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169
ZOOSYSTEMA • 2015 • 37 (1)
© Publications scientiques du Muséum national d’Histoire naturelle, Paris. www.zoosystema.com
KEY WORDS
conservation,
butteries,
restoration ecology,
oviposition,
larval development.
urn:lsid:zoobank.org:pub:791830E1-C6B6-4064-984E-C9DBCA6816CD
Bonelli S., Barbero F., Casacci L. P.& Balletto E.2015. — Habitat preferences of Papilio alexanor Esper, [1800]: im-
plications forhabitat management in the Italian maritime Alps, in Daugeron C., Deharveng L., Isaia M., Villemant C. &
Judson M. (eds), Mercantour/Alpi Marittime All Taxa Biodiversity Inventory. Zoosystema 37 (1): 169-177. http://dx.doi.
org/10.5252/z2015n1a7
ABSTRACT
Papilio alexanor Esper, [1800] is a threatened European buttery species listed in Annex IV of the Habi-
tats Directive and in Appendix II of the Bern Convention, being considered extremely vulnerable to
climate change. According to some projections (e.g., Bambu, a scenario of moderate climate change),
it would be expected to lose63% of its European climatic niche by the year2050 and77% by2080.
e few remaining populations are expected to become concentrated in the Maritime Alps. In2009
and2010, we studied what is probably the densest P.alexanor population in the Italian part of this area.
It occurs in a series of dry, xerothermic grasslands, also partially occupied by an abandoned limestone
quarry, where the larval food plant is Ptychotis saxifraga (L.) Loret & Barrandon. Females lay eggs in
July, choosing patches where the food plants are higher and more abundant. e habitat preference,
conservation status and survival of the early instars larvae of P.alexanor have been investigated in order
to draw up conservation strategies for this species in the Italian Maritime Alps.
RÉSUMÉ
Préférences d’habitat de Papilio alexanor Esper, [1800]: implications pour la gestion de l’habitat dans les
Alpes-Maritimes Italiennes.
Papilio alexanor Esper, [1800] est un papillon diurne menacé en Europe et inscrit à l’Annexe IV de la
Directive Habitats dans l’Appendice II de la Convention de Berne. Cette espèce est considérée comme
particulièrement sensible aux changements climatiques. Selon quelques projections (ex.Bambu, un
scénario de changement climatique modéré), elle serait susceptible de perdre63 % de sa niche cli-
matique européenne d’ici à l’année2050 et jusqu’à77 % d’ici à2080. On peut s’attendre à ce que
les quelques populations survivantes soient concentrées dans les Alpes maritimes. En2009 et2010,
nous avons étudié la population de P.alexanor probablement la plus dense parmi celles qui habitent
la portion italienne de ce territoire. Elle occupe une série de friches semi-naturelles aussi bien qu’une
Simona BONELLI
(Corresponding author)
Francesca BARBERO
Luca Pietro CASACCI
Emilio BALLETTO
Department of Life Science and Systems Biology, Turin University
Via Accademia Albertina13 10123, Turin (Italy)
simona.bonelli@unito.it
francesca.barbero@unito.it
luca.casacci@unito.it
emilio.balletto@unito.it
Habitat preferences of Papilio alexanorEsper,[1800]:
implications forhabitat management
intheItalianMaritimeAlps
170 ZOOSYSTEMA • 2015 • 37 (1)
Bonelli S. et al.
carrière de roches calcaires aujourd’hui désaectée. Dans notre aire de travail la plante nourricière
des chenilles est Ptychotis saxifraga (L.)Loret & Barrandon. Les femelles pondent leurs œufs au mois
de juillet, choisissant les sites où les plantes nourricières sont particulièrement hautes et abondantes.
Les préférences écologiques, l’état de conservation et la survie des premiers stades du développement
larvaire ont été étudiés, en vue de proposer une stratégie pour la conservation durable de cette espèce
dans les Alpes maritimes italiennes.
MOTS CLÉS
conservation,
papillons,
écologie de la
restauration,
oviposition,
développement larvaire.
INTRODUCTION
Papilio alexanor Esper, [1800] is a swallowtail buttery with
a highly fragmented Euro-Central Asiatic range. It occurs
in the pre-Alps and sub-Mediterranean areas of SE France,
from Provence to the French Maritime Alps, while in Italy it
is restricted to a few sites of the Ligurian and Italian Maritime
Alps. Outside of this range, its distribution shows a very wide
gap and it occurs again in the southern Balkans, thereafter
extending eastwards as far as Central Asia (see Kudrna etal.
