Transcript Connecting eastern monarch population dynamics across their

Connecting eastern monarch population
dynamics across their migratory cycle
Leslie Ries, Univ. of MD
Karen Oberhauser, Univ. of MN
Elise Zipkin, USGS (Patuxent)
Doug Taron, IL BMS
Eduardo Rendon, WWF-Mexico
Monarchs have a complex migratory cycle that
makes tracking population dynamics challenging
Stage 3: Summer
expansion and breeding
Stage 2:
Spring migration
and breeding
Stage 1:
Overwintering
Stage 4:
Fall migration
• Dynamics in one
stage have carry-over
effects into
subsequent stages
• On the other hand,
it is largely one
population, rather
than a series of
loosely connected
“sub” populations
Understanding monarch population
dynamics is critical for their conservation
• Notable patterns:
– Eastern monarchs may be declining,
but examining different life stages
suggests different patterns
– Monarch populations show large
fluctuations from year to year
SUMMER MONITORING DATA
• Underlying mechanisms
– REGIONAL CONNECTIONS: How do
dynamics in one phase of the
migratory cycle influence dynamics
in subsequent phases?
– ENVIRONMENTAL INFLUENCE: How
much do environmental factors
influence the connection between
these phases?
FALL MONITORING DATA
WINTER MONITORING DATA
How can we track dynamics through each
life stage?
Monarch
Health
started ‘99
Gen 3/4 adults
N. American
Bfly Assoc.
started 1975
Ohio BMS
started ’96
Gen 2 adults
Illinois BMS
started ’87
Florida BMS
started ’03
Gen 3/4 eggs
Monarch Larvae
Monitoring
Project
started ‘99
Gen 2 eggs
Expansion
Gen 1 adults
Gen 1 eggs
Journey North
started ‘99
Migrants
going north
Adults arriving in Mexico
Surviving overwinter adults
Cape May
Roosts
started ‘92
Migrants
going south
Journey South
started ’99
Monarch Watch
started ’92
Peninsula Point
Roosts
started ‘96
WWF-Mexico
•started ’96
•started tracking overwinter
mortality in 2003
Data Available for Analysis
Monarch Larvae Monitoring
Project (MLMP)
North American Butterfly
Association Counts (NABA)
Ohio Butterfly Monitoring
Scheme (OH)
Illinois Butterfly Monitoring
Scheme (IL)
•Cape May (CM)
•WWF-Mexico (MEX)
•(’95 winter start; ‘04
winter end)
Mexican sites
Data Available for Analysis
N-East
Monarch Larvae Monitoring
Project (MLMP)
North American Butterfly
Association Counts (NABA)
N-Central
South
Mexican sites
Ohio Butterfly Monitoring
Scheme (OH)
•Cape May (CM)
•WWF-Mexico (MEX)
•(’95 winter start; ‘04
winter end)
Tracking the population through each region and stage
1. Do the number of adults surviving
the winter in Mexico relate to the
number of adults arriving in the
Texas area in spring?
2. Do the number of spring arriving
adults relate to the number of 1st
gen eggs that are recorded?
Mexican sites
Tracking the population through each region and stage
1. Do the number of adults surviving
the winter in Mexico relate to the
number of adults arriving in the
Texas area in spring?
2. Do the number of spring arriving
adults relate to the number of 1st
gen eggs that are recorded?
3. How do the number of spring adults
or eggs relate to the number of 1st
generation arrivals in the northern
regions?
Mexican sites
Tracking the population through each region and stage
1. Do the number of adults surviving
the winter in Mexico relate to the
number of adults arriving in the
Texas area in spring?
2. Do the number of spring arriving
adults relate to the number of 1st
gen eggs that are recorded?
3. How do the number of spring adults
or eggs relate to the number of 1st
generation arrivals in the northern
regions?
4. Can the number of 1st generation
adults / 2nd generation eggs predict
numbers in subsequent
generations?
Mexican sites
Tracking the population through each region and stage
1. Do the number of adults surviving
the winter in Mexico relate to the
number of adults arriving in the
Texas area in spring?
2. Do the number of spring arriving
adults relate to the number of 1st
gen eggs that are recorded?
3. How do the number of spring adults
or eggs relate to the number of 1st
generation arrivals in the northern
regions?
4. Can the number of 1st generation
adults / 2nd generation eggs predict
numbers in subsequent
generations?
5. Can the size of the population at the
last stages of the breeding cycle
predict the number of fall migrants?
Mexican sites
Tracking the population through each region and stage
Mexican sites
1. Do the number of adults surviving
the winter in Mexico relate to the
number of adults arriving in the
Texas area in spring?
2. Do the number of spring arriving
adults relate to the number of 1st
gen eggs that are recorded?
3. How do the number of spring adults
or eggs relate to the number of 1st
generation arrivals in the northern
regions?
