Community Structure and Population Genetics of Eastern Mediterranean Polychaetes
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Frontiers - Publisher Connector ORIGINAL RESEARCH ARTICLE published: 06 October 2014 MARINE SCIENCE doi: 10.3389/fmars.2014.00047 Community structure and population genetics of Eastern Mediterranean polychaetes Giorgos Chatzigeorgiou 1,2*, Elena Sarropoulou 2, Katerina Vasileiadou 2, Christina Brown 3, Sarah Faulwetter 2, Giorgos Kotoulas 2 and Christos D. Arvanitidis 2 1 Biology Department, University of Crete, Heraklion, Greece 2 Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion, Greece 3 Department of Biology, Chemistry and Pharmacology, Institute of Biology, Free University of Berlin, Berlin, Germany Edited by: Species and genetic diversity are often found to co-vary since they are influenced by Alberto Basset, University of external factors in similar ways. In this paper, we analyse the genetic differences of the Salento, Italy abundant polychaete Hermodice carunculata (Pallas, 1766) during two successive years Reviewed by: at two locations in northern Crete (Aegean Sea) and compare them to other populations Guillem Chust, AZTI-Tecnalia, Spain Katherine Dafforn, University of in the Mediterranean Sea and the Atlantic Ocean. The genetic analysis is combined with New South Wales, Australia an analysis of ecological divergence of the total polychaete community structure (beta *Correspondence: diversity) at these locations. The phylogenetic analysis of all included H. carunculata Giorgos Chatzigeorgiou, Hellenic populations revealed two main clades, one exclusively found in the Mediterranean and Centre for Marine Research, a second occurring in both the Mediterranean and the Atlantic. Genetic diversity indices Institute of Biology Biotechnology and Aquaculture, Former American reveal unexpectedly high differences between the two Cretan populations, despite the Base at Gournes, 71500 Crete, absence of apparent oceanographic barriers. A similarly high divergence, represented by Greece a high beta diversity index, was observed between the polychaete communities at the e-mail: [email protected] two locations. This comparatively high divergence of the genetic structure of a dominant species and the total polychaete community might be explained by the strong influence of local environmental factors as well as inter-specific interactions between the dominance of a single species and the members of the community. Keywords: Hermodice carunculata, mtCOI, NaGISA, rocky shore, beta diversity, fixation index INTRODUCTION species (http://www.barcodeoflife.org/) and population genetic The marine environment provides many opportunities for dis- analysis (e.g., Avise, 1994; Galtier et al., 2009). For instance, persal of individuals within and among populations (Cowen mtDNA data have been widely used to assess the temporal and and Sponaugle, 2009). Benthic invertebrate taxa usually have spatial fluctuations of haplotype diversity in natural populations. very limited dispersal potential as adults, whereas many species Many studies investigate cryptic species along environmental gra- have pelagic larval stages that facilitate dispersal (Weersing and dients (e.g., Jolly et al., 2005; Barroso et al., 2010), but few focus Toonen, 2009). The dispersal ability of a taxon is directed by on the population structure within a specified area (e.g., Schulze a number of factors such as historical processes, environmental et al., 2000; Craft et al., 2010; Chust et al., 2013). conditions, currents and life history traits such as the duration of At the community level, a series of mathematical approaches the larval stage (Pringle and Wares, 2007; Jolly et al., 2009). These and indices exist to calculate quantitative estimates of divergence. factors can lead to a variety of distribution pattens—from cos- Whittaker (1960) introduced the term “beta diversity” (often mopolitan distributions of species to the existence of populations referred to as turnover diversity) to describe the diversification with significant genetic differences even at close geographic dis- between assemblages within a certain geographic area. Since then, tances (Hohenlohe, 2004; Hart and Marko, 2010; Derycke et al., 24 different (dis-)similarity coefficients have been proposed to 2013; Iacchei et al., 2013; Vergara-Chen et al., 2013). quantify beta diversity (Legendre and Cáceres, 2013). The evolution of genetic diversity patterns depends mostly There is a conceptual analogy between beta diversity of com- on the interplay of mutation, random genetic drift, gene flow munity structure and genetic divergence between populations of and natural selection (Hartl and Clark, 2007). These processes a species. Theory predicts that environmental and