Post on 23-Feb-2016
description
Connecting eastern monarch population dynamics across their migratory cycle
Leslie Ries, Univ. of MDKaren 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 1: Overwintering
Stage 2: Spring migration and breeding
Stage 3: Summer expansion and breeding
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
• 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?
SUMMER MONITORING DATA
FALL MONITORING DATA
WINTER MONITORING DATA
How can we track dynamics through each life stage?
Surviving overwinter adults
Gen 3/4 eggs
Gen 2 adultsGen 2 eggs
Gen 1 eggs
Gen 1 adults
Gen 3/4 adults
Migrants going south
Adults arriving in Mexico
Journey Northstarted ‘99
Monarch Larvae Monitoring
Projectstarted ‘99
Migrants going north
Cape May Roosts
started ‘92
WWF-Mexico• started ’96
• started tracking overwinter mortality in 2003
N. American Bfly Assoc.
started 1975Ohio BMSstarted ’96
Journey Southstarted ’99
Monarch Watchstarted ’92
Peninsula Point Roosts
started ‘96
Monarch Health
started ‘99
Illinois BMSstarted ’87
Florida BMSstarted ’03
Expansion
Data Available for Analysis
•Cape May (CM)•WWF-Mexico (MEX)•(’95 winter start; ‘04 winter end)
Monarch Larvae Monitoring Project (MLMP)
North American Butterfly Association Counts (NABA)
Illinois Butterfly Monitoring Scheme (IL)
Ohio Butterfly Monitoring Scheme (OH)
Mexican sites
Data Available for Analysis
Monarch Larvae Monitoring Project (MLMP)
North American Butterfly Association Counts (NABA)
Mexican sites
South
N-Central
N-East
•Cape May (CM)•WWF-Mexico (MEX)•(’95 winter start; ‘04 winter end)
Ohio Butterfly Monitoring Scheme (OH)
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
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?
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?
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?
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?
Tracking the population through each region and stage
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?
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!!
0 1 2 3 4 5 6 70
0.5
1
1.5
2
2.5
MEX – monarch area covered (ha)
NAB
A de
tecti
ons (
spr –
Sou
th)
Mexican migrants and spring adults
0 0.5 1 1.5 2 2.50
0.20.40.60.8
11.21.41.61.8
2
NABA detections (South)
MLM
P eg
g de
nsity
(Sou
th)
Spring adults and spring eggsr=0.5 p=0.25 r=0.34 p=0.51
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3
2nd
gen
MLM
P eg
g de
nsity
(N-C
entr
al)
1st gen MLMP egg density (South)
00.20.40.60.8
11.21.41.61.8
2
0 0.5 1 1.5 2 2.5N
ABA
1st G
en ad
ults
(N-E
ast)
NABA spring migrants (South)
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).
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.
1st gen eggs in south to 2nd gen eggs North Migrant adults in south to 1st gen adult arrivals
r=0.5 p=0.13 r=0.69 p=0.12
0
1
2
3
4
5
6
7
8
0 1 2 3
Sum
mer
NAB
A de
tecti
ons (
N-C
entr
al)
1st Gen Spring arrivals NABA (N-Central)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.01 0.1 1
Sum
mer
MLM
P eg
g den
s (N
-Cen
tral
)
2nd gen MLMP egg density (N-Central)
Q3. Can the number of 1st generation adults / 2nd generation eggs predict numbers in subsequent generations?
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.
