L16: Species Distribution Modelling

Question 1

Why are species distribution models important?

Answer 1

1) Species ranges are shifting, contracting, expanding, and fragmenting in response to global environmental change (Chen et al 2011).
2) The emergence of global databases has provided new opportunities to analyse species occurrence data in support of conservation (Jetz et al 2012) and evidence-based approaches (Sutherland et al 2004)

Question 2

What is a species’ distribution model?

Answer 2

These are models that can predict how species are distributed by using what is already known with digital layers of environmental variables.

Question 3

The most common strategy for estimating the actual or potential geographic distribution of a species is…

Answer 3

First get an idea of the environmental conditions that are suitable for the species, and then identify where these suitable environments are located (Guisan and Thuiller, 2005).

Question 4

Define niche

Answer 4

The total requirements of a population or species for resources and physical conditions.

Question 5

Fundamental niche

Answer 5

The niche a species could occupy if only limited by the environment, and not by interactions with other species. Absence of any interspecific competition and predation.

Question 6

Realized niche

Answer 6

The observed ecological space a species uses – subset of entire fundamental niche.

Question 7

The degree of equilibrium depends…

Answer 7

both on biotic interactions (competitive exclusion from an area) and dispersal ability (organisms with higher dispersal ability are expected to be closer to equilibrium than organisms with lower dispersal ability) (Araújo and Pearson, 2005).

Question 8

Limitations of this type of data

Answer 8

1) Incorrect identification of the sp. or coordinates.
2) Researchers uploading data might be biased towards easy access places (Graham et al., 2004).
3) Museum data is also used. Often biased towards rare sp
4) Are highly sensitive to the assumptions, algorithms, and parameterizations of different methods (Araújo et al, 2005).
5) Assume equilibrium between species and their environment. “A species is at equilibrium with the physical environment if it occurs in all suitable areas, while being absent from all unsuitable areas“.

Question 9

Maximum Entropy (MaxEnt)

Answer 9

1) MaxEnt is a very general way to predict probability distributions.
2) Predict species’ distributions based on environmental covariates.

Question 10

How to build an SDM

Answer 10

Start with a map with lots of different data point (occurrence of species)- present data you want to model.

Different layers of environment co-variates- e.g precipitation, seasonality, soil type etc

Upload to software called MaxEnt to build an algorithm and build up a concept of niche.

Question 11

Limitations of this type of data

Answer 11

1) Incorrect identification of the sp. or coordinates.
2) Researchers uploading data might be biased towards easy access places (Graham et al., 2004).
3) Museum data is also used. Often biased towards rare species

Question 12

What are environmental covariates?

Answer 12

To describe the environment (the niche) where the sp. is present.

1) Climatic variables: Temperature, precipitation, etc.
2) Topographic variables: elevation, slopes. Etc.
3) Soil types and landcover.