Asymmetric interference competition and niche partitioning between native and invasive Anolis lizards

Area of Science:

• Ecology
• Behavioral Ecology
• Community Ecology

Background:

• Species coexistence relies on understanding competition mechanisms: interference (direct aggression) and exploitation (resource use).
• Anolis carolinensis and invasive Anolis sagrei exhibit vertical habitat partitioning in the southern US, previously thought to be solely exploitative competitors.
• The role of direct interference in structuring Anolis assemblages remains understudied.

Purpose of the Study:

• To investigate the presence and impact of direct interference competition between Anolis carolinensis and Anolis sagrei.
• To determine if interference influences species interactions beyond resource competition.
• To understand the behavioral mechanisms underlying asymmetric competition in this invasive-native lizard system.

Main Methods:

• Field-based behavioral trials were conducted.
• Heterospecific male intruders (Anolis sagrei or Anolis carolinensis) were introduced to resident individuals of both species.
• Behavioral responses, including displays and retreats, were recorded to assess interference asymmetry.

Main Results:

• Interspecific interference competition was asymmetric, favoring Anolis sagrei.
• Anolis sagrei were more likely to display and less likely to retreat when encountering Anolis carolinensis.
• Anolis carolinensis exhibited arboreal retreat behavior, consistent with their habitat partitioning, even without physical attacks.

Conclusions:

• Subtle interference, characterized by signaling and avoidance rather than combat, significantly structures Anolis communities.
• Direct interference competition plays a crucial role in the coexistence dynamics and ecological interactions between these Anolis species.
• Understanding non-combative interference is essential for accurately predicting community structure and species interactions.