Transcript Slide 1

 Photoperiodic initiation of migration limiting flycatchers ability to
respond to long term climate change
Pineal gland involved in many photoperiodic responses:
-initiation of migration
- initiation of reproduction
- changes in pelage color
- molting / growth of winter coat
Pineal gland converts signals of light perception into an endocrine signal
Many hormones in photoperiodic response – melatonin often important
Melatonin synthesis: High during day
Low at night
Long photoperiod = increased melatonin = increase in gonadal activity
or maintenance of high activity
Short photoperiod = decreased melatonin = decrease in gonadal activity
or maintenance of low activity
 Critical photoperiod: threshold that divides long-day from short-day response
 Critical photoperiod differs by species often due to latitude of range
 Photoperiodic responses often less pronounced in equatorial vs northern species
Southern latitude
Critical photoperiod
~ 12.5 hours
Syrian hampster (Syria/Turkey)
Northern latitude
Critical photoperiod
~ 13 hours
Djungarian hampster (Siberia/Mongolia)
Steinlechner and Niklowitz (1992)
 Ambient temperature can interact with photoperiod to alter response
 Hampsters at room temp (22C) had a critical photoperiod ~ 13 hours
 Hampsters in cold temp (5C) had a critical photoperiod ~15 hours
 2 hour change represents a 4 week shift in seasonal acclimations due to
photoperiod
22 °C
5 °C
Djungarian hampster (Winter/Summer pelage)
Steinlechner and Niklowitz (1992)
Conservation implications
Some physiological mechanisms that govern species biology may be
maladaptive in the face of rapid climate change
 The signal for a hare to shift coat color comes from the pineal gland in
the brain that senses changes in daylight length.
Shortening days of autumn trigger the coat color change from brown to
white.
Earlier winters and springs may be resulting in hares that change color at
the wrong time (white hairs on brown dirt or brown hares on snow)
The Tatra mountain ibex (Capra ibex ibex) in Czechoslovakia had gone extinct
Subsequent reintroduction of ibex from nearby Austria was successful.
However, later supplementation of the Tatra herd with individuals from
Turkey and Sinai resulted in fertile hybrids which rutted in autumn rather than
in winter as the native ibex did.