Levels of fluctuating asymmetry in Graomys griseoflavus (2n=34-38) and Graomys centralis (2n=42) (Rodentia: Sigmodontinae)

JUAN JOSÉ MARTÍNEZ

Mendoza

Congreso; International Mammalogical Congress 10; 2009

IFM, Sarem

Developmental instability is related with stressful conditions and with high levels of fluctuating asymmetries (FA). FA comprises small and random departures from perfect symmetry and its levels may increase when chromosomal rearrangements occur. Robertsonian chromosomal polymorphism has been described in the South American Sigmodontinae rodent Graomys griseoflavus, from animals with 2n=34 to 2n=38. In order to determine levels of FA in Graomys griseoflavus, a preliminary analysis was performed on the basis of geometric morphometrics approach. For the analyses, I used twenty specimens of G. griseoflavus previously karyotyped, with 2n=36-38. Additionally, seventeen specimens of G. centralis, with 2n=42, were used for a comparative analysis of FA levels between species. Eighteen landmarks were digitized in ventral view of skull, 16 of them were paired landmarks and the other two, unpaired. The landmarks were digitized three times in different occasions and in each specimen in order to estimate measurement error. For each species, I tested whether directional asymmetries (DA) were different from zero and whether FA were significantly higher than measurement error by means of Procrustes ANOVA. Difference in FA levels between species was evaluated by mean of F-test using the mean squares of the individual-side interaction and the degrees of freedom of the corresponding Procrustes ANOVA, thus avoiding the presence of DA. In both species, the Procrustes ANOVA revealed significant DA and FA. The comparison between species showed that the degree of FA in skull shape in G. griseoflavus was significantly higher than in G. centralis. These results suggest that chromosomal rearrangements may have disrupted coadapted gene complexes, impairing developmental homeostasis and increasing FA levels. Additional studies are necessary to properly asses FA differences between those species and to compare FA levels in heterozygous and homozygous individuals of G. griseoflavus.