Diet quality and prey selectivity correlate with life histories and predation regime in Trinidadian guppies

Abstract

Summary 1.Life histories evolve as a response to multiple agents of selection, such as age-specific mortality, resource availability or environmental fluctuations. Predators can affect life-history evolution directly, by increasing the mortality of prey, and indirectly, by modifying prey density and resources available to the survivors. Increasing survivor densities can intensify intraspecific competition and cause evolutionary changes in their selectivity, also affecting nutrient acquisition. 2. Here, we show that different life-history traits in guppies (Poecilia reticulata) are correlated with differences in resource consumption and prey selectivity. We examined differences in wildcaught guppy diet among stream types with high (HP) and low predation (LP) pressure and how they are related to benthic invertebrate biomass. Fish and invertebrate samples were collected from two HP and two LP reaches of two distinct study rivers in Trinidad. 3. Our results reveal a strong association between life history and diet. Guppies from HP environments mature earlier and have higher fecundity and reproductive allotment than those from LP environments. Prior work revealed that their population densities are lower and that they grow faster than their LP counterparts. Here, we show that these life-history differences are repeated and that HP guppies feed primarily on invertebrates. In contrast, guppies from LP sites feed primarily on detritus and algae, which are a poorer quality food. LP guppies fed on invertebrates according to their availability, while HP guppies were selective towards those invertebrates with the lower carbon ⁄ nitrogen body ratio and thus with higher nutritional value. 4. Our study suggests that as predators shape the life histories of their prey and alter prey population densities, they can also indirectly shape their prey's foraging and diet selectivity. This is, to our knowledge, the first report on how intraspecific differences in life-history traits are correlated with prey selectivity, where prey stoichiometry is included. Although there are clear limitations of association data, our study suggests that the patterns of resource use and life history evolve in concert with one another. However, further research is needed to investigate the possible causal links between risk of predation, the indirect effects of predators on guppy population density, the evolution of life-history traits and nutrient acquisition.

Divergence across diet, time and populations rules out parallel evolution in the gut microbiomes of Trinidadian guppies

“…In addition to these attributes, HP and LP ecotypes also diverge in trophic ecology, and HP guppies eat significantly more invertebrates than their derived LP counterparts that consume more detritus and diatoms (Zandonà et al, 2011). Dietary differences have also been observed in commongarden settings (Bassar et al, 2010) and appear related to differences in gut morphology and physiology (Sullam et al, 2014).…”

“…Despite dietary differences repeated across streams and years (Bassar et al, 2010;Zandonà et al, 2011), and differences in gut size and enzymatic activity (Sullam et al, 2014), gut bacterial communities did not show strong or clear convergence across independently derived LP ecotypes, nor did they show high similarity among the ancestral HP ecotypes from across the targeted streams.…”

“…In this experiment, 64 LP and HP guppies were randomly assigned to 16 tanks and fed a predominately spinach or brine shrimp diet. These diets roughly reflect the highly detrital and algal diet of LP guppies and invertebrate diet of HP guppies, previously found in the Aripo and Guanapo Rivers (Zandonà et al, 2011). A subset of reared females (n ¼ 14), each from a separate tank, was analyzed for gut microbes, whereas the remaining fish were analyzed for enzyme activities in another study (Sullam et al, 2014).…”

<b>Diet of <i>Poecilia reticulata</i> Peters, 1959 in streams from Paraná River basin: influence of the urbanization

“…The consumption of detritus and benthonic invertebrates reinforces the status of benthivorous fish of P. reticulata, such as verified by several authors (Dussalt & Kramer, 1981;Zandona et al, 2011;Silva et al, 2012;Bonatto et al, 2012). However, the presence of terrestrial organisms in the gastrointestinal contents indicates that this small fish can occasionally feed on the surface.…”

An Operational Framework for the Advancement of a Molecule-to-Biosphere Stoichiometry Theory

“…However, classical stoichiometric theories mainly considered the effects of elemental limitation on somatic growth, and more rarely its effects on life history traits (reviewed in Moe et al, 2005). Fecundity was generally found to be affected by poor diet quality (Sterner, 1998;Urabe and Sterner, 2001;Zandona et al, 2011). Few studies focussed on stoichiometryrelated mortality (Sterner et al, 1993;Nelson et al, 2001;Declerck et al, 2015; Table 2).…”