Intrinsic microhabitat preference promotes coexistence in two competing intertidal hermit crabs

Area of Science:

• Marine Biology
• Ecology
• Behavioral Ecology

Background:

• Environmental complexity creates fine-scale spatial variation, enabling species to utilize distinct microhabitats and coexist.
• Mixed intertidal shores offer high habitat heterogeneity, influencing benthic organism distribution based on microhabitat preferences and competitive interactions.

Purpose of the Study:

• To investigate how social conditions, specifically competition with conspecifics and heterospecifics, influence microhabitat use in two competing intertidal hermit crab species.
• To determine species-specific microhabitat preferences in the absence of competition and assess how these preferences are modified by competitive pressures and density.

Main Methods:

• Assessed microhabitat preferences of two hermit crab species (Clibanarius albidigitus and Calcinus californiensis) across four distinct microhabitats (sand, upper rock, under-rock, exposed rock) under solitary conditions.
• Evaluated changes in microhabitat use when exposed to conspecific and heterospecific competitors at varying densities.

Main Results:

• Clibanarius albidigitus preferred upper submerged rock surfaces, while Calcinus californiensis favored under-rock microhabitats; both avoided sand and exposed rock.
• Calcinus californiensis's microhabitat use remained largely unaffected by competition.
• Clibanarius albidigitus used its preferred habitat less under intraspecific competition but was unaffected by interspecific competition.

Conclusions:

• Contrasting microhabitat preferences between the two hermit crab species significantly limit direct interspecific competition.
• Habitat segregation is primarily driven by environmental conditions and intrinsic species preferences, rather than direct interference competition.
• Population density has minimal influence on the spatial organization and microhabitat use of these hermit crab species.