2011). e rst records of P.alexanor in the Italian Alps date
back to the 1970s, when it was found in the Ligurian Alps
(Balletto& Toso1976). In the Maritime Alps, apart from
an old, unconrmed report by Turati& Verity (1911-12;
“Col de Fenestre”) and a vaguely localized record by Barajon
(1957: “upper Val Tanaro”), its occurrence was conrmed
only much later (Baldizzone1971; Balletto etal. 1982). More
recent reports include those by Ortali& Bertaccini (1987),
Prola& Prola (1990), Sala& Bollino (1991), Audisio& De
Biase (1993), David& Sanetra (1994) and Arnscheid (2000).
e presence of this species in the general area had, however,
already been known to amateur collectors for a number of
years. Populations from the Italian Maritime Alps were later
described as “ssp. radighierii” Sala& Bollino, 1991. Elsewhere
in Italy, although P.alexanor was sometimes observed in some
parts of Calabria and NE Sicily (see Fig.2), it does not have
any stable populations there and the records probably refer
to stray adults having reached the Italian Peninsula by ying
from the Balkans.
In NW Italy, the species is found in mountainous or
hilly regions, from around500 to1200m a.s.l., but at least
occasionally reaching up to2100m, at Col de Tende (E.
Balletto, personal observation). Papilioalexanor is a ther-
mophilous species that prefers calcareous areas, on south-
facing, sometimes steep and rocky slopes. is is probably
a consequence of the ecological needs of its food plants,
some of which are pioneering species selecting eroded and
poor soils. e larvae feed on various Umbelliferae mainly
Ptychotis saxifraga (L.) Loret& Barrandon in the Maritime
Alps, but eggs can also be laid on Trinia glauca ssp. glauca
(L.) Dumort (C. Forte, pers. comm.; Nel& Chauliac1983;
Bollino& Sala2004). At lower elevations (500-800m) of
the southern slopes of the Ligurian Alps, caterpillars are
found on Opoponax chironium (L.) Koch (see Reche1978),
while populations from the Balkans and Central Asia may
use several species of Ferula (see de Freina1996). As observed
by Nel (1991), each population (or group of populations)
of P.alexanor generally shows a selected trophic preference
for a single Umbelliferous species, although the use of up to
three species, each having dierent blooming time, has been
reported locally for some populations from central Greece
(Pimpinellasp., O.chironium, Ferulagosp., see Bollino&
Sala2004). Similar local plant-shifts are also reported for
French populations, where larvae of P.alexanor, occurring
on opposite slopes of the same hill, select O.chironium on
the northern side and P.saxifraga on the southern. e same
authors (Bollino& Sala2004) argue that the capability of
exploiting various food plants having spaced-out blooming
times may represent an important adaptation in the case of
species having a prolonged emergence period. Papilioalexanor
is invariably monovoltine: adults may y from late March to
late July, depending on local climatic conditions (Bollino&
Sala2004). Papilioalexanor overwinters as a pupa, and is
known to stay in diapause for up to threeyears (Nakamura&
Ae1977; Bollino& Sala2004).
Although P.alexanor is listed in Annex IV (species of
community interest) of the Habitats Directive (H.D.) and
in Appendix II (strictly protected species) of the Bern Con-
vention, no immediate or major threats to its survival have
been identied at the European level and it is considered a
species of “least concern” (van Swaay etal. 2010). In2007
its conservation status under Article17 (H.D.) was assessed
as “favourable” for the Alpine region and “unknown” for the
Mediterranean area.
Papilioalexanor, however, is known to be particularly vulner-
able to climate change and Settele etal. (2008) have listed it
as an “Extremely high climate change risk (HHR)” species, in
their Climate Risk Atlas of the European butteries. Indeed,
climate change will soon represent a real threat for P.alex-
anor, which, according to currently available climatological
scenarios, is expected to lose63% of its European climatic
niche by2050, and77% by2080 (Bambu scenario). Given
its good dispersion ability, it is likely that P.alexanor will
respond to climate change by colonizing new, climatically
suitable areas, as suggested by recent observations of isolated
individuals far north from its actual range along the Rhone
Valley, especially during the warmest years. However, sites
in the SW Alps will be among the very few to oer suitable
conditions for its long-term survival, so that it is extremely
important to protect all populations in the Maritime and
Ligurian Alps, in order to mitigate the severe eects that
climate change will have on this species.
