Invasive plants

Question 1

describe Bayesian methods

Answer 1

the likelihood of events depends on our prior assumptions (having prior knowledge of an event is ideal = we can include expert input; predictions are constantly updated as more data becomes available)

Question 2

what is invasibility?

Answer 2

likelihood of invasion by pests (cause harm); deeply connected with temperature and other climatic factors (precipitation); climate change increases risks; models allow for graphic identification of geographic regions more likely to receive invasive species, depending on the climate of each region

Question 3

what is fundamental niche?

Answer 3

conditions and resources allowing species to exist (thus allowing invasion); each point in the map (biotope = geographic) would allow species to live indefinitely, depending on factors that limit the fitness of a given organism

Question 4

what is potential niche?

Answer 4

(smaller) portion of fundamental niche that actually exists in specific space and time

Question 5

what is realized niche?

Answer 5

smaller (than fundamental and potential) environmental space where species actually exists. It is smaller because of biotic interactions (predation, competition), source-sink relationships (sink populations can make realized niche bigger than fundam/potential), dispersal limitations

Question 6

“In the case of invasive species: the fundamental niche concept is more relevant to predict where an invasive species can eventually be located”. Why is that so?

Answer 6

1) Dispersal limitations no longer exist (the species was taken there, “it got a lift from humans”)
2) These new locations are outside its native range (outside realized niche)
3) Overestimation will occur, but at least models will list locations where species can live if conditions allow (biotic and abiotic)
4) Adaptive evolution to new conditions must be considered (should I model a species considering its current genetic pool only? Better to think about traits likely to be under selective pressure)

Question 7

what are mechanistic models?

Answer 7

based on mechanisms or processes instead of patterns. Examples: physiological, life history, phenological, functional traits. These processes are critical to survival and fecundity (constrain distribution and abundance of species). Such models link these processes with environmental data to map predictions of fundamental niches.

Question 8

what are correlative models aka species distribution models (SDMs)?

Answer 8

“are based on relationships between observed species locations”; are based on realized niches; presence-absence info and environmental covariates
Example of correlative model: Maximum entropy (MaxEnt)

Question 9

1 advantage and 1 disadvantage of presence-only method (correlative models)

Answer 9

simple to use; easier because this data is more widely available (but problem is bias in records, eg., towards urban centers)

Question 10

most invasion studies are reactive, what does this mean?

Answer 10

conducted when alien plant has already established; large economic and ecological costs

Question 11

give 1 characteristic indicating increased risk of successful invasion?

Answer 11

number of introduction episodes (eg., bird releases)

Question 12

cite 3 areas affected by invasions

Answer 12

economic, ecological (threat to native species and ecosystem function), human health damage

Question 13

what can exacerbate invasions?

Answer 13

increased risks globalization/climate change

Question 14

what are the 4 phases of invasion?

Answer 14

1. transportation
2. release = introduction (amount of individuals; frequency of introduction attempts; and time since first introduction matter here)
3. establishment
4. spread
   (most studies focus on these 2 last phases, which is problematic, as early intervention works best)

Question 15

what is an invasive plant?

Answer 15

non-indigenous plant which is able to become widely spread and cause damage

Question 16

what are the patterns found in invasive plants?

Answer 16

• propagule pressure (associated with commercial activities; release phase of invasion)
• unevenly distributed phylogenetically
• have a history of invasion (either the species or related species)
• reproduce vegetatively
• have low variability in seed crops
• origin region (although 1 study found that climates do not determine invasiveness)

Question 17

what is not important for invasiveness?

Answer 17

annual/perennial; length of flowering period

Question 18

what is the second leading factor resulting in species endangerment in USA (second to land use)?

Answer 18

biological invasion

Question 19

what mechanisms can explain plant invasion causing impacts such as reduction of biodiversity, fires, etc.?

Answer 19

competition, allelopathy, production of flammable biomass, change in ecosystem processes such as nitrogen cycling

Question 20

what are the most significant plant invasion effects according the literature reviews?

