10.5061/DRYAD.TQJQ2BVX5
Neves, Mayara
0000-0003-2523-3874
Federal University of Rio Grande do Sul
Costa-Pereira, Raul
State University of Campinas
Delariva, Rosilene Luciana
State University of West Paraná
Fialho, Clarice Bernhardt
Federal University of Rio Grande do Sul
Seasonality and interspecific competition shape individual niche variation
in co-occurring tetra fish in Neotropical streams
Dryad
dataset
2020
co-occurrence
Gut contents
southern Brazil
FOS: Biological sciences
tropic niche breadth
National Council for Scientific and Technological Development
https://ror.org/03swz6y49
152847/2016-2
2020-09-17T00:00:00Z
2020-09-17T00:00:00Z
en
16579 bytes
2
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
The drivers of intraspecific niche variation and its effects on species
interactions are still unclear, especially in species-rich Neotropical
environments. Here, we investigated how ecological opportunity and
interspecific competition affect the degree of individual trophic
specialization and the population niche breadth in tetra fish. We studied
the four ecologically similar species (Psalidodon aff. gymnodontus, P.
aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical
headwater streams (three sites with two co-occurring species and three
sites with only one species). We sampled fish in two contrasting seasons
(winter/dry and summer/wet), and quantified their trophic niches using gut
content analysis. Psalidodon bifasciatus was the only species distributed
over all the sampled streams. We observed seasonal differences in
population trophic niche breadth of P. bifasciatus just when this species
co-occurred with P. aff. gymnodontus. These findings confirm the complex
nature of the effects of interspecific competition, depending, for
instance, on the identity of the competitor. The degree of individual
specialization of P. bifasciatus was higher in the winter, and it was not
influenced by the presence of another species. Conversely, the other two
Psalidodon species studied presented greater individual specialization in
the summer, when fish consumed a higher proportion of allochthonous items
(terrestrial insects and seeds), and there were no effects only for B.
ikaa. Herein, our results suggest that seasonality in food-resource
availability is a major driver of niche variation and it has the potential
to play an important role in how these similar tetra species interact and
coexist.
We sampled six headwater streams (2nd and 3th orders – Figure S1, Table
S1) and collected all small characids species found: Psalidodon aff.
paranae (Eigenmann, 1914), Psalidodon bifasciatus (Garavello &
Sampaio, 2010), Psalidodon aff. gymnodontus (Eigenmann, 1911) and
Bryconamericus ikaa Casciotta, Almirón & Azpelicueta, 2004. We
sampled fish in July (winter) and December (summer) 2017. According to the
historical climate series of the region, 2017 represents a typical year
with cold and dry winter, and hot and rainy summer . In each season, we
realized one sampling event per stream. We conducted the fish sampling in
reaches of 50 m using electrofishing with three passes of 40 min. After
capture, specimens were anaesthetized, fixed in 10% formalin, and
preserved in 70% alcohol. We collected fish with authorization from the
Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) (license
number 25039-1) and approved by the Ethics Committee on Animal Use of the
Universidade Federal do Rio Grande do Sul (CEUA – 32734) in accordance
with protocols in their ethical and methodological aspects for the use of
fish. We identified specimens in the laboratory according to specific
identification keys (Baumgartner et al., 2012; Ota, Deprá, Graça &
Pavanelli, 2018). To avoid bias caused by ontogenetic variations, we
selected 403 adult individuals (Table S2). Voucher specimens were
deposited in the fish collection of the Departamento de Zoologia,
Universidade Federal do Rio Grande do Sul. We analyzed the stomach
contents under stereoscopic and optical microscope and feeding items were
identified to the lowest possible taxonomic level, using specific
literature for the algae (Bicudo & Bicudo, 1970) and invertebrates
(Mugnai, Nessimian & Baptista, 2010). We quantified the proportion
of feeding items in each individual’s diet following the volumetric method
(Hyslop, 1980) using graduated test tubes and a glass counting plate
(Hellawell & Abel, 1971).