Genetic homogeneity in eight freshwater populations of Sicyopterus lagocephalus, an amphidromous gobiid of La Réunion Island

Abstract

International audienceIn the subfamily Sicydiinae of the family Gobiidae, the species Sicyopterus lagocephalus is one of the common amphidromous fish inhabiting island freshwaters in a large intertropical area, widespread from the Comoros archipelago to the Austral Islands. Eight of the main perennial rivers of La Réunion Island (Mascarene Islands) were sampled in 2000, in order to describe their population genetic structure. A total of 267 adult specimens of S. lagocephalus were screened for 14 enzymatic systems providing 15 presumptive loci, 11 of them being polymorphic. Four other loci were useful as diagnostic markers between S. lagocephalus and Cotylopus acutipinnis, a similar, closely related sympatric species. Both species constitute an economic resource locally called “bichique”. The focus of this study, S. lagocephalus, accounts for the majority of the bichique. The results clearly showed a genetic homogeneity among the eight samples (Fst tests). Within-samples tests (Fis) indicated, in general, a heterozygote deficiency. The multidimensional diagrams (CA) describe an overall structure composed of two main subgroups. This structure was not confirmed in a 2001 sampling. The interpretation of the results takes into account the biological life cycle of this species, characterized by a planktonic phase, from hatching to recruitment, followed by a freshwater life of the adults. All the samples in the survey belong to a single pool. However, the young fish entering the rivers are probably of complex origin. We did not find any isolation between rivers and this result should be considered when conservation measures are taken to prevent overfishing

Oceanic larval life of La Réunion ‘bichiques’, amphidromous gobiid post-larvae

“…(4) The results suggest a decrease in growth during the planktonic phase. These observations are in agreement with results obtained in previous genetic studies on S. lagocephalus in La Réunion and Mauritius rivers, where at least 2 sub-groups have been detected in each river (Berrebi et al 2005, Hoareau 2005). In the aforementioned studies, the most probable hypothesis was a Wahlund effect, appearing to favour the colonisation of allochthonous specimens.…”

“…Sicyopterus lagocephalus is distributed throughout the Indo-Pacific region (Watson et al 2000, Keith et al 2005a), suggesting regular connectivity between neighbouring populations. The presence of autochthonous and allochthonous specimens of S. lagocephalus in La Réunion rivers is likely and has already been suggested by Berrebi et al (2005). This would result in the mixing of several genetically distinct populations from its wide metapopulation, which would not be the case for endemic species with homogeneous populations (Hoareau 2005 innis, suggesting higher dispersal for the widespread species.…”

High gene flow due to pelagic larval dispersal among South Pacific archipelagos in two amphidromous gastropods (Neritomorpha: Neritidae)

“…Consistent with this high dispersal potential, genetic structure within high-island archipelagos is low or non-existent in amphidromous Neritid and Neritiliid snails (Hodges and Allendorf, 1998;Myers et al, 2000;Kano and Kase, 2004), as well as in Galaxiid and Sicydiine fishes (Chubb et al, 1998;Waters et al, 2000;Berrebi et al, 2005;Hoareau et al, 2007a), suggesting that populations of amphidromous species are genetically structured at scales similar to fully marine species. In contrast, fully lotic species are frequently genetically structured within watersheds or even within reaches (Bunn and Hughes, 1997;Marten et al, 2006).…”

The importance of ecosystem‐based management for conserving aquatic migratory pathways on tropical high islands: a case study from Fiji

“…Unlike salmonids in temperate systems that respond to chemical cues specific to their natal catchments (Hasler and Scholz, 1983;Dittman and Quinn, 1996), upstream migrations of amphidromous species may be cued by large pulses of fresh water (Delacroix and Champeau, 1992;Fitzsimons et al, 2002) or adult odours (Baker and Hicks, 2003), either of which would indicate viable upstream habitat. These mass migrations of juveniles support locally important, traditional fisheries (McDowall, 1984;Bell, 1999;Berrebi et al, 2005) and it is likely that they provide important seasonal input to local food webs.…”