Chromosomal evidence of population subdivision in the freshwater fish Leporinus elongatus in the Upper Paraná River basin

Abstract

Cytogenetic analyses performed in populations of the Neotropical freshwater fish Leporinus elongatus of the Upper Paraná River basin showed a chromosome polymorphism involving heterochromatic segments of the nucleolar organizing pair in this species. The NOR-bearing chromosome pair was characterized by two phenotypes identified by the absence (C 1 ) or presence (C 2 ) of a heterochromatic segment located in an interstitial position of the long arm in this pair. The meiotic segregation of these variations results in three distinct cytotypes, C 1 C 1 , C 1 C 2 and C 2 C 2 . Both populations were in Hardy-Weinberg equilibrium. Sex-related cytotype divergence was identified and multivariate analyses revealed that the C 2 C 2 individuals presented morphometric differentiation relative to body height in relation to the other cytotypes. A chromosome differentiation and a cytotype proportion difference observed between both populations suggest the occurrence of population subdivision within this species along the Upper Paraná River basin. These findings might contribute to the knowledge of the population biology of this fish and for its conservation.

Morphological Differentiation in the Damselfish Abudefduf saxatilis Along the Mexican Atlantic Coast is Associated with Environmental Factors and High Connectivity

“…However, further studies are necessary to state about the main evolutionary processes underlying these variations. Our study builds on a previous investigation on the morphological variation of A. saxatilis from the coast of Brazil (Molina et al 2006) by providing evidence suggesting that shape variation also occurs in the Mexican Atlantic coast in the species and that it is correlated with environmental but not with genetic variation.…”

“…During the reproductive season males aggressively defend individual territories, showing great fidelity to the sites they inhabit (Albrecht 1969). Molina et al (2006) found that Brazilian populations of A. saxatilis show significant differences in body size and shape that might be related to variation in water temperature and oceanic currents, which play a role as oceanographic barriers. However, their study does not include environmental or genetic data to support their suggestion.…”

Pleistocene karyotypic divergence in Hoplias malabaricus (Bloch, 1794) (Teleostei: Erythrinidae) populations in southeastern Brazil

“…Redi (2001) also suggests that heterochromatin would be involved in speciation. Within-population heterochromatin variation has been reported for Astyanax scabripinnis (Mantovani et al, 2000) and among-population variation has been observed in H. malabaricus populations from the rio Tibagi and rio Iguaçu (Vicari et al, 2003), and in Leporinus elongatus from the Tibagi (Molina et al, 2008). However, Sumner (2003) indicates that the relation between heterochromatin and chromosome pairing and crossing-over has been not demonstrated consistently and therefore it is not possible to assign a clear function to this type of chromatin.…”

Morphological and Genetic Divergences in a Coral Reef Damselfish, Pomacentrus coelestis

“…fin-rays counts, size) among populations of the clownfish, Amphiprion clarkii. Molina et al (2006) highlighted body shape variation between continental and island populations of a damselfish, Abudefduf saxatilis. To our knowledge, geographic variation of skull shape has never been tested in coral reef fishes although it has been extensively studied in freshwater (e.g.…”