stochastic pro- can be studied through population genetics and phylogeographic cesses act at all levels of the biological organization and thus cause approaches (Derycke et al., 2013). Over the last two decades, species diversity and genetic diversity to co-vary in time and space the development of molecular techniques has allowed the in- (Etienne and Olff, 2004; Vellend and Geber, 2005). A number of depth study of population structure and dynamics in benthic studies have identified the parallel influence of local processes on invertebrates (e.g., Duran et al., 2004). Mitochondrial genes and species and genetic diversity (e.g., Vellend, 2003; Papadopoulou especially the cytochrome c oxidase subunit I (mtCOI) are widely et al., 2011), as well as the mutual shaping of community diversity used and have been proved useful for both DNA barcoding of and the genetic diversity of its members (e.g., Booth and Grime, www.frontiersin.org October 2014 | Volume 1 | Article 47 | 1 Chatzigeorgiou et al. Combining two different levels of biodiversity 2003; Whitham et al., 2003; Hughes et al., 2008). If these theo- ries hold true, beta diversity and population genetic diversity can be expected to change at similar rates between locations. Indeed, Baselga et al. (2013) have found such correlations in communities of water beetles across Europe, and Papadopoulou et al. (2011) revealed that beta diversity and haplotype diversity of tenebri- onid beetle communities on the Aegean Islands declined at similar rates with increasing distances. Furthermore, there are strong indications that the genetic diversity of a single species can have effects on the diversity of a whole community if that species has a dominant or keystone role in the ecosystem (Treseder and Vitousek, 2001; Whitham et al., 2003). If the genetic diversity of certain species is shown to change at similar rates to the species diversity of a commu- nity, these species could be used as a proxy for time-consuming and costly whole-community analyses (e.g., Féral et al., 2003). FIGURE 1 | Map of the study sites, located in Crete: Alykes in the In this paper, we analyse the genetic differences of the abundant central part of the island and Elounda in the eastern part. polychaete Hermodice carunculata (Pallas, 1766)duringtwosuc- cessive years at two locations in northern Crete (Aegean Sea). removed and the remaining tissues were first cleaned and then The results are combined with an analysis of ecological divergence processed for the analysis (Vasileiadou et al., 2012). of the total polychaete community structure between these loca- tions. This allows us to assess to what extent the genetic diversity ECOLOGICAL ANALYSES of a single, dominant species reflects the overall community diver- For the purpose of this study, the original dataset was modi- sity, and provides a basis for the future exploration of such species fied by combining the abundances of each depth, and analyses as biological indicators. of beta diversity were based on the total species pool in each loca- tion per year. Although many indices have been suggested, the bw MATERIALS AND METHODS (Whittaker, 1960; Magurran, 1988; Southwood and Henderson, STUDY AREA 2000)was selected as the most suitable for comparing geographic The analysis was based on samples collected previously in variation among populations, according to Wilson and Shmida the framework of the NaGISA project [http://www.coml.org/ (1984). The following equation was used: projects/natural-geography-shore-areas-nagisa; datasets were published by Faulwetter et al. (2011) and Chatzigeorgiou et al. bw = [(a + b + c) / (2a + b + c) /2] − 1, (2014)]. Samples were taken from two locations in northern Crete, Alykes and Elounda (35.41583, 24.98785; 35.25166, where, 25.75833; Figure 1). Both locations are characterized by a moder- a is the total number of species occurring in both sampling ate wave exposure and a continuous hard bottom habitat, densely locations, b the total number of species occurring only in the first covered by algae, with Cystoseira spp. and Sargassum spp. being sampling location and c the total number of species occurring the most abundant in terms of surface coverage. The locations only in second location. The beta diversity between two locations are60kmawayfromeachotherandtheyseemtoreceiveno can assume values between zero (complete similarity) and one detectable impact caused by human activities (Chatzigeorgiou (complete dissimilarity) (Koleff et al., 2003). et al., 2012). A Mann-Whitney test (Mann and Whitney, 1947)was applied in order to test for differences between the measured SPECIMEN COLLECTION AND PROCESSING morphological characters of the individuals belonging to the two Sampling was conducted following the NaGISA protocol (Iken