Open AccessCharacteristics of B‐chromosomes in Galetucella nymphaeae species complex (Coleoptera, Chrysomelidae)
Author(s) -
NOKKALA CHRISTINA,
NOKKALA SEPPO
Publication year - 1989
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.1989.tb00393.x
Subject(s) - chiasma , biology , b chromosome , meiosis , population , genetics , euchromatin , chromosome , mitosis , anaphase , evolutionary biology , karyotype , heterochromatin , demography , gene , sociology
Characteristics of B‐chromosomes were studied in 12 populations of Galerucella nymphaeae (11 Finnish and one Swedish) and 21 populations of G. sagittariae (20 Finnish and one Swedish). B‐chromosomes were found in varying frequencies in all but one population studied. Though varying in size, all B's seemed to be largely euchromatic, able to form chiasmata, and isopycnotic during meiotic prophase. According to their behavior at mitosis, B's could be classified as stable and unstable. The presence of B's did not affect chiasma frequency in G. sagittariae , while in G. nymphaeae chiasma frequency was increased if either B's or an unusually large Y chromosome was present. Most individuals possessing stable B‐chromosomes were found to carry 2 B's. It was found that the shape of B‐chromosome distribution and B‐chromosome frequency in a population are not interdependent and they are determined by different factors. It seems that the shape of the distribution of B's is created by their mitotic and meiotic properties, while the frequency of B‐chromosomes in a population is determined by external factors, selection or random processes.