Drought alters the spatial distribution, grazing patterns, and radula morphology of a fungal-farming salt marsh snail

• Climate change is altering consumer− plant interactions in ecosystems worldwide. How consumers alter their spatial distribution, grazing activities, and functional morphology in response to climate stress can determine whether their effects on plants intensify or relax. Few studies have considered multiple consumer response metrics to elucidate the mechanisms underpinning the resulting changes in consumer− plant interactions. Here, we tested how drought stress influences the interaction between the dominant consumer, the fungal-farming periwinkle snail Littoraria irrorata, and a foundational plant, cordgrass Spartina alterniflora, in a southeastern US salt marsh. In a 4 mo field experiment, we maintained moderate snail densities in mesh control chambers and clear plastic climate chambers that simulated drought by elevating temperatures and drying soils. Monitoring revealed that snails more often congregated on cordgrass stems than leaves in climate chambers than in controls. Image analyses indicated that this behavioral shift corresponded to snails inflicting shorter, but more numerous, fungal-infested scars on cordgrass leaves, and causing less plant damage in climate chambers than controls. Coincident with their net reduction in grazing, snails maintained longer radulae, whose central teeth were blunter and lateral teeth were sharper, in climate chambers compared to controls. These results suggest that under drought, snail radulae may experience less frictional wear and that, at intermediate densities, snail−cordgrass interactions relax. Together with prior research showing that at high densities, snails can denude cordgrass during drought, we conclude that con-Saltmarsh snails (top left) stressed by drought conditions show reduced radula wear and shifts in tooth morphology (e.g. sharper lateral teeth; bottom right), suggesting that fewer resources are invested in maintaining the grazing apparatus. Climate change is expected to increase drought stress. © The authors 2019.

Subject headings

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

Climate change

Coastal wetland

Herbivory

Littorariairrorata

Spartinaalterniflora

drought stress

functional morphology

fungus

grass

grazing

morphology

saltmarsh

snail

spatial distribution

United States

Gastropoda

Littoraria irrorata

Spartina

Spartina alterniflora

Publication and Content Type

ref (subject category)

art (subject category)