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Holarctic phylogeography of an asexual species complex – II. Allozymic variation and clonal structure in Arctic Daphnia
Author(s) -
Weider Lawrence J.,
Hobæk Anders,
Hebert Paul D. N.,
Crease Teresa J.
Publication year - 1999
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1046/j.1365-294x.1999.00522.x
Subject(s) - biology , holarctic , phylogeography , daphnia pulex , restriction fragment length polymorphism , vicariance , population , introgression , mantel test , population genetics , biological dispersal , genetics , evolutionary biology , ecology , genetic variation , daphnia , phylogenetics , genotype , gene , demography , crustacean , sociology , genus
Previous mitochondrial (mt)DNA sequencing and restriction fragment length polymorphism (RFLP) studies have shown that the Holarctic Daphnia pulex complex is divisible into two major groups ( pulicaria and tenebrosa ) that exhibit distinct phylogeographic patterns. Here we examine allozymic variation at six polymorphic enzyme loci to ascertain clonal structure and clonal distribution patterns within each group. Specimens were collected from a total of 850 populations encompassing the Arctic. A significant negative relationship (Mantel test) between similarity of regional clonal arrays and geographical distance was observed. A small fraction of clones in each group was widespread (in the order of 1000s of kilometres). However, most clones were restricted to single regions, and were often found only in a single population. These data indicate that the population genetic structure is highly fragmented in this complex, but the potential for long‐distance passive dispersal exists. Further, ‘hot spots’ of high clonal richness and diversity were found in each group, which is concordant with earlier work. In addition, ≈ 20% of pulicaria group clones possess nuclear genes from tenebrosa , while approximately 10% of tenebrosa group clones harbour pulicaria nuclear genes. These data indicate nuclear introgression between the two groups, which was found to be prominent in a broad zone of secondary contact encompassing parts of northwestern Russia, northern Fennoscandia, Svalbard, and extending into the high eastern Canadian Arctic.