Abstract
The haploid DNA content of Aeshna confusa (2n = 27, n = 13 + XO, male). A. bonariensis (2n = 26, n = 12 + neo-XY, male) and A. cornigera planaltica (2n = 16, n = 7 + neo-XY, male) has been determined (2.16 ± 0.16 pg, 1.81 ± 0.17 pg, and 2.08 ± 0.08 pg, respectively). Despite the differences in chromosome size and number, differences in DNA content between species are not significant. The karyotypic analysis of Aeshna species leads to the conclusion that fusions between autosome.s or autosome and the sex chromosome, are the only chromosome rearrangement that occurred during evolution. In the species here studied, fusions have taken place with a minimal loss of DNA; however, other species of the genus show important differences in genome size, which cannot only be justified by fusion events.
Highlights
(2.16 i0.16 pg, 1.81 k 0.17 pg, and 2.08 k 0.08 pg, respectively)
The karyotypic analysis of,4e.shnu species leads to the conclusion that fusions between autosomes or autosome and thc scx chromosome, are the only chromosome rearrangement that occurred during evolution
In the species here studied, fusions have taken place with a minimal loss of DNA; other species of the genus show important differences in genome size, which cannot only he justified by fusion events
Summary
The chromosome complement and meiotic behaviour of the three specics havc been previously describcd in detail (MOLA 1992). The principal features of the karyotype of these species can be summarized as follows: Aeshna confusu + n = 13 XO) has a larger bivalent and a very small one (m bivalent), while the other eleven bivalents decrease gradually in size. The X chromosomc is larger than the m bivalent and of similar sizc to the second smallest one (Fig. la). Bonariensis (2n = 26, n = 12 neo-XY), the autosomal bivalents decrease gradually in size, except for the very small nz bivalent; the neo-XY is the largest bivalent and is heteromorphic (Fig. Ib). Has a reduced chromosome number and larger chromosomes than the Cormer two species. The autosomal bivalents can be grouped in five largc and two small ones, while the sex chromosome bivalent is the smallest one and noticeably heteromorphic (Fig. lc)
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