171
ZOOSYSTEMA • 2015 • 37 (1)
Papilio Alexanor in the Italian Alps
Even though no population extinction is known to have
aected P.alexanor on Italian territory (Bonelli etal. 2011a)
and all known Italian populations occur within protected areas
(Bonelli etal. 2011b), we recently estimated as “inadequate”
the overall conservation status of this species, on the basis of
its “future prospects”. Apart from climate, the other threats
that Italian populations are facing, and which may eventu-
ally undermine the long-term persistence of this species,
are mainly connected with the abandonment of traditional
pastoral systems and the return of natural forestation (H.D.
Article17 assessment; Balletto etal. in press).
Perhaps the most severely threatened Italian population of
P.alexanor occurs in Valdieri, in the Italian Maritime Alps
(Maritime Alps natural Park – SCI and SPZ IT1160056).
Adults occur there in a semi-natural habitat (calcareous rocky
slopes, Annex I Habitats Directive, 8210) and in an aban-
doned quarry. Among the most important factors threatening
this population we can cite: 1) over-collecting of both adults
and larval stages; 2) habitat loss, as a consequence of natural
forestation; and 3) possible opening of new quarrying activi-
ties in the area.
We investigated this population in the years2009 and2010
within the framework of the programme “Inventorying biodi-
versity in the Mercantour/Marittime”, funded by the European
Distributed Institute of Taxonomy (EDIT).
e main aims of our study are listed below:
–eld study of the local larval food-plant. ere is growing
evidence of polyphagous buttery species that are monopha-
gous at the local level. is would have strong inuence for
in situ conservation plans and general habitat management
(see Dolek etal. 2013);
–assess habitat preferences and food-plants use. We wanted
to evaluate whether females select oviposition sites on the
basis of microhabitat characteristics or of some specic plant
features, as observed in other buttery species (e.g., Patricelli
etal. 2011);
–assess the conservation status of P.alexanor at Valdieri sites.
Since swallowtails are large butteries and require substantial
amounts of food to reach their nal instars, it will be useful
to estimate the food plant density and the area of favourable
habitat needed to guarantee the long term survival of this
population.
Fig.1.—Papilio alexanor Esper, [1800]. Photograph: Davide Piccoli.
172 ZOOSYSTEMA • 2015 • 37 (1)
Bonelli S. et al.
MATERIALS AND METHODS
During the spring-summer period of2008, preliminary in-
spections were made to verify the persistence of the Papilio
alexanor population and conrm that Ptychotis saxifraga is the
larval food-plant in the study area.
Study area
Papilio alexanor adults and eggs occur in both natural and
semi-natural/replacement habitats.
e buttery was detected in the abandoned quarry of Valdieri
and in the nearby Natural Reserve for Juniperus phoenicea.
e limestone banks that extend to the East of Valdieri were
quarried for about35years (1962-1997) for the preparation
of cement (Ansaldi etal. 2006).
e Phoenician juniper (Juniperus phoenicea L.) is a very rare
plant in this part of Italy, where it reaches its northernmost
limit. A Natural Reserve for the protection of an important
stand of this shrub was therefore created in1984. It extends
over the limestone and dolomitic banks occurring close to
the summit of Mt Saben (1670m), where the southern
exposition and the presence of carbonate rocks favour the
establishment of a microclimate that is also suitable for the
survival of P.alexanor.
Sampling the food plantS and the larval inStarS
Papilioalexanor is a fast and high-ying swallowtail buttery
that always occurs at low densities, which makes studying its
adult’s population dynamics by the Mark-Release-Recapture
method unfeasible. During the summers of2009 and2010,
we surveyed the spatial distribution of P.saxifraga and focused
our eorts on nding the pre-imaginal stages of P.alexanor.
We randomly chose47quadrats (25m2) in which at least
one food plant existed. In each geo-referenced plot, we col-
lected data on the number and height of P.saxifraga plants. We
measured the density of the vegetation cover and the propor-
tion of bare soil, according to the Braun-Blanquet’s method
(Braun-Blanquet1932). For each plot, we noted the number
of eggs, larvae and/or pupae of P.alexanor. In2010, the same
data were collected once a week for the whole ight period
of P.alexanor adults, to assess the in-eld larval development
and the microhabitat requirements of the early stages. Finally,
we measured the minimum distance of each plot centre from
the nearest thistle plant (e.g., Carduus, Cirsium), since these
plants represent the only nectar sources potentially available
for P.alexanor adults at that time of the year.
