Volume 12, Issue 2 (2017)
published June 2017
Contents | |
Research articles |
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Peter E. Robins, Andrei Tita, Jonathan W. King and Stuart R. Jenkins
Predicting the dispersal of wild Pacific oysters Crassostrea gigas (Thunberg, 1793) from an existing frontier population – a numerical study
(pp 117–131)
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Non-native populations of Pacific oysters Crassostrea gigas (Thunberg 1793) are established around the United Kingdom (UK),
with two genetically different stocks originating from separate introductions to the UK and France. In this study, we use a coupled
biophysical model to simulate Pacific oyster larval transport, in order to investigate the dispersal of the species from a known
population near their northern limit on the west coast of the UK (in the Milford Haven Estuary). The model included a pelagic phase,
simulating different swimming behaviours, and a settlement phase based on a hydrospatial substrate map. Following successful settlement
elsewhere, subsequent releases simulated potential population spread over successive generations. Our results suggest that, should
there be sufficiently warm sea temperatures to allow reproduction, dispersal away from Milford Haven Estuary would most be southeast
ward towards the Bristol Channel; but dispersal north and west to Ireland is also possible, depending heavily on pelagic swimming behaviour.
Seasonal modifications to circulation were less influential. Our study increases understanding of factors that contribute to oyster population
spread, and suggests methods for improved management through numerical predictions. |
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Paula Moura, Lucía L. Garaulet, Paulo Vasconcelos, Paula Chainho, José Lino Costa and Miguel B. Gaspar
Age and growth of a highly successful invasive species: the Manila clam Ruditapes philippinarum (Adams & Reeve, 1850) in the Tagus Estuary (Portugal)
(pp 133–146)
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The Manila clam Ruditapes philippinarum (Adams & Reeve, 1850) was introduced in several regions worldwide where it is permanently established.
In Portuguese waters, the colonisation of the Tagus Estuary by this invasive species coincided with a significant decrease in abundance of the native
Ruditapes decussatus (Linnaeus, 1758). This study aimed to estimate the age and growth of the Manila clam, to compare the growth performance
between R. philippinarum and R. decussatus in several locations worldwide, and to ascertain whether the Manila clam’s growth patterns
contributed to the extensive distribution of this invasive bivalve in the Tagus Estuary. The growth of R. philippinarum in the Tagus Estuary
was described through the von Bertalanffy equation SLt=65.2[1−e-0.34(t+0.93)], corresponding to a phi-prime index (φ’) of 3.160 and an overall growth
performance of 4.974. This growth performance is the second highest recorded for R. philippinarum worldwide and was much higher than that of
R. decussatus from Portugal. This study confirmed that the Tagus Estuary presents near-ideal environmental conditions for growth of the Manila clam.
R. philippinarum displayed clearly invasive behaviour, spreading widely and growing faster than the native R. decussatus, which certainly
contributed to the decline of its populations in the Tagus Estuary. |
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Ratha Sor, Pieter Boets, Sovan Lek and Peter L.M. Goethals
Spatio-temporal co-occurrence of alien and native molluscs: a modelling approach using physical-chemical predictors
(pp 147–158)
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The invasion of alien species can have serious economic and ecological impacts. Ecologically, invasions often lead to an increased rate
of native species replacement and decreased biodiversity. A critical step in the dominance of alien species is their successful
co-occurrence with native species. In this study, we assessed the occurrence of alien molluscs and their co-occurrence with native
molluscs and identified the determining physical-chemical variables. We expected that a combination of some key variables of water
quality could provide suitable conditions promoting alien molluscs to occur and to co-occur with native molluscs. The analyses were
based on 20-year data, collected from river systems across Flanders (Belgium). Classification Trees (CTs) were used to perform
the analyses and to develop the predictive models. Based on CT models, the co-occurrence of alien and native molluscs could be reliably
predicted based on physical-chemical variables. However, there was insufficient data to determine the environmental conditions in which
alien taxa dominate. From the past to the present, spatial co-occurrence significantly increased. Sinuosity, ammonium and nitrate
concentrations, chemical oxygen demand, pH and conductivity were the key determining variables. Our findings suggest that the co-occurrence
of alien and native molluscs mainly occurs in straight rivers with good chemical water quality. These results provide insights into
the ecology and behaviour of alien species which could support management practices and priority setting for conservation planning
in surface waters of Flanders and Europe. |
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Ian C. Duggan and Richard J. Payne
Revisiting Elton’s copepods: lake construction has altered the distribution and composition of calanoid copepods in the British Isles
(pp 159–166)
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It is now widely accepted that the construction of new lakes, ponds and reservoirs facilitates the invasion of non-indigenous aquatic species,
due largely to low biotic resistance from native communities. The role played by constructed waters appears to be a particularly frequent feature
of zooplankton invasions. Charles Elton, in his classic 1927 book “Animal Ecology”, noted that the estuarine calanoid copepod Eurytemora velox
had invaded constructed inland waters in Britain and highlighted the lack of a key species, Eudiaptomus gracilis, in allowing its establishment.
