Aspectos da ecologia de Mimagoniates microlepis (Steindachner, 1876) (Characidae, Glandulocaudinae) em um riacho costeiro: Reprodução, dinâmica populacional e movimento.

Abstract

The impacts that Rainforest streams have been suffering, biodiversity loss and high number of endemic species on this Brazilian biome are factors that reinforces the importance of studying the biology of fish species from this environment. In this work we present important issues about the biology and population structure of Mimagoniates microlepis. Specifically, we evaluated: i) rates of growth and densities fluctuation (return rate) through high temporal scale; ii) reproductive strategies and life history; and iii) spatial distribution and genetic structure of the population using mitochondrial DNA (mtDNA). Our results revelead that fluctuations in population size do not return to the equilibrium point and negative values of return rate, suggesting a decline of population. This scenario is probably occuring due human activities that have intensified over the years in Ubatiba river. Our observations of reproductive biology of the species showed that the species do not present a seasonal pattern as registered in other basins, and consequently, reproduce throughout the annual cycle. These reproductive strategies may ensure the survival of the offspring and local permanence of the species. We also found that males and females differed in relation to reproductive tactics. Females appear to invest more in reproduction than males, which is related to early maturation and high IGS values (> 5). Patterns of spatial segregation of size were also recorded. We verified that adults were consistently larger in upstream sites near the fountain?, while the small ones predominated in downstream sites near the river mouth?. This scenario indicates that individuals begin their life cycle in the lower reaches of the river and as they grow migrate towards bedside areas due to their ecological adaptability in relation to egg and larvae drift. The historical contact between its individuals along the Ubatiba river, whether by active or passive migrations (eggs and larvae drift) is supported by the molecular results of the COI and D-loop region. The sharing of haplotypes in all localities, from bedside areas to the mouth of the Ubatiba River, added to the genetic homogeneity revealed by the AMOVA Allelic Fixation Index (Фst), shows the existence of gene flow and that it is a characteristic of only one structural genetics population. The nucleotide and haplotypic diversity found was low.