{"refrec":{"BRefID":290380,"RR":"<b>Goedknegt, M.A.</b> (2017). Pacific oysters and parasites: Species invasions and their impact on parasite-host interactions. PhD Thesis. VU University Amsterdam/NIOZ: Amsterdam. ISBN 978-90-5383-297-9. 271 pp. <a href=\"https://hdl.handle.net/1871/55400\" target=\"_blank\">https://hdl.handle.net/1871/55400</a>","BEntID":282420,"PublicFlag":1,"CheckedFlag":0,"wosflag":null,"vabbflag":null,"RefStringPartII":". PhD Thesis. VU University Amsterdam/NIOZ: Amsterdam. ISBN 978-90-5383-297-9. 271 pp. <a href=\"https://hdl.handle.net/1871/55400\" target=\"_blank\">https://hdl.handle.net/1871/55400</a>","DocTypID":5,"DocType":"Book/Monograph","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Goedknegt, M.A.","OrigTitleTranslFlag":0,"Authorstringtrunc":"Goedknegt, M.A.","Englishabstract":"Human-aided  introductions of  species affect natural  communities  and  ecosystems  worldwide. These  biological  invasions  can  be considered  to  be ‘experiments in nature’ to study general ecological and evolutionary  processes at large spatial and temporal scales.Studies  on biological invasions have mostly been focussing on competitive or predatory interactions between invasive  and resident species, and the resulting impacts on native communities. Much less known are the impacts  of  invasions  on parasitism, the  most  common consumer  strategy in  the  world.  In  this case, these ‘experiments in nature’ may involve the addition and loss of parasite and host species. Especially the loss of parasites in the process of an invasion has received increasing interest, as it has  been  hypothesized  that such  a loss of  parasites may  give invaders  a  potential  competitive  advantage over native species, contributing  to their invasion success (enemy  release  hypothesis). However,  recent developments  in  the fields of  parasite  ecology and invasion  biology suggest additional   ways   of   how   invasive   species   can   affect   parasite-host interactions   in   invaded ecosystems beyond an initial parasite release.Yet, the complexity of these effects as the result of a single species invasion has not been investigated so far.In this thesis, I addressed this knowledge gap and investigated them anifoldways in which a single invader  can affect  parasite-host  interactions in  invaded  ecosystems in one of  the  most prominent  marine  invaders  in  the  world:  the Pacific  oyster Crassostrea  gigas.This  invasive  species is now globally distributed after  initial  introductions for  aquaculture  purposes from  its native  range  (East  Asia)to  the  Pacific  coast  of  North  America,  followed  by  secondary human-aided introductions  from this area to Europe and other continents. In the European Wadden Sea, the main study area of this thesis, the Pacific oyster became invasive via larval spread from oyster culture  plots  in  the  Dutch  Delta  and in the  northern German  Wadden  Sea. Like  in  many  other European  coastal  areas, the  Pacific  oyster now  occurs  in  dense  populations  across  the entire  Wadden Sea and has transformed native blue mussel Mytilus edulisbeds into complex oyster reef structures.  In the Wadden  Sea ecosystem,the Pacific oyster is associated with five  invasive  and native  macroparasite  species, providing  a suitable model  system to study the establishment  of new and the alteration of existing parasite-host interactions  as a result of species invasions.The overall objective of my thesis was to disentangle the various roles of invasive species in   affecting   parasite-host   interactions   in   invaded   ecosystems  and  to identify   the resulting ecological  impacts.I specifically  aimed to I)provide  a  conceptual  framework  for  the  study  of parasite-host  interactions  as  a  result  of  marine  invasions(Chapter  2), II)identify  the multipleroles of the invasive Pacific oyster (Crassostrea  gigas) in parasite-host interactions in the Wadden Sea ecosystem(Chapters 3-6), and III)determine the resulting ecological implications of changes in parasite-host  interactions  mediated  by Pacific  oysters(Chapters  7-9). The thesis ends with  a general  discussion in  which I place  the  results  in  a  broader  ecosystem  context  and  provide  suggestions for future research (Chapter 10). Part I -Marine invasions and parasites: a review In Chapter  2, I provided a  conceptual  framework  of  six  mechanisms  by  which  marine  invasive  species   can   affect   parasite-host   interactions   in   invaded   ecosystems.   