Biological Invasions Flashcards
(35 cards)
Describe deliberate invasion of rabbits from uk to australia and new zealand
Normans brought from france to UK for food.
Britons taking to Australia for food and pets – compete with other animals
Lots of rabbits in Australia died from Myxomatosis which was introduced as a biological control agent
Describe potential ecological impact of invasive species
Dinomis maximus - common in new zealand but went extinct (probably from hunting, predation of eggs and nests by rats from polynesians).
Blue-footed booby and rat - many ground-nesting birds produce lots of chicks - cascading ecological consequences of rats hunting bird nests - nutreitn from guano decline, negative effects leading to reduced grazing and bioerosion of the reef.
Describe potential economic impact of invasive species
Weevil - eats purple loosestrife (isn’t native to america and grows really fast there so introduced weevil to control - success)
Zebra mussel - Likes to sit in water cooling pipes of power stations and completely clog the pipes, stopping the power station working and causing billions of dollars of damage in the US
Describe how an example of “natural experiments” can teach us about natural relationships in communities
Disrupt natural community with an invasive species.
Mount st helens, Washington state – 1980 eruption obliterated life for miles around, leaving debris of pine trees being knocked over and rich volcanic soil but no life watch recolonisation and how communities rebuild
Describe the process of invasion
Arrival
Introduced
If it succees, establishment (approx 10%)
Lag
Spread
Approx 10% of those that establish will have major effects on the environment
Who came up with the tens rule estimate
Williamson and Fitter, 1996
Why is invasion difficult?
Ecology – many species are not adapted to the ecological conditions that they find themselves in
Genetics – massive genetic bottleneck because only a few individuals have travelled from the source population homozygosity and problems with recessive alleles becoming visible in the phenotypes
Humans – tend to do everything we can do to stop them invading, especially last 50 years
Describe why invasion is puzzling becaue of local adaptation and competition paradox
should be outcompeted by better adapted native equivalents
Brook trout (Salvelinus fontinalis) is American fish living in freshwater rivers native to eastern US
Western to rockies Rainbow trout
Tried introducing them reciprocally – invasive can outcompete native one in the native ones’ range
Describe genetic reasons for invasion lag
Propagule pressure driving diversity - e.g. brown anole restricted to 1 county in florida but spread to whole of it - maybe this 50 years before anything happened, it was slowly being joined by other members of the population and accumulating genetic diversity > overcome problems caused by genetic bottleneck > competitive in new environment and starts to spread.
Alleles never found togther in European populations now found simultaneously in american population - more genetically diverse population ready to compete with native grasses.
Local adaptation - 50 years is enough time for natural selection to start shaping the species for the environment in which it now finds itself i.e. genotypes which are doing well in this new environment will be favoured.
Hybridisation with local species e.g. Spartina anglica = S. maritima + S. alitflora. Most successful invaders are capable of hybridising across species boundaries because the boundaries aren’t necessarily well policed by the mechanisms that normally stop you hybridising because these are species that haven’t evolved together > i.e. no great imperative stopping them from sharing genes
Describe allee effects as an ecological reason for invasion lag
At very low population densities, population grows slower the smaller the population gets (find harder to get mate). Allee effect = reverse density dependence
Describe stochasticity as an ecological reason for invasion lag
Random fluctuations in conditions are more likely to kill off the small populations
Less likely to negatively affect larger populations
Describe complex dispersal as an ecological reason for invasion lag
Reaction diffusion dispersal = hops a short distance, has babies, they hop a bit further and have babies there small distance, continual gradually get continual increase in range size with time
Stratified dispersal = some offspring fly a long way and establish colony further away > get island/colony of birds surrounded by space with none > islands start to grow and coalesce, appearing as acceleration in range occupied by the species
Describe ecological dependency as an ecological reason for invasion lag
Species is waiting for another species to colonise because it might not have any food or suitable host plants in the new environment
Wait until invasive species from their original habitat establishes to provide them with food
Success of invasive herbivorous insects is predicted by success of invasive plants 100 years previously (Bonnamour et al., 2023)
Describe enemy release as a solution
unless you’re unlucky, your natural enemies (predators, parasites and diseases) won’t arrive at the same time as you you can compete with native species which have their coevolved predators, parasites and diseases there.
