Abstract
The Harpacticoid copepod Tigriopus brevicornis belongs to the meiofauna of intertidal rock pools and is distributed widely along European coasts. Sixteen sites were sampled from the Irish Sea to the coasts of Spain. We used the ITS1 marker to analyse the relationship between the populations because it shows low intrapopulational variation (mean pairwise difference: 1.00 ± 0.8) and high interpopulational divergence (mean pairwise difference: 16.38 ± 7.39). A total of 57 bp out of 433 bp were recognised as informative nucleotides among the 61 individuals analysed. The analysis of the genetic relationships highlighted a north-south split in the distribution of the natural populations and showed a genetic break point around the Gironde estuary, which is probably due to differences in the geomorphologic characteristics of the coastal area on the two different sides of this estuary. Various populations were isolated and the ITS1 sequences indicated that there are specific genetic signatures in these populations. The northern set of populations, which was sampled along a large rocky coastline, had a metapopulation structure with genetic exchanges between geographically close populations and also between geographically far ones. The southern set of populations, which was sampled in small rocky pools on large sandy beaches, showed isolated populations as a consequence of the geomorphology of the area.
Highlights
Some physical factors, such as current patterns, may restrict or promote dispersal routes, oceans often appear to be free from gene flow barriers, and this limits our ability to understand the genetic exchange between the marine invertebrate populations
SUMMARY: The Harpacticoid copepod Tigriopus brevicornis belongs to the meiofauna of intertidal rock pools and is distributed widely along European coasts
We used the ITS1 marker to analyse the relationship between the populations because it shows low intrapopulational variation and high interpopulational divergence
Summary
Some physical factors, such as current patterns, may restrict or promote dispersal routes, oceans often appear to be free from gene flow barriers, and this limits our ability to understand the genetic exchange between the marine invertebrate populations. In the case of the marine invertebrates with a free-swimming stage (larvae and/or adult), the relationships between populations could be used to study the dispersal behaviour and the ability of species to recolonise highly variable environments. Distribution analyses of copepod populations have shown various degrees of differentiation over short distances (less than 1 km) (Burton and Feldmann, 1983; Burton, 1990; 1998; Burton and Lee, 1994) and over long distances (hundred of kilometres) (Burton, 1998; Schizas et al, 1999). In the latter case, the results suggest a distinct geographic pattern with breaks in the genetic composition. The divergence observed in the spacer regions was appropriate for detecting differences between conspecific organisms and provided a useful marker for studying the relationships between populations (Vogler and DeSalle, 1994)
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