1,721,172 research outputs found
Population dynamics and life cycle of the introduced ascidian Microcosmus squamiger in the Mediterranean Sea
No full textMarine introductions are a serious threat for biodiversity, especially in seas where shipping is intensive. Microcosmus squamiger is a widespread marine invader that can alter native biota and it is therefore imperative to understand its biology and ecology. We studied the population dynamics and reproductive cycles of M. squamiger over a 2-year period, as well as its settlement and colonization patterns, in a north-western Mediterranean (NE Spain) locality where M. squamiger has been introduced. All biological parameters showed a strong seasonal pattern that peaked in summer with a major spawning episode at the end of summer. Size-frequency histograms indicated a 2-year cycle. Colonization experiments suggested that M. squamiger recruitment mortality is high and requires a well structured community. In addition, we monitored the abundance of the native predator Thais haemastoma, which showed a significant positive correlation with M. squamiger biomass, indicating its potential usefulness as a biological control
Spread of Microcosmus squamiger (Ascidiacea: Pyuridae) in the Mediterranean Sea and adjacent waters
No full textThe Mediterranean Sea is subject to an ever-increasing arrival of non-indigenous marine organisms. Microcosmus squamiger is a solitary ascidian that inhabits shallow rocky littoral habitats. It probably originated in Australia and it has shown great invasive potential in other parts of the world. In the Mediterranean, M. squamiger has only been reported at a few sites in Spain and Italy. However, the closely related species Microcosmus exasperatus has been reported in several areas of the western Mediterranean. As these species can be easily confused, we re-examined most of the material from previous studies and our personal collections. In addition, sampling was done at several sites along the western Mediterranean and Atlantic coasts. The results showed that the majority of the M. exasperatus reports correspond to M. squamiger, and that M. squamiger is common on the Atlantic shores. This suggests that M. squamiger has entered the Mediterranean through the Gibraltar Strait, while the restricted distribution in the eastern Mediterranean of M. exasperatus suggests that this species is probably a Lessepsian migrant. In the Mediterranean Sea, M. squamiger has the ability to occupy extensive areas of hard substrata and to outcompete native species. Further studies are necessary to assess what impacts this invasive species have on native communities
Isolation of polymorphic microsatellite loci for the marine invader Microcosmus squamiger (Ascidiacea)
No full textThe ascidian Microcosmus squamiger is native to Australia and has recently spread worldwide. It has become a pest in some littoral communities within its introduced range. An enriched genomic library of M. squamiger resulted in a total of eight polymorphic loci that were genotyped in 20 individuals from a population within its introduced range, and 20 individuals more from a native population. The mean number of alleles per locus was 5.33 and mean observed heterozygosity was 0.432. No significant linkage disequilibrium was found among loci pairs. Significant genetic differentiation was observed between populations
Phylogeography and the Description of Geographic Patterns in Invasion Genomics
Full text linkEste artículo contiene 6 páginas, 1 figura.Phylogeography is an integrative discipline that aims to understand the geographic ordination
of genotypes. In recent decades, phylogeographic approaches have been used to enhance our
understanding of both biogeography and landscape genetics across a variety of spatial and temporal
scales. By definition, species studied using these approaches need to meet certain assumptions
(e.g. mutation and drift need to be at equilibrium). However, artificially dispersed species (i.e.
non-indigenous, naturalised and invasive species) often do not comply with these assumptions.
Thus, the use of phylogeographic approaches to study these species may lead to erroneous
interpretations. Considering that self-denominated phylogeographic studies of invasive species
have proliferated in recent years and that genomic tools are now more accessible than ever
before, kick starting this debate is particularly timely. We argue herein that invasion scientists
must carefully use phylogeographic approaches when studying genomic data obtained from
the introduced range. In addition, the assumptions of these phylogeographic approaches need
to be explicitly considered when interpreting genomic patterns of invasive species. Finally,
we suggest abandoning the use of the term ‘phylogeography’ for describing geographically
contextualized genomic data from the introduced range to avoid both terminological and
methodological confusion.The ideas developed in this
opinion note were partly conceived during the development of
the project CTM2017-88080 (MCIU/AEI/FEDER/UE) from the
Spanish Government.Peer reviewe
FIGURE 9. Cnemidocarpa verrucosa, A in Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile
No full textFIGURE 9. Cnemidocarpa verrucosa, A, natural aspect; B, dissected body. Scale bar: A, B, 2 cm.Published as part of Turon, Xavier, Cañete, Juan I., Sellanes, Javier, Rocha, Rosana M. & López-Legentil, Susanna, 2016, Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile, pp. 151-180 in Zootaxa 4093 (2) on page 167, DOI: 10.11646/zootaxa.4093.2.1, http://zenodo.org/record/26766
Non-lethal effects of an invasive species in the marine environment: the importance of early life-history stages
No full textStudies examining the effects of invasive species have focussed traditionally on the direct/lethal effects of the invasive on the native community but there is a growing recognition that invasive species may also have non-lethal effects. In terrestrial systems, non-lethal effects of invasive species can disrupt early life-history phases (such as fertilisation, dispersal and subsequent establishment) of native species, but in the marine environment most studies focus on adult rather than early life-history stages. Here, we examine the potential for an introduced sessile marine invertebrate (Styela plicata) to exert both lethal and non-lethal effects on a native species (Microcosmus squamiger) across multiple early life-history stages. We determined whether sperm from the invasive species interfered with the fertilisation of eggs from the native species and found no effect. However, we did find strong effects of the invasive species on the post-fertilisation performance of the native species. The invasive species inhibited the settlement of native larvae and, in the field, the presence of the invasive species was associated with a ten-fold increase in the post-settlement mortality of the native species, as well as an initial reduction of growth in the native. Our results suggest that larvae of the native species avoid settling near the invasive species due to reduced post-settlement survival in its presence. Overall, we found that invasive species can have complex and pervasive effects (both lethal and non-lethal) across the early life-history stages of the native species, which are likely to result in its displacement and to facilitate further invasion
