9 research outputs found
Dispersal in a metapopulation of the critically endangered Danube Clouded Yellow butterfly Colias myrmidone : implications for conservation
Colias myrmidone has suffered a dramatic decline in Europe, and now its
occurrence is restricted to just a few countries. We investigated one of
the last viable metapopulations (Knyszyn Forest, NE Poland), where the
butterfly is almost completely dependent on forestry, inhabiting some
clearings and young tree plantations rich in larval food plants
(Chamaecytisus ruthenicus) and nectar resources. Intensive
mark-recapture studies were performed in 2017 on eight occupied patches
separated by 0.5-5km. The overall population size of imagoes in the
second brood was calculated at about 750 individuals. Sex ratio was
shown to be well-balanced and average residency was estimated at 5.6
days. Dispersal occurred mostly between neighbouring patches, and
isolation of patches contributed to the high mortality of emigrants. The
average distance covered during dispersal was significantly higher for
males. However, females left small patches much more readily than males.
These patches were probably used only as stepping stone' sites in
dispersal. Restricted dispersal could be related to barriers created by
forest stands but it is also not excluded that individuals living in an
isolated metapopulation become increasingly sedentary and our results
are an early warning sign. The most distant local population was clearly
isolated, with hardly any immigration from the other populations. To
maintain a network of more stable habitat patches some clearings should
be left deforested and appropriately managed. However this goal is
difficult to achieve under the current forestry rules and therefore
(re)creation of habitats on other available open areas should be
considered
A unique population in a unique area : the Alcon blue butterfly and its specific parasitoid in the Białowieża Forest
What keeps "living dead" alive : demography of a small and isolated population of Maculinea (= Phengaris) alcon
Small and isolated populations are prone to future extinctions and thus
perceived as living dead'. Although generally considered to be of low
conservation value, their existence can still enhance species survival
at the landscape scale through improving the connectivity of other
populations and facilitating some (even if little) gene flow. We
investigated the demography and genetic status of a tiny and highly
isolated local population of Maculinea (=Phengaris) alcon near its
distribution margin with the aim of identifying the features that allow
it to persist. The study comprised intensive mark-recapture, surveys of
Gentiana pneumonanthe foodplants and butterfly eggs laid on them, as
well as genetic analyses. The population has been found to be
characterised by low genetic diversity and estimated at only a few tens
of individuals. The foodplant availability turned out to be the most
obvious factor limiting M. alcon abundance. Nevertheless, the life
expectancy of adult butterflies is fairly long, and their flight period
very short, implying that most individuals occur within the same time
window. Together with the relatively little protandry observed, i.e.
almost synchronous emergence of males and females, this increases the
chances of random mating among the individuals. Moreover, the
butterflies move freely across the core habitat fragment. All things
concerned, the effective population size is presumably not much lower
than the recorded population size. Our findings provide guidelines for
pinpointing those among "living dead" populations that are likely to be
the most persistent and thus worth conservation efforts aimed at
preserving them
A Unique Population in a Unique Area: The Alcon Blue Butterfly and Its Specific Parasitoid in the Białowieża Forest
Caterpillars of the Alcon blue butterfly Phengaris alcon are initially endophytic and feed inside the flowerheads of Gentiana plants, but complete their development as social parasites in the nests of Myrmica ants, where they are fed by workers. Its specific and complicated ecological requirements make P. alcon a very local, threatened species, sensitive to environmental changes. We investigated an isolated and previously unknown population in an area of high nature value—the Białowieża Forest (NE Poland). Using the mark–release–recapture method we estimated the seasonal number of adults at 1460 individuals, and their density (850/ha) was the highest among all populations using G. pneumonanthe studied so far. The site is also unique due to the presence of the specific parasitoid Ichneumon cf. eumerus, and parasitoids are considered the ultimate indicators of the biodiversity of Phengaris systems. Since 75.5% of P. alcon pupae were infested we could estimate the seasonal population of adult wasps at about 4500 individuals. The high abundance of both P. alcon and its parasitoid may be explained by favorable habitat characteristics, i.e., the strong presence of host plants and the high density of nests of Myrmica scabrinodis, which is the only local host ant of the butterfly
Population Genetic Structure and Demography of the Critically Endangered Chequered Blue Butterfly (Scolitantides orion) in a Highly Isolated Part of Its Distribution Range
Scolitantides orion is a butterfly species threatened in many European countries. In Poland, it survived in a single highly isolated area (Vistula River valley), which is an example of the dramatic decline in the population number. We studied the two largest remaining populations inhabiting opposite banks of the river. Mark-release-recapture studies showed that both populations were small, and they fluctuated in numbers, but adult individuals were twice as numerous on the western site. Genetic analyses were carried out using a mitochondrial (COI, ND5) and nuclear markers (Wgl, EF-1α, and microsatellite loci). We found out that genetic variation was low at both sites but higher in the smaller eastern population. This pattern is likely to be better explained by past distribution, when the butterfly, as a continental species used to be much more widespread in the east. However, the genetic differentiation between populations was low. This could suggest that the existing gene flow is facilitated by dominant regional wind direction, which may also contribute to a better genetic condition of the western population. Finally, a comparison of the obtained COI sequences with others available enabled us to reveal the phylogeographic pattern of the S. orion from different localities within its range
Patterns of host use by brood parasitic Maculinea butterflies across Europe
The range of hosts exploited by a parasite is determined by several factors, including host availability, infectivity and exploitability. Each of these can be the target of natural selection on both host and parasite, which will determine the local outcome of interactions, and potentially lead to coevolution. However, geographical variation in host use and specificity has rarely been investigated. Maculinea (=Phengaris) butterflies are brood parasites of Myrmica ants that are patchily distributed across the Palæarctic and have been studied extensively in Europe. Here, we review the published records of ant host use by the European Maculinea species, as well as providing new host ant records for more than 100 sites across Europe. This comprehensive survey demonstrates that while all but one of the Myrmica species found on Maculinea sites have been recorded as hosts, the most common is often disproportionately highly exploited. Host sharing and host switching are both relatively common, but there is evidence of specialization at many sites, which varies among Maculinea species. We show that most Maculinea display the features expected for coevolution to occur in a geographic mosaic, which has probably allowed these rare butterflies to persist in Europe