Ecomorphological Diversification in Lowland Freshwater Fish Assemblages from Five Biotic Regions

Winemiller, Kirk

This study investigates the relationships among species diversity, community structure, and convergent evolution among divergent fish faunas. Morphological traits can be used as surrogates for ecological data in the comparative study of community niche relationships. In the present study I examined 30 morphological features related to the ecology of the dominant fish species from lowland stream and backwater habitats in five widely separated geographic regions: nearctic Alaska, temperate North America, Central America, South America, and tropical Africa. The study regions exhibited a general gradient of species richness from a minimum of 6 dominant species at one of the high-latitude sites (65° N) to a maximum of 43 numerically dominant species at a neotropical site (8° N). Fishes from Alaskan sites near the edge of the polar circle tended to be larger than fishes at other sites. Mean values for most morphological characters varied little between regions, indicating similar faunal centroids in morphological space. Morphological diversification within fish assemblages was estimated from species similarities based on Euclidean distances plus species projections on the principal axes from multivariate analysis. The total morphological space encompassed by ichthyofaunas in both stream and backwater sites was generally concordant with the latitudinal and species-richness gradient, with low-diversity nearctic assemblages exhibiting little morphological diversification relative to high-diversity tropical faunas.

Ecomorphological Diversification in Lowland Freshwater Fish Assemblages from Five Biotic Regions

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