use of space and resources in a mediterranean population of the butterfly euphydryas aurinia

8/3/2019 Use of Space and Resources in a Mediterranean Population of the Butterfly Euphydryas Aurinia

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Acta (Ecologica, 1997 , 18 (5 ) , 597 -612

U s e o f s p a c e a n d r e s o u r c e s in a M e d i t e r r a n e a n p o p u l a t i o no f t h e b u t t e r f ly Euphydryas aurinia

M igue l L. M ungu ira , Jos6 Mart fn , Enrique G arcfa-Barros and Jos6 Lu is ViejoDepartamento de Biologia (Zoologia), Facultad de Ciencias, Universidad Aut6nom a de M adrid, Cantoblanco,E-28049-Madrid, Spain.E-mail: [email protected]

R e c e i v e d : 1 7 . 1 1 . 9 6 A c c e p t e d : 1 8 . 4 . 9 7

Abs t rac tP o p u l a t i o n p a r a m e t e r s o f a c e n t r a l S p a n i s h p o p u l a t i o n o f t h e m a r s h f r it i ll a r y b u t te r f ly , Euphy-dryas aurinia ( R o t t. ) , w e r e s t u d i e d b e t w e e n 1 9 9 0 a n d 1 9 9 1 . N u m b e r s w e r e v e r y s i m i l a r i n t h e t w o

s t u d y y e a r s , b u t a d u l t e m e r g e n c e w a s d e l a y e d 1 5 d a y s i n t h e s e c o n d y e a r a s a c o n s e q u e n c e o f v a r ia t i o ni n w e a t h e r c o n d i t i o n s .

T h e n e c t a r s o u r c e s u s e d b y a d u l t s w e r e d i f f e re n t i n th e t w o y e a r s a n d w e r e c o r r e l a t ed w i t h t h em o s t a b u n d a n t p l a n t s a v a il a b l e d u r i n g t h e f l i g h t p e ri o d . A d u l t a b u n d a n c e w a s c o r r e la t e d w i t h t h e p r e -s e n c e o f t h e l a rv a l f o o d p l a n t (Lonicera periclymenum) i n o p e n w o o d l a n d a n d w a s h i g h e r w h e r e t h ish a b i t a t w a s m i x e d w i t h o p e n a r e a s , w h e r e n e c t a r s o u r c e s a b o u n d .

E s t i m a t e s o f m a l e p o p u l at i o n n u m b e r s w e r e h i g h e r t h a n t h o s e o f f e m a l e s , s u g g e s t i n g t h a t m a l e su s e d w i d e r r a n g e s t h a n f e m a l e s , o r a h i g h e r r e s i d e n c e r at e f o r m a l e s . N e v e r t h e l e s s m o b i l i t y d i d n o td i f f er s i g n i f i c a n t l y b e t w e e n t h e s e x e s .

T h e c o n s e r v a t i o n o f t h e s p e c ie s i n ce n t r a l S p a in d e p e n d s o n m a i n t a i n i n g p a t c h e s o f o a k w o o d -l a n d s , i m p o r t a n t f o r t h e p r e s e n c e o f la r v a l f o o d p l a n t s . L a r g e n u m b e r s o f t h e b u t te r f l y i n th e N a t u r a lP a r k s t u d y a r e a a r e f a v o u r e d b y t ra d i t io n a l m a n a g e m e n t i n c l u d i n g c h a r c o a l p r o d u c t i o n a n d e x t e n s i v eg r a z i n g b y c a t tl e a n d g o a t s .

Keywords: L e p i d o p t e r a , N y m p b a l i d a e , p o p u l a t i o n e s t i m a t e s , r e s o u r c e u s e , s p a t i a l d i s t r i b u t i o n , c o n -s e r v a t i o n .

