2. Plasticity and Maternal Effects

Phenotypic Plasticity and Maternal Effects Short-term responses to changing climates?

Changing Thermal Environments

Current Climate Models Predict an Increasingly Warmer World

Organismal response to rising temperatures

Ecological Response Shifts in Distribution Δ Phenology

Evolutionary Response: Adaptation

Failure to Adapt

Extinction

Creative Commons/Bart Heird

Another response (short term)

& Maternal Effects

Adaptive Plasticity in Novel Environments Reaction Norms – low cost to fitness persistence of plasticity

φ

Novel Low

Normal Range of Developmental Temperatures

Novel High

“Release” of cryptic variation in novel environments. Selection on G x E.. after Ghalambor et al. 2007. Functional Ecology 21:397

Acclimitization is one form of Plasticity

B. CIB

Fitness

A. BAH

Cool

Warm

Test Temperature

C. HIB

Cool

Warm

Test Temperature

Fitness

D. LAH

Cool

Warm

Test Temperature

Cool

Warm

Test Temperature

BAH, CIB, etc. • Most tests of these hypotheses involve Developmental Plasticity – i.e., irreversible phenotypic changes induced by rearing conditions

Plasticity in Reproduction • How do gravid (pregnant) females respond to warming?

Reproductive Plasticity in Females

Manipulation of thermal regime experienced by gravid females

Developmental stage is sensitive to thermal conditions experienced by gravid females

Reproductive Investment

Why Females?

Females can manipulate the phenotype of her offspring depending on intrinsic and extrinsic conditions

Hormones (Cort, Androgens), Tb of dam

How can females affect offspring phenotype? • Hormones • Offspring Provisioning • Incubation Temperatures during embryonic development – Viviparous Lizards • Maternal Tb

– Oviparous Lizards • Nest Site Selection

How does elevated CORT Altered niche attributes initiate effects and costs of immune response mediate stress response offspring quality

Population dynamics Consequences

Rising Temperatures

Extended Warm Spells

Maternal Condition

ReproSuccess/ Offspring Traits

Decreasing rainfall Adaptive maternal effects (mainly organizational effect of hormones and immunity products) modify individual strategy and survival later on. One outcome is the induction of offspring phenotypes to cope with novel environments.

Altered Population Dynamics

Maternal Effects & Developmental Plasticity Stressor CORT

Could be Ta

Energy Stores ¥

Maternal Survival Clutch Size/Offspring Size Trade-off Offspring “Quality”

Dispersal

Philopatry

Growth Rate

Body size affected by incubation temperature

Speed is sensitive to incubation temperature

Hormones and Offspring Phenotype

CORT treated lizards remained in shelters longer than controls

Plasticity in Dorsal Pattern

Zootoca (=Lacerta) vivipara

Mechanism of Induction

Juvenile dorsal pattern affected by: May Ta during Gestation August Ta year before pregnancy

x

Significance of Dorsal Pattern

Behavior and performance covary with dorsal pattern Brodie 1992 Evolution

Temporal variation in % reticulated morphs Frequency of Reticulate females decreased with elevation only in 2008 “Cool” Year

Evidence for plasticity in morphs

Maximum velocity increased with habitat openness F3,349 = 3.05, p < 0.02

Speed differed between years F3,349 = 7.82, p < 0.001

Speed differed between morphs F3,349 = 3.35, p < 0.01

Number of stops increases with habitat openness

Reticulate females stopped more frequently than linear females

Chi-square = 5.42, P < 0.01

Conclusions • Climate can induce variation in reproductive performance • Variation in conditions experienced by females can affect offspring phenotype – Whether female manipulation benefits offspring depends on conditions at hatching (birth)