At the time, Elton’s observations were dismissed and his findings largely consigned to obscurity. Using occurrence records gathered since this time
and current knowledge of calanoid copepod ecology and invasion biology, we re-examined the distributions of three species of freshwater calanoid
copepods in the British Isles to: 1) determine the legacy of lake and pond construction on their distributions, and 2) reassess the conclusions
made by Elton in light of this knowledge. The lack of natural lakes in the south and east of England, and the subsequent widespread development
of new lakes and ponds, has altered calanoid copepod distributions. The common E. gracilis occurs frequently in the north and west
of the British Isles in natural lakes, and is found in the south and east in constructed waters. The estuarine E. velox was found only
in 3 natural freshwater sites, all in close proximity to the coast, but has been recorded in 23 constructed sites, many of these well inland.
Elton noted a general lack of co-existence between E. velox and E. gracilis, with the relatively slow establishment rates
of E. gracilis thought key in allowing the estuarine species to invade. However, subsequent collections suggest long-term co-occurrence
of these species at some sites. We suggest that E. velox has now successfully invaded freshwaters in the British Isles.
Eudiaptomus vulgaris is not known from natural lakes, but has been recorded in several constructed waters, and appears to have invaded
Britain facilitated by lake construction. Current knowledge supports Elton’s contention that constructed waters are more readily invaded than
natural waters, and that biotic resistance due to the presence of key species is important. While some specific criticisms of Elton’s ideas
were valid, we argue that Elton’s concepts regarding constructed waters and invasions were in many ways correct and prescient of current understanding. |
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Suzanne N. Branford, Ian C. Duggan, Ian D. Hogg and Gerd-Oltmann Brandorff
Mitochondrial DNA indicates different North American east coast origins for New Zealand and German invasions of Skistodiaptomus pallidus (Copepoda: Calanoida)
(pp 167–175)
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The freshwater calanoid copepod Skistodiaptomus pallidus (Herrick, 1879), native to the Mississippi basin of North America,
has recently established non-indigenous populations in New Zealand, Germany and Mexico. We used the mitochondrial cytochrome c
oxidase subunit I (COI) gene to more precisely identify the origins of S. pallidus populations within New Zealand and Germany.
The S. pallidus COI sequences suggested that both New Zealand and German populations were most similar to those from the most
easterly regions of the USA (e.g., New York, Virginia and Georgia). However, several haplotypes were found to be divergent between
the New Zealand and German populations, indicating the exact sources of the introductions were likely different for each country.
German sequences possessed two of the major haplotypes known from the east coast of USA, while New Zealand had one, indicating
a shipping related vector of introduction with greater propagule supplies to Germany is plausible. Although both German and
New Zealand populations contained haplotypes identical to common east coast North American sequence records, both non-indigenous
populations had haplotypes not yet recorded in the USA. Further sampling of the native range will be required to determine
the exact origin of the non-indigenous S. pallidus populations and may also help to identify more precisely the vectors
and pathways of the translocations. |
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Rosetta C. Blackman, Drew Constable, Christoph Hahn, Andrew M. Sheard, Jessica Durkota, Bernd Hänfling and Lori Lawson Handley
Detection of a new non-native freshwater species by DNA metabarcoding of environmental samples – first record of Gammarus fossarum in the UK
(pp 177–189)
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We report the discovery of a non-native gammarid, Gammarus fossarum (Koch, 1836) (Crustacea, Amphipoda), in UK rivers.
Gammarus fossarum is a common freshwater gammarid in many parts of mainland Europe, but was previously considered absent from the UK.
Gammarus fossarum was detected in a number of UK rivers following DNA metabarcoding of a mini-barcode region of the COI gene
in macroinvertebrate kick samples, and environmental DNA (eDNA) from water and sediment samples. Subsequent morphological analysis
and standard DNA barcoding showed that the species could be reliably identified and separated from Gammarus pulex (Linnaeus, 1758),
the most dominant and widespread native freshwater gammarid in the UK. Our data demonstrate extensive geographical coverage of G. fossarum
in the UK, spanning distant river catchments. At present there is no data to confirm the likely origin of G. fossarum’s introduction.