To   do   so,   I gave a comprehensive  overview  of  what  is  currently   known  about  the  roles  of  invasive  species  in parasite-host  interactions by reviewing conceptual  developments  and empirical  evidence  from the literature. Subsequently, I discussed he ecological and evolutionary  implications for each of these mechanisms for the parasite and host species involved.The six mechanisms identified  and discussed are the following: Summary 2491. Parasite   release  or  reduction:Invasive  species  can  leave  all  or  some  of  their  parasites behind  in the  native range, leading  to potential competitive  advantages  of  invaders  over native species (enemy release hypothesis). 2. Parasite  spillback:  Invasive  species  can  act  as  new  competent  hosts  for  native  parasite  species,   potentially   amplifying   the   native   parasite   population,   leading   to   increased infection levels in native host species.3.Introduction of free-living stages of parasites: Invasive species can be parasites themselves, which  are  introduced   as  free-living  stages  (mostly  microparasites)  in  the  introduced range, potentially infecting  native host species. 4. Parasite  co-introduction  with  host: Invasive  parasite scan  be  co-introduced  with  their invasive host to the introduced range. 5. Co-introductions  of  parasites   and  spillover  to  native  hosts:  Invasive  parasites  can  be  co-introduced with their invasive host to the introduced range and subsequently spill over to native host species.6.Interference  with parasite  transmission:Invasive species can be non-competent  hosts and interfere  with the transmission of native parasites. Part II - Pacific oysters and parasite-host interactions In Chapter  3, I investigated the effects  of the invasion of Pacific  oysters (Crassostrea  gigas)  on the distribution  and  abundance  of  parasites  in  native  mussel  (Mytilus  edulis)  and  invasive Pacific oyster  hosts  across  the  entire  Wadden  Sea. In  this  study,  I used  a hierarchical  field sampling design  with  three  spatial  scales  to  determine  the  spatial  distribution  of  parasites  in  both  host species.  Furthermore, I  identified the  most  important  environmental  and  biological  drivers  of infection  levels using  mixed  models, demonstrating  that spatial  infection  patterns  and  their drivers are host and parasite specific. In Chapter  4, I assessed the reliability of the morphological identification  of two invasive  parasitic  copepods, Mytilicola  orientalis and Mytilicola  intestinalis, which  play a potential  role in three of the mechanisms identified  in Chapter  2. These two parasite species have originally been described from different  continents, but now co-occur in the same host species (blue mussels M. edulis)  and at similar locations (the  Wadden Sea and Dutch  Delta), challenging  the reliability  of their identification. By using a multitude  of morphological variables and multivariate statistics, I demonstrated that  the  invasion  of  both Mytilicola species in  the  Dutch  Delta  and  Wadden  Sea represents a case of ‘cryptic by invasion’, i.e. the two species are not reliably distinguishable by morphology in the invaded range, rendering  them cryptic species (a phenomenon probably more  common in species invasions than currently  known.In the end of this chapter, I recommended guidelines for the identification of both parasite species when they co-occur in similar hosts and at similar locations. In Chapter  5, I used the recommendations provided in Chapter 4 to identify the role of the Pacific   oyster   in  the  co-introduction   and  spillover   of M.  orientalis and  the   spillback  of M. intestinalisto  native  host  species,  which  are two of  the mechanisms which  were  identified  in Chapter  2. To  this  end,  I  used a  substantial  field  sampling  of  11  different invasive  and  native mollusc species across the Dutch Delta and the Wadden Sea, and found evidence for spillover of Summary 250M.  orientalisto  three  native  bivalve  species,  but  no  evidence  for  spillback  of M.  intestinalisto native mussels via nvasive Pacific oyster hosts. In Chapter  6, I introduced a new  mechanism of  how invasive ecosystem engineers, such as Pacific oysters, can affect parasite-host interactions. With a field experiment performed at both ends of the Wadden Sea, I demonstrated that invasive Pacific  oysters can initiate trait-mediate d indirect   effects   on  parasite-host   interactions  via  the  habitat  structure   and  complexity  they provide.  