Loss of planktotrophy and speciation: geographical fragmentation in the deep-water gastropod genusBathytoma(Gastropoda, Conoidea) in the western Pacific

Abstract

Dispersal capabilities are crucial in how speciation patterns are determined in marine invertebrates. Species possessing a long-living planktonic larva apparently have a dispersal advantage over those with non-planktotrophic development, and their distant populations may exchange genetic material, maintaining a broad geographical range for the species. Recent species of the gastropod genus Bathytoma (Conoidea) are all characterized by non-planktotrophic development, having most probably lost a free-swimming larva in the pre-Pliocene, as Miocene fossils have protoconchs indicating planktotrophic larval development. All have a bathyal distribution (100-1500 m), which implies that their capability for direct expansion on the bottom is restricted by both deep-sea basins and shallow-water areas, especially in insular West and South-West Indo-Pacific. Therefore, it can be hypothesized that Bathytoma populations should represent numerous, mostly allopatric taxa restricted to a single or contiguous island groups. We tested this hypothesis using molecular and morphological characters independently. One hundred and thirty-eight specimens from the Philippines, Solomons, Vanuatu, and the Coral Sea were sequenced for one mitochondrial (COI) and one nuclear (ITS2) gene, and 14 operational molecular units were recognized. When these molecular units are overlaid over shell characters, 13 species (11 unnamed) and one form of uncertain status are recognized: three occur in the Philippines, six in the Solomons and one in New Caledonia. Broad distributions (inter-archipelagic) are uncommon (three species). On the whole, the phylogeographic pattern of the diversity in the genus is rather complex and probably also reflects processes of sympatric and fine-scale allopatric speciation, and local extinctions. The eleven new species are described and named.

Not all spotted cats are leopards: evidence for a Hemilienardia ocellata species complex (Gastropoda: Conoidea: Raphitomidae)

“…The p-distances calculated for the 16S sequences vary from 0 to 0.027 for within-morphospecies comparisons (mean = 0.012, SD = 0.0072) and from 0.069 to 0.104 for comparisons between morphospecies (mean = 0.082, SD = 0.0109). As the between-group genetic distances (especially for the COI gene) are greater than genetic distances between closely related species of conoideans found in our earlier studies (e.g., Puillandre et al 2009Puillandre et al , 2010Fedosov & Puillandre 2012), the genetic differences found within the H. ocellata species complex support the species hypotheses based on the identified morphospecies.…”

“…Moreover, the material shows notable differences in size and number of whorls of the protoconch. The latter character is known to vary notably among closely related conoidean species (Bouchet 1990;Puillandre et al 2010), and particularly in the family Raphitomidae (Fedosov & Puillandre 2012;Fedosov & Stahlschmidt 2014). Thus, the species treated in the present study are not cryptic.…”

Phylogeny and taxonomy of theKermia–Pseudodaphnella(Mollusca: Gastropoda: Raphitomidae) genus complex: a remarkable radiation via diversification of larval development

“…Moreover, it has been demonstrated for some conoidean taxa that the switch from planctotrophic to non-planctotrophic development can give rise to adaptive radiation, especially in polar or insular regions, or in groups with narrow bathymetric distribution (Bouchet, 1990;Leal & Bouchet, 1991). Loss of planctotrophy for example, preceded radiation in the polar genus Oenopota (Bogdanov, 1989) or bathyal Indo-Pacific genus Bathytoma (Puillandre et al, 2010).…”

“…It proved useful in solving various taxonomic problems, both at the species and phylogenetic levels (Duda & Kohn, 2005;Cunha et al, 2008;Kantor et al, 2008;Puillandre et al, 2010), and for hypotheses on aspects of the biology, ecology and evolution of the group (Williams & Duda, 2008;Duda & Lee, 2009;Castelin et al, 2012). Many groups of turrids, however, remain unstudied at the molecular level, among which Raphitomidae is of particular importance.…”

Possible Poecilogony Due to Discontinuous Multifactorial Inheritance in Some Mediterranean Species of Raphitoma (Mollusca, Conoidea, Raphitomidae)

“…In addition, it has been demonstrated that the switch in some conoidean taxa from the planktotrophic to the non-planktotrophic development has increased their adaptive radiation, especially in polar or insular region, or in groups with narrow bathymetric distribution [3,7]. In the case of Oenopota elongata Bogdanov, 1989, and in the polar genus or bathyal IndoPacific genus Bathytoma Harris & Burrows, 1891, the loss of planktotrophy actually preceded adaptive radiation [8][9][10][11].…”