Subsequent re-examination of historic archive material shows the species to have been present in the UK since at least 1964. This study is
among the first to demonstrate the potential of eDNA metabarcoding for detection of new non-native species. |
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Katariina Riipinen, Salla Mikkola, Milla K. Ahola, Milla M. Aalto, Alisa Olkinuora and Outi Vesakoski
Habitat selection of the mud crab Rhithropanopeus harrisii in its newly invaded range
(pp 191–200)
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Information on the habitat selection by non-indigenous species is crucial for understanding their effects on the communities
to which they are introduced, since the effects are often focused on the invaded habitats. The North American mud crab
Rhithropanopeus harrisii is a new invader in the northern Baltic Sea, on the coasts of Finland and Estonia.
In the Finnish Archipelago Sea, it has been found in two very distinct habitats: reed belts of Phragmites australis
and algal zones with Fucus vesiculosus as the main habitat-forming species. In previous studies in the Baltic Sea, R. harrisii
has preferred F. vesiculosus and has locally driven a shift in the structure of F. vesiculosus-associated invertebrate communities.
Here, we disentangled whether habitat choice was determined by habitat structure or the availability of food. First, we conducted a habitat
selection experiment with P. australis and F. vesiculosus habitats and varying food availability, and found that R. harrisii
preferred F. vesiculosus, with food having no effect on the habitat choice. Second, we studied if the preference for F. vesiculosus
was due to the alga itself or the rocks it grows on. We found that R. harrisii preferred the shelter of the rock habitat, indicating that
R. harrisii choose their habitat based on habitat structure rather than food availability in the habitat. However, the preference for
sheltered rocky bottom habitats also exposes the associated F. vesiculosus communities to the impacts of R. harrisii through predation. |
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M. Anouk Goedknegt, Jarco Havermans, Andreas M. Waser, Pieternella C. Luttikhuizen, Estefania Velilla, Kees (C. J.) Camphuysen, Jaap van der Meer and David W. Thieltges
Cross-species comparison of parasite richness, prevalence, and intensity in a native compared to two invasive brachyuran crabs
(pp 201–212)
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An introduced species’ invasion success may be facilitated by the release of natural enemies, like parasites, which may provide an invader
with a competitive advantage over native species (enemy release hypothesis). Lower parasite infection levels in introduced versus native
populations have been well documented. However, any potential competitive advantage will depend on whether native competitors exhibit higher
parasite loads than introduced hosts and whether native hosts suffer more (e.g., reduced reproduction or growth) from parasite infections
than introduced hosts. In this study, we compared macroparasite richness, prevalence, and intensity in sympatric populations of one native
and two introduced brachyuran crab hosts in the centre of their European range. While the native green crab Carcinus maenas
(Linnaeus, 1758) hosted three parasite groups (acanthocephalans, microphallid trematodes, rhizocephalans), the two invasive crab species
Hemigrapsus sanguineus (De Haan, 1835) and H. takanoi Asakura and Watanabe, 2005 were only infected with acanthocephalans.
All acanthocephalans were molecularly identified (COI) as the native Profilicollis botulus (Van Cleave, 1916). Prevalence and
intensities of P. botulus were generally lower in the introduced than in the native crabs. Metacercariae of microphallid trematodes
were only found in the native C. maenas, with mean infection levels of 100–300 metacercariae per host, depending on geographical location.
Likewise, the castrating rhizocephalan barnacle Sacculina carcini Thompson, 1836 was only found in C. maenas at a few locations with
low prevalences (< 3%). This first study on infection levels in invasive Hemigrapsus species in Europe indicates that these invasive crabs
indeed experience lower infection levels than their native competitor C. maenas. Future experiments are needed to investigate whether
this difference in infection levels leads to a competitive advantage for the invasive crab species. |
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Danielle Asson, John W. Chapman and Brett R. Dumbauld
No evidence that the introduced parasite Orthione griffenis Markham, 2004 causes sex change or differential mortality in the native mud shrimp, Upogebia pugettensis (Dana, 1852)
(pp 213–224)
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Dramatic, rapid, population declines of the native North American burrowing shrimp Upogebia pugettensis (Dana, 1852) are associated
with intense infestations by the introduced Asian bopyrid isopod parasite, Orthione griffenis Markham, 2004. However, expected host
weight losses with increasing parasite weights do not occur, even among apparently castrated females. The prevailing assumption that energetic
losses cause host castration have thus remained open to question, and the mechanism(s) resulting in castration and consequent population declines
of U. pugettensis have remained unclear. Proposed alternative explanations for these declines, which have been based on a dramatically
greater prevalence of O. griffenis among U. pugettensis females, include parasite induced sex change, increased male mortality,
and differential tidal exposure of sexes to settling O. griffenis larvae. We examined 508 O. griffenis infestations from 2,014 shrimp
collected from 26 stations in 5 Oregon estuaries to test these alternative hypotheses. We expected greater infestation frequencies among females
than among males and a close association of O. griffenis infestations with intersex shrimp in the overall population if feminization occurs.