In addition to eld sampling, we performed a study of the
survival of larval instars in the laboratory. Ten plants bear-
ing visible P.alexanor eggs were collected, carried and set in
laboratory conditions. We measured the length of each larval
stage during development and the number of days between
each moulting until pupation.
StatiStical analySiS
Data on plot parameters collected over the two-year samplings
were not normally distributed. erefore, we used non-
parametric tests to compare the ecological factors between
occupied and unoccupied plots, in separate tests.
We used the Wilcoxon test to compare the numbers and
heights of P.saxifraga plants, the percentage of bare soil and
vegetation cover, between plots occupied by P.alexanor in2009
and/or in2010. e Mann-Whitney-U test was used to assess
dierences in plot distances from the rst colonised square
and the rst nectar source (thistle) between plots, either oc-
cupied or unoccupied by P.alexanor.
In-eld larval survival was calculated for each plot, using
data collected in2010, as the number of larvae divided by
the initial number of eggs. Dierences in larval survival be-
tween plots occupied by increasing numbers of food-plants
were analysed with the Friedman two-way analysis of vari-
ance by ranks test.
RESULTS
During the summer of2008, we conrmed the persistence
of a P.alexanor population in the surroundings of an aban-
doned quarry in the Valdieri area. Larvae were feeding only
on P.saxifraga.
Survey of P. saxifraga
In2009, we surveyed the food-plants and counted P.alexanor
eggs, larvae and pupae. We identied47quadrats, spanning
in altitude from700to950m, where P.saxifraga was pre-
sent. At the base of the quarry, the food-plant was located
Fig.2.— Stable range of P.alexanor Esper,[1800] in Italy (Balletto etal. 2007),
observations from S Italy are interpreted as being based on vagrant specimens
from the Balkans, the arrow indicates the Valdieri study area.
173
Butteries of the Italian maritime Alps
ZOOSYSTEMA • 2015 • 37 (1)
mostly in the low-lying areas colonised by pioneer vegetation,
while at higher altitudes it occurred at the edge of the rocky
terraces and on the south facing rocky slopes. e data col-
lected in2009 allowed us to estimate P.saxifraga coverage:
about1.8hectares out of a total of29.5hectares surveyed,
while in2010 the proportion of habitat occupied by the food-
plant had slightly decreased, to1.5ha. In2009, 594plants
were scanned: 538of them (90.5%) did not present any trace
of P.alexanor eggs, while56 (9.5%) were exploited by the
buttery and occurred in28out of47quadrats.
Within each quadrat we counted from a minimum of
oneplant up to a maximum of50. e average height per
plot of the P.saxifraga plants varied between20 and 60cm.
In2009 we counted a total of65eggs, as well as70rst,
43second, 12third andfournal (IV and V) instar larvae,
and5pupae of P.alexanor.
In2010, we monitored the same47patches surveyed
in2009. e distribution of P.alexanor was similar to that
observed in2009, butnineplots were no longer occupied
in2010, whilevepatches unexploited in2009 were colo-
nized by P.alexanor in2010.
e comparison between the quadrats monitored in our
two-year study showed that occupancy depends on the number
of P.saxifraga plants (Wilcoxon test: Z = –2.745, p = 0.006)
as well as on the percentage of plant cover (Wilcoxon test: Z
= –2.251, p = 0.024) (Fig.3).
Quadrats colonized by P.alexanor also showed a statistically
signicant larger average height of the food-plants (Wilcoxon
test: Z = –2.506, p = 0.012) (Fig.3). e percentage of bare
soil showed no statistically signicant correlation, while the
percentage of other vegetation was lower in the quadrats oc-
cupied by the buttery (Wilcoxon test: Z = –2.254, p = 0.024).
In2010, 21patches were exploited by P.alexanor while26were
unoccupied. A total of423P.saxifraga plants were examined,
356of which (84%) did not bear any pre-imaginal P.alexanor
pre-imaginal instars, while67 (16%) were occupied by the
buttery. Inside quadrats we surveyed a minimum of oneplant
up to a maximum of32 plants. In quadrats with P.alexanor
we examined an average (± SD) of11.2 ± 8.6 plants.
