Changes in arthropod communities as Avicennia germinans expands into Gulf of Mexico salt marshes

Climate change is driving poleward shifts in species distributions worldwide. In the Gulf of Mexico (GOM), warming temperatures are allowing cold sensitive black mangroves (Avicennia germinans) to move north into coastal wetlands that have previously been dominated by the marsh grass Spartina alterniflora. Avicennia germinans in the western GOM become established in upper tidal elevations, creating dense monocultures and replacing S. alterniflora and other wetland plants (e.g., Salicornia virginica, Batis maritima). I investigated insect community assemblages in wetlands with and without A. germinans to assess potential effects of A. germinans expansion on insect fauna. Insect abundance, biomass, richness, diversity, and community and feeding guild composition were measured in both the spring and the fall across varying levels of A. germinans abundance and at low and high tidal elevations. Insects were more abundant and had larger biomass contributions in both the spring and the fall in upper tidal elevation wetlands where A. germinanss have yet to become established. Richness and diversity were not different in any of the wetland types or tidal elevations, however multivariate analysis indicated significant differences in community structure in the wetlands without A. germinans. Feeding guild composition was also different; wetlands containing A. germinans monocultures had less predator biomass. Thus, shifting vegetation brought on by climate change can alter insect communities in coastal wetlands, illustrating the need for a more comprehensive understanding of climate change effects on fauna in response to shifting foundation species.