PatelGene - Genetic Structure of Azorean Limpets: Implications for Conservation and Marine Protected Areas

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Ecological, biological and molecular considerations towards the sustainable exploitation of limpets in macaronesia (NE-Atlantic)

Publication . Faria, Joao; Cabral, Henrique N., 1969-

The uptake of natural living resources for human consumption has triggered serious changes in the balance of ecosystems. In the archipelagos of Macaronesia (NE Atlantic), limpets have been extensively exploited probably since islands were first colonized. This has led to profound consequences in the dynamics of rocky shore communities. The specific objectives of this thesis were to: 1) develop and characterize species-specific microsatellite markers for the limpets Patella candei (d’Orbigny 1840) and Patella aspera (Röding 1798), endemic to the Macaronesia archipelagos; 2) assess their genetic diversity, population structure and contemporary levels of connectivity throughout Macaronesia; 3) conduct a morphometric analysis of the P. candei complex to complement molecular data; 4) evaluate the temporal and spatial variation in recruitment of P. candei and study its association with real-time environmental data; 5) assess the effect of temperature on larval development of P. candei; and 6) provide general recommendations to foster the sustainable exploitation of limpets in Macaronesia. A total of twelve and seventeen microsatellite markers were described for P. candei and P. aspera, respectively. These showed clean polymorphisms and speciesspecific markers were combined in three optimized multiplex reactions. For P. candei, a highly significant genetic break between archipelagos following isolation by distance was detected. Contrastingly, significant genetic differentiation among islands (i.e. Azores) was absent possibly indicating ongoing gene flow via larval exchange between populations. Significant shell shape differences among archipelagos were also detected using both distance-based and geometric morphometric analyses. Adaptive processes associated with niche differentiation and strong barriers to gene flow among archipelagos may be the mechanisms underlying P. candei diversification in Macaronesia. As for P. aspera, genetic analyses showed significant population structure between populations from Azores and populations from Madeira and Canaries, and absence of current or historic gene flow between these. Results also suggest that both population clusters have experienced demographic changes over time. Heterozygote deficits were common across populations, which can be better accounted for by inbreeding than by null alleles or Wahlund effect. Such levels of inbreeding are likely a consequence of a significant reduction of reproductive units due to decades of intense exploitation. The monitoring program applied to track P. candei recruitment showed that early recruits occurred throughout the entire duration of the program, but its intensity varied in space and time. In general, a marked peak in recruitment occurred during winter/spring months, the period of greatest reproductive activity, when sea surface temperatures are lower and wave turbulence higher. Significant wave height was probably the most important proximate cue triggering the recruitment of P. candei, which eventually depends on adequate ultimate drivers for spawning and reproduction (i.e. temperature). Indeed, as a winter-breeder, P. candei larvae seem to perform better and attain higher fitness at colder temperatures. In fact, experimental treatments on larval rearing showed that larval development was faster at increasing temperatures but cumulative survivorship decreased; about 25% of larvae at higher temperatures survived to the end of the experiment, a 2-fold decrease from the average survivorship of ~ 50% at lower temperatures. Overall, the outcomes of this thesis fill a gap in our knowledge about processes involved in determining the connectivity patterns between limpet populations and the environmental factors influencing such patterns across the Macaronesia region. The present study is an important first step in this direction of using multi-faceted approaches to understand complex processes operating at the marine environment, while providing a fundamental asset to define stocks and thus inform specific conservation strategies that foster the sustainable exploitation of limpets throughout Macaronesia archipelagos.

2018Tese de doutoramento

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

5876-PPCDTI

Número da atribuição

PTDC/BIA-BIC/115837/2009