Comparing distances between quadrats, we found that
plots where P.alexanor was absent were much more isolate
than those where the buttery was present (Mann-Whitney
U = 84.000, p = 0.18), the distance between the occupied
quadrats and the nearest quadrat was lower (15.81 ± 4.23m,
mean ± SE) than the distance between unoccupied quadrats
(27.22m±4.50; mean±SE) (Fig.3). Distances from the
nearest potential nectar source (thistles) were similar for plots
where P.alexanor was present and those where it was absent
(Mann-Whitney U = 155.5, p = 0.950).
larval Survival in the laBoratory
On average, larval development lasted22days and the transi-
tion from one stage to the next took4.1 ± 0.7days (Fig.4).
Larval body length changed from0.4 ± 0.15cm (rst instar
larvae) to a maximum of4.3 ± 3.5cm (nal instar larvae).
e development of the last instars was faster than that
of rst instar larvae: P.alexanor took about a week to pass
fromthird instar larva to pupa (Fig.4). Two butteries hatched
in the laboratory and were transported, along with the reared
pupae, to their site of origin.
present presen
tp
resent
absent absen
ta
bsent
Occurrence of P. alexanor Occurrence of P. alexanor Occurrence of P. alexanor
Height of P. saxifraga
plants (cm)
50
40
30
20
10
0
Number of P.saxifraga
plants
0
5
10
15
20
Percentage
of vegetation
60
50
40
30
20
10
0
A
BC
0510 15 20 25
0
5
4
3
2
1
e
I
II
III
IV
p
Days
Lenght (cm)
F
ig
.3.— Comparison of mean number (A) and height (± SD) (B) of P.saxifraga (L.) Loret& Barrandon and average percentage (± SD) of vegetation cover
(C) between occupied and unoccupied plots by Papilio alexanorEsper,[1800].
F
ig
.4.— Pre-imaginal development of Papilio alexanor Esper,[1800] under
laboratory conditions; box plots illustrate increases in larval length; vertical
lines: median larval length; box: 25th-75th percentiles; whiskers: minimum
and maximum observed values; outliers; dark grey band width represents
the standard deviations of mean development intervals (days). Abbreviations:
e,egg; I-IV, larval instars; p, pupa.
174 ZOOSYSTEMA • 2015 • 37 (1)
Bonelli S. et al.
development of P. alexanor in field conditionS
During2010, we observed a total of369eggs and268larvae.
P.alexanor females laid on average2.4 ± 0.99eggs (mean ±
SD) on each plant, but in quadrats where the availability of
plants was more limited (oneor few P.saxifraga plants), we
found a higher number of eggs per plant (up to20 eggs per
plant). Within quadrats, depositions occurred on an average
of2.6 ± 1.6 plants (min1; max5), even when plant avail-
ability was high.
As can be seen in Fig.5, the highest number of eggs was
found in the rst week of sampling (6.81 ± 1.02 eggs per quad-
rate), whereas this value decreased during July, as the number
of caterpillars increased. e highest number of larvae was
observed during the third sampling (on average5.04±0.73
larvae per quadrat). In total, 24 larvae atfourth orfth instar
were found during the last two sampling events, as well as a
single pupa (Fig.5).
We calculated the survival rates of three larval stages, from
the second to the nal instar larva. Survival was similar for
second and the third instar larvae, while it was signicantly
lower for nal instar larvae. Comparing the average larval
survival within each quadrat with the available number of
food-plants, we observed that larval survival increased when
the number of plants was higher than15 (Friedman’s test:
Z= 6.000; p = 0.05) (Fig.6).
DISCUSSION
Our results show that P.alexanor is locally monophagous: in
the study area it strictly exploits Ptychotis saxifraga, whereas
at a locality situated 70km away (above Latte, in the prov-
ince of Imperia) it exclusively feeds on Opoponax chironium.
Local exploitation of a single food-plant species commonly
occurs in otherwise polyphagous butteries (e.g., Finke&
Scriber1988), including Papilionidae Latreille, 1802. For
example, Papilio glaucus (Linnaeus, 1758) is considered one of
the most polyphagous species among Papilionidae (563species
in the world), using more than14dierent families as food-
plants in North America, yet this species is monophagous in
Florida (Scriber1986). Studies carried out under laboratory
conditions have shown that the larvae of Papilio troilus (Lin-
naeus, 1758) are associated with various species of Lauraceae,
depending on the geographical area. More specically, they can
survive on three dierent plants, but growth rates are inu-
enced by the essence selected (Nitao etal. 1991). Euphydryas
maturna (Linnaeus, 1758) is another example of a buttery
locally using dierent plants. Females lay their eggs on the
leaves of Fraxinus excelsior L. and the whole pre-hibernation
development takes place on this plant. After winter diapause,
larvae are known to feed on various common herbaceous
species, such as Pulmonaria ocinalis L., Lonicera coerulea
L., Veronica longifolia L., Violasp. and Plantago lanceolata
L. (see Freese etal. 2006). Nonetheless, at the local level the
buttery selects only one plant species to feed on, even where
many more are available (Dolek etal. 2013).
