Lecture 11: Climate Change Vulnerability - Lecture Outline (Part 2)

Methods

• Genetic Diversity (Ar and He)

• Genetic Isolation (FST)

• Geographic Isolation (Least-cost pathways)

• Maximum Elevation

• Forward Climate Velocity (from climate model predictions)

Geographic Isolation (Least-cost pathways):

Estimate how different/far apart one population is from another

Euclidean distance

Each pathway has a value

Maximum Elevation:

How tall a mountain range is provides more resources for sheep

Measure of current climate stress; lower maximum elevation is associated with higher temps, lower precipitation, and lower population persistence

How under stress would a population be currently

Predicting how threatened would a population would be if temperature increased

Forward Climate Velocity (from climate model predictions):

a measure of geographic movement rate required for an organism to maintain constant climate conditions

Methods: Forward climate velocity

Measure of speed and direction of regional climate change

Obtained gridded spatial data on forward climate velocity based on mean projections for 2050s from 15 global climate models (IPCC)

Under two emissions scenarios

What two emissions scenarios does the assessment use?

(1) ‘moderate’ and (2) ‘high’

What is the (1) ‘moderate’ emissions scenario?

RCP8.5: stable climate change by 2100

What is the (2) ‘high’ emissions scenario?

RCP8.5: assumes greater greenhouse gas emissions

Why is the Bighorn sheep assessment not wholly independent?

uses the same data as other assessments; estimates without evidence

Genetic Diversity results:

Most unique populations are in southern Utah, in Canyon lands, and arches

Five genetic clusters with different genetic patterns

• Clusters

• Translocations

• Bighorn are least genetically isolated in areas between Mojave, Death Valley, and Lake Mead areas

• Most isolated in mountains surrounded by desert flats in southern Mojave

Allelic richness:

measure of genetic diversity with alleles

Mean pairwise FST:

measure of genetic isolation; how different or similar are populations due to genetic structure

run from 0 to 1; determines population structure

• Low FST, ~0: no to little difference

• High FST, >0.5: a lot/greater difference

Mean effective distance:

how they manage geographic isolation from their 3 nearest populations

• takes into account topography, barriers, and distance

Forward climate velocity:

how much the population would have to move

Maximum elevation:

high mountain range doesn’t alter change

• Most vulnerable: lower elevation, isolate, fragmented, hot desert ranges (Mojave Desert)

Relationship between genetic diversity and genetic isolation:

shows a negative relationship

Relationship between genetic diversity and effective geographic distance:

shows a neutral relationship

Relationship between genetic isolation and geographic isolation:

shows a positive relationship; genetic isolation and geographic isolation go hand-in-hand

Most vulnerable:

Southernmost populations in the study area had the highest forward climate velocities

Southernmost populations in the study area also had:

lowest elevation

lowest genetic diversity

high genetic isolation

high geographic isolation

Least vulnerable:

Other populations, like DEVA and GRCA, had low forward climate velocities

Other populations, like DEVA and GRCA, in the study also had;

higher elevation

high genetic diversity

low genetic isolation

low geographic isolation

What do climate variability results help to do?

help NPS and other management agencies make more informed decisions about resource allocations among Desert bighorn populations

What are the perspectives discussed in the study?

All of the above