Spatial isolation and fish communities in drainage lakes

Fifty-two drainage lakes, located in south-central Ontario, Canada, were ex amined to study the association of isolation- and environment-related facto rs with fish community composition. Eight quantitative measures of lake iso lation were examined, each of which incorporated potential ecological "chal lenges" that a fish encounters when moving between lakes. A Procrustean app roach was employed to assess the degree of concordance between fish assembl age structure, measures of lake isolation and environmental conditions (i.e ., lake morphology and water chemistry). Our results revealed a high concor dance between patterns in fish community composition and lake isolation and lake morphology at the watershed scale, suggesting that insular and habita t-related factors influence the structure of fish communities. At the scale of the individual lake, this relationship varied greatly, ranging from a s trong match of community composition with both spatial and abiotic conditio ns to communities exhibiting weak association with these conditions. Furthe rmore, we showed that alternative measures of Lake isolation provide additi onal insight into potential factors shaping patterns in fish community comp osition; information not provided using straight-line distances between lak es. Finally, the statistical methodology outlined in this paper provides a robust technique for assessing both the overall association between multiva riate data matrices (i.e., landscape or regional scale), as well as facilit ating the examination of smaller-scale relationships of individual observat ions (i.e., local scale).