R~sum~N o u s a v o n s ~ t u di 6 , e n t r e 1 9 9 0 e t 1 9 9 1 , d i ff ~ r e n t s p a r a m ~ t r e s d ' u n e p o p u l a t i o n d u p a p i l l o nEuphydryas aurinia ( R o t t. ) d u c e n t r e d e l ' E s p a g n e . L e n o m b r e d e p a p i l l o n s e s t tr E s s i m i l a i r e d ' u n e

a n n 6 e ~ l' a u t r e , m a i s l ' ~ m e r g e n c e d e s a d u l t e s a e u l i e u 1 5 j o u r s p l u s t a rd l a s e c o n d e a n n i e , e n r a i s o nd ' u n e v a r i a t i on d e s c o n d i t i o n s c l i m a t i q u e s .

L e s s o u r c e s d e n e c t a r u t i li s 6 e s p a r l e s a d u l t e s s o n t d i f f 6 r e n te s s e l o n l e s a r m i e s e t s o n t c o r r~ l ~ e sa u x p l a n t e s l e s p l u s a b o n d a m m e n t d i s p o n i b l e s a u c o u r s d e l a p 6r i o d e d e v o l . L ' a b o n d a n c e d e s a d u l t e se s t c o r r ~ l ~ e ~ la p r 6 s e n c e d e l a p l a n t e n o u r r i c i ~ r e d e s I a r v e s (Lonicera perictymenum) d a n s l e s b o i so u v e r t s e t e s t p l u s i m p o r t a n t e l o r s q u ' ~ c e t h a b i t a t s e m ~ l e n t d e s z o n e s o u v e r t e s o O a b o n d e n t l e s s o u r -c e s d e n e c t a r .

L e s e s t i m a t i o n s d e n o m b r e s s o n t p l u s 6 1e v 6e s p o u r l a p o p u l a t i o n m a l e q u e p o u r l a p o p u l a t i o nf e m e l l e , c e q u i s u g g b r e q u e l e s m a l e s u t i l is e n t u n e s p a c e p l u s g r a n d q u e l e s f e m e l l e s , o u q u ' i l s o n t u nt a u x d e r e s i d e n c e p l u s 6 1e v6 . C e p e n d a n t l a m o b i l i t6 n e d i f f er e p a s s i g n i f i c a t i v e m e n t e n t r e l e s s e x e s .

Acta (Ecologica 1 1 4 6 - 6 0 9 X / 9 7 1 0 5 / 9 E l s e v i e r , P a r i s


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5 9 8 M . L . M u n g u i ra et aL

L a c o n s e r v a t i o n d e t ' e s p r c e d a n s l e c e n tr e d e t 'E s p a g n e d r p e n d d u m a i n t ie n d e b o s q u e t s d e c h i -n e s , i m p o r t a n t s p o u r l a p r r s e n c e d e l a p l a n t e n o u r r i c i ~ r e d e s l a r v e s . D a n s l a z o n e d ' r t u d e d u P a r cN a t i o n a l , u n e g e s t i o n t r a d i t io n n e l l e in c l u a n t l a p r o d u c t i o n d e c h a r b o n d e b o i s e t u n p ~ t u r a g e e x t e n s i fp a r l e s b o v i n s e t l e s c a p r i n s f a v o r is e la p r r s e n c e e n g r a n d h o m b r e d e c e p a p i l l o n .

INTRODUCTIONSome species of the genus E u p h y d r y a s Scudder are well known by ecologists andevolutionary biologists after three decades of research by Paul R. Ern~icH and co-workers (E~tRLICHet al . , 1975). Studies have focused mainly on the American speciesE. edi tha (Boisduval) and have covered aspects such as population dynamics, adultand larval resources, use of space and other relevant ecological traits. The best knownresults concern the great variability of the use of resources among and within popu-lations (EI-n~xcHet al . , 1975) and the fluctuations in adult numbers causing local

