Population viability analysis

Question 1

What is PVA

Answer 1

describes an entire process

evaluating information from a population, running models, determining probability of a population persisting into future, often experimenting with different conditions. Can relate to conservation intervention eg assessing options

Question 2

What is MVP

Answer 2

Minimum Viable Population- minimum number required to ensure persistence of population at some time eg 99% over 4 generations, 95% probs of persistence over next 100 years. As long as estimates defined can interpret data

Question 3

PVA models

Answer 3

Can buy software that is becoming increasing bespoke. Remains controversial.

Has been found to be accurate for retrospective data- but this was for organisms with lots of data surrounding them. We are interesting in organisms that don’t have long, detailed data sets

Plus catastrophes can cause extinction (bramble cay melomys) these cannot be predicted.

Question 4

Misuse of MVP

Answer 4

Empiricial (case-specific) and theoretical (genetic) estimates of MVP. Median estimate around 5000 individuals but huge variations around this.

So should we assess the importance of looking after species based n how far they are from 5000? Potential misuse of this. Concept of triage, give up on some spp who aren’t going to make it. Money could be better spent else where

Some people developed index called Species’ Ability to Forestall Extinction (SAFE) Lower a species on SAFE less likely they were salvageable so should be lower funding priority

BUT

5000 is not a magic number. No clear variation between taxa for MVP and yet so much variation within taxa
- grizzly has 9 estimates from 400 - 44,0000. Variability depending on circumstances of the population. Generalised MVPs do not account for threats. Genetic evidence for consistency is weak. Why do we need a guideline for MVP? (Caughley’s declining pop para? 1994)

MVPs don’t help us understand cause of decline

Variability because if an animal is in a poor quality habitat with lots of threats MVP will be higher. 5000 tries to put everything into the same situation. Plus when we generalise we don’t account for anthropogenic threats, genetics (eg woodhen was cool with 20 indivis at one point- would have been written off

Question 5

So is PVA a waste of time?

Answer 5

Nah

Can be tailored to fit specific situations

Bayesian analysis (answers research questions about unknown parameters using probability statements) of parameters to make use of diverse information sources. Recent models have successfully informed management of disease, hunting and conservation

Haydon et al (2002) found from modelling the biggest threat to wolves was disease. Showered how much a difference vaccinating domestic dogs would have –> successful

Fordham et al (2008) worked out what threats to alleviate for tortoise
1. Aboriginal exploitation for food
2. Predation from feral domestic pigs
If you control the pigs you don’t need to do anything about the traditional practises