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MULTIPLE ORIGINS OF SEX CHROMOSOME FUSIONS CORRELATED WITH CHIASMA LOCALIZATION IN HABRONATTUS JUMPING SPIDERS (ARANEAE: SALTICIDAE)
Author(s) -
Maddison Wayne P.,
LeducRobert Geneviève
Publication year - 2013
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12109
Subject(s) - chiasma , biology , autosome , meiosis , genetics , x chromosome , evolutionary biology , chromosome , gene
Entelegyne spiders rarely show fusions yielding neo‐Y chromosomes, which M. J. D. White attributed to a constraint in spiders, namely their proximal chiasma localization acting to upset meiotic segregation in males with fusions. Of the 75 taxa of Habronattus and outgroups studied, 47 have X 1 X 2 0 sex chromosomes in males, 10 have X 1 X 2 Y, 15 have X 1 X 2 X 3 Y, 2 have X0, and one has both X 1 X 2 0 and X 1 X 2 X 3 Y. Chromosome numbers and behavior suggest neo‐Ys formed by an autosome‐X fusion to make X 1 X 2 Y, with a second fusion to an autosome to make X 1 X 2 X 3 Y. Phylogeny shows at least 8–15 gains (or possibly some losses) of neo‐Y (i.e., X‐autosome fusions), a remarkable number for such a small clade. In contrast to the many X‐autosome fusions, at most one autosome–autosome fusion is indicated. Origins of neo‐Y are correlated significantly with distal localization of chiasmata, supporting White's hypothesis that evolution of neo‐Y systems is facilitated by looser pairing (distal chiasmata) at meiosis. However, an alternative (or contributing) explanation for the correlation is that X‐autosome fusions were selected to permit isolation of male‐favored alleles to the neo‐Y chromosome, aided by distal chiasmata limiting recombination. This intralocus sexual conflict hypothesis could explain both the many X‐autosome fusions, and the stunning complexity of male Habronattus courtship displays.