extinctions and occasional recolonizations in vacant habitat patches (EHRLICHet al . ,1980; ErmLiCrt & Mtmpnv, 1981). Some of the American populations of E. edi tha havebeen proposed as a typical example of the mainland-island metapopulation constella-tion (Wmcox & Mt;~Hv, 1985; HARRISONet al., 1988). The research on E u p h y d r y a spopulations has contributed to the development of the metapopulation theory and itsimplications in conservation practice (THOMAS & HARRISON, 1992; WARREN, 1994).In Europe, the genus Eu p h yd r ya s ( s en s u s t ri c tu ) is represented by the E. aurin ia(Rottemburg) species complex (with several species or subspecies depending on sys-tematics) and E. desfontaini i (Godart). The boreal and alpine species of the closelyrelated genus H yp o d r ya s ( s en s u HIGGINS & HARGREAVES, 1983) are considered bysome authors as members of the genus E u p h y d r y a s (KtmRNA, 1986). Most of the

available ecological information comes from the nominal subspecies E. a. aurinia,that lives in central Europe and the British Isles (SBN, 1987; WARREN, 1990, 1994),and whose ecology has been studied with some detail since 1930 (FORD & FORD,1930). The species had declined dramatically in some European areas. For examplein The Netherlands it declined continuously since the beginning of this century, andthe last population became extinct around 1983 (VAN SWAAY, 1990). Similar declinesin Eu p h yd r ya s ed i t h a b a yen s i s were observed in California (USA) where more thana dozen populations have been reduced to only two remnant populations (MURPHY &WEISS, 1988). The protection of E. aurin ia in European countries through the BernConvention and the Habitats Directive (FERNANDEZ-GALIANO, 1992; VIEJOe t aL , 1990)has produced a high demand of information for the species, in order to make soundrecommendations towards its conservation. There have been three main reasons forthe present study of E. aurin ia in Spain: i) the lack of knowledge of the species inMediterranean countries, ii) Spain represents the south-western limit to its distributionrange and its ecology is different from elsewhere in Europe, and iii) while the speciesis declining in central and northern Europe, its populations are abundant in our area(WARRENe t aL, 1994) and represent an important stronghold for the species.

The Iberian E. aurin ia has some specific morphological features that have led toit being described asa distinct subspecies: E. a . beckeri Herrich-Sch~iffer. Some recentauthors regard becker i as a true species (KUDRNA, 1986). Differences are not only mor-phological but also ecological: its larval foodplants are a few honeysuckle species(vines of the genus Lonicera , TEMeLAOO, 1975), and no Succi sa pra t ens i s as in otherareas. The species' habitat is therefore also completely different and consists incleared Mediterranean Quercus i l ex and Q. pyrena ica woodlands ("encinares" and

Acta ~Ecologica


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R e s o u r c e u s e in Euphydryas auriniab u t t e r f l i e s 599

"melojares"), while in central and northern Europe its habitat consists of wet meadowswhere its hygro phil ous foo dpla nt lives (WARREN, 1994), or semi-n atura l, relatively drychalk grasslands in other areas ( e . g . SBN, 1987).

The present study summarizes results concerning the adult population biology,wit hin a r esearc h pro gra m that also i ncl ude s larval featur es (PEREZ-FAR1NOS, un pu b-lished data). Our aims were to study for the first time in the Iberian Penin sula popu-lation parameters s uch as popu lat ion size, dispersal rates, adult nectar use, depe nden ceon the presence of the larval foodplant and habitat use. These parameters are relativelywell known in the nominal subspecies ( a u r i n i a Rottemburg), and therefore we triedto test whether the different morphology ( i . e . adu lt size , HIGGINS & HARGREAVES,1983) and ecology (different larval foodplant and habitat) of the Iberian populationsimplies parameter differences. A further objective was to test the hypothesis ofwhether these parameters are useful to identify the adequate land uses that are neces-s~ for a successful conse rvat ion of the species.

METHODSThe study area is close to Soto del Real in the Natural Park of the Cuenca Alta del Manzanares, in

Madrid (central Spain). The site is about 4 ha in extent and is on a gentle south-facing slope. Its meanaltitude is i250 m a.s.I, and the vegetation comprises a mosaic of Qu er cu s p yr en a i ca (Pyrenean oak,"melojar") woodland with grassy clearings. The whole area is lightly grazed by goat and cattle, and theoak trees are cut periodically for charcoaI production.

