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Ročník:

55/2018

Název česky:

Taxonomické postavení, biologie a ekologie poddruhu suchozemského plže Cochlodina dubiosa corcontica (Mollusca: Gastropoda: Clausiliidae) endemického pro Krkonoše

Název anglicky:

Taxonomic position, biology and ecology of the endemic landsnail subspecies of the Krkonoše Mts Cochlodina dubiosa corcontica (Mollusca: Gastropoda: Clausiliidae)

Autor (autoři):

Pavel Tlachač; Adam Petrusek; Lucie Juřičková

Klíčová slova česky:

suchozemští plži, Clausiliidae, životní cyklus, ekologie, taxonomie, fylogeografie, 16S rRNA, holocén, radiokarbonové datování

Klíčová slova anglicky:

land snails, Clausiliidae, life cycle, ecology, taxonomy, phylogeography, 16S rRNA, Holocene, radiocarbon dating

Od strany:

Do strany:

Abstrakt česky:

Vřetenovka krkonošská, Cochlodina dubiosa corcontica (Brabenec 1967), je jedním z mála endemitů Krkonošského
národního parku. Přesto se tímto poