How well do
first flowering
dates measure
plant
responses to
climate
change?
Abraham MillerRushing,
David Inouye, and
Richard Primack
Why phenology?
22 June 1917
17 May 2005
Miller-Rushing et al. 2006. American Journal of Botany.
Why phenology?
• Earlier springs
• Changing
relationships
English Oak
Quercus robur
EARLIER
From Both et al.
2006. Nature.
English Oak
Quercus robur
EARLIER
Winter Moth
Operophtera brumata
EARLIER
From Both et al.
2006. Nature.
English Oak
Quercus robur
EARLIER
Winter Moth
Operophtera brumata
EARLIER
Pied Flycatcher
Ficedula hypoleuca
SAME TIME EACH
YEAR
From Both et al.
2006. Nature.
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ed
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Days earlier per 1 oC warming
Variation among species
8
6
4
2
0
Miller-Rushing and Primack. 2008. Ecology. &
Miller-Rushing et al. in press. Global Change Biology.
Earlier spring
First flowering dates:
• ~1900 – July 8
• ~2005 – June 19
Crown vetch
Coronilla varia
Miller-Rushing and Primack. 2008. Ecology.
Earlier spring
Dwarf larkspur
Delphinium nuttalianum
Inouye and McGuire. 1991. American Journal of Botany.
Later spring?
First flowering dates:
• ~1900 – May 18
• ~2005 – May 29
Bastard toadflax
Comandra umbellata
Miller-Rushing and Primack. 2008. Ecology.
What is really going on?
Concord, Massachusetts
• 1850—2006
• First flowering dates
• Population sizes
• Across entire town
Concord, Massachusetts
• Ð population sizes: 7 days later
• ÍÎ population sizes: 5 days
earlier
• Ï population sizes: 12 days earlier
Miller-Rushing et al. in review.
Concord, Massachusetts
Gothic, Colorado
• 1973—2007
• Flowering
distribution
• Number of flowers
• Fixed plots
Gothic, Colorado
Miller-Rushing et al. in review.
Why different between
locations?
• Fixed developmental
schedule of montane
plants
• Fixed spatial
sampling
Dwarf bluebells
Mertensia fusiformis
Sampling effort
Sampling effort
Ï sampling effort
• Expands distribution
• Increases probability
of detecting changes
• Can alter estimates of
change
Miller-Rushing et al. in review.
Conclusions
• Measure entire
distribution when
possible
• Consider effects of
population size and
sampling effort
Mariposa lily
Calochortus gunnisonii
• Past results may
need to be
reinterpreted