The population study was made using the mark-release-recapture method (MRR) during 1990and 1991. We made three estimates per week during the whole flight period, except when weather con-ditions were unfavourable (rain, temperature below 20~ strong wind or cloud cover > 80%). Theinterval between sampling days was taken into account in the calculation of longevity figures. The areawas divided into plots of aproximately 2500 m2, that were each sampled intensively twice per day.Both grassland and woodland areas were sampled with the same intensity during the study. The butter-flies caught were each given an individual mark with a waterproof pen. Handling was reduced to aminimum and typically took less than one minute, besides the butterflies were kept in the shade whilebeing marked to avoid overheating and reduce stress. For each individual we also recorded the beha-viour when captured (according to the following categories: flying, resting, feeding, fighting, courtingand mating), area of capture, hour, sex and wing wear (using an arbitrary scale similar to that inT~OMAS, 1983: t mint, 2 slight wing damage, 3 notable wing damage, 4 severe wing damage).

Population numbers were estimated using the Jolly-Seber method (program " J O L L Y ' in KREBS,I989). Ageing was estimated by regressing wing wear on date from the beginning to the end of thesampling period, and differences between the sexes assessed using covariance analysis (e.g. GARdA-B~OS, t988).

A study of adult mobility was made using the distance between the centres of the plots where abutterfly was captured and recaptured. This distance was considered zero when the recapture tookplace in the same plot where captured. Total movements during the flight period and daily movementswere calculated for each specimen, and the averages for these figures worked out for comparisonbetween years and sexes. To estimate whether the butterflies preferred clearings or woodland habitats,the distance from the place of capture to the nearest wooded area was measured for each captured indi-vidual. Large distances from these wooded areas should be correlated with a preference for open habi-tats.

Vot. 18, n~ 5-I997


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In 1990 we detected a non-random ad ult distribution in the studied plo ts. To understand thecauses of thi s distribution, habitat parameters which seemed im portant where m easured in 1991. Theabundance of potential nectar sources was estimated by a 10 m x 1 m weekly transect in each plot, inwhich w e counted all flower-heads of plants that could be u sed by E. aurinia. We also estimated thetree cover by counting the numb er of oak trees (size > 3 m) per p lot. The number, height and size ofhoneysuckle plants (the larval foodplants) were also measured in each plot. All these habitat parame-ters were com pared in a m ultiple regression analysis with the relative abund ance of adu lts in each plot.R E S U L T SA d u l t n u m b e r e s t i m a t e s

E s t i m a t e s o b t a i n e d b y t h e " ' J O L L F ' m e t h o d a r e g i v e n i n fi g u r e 1 f o r t h e t o t a lp o p u l a t i o n a n d f i g u r e 2 f o r th e m a l e s a n d f e m a l e s s e p a r a t el y . N o t e t h a t in f i g u r e 2 t h es e x e s a re t r e a te d a s d i f f e r e n t p o p u l a t i o n s a n d t h e a d d i t io n o f b o t h e s t i m a t e s n o tn e c e s s a r i l y m a t c h e s t h e e s t im a t e i n fi g u r e 1 f o r th e s a m e d a y . W i t h t h e J o l l y - S e b e rm e t h o d t h e f ig u r e o f b u t te r f fl i e s a d d e d e a c h d a y t o t h e p o p u l a t i o n c a n a l s o b eo b t a i n e d . W e c a n e s t i m a t e t h e t o ta l a d u l t n u m b e r i n a p o p u l a t i o n b y a d d i n g t h e e s t i-m a t e d n u m b e r o f n e w i n d i v id u a l s b e t w e e n e a c h c a p t u r e d a y . A t S o t o d e l R e a l , to t a lp o p u l a t i o n w a s e s t im a t e d t o b e 1 2 4 4 i n 1 9 9 0 a n d 1 05 1 i n 1 9 9 1 . T h e p e a k a d u l t n u m -b e r s w e r e a r o u n d 6 0 0 i n d i v i d u a l s i n b o t h y e a r s ( 5 7 7 a n d 6 1 3 r e s p e c t i v e l y , f i g . 1), b u tt h e p e a k d a y w a s r o u g h l y 1 5 d a y s l a t e r i n 1 9 9 1 t h a n i n 1 9 9 0 .A d u l t b e h a v i o u r a n d n e c t a r u s e

