Abstract
The distribution of genetic diversity across a species distribution range is rarely homogeneous, as the genetic structure among populations is related to the degree of isolation among them, such as isolation by distance, isolation by barrier, and isolation by environment. Jenynsia lineata is a small viviparous fish that inhabits a wide range of habitats in South America. To decipher the isolation processes that drive population structuring in J. lineata, we analyzed 221 sequences of the mitochondrial cytochrome c oxidase I gene (COI), from 19 localities. Then, we examined the influence of the three most common types of isolation in order to explain the genetic variation found in this species.Our results revealed a marked structuration, with three groups: (a) La Plata/Desaguadero Rivers (sampling sites across Argentina, Uruguay, and Southern Brazil), (b) Central Argentina, and (c) Northern Argentina. A distance‐based redundancy analysis, including the explanatory variables geographical distances, altitude, latitude, and basin, was able to explain up to 65% of the genetic structure. A variance partitioning analysis showed that the two most important variables underlying the structuration in J. lineata were altitude (isolation by environment) and type of basin (isolation by barrier).Our results show that in this species, the processes of population diversification are complex and are not limited to a single mechanism. The processes that play a prominent role in this study could explain the high rate of diversity that characterizes freshwater fish species. And these processes in turn are the basis for possible speciation events.
Highlights
The distribution of genetic diversity across a species distribution range is rarely homogeneous since there is a genetic structure related to the degree of isolation that may exist among groups of individuals
The explanatory variables were as follows: (a) the geographical distance between localities as indicated by the first six axes of a Principal Coordinates of Neighbour Matrices (PCNM) on the geographical distance matrix where each axis was considered as separate variables; (b) the basin and (c) system type, as categorical variables; (d) the altitude expressed as meters above sea level; and (e) latitude expressed by decimal coordinates
Since it is a small fish, J. lineata should have a limited dispersal capacity, so its structuring could be due to other factors, such as population size, which affects the geographical distance, which we evidence in our analysis (Mantel test and db-RDA) where we did not detect any IBD pattern in this species
Summary
The distribution of genetic diversity across a species distribution range is rarely homogeneous since there is a genetic structure related to the degree of isolation that may exist among groups of individuals. The Mantel test results were not significant (p =0.129 and 0.457, respectively) Both SAMOVA with geographic distance following the course of the rivers (Table S4-a) and based on the Euclidean distance (Table S4-b) suggested that an organization into three groups or populations (K = 3, for both analyzes, the groups were made up of the same localities) best reflects the genetic structure of this species in the region. The explanatory variables were as follows: (a) the geographical distance between localities as indicated by the first six axes of a PCNM on the geographical distance matrix where each axis was considered as separate variables (representing IBD); (b) the basin and (c) system type (both representing IBB), as categorical variables; (d) the altitude expressed as meters above sea level; and (e) latitude expressed by decimal coordinates (both representing IBE). Out of all these combinations with significant p, the optimal model for explaining the genetic structure was chosen according to AIC
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
