Abstract
Few studies have explored the ecology and interrelationship with other organisms of the many endangered freshwater turtle species inhabiting the Neotropical Region. The focus of the current study was to shed light on the relationship between Neotropical turtle carapaces and primary producers, insofar as the surface of former constitutes a suitable substrate for the colonization and establishment of the latter. The under-explored relationship between turtle carapaces and the diatom assemblages inhabiting them was investigated and characterized in terms of taxonomic and biological traits (bio-volume, life-form, and attachment). The carapaces of seven native turtle species were surveyed. Among these carapaces, a total of 45 diatom taxa were found, and diatom taxa varied among turtle species. Podocnemis vogli and Podocnemis expansa supported more diverse diatom assemblages than Podocnemis lewyana, Rhinoclemmys diademata, and Rhinoclemmys melanosterna, which were dominated by Navicula spp. Analysis further showed that carapace size did not explain differences in diatom diversity. However, a trait-based analysis suggests that both carapace roughness and an assemblage’s successional stage might explain the differences in assemblage composition. Because turtles can serve as dispersal vectors, characterizing their epibiont diatom assemblages may contribute to our understanding of diatom distribution on larger scales, as well as, give us some clues as to the auto-ecology of turtles that help us to effectively determine conservation areas for these endangered species.
Highlights
The poor dispersal capabilities of diatoms represent a strong constraint to their spatial distribution along the longitudinal dimension of rivers (Kristiansen, 1996)
While the study of epizoic diatoms growing on the carapaces of marine turtles has been advanced considerably in recent years (Frick & Pfaller, 2013; Majewska, Santoro, Bolaños, Chaves, & De Stefano, 2015), such studies for freshwater turtles have remained scarce, and even more so in the Neotropical region, where epizoic diatoms in aquatic ecosystems have only been studied by Wetzel, van de Vijuer, Cox, and Ector (2010); Wetzel, van de Vijuer, Cox, Bicudo, and Ector (2012)
This study is one of the first to assess and compare the association between turtle carapaces and the diatom life-forms inhabiting them, in the Neotropical region. It is a small-scale study carried out on turtles in captivity, its findings show that turtle carapaces are not uniformly colonized by the same diatom species
Summary
The poor dispersal capabilities of diatoms represent a strong constraint to their spatial distribution along the longitudinal dimension of rivers (Kristiansen, 1996). In order to offset individual losses and maintain viable populations in upstream sections, diatoms have a wide variety of strategies, such as increasing the number of generations per year, developing attachment mechanisms, and growing on animals which can carry them to upstream sections (Peterson & Stevenson, 1989; Kristiansen, 1996; Tiffany, 2011). One such animal dispersal vector could be the turtle, for turtle carapaces provide a suitable substrate for diatoms, while turtles themselves travel long distances in the upstream. Specific associations could serve as proxies of turtle’s feeding behaviour and foraging sites, or population’s connectedness, which are important elements for delineating species home range
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