Morphology and molecular biology of freshwater decapods populations in a biogeography context from Argentina, South America

GIRI F.; WILLINER V.; COLLINS P.; RUEDA E.C.; AMAVET P; GALARZA P.; OJEDA G.

Franckfurt

Conferencia; 21 st International Senckenberg Conference. Biology of Freshwater decapods; 2010

Senckenberger Museum

In Argentina freshwater crustaceans decapods are grouped into 4 families: Sergestidae, Palaemonidae, Parastacidae, Aeglidae, Trichodactylidae. The diversity and distribution of these families is the results of evolution where have “acted” intrinsic and/or extrinsic factors. This work is presented as a synthesis of morphology and molecular studies in a biogeography context of different taxa to elucidate actual evolutionary situation. All these aspects continued being studied (morphological) and new (molecular) evidences are added with the objective of find new pieces of the puzzle that is the evolution of the freshwater decapods. The geometric morphometrics is relative new tool to study shape and size. This technique combined the geometry, the statistics and the biology, allowing the traditional methods based on distances and measures were replaced by geometric approaches. The analysis of populations genetic structure has become a useful tool since the existent genetic variability is related to the dynamics of ecological and behavioral variables in wild populations. The measurement of variation at DNA level may allow us to predict the behavior of local populations over time since a considerable level of variation increases the ability of the species to adapt to environmental changes. Populations of Aegla platensis, A. scamosa, A. riolimayana, A. uruguayana, A. neuquensis, and A. affinis (Aeglidae Family) and Trichodactylus borellinauns and T. kensleyii (Trichodactylidae Family) were studied. The geometric morphometrics approach was carried out, exclusively, using landmarks and semilandmarks. Then, the analysis of the shape was carried out principally using the TPS software package. The selection of the landmarks was different for each species, so that different configurations of landmarks and semilandmarks were explored and used. For each analysis relative warps were obtained in an exploratory way. Finally it was conducted the analysis of shapes of cephalothorax as a hole and for some species of Aeglidae considering it as a modular structure. The statistical methods used were uni and multivariate. It is well known that a population can present a unique gene combination and the genetic structure of a set of reproductively isolated populations can mutually diverge. In this way we have analyzed the genetic structure of different populations of Aegla singularis and Aegla uruguayana. The genetic variation between populations was assessed by using RAPD analysis. The results showed that population showed different shape patterns. A. scamosa, A. riolimayana and A. uruguayana presents clinal patterns while in A. platensis was not observed this pattern in relation to the distribution of populations. A. riolimayana and A. neuquensis population’s presented distributional patterns associated to pseudo-crabs inhabiting rivers vs. those living in lakes. Regarding crabs, T. borellinauns presents different shapes considering a metapopulation structure and environmental parameters in the ventral region but not in the dorsal. T. kensleyii speciemens belonging from different basins was not present statistical differences in shape. Molecular analyses considering two populations of A. singularis (from the same basin) showed no population differentiation. However, high levels of polymorphism were found in one population (Pesiguero stream) unlike the other (Coaty stream). The same analysis was performed considering 3 populations of A. uruguayana from the same metapopulation. In this case, we found significant differentiation among populations. Genetic distance showed, possibly, a clinal pattern related to colonization events. In this context, through interpretation of data which has long been working together the incorporation of new tools we began to reinterpret the evolutionary aspects of the freshwater decapods from Argentina and South America.