At least some meiofaunal species are not everywhere. Indication of geographic, ecological and geological barriers affecting the dispersion of species of Ototyphlonemertes (Nemertea, Hoplonemertea)

Abstract

Most meiofaunal species are known to have a broad distribution with no apparent barriers to their dispersion. However, different morphological and/or molecular methods supported patterns of diversity and distribution that may be different among taxa while also conflicting within the same group. We accurately assessed the patterns of geographic distribution in actual genetic species of a marine meiofaunal animal model: Ototyphlonemertes. Specimens were collected from several sites around Europe, Northern and Central America, Southern America, Pacific Islands and Asia. We sequenced regions of two mitochondrial and two nuclear genes. Using single-gene, a concatenated data set, multilocus approaches and different DNA taxonomy methods, we disentangled the actual diversity and the spatial structures of haplotypes and tested the possible correlation between genetic diversity and geographic distance. The results show (i) the importance of using several genes to uncover both diversity and highlight phylogeographic relationships among species and that (ii) independent genetic evolutionary entities have a narrower distribution than morphological species. Moreover, (iii) a Mantel test supported a positive correlation between genetic and geographical distance. By sampling from the two sides of Isthmus of Panama, we were additionally able to identify lineage divergence times that are concordant with vicariance mechanisms caused by the geological closure of the seaway across the Isthmus. We therefore propose that in addition to distance, other geological and ecological conditions are also barriers to the dispersion of and gene flow in marine meiofaunal organisms.

Interstitial annelids from the Caribbean Coast of Colombia

“…Therefore, it is also likely that the apparently broad distribution range exhibited by many of the species here recorded are in fact an artifact of the lack of such studies, which might reveal that several of these taxa represent in fact complexes of species (Westheide, 1971;Westheide & Rieger, 1987;Von Soosten et al, 1998). Cosmopolitan complexes of cryptic species have been already shown for several species of meiofaunal metazoans without larvae such as nemerteans (Leasi, Andrade, & Norenburg, 2016), gastrotrichs (Leasi & Todaro, 2009), nemertodermatids (Meyer-Wachsmuth, Curini-Galletti, & Jondelius, 2014) and annelids such as Hesionides gohari (Westheide, 1974;Schmidt & Westheide, 1999), Microphthalmus listensis (Westheide & Rieger, 1987), Nerilla antennata, (Goodrich, 1912;Schmidt & Westheide, 1997/98), and Petitia amphophtalma (Westheide & Hass-Cordes, 2001;Westheide & Schmidt, 2003). Nevertheless, real cosmopolitan species also exist, as seems to be the case of Hesionides arenaria (Schmidt & Westheide, 2000).…”

Histology-free Descriptions for Seven Species of Interstitial Ribbon Worms in the Genus <i>Ototyphlonemertes</i> (Nemertea: Monostilifera) from Vietnam

“…Ototyphlonemertes duplex species group. The Duplexmorph of Envall and Norenburg (2001) was corroborated by Leasi et al's (2016) Corrêa, 1948;and O. (duplex) martynovi Chernyshev, 1993. Ototyphlonemertes macintoshi species group.…”

Echinoderes pterus sp. n. showing a geographically and bathymetrically wide distribution pattern on seamounts and on the deep-sea floor in the Arctic Ocean, Atlantic Ocean, and the Mediterranean Sea (Kinorhyncha, Cyclorhagida)

“…Such wide distribution patterns have been explained or hypothesized by the stepping stone hypothesis (George 2013; Packmor and Riedl 2016), artificial dispersal (artificial invasion) (Herranz and Leander 2016; Pardos et al 2016; Cvitković et al 2017), or long range dispersal using currents and/or drifting (Walters and Bell 1994; Neuhaus and Sørensen 2013; Neuhaus et al 2014; Yamasaki et al 2014). Some are even regarded as a pseudo-wide distribution via the detection of cryptic species (Jörger et al 2012; Leasi et al 2016). …”