Meeting Abstract

S5-9   14:30 - 15:00  Is the medium the message? Phylogenetic and functional diversity are not strongly shaped by abiotic gradients in freshwater electric fishes. Ford, KL*; Albert, JS; University of Bern; University of Louisiana at Lafayette kassy159@gmail.com http://www.kassandraford.com

Abiotic factors related to geological and climatic processes are widely thought to affect ecological processes at the local (alpha diversity) and regional (beta diversity) scales. Salient abiotic factors affecting fish ecology in tropical freshwaters include water chemistry (e.g. pH, dissolved oxygen, temperature, conductivity), and conditions along the river continuum (e.g. elevation, substrate, flow rate, habitat volume). Here we review the effects of abiotic factors on the distribution of functional traits and species richness in Neotropical (Gymnotiformes) and Afrotropical (Mormyroidea) electric fishes, each clade represented by c. 250 valid species. Among Gymnotiformes, phenotypes and biodiversity patterns most strongly associated with abiotic variables are: 1, Deeper bodies in lateral profile with shorter tails in high conductivity, sediment-rich Amazonian whitewaters vs. more slender and elongate bodies with longer tails in low conductivity, low pH Amazonian blackwaters or clearwaters, or in non-Amazonian whitewaters. 2, High-frequency (60-2000 Hz) wave-type electric organ discharge (EOD) in fast-flowing rivers with more stable temperatures vs. low-frequency (1-100 Hz) pulse-type EOD in slowly-flowing floodplains and small streams with more variable temperatures). Sexual selection (a biotic variable) may contribute to this pattern with a strong phylogenetic signal of EOD types among gymnotiform families. 3, Highest local and regional species density in large (Strahler stream order 6-10), lowland (<100 m) whitewater rivers and várzeas of the Western Amazon. In mormyroids the four patterns are either not observed, or data are not known. We found little association between abiotic variables and craniofacial shape or trophic position.