes (Toju and Sota 2006a, b), antagonistic coevolution in general may show a similar geographic pattern along latitude (i.e., more escalated state of arms race coevolution at lower latitudes).…”