Transcript Biological invasions – an introduction

Parasitism
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Relationship between two organisms, where the
parasite benefits at the expense of the host (ant.
mutualism)
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50% of all living species are parasites
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Every organism is susceptible to parasite infection
once in its lifetime
Microparasites
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Very small, often intracelluar, have short
generation times, high rates of reproduction
within the host, tendency to induce immunity.
Typical infections are of short duration in
relation to the normal life-span of the host.
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Bacteria, viruses, protozoa, fungi
Borrelia burgdorferi s.l.
Trypanosoma sp.
HIV
Staphylococcus aureus
Candida albicans
Macroparasites
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Much larger than microparasites with much
longer generation times. Reproduction occurs
but reproductive products are shed. Immune
response is usually density dependent and of
short duration. Such infections are persistent
with hosts often being continuously
reinfected.
Ectoparasites
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On the outside of the host  feather, skin,
hair, gills (permanent, temporarily)
No complete parasite existence (oxygen from
outside the host)
Ticks, fleas, lice, mites, mosquitoes, bugs
Trombidium
holosericum
Aedes albopictos
Endoparasites
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In the inside of the host
Intracellular (microparasites)
Intercellular (helminths)
Ascaris
lumbricoides
Wucheria
bancrofti
Opisthorchis viverrini
Ancliostoma
canium
Effect of parasites on their hosts:
morbidity and mortality
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Microparasites
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Acute infections over a short term, can have a
major influence on host mortality
Macroparasites
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More commonly chronic infections, cause less
mortality but more morbidity (i.e. pathogenicity
leading to reduced fitness)
Mortality in intermediate hosts
Biological invasions – an introduction
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Closely connected to
human travel and trade
(increased by 50% since
1990)
Biggest threat to
worldwide biodiversity
besides habitat loss and
fragmentation
Cause for 40% of historic
extinctions
Special danger to island
ecosystems
Clavera & García-Berthou 2005
Biological invasions – an introduction
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Introduced species:
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nonindigenous to a given area, transported by human
activity
usually localized distribution, possibly rare
can include garden and farm animals
Invasive species:
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non-indigenous species (NIS) that can maintain an
established population
causes economic or ecological harm or is likely to do
so in the future
Biological invasions – an introduction
Typical introduction routes:
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Intentional introductions:
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Domestic, farming or hunting animals
Farm or ornamental plants
Biological control experiments
Unintentional introductions:
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Transport of plant seeds, small insects and other
invertebrates with other goods
Marine organisms via ballast water, fouling
Pathogens
Biological invasions – an introduction
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percentage of species
100 of the worst invaders, selected by the Invasive Species
Specialist Group (ISSG) of the IUCN:
Lowe et al. 2004
Ecological consequences – Lake
Victoria
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Nile perch (Lates niloticus)
introduction 1954
Massive spread in
1980s
Extinction of >200
endemic fish species
(mainly cichlids)
Nile perch
Endemic cichlids
Ecological consequences – Lake
Victoria
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Altered fish industry:
smoking instead of
sun drying
Deforestation, soil
erosion,
desertification
Increased nutrient levels
promoted water hyazinth
(Eichhornia crassipes) invasion
Ecological consequences – Hawaii
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Avian malaria (Plasmodium
relictum) introduced with pet
birds
But: vector necessary for
spread
1826: introduction of the
southern house mosquito
Plasmodium
nucleus
(Culex quinquefasciatus)
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Malaria spread among
bird populations
Honeycreeper with malariatransmitting mosquitos
Ecological consequences – Hawaii
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High mortality due to lack of
resistance
Contributed to the extinction
to >10 native bird species
Limits geographic distribution
of birds
Hawaiian honeycreepers
Ecological consequences – Hawaii
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Control difficult due to
remote habitats
Mosquitos benefit from
another invader: feral
pigs (Sus scrofa)
Water-filled wallows
serve as breeding
locations for mosquitos
Der Nematode ist der Parasit:
Anguillicola crassus
Natürliche Bedingungen: saugt Blut in der Schwimmblase des
Japanischen Aals (Anguilla japonica).
Globalisierung: hat Aalarten anderer Kontinente, die mit dem Parasiten
keine Koevolution durchlaufen haben, als naive Neuwirte
Anguillicoloides crassus
kolonisiert. Wurde selbst nicht als Wirt von Parasiten oder
Pathogenen beschrieben.
Life-cycle of Anguillicola crassus
Natural and introduced range of A. crassus.
Red area: distributional range of Anguilla- species naturally infected by A. crassus
(Anguilla japonica) and colonized eel species in Europe, America and Africa
How is invasion success determined?
The enemy release hypothesis (ERH):
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Biogeographical studies:
 examine native and introduced
populations of invaders
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Confirmed
release from
enemies,
impact on
invasion
suggested
Community studies:
 compare native and introduced
species within the same
community
Invaders do
not have less
enemies than
the native
species
Colautti et al. 2004
How is invasion success determined?
The enemy release hypothesis (ERH):
Hypotheses opposing the ERH:
 Propagule/sampling bias
 Community interactions or abiotic factors
reverse/reduce enemy effects
 Effects of newly acquired enemies:
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NIS are naive hosts
Genetic bottleneck leads to higher susceptibility
Ticks: Acari, Ixodida
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About 900 species in two major families:
Argasidae (ca. 180 spp.) and Ixodidae
(ca.720 spp.)
Almost all species spend much more time
free-living in the environment than on their
hosts
About 5-10% of species are of medical or
veterinary significance
Three families
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Argasidae
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Ixodidae
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The soft ticks (Lederzecken)
The hard ticks (Schildzecken)
Nuttalliellidae
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A monospecific family (Nuttalliella namaqua)
The lifecycle of ixodid ticks
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Three-host ticks
Larvae
Nymphs
Adults
Eggs
Transstadial transmission
Transovarial transmission
I. ricinus: larvae, nymphs and adults
Ticks as vectors
Ticks are the most important
vectors of pathogens to domestic
animals and the second most
important to humans
Tick-borne diseases
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Viral (e.g. CCHF, TBE)
Bacterial (e.g. Borrelia, Ehrlichia,
Rickettsia)
Protozoan (e.g. Babesia, Theileria)
Environment and hosts
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Tick distribution appears to be largely controlled by
the environmental conditions available to the free
living stages (eggs, larvae, nymphs and adults),
especially temperature and humidity
Host availability may also play a role but many
economically and medically important species use a
wide variety of hosts (e.g. Ixodes ricinus,
Amblyomma variegatum)
Tick distributions and global change
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Substantial changes in various species, e.g.
I. ricinus in Europe
Evidence that these may be due to climatic
changes (e.g. Finland, Czech Republic)
Also suggestions that political, social and
habitat changes may be involved (Randolph 2004)
Food-borne trematodes
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Opistorchis viverrini, the small liver fluke
Mekong area: Thailand, Laos, Cambodia, Vietnam
10 million people infected in Thailand and Laos
alone
Infection by eating uncooked freshwater fish from
the cyprinid family
At the taxonomic level: how many species are
present?
From: Andrews et al. 2008
Trends in Parasitol
Pathogenicity
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Causes liver and bile duct problems;
blockage
One of the two species classifies by WHO as
a carcinogen
Long-term infection can lead to
cholangiocarcinoma (bile duct and later liver
cancer)
www.stanford.edu
www.nri.org
Road constructionmore pondsstocked with infected fishhigh human prevalence
Problem
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Symptoms and disease prevalence in the
human population in the northeast of
Thailand and southern Laos vary
geographically
Does this variation have a population genetic
basis: i.e. due to variation in O. viverrini