Ricardo García-Jiménez

Extremely reduced dispersal and gene flow in an island bird

The Réunion grey white-eye, Zosterops borbonicus, a passerine bird endemic to Réunion Island in the Mascarene archipelago, represents an extreme case of microgeographical plumage colour variation in birds, with four distinct colour forms occupying different parts of this small island (2512 km2). To understand whether such population differentiation may reflect low levels of dispersal and gene flow at a very small spatial scale, we examined population structure and gene flow by analysing variation at 11 microsatellite loci among four geographically close localities (<26 km apart) sampled within the distribution range of one of the colour forms, the brown-headed brown form. Our results revealed levels of genetic differentiation that are exceptionally high for birds at such a small spatial scale. This strong population structure appears to reflect low levels of historical and contemporary gene flow among populations, unless very close geographically (<10 km). Thus, we suggest that the Réunion grey white-eye shows an extremely reduced propensity to disperse, which is likely to be related to behavioural processes.

The role of selection and historical factors in driving population differentiation along an elevational gradient in an island bird

Adaptation to local environmental conditions and the range dynamics of populations can influence evolutionary divergence along environmental gradients. Thus, it is important to investigate patterns of both phenotypic and genetic variations among populations to reveal the respective roles of these two types of factors in driving population differentiation. Here, we test for evidence of phenotypic and genetic structure across populations of a passerine bird (Zosterops borbonicus) distributed along a steep elevational gradient on the island of Réunion. Using 11 microsatellite loci screened in 401 individuals from 18 localities distributed along the gradient, we found that genetic differentiation occurred at two spatial levels: (i) between two main population groups corresponding to highland and lowland areas, respectively, and (ii) within each of these two groups. In contrast, several morphological traits varied gradually along the gradient. Comparison of neutral genetic differentiation (FST) and phenotypic differentiation (PST) showed that PST largely exceeds FST at several morphological traits, which is consistent with a role for local adaptation in driving morphological divergence along the gradient. Overall, our results revealed an area of secondary contact midway up the gradient between two major, cryptic, population groups likely diverged in allopatry. Remarkably, local adaptation has shaped phenotypic differentiation irrespective of population history, resulting in different patterns of variation along the elevational gradient. Our findings underscore the importance of understanding both historical and selective factors when trying to explain variation along environmental gradients.

Development of Microsatellite Markers as a Molecular Tool for Conservation Studies of the Mediterranean Reef Builder Coral Cladocora caespitosa (Anthozoa, Scleractinia)

Cladocora caespitosa is a reef-building zooxanthellate scleractinian coral in the Mediterranean Sea. Mortality events have recurrently affected this species during the last decade. Thus, knowledge of its genetic structure, population diversity, and connectivity is needed to accomplish suitable conservation plans. In order to obtain a better understanding of the population genetics of this species, 13 highly variable microsatellites markers were developed from a naturally bleached colony. The developed primers failed to amplify zooxanthella DNA, isolated from C. caespitosa, verifying that these markers were of the coral and not algal symbiont origin. The degree of polymorphism of these loci was tested on tissue samples from 28 colonies. The allele number for each loci ranged from 2 to 13 (mean N(a) = 5.4), with an average observed heterozygosity of 0.42 (H(e) = 0.43) and all loci were in Hardy-Weinberg equilibrium. These new markers should be useful in future conservation genetic studies and will help to improve the resolution of the individual identification within this coral species. Primers were also tested in Oculina patagonica, with successful amplifications of several loci.

Development of Microsatellite Markers in the Deep-Sea Cup Coral Desmophyllum dianthus by 454 Sequencing and Cross-Species Amplifications in Scleractinia Order

Microsatellite loci were isolated for the first time for the deep-sea coral Desmophyllum dianthus, using 454 GS-FLX Titanium pyrosequencing. We developed conditions for amplifying 24 markers in 10 multiplex reactions. Three to 16 alleles per locus were detected across 25 samples analyzed from Santa Maria di Leuca coral province (Mediterranean Sea). For the 24 polymorphic loci, observed and expected heterozygosities ranged from 0.211 to 0.880 and 0.383 to 0.910, respectively; 3 loci deviated from Hardy-Weinberg equilibrium, after null allele and sequential Holm-Bonferroni corrections. These newly isolated microsatellites are very useful genetic markers that provide data for future conservation strategies. Cross-amplification of these microsatellites, tested in 46 coral species, representing 40 genera, and 10 families of the phylum Cnidaria, produced informative allelic profiles for 1 to 24 loci. The utility of extending analyses to cross-species amplifications is also discussed.

Isolation and characterization of twelve polymorphic microsatellite loci for investigating an extreme case of microgeographical variation in an island bird (Zosterops borbonicus)

Twelve polymorphic microsatellite loci were characterized in order to investigate an extreme case of microgeographical variation in an island-dwelling passerine (Zosterops borbonicus). Variation was examined in two distinct natural populations of 27 individuals each. The loci displayed 5–20 alleles, with observed heterozygosities ranging between 0.33 and 0.93. All but one loci (Z16) conformed to Hardy–Weinberg equilibrium. None of the pairwise comparisons among loci showed significant linkage disequilibrium after sequential Bonferonni correction. Successful cross-species amplification in additional Zosterops species and other passerines suggests their broad applicability.

