Life-history of the South American darter, Characidium pterostictum (Crenuchidae): evidence for small scale spatial variation in a piedmont stream

Abstract

The present study compares the reproduction, condition and size of the small characiform fish, Characidium pterostictum, sampled at close sites differing in severity of flash flood effects. Data were obtained from seasonal samples in two sites situated 8 km apart in the same stream. In the upstream site, habitat is more severely affected by flash floods than in the downstream site, and this difference was hypothesized to produce differences in life history and individual reproduction trade-off patterns, as predicted by life-history theory. The results provided evidence for small-scale spatial variation in life-history and trade-off patterns within the studied population. At the most severely disturbed site, C. pterostictum displayed a trade-off pattern that favored reproductive life-span (e.g., larger size, higher and seasonally stable condition, larger mean size of mature females) over instantaneous reproductive output (lower gonadosomatic index), while the opposite pattern was observed in the less disturbed site. Because of the differences in disturbance effects between each sampling site, these results suggest that withinstream variability in the severity of hydrological disturbance can influence life-history patterns at small spatial scales. An implication of the results is that fish occupying areas that are hydrologically more variable within a stream are not necessarily at an energetic or reproductive disadvantage, but may be simply under environmental conditions that favor distinct patterns of energy allocation (or trade-offs) and population persistence, as predicted by life-history theory. Therefore, plasticity in lifehistory is expected to be common in stream fish populations that are widespread in a stream system with spatially variable or patchy habitat characteristics.Este estudo compara a estrutura populacional e a reprodução do pequeno caraciforme, Characidium pterostictum, amostrado em locais sujeitos a diferentes efeitos de perturbações hidrológicas naturais (enxurradas). Os dados foram obtidos a partir de amostragens sazonais em dois trechos distando 8 km entre si, no mesmo riacho. No trecho a montante, o habitat é mais severamente afetado pelas enxurradas do que no trecho a jusante e, devido a esta diferença, testou-se a hipótese de que haveria contrastes em padrões de alocação de energia entre reprodução e sobrevivência individual, como previsto pela teoria de história de vida. No trecho a montante, C. pterostictum apresentou características que favorecem a longevidade reprodutiva (como maior tamanho, condição mais elevada e sazonalmente pouco variável, maior tamanho de fêmeas maduras) em relação ao desempenho reprodutivo instantâneo (menor índice gonadossomático). O padrão oposto foi observado no trecho a jusante. Devido às diferenças em termos de efeito de perturbação (enxurradas) em cada trecho, esses resultados sugerem que a variabilidade espacial de perturbações hidrológicas pode influenciar padrões de história de vida dentro de uma população. Outra implicação dos resultados, é que os pei...

Life history traits of Characidium pterostictum (Characiformes, Crenuchidae) along the longitudinal gradient of a Neotropical river in southern Brazil

“…These results corroborate studies conducted for other Characidium species, as well as for most species of Characiformes for which data are available (Vazzoler & Menezes, 1992;Braga, 2006;Azevedo, 2010). Another study conducted in the Maquiné river, Rio Grande do Sul, involving other populations of C. pterostictum, also reported similar results regarding reproductive period (Becker et al, 2008). When compared the three sampled sites in the upper Sinos river, the similar reproductive period indicates that the main factors aff ecting extent and timing of C. pterostictum breeding are not variable enough to cause divergence between populations in this trait.…”

“…The species is commonly found in stream sections of distinct environmental characteristics and widely distributed along the longitudinal position, inhabiting watercourses with varied width, depth, water velocity, temperature and food resources. Becker et al (2008) found variation in life history characteristics of two C. pterostictum populations inhabiting sites that supposedly differed regarding harshness of flash floods. Nevertheless, although this species is widely distributed and relatively abundant, its reproductive traits and variation are still seldom studied (Braga, 2006).…”

“…According to Tamate & Maekawa (2000), fi shes exhibit fl exible life histories, with their strategies being largely determined by environmental conditions. In riverine ecosystems, the reproductive traits may vary even between populations of the same species, depending on the environmental characteristics of the diff erent habitats (Becker et al, 2008). Variations in temperature, photoperiod, rainfall, niche and food availability as well as hydrological disturbances are identifi ed as the main factors that infl uence certain reproductive traits, acting distinctly according to reproductive strategy, physiological traits and phylogenetic heritage of species (Winemiller, 1989;Vazzoler & Menezes, 1992;Braga et al, 2012;Espírito-Santo et al, 2013;Román-P et al, 2014).…”

Seasonal changes in the gonadossomatic index, allometric condition factor and sex ratio of an auchenipterid catfish from eastern Amazonia

“…The breeding season was identified by using two different approaches: (1) the seasonal variation concerning relative frequencies of ovarian and testis classified according to the maturation stage; and (2) through the analysis of the seasonal variation in the gonadosomatic index (GSI) (Vazzoler, 1996;Becker et al, 2008;Carvalho et al, 2009;Santos et al, 2010).…”

Changes in ichthyofauna composition along a gradient from clearwaters to blackwaters in coastal streams of Atlantic forest (southeastern Brazil) in relation to environmental variables

“…In coastal streams, P. obtusa, C. pterostictum, H. griemi and H. reticulatus occur in clearwaters (Aranha et al, 1998;Leung & Camargo, 2005;Becker et al, 2008), but some of these species are also abundant inhabiting blackwater streams (Leung & Camargo, 2005). In addition, Scleromystax macropterus occurred exclusively in the rio Preto, which supports the assertion of Oyakawa et al (2006) that the species shows a preference for lentic and blackwater streams.…”