86 research outputs found
Butterflies and moths (Insecta, Lepidoptera) recorded at sea off Eivissa and Barcelona (Western Mediterranean) in October 1996
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General declines in Mediterranean butterflies over the last two decades are modulated by species traits
Species’ responses to environmental changes are highly idiosyncratic and context-dependent. Although intrinsic traits (i.e. those that define species niches) may play a key role, little empirical evidence exists regarding their relationship to demographic responses. We used data for 66 butterfly species representing five ecological and two life-history traits to study the effect these factors have on population growth rates and variations in populations. Using a novel methodological approach, we provide here improved estimates of population change. Our results reveal declines in 70% and increases in 23% of the studied species, clear evidence of more serious population declines in Catalan butterflies than those that have previously been reported. Declines were associated with species' degree of habitat specialisation and the number of generations. For all species, fluctuations were greater within than between years and, on average, the latter was 1.5 times greater. Our results indicated that habitat specialists and multivoltine species are more likely to suffer severe annual fluctuations in population abundance; and that multivoltine species and extreme larval specialists had the most marked fluctuations within seasons. We also found higher resilience to environmental changes in generalist species, which is concordant with biotic homogenisation in disturbed communities. However, amongst the declining species there were also many generalists, which indicates a potential general reduction in this group that goes beyond faunal homogenisation. Given butterflies are biodiversity indicators, these patterns are a possible reflection of an overall impoverishment in biodiversity
DistribuciĂł i abundĂ ncia de Symphurus nigrescens Rafinesque, 1810 i Symphurus ligulatus (Cocco, 1844) (Pisces, Pleuronectiformes) en el talĂşs del mar CatalĂ
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Strong, Long-Term Temporal Dynamics of an Ecological Network
Nature is organized into complex, dynamical networks of species and their interactions, which may influence diversity and stability. However, network research is, generally, short-term and depict ecological networks as static structures only, devoid of any dynamics. This hampers our understanding of how nature responds to larger disturbances such as changes in climate. In order to remedy this we studied the long-term (12-yrs) dynamics of a flower-visitation network, consisting of flower-visiting butterflies and their nectar plants. Global network properties, i.e. numbers of species and links, as well as connectance, were temporally stable, whereas most species and links showed a strong temporal dynamics. However, species of butterflies and plants varied bimodally in their temporal persistance: Sporadic species, being present only 1–2(-5) years, and stable species, being present (9-)11–12 years, dominated the networks. Temporal persistence and linkage level of species, i.e. number of links to other species, made up two groups of species: Specialists with a highly variable temporal persistence, and temporally stable species with a highly variable linkage level. Turnover of links of specialists was driven by species turnover, whereas turnover of links among generalists took place through rewiring, i.e. by reshuffling existing interactions. However, in spite of this strong internal dynamics of species and links the network appeared overall stable. If this global stability-local instability phenomenon is general, it is a most astonishing feature of ecological networks
Les papallones com a bioindicadores dels hĂ bitats a Catalunya: l'exemple dels prats de dall i le pastures del Parc Natural dels Aiguamolls de l'EmpordĂ
El Parque Natural de los Aiguamolls de lÂ’EmpordĂ
(PNAE) es uno de los espacios protegidos más conocidos
y emblemáticos de Cataluña. Uno de sus
hábitats más localizados y amenazados son las denominadas
closes, prados de siega destinados a la producciĂłn
de forraje, rodeados de canales de desagĂĽe e
inundados durante parte del invierno. Recientemente,
se ha demostrado que la comunidad vegetal más
tĂpicamente asociada con estos prados es la más rica
del Parque y la que alberga las especies más raras.
En este trabajo se utilizan datos de mariposas diurnas
(ropalóceros), obtenidos después de aplicar durante
17 años la metodologĂa del Butterfly Monitoring
Scheme, para evaluar el interés de conservación
de los principales ambientes del PNAE. Las closes
constituyen también para los ropalóceros el
hábitat más valuoso. La coincidencia en los resultados
obtenidos en dos grupos taxonĂłmicos amplios
y que ocupan niveles trĂłficos distintos, sumada a la
alarmante regresiĂłn que han experimentado las
closes en los últimos 50 años y a su singularidad en
el área mediterránea, permiten considerarlas objetivamente
como uno de los hábitats más amenazados
del PNAE y del conjunto de Cataluña. En una segunda
parte del trabajo, se analizan las respuestas
de las mariposas frente al abandono de las closes y
a su recuperaciĂłn a partir de antiguos cultivos intensivos.
Los cambios que experimentan las comunidades
de mariposas pueden pasar del todo desapercibidos
si los análisis se focalizan en indicadores
generales (p. ej., riqueza especĂfica y abundancia).