4. Can the number of 1st generation
adults / 2nd generation eggs predict
numbers in subsequent
generations?
5. Can the size of the population at the
last stages of the breeding cycle
predict the number of fall migrants?
6. Can the size of the population at the
last stages of the breeding cycle
predict the number of Mexican
arrivals?
Mexican migrants and spring adults
r=0.5 p=0.25
2.5
MLMP egg density (South)
NABA detections (spr – South)
Q1 and Q2. How do overwintering numbers relate to the number of
arriving adults and how do arriving adults influence the number of
eggs we see in the spring?
2
1.5
1
0.5
0
0
1
2
3
4
5
6
7
MEX – monarch area covered (ha)
Spring adults and spring eggs
r=0.34 p=0.51
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0.5
1
1.5
2
NABA detections (South)
2.5
A non-existent (or weak) relationship between the number of adults leaving Mexico and
the number arriving in Texas and surrounding areas in the spring. And no hint of a
relationship between spring adults and eggs. But there are few data available to
rigorously make these comparisons!!
Q3. How do the number of spring adults or eggs relate to the number of
1st generation arrivals in the northern regions?
NOTE: There are eight combinations of comparisons here, none show
significant relationships (the strongest patterns are shown below).
1st gen eggs in south to 2nd gen eggs North
r=0.5 p=0.13
NABA 1st Gen adults (N-East)
2nd gen MLMP egg density (N-Central)
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1
2
1st gen MLMP egg density (South)
Migrant adults in south to 1st gen adult arrivals
3
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
r=0.69 p=0.12
0
0.5
1
1.5
2
NABA spring migrants (South)
A weak, or non-existent, relationship between the spring generation and summer
arrivals in the north could be due to lack of data, or swamping out by environmental
factors.
2.5
4
3
2
1
0
0.001
N-Central:
Summer MLMP egg dens (N-Central)
Summer MLMP egg density (N-East)
5
0.6
0.01
0.1
2nd gen MLMP egg density (N-East)
1
r=0.7925 p=<0.0001
0.5
0.4
0.3
0.2
0.1
0
0.01
0.1
2nd gen MLMP egg density (N-Central)
1
Summer NABA detections (N-Central)
Summer NABA detections (N-East)
Q3. Can the number of 1st generation adults / 2nd generation eggs predict numbers in
subsequent generations?
6
0.8
N-East:
r=0.899 p=<0.0001
r=0.85 p=0.004
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.001
8
0.01
0.1
2nd gen MLMP egg density (N-East)
1
r=0.73 p=0.005
7
6
5
4
3
2
1
0
0
1
2
1st Gen Spring arrivals NABA (N-Central)
YES: This suggests that the number of arrivals in the northern breeding grounds from the
southern spring generation has a strong influence on the ultimate size of that year’s
population.
3
Tracking climate’s impacts on the
migratory monarch butterfly
a)
center of
summer
recruitment
b)
Years of data
1-4
5-9
10-13
Overwintering site
We examined the impacts on
population growth in Ohio of:
1. Spring temperature (in
Texas)
2. Spring precipitation (in
Texas)
3. Summer temperature (in
Ohio)
4. Summer precipitation (in
Ohio)
26-28)
(weekssize
monarchs/hr
Mean number
(Ohio)
population
peak
Summer
Patterns based on simple climate
metrics aren’t informative
a)
18
16
14
12
10
8
6
4
2
0
500
20
550
600
650
700
750
GDD (weeks
4-9) in Texas)
SpringTexas
temperature
(GDD
c)
18
b)
16
14
12
10
8
6
4
2
0
800 1500
1700
1900
2100
2300
2500
GDD (weeks(GDD
10-28)in Ohio)
SummerOhio
temperature
20
15
15
10
10
5
5
0
0
0
2
4
6
8
10
rainfall (cm)
Spring Texas
precipitation
(Texas)
12
d)
-4
-2
0
2
4
Ohio PDI (through week 28)
Summer drought index (Ohio)
6
Meaningful patterns emerge when patterns are
evaluated in a multiple regression framework, taking
site characteristics into account
20
1.0
15
0.5
1
6
0
4
-1
Summer GDD in OH (standardized)
Standardized summer GDD in Ohio
a)
GDDdiff (standardized)
8
1.5
-0.5
5
-1.0
0
10
15
b)
20
25
6
Week
1.0
5
0.5
4
Location with min average GDD
-3
3 10
25
10
8
1
6
0
4
-1
-3
3
3
20
week
-2
0.0
0
15
2
GDDdiff (standardized)
10
2
Coolest sites
-2
0.0
1.5
10
2
2
Avg site
Location with mean average GDD
0
10
15
20
25
10
week
2
-0.5
2
-1.0
1
-1.5
0
10
15
20
GDDdiff (standardized)
Springin
GDD
TX
(standardized)
Spring Precipitation
in
TX (standardized)
spring
in TX
(standardized)
in TXPrecip
(cm)
(standardized)
TXinspring
precipitation
Spring GDD
SpringStandardized
GDD in TX
Standardized
3
8
1
6
0
4
-1
25
Week
Week
Zipkin et al. (in press): Global Change Biology
-2
2
Warmest sites
Location with max average GDD
-3
0
10
Week
15
20
25
The story so far…
• No relationship between adults leaving
Mexico, arriving in the South, and laying eggs
• Weak (or non-existent) relationship between
adults arriving in the South, next generation
arrivals in the North and egg-laying
•The disconnect may be due to the
importance of spring climate on the
ultimate population size (and/or health) of
migrants to the North
• A strong relationship between the numbers
arriving in the North and laying eggs and the
size of the population at the end of the summer.
