Niche dissociated assembly drives insular lizard community organization

Area of Science:

• Ecology
• Community Assembly
• Island Biogeography

Background:

• Interspecific competition and niche partitioning are traditionally viewed as key drivers of community assembly.
• These processes are often inferred from species co-occurrence, abundance distributions, and body size patterns.
• Previous research has extensively investigated these patterns to understand the role of competition.

Purpose of the Study:

• To investigate the role of competitive niche partitioning in shaping insectivorous lizard communities on the Andaman & Nicobar Islands.
• To analyze species co-occurrence, species abundance distributions (SADs), and body size distributions at both archipelago and island levels.
• To determine if niche subdivision explains species assortment in these island lizard communities.

Main Methods:

• Analyzed species co-occurrence patterns, noting negative co-occurrences primarily between species on islands separated by deep ocean channels.
• Conducted guild co-occurrence analyses, finding no positive co-occurrence among ecologically similar species.
• Modeled species abundance distributions (SADs) using Pareto distributions for both metacommunity and local communities.
• Examined body size distributions for predictable spacing among co-existing species.

Main Results:

• Negative geographic co-occurrences were linked to historical allopatry rather than current interspecific competition.
• Species abundance distributions were consistently explained by Pareto distributions across different scales.
• No evidence of predictable body size spacing was found among co-existing lizard species.
• Empirical data did not support niche subdivision as a mechanism for species assortment in these island communities.

Conclusions:

• The assembly of insectivorous lizard communities in the Andaman & Nicobar Islands is not driven by competitive niche partitioning.
• Historical allopatry and niche-dissociated assembly appear to be more significant factors shaping these island communities.
• Niche-dissociated assembly may play a crucial role in biological community formation across various geographic scales.