assisted migration Flashcards
Loss et al. 2011
mostly against AM but says current practices in nature conservation are not enough.
increase landscape connectivity
highly manipulative, conflicts w/ principles in nature conservation and idea of letting mother nature take control
doesnt address root issue of climate change
don’t have rigorous testing - how do we know which species are best for AM?
There’s too much bias to forest ecosystems without acknowledging others
potential for change in species composition and genetic disruption; for species to become invasive
not economically plausible
reliance on models, none of which encompass all aspects of ecosystem
aitken and whitlock 2013
pro AM and genetic diveristy/rescue
can maximise benefits of gene flow while minimising its costs
introduction of new genetic material can facilitate future adaptation of phenotypes to new environmental conditions.
increase survival rate, fecundity, production of ecosystem services, population size.
higher genetic variation = higher adaptive capacity
can avoid risk of drowning out original local genotypes by introducing a limited number of individuals e.g. 20% in first generation and then 2-4% in subsequent ones
anti AM: could cause outbreeding depression.. but this is usually temporary and epitasis resolves this.
Whitely et al. 2015
AM can be used as form of genetic rescue = increase population fitness owing to immigration of new alleles
assisted gene flow to move individuals into populations to reduce local maladaptation to climate or other environmental change.
advanced technologies have emerged in genomics and data analysis/computational capabilities… could all be used to ensure assisted migration is successful in both short and long term
particularly viable for large pops w/ high fecundity, such as many trees, because inbreeding rates should be low and selection can reduce chances of genetic drift.
adaptive management is best.
Hunter (2007)
candidate species can be characterised by probability of extinction, vagility & ecological roles.
Species unlikely to disperse/colonise on their own because of limited vagility = prime candidates.
species w/ major ecological roles are riskier to move b/c they’re more likely to cause dramatic change.
sites are important. disturbed sites will be more publicly accepted than e.g. old growth forest.
isolated sites more likely to harbour unique biota and more vulnerable to disturbance.
no strong case for AM due to cost, tech, humanness
Hamilton & Miller 2016
Introgression = transfer of genetic information from one species to another as a result of hybridisation between them and repeated backcrossing. Movement of genetic material from one genome to another through repeated inbreeding
Interspecific gene flow between populations that exhibit strong ecotypic differentiation may represent an under-utilised management option
HYBRIDISATION offers increased capacity for adaptation, potential range expansion in changing climate, persistence of genes at risk of extinction (if parents are going to go extinct in some way, don’t we want to protect genes in some way)
evolutionary rescue results in change in genetic composition of a population to increase the frequency of adaptive alleles and leads to an adaptive evolutionary response
Anderson 2016
if species can’t adapt at the same rate as climatic changes, they will go extinct, so broadening their ranges now may help populations survive.
many species can’t disperse fast enough.
climate changes have fitness consequences. anthropogenic activities are speeding up these changes and even rapidly migrating species can’t keep up.
contraction of populations = loss of genetic diversity and adaptive potential, smaller pops attract less pollinators and reduce plant fecundity.
species have moved into other habitats before due to changing climate i.e. woody plants into semi arid areas or shrubs into alpine
populations need genetic variation to adapt to changing local climates otherwise there could be lowered emigration rates and increasing extinction risks. changes in climate have already altered trait selection in natural populations.
Arguments FOR Assisted Migration
Genetic rescue / evolutionary rescue - help move alleles around that are adapted to changing climate (Anderson 2016; Aitken and Whitlock 2013; Whitely et al. 2015; Hamilton and Miller 2016)
Hybridisation is a good thing and has conservation management potential (Hamilton and Miller 2016)
It’s going to happen anyway, we’re just helping (Anderson 2016; Hamilton and Miller 2016 in regards to hybridisation)
Moral responsibility (Anderson 2016; Loss et al. 2011)
Adaptive management is best (McLachlan et al. 2006; Whitely et al. 2015; Hunter 2007)
Ricciardi and Simberloff 2009
Species introductions erode biodiversity and disrupt ecosystems
Translocated species are risky
Uncertainty confounds risk assessment
Lag in time = difficult monitoring
Laikre et al. 2010
AM can cause loss of genetic variation, loss of adaptations, change in population composition, change to population structure.
AM already occurs for economic and recreational gains.
Seddon et al. 2009
IUCN translocations guidelines do not condone ‘early adoption’ of assisted colonisation as conservation tool.
caution against proactive conservation measures b/c of huge uncertainties involved in the climate-change predictions and species responses, and also in our understanding of what specie’s habitat requirements actually are.
Arguments AGAINST assisted migration
too much uncertainty about climate modelling, species needs, species responses effects of translocations on ecosystem function (Seddon et al. 2009)
too much uncertainty about whether not a species will become invasive. Could hinder global conservation efforts (Ricciardi and Simberloff 2009; 2021)
Seddon 2010
AM has been used to help species under threat of agriculture and urbanisation…
climate change reduces the usefulness of historic references for restoration
ecological funcitons once performed by now extinct taxa can be restored through ecological replacements, which could themselves be threatened
Creation of novel ecosystems should be well-considered
Ricciardi and Simberloff (2021)
current risk assessment techniques are unable to predict whether a species will become invasive after introduction to another region
