Abstract
The meiotic systems of some Scottish individuals of the rare Chrysolinalatecinctassp.intermedia (Franz, 1938) have been analyzed from meiotic cells at diakinesis to study the types of chromosomal bivalents and the number and locations of their chiasmata. The mean number of unichiasmate was about two-thirds and that of bichiasmate bivalents about one-third. Most chiasmata were at distal positions and there were no pairwise statistically significant differences in the mean number of chiasmata and those of unichiasmate and bichiasmate bivalents between the three surveyed geographic sources of these Scottish individuals. However, pairwise significant differences were found in the mean number of proximal + interstitial chiasmata between Loch Etive (Argyllshire) and both Orkney and Shetland Islands individuals. The presumed higher values of genetic recombination due to the proximal + interstitial chiasmata with regard to the prevailing distal ones, might provide a slight selective advantage to the insular individuals against the more extreme climates of both islands compared with the Loch Etive site.
Highlights
Chrysolina latecincta (Demaison, 1896) is a species distributed in western and central Europe from southern Norway to Spain and from Scotland to the Alps and Apennines (Kippenberg 2010)
The mean number of chiasmata per cell in Scottish Ch. latecincta were very similar in all studied individuals from the three sites, 14.4 to 14.8, due to the regular formation of a single chiasma in the seven smaller pairs of autosomes, and a varying number of one or two chiasmata in each of the four larger pairs (Table 1)
The small differences in mean total number of chiasmata and in both bichiasmate and unichiasmate bivalent numbers between Scottish individuals were not statistically significant (Table 2). These results are in agreement with those obtained in other Ch. latecincta individuals from Southern France, whose four larger autosomes correspond to 57.44% of the total complement length and are responsible for all the bichiasmate bivalents scored (Petitpierre 2000)
Summary
Chrysolina latecincta (Demaison, 1896) is a species distributed in western and central Europe from southern Norway to Spain and from Scotland to the Alps and Apennines (Kippenberg 2010). Latecincta from southern France has shown 2n = 24 chromosomes, with four large and seven small autosome pairs, plus a medium size X and a very small Y sex-chromosomes (Petitpierre 2000). In agreement with this size asymmetric karyotype the meiotic metaphases I display a male meioformula of 11 + Xyp, with four large and seven small autosome bivalents and the achiasmate “parachute-like” Xyp sex-chromosome (Petitpierre 1999). The possible differences in chiasmate systems between these Scottish individuals will be studied
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