Unlikely to arrive coincidentally
Parasite/predator will suffer same things but probably magnified as they are at higher trophic level and lower density – Enemy bottlenecks, Allee effects, host/prey density too low
Describe assumptions and caveats with enemy release as a solution
Assumption that enemies matter – not necessarily a top down ecological factor that determines how successful a population is – it’s normally a bottom up factor such as food availability or competition for food with an equivalent ecological species
Important enemies (i.e. prevalent parasite) are likely to travel at the same time as you
Susceptible to native enemies – not coevolved with these ones so may not have defences against the predators or parasites they’ll face in the new environment
The enemy of my enemy is my friend! – success appears to be partly because their enemies are a bigger problem for the native species than they are for the invasive species (because they’re the ones that have coevolved together)
Describe novel weapon hypothesis
Invasive species may carry mechanisms for competing with other plants that the competitor’s back home are coevolved to deal with but naïve competitors in new environment aren’t coevolved to deal with
Describe short term gain, long term pain paradox.
Rainbow trout (Oncorhynchus mykiss)
Looks like in short term they’re more successful as introduced species than as native species
Over the long run may not work e.g. drought regimes being very different will mean they likely have different adaptations to allow them to survive in really bad years, but invader will be less successful in these rare, bad events
Describe vacant or uncompetitive niches
Invasive species may have solution to a problem that’s never been solved or even seen in the habitat that’s being invaded
E.g. Zebra mussel (super successful in north America – the power industry one) has Byssus threads which it attaches to rocks with and are very hard to detach with in fast moving water
Before its arrival, niche of filter feeding in fast flowing streams was filled by mayfly larva with a different method
Zebra mussel doesn’t have to outcompete another bivalve
Most likely to happen in isolated and small patches of habitat > oceanic islands are particularly vulnerable to biological invasions because of this
Describe herbivory, predation and parasitism as a direct vertical ecological impact of invasion
Brown tree snake (Boiga irregularis) introduced in many pacific islands where there was previously no ground dwelling prey.
Will eat ground-dwelling Chestnut munia (Lonchura malacca) on Guam which has evolved without any ground-dwelling predators
Direct trophic impacts on prey
9 example endemic bird species on this island, ~5 at least gone extinct due to the bird
Rabbit in Chalk grassland
South and North downs – chalk downs have higher botanical diversity than any other part of the UK
Almost certainly the result of close grazing of rabbits and deforestation from humans – would’ve previously been covered in juniper (very rare and now mostly wiped out in the UK)
Describe prey for native enemies as a direct vertical ecological impact of invasion
European Gall fly (Urophora sp.) introduced to north America and native Deer mouse (Peromyscus maniculatus)
Large part of year, diet of mouse is dominated by invasive fly species
Describe competition as a direct horizontal ecological impact of invasion
On Pacific islands, invasive gecko Hemidactylus frenatus is competing with the native Lepidodactylus lugubris and replacing it
Petren and Case (1996)
Huge drops in health condition, survival and fecundity when invasive species is present compared to native alone
Interestingly, asymmetric competition – see higher fitness in invasive populations that are coexisting with high populations of native species
Describe ammensalism, commensalism and mutualism as a direct horizontal ecological impact of invasion
Invasive Crazy ant (Anoplolepis gracilipes) and Coccus sp (scale insect)
Bug sucks out honeydew they don’t need (need protein instead) so feed it to ants who in return protect them from predators and parasites
Describe apparent competition as a indirect and complex ecological impact of invasion
Two species with same position in the food web apparently competing for food but one, or both, has really negative effect on the other, as a result of shared natural enemies
Seven-spot ladybird (Coccinella septempunctata) and invasive (from central asia) Harlequin ladybird (Harmonia axyridis)
Harlequin carries spores of a parasitic microsporidia which is benign to them but lethal to other species of ladybird
Looks like one has negative impact on the other which looks like its due to food competition but is actually a result of a shared natural enemy, the parasite > why it’s called apparent competition
Describe trophic cascades as a indirect and complex ecological impact of invasion
Gypsy moth (Lymantria dispar) is European moth that feeds on trees and has been introduced to north America. Huge problem for the timber industry as it attacks trees and is free from natural enemies there.
Native deer mice love to eat gypsy moth so in years where trees do well, you get a lot of gypsy moth and get lots of mice
Mice carry a native tick which is then doing well when there are loads of trees, moths and mice
Deer get a lot of ticks and drop them in many areas that humans live
More humans get lyme disease caused by Borrelia burghdor