T h e o b s e r v e d b e h a v i o u r a t t h e m o m e n t o f c a p tu r e d u r i n g t he m a r k - r e c a p t u r es t u d y is s h o w n i n f i g u re 3 . T h e f l o w e r s p e c i e s u s e d b y a d u l t s a t th e m o m e n t o f c a p t u r ea r e s h o w n i n f ig u r e 4 . I n 1 9 9 0 a n d 1 9 91 t h e p a t t e r n o f n e c t a r r e s o u r c e u s e i s c l e a r l yd i f f e r e n t . W h i l e i n 1 9 9 0 t h e m a i n n e c t a r s o u r c e w a s R a n u n c u l u s b u l b o s u s , in 1991t h e r e w a s a s h i f t t o o t h e r s p e c i e s a n d t h e b u t t e r f l i e s a ls o f r e q u e n t l y u s e d G l o b u l a r i acordi fo l ia a n d A n t h e m i s a r v e n s i s .T h e m o s t a b u n d a n t f l o w e r s p e c i e s re c e i v e d t h e h ig h e s t n u m b e r o f v i s it s b y b u t -t e r f l i e s ( r = 0 . 3 7 , p = 0 . 0 1 4 , w i t h l o g t r a n s f o r m e d d a t a ) , i n d i c a t i n g t h a t f l o w e r s p e c i e sw e r e s e l e c t e d p r i m a r i l y a c c o r d i n g t o t h e i r a b u n d a n c e . F l o w e r s ( o r i n f l o r e s c e n c e s )l a rg e r th a n 1 c m w e r e p r e f e r e d ( A N O V A w i t h l o g n u m b e r o f f lo w e r s a s c o v a r ia t eF = 9 . 0 2 , p = 0 . 0 0 5 , d f = 1 , 4 0 ) . A f t e r e x c l u d i n g f l o w e r s s m a l l e r t h a n 1 c m ( t h a t c O u l dp r o v e u n s u i t a b l e f o r t h e b u t t e r f l ie s t o s e t t le ) f r o m t h e a n a l y s i s , th e c o r r e l a t i o n b e t w e e nn u m b e r o f b u t t e r fl y v i s it s a n d t h e a b u n d a n c e o f e a c h o f t h e f l o w e r s p e c i e s u s e d f o rn e c t a r f e e d i n g r e m a i n s h i g h l y s i g n i f i c a n t ( r = 0 .5 5 , p = 0 . 0 0 2 , r e g r e s s i o n e q u a t i o n :L o g N o f l o w e r s v i s i t e d = 4 ) . 0 8 + 0 .3 3 L o g N o f l o w e r s ) . I n al l t h e a n a l y s e s , f o u r p l a n ts p e c i e s s h o w e d u n e x p e c t e d l y h i g h r e s i d u a l v a l u e s , i n d i c a t i n g a s l i g h t p r e f e r e n c e f o rf l o w e r s o f R a n u n c u l u s b u l b o s u s , G l o b u l a r i a c o r d i f o l i a , A n t h e m i s a r v e n s i s a n dA r m e r i a a l l i a c e a ( i n d e c r e a s i n g o r d e r ) .

A d u l t s p a t i a l d i s t r i b u t io nT h e s p a t i a l d i s t r i b u t i o n o f E . a u r i n i a c a p t u r e d a d u l ts i s s h o w n i n f ig u r e 5 f o r t h e

y e a r s 1 9 9 0 a n d 1 9 91 . T h e n u m b e r o f m a l e s a n d f e m a l e s c a p tu r e d p e r p l o t w a s h i g h l yc o r r e l a t e d i n d i c a t i n g s i m i l a r w i t h i n s i t e d i s t r i b u t i o n i n b o t h s e x e s ( r = 0 . 7 5 , p

use of space and resources in a mediterranean population of the butterfly euphydryas aurinia

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