Mixed but not admixed: a spatial analysis of genetic variation of an invasive ascidian on natural and artificial substrates
No full textFollowing the introduction to a new area (pre-border dispersal), post-border processes determine the success in the establishment of non-indigenous species (NIS). However, little is known on how these post-border processes shape the genetic composition of NIS at regional scales. Here, we analyse genetic variation in introduced populations along impacted coastlines to infer demographic and kinship dynamics at the post-border stage. We used as a model system the ascidian species Microcosmus squamiger that has been introduced worldwide. This species can colonize and grow fast on man-made artificial structures, impacting activities such as mariculture. However, it can also establish itself on natural substrates, thus altering natural communities and becoming an ecological problem. We genotyped 302 individuals from eight populations established on natural and artificial substrates in the north-western Mediterranean Sea, using six microsatellite loci. We then compared the resulting genotypes with those found within the native range of the species. We found high levels of genetic diversity and allelic richness in all populations, with an overall deficit of heterozygotes. Autocorrelation analyses showed that there was no within-population genetic structure (at a scale of tens of metres); likewise, no significant differentiation in pairwise comparisons between populations (tens of kilometres apart) and no isolation-by-distance pattern was found. The results suggest that M. squamiger has a natural capacity for high dispersal from one patch of hard substrate to another and no differences whatsoever could be substantiated between natural and artificial substrates. Interestingly, two groups of genetically differentiated individuals were detected that were associated with the two ancestral source areas of the worldwide expansion of the species. Individual assignment tests showed the coexistence of individuals of these two clusters in all populations but with little interbreeding among them as the frequency of admixed individuals was only 15 %. The mechanism responsible for maintaining these genetic pools unmixed is unknown, but it does not appear to compromise post-border colonization of introduced populations
Phylogeography of the widespread marine invader Microcosmus squamiger (Ascidiacea) reveals high genetic diversity of introduced populations and non-independent colonizations
No full textThe spread of non-indigenous species into new marine habitats represents an increasing threat to global diversity. Genetic techniques provide basic understanding of the invasion processes. The ascidian Microcosmus squamiger is considered to be native to Australia, having been spread worldwide via transoceanic vessels. It has successfully invaded artificial and natural habitats where it has become a pest. We studied phylogeography and genetic structure of 12 M. squamiger populations, including samples from its native range (Australia) and introduced populations from the Indian, Pacific, and Atlantic oceans, as well as the Mediterranean Sea. We amplified 574 bp of the mitochondrial COI gene in 258 individuals and found a total of 52 haplotypes. A haplotype tree revealed two main groups of haplotypes. The relative frequency of each group of haplotypes, multidimensional scaling, and analysis of molecular variance showed important differences between the western Australia localities and the remaining ones (eastern Australia and introduced populations). Furthermore, we found that the colonization of the different areas by M. squamiger has not occurred independently, as many introduced populations shared some low frequency alleles. A nested clade analysis showed a global pattern of restricted gene flow with isolation by distance, although we found episodes of long-distance dispersal in some clades. A contiguous range expansion was detected between Australian populations. We conclude that M. squamiger is native to Australia and has most likely expanded its range of distribution sequentially through worldwide shipping, especially from the harbours of the more populated eastern Australia. In introduced populations, we found a high genetic diversity which suggests enhanced invasive potential. Consequently, there is a need to control this species, as it outcompetes local biota and is an economic threat
FIGURE 2. Distaplia colligans. A in Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile
No full textFIGURE 2. Distaplia colligans. A, image of a colony; B, zooid as seen from the left hand side; C, Thoracic region as seen from the right hand side; D, larva. Scale bars: A, 2 cm; B,C,D, 0.5 mm.Published as part of Turon, Xavier, Cañete, Juan I., Sellanes, Javier, Rocha, Rosana M. & López-Legentil, Susanna, 2016, Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile, pp. 151-180 in Zootaxa 4093 (2) on page 156, DOI: 10.11646/zootaxa.4093.2.1, http://zenodo.org/record/26766
FIGURE 15. Paramolgula gigantea. A in Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile
No full textFIGURE 15. Paramolgula gigantea. A, underwater image of an specimen from Porvenir Bay; B, dissected individual; C, same individual without branchial sac; D, close-up of the aperture of the left gonad (stained), showing one female (♀) and three male openings (short tubes around ♀); E, image of the branchial sac (stained). Scale bars: A, B, C, 2 cm, D, 2 mm, E, 0.2 mm.Published as part of Turon, Xavier, Cañete, Juan I., Sellanes, Javier, Rocha, Rosana M. & López-Legentil, Susanna, 2016, Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile, pp. 151-180 in Zootaxa 4093 (2) on page 177, DOI: 10.11646/zootaxa.4093.2.1, http://zenodo.org/record/26766
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