Dispersal and connectivity of northeastern atlantic patellid limpets: a multidisciplinary approach

Abstract

Dispersal and connectivity of patellid limpets (Patella spp.) in the eastern North Atlantic have been examined by addressing reproductive biology, larval development, population genetics and physical modelling of dispersal. The reproductive cycles of four limpet species were assessed on the northern and central Portugese coast, to determine spawning periods. This information was incorporated into dispersal models. The results showed that P. depressa and P. ulyssiponensis have almost year-round breeding, with a brief resting phase in the early summer. Conversely, the two other species displayed much shorter spawning periods, with gamete release taking place between December and March in P. vulgata and between September and December in P. rustica. The relationship between temperature and planktonic periods in P. depressa, P. ulyssiponensis, and P. vulgata was investigated with laboratory rearing experiments. Average duration of precompetent periods varied inversely with temperature, ranging between 3.7-14.0 days in P. depressa, 2.8-13.7 days in P. ulyssiponensis and 5.7-14.6 days in P. vulgata, whilst delay periods ranged between 15.8-25.4 days in P. depressa, 14.5-27 days in P. ulyssiponensis and 16.5-25 days in P. vulgata. Population genetic structure was examined on a range-wide scale in P. depressa and along the Iberian coast in P. rustica using microsatellite markers, plus one mtDNA locus in P. rustica. Results suggested high levels of gene flow throughout the study area and widespread lack of population differentiation in both species. A biophysical model of dispersal has been developed to assess the degree of demographic connectivity over ecological and evolutionary time frames, and to identify possible barriers to dispersal for P. depressa and P. rustica. The model predicted high levels of connectivity through most of the study area in both species, but in P. depressa simulations identified two large extensions of adult habitat discontinuity as barriers to larval dispersal. The model also showed that despite the potential for long-distance dispersal, most of the larvae released at one given location settle within much shorter distances. These results illustrate the need to view the study of marine dispersal as a multidisciplinary task, and suggest that relying on just one line of evidence may produce misleading results.

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