Native  blue  mussels  use  the  complex  structure  created  by  the  oysters  as  refuge  from predators by migrating  to the bottom of  the oyster matrix and this behavioural  change induced by  the  oysters  in presence  of  predators  results  in  mussels  at the  bottom  and  top  of  the  matrix experiencing  significantly  different parasite infection  levels. This study is the  first  to  present evidence  for  an indirect  modification  in  parasite-host  interactions  as  a  result  of  the  physical structure  of an invasive ecosystem engineer.Part III -Ecological  implications In Chapter   7,  I  focused on  the  newly  established  parasite-host   relationship  of  the  invasive  copepod Mytilicola  orientalis and  the  native  blue  mussel Mytilus  edulis. By  breeding  parasite  larvae in the laboratory and executing controlled infections, the effects of the invasive parasite on its new blue  mussel host were experimentally  investigated. While the  condition  of the  mussels was significantly  reduced,  mussel clearance  rates and growth  were not affected  by the parasite.  With this study, I demonstrated that controlled experimental infections with M. orientalis can be used to study the effects of the parasite onnative and invasive host species.In Chapter  8, I investigated the mechanism  behind  the reduced  condition of native blue mussels as a result of M. orientalis infections (Chapter 7). I used stable isotope analyses to identify the  trophic  relationship  of M.  orientalis and  its  new  native  mussel host.  The measured trophic enrichment  of the parasite compared to its host species, indicated that the parasite is feeding on host tissue. Furthermore, with isotope mixing models I was able to show that mussel food sources (phytoplankton  and microphytobenthos)  could also contribute  to the parasite’s diet,  indicating that  the invasive M. orientalis has probably  a parasitic  as well as a commensalistic  relationship with its new native mussel host. Chapter   9 explored whether  the  trophic  enrichment  found  in  Chapter  8  is  a  general pattern  in  parasite-host  relationships. Based  on  a large  data  set compiled from  the  published literature  on  stable  isotope measurements  across  many  parasite  and  host  taxa, a phylogenetic comparative analysis found no general pattern  in trophic enrichment or depletion of parasites in nitrogenor carbon  isotopes compared  to  their host species.  This result  suggests that  parasite-host interactions in general may not fit well into the conservative stable isotope framework  with standardized trophic fractionation factors and calls for developing an appropriate framework  for parasitic trophic interactions. General discussion In Chapter  10, I presented  an overview  of the seven possible ways in which invasive species can affect  parasite-host  interactions  in  invaded  ecosystems that  I  identified  in  Chapters  2  and  6. Following  this, I showed that  all  seven  mechanisms  also play  a  role in the  invasion  of Pacific oysters and I discussed he results of my thesis in this respect. In addition, I provided a literature  review for  the mechanism  of parasite  release, indicating  that  at least five parasite  species were  lost during  the course of the invasion which may have facilitated the initial  spread of the Pacific oyster. Literature  sources were also used to include microparasite species (e.g. bacteria, viruses  Summary 251 and  protozoans) into the summary  of  the seven  mechanisms  for Pacific  oysters. Overall, this summary  shows  that  the introduction  of  the  Pacific  oyster to the  Wadden  Sea  (and elsewhere  such as the Dutch Delta) has resulted in complex changes in the parasite-host interaction web in the invaded ecosystem, involving both invasive  and native host and parasite species. Hence,  the seven  mechanisms discussed above can  occur  simultaneously  during the  invasion  of a  single species. However, the large-scale field  study I  conducted (Chapter  3) suggests that the parasite-host interaction   webs which  result   from   these   complex  interactions will  differ   across   the ecosystem depending  on local environments, as strong  spatial heterogeneity  in the distribution and abundance of parasites infecting  mussel and oyster hosts were observed across the Wadden Sea. Local environments obviously influence  local parasite-host  webs, resulting  in a diversity  of different  local webs across an ecosystem. These local interaction  webs can  differ  in the general species (parasites and host) composition and interaction  architecture, but also in the strength  of specific interactions between parasites and host species. This variation  in  parasite-host  interaction  webs  across the  invaded  ecosystem  will also result  in  different  impacts  on  host species  and  local  communities  across  the  ecosystem.  