lecture 11b: invasive ecology 2 Flashcards
(17 cards)
IPBES Global Assessment Report on Biodiversity & Ecosystem Services (2019): Invasive spp at #5 for biodiversity impact
See goals figure in notes
While there is progress in prioritizing impactful IAS for management, control/eradication is poor
In many of these goals progress level is poor
also see: http://www.millenniumassessment.org/en/Synthesis.html
^ details on major human impacts on ecosystems
Main types of impact
*All established alien species, through their interactions with native species or the abiotic environment, will have some impact
*Some species have much stronger impacts than others
*Impacts can be ecological, economic or social
Ecological impacts of invasives: an overview
-Reduced abundance and distribution of native species
-Diversity and species loss (extinction)
-Impacts via trophic interactions
-Effects on community and ecosystem processes
Reduced abundance, performance and diversity: Himalayan Balsam study
Many studies have measured impact of invasive plants by comparing invaded and neighbouring non-invaded patches
Using meta-analysis: invasive plants largely have negative impacts on native diversity, abundance and fitness across studies:
See figure in notes
Vila et al. (2011) Ecology Letters 14: 702-708.
Data review ‘meta analysis’
Productivity increases and the majority of other areas reduced
Extinction threats : IAS
How much of an extinction threat are invasive alien species (IAS) compared to other threats?
see figure in notes
^ Map shows number of vertebrate species on IUCN Red List as threatened by IAS (for regions with >25% species threatened by IAS)
(^ Bellard et al. (2011) Proceedings of the Royal Society B 283: 20152454)
Major vertebrate taxa have many species that are endangered (IUCN red list), due to IAS
Major ISA groups:
batrachochytrium dendrobatidis (funghi that infects amphibians)
rat,
cats,
dogs,
wild boar,
goat, cattle
Examples of IAS and the species they impact:
Chytrid fungus -> Amphibians
Rats and cats -> Birds and mammals
Effects of Batrachotrychium fungus on snakes
*Amphibians an important prey item for snakes
*Batrachochytrium dendrobatidis (chytrid fungus) has spread through the Neotropics, causing catastrophic loss of frogs
In a Panamanian rainforest, snake diversity is in sharp decline due to loss of prey
see: Zipkin et al. (2020) Science 367: 814-816
^ Body condition (weight per unit volume) of snakes had declined after fungal disease outbreak in amphibians for multiple species
Brown Tree Snake, Guam: bird declines affect spider abundance, and plant recruitment see : http://www.bbc.co.uk/news/science-environment-17992053
&
Rogers et al. (2012) Plos One 7:e43446; Mortenson et al. (2008) Biological Conservation 141: 2146-2154
IAS example: Cane Toad (Australia)
Cane Toad Australia
*Introduced to Queensland, 1935
-3000 individuals released, biological control of sugar cane grubs
*Biocontrol of sugarcane grubs failed, but the toad established and spread
*Main impact is on predators
-Northern Quoll
-Snakes
-Monitor Lizards; finch prey benefitted
see figure from:
http://www.environment.gov.au/biodiversity/threatened/key-threatening-processes/biological-effects-cane-toads; Doody et al. (2015) Ecology 96: 2544-2554.
Altered ecological processes
Soil nutrient and carbon cycling are affected by the composition of plants growing in a community
Soils invaded by alien plants can have altered nutrient availability microbial activity
May be driven by N-fixers/species with nutrient rich plant material (N fixers are the closed triangles)
See figures from Vila et al 2011 ecology letters
Water Hyacinth (Lake Victoria)
*Appeared in late 80s
*Vegetative spread, mat-forming
↓ in Dissolved oxygen
↑ in macroinvertebrates (snails)
^ Shifts in prey of Nile Perch (also introduced!) to macroinverts
-Mats block access to Perch/Tilapia spawning areas
Water Hyacinth decline initiated in late 90s by introduction of biological control (weevil)
See: Wilson et al. (2007) Aquatic Botany 87:90-93; Villamagna & Murphy (2010) Freshwater Biology 55:282-298
Hybridisation
^Ruddy duck interbreeds with natives threatening native duck
^ spanish bluebell hybridises with british bluebell
What determines ecological impact
Impacts can be driven by the nature of the interactions invasive species have with native species, which can be underpinned by:
*Novelty
-New predators
-Novel defences (‘weapons’), e.g. toxins
-Evolutionarily naïve natives
*Similarity
-Greater fitness than natives, but overlapping niches leads to competitive exclusion
-Hybridisation
How do we classify species based on impact in a standardized way? IUCN EICAT
Categorizing invasive species based on impact can assist with prioritising species in biosecurity and management policy (Blackburn et al. 2014, PloS Biology, 12: e1001850)
IUCN Invasive Species Specialist Group: Environmental Impact Classification of Alien Taxa (EICAT)
See figure of EICAT categorisation in notes
Assess evidence of impact, categorise into one of 5 impact scenarios:
Massive, Major, Moderate, Minor, Minimal
Following impact types assessed:
- Competition
- Predation
- Hybridisation
- Disease transmission to native spp
- Parasitism
- Poisoning/toxicity
- Bio-fouling
- Grazing/herbivory/browsing
- Chemical/physical/structural impact
- Interaction with other alien species
Overall species impact category = highest impact across all 10 types
EICAT has now been extended to EICAT+
Recognizes that introduced established species can have positive impacts on native biodiversity and ecosystems (Vimercati et al. 2022, PLoS Biology, 20: 33001729)
See EICAT+ figure in notes
Positive impact example: Prickly Pear
*Prickly pear (Opuntia ficus-indica) invading Nairobi National Park, Kenya
*Ungulate herbivory of palatable plants can be intense
*Native plant richness and diversity higher in areas invaded
*Recruitment and survival may be higher in the invaded than uninvaded vegetation (facilitation)
See: Oduor et al. (2018) Biological Invasions, 20:2745–2751
Economic impacts
Damage to infrastructure; loss of earnings and opportunity (agriculture, fishing, forestry); management and removal costs; energy costs…
see figure:
Global database of economic costs of invasive species found a total cost of US $1.29 trillion from 1970 to 2017. (Diagne et al. (2021) Nature 592: 571-576.)
Social Impacts
Social impacts
*Loss of resources, or access to them; health
-Ambrosia artemisiifolia
-Extension of high pollen count
period in Central Europe -> Hayfever
Negative impact prickly pear
- Prickly pear cacti (Opuntia) species: invading large areas of rangeland in Kenya
- Reduction in pastoralist livelihood (loss of high quality grazing and injury to cattle)- up to $ 1000/household/yr
See: Shackleton et al. (2017) Biological Invasions 19: 2427-2441.