Development and characterization of 26 novel microsatellite loci for the trochid gastropod Gibbula divaricata (Linnaeus, 1758), using Illumina MiSeq next generation sequencing technology

In the present study we used the high-throughput sequencing technology Illumina MiSeq to develop 26 polymorphic microsatellite loci for the marine snail Gibbula divaricata. Four to 32 alleles were detected per locus across 30 samples analyzed. Observed and expected heterozygosities ranged from 0.130 to 0.933 and from 0.294 to 0.956, respectively. No significant linkage disequilibrium existed. Seven loci deviated from Hardy-Weinberg equilibrium that could not totally be explained by the presence of null alleles. Sympatric distribution with other species of the genus Gibbula, as G. rarilineata and G. varia, lead us to test the cross utility of the developed markers in these two species, which could be useful to test common biogeographic patterns or potential hybridization phenomena, since morphological intermediate specimens were found.

Development and characterization of microsatellite loci in the entocommensal Malacobdella arrokeana (Nemertea: Bdellonemertea), from Patagonia (Argentina) and cross-amplification in 34 nemertean species

Microsatellite loci (26 in total) were isolated for the first time for the entocommensal nemertean Malacobdella arrokeana, using 454 GS-FLX Titanium pyrosequencing. We developed conditions for amplifying these markers in 8 multiplex and 5 individual reactions. One to 14 alleles were detected per locus across 25 samples analyzed from San Matías Gulf, Patagonia (Argentina). For the 25 polymorphic loci, observed and expected heterozygosities ranged from 0.125 to 0.920 and 0.119 to 0.890, respectively; five loci deviated from Hardy–Weinberg equilibrium. Limited distribution and host specificity of M.arrokeana, which only inhabits Panopea abbreviata, have endangered this nemertean given the unregulated commercial exploitation of its host. These useful markers provide data for future conservation strategies. Cross-amplifications were also tested in 34 nemerteans species, representing the major lineages in this phylum. In total, 18 of the 26 loci (from one to 11 per species) gave clear allelic profiles.

Minimal barcode distance between two water mite species from Madeira Island: a cautionary tale

In this work, we compare morphological and molecular data in their ability to distinguish between species of water mites (Acari, Prostigmata, Hydrachnidia). We have focused on the two species of the genus Lebertia inhabiting the island of Madeira. While traditional morphological traits were initially sufficient to distinguish between these two species, the molecular data were more dependable on the kind of analysis carried out. Single arbitrary genetic distance (e.g. a K2P distance below 2%) may lead to the conclusion that the specimens under study belong to the same species. Analysing the same specimens with the coalescent model has proved the evolutionary independence of both Lebertia clades in Madeira. Furthermore, multi-rate Poisson Tree Process analysis confirmed both lineages as independent species. Our results agree with previous studies warning of the dangers of rigid species delimitation based on arbitrary molecular distances. In addition, the importance of different molecular data approaches for correct species delimitation in water mites is highlighted.

Predatory flying squids are detritivores during their early planktonic life

Cephalopods are primarily active predators throughout life. Flying squids (family Ommastrephidae) represents the most widely distributed and ecologically important family of cephalopods. While the diets of adult flying squids have been extensively studied, the first feeding diet of early paralarvae remains a mystery. The morphology of this ontogenetic stage notably differs from other cephalopod paralarvae, suggesting a different feeding strategy. Here, a combination of Laser Capture Microdissection (LCM) and DNA metabarcoding of wild-collected paralarvae gut contents for eukaryotic 18S v9 and prokaryotic 16S rRNA was applied, covering almost every life domain. The gut contents were mainly composed by fungus, plants, algae and animals of marine and terrestrial origin, as well as eukaryotic and prokaryotic microorganisms commonly found in fecal pellets and particulate organic matter. This assemblage of gut contents is consistent with a diet based on detritus. The ontogenetic shift of diet from detritivore suspension feeding to active predation represents a unique life strategy among cephalopods and allows ommastrephid squids to take advantage of an almost ubiquitous and accessible food resource during their early stages. LCM was successfully applied for the first time to tiny, wild-collected marine organisms, proving its utility in combination with DNA metabarcoding for dietary studies.

Carinina ochracea (Palaeonemertea: Tubulanidae) Reaches Its Southernmost Distribution: New Morphological and Molecular Data

New data for Carinina ochracea Sundberg et al., 2009 are provided for the Iberian Peninsula, establishing the southernmost limit of its known distribution. This species was previously known from only two localities: the type locality in Tjärnö (Sweden) and Pouldohan (Brittany, France). The material examined here was obtained during a faunal survey in the Villaviciosa Estuary (Asturias, northern Iberian Peninsula). The identity of the new specimen was confirmed both by DNA barcoding and anatomical examination. The molecular divergence of all available sequences of this species for four molecular markers, cytochrome c oxidase subunit I (COI), 16S, 18S and 28S rDNA, is discussed. For COI, four polymorphic sites were found, indicating: 1) a nuclear pseudogene; 2) heteroplasmy; or 3) gene duplication of a region of the mitochondrial genome. Two previously overlooked morphological characters were found: the presence of a colour ring and a postfixation staining band (pigmented band), which is histologically characterized. This species is the 12th palaeonemertean and the 75th nemertean reported from Iberian waters.