Understorey environments influence functional diversity in tank‐bromeliad ecosystems

Abstract

Summary 1. A substantial fraction of the freshwater available in neotropical forests is impounded within the rosettes of bromeliads that form aquatic islands in a terrestrial matrix. The ecosystem functioning of bromeliads is known to be influenced by the composition of the contained community but it is not clear whether bromeliad food webs remain functionally similar against a background of variation in the understorey environment. 2. We considered a broad range of environmental conditions, including incident light and incoming litter, and quantified the distribution of a very wide range of freshwater organisms (from viruses to macroinvertebrates) to determine the factors that influence the functional structure of bromeliad food webs in samples taken from 171 tank‐bromeliads. 3. We observed a gradient of detritus‐based to algal‐based food webs from the understorey to the overstorey. Algae, rotifers and collector and predatory invertebrates dominated bromeliad food webs in exposed areas, whereas filter‐feeding insects had their highest densities in shaded forest areas. Viruses, bacteria and fungi showed no clear density patterns. Detritus decomposition is mainly due to microbial activity in understorey bromeliads where filter feeders are the main consumers of microbial and particulate organic matter (POM). Algal biomass may exceed bacterial biomass in sun‐exposed bromeliads where amounts of detritus were lower but functional diversity was highest. 4. Our results provide evidence that tank‐bromeliads, which grow in a broad range of ecological conditions, promote aquatic food web diversity in neotropical forests. Moreover, although bromeliad ecosystems have been categorised as detritus‐based systems in the literature, we show that algal production can support a non‐detrital food web in these systems.

Euglenophyceae from bromeliad phytotelmata: new records for Bahia state and Brazil

“…According to Brouard et al (2012), mixotrophic Euglenophyceae are often found in partially or totally shaded bromeliads absorbing more organic than inorganic nitrogen. However, we suppose that sunlight has a greater influence on the diversity of Euglenophyceae (especially pigmented ones) more than the concentration of organic matter in bromeliad tanks.…”

Assessing the role of canopy cover on the colonization of phytotelmata by aquatic invertebrates: an experiment with the tank-bromeliad Aechmea lingulata

“…Among these, leaf litter and fine particulate organic matter (FPOM) constitute the main food resources (Brouard et al, 2012). Abiotic (leaching) and biotic processes (microorganisms and invertebrate detritivores) (Graça, 2001) successively decompose this material.…”

“…Abiotic (leaching) and biotic processes (microorganisms and invertebrate detritivores) (Graça, 2001) successively decompose this material. As in other aquatic ecosystems (Graça et al, 2015), the availability of organic detritus is a relevant factor to phytotelm communities (Walker et al, 1997;Brouard et al, 2012;Dézerald et al, 2013). Thus, both the quantity and quality of organic detritus can influence invertebrate abundance (Armbruster et al, 2002) and taxonomic richness (Kitching, 2000(Kitching, , 2001, as well as the biomass for functional feeding groups (Srivastava, 2006;Ptatscheck and Traunspurger, 2015).…”

“…Furthermore, recent studies have found that food resources, i.e., algae and organic detritus, may vary in phytotelmata held by shaded and unshaded bromeliads (Yee and Willig, 2007;Brouard et al, 2012;Dézerald et al, 2014). According to Kaufman et al (2006), in unshaded bromeliads, algae constitute a high energetic resource to consumers because they provide nutritionally important compounds such as sterols, fatty acids and organic carbon.…”

Aquatic invertebrates associated with bromeliads in Atlantic Forest fragments

“…Some invertebrates, such as oligochaetes and ostracods, spend their entire lives inside the cisterns of bromeliads (Montero et al 2010, Pinto & Jocqué 2013, while others are only found in such habitats in immature forms, mainly beetles and flies (Mestre et al 2001). These organisms play an important role (Sodré et al 2010), by helping to degrade the organic matter falling from the forest canopy, accelerating the release of nutrients to the bromeliad (Benzing 1990, Richardson 1999, Armbruster et al 2002, Araújo et al 2007, Brouard et al 2012. Furthermore, Martinelli et al (2008) mentioned the ecological importance of bromeliads due to their interaction with fauna, making a considerable contribution of the biodiversity of the communities in which they live.…”