Haplotypic diversity of Discocyrtus dilatatus Sørensen 1884 (Arachnida, Opiliones, Gonyleptidae) in Argentina.

VERGARA J, ACOSTA LE & GONZÁLEZ ITTIG RE

Punta del Este, Uruguay

Congreso; 150 years of Darwin?s Evolutionary theory: a South American Celebration; 2009

The International Union of Biological Sciences (IUBS)

Discocyrtus dilatatus is a widespread harvestman occurring in central-eastern and north-eastern Argentina, characteristic of the ?Mesopotamian sensu stricto? region, as defined by Acosta (2002). This species was reported from Cordoba province and NW Argentina as well. The presence of the species in Córdoba may be explained by the continuity of suitable habitats; in contrast, occurrences in the NW reveal a long-distance disjunction across the hostile, sub-xeric Chaco. Two hypotheses have been proposed to explain the disjunction: 1) climatic cycles in the Pleistocene, determining alternate range expansions and retractions, or 2) recent antropic introductions into the NW. Here we examine the genetic and haplotypic diversity of D. dilatatus populations, focusing in Córdoba province. We obtained sequences of the mitochondrial DNA cytochrome oxidase I gene (COI) in 34 individuals corresponding to 11 collecting sites, 8 of them in Córdoba, one in Corrientes, one in Misiones and one in Entre Ríos. The data set included approximately 681 bp; no indels were detected. Nucleotide sequences analysis showed 19 variable nucleotides and 14 phylogenetically informative sites. The average ratio of Ts:Tv (R) for CO I was 7.5. Thirteen haplotypes, a nucleotide diversity (pi) = 0,00682 and an haplotype diversity = 0,9198 were found in the D. dilatatus data set. The most common haplotypes (3, 2 and 6), and haplotype 7 were shared by different localities. Only two localities present exclusive haplotypes: Misiones and Entre Ríos. Four haplotypes showed a frequency of 1/n and represent rare alleles. The Median Joining Network showed that haplotype 3, the most frequent, is central and that five haplogroups derive from it: Haplogroup A) includes most of the haplotypes from Córdoba, HB and HC) includes haplotypes from Córdoba and Corrientes, HD) and HE) are formed by haplotypes from Entre Ríos and Misiones. These results indicate that COI is a good molecular marker to study the genetic structure of the species, towards our main objective, that is, to unravel the historical factors that shaped the disjunct pattern in D. dilatatus.