Regional Parapatry of the Congeneric Cyprinids Lythrurus snelsoni and L. umbratilis: Species Replacement along a Complex Environmental Gradient

Towards a mechanistic understanding of fish species niche divergence along a river continuum

“…Nevertheless, recently published niche models for N. topeka have documented a decrease in site occupancy with stream size (Wall et al 2004, Gerken andPaukert 2013), supporting the stream-size preference described by Cross (1967) and our hypothesis that N. topeka exhibits a complementary distribution with its congener, N. stramineus. This repeated pattern of stream-size niche complementarity between congeners shown in the current study and for other congeners in eastern North America (e.g., Braasch andSmith 1965, Taylor andLienesch 1996) suggests that a general, yet poorly understood mechanism underlies the distribution of fishes in stream networks.…”

“…For example, the congeneric topminnow species (Teleostei: Fundulidae), Fundulus notatus and F. olivaceus, occupy tributaries and river mainstems, respectively, in the Mississippi River basin (Braasch andSmith 1965, Schaefer et al 2011). Similarly, Taylor and Lienesch (1996) described the tributary and river mainstem preferences of Lythrurus snelsoni and L. umbratilis (Teleostei: Cyprinidae), respectively, in the Ouachita Mountains of southeastern Oklahoma, USA. These observations suggest that turnover in warmwater stream fish communities is a consequence of direct environmental gradients (other than temperature and resources) differentially filtering congeners or conditionspecific competitive exclusion by competitors.…”

Distribuição de peixes na microbacia do Ribeirão Grande, Serra da Mantiqueira Oriental, São Paulo, Brasil

“…Esse padrão surge quando espécies de relacionamento muito próximo não sobrepõem suas áreas de distribuição; nesses casos uma espécie é dominante de um lado da linha divisória e a outra é dominante do outro lado (MAYR, 1968;BULL, 1991). A competição interespecífica entre espécies morfologicamente similares pode levar à parapatria, onde também outros fatores bióticos e abióticos contribuem para a manutenção da distribuição parapátrica (TAYLOR & LIENESCH, 1996). A distribuição da ictiofauna nos riachos de encosta da Serra da Mantiqueira Oriental está associada ao relevo das vertentes, que delimitam e caracterizam as microbacias e às adaptações desenvolvidas pelas espécies de peixes que a habitam.…”

Habitat associations of a semi-arid fish community in a karst spring-fed stream

“…Heterogeneity among and within abiotic parameters increases with longitudinal distance from spring outflows because of contributions from sheet flow (e.g., tributary streams) and regional abiotic conditions (e.g., ambient temperatures) (Power et al, 1999). Longitudinal variations in abiotic parameters influence fish distributions within spring-fed streams according to species-specific physiological tolerances and habitat associations (e.g., Taylor and Lienesch, 1996). Among larger karst streams, regionally endemic fishes are generally concentrated in the stenothermal, headwater sections of streams, whereas fishes with more ubiquitous distributions are generally concentrated in the more abiotically variable, downstream sections of streams (Hubbs, 1995).…”

“…Because of their limited distributions in or near a spring source, these regionally endemic fishes are often described as spring-associated; however, exact factors leading to their restricted range as well as their segregation with riverine taxa remain unclear (Garrett et al, 2004). Several biotic (e.g., competition, fecundity) and abiotic (e.g., temperature, salinity, stream order, stream gradient) factors are hypothesized to regulate fish distributions and segregation among fish assemblages (Garrett et al, 2004;Gido et al, 1999;Ingersoll and Claussen, 1984;Taylor and Lienesch, 1996). Among abiotic factors, constant temperature is most often identified as the explanatory variable of fish assemblage segregation in larger karst streams (Bonner et al, 1998;Gehlbach et al, 1978;Hubbs, 2001).…”