High intraspecific variability in morphology and diet in tropical stream fish communities

Abstract

Functional diversity of fish communities has been measured according to (a) interspecific variability, assuming that intraspecific variability is negligible, or (b) morphological differences, as good descriptors of complex functions, such as diet. These two assumptions have been scarcely tested on the individual level, especially in species‐rich tropical ecosystems. Here, we adapted intraspecific specialisation (ISpe) and intraspecific originality indices (IOri) to assess complementary components of intraspecific variability. Next, we applied these indices to evaluate the intra‐ and interspecific variability of morphological and diet traits in two contrasting Brazilian stream‐dwelling fish assemblages (rainforest and savannah). We also compared correlations between morphology and diet at the individual and species level to test whether accounting for intraspecific variability increases the predictability of diet due to morphological differences. Significant contributions of intraspecific variability to differences between fish were revealed for morphology and diet. Intraspecific variability in the diet was higher than that in morphology in both assemblages. The ISpe was positively correlated to IOri in the diet of both ecosystems. The morphological–dietary relationships were significant but weak at both individual and species levels. Our findings highlight the importance of measuring individual variability and accounting for complementary components of the intraspecific variability (ISpe and IOri). Importantly, we showed that the variability in morphology does not predict diet variability at both intra‐ and interspecific levels. Thus, high intraspecific variability in morphology and diet challenges the use of functional traits measured at the species level to describe the functional diversity of different fish assemblages.

Variação Intraespecífica Em Peixes De Riacho Com Ênfase Na Ecologia Trófica

“…Cada abordagem contribui de forma única para o avanço do conhecimento ecológico, desde respostas mais descritivas a respeito de uma população ou comunidade local (e.g. Brito et al 2019, Manna et al 2019) até respostas mais teóricas que ajudam a explicar dinâmicas ecológicas e/ou evolutivas (e.g. Matthews et al 2010).…”

“…No entanto, apenas aqueles artigos que relacionaram aspectos da variação intraespecífica com as estratégias tróficas em populações e/ou comunidades foram considerados, restando 22 artigos. Para exemplificar a existência de variação intraespecífica dentro de populações de peixes, dados referentes a duas espécies do gênero Deuterodon, que coexistem em um riacho costeiro de Mata Atlântica, revelam diferenças na dieta com alta variação intraespecífica em ambas as espécies (Manna et al 2019). Deuterodon hastatus utiliza insetos aquáticos como principal fonte alimentar, enquanto Deuterodon taeniatus, matéria vegetal alóctone.…”

“…Além disso, as diferenças individuais no consumo alimentar podem deslocar determinados indivíduos para um outro nicho trófico, diminuindo então a sobreposição de nicho e, consequentemente, a competição Figura 3. Representação gráfica de dados individuais na dieta de duas espécies de Deuterodon (retirado de Manna et al 2019). Cada ponto representa um indivíduo e cada linha, a distância para a média da população (quadrado branco).…”

“…Essa distribuição de dados revela alta variação intraespecífica para ambas as espécies, mas em locais diferentes desse espaço funcional devido às diferenças em suas fontes principais de alimento. Manna et al 2019). Black dots indicate each individual and each line, the distance to population mean value (white square).…”

Seed traits and phylogeny explain plant distribution at large geographic scale

“…It is interesting to note that Sides and Sloat (2014) found that species with greater intraspecific variation in specific leaf area (SLA) have wider ecological breadth. Because of its potential role in modulating the responses of plant species to environmental changes, greater intraspecific functional variability may enable species to adjust to a wider range of competitive and abiotic conditions (Sides and Sloat, 2014;Manna et al, 2019).…”