THE EFFECTS OF MULTIPLE FACTORS ON VIABILITY SELECTION IN HYLA GRATIOSA TADPOLES

Area of Science:

• Ecology
• Evolutionary Biology
• Amphibian Biology

Background:

• Understanding how ecological factors influence survival and selection is crucial for evolutionary studies.
• Predator-prey dynamics and density-dependent effects are key factors shaping population dynamics in amphibians.

Purpose of the Study:

• To investigate the effects of predator presence and tadpole density on the survival and growth of Hyla gratiosa larvae.
• To examine the interaction between ecological conditions and genetic variation in determining larval survival.

Main Methods:

• Field enclosures were used to simulate twelve ecological conditions, varying predator (dragonfly, salamander) presence and tadpole densities (8, 16, 32).
• Two full sib families of Hyla gratiosa larvae were compared across these conditions, with five replicates per treatment.
• Survival rates and body size differences were analyzed using a 2x2x3 variance analysis design.

Main Results:

• Predator presence reduced overall larval survival by 24%, with additive effects from both dragonfly and salamander predators.
• Salamander predation effects were density-dependent, impacting survival only at higher tadpole densities (16 and 32 larvae).
• Differential survival between sibships was linked to body size, but the relationship varied ecologically, indicating mediated selection.

Conclusions:

• Ecological factors like predator abundance and conspecific density interact, influencing mortality rates and trait-fitness relationships.
• Selection pressures are not isolated; their combined effects on fitness components vary with ecological conditions.
• A comprehensive understanding of ecological interactions is essential for accurately predicting selection in natural populations.