eoretical studies predict that butteries, like many other
phytophagous insects, will tend to specialise, moving from
polyphagy to monophagy, since any new mutation that in-
creases tness on the primary host plant, and thereby lowers
the relative tness on secondary host plants, will be favoured
by selection (Bernays& Graham1988, Futuyma& More-
no1988, Futuyma2008). Furthermore, at least in some cases,
additional advantages may be achieved by entering relatively
competitor-free new spaces (Wiklund& Friberg2008).
Local adaptations to single host plants may have favoured
dierentiation between populations, which might eventually
culminate in speciation. In fact, the two populations from
Latte (IM) and from Valdieri have been described as separate
subspecies (respectively P.alexanor alexanor Esper, 1799and
P.alexanor radighierii Sala& Bollino, 1991) and should at
least be considered separate ESUs (Casacci etal. 2013). Dier-
ences between them may have become xed and maintained
by the temporal shift (about15days) in the blooming of the
Number of P. alexanor larvae
and eggs (mean ± SE)
Sampling dates
9
8
7
6
5
4
3
2
1
0
9 July 2010 15 July 21 July 28 July
I instar
II instar
III instar
IV+V instars
eggs
tot. larvae
Fig.5.— Pre-imaginal development of P.alexanor Esper, [1800] in the eld. Mean (± SE) number of eggs and larvae of P.alexanor collected during thefour sam-
pling events (2010).
175
Butteries of the Italian maritime Alps
ZOOSYSTEMA • 2015 • 37 (1)
two locally selected host plants. Nevertheless, in standard
eld guides the descriptions of many buttery species are
accompanied by long lists of food-plants. Exact information
on regional food-plant variation is, in contrast, relatively
scanty, or provided independently from information on the
ecological context.
In our study area, oviposition took place at the end of June,
in agreement with the phenology of P.saxifraga, and larval
development occurred in July. e females laid few eggs per
plant (2.4 ± 0.99 on average), as previously reported (Bol-
lino& Sala2004), and used on average2.6plants close to each
other for oviposition (no more than veplants per plot), even
when many plants occurred in5× 5m plots. Females scattered
their eggs and this may increase their ospring’s tness. As
observed in eld and laboratory conditions, P.alexanor larvae
need to feed abundantly to exponentially increase their body
mass in about20days. Moreover, it is likely that females lay
few eggs per plot to prevent cannibalistic behaviour, which
is very frequent among buttery caterpillars.
If we assume that: 1) the sex ratio in the P.alexanor population
is balanced; 2) a single P.alexanor female lays about70/80eggs
during a season (C. Forte, pers. comm.); and 3) the area
covered by P.saxifraga was of1.5ha, having sampled the egg
density, the adult population size in the study area can be
estimated at about 170individuals. Nevertheless, it seems
that the Valdieri population, and therefore also its ovipos-
iting preferences, may be considered representative of the
whole “subspecies radighierii”, which often occurs in small,
but constant and isolated areas, supported by a few hectares
of suitable habitat (Bollino& Sala2004).
Our results indicate that the number of food-plants and their
height are among the factors that aect the number of eggs
laid by P.alexanor females on Ptychotis saxifraga plants. Female
preference for plots with high numbers of plants is conrmed
by the fact that larval survival is higher in those plots where
the number of P.saxifraga was more than15plants (Fig.6),
probably because larvae need to consume a great amount
of food. Selection for oviposition of higher plants, usually
having a larger number of owers, is common in butteries
(e.g., Myers etal. 1981; Courtney1984; Bonelli etal. 2005;
García-Barros& Fartmann2009). e most likely explana-
tion is that gravid females choose visually prominent plants
as their main targets. e fact that the distances of occupied
plots from the rst patch with P.saxifraga plants were lower
than between unoccupied plots suggested that, as for other
Lepidoptera (ompson& Pellmyr1991), P.alexanor females
accept or reject certain plants as oviposition sites on the basis
of their relative position in the food-plant community. On
the contrary, we did not observe any dierence in distances
from the nearest nectar source between occupied and unoc-
cupied patches. is is consistent with the high vagility of
P.alexanor adults, which can easily move from nectar sources
to oviposition sites, as well as with the relative abundance of
thistle plants, which were probably sucient to support the
whole P.alexanor population.
