Genetic Structuring across Marine Biogeographic Boundaries in Rocky Shore Invertebrates

Abstract

Biogeography investigates spatial patterns of species distribution. Discontinuities in species distribution are identified as boundaries between biogeographic areas. Do these boundaries affect genetic connectivity? To address this question, a multifactorial hierarchical sampling design, across three of the major marine biogeographic boundaries in the central Mediterranean Sea (Ligurian-Tyrrhenian, Tyrrhenian-Ionian and Ionian-Adriatic) was carried out. Mitochondrial COI sequence polymorphism of seven species of Mediterranean benthic invertebrates was analysed. Two species showed significant genetic structure across the Tyrrhenian-Ionian boundary, as well as two other species across the Ionian Sea, a previously unknown phylogeographic barrier. The hypothesized barrier in the Ligurian-Tyrrhenian cannot be detected in the genetic structure of the investigated species. Connectivity patterns across species at distances up to 800 km apart confirmed that estimates of pelagic larval dispersal were poor predictors of the genetic structure. The detected genetic discontinuities seem more related to the effect of past historical events, though maintained by present day oceanographic processes. Multivariate statistical tools were used to test the consistency of the patterns across species, providing a conceptual framework for across-species barrier locations and strengths. Additional sequences retrieved from public databases supported our findings. Heterogeneity of phylogeographic patterns shown by the 7 investigated species is relevant to the understanding of the genetic diversity, and carry implications for conservation biology.

Genetic erosion in the snailLittoraria subvittata(Reid, 1986) due to mangrove deforestation

“…The repeated logging of mangroves for salt-pond construction, firewood and housing construction may also have reduced the effective population size of this species in the area due to the creation of local habitats that are not suitable for the recruitment of larvae. The extent of larval dispersal is determined by complex interactions, including oceanographic regimes and habitat quality (Villamor, Constantini & Abbiati, 2014). Selective logging may have caused reduced microhabitat complexity regarding trees and pneumatophores and resulted in an unsuitable environment for larvae and adults, which depend on them for refuge, food and development.…”

Cryptic lineages and high population genetic structure in the exploited marine snail Hexaplex trunculus (Gastropoda: Muricidae)

“…Following capture, samples were transported to the laboratory, and a small portion of foot tissue was cut and preserved in absolute ethanol at −20 °C until further processing. A hundred published cox1 sequences (GenBank accessions: KF297407-KF297433) from six Italian populations and a single specimen from Table 1 for details), Letters (A→F) are the six populations studied by Villamor et al (2014). Pie charts show the distribution of the major haplogroups for cox1 (A 1 : present study, A 2 : Villamor et al, 2014) and for i29 (B).…”

“…A hundred published cox1 sequences (GenBank accessions: KF297407-KF297433) from six Italian populations and a single specimen from Table 1 for details), Letters (A→F) are the six populations studied by Villamor et al (2014). Pie charts show the distribution of the major haplogroups for cox1 (A 1 : present study, A 2 : Villamor et al, 2014) and for i29 (B). For the cox1 sequences of Villamor et al (2014), it was not possible to distinguish haplogroups Ia and Ib due to shorter sequence length.…”

“…González-Tizón et al (2008) compared the genetic diversity of the harvested population from Ria Formosa (southern Portugal) with two adjacent populations in order to provide source populations for stock enhancement. Villamor, Costantini & Abbiati (2014) characterized Italian populations from the Ligurian, Tyrrhenian, Ionian and Adriatic Seas, encompassing putative biogeographical barriers for the cox1 marker, and reported strong genetic differentiation across the Siculo-Tunisian strait, with a potential gene flow from Ligurian-Tyrrhenian towards Ionian-Adriatic populations. However, these studies were based on a single mitochondrial marker and/or were geographically too restricted to address the genetic variability of H. trunculus across its distribution range or to identify major genetic divisions.…”

“…In addition, we included data from the six locations characterized by Villamor et al (2014) and one cox1 sequence of a specimen from Haifa (Levantine Sea) retrieved in the BOLD-system database (Ratnasingham & Hebert, 2013). On the basis of extensive sampling coverage, we investigated (1) the main phylogeographical splits and the possibility of distinct species and secondary contacts within the nominal species H. trunculus, (2) its genetic structure at a smaller geographical scale and (3) its demographic history.…”