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Characterization of ten highly polymorphic microsatellite loci for the intertidal mussel Perna perna, and cross species amplification within the genus

Publication . Coelho, Nelson; I Zardi, Gerardo; Pearson, G. A.; Serrão, Ester; Nicastro, Katy R

The brown mussel Perna perna (Linnaeus, 1758) is a dominant constituent of intertidal communities and a strong invader with multiple non-native populations distributed around the world. In a previous study, two polymorphic microsatellite loci were developed and used to determine population-level genetic diversity in invasive and native P. perna populations. However, higher number of microsatellite markers are required for reliable population genetic studies. In this context, in order to understand P. perna origins and history of invasion and to compare population genetic structure in native versus invaded areas, we developed 10 polymorphic microsatellite markers. Findings Described microsatellite markers were developed from an enriched genomic library. Analyses and characterization of loci using 20 individuals from a population in Western Sahara revealed on average 11 alleles per locus (range: 5–27) and mean gene diversity of 0.75 (range: 0.31 - 0.95). One primer pair revealed possible linkage disequilibrium while heterozygote deficiency was significant at four loci. Six of these markers cross-amplified in P. canaliculus (origin: New Zealand). Conclusions Developed markers will be useful in addressing a variety of questions concerning P. perna, including dispersal scales, genetic variation and population structure, in both native and invaded areas.

2012-10-08Journal article

Open Access

Love thy neighbour: group properties of gaping behaviour in mussel aggregations

Publication . Nicastro, Katy R; I Zardi, Gerardo; McQuaid, C. D.; Pearson, G. A.; Serrão, Ester

By associating closely with others to form a group, an animal can benefit from a number of advantages including reduced risk of predation, amelioration of environmental conditions, and increased reproductive success, but at the price of reduced resources. Although made up of individual members, an aggregation often displays novel effects that do not manifest at the level of the individual organism. Here we show that very simple behaviour in intertidal mussels shows new effects in dense aggregations but not in isolated individuals. Perna perna and Mytilus galloprovincialis are gaping (periodic valve movement during emersion) and non-gaping mussels respectively. P. perna gaping behaviour had no effect on body temperatures of isolated individuals, while it led to increased humidity and decreased temperatures in dense groups (beds). Gaping resulted in cooler body temperatures for P. perna than M. galloprovincialis when in aggregations, while solitary individuals exhibited the highest temperatures. Gradients of increasing body temperature were detected from the center to edges of beds, but M. galloprovincialis at the edge had the same temperature as isolated individuals. Furthermore, a field study showed that during periods of severe heat stress, mortality rates of mussels within beds of the gaping P. perna were lower than those of isolated individuals or within beds of M. galloprovincialis, highlighting the determinant role of gaping on fitness and group functioning. We demonstrate that new effects of very simple individual behaviour lead to amelioration of abiotic conditions at the aggregation level and that these effects increase mussel resistance to thermal stress.

2012Journal article

Open Access

Behind the mask: cryptic genetic diversity of Mytilus galloprovincialis along southern European and northern African shores

Publication . Lourenço, Carla R.; Nicastro, Katy; Serrao, Ester A.; Castilho, Rita; Zardi, Gerardo

Morphological uniformity in geographically widespread species may cause genetically distinct entities to pass unnoticed if they can only be detected by molecular approaches. The importance of uncovering such cryptic diversity is prompted by the need to understand the putative adaptive potential of populations along species ranges and to manage biodiversity conservation efforts. In this study, we aim to assess cryptic intraspecific genetic diversity and taxonomic status of the widely distributed intertidal mussel Mytilus galloprovincialis, along Atlantic southwestern (SW) Iberian, Atlantic northwestern (NW) Moroccan and Mediterranean Tunisian shores. By using mitochondrial (16S restriction-fragment length polymorphism) and nuclear (polyphenolic adhesive protein gene, Glu-5') markers, we discovered a more complex taxonomic diversity of M. galloprovincialis than previously known. Both Atlantic and Mediterranean haplogroups of M. galloprovincialis were detected along Atlantic SW Iberian shores along with M. galloprovincialis/edulis hybrids (92.2% Atlantic, 3.9% Mediterranean and 3.9% hybrids). In contrast, NW Moroccan populations consisted solely of Atlantic M. galloprovincialis. The Mediterranean populations did not include M. galloprovincialis/ edulis hybrids, but both Atlantic (58%) and Mediterranean (42%) lineages were detected. Divergent selection between coastlines and/or indirect larval dispersal by human activities may be the drivers of this geographically structured genetic diversity.

2015-08Journal article

Open Access

Intraspecific genetic lineages of a marine mussel show behavioural divergence and spatial segregation over a tropical/subtropical biogeographic transition

Publication . Zardi, Gerardo I.; Nicastro, Katy R; McQuaid, C. D.; Castilho, Rita; Costa, Joana; Serrão, Ester; Pearson, G. A.

Background: Intraspecific variability is seen as a central component of biodiversity. We investigated genetic differentiation, contemporary patterns of demographic connectivity and intraspecific variation of adaptive behavioural traits in two lineages of an intertidal mussel (Perna perna) across a tropical/subtropical biogeographic transition. Results: Microsatellite analyses revealed clear genetic differentiation between western (temperate) and eastern (subtropical/tropical) populations, confirming divergence previously detected with mitochondrial (COI) and nuclear (ITS) markers. Gene flow between regions was predominantly east-to-west and was only moderate, with higher heterozygote deficiency where the two lineages co-occur. This can be explained by differential selection and/or oceanographic dynamics acting as a barrier to larval dispersal. Common garden experiments showed that gaping (periodic closure and opening of the shell) and attachment to the substratum differed significantly between the two lineages. Western individuals gaped more and attached less strongly to the substratum than eastern ones. Conclusions: These behavioural differences are consistent with the geographic and intertidal distributions of each lineage along sharp environmental clines, indicating their strong adaptive significance. We highlight the functional role of diversity below the species level in evolutionary trends and the need to understand this when predicting biodiversity responses to environmental change.

2015-05-31Journal article

Open Access