Answer 20

alteration of fire regimes

Question 21

explain why a trait-based analysis is appropriate to investigate effects of invasion (nitrogen-fixing example)

Answer 21

we need to match invader traits with native traits: eg., impacts of nitrogen-fixing invaders are significant only if native species to be replaced are not nitrogen-fixing themselves

Question 22

define and give an example of positive feedback in plant invasion

Answer 22

• the effects of the invader benefit the long-term establishment of the invader itself
• greatest threat to ecological systems
• example: duckweed mats intercepting light and eliminating competing phytoplankton = more resources are now available for duckweeds = positive feedback

Question 23

what does meta analysis on traits indicating high performance show in terms of invasive species performance?

Answer 23

when measuring traits such as growth rates, size, physiology [photosynthesis, water, nitrogen use, etc.], leaf-area allocation, shoot allocation, and fitness (number of seeds, flowers, etc.), invasive species showed increased measurements for all traits (many traits are associated with each other, ie., leaf area and dry biomass), indicating faster growth of invasives across taxonomic groups / across environments (disturbed, high availability of resources; low sample size for this)

Question 24

what do studies show in terms of invasive alien x non-invasive alien?

Answer 24

not well studied, important for risk assessment protocols

Question 25

what do studies show in terms of invasive x native which is invasive elsewhere?

Answer 25

non-significant differences

Question 26

what are the most relevant groupings for investigating invasive species performance?

Answer 26

by phylogeny (we are more likely to see invasive species advantages when comparing 2 species from the same family); growth form

Question 27

what is invasibility?

Answer 27

likelihood of invasion (e.g., high invasibility in the same climate zone as native range of an invasive species)

Question 28

what is biotope?

Answer 28

the geographic location of a species’ niche

Question 29

when we predict a location where an invasive species could potentially invade, what kind of niche are we talking about?

Answer 29

we are talking about a given species going from its realized niche (native range) to a fundamental niche (invaded area)

Question 30

which niche is better suited to predict invasion risks in geographic locations?

Answer 30

fundamental niche

Question 31

for SDMs (species distribution models), what is the most important thing to consider when modelling the realized niche?

Answer 31

the realized niche is modelled and it is possible to characterize the fundamental niche as well. it is very important to consider the environmental variables which are relevant for the organism being studied (eg., phosphorus concentration)

Question 32

what can be done to improve SDMs (species distribution models) so that they predict fundamental niches instead of realized niches?

Answer 32

adding physiological data

Question 33

why are SDMs (species distribution models) more accurate for species without significant pathogens, pests and competitors?

Answer 33

because biotic interactions in the native range are very hard to quantify and include in SDMs. however, when these interactions are important for invaders, SDMs are not able to predict well distributions in the invaded range.

Question 34

how do species records affect the predicted distribution?

Answer 34

accuracy in terms of taxonomy, location precision, and abundance

Question 35

what is the problem of having just a few records for SDMs (species distribution models)?

Answer 35

this limits how many parameters can be fitted (limits the overall complexity of model)

Question 36

correlative SDMs assume that each record is an independent sample. is this true for records in very close proximity?

Answer 36

no, due to spatial autocorrelation, which needs to be adjusted in models to avoid survey bias (some places have more info than others); some techniques include using spatial blocks (Kim’s paper on giant hogweed)

Question 37

what are the common errors of online databases in terms of invasive species records?

Answer 37

duplications and errors (taxonomic, for example)

Question 38

what is the most common type of data (presence-only, presence-absence, or abundance) in SDMs?

Answer 38

presence-only (more commonly found)

Question 39

what are the requirements for presence-absence and abundance data in terms of SDMs?

Answer 39

invaded regions need to be occupied for a long time for us to observe persistence and reach stable population states (in case of abundance) or to die out.

Question 40

what are the advantages and disadvantages of using presence-absence and abundance data in terms of SDMs?

Answer 40

advantages: SDMs can approach fundamental niches when using them (conditions of environments are more closely modelled)
disadvantages: because invading populations are not in equilibrium in invaded areas (records will be too low, or too high, reflecting dispersal limitations and environmental preferences), and this is a violation of SDMs principles