0
1
2
3
4
5
6
0.001 0.01 0.1 1Su
mm
er N
ABA
dete
ction
s (N
-Eas
t)2nd gen MLMP egg density (N-East)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.001 0.01 0.1 1
Sum
mer
MLM
P eg
g den
sity
(N-E
ast)
2nd gen MLMP egg density (N-East)
N-East: r=0.899 p=<0.0001 r=0.85 p=0.004
r=0.7925 p=<0.0001 r=0.73 p=0.005
N-Central:
Tracking climate’s impacts on the migratory monarch butterfly
Overwintering site
Approximate limit of breeding
center of summer recruitment
a)
b)
Years of data1-4
5-910-13
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)
Patterns based on simple climate metrics aren’t informative
2 3 4 5 6 7 8 9 10 11 120
5
10
15
20
Texas rainfall (cm)
500 550 600 650 700 750 80002468
1012141618
Texas GDD (weeks 4-9)
1500 1700 1900 2100 2300 250002468
1012141618
Ohio GDD (weeks 10-28)
-4 -3 -2 -1 0 1 2 3 4 50
5
10
15
20
Ohio PDI (through week 28)
Mea
n nu
mbe
r mon
arch
s/hr
(wee
ks 2
6-28
)
a) b)
c) d)
Spring precipitation (Texas)
Spring temperature (GDD in Texas) Summer temperature (GDD in Ohio)
Summer drought index (Ohio)
Sum
mer
pea
k po
pula
tion
size
(Ohi
o)
Meaningful patterns emerge when patterns are evaluated in a multiple regression framework, taking
site characteristics into account
0
5
10
15
20
10 15 20 25
-1.0
-0.5
0.0
0.5
1.0
1.5
Week
Spr
ing
Pre
cipi
tatio
n in
TX
(sta
ndar
dize
d)
0
1
2
3
4
5
6
10 15 20 25
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Week
Spr
ing
GD
D in
TX
(sta
ndar
dize
d)
b)
a)
Sprin
g GD
D in
TX
(sta
ndar
dize
d)
Week
0
2
4
6
8
10
10 15 20 25
-3
-2
-1
0
1
2
3
week
GD
Ddi
ff (s
tand
ardi
zed)
Location with min average GDD
0
2
4
6
8
10
10 15 20 25
-3
-2
-1
0
1
2
3
week
GD
Ddi
ff (s
tand
ardi
zed)
Location with mean average GDD
0
2
4
6
8
10
10 15 20 25
-3
-2
-1
0
1
2
3
week
GD
Ddi
ff (s
tand
ardi
zed)
Location with max average GDD
Sum
mer
GDD
in O
H (s
tand
ardi
zed)
Sprin
g pr
ecip
itatio
n (c
m) i
n TX
(sta
ndar
dize
d)
Week
Coolest sites
Avg site
Warmest sitesSt
anda
rdize
d su
mm
er G
DD in
Ohi
o
Stan
dard
ized
sprin
g GD
D in
TX
Stan
dard
ized
sprin
g Pr
ecip
in T
X
Zipkin et al. (in press): Global Change Biology
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
0 1 2 3 4 5 60
20
40
60
80
100
120
N-east summer adult population (NABA detections)
Cape
May
Roo
st S
ize
Q5. Can the size of the population at the last stages of the breeding cycle predict the number of fall migrants?
r=0.61 p=0.005
02468
101214161820
0 2 4 6
Ove
rwin
ter c
olon
y size
in N
ov (h
a)
N-east summer adult population (NABA detections)
02468
101214161820
0 2 4 6 8
Ove
rwin
ter c
olon
y size
in N
ov (h
a)
N-central summer adult population (NABA detections)
Q6. Can the size of the population at the last stages of the breeding cycle predict the number of Mexican arrivals?
r=0.00 p=0.99 r=-0.01 p=0.69
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 VentureCECSESYNC
Results: Winter counts are related to the previous summer (but not vice-versa)
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3
ln (Previous Summer Counts + 1)
ln (F
ollo
win
g W
inte
r Mex
ican
Cou
nts
+ 1) Illinois
Ohio
4-Jul
Linear (Ohio)
Linear (Illinois)0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3 3.5
ln (Previous Winter Mexican Counts)
LN (F
ollo
win
g Su
mm
er C
ount
s)
Illinois
Ohio
4-Jul
Illinois: r = 0.72, p = 0.005Ohio: r = 0.80, p = 0.0094July: r = 0.38, p = 0.21*
Illinois: r = 0.13, p = 0.68Ohio: r = 0.08, p = 0.834July: r = 0.17, p = 0.60
*Data can be expanded to their full range and for the full 30 years of winter data
Gen 2-4 adults
Overwintering adults
Gen 2-4 adults
Overwintering adults
Two main questions
Stage 1: Overwintering
Stage 2: Spring migration and breeding
Stage 3: Summer expansion and breeding
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?
Surviving overwinter adults
Gen 3/4 eggs
Gen 2 adultsGen 2 eggs
Gen 1 eggs
Gen 1 adults
Gen 3/4 adults
Migrants going south
Adults arriving in Mexico
Monarch Larvae Monitoring
Projectstarted ‘99
Migrants going north
Cape May Roosts
started ‘92
WWF-Mexico• started ’96
• started tracking overwinter mortality in 2005
N. American Bfly Assoc.
started 1975
Expansion