MAPPING ANIMAL FITNESS

ONTO SEASONAL CLIMATE CHANGE

F. Stephen Dobson

Department of Biological Sciences

College of Science & Mathematics

• GENERAL TOPIC: PHENOLOGICAL RESPONSES TO CLIMATE CHANGE

• GENERAL PATTERN: earlier dates of spring phenology with warming - including species at different trophic levels in the same habitats

• PROBLEM: because trophic links are involved, there may be mismatches between resources & reproduction for some of the species

specifically, breeding and peak resource periods may not match up

e.g., peak insect abundances and nestling feeding by breeding birdsoften coincide

Evidence of trophicinteractions

Typical story of timingacross trophic levels

1985 - 2005

This study compared

plant growthinsect development4 species - song birdsan avian predator

Both et al. 2009, JAE

Budburst

Caterpillars

Sparrowhawks

• GENERAL TOPIC: PHENOLOGICAL RESPONSES TO CLIMATE CHANGE

• SPECIFIC QUESTION: how much of the changes in timing is due to:

• Plastic responses of phenotypes• Genetic adaptations to new conditions

Breeding Date

cool warm

Spring temperature

A

B

Pattern:

Laying date is a week later than 20 years ago (b = 0.35 ± 0.05, p < 0.0001)[due to lower fish food abundance]

Heritability = h2 = 0.36 (± 0.05)

Selection gradient = S = -0.10

Breeder’s equation: R = h2 S

Conclusion 1: •natural selection favors earlier breeding, not later breeding!

Conclusion 2:

•later breeding due to phenotypic plasticity

Snow melted off significant later

Emergence from hibernation delayed

Lower fitness with later emergence

OVER 20 YEARS:

•Emergence 9.4 days later

Heritability = h2 = 0.23 (± 0.05)

Selection gradient = S = -0.14

Breeder’s equation: R = h2 S

Conclusion 1: •natural selection favors earlier, not later emergence from hibernation!

Conclusion 2:

•later emergence due to phenotypic plasticity

Population grew, then declined

Δ Fitness & Δ Climate:

Summer temperature has gone up:

+4.4°C, mean = 16.5°C

Summer rainfall has gone down:

-3.7mm, mean = 2.5mm

Fitness has gone down:

r = -0.428 (P = 0.05), with temp

r = 0.548 (P = 0.01), with rain

AnnualFitness

AprilSnowfallbefore

July Rain &Temperature

Nov – DecSnowfall

DecemberSnowpack

0.046

0.468*

0.047

-0.032

AprilSnowfall

after

-0.223