Fish trait diversity in littorals of two floodplain lakes of the highly biodiverse Caura River, Venezuela

Abstract

We studied the trait diversity and structure in the fish communities of two floodplain lakes of the Caura River: Aricagua and Paramuto, during one hydrological cycle. We calculated taxonomic and a functional alpha and beta diversities and made comparisons among hydrological seasons and among habitats within each lake based on rarefactions. The trait structure was explored with an RLQ (analysis of a table R of environmental conditions, a table L of abundances of species and a table Q of species traits) analysis, and pairwise relationships between environmental variables and traits were explored with fourth-corner analyses. Despite its smaller extension, Paramuto showed higher alpha taxonomic and trait diversities. The substrates of open sand and those covered by leaf litter were the most diverse habitats in terms of both species and traits. The trait structure of the fish communities was influenced by the hydrological seasons, the lakes as well as water pH and temperature, and in a lesser degree dissolved oxygen, habitat type and total dissolved solids in the water. These factors constitute the habitat templet for the fish community's composition and trait structure. K E Y W O R D Scomponents of beta diversity, fourth-corner analysis, neotropical freshwater fish communities, RLQ analysis

Fish taxonomic and functional diversity in mesohabitats of the River Kakada, Caura National Park, Venezuela

“…Each mesohabitat type was associated to certain fish traits, in a manner that seems to reflect the species adaptations to the substrate structure and also to the particular trophic resources they offer. Some of the observed fish trait -mesohabitat associations were similar to those observed in the floodplain lakes of the lower River Caura (Echevarría & González, 2018), such as that between sandy bottoms and invertivores and that between the bottoms covered by debris with detritivores, suggesting the origin of these associations might be related to the trophic resources within these mesohabitats. The rocky substrates were associated to herbivores, mouths in ventral position and fusiform bodies, such as that of Apareiodon sp., a specialist in fast currents that scraps algae from the surface or rocks with its specialised mandibles (Casatti & Castro, 2006).…”

“…However, the functional compositions and diversities within mesohabitats did not change seasonally, indicating that across the hydrological season, there is a replacement of species that are functionally rather similar. This pattern deviates from the one observed in mesohabitats of the floodplain lakes of the lower River Caura, where both the taxonomic and functional diversities varied seasonally (Echevarría & González, 2018), along with the taxonomic composition (Echevarría & González, 2017). In other Neotropical rivers, seasonal variations in functional dispersion have been related to seasonal species turnover and changes in their frequencies of occurrence (Fitzgerald et al, 2017).…”

“…The convex hull of Siluriformes was determined by three points represented by the flat bodied detritivore Loricariids, the cylindrical bodied and invertivore Corydoras spp., and the slender omnivore Pimelodella spp. The traits exhibited by the Loricariids, particularly the flat bodies and the mouths in terminal position with mandibles specialised in gauging wood (Lujan et al, 2012) enabled them to forage on bottoms with debris that included logs, in a similar trend as in floodplain lakes of the lower River Caura (Echevarría & González, 2018). The Characiformes exhibited a wider combination of traits and their functional space was occupied by more species in a less divergent pattern than that of Siluriformes.…”

“…In the River Caura Basin, a recently declared national park, the taxonomic diversity of fishes is relatively well known (Chernoff et al, 2003;Machado-Allison et al, 2003;Vispo et al, 2003;González et al, 2012a), as well as some ecological aspects of the fish communities such as their trophic structure (González & Vispo, 2004) and reproductive biology (Echevarría et al, 2011). The only study of functional diversity was carried out in mesohabitats of two floodplain lakes of the lower River Caura (Echevarría & González, 2018), where significant spatiotemporal differences in taxonomic and functional diversities were evidenced, with the highest diversities occurring in mesohabitats of leaf litter and sandy bottoms. It was also found that these mesohabitats were associated to different fish traits.…”

Environmental filtering and low trait redundancy characterise fish assemblages in Lake Mamo, Orinoco River floodplain, Venezuela

“…Likewise, the strength of environmental filters varies according to the age of a patch (Arrington et al, 2005). In these floodplains, the taxonomic and functional structure of fish communities is determined by seasonality and substrate type (Echevarría & González, 2017b). However, functionally similar species can show spatial segregation for short periods , while many pairs of species are randomly associated, implying that fish communities are determined not only by environmental filters, but also by biotic and stochastic factors.…”