Species traits influence assemblage structure across anthropogenic environmental gradients in streams.
Allan, David1, Infante, Dana2, 1 School of Natural Resources, Ann Arbor, MI, USA2 Institute for Fisheries Research, Ann Arbor, MI, USA
ABSTRACT- Recent studies suggest that analyses of biological assemblages summarized by phenotypic traits (trophic, life cycle, habit, and stressor tolerance) may be more insightful than taxon-based analyses, and that landscape features, including anthropogenic land use, may act as filters that can be linked to assemblage differences when summarized by traits. Common fish species and macroinvertebrate taxa collected from 46 stream sites in southeastern Michigan were summarized by traits, and principal component analysis was used to identify biological gradients. Axes that explained the most variation in fish and macroinvertebrates were interpreted as gradients in ecological integrity because each was strongly and positively weighted by intolerant taxa and trait specialists. However, only the axis summarizing macroinvertebrate integrity was correlated with taxon diversity and richness; the axis summarizing ecological integrity for fishes was not correlated with either measure. Instead, a different fish axis, which emphasized the inclusion of fluvio-lacustrine species, was correlated with diversity, implying that stream fish diversity was elevated by lentic conditions. These findings emphasize the value of viewing an assemblage through its phenotypic trait diversity, and support the view that environmental features, acting as filters on phenotypic traits, have a strong influence on assemblage structure.
Key words: trait, diversity, assemblage, stream
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