SUMMARYSpecies are different, but they are not equally different. Yet many indices of biodiversity assume species vary to identical degrees. This notion does not meet with intuition: some species vary greatly in terms of their morphology, behaviour and ecology, while others vary only a little. One way to reconcile the dissimilarity between species is by collecting information on their functional traits (FTs), descriptors of how organisms interact with their environment and each other. Functional diversity (FD) is the total variation in one or more FTs across all species within a community, and provides a powerful complement to species diversity. There are several challenges facing the application of FD to conservation science, including lack of rigorous trait data for many organisms, and sparse details on how to select available traits to generate meaningful inferences for the various summary metrics of FD. This Comment provides a brief discussion on choosing and using FTs, and recommendations for best practice. Ultimately, researchers need to consider using a variety of traits when hypotheses are multifaceted or could potentially evolve, at the same time thinking critically about trait selection to avoid redundant information.

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ABSTRACT. This manuscript presents information about the ecology of Lontra longicaudis (Olfers, 1818) in the Taquari Valley, State of Rio Grande do Sul, southern Brazil. The study was carried out in two areas located in the Forquetinha Creek and in the Forqueta River from January to December 2003. The otters are specialist feeders (B sta = 0.24), with a diet based mostly on fish, especially those of the families Loricariidae and Cichlidae. Most shelters used by the species were excavated burrows underneath tree roots, while shelters within rocks were used less frequently. The burrows showed great variation in size, being found on average 3.5 m (sd = 3.6 m) away from the margin and 2.5 m (sd = 1.2 m) above the water level. Scent marks were made preferentially on rocks and fallen tree trunks at the edge of the water. There was a tendency to increase the reutilization of latrines in detriment of using new sites throughout the sample period. KEYWORDS.Neotropical otter, feeding habit, scent marking, resting sites, Brazil. RESUMO. Ecologia trófica e o uso de abrigos e latrinas pela lontra Neotropical (Lontra longicaudis) no Vale do Taquari, RioGrande do Sul, Brasil. O presente estudo apresenta dados sobre a ecologia de Lontra longicaudis (Olfers, 1818) no Vale do Taquari, sul do Brasil. O trabalho foi realizado em duas áreas localizadas no arroio Forquetinha e rio Forqueta, entre janeiro e dezembro de 2003. A população apresentou hábito alimentar especialista (B sta = 0,24), baseado em peixes das famílias Loricariidae e Cichlidae. Os abrigos utilizados pela espécie foram formados em sua maioria, por escavações sob raízes de árvores e, com menor freqüência, entre rochas. Os abrigos escavados apresentaram dimensões bastante variáveis, sendo que estiveram em média a 3,5 m (s = 3,6 m) de distância da margem e 2,5 m (s = 1,2 m) de altura em relação ao nível da água. A utilização de marcas odoríferas se deu preferencialmente sobre rochas e troncos caídos na margem, sendo que houve uma tendência de aumento na reutilização de latrinas, em detrimento de novos pontos de deposição de fezes, no decorrer do período amostrado. PALAVRAS CHAVE. Lontra Neotropical, hábito alimentar, marcação odorífera, locais de descanso, Brasil.

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