We also expected covariation in sex ratio with tide exposure if O. griffenis settlement is sex linked. Instead, we found an overall 1:1.07 sex
ratio, a lack of association of intersex U. pugettensis with O. griffenis infestations, and an unchanging sex ratio with tidal exposure,
precluding parasite induced sex change, male mortality, or tidal immersion effects on infestations. The most likely mechanism driving U. pugettensis
declines thus remains castration due to host energetic losses. This energetic interaction is likely to be resolved quantitatively through controlled
experiments and increasingly detailed field surveys over time. |
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Melissa Gibbs, Patrick Watson, Kelsey Johnson-Sapp and Craig Lind
Reproduction revisited – a decade of changes in the reproductive strategies of an invasive catfish, Pterygoplichthys disjunctivus (Weber, 1991), in Volusia Blue Spring, Florida
(pp 225–239)
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The reproductive patterns of invasive species may undergo changes in response to the pressures of a novel environment. We tracked
the reproductive strategies of Pterygoplichthys disjunctivus collected in Volusia Blue Spring, adjoining the St. Johns River,
over a 10 year period from 2005 through 2014. After analyzing various measures of fecundity and reproductive seasonality, we found that
during that time period, P. disjunctivus reduced investment in individual offspring, while increasing overall fecundity and GSI.
In addition, its reproductive season had expanded, and seasonal differences in nearly all measures became significantly smaller.
This species does not seem to fit into any one reproductive strategy, nor has it moved in a consistent direction within the Winemiller-Rose
reproductive strategy scheme. We suggest that despite the value of such schemes in predicting responses to environmental parameters,
they may not be able to adequately describe the strategies of invasive species that have access to ecosystems that are more benign
than their native habitats. |
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Hui Wei, Gordon H. Copp, Lorenzo Vilizzi, Fei Liu, Dangen Gu, Du Luo, Meng Xu, Xidong Mu and Yinchang Hu
The distribution, establishment and life-history traits of non-native sailfin catfishes Pterygoplichthys spp. in the Guangdong Province of China
(pp 241–249)
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In China, the introduction of South American sailfin catfishes of the genus Pterygoplichthys are a concern due to the potential
risks they pose to native species and ecosystems. The present study reports on the distribution, establishment and maturity of
a Pterygoplichthys spp. hybrid swarm in Guangdong Province, China. Distribution data demonstrated that Pterygoplichthys spp.
were widespread in Guangdong Province, whereas only a few records were found in other parts of the country. The presence of mature
Pterygoplichthys spp. females indicated established self-sustaining populations in most drainages in the study region. While variation
in size at maturity and condition was observed among populations established in different drainages, Pterygoplichthys spp. in Guangdong
Province appeared to mature at a smaller size than in other non-native ranges. National-level legislation with which to prevent and/or mitigate
the release of other non-native fishes into the wild is recommended. |
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Annika W. Walters, Elizabeth G. Mandeville, W. Carl Saunders, Paul C. Gerrity, Joseph A. Skorupski, Zack E. Underwood and Eric I. Gardunio
Comparison of burbot populations across adjacent native and introduced ranges
(pp 251–262)
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Introduced species are a threat to biodiversity. Burbot, Lota lota, a fish native to the Wind River Drainage, Wyoming and a species
of conservation concern, have been introduced into the nearby Green River Drainage, Wyoming, where they are having negative effects on native
fish species. We compared these native and introduced burbot populations to evaluate potential mechanisms that could be leading to introduction
success. We examined genetic ancestry, physical habitat characteristics, community composition, and burbot abundance, relative weight,
and size structure between the native and introduced range to elucidate potential differences. The origin of introduced burbot in Flaming Gorge
Reservoir is most likely Boysen Reservoir and several nearby river populations in the native Wind River Drainage. Burbot populations did not
show consistent differences in abundance, size structure, and relative weight between drainages, though Fontenelle Reservoir, in the introduced
drainage, had the largest burbot. There were also limited environmental and community composition differences, though reservoirs in the introduced
drainage had lower species richness and a higher percentage of non-native fish species than the reservoir in the native drainage. Burbot
introduction in the Green River Drainage is likely an example of reservoir construction creating habitat with suitable environmental
conditions to allow a southwards range expansion of this cold-water species. An understanding of the factors driving introduction success
can allow better management of species, both in their introduced and native range. |
Letter to the Editor |
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Irene Adrian-Kalchhauser, Anouk N’Guyen, Philipp E. Hirsch and Patricia Burkhardt-Holm
The invasive round goby may attach its eggs to ships or boats – but there is no evidence (pp 263–267)
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