monarchs in southern spain - monarch joint venture · 1. [email protected] 2. [email protected] 3....
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Monarch butterflies in southern SpainPatch dynamics and persistence
During the ninetieth century the Monarch butterfly spread across the PacificOcean. At the same time, migrants crossing the Atlantic Ocean were seen for thefirst time in several European countries (Fig. 1). Breeding populations onlyestablished in the islands. During the 1980s some small breeding colonies werefound along the coast of Spain. However, these were ephemeral.
J. Fernández Haeger1, D. Jordano2 & M. Zalucki3
1,2. University of Córdoba, Spain.3. University of Queensland. Brisbane, Australia.
1. [email protected] 2. [email protected] 3. [email protected]
Since 1997 we have regularly recorded monarch butterflies along thesouthernmost coastal area in Europe (36o N). Part of this area is within theAlcornocales Natural Park and also the Natural Park of the Gibraltar straits.
OBJECTIVES
The aim of the study was to inventory suitable breeding habitats for the monarchbutterfly and to assess its status in the study area.
METHODS
Starting in June 2008, we systematically surveyed a coastal area of 900 km2 closeto the Gibraltar strait (Fig. 2). We located 62 milkweed patches, which were visitedon a regular basis over 30 months. We searched for adults, eggs, larvae andpupae, thus determining whether the patch was occupied or empty.
RESULTS
Fig. 2 Distribution of the 62 host plant patches in the study area. Gomphocarpusfruticosus is more abundant and widespread than Asclepias curassavica; G.physocarpus is scarce and restricted to just 2 patches.
Table 1 Butterflies and immature stages recorded during 1945 visits to patches.
HOST PLANT
STAGE A. curassavica G. fruticosus TOTAL
No. EGGS 2964 815 3779
No. LARVAE 2294 2005 4299
No. PUPAE 378 250 628
No. BUTTERFLIES 3095
Maximum patch occupation rangedfrom 50 to 65 % among years (Fig. 6).
0
10
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40
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60
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100M
on
thly
Occ
up
ancy
(%
)
Patches
PatchesOccupied: 47Unnocupied: 15
5 10 15 20 25 30 35 40 45 50 55 6260
0
10
20
30
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70
2008 2009 2010 2011
No
. of
Pat
che
s
Year
Vacant Occupied
0102030405060708090
100
3 4 1 2 3 4 1 2 3 4
2008 2009 2010
Pat
ch O
ccu
pan
cy (
%)
Quarter & Year
Fig. 8. Variation of patch occupation among years
0
100
200
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700
6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 12
2008 2009 2010 2011 2012
No
. o
f In
div
idu
als
Month and Year
Monarch butterflies
Inmature stages
2523
In the study area the Monarch is multivoltine with no diapause, breedingthroughout the year. We recorded immature stages in 65.5 % of field-workdays, even during winter. In the last five years there were two major populationoutbreaks, leading to severe patch defoliation (Fig. 4, see pictures at the top).
Fig. 1. Early citations of Monarch butterflies in European countries.
Patch occupation also showed strongseasonal variation, peaking in late summerand early autumn (Fig. 7)
CONCLUSIONS
There were huge differences in butterfly and immature abundance among patches and amongmonths and years. While a few patches make a large contribution to the population, othersseem to be sinks. Good patches are located next to permanent streams in riparianhabitat, where microclimate and shelter from the strong easterly wind provide more suitableconditions during the summer drought.
The monarch population persists at the regional scale, but local extinctions and recolonizationswere frequent events. Local extinctions were mainly driven by flooding, severe host plantdamage by frost, complete patch defoliation by caterpillars (see pictures at the top), diversion ofthe water supply and vegetation clearings.
Spain
The presence of butterflies and/or immatures in each patch was not constant.Only 4 patches were occupied over ninety percent of months (Fig. 5).
Fig. 3 Patch occupation by monarchs butterflies. Occupied patches were thosewhere the species was recorded at least once during the 2008-2011 period.