Contrariamente, se demuestra que la respuesta de
algunas especies potencialmente bioindicadoras
puede ser muy acusada, si bien es necesario conocer
su ecologĂa para poder interpretarla correctamente.
En concreto, se concluye que Plebejus argus representa
la mejor especie bioindicadora de las peculiares
condiciones ambientales propias de las
closes: las poblaciones responden con descensos
rapidĂsimos cuando estas condiciones se deterioran,
y también con aumentos progresivos cuando
el hábitat mejora. Además, se trata de una especie
muy sedentaria que se estructura en forma de
metapoblaciones, por lo cual el monitoreo de una
población local refleja también las condiciones
del paisaje de su entorno.Aiguamolls de lÂ’EmpordĂ Natural Park is one of
the most important protected wetland areas on the
Mediterranean coast. In this article, butterfly
assemblages were used to characterize and evaluate
the conservation value of the main habitat types in
this protected area. Butterfly data were obtained
from a number of transects walked as part of the
Catalan Butterfly Monitoring Scheme, which uses a
standardized methodology for monitoring butterflies.
Hay meadows flooded in winter (the so-called
closes) appeared always as the highest ranked
habitat in terms of conservation evaluation: they
have more butterflies and a slight tendency to
harbour more and generally rarer species. This
conclusion coincides with that of previous
investigations indicating that the most diverse and
rare plant communities in the whole Natural Park
are present in the closes, and highlights the
importance of traditionally managed hay meadows
for wildlife. However, these hay meadows are in
alarming decline and have become one of the most
threatened habitats in this area and the whole
Mediterranean region. In a second part of the
article, we analysed the responses of butterfly
communities once the closes are abandonned or
when they are recovered from former arable
fields. Changes may be completely overlooked if
the analyses are focussed on general patterns for
the whole community (e.g. species richness and
abundance). On the other hand, several individual
species showed strong population trends and some
of them may be considered as true bioindicators of
the narrow environmental conditions associated
with this kind of habitat. In particular, we suggest
that Plebejus argus represents an excellent
bioindicator of these traditionally managed hay
meadows: its populations always showed dramatic
decreases once the closes were abadonned,
overgrazed or invaded by exotic weeds, and
progressive increases once the quality of the
meadows improved. Moreover, this highly
sedentary species exists as metapopulations and,
therefore, the wealth of local populations also
reflects that of the surrounding landscape.El Parc Natural dels Aiguamolls de l'EmpordĂ
(PNAE) és un dels espais protegits més coneguts i
emblemĂ tics a Catalunya. Un dels seus hĂ bitats
més localitzats i amenaçats són les anomenades
closes, prats destinats a la producciĂł de farratge,
envoltats per canals de desguĂ s i bosc de ribera,
inundats durant part de l'hivern i dallats periòdicament.
Recentment s'ha demostrat que la comunitat
vegetal mĂ©s tĂpica de les closes Ă©s la mĂ©s rica
del Parc i la que alberga les espècies més rares. En
aquest treball s'utilitzen dades de papallones
diürnes (ropalòcers), obtingudes després d'aplicar
durant 17 anys la metodologia del Butterfly Monitoring
Scheme, per avaluar l'interès de conservació
dels principals ambients del PNAE. Les closes
constitueixen l'hà bitat més valuós també per als
ropalòcers. La coincidència dels resultats per a
dos grups taxonòmics amplis que ocupen nivells
tròfics diferents, sumada a l'alarmant regressió
que han experimentat les closes en els darrers 50 anys i a la seva singularitat dins de l'Ă rea mediterrĂ nia,
permeten considerar-les objectivament
com un dels hà bitats més amenaçats del PNAE i
de tot Catalunya. En una segona part del treball,
s'analitzen les respostes de les papallones enfront
de l'abandonament de les closes i de la seva
recuperaciĂł a partir d'antics conreus intensius. Els
canvis que experimenten les comunitats de
ropalòcers poden passar del tot desapercebuts si
les anĂ lisis es focalitzen en indicadors generals (p.
ex., riquesa especĂfica i abundĂ ncia). ContrĂ riament,
es demostra que la resposta d'algunes espècies
potencialment bioindicadores pot ser molt
més acusada, encara que cal conèixer la seva ecologia
per poder-la interpretar correctament. En
concret, es conclou que Plebejus argus representa
la millor espècie bioindicadora d'unes condicions
ambientals pròpies de les closes empordaneses
tradicionals: les poblacions responen amb descensos
rapidĂssims quan les condicions òptimes es deterioren,
i també amb augments progressius quan
l'hà bitat millora. A més, es tracta d'una espècie
molt sedentĂ ria que s'estructura en forma de
metapoblacions, per la qual cosa el monitoratge
d'una població reflecteix també les condicions del
paisatge del seu entorn
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