In agreement with observations by Bollino& Sala (2004),
eggs took about sevendays to hatch in the eld, but developed
slightly faster under laboratory condition (aboutve days).
As noted in the literature, and observed in the eld, larvae
were easy to observe, not only because of their aposematic
colours, but also for their strong heliotropism, which causes
them to remain on a ower stem and rarely abandon it. Just
before pupation, the caterpillar usually abandons the plant
and pupates near the ground, indicating a negative photo-
taxis (Nakamura& Ae1977). e low number of individu-
als observed belonging to the last two stages may be related
to the diculty, already noted by other authors (Bollino&
Sala2004), of nding the last instar larvae and the mimetic
pupae of P.alexanor in eld conditions.
conServation remarkS
In order to ensure the persistence of the population in the
study area, we suggest that it is important to take into account
both the ecological features of the resident P.alexanor popula-
tion (e.g., the correlation between food plant’s phenology and
larval development) and the most signicant local threats. In
particular it will be crucial to discourage collectors of both
adults and larvae. Sampling could be authorized only for
justied scientic reasons and surveillance of the area should
be ensured, at least during June-July.
At the same time, to ensure the long-term persistence of the
species it would be essential to create new habitats, or restore
old ones, where suitable growth condition for P.saxifraga can
be assured. In this context, the restoration of the abandoned
quarry would generate very good opportunities for P.alexanor.
Butteries frequently benet from areas transformed by
human activity, such as pastures or areas under non-intensive
cultivation, and suer rapid decline when these habitats
are abandoned or altered (Balletto etal. 2007; Skorka etal.
2007). Less common, but relatively well known, are cases of
colonisation of quarry areas. A study performed in Bedford-
shire (UK) (Turner etal. 2009) has shown the settlement of
a riodinid buttery, Hamearis lucina (Linnaeus, 1758), at an
abandoned chalk quarry, fostered by the availability of its
larval food plants. e latter benet from disturbance caused
by occasional landslides on unstable ground and prefers steep
slopes, in the lee of the wind. us, as also demonstrated by
0
0.1
0.2
0.3
0.4
0.5
0.6
Larval survival
Number of P. saxifraga
<10 10-15 >15
L2 L3 L4 + 5
F
ig
.6.— Comparison of mean values of larval survival rates calculated for
the21 (occupied) plots ranked by increasing total number of P.saxifraga (L.)
Loret& Barrandon plants.
176 ZOOSYSTEMA • 2015 • 37 (1)
Bonelli S. et al.
the present study, abandoned quarries may harbour a signi-
cant number of plants, many of which may be characterized
by peculiar ecological requirements. Results of a comparative
study of buttery communities, carried out in 21limestone
quarries at the Moravian Gate (Czech Republic), showed that
quarries can provide secondary habitats for xerophilous spe-
cies, replacing the calcareous grasslands once densely popu-
lated by butteries (Benes etal. 2003). Butteries beneting
from these areas are rare xerophilous species and/or sedentary
species. eir abundance, even during extraction activities,
conrms the idea that quarries can contribute signicantly
to the conservation of these butteries.
Unfortunately, the ecological requirements of these species
are rarely considered in the management commonly practiced
in the dry grasslands of Central Europe, which typically aims
at protecting sites where charismatic plants (e.g., orchids)
are growing (Balmer& Erhardt2000; Kahmen etal. 2002).
Acknowledgements
e All Taxa Biodiversity Inventory + Monotoring Mercantour/
Alpi Marittime was launched by the European Distributed
Institute of Taxonomy (EDIT) project (2006-2011).
We thank M.De Biaggi (Parco Alpi Marittime) and
M.-F.Leccia (Parc national du Mercantour).
We also thank the Municipality of Valdieri and L.Mavilla,
C.Forte and E.Rivella (Regional Agency for Environmental
Protection – ARPA Piemonte). We are also grateful to the
reviewers for their helpful comments.
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Submitted on 5March 2014;
accepted on 20October 2014;
published on 27March 2015.