Abstract
SUMMARY: The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is distributed from the Ghana coast to the Iberian Peninsula, being particularly abundant on the south coast of Portugal. The differentiation of this species along the Portuguese coast was assessed through the analysis of 10 samples, considering morphological characters (20 morphometric and 16 meristic) and genetic markers (10 allozymes, 11 loci). Southern samples included estuaries and their adjacent coastal areas, given that this species inhabits both environments, whereas western samples only comprised estuaries. Morphometric and meristic data discriminant analysis evidenced some differentiation between estuarine and coastal populations. This was not entirely corroborated by the genetic analysis, which showed an overall pattern of low FST (0.042) and Nei’s genetic distance, even between geographically distant areas. However, higher values of these parameters were found between estuaries of the south coast and their adjacent coastal areas, suggesting that estuarine systems play a major role in such differentiation. Results are discussed regarding toadfish life-history pattern and Portuguese coast geomorphology, giving an insight into the biological and environmental factors influencing population sub-structuring.
Highlights
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801) (Batrachoididae) is a sedentary benthic species that lives down to about50 m, inhabiting the eastern Atlantic from Ghana to the Iberian Peninsula (Roux, 1986)
On the western coast it occurs only in estuaries but on the south coast it occurs in both estuaries and coastal areas (Costa, 1993)
Research on the genetic diversity and differentiation of this species using allozymes suggested that the morphological differentiation observed in the lagoon of Venice was related to population structuring (Stefanni et al, 1996; 2003)
Summary
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801) (Batrachoididae) is a sedentary benthic species that lives down to about50 m, inhabiting the eastern Atlantic from Ghana to the Iberian Peninsula (about 39oN) (Roux, 1986). This species’ life history suggests a low flux of individuals, even between close areas, since males nest under rocks or in crevices defending the clutch (Santos et al, 2000). This is expected to result in a differentiation by genetic drift, inbreeding or, as suggested by Beheregaray and Sunnucks (2001) for species that inhabit coastal and estuarine regions, “divergence-with-gene-flow”. Within the family Batrachoididae population sub-structuring has been described for Opsanus tau Linnaeus, 1758 and Opasanus beta Goode and Bean, 1879 inhabiting each side of cape Hatteras on the western Atlantic coast (Avise et al, 1987). Considerable genotypic diversity and differentiation was observed within each species due to the constrained gene flux between populations
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