•This suggests that the size of that first
generation produced in the spring that
arrives in the North is an important
contributor to yearly population sizes and
(again) that spring climate is important
Next up: Population connections on the return trip
Q5. Can the size of the population at the last stages
of the breeding cycle predict the number of fall
migrants?
120
r=0.61 p=0.005
Cape May Roost Size
100
80
60
40
20
0
0
2
4
6
N-east summer adult population (NABA detections)
20
18
16
14
12
10
8
6
4
2
0
r=0.00 p=0.99
0
2
4
6
N-east summer adult population (NABA detections)
Overwinter colony size in Nov (ha)
Overwinter colony size in Nov (ha)
Q6. Can the size of the population at the last
stages of the breeding cycle predict the
number of Mexican arrivals?
20
18
16
14
12
10
8
6
4
2
0
r=-0.01 p=0.69
0
2
4
6
8
N-central summer adult population (NABA detections)
NO? This lack of relationship is surprising given results of past (admittedly
smaller) analyses, and deserves further examination.
Conclusions and future directions
• Growth during the summer breeding season is the most important
factor driving yearly population sizes
– The number (or health) of migrants arriving from the southern US into the north
is a key driver of population growth and this may be driven by climate
– Summer climate also influences summer growth
• There seems to be little congruence between winter colony size and
the spring and summer detection rates from butterfly surveys
– Loss of milkweed (not captured by surveys) may be influencing winter, but not
summer, values (Pleasants and Oberhauser, in press)
• We will continue to develop this “regional connections” framework
– Include data from other programs
– Repeat analyses as data resources grow
– Continue to develop mechanistic models that explore environmental impacts on
specific stages or linkages
Acknowledgements
• All members of
MonarchNet
• NCEAS monarch
working group
• Program coordinators
and the thousands of
volunteers!!!
• Funding:
Monarch Joint Venture
CEC
SESYNC
Results: Winter counts are related to the
previous summer (but not vice-versa)
Gen 2-4
adults
Gen 2-4
adults
3.5
3.5
3
2.5
2
Illinois
1.5
Ohio
1
4-Jul
Linear (Ohio)
0.5
Linear (Illinois)
LN (Following Summer Counts)
ln (Following Winter Mexican Counts +
1)
Overwintering adults
Overwintering adults
3
2.5
2
1.5
Illinois
1
Ohio
0.5
4-Jul
0
0
0
0.5
1
1.5
2
ln (Previous Summer Counts + 1)
Illinois: r = 0.72, p = 0.005
Ohio: r = 0.80, p = 0.009
4July: r = 0.38, p = 0.21*
2.5
3
0
0.5
1
1.5
2
2.5
ln (Previous Winter Mexican Counts)
Illinois: r = 0.13, p = 0.68
Ohio: r = 0.08, p = 0.83
4July: r = 0.17, p = 0.60
*Data can be expanded to their full range and for the full 30 years of winter data
3
3.5
Two main questions
Stage 3: Summer
expansion and breeding
Stage 2:
Spring migration
and breeding
Stage 1:
Overwintering
Stage 4:
Fall migration
•REGIONAL CONNECTIONS
ANALYSIS: How do dynamics
in one phase of the
migratory cycle influence
dynamics in subsequent
phases?
• CLIMATE ANALYSIS: How
much do environmental
factors influence the
connection between these
phases?
Monarch Net:
A network of monarch monitoring groups
For more information, see monarchnet.org and the Butterfly Monitoring Poster
How can we track dynamics through each
life stage?
N. American
Bfly Assoc.
started 1975
Gen 3/4 adults
Gen 3/4 eggs
Monarch Larvae
Monitoring
Project
started ‘99
Gen 2 adults
Gen 2 eggs
Expansion
Cape May
Roosts
started ‘92
Gen 1 adults
Gen 1 eggs
Migrants
going south
Migrants
going north
Adults arriving in Mexico
Surviving overwinter adults
WWF-Mexico
•started ’96
•started tracking overwinter
mortality in 2005