This compromises a general assessment of ecological and evolutionary impacts at the ecosystem scale. However, it is possible to assess the impact on smaller scales based on the condition that the local presence   and   abundance   of   parasite   and   host   species   is   known. Regarding   local   impact assessments in the Wadden Sea, parasite-host interactions involving  macroparasites will mostly impact native host species (in particular blue mussels M. edulis), while interactions  including the more virulent microparasites will mostly affect invasive Pacific oysters themselves.While  this  thesis  contributed  to  efforts  to  disentangle  the complex effects  of  marine invasive species on parasite-host interactions in invaded communities,there are still many open questions for  future  research. In the  studies  presented  in  this thesis, I focussed  particularly  on the mechanisms which link invaders with native species via parasite-host interactions. However,  interaction webs including these  parasite-host interactions are still simplified  versions of more  realistic  interaction  webs, as other  species interactions  involving  parasites  and their  hosts also exist such   as   parasite-parasite    interactions   and    parasite-mediated    indirect    interactions.  Furthermore, all these direct and indirect parasite-host interactions between invasive and native  species may affect  the  structure  and  dynamics of  food webs  via  the introduction  of  new  nodes and links. In conclusion, the work presented  in this thesis demonstrates  that only a single invasive  species,   exemplified   by   the   Pacific   oyster Crassostrea    gigas,   can   be   responsible   for   the establishment of various new and the modification of many existing parasite-host interactions  in invaded  ecosystems. Considering  the multitude  of  alien species  which have  been introduced  to the  Wadden  Sea  alone (at  least  49  species),  the  number  of  biotic  interactions  that  have  been added and  altered  since the introduction of each of these species must  be enormous, with  each type   of   interaction    resulting   in   ecological   and   evolutionary   impacts   for   native   marine communities. To unravel the complexity of these changes and the resulting impacts is a daunting task, but efforts  in this direction  will give significant  insights into the manifold roles of parasites  in marine invasions, their effects on species interaction networks and into the general functioning of marine ecosystems under an increasing pressure of species invasions.","AbstractOtherLang":null,"BibLvlCode":"M","StandardTitle":"Pacific oysters and parasites: Species invasions and their impact on parasite-host interactions","OrigTitleLangCode":"en","OrigTitleLangCodeExtended":"eng","OrigTitleLangID":15,"DateLastModified":{"date":"2024-12-10 01:33:17.368041","timezone_type":1,"timezone":"+01:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":null,"MonPub":2017,"DateUpdate":"2018-03-05","DateCreate":"2017-10-30","SecASFANote":null,"ConfID":null,"PeerRev":0,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":1,"Handle":"1871/55400"},"refs":null,"anarec":null,"monrec":{"MonID":290380,"ISBN":"978-90-5383-297-9","PubliDate":2017,"IssueDate":null,"Volume":null,"Issue":null,"Pagination":"271","Place":"Amsterdam","Edition":null,"BRefXtra":null,"BRefXtraRR":null,"SerID":null,"SerRR":null,"Ser2BRefID":null,"Ser2RR":null,"StandardTitleSer":null,"ISSN":null,"AbbrevSer":null,"Degree":"PhD","ThesisID":290380,"InsID":null,"Acronym":null,"FullStandardName":null,"ToPubliDate":null,"SerNotes":null,"eISBN":null,"Pages":271},"serrec":null,"relations":null,"relationsRev":null,"addrec":null,"othpubs":null,"ownerships":null,"authors":[{"AutName":"Goedknegt","Firstname":"M. 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