Sympatric Australian Lasaea species (Mollusca: Bivalvia) differ in their ploidy levels, reproductive modes and developmental modes

Abstract

The cosmopolitan marine bivalve genus kisaea is predominantly composed of highly polyploid asexual lineages with one exception: the diploid, sexual Australian species L. australis. Two undescribed, direct-deireloping congeners co-occur with the indirect-developing L. austruliJ on the rocky intertidal of southeastern Australia. One of these, L. colmani sp. nov., is also diploid and sexual. The other direct-developing congener is an asexual polyploid composed of a variety of clonal lineages. All three sympatric Australian h a e a congeners are morphologically distinguishable, although prodissoconch distinctions are required to separate large polyploid clams from equivalently-sized L. australis. Similarities in mitochondria1 gene sequence and in shell morphology suggest that L. australis and the Australian sytnpatric polyploid clones share an exclusive common ancestor despite differing in developmental mode, ploidy and reproductive mode. However, detailed karyological analyses failed to identify a chromosome set morphologically similar to that of L. australis among the sympatric Australian polypoid complement. We propose that generation of the polyploid Australian clones (presumably by hybridization) was followed by radical karyological rearrangement. 0 I999 The Linnean Socier) of London ADDITIONAL

Patterns of nucleotide variation in homoeologous regulatory genes in the allotetraploid Hawaiian silversword alliance (Asteraceae)

“…1997; Mewes et al . 1997; Wolfe & Shields 1997), invertebrates (Foighil & Thiriot‐Quievreux 1999) and vertebrates (Spring 1997; Pebusque et al . 1998; McLysaght et al .…”

Phylogeny of Sphaerium solidum (Bivalvia) based on karyotype and sequences of 16S and ITS1 rDNA

“…Although B chromosomes are found in numerous species of all major groups of animals and plants, data on the occurrence of B chromosomes in bivalve molluscs are so far very scarce. Variable numbers of B chromosomes were recorded in clonal lineages of marine clams of the genus Lasea (Veneroida) [44,45]. Supernumerary chromosomes were observed in chromosome sets of Cerastoderma edule (Veneroida); these were small, much smaller than that of the smallest in the standard complement and occurred in number of 1 to 3 [46].…”

Structure and meiotic behaviour of B chromosomes in Sphaerium corneum/S. nucleus complex (Bivalvia: Sphaeriidae)

“…They have been found in some gastropod genera (Evans 1960;Patterson 1969Patterson , 1973 and in the bivalve order Veneroida (Insua and Thiriot-Quiévreux 1992;Thiriot-Quiévreux 1991, 1999). Another unusual characteristic of the order Veneroida is the occurrence of polyploidy in some genera (Lee 1999;Ó Foighil and Thiriot-Quiévreux 1999;Park et al 2000; Lee and Ó Foighil 2002). In the veneroid family Sphaeriidae, high chromosome numbers are considered a consequence of ancient allopolyploidization events (Lee and Ó Foighil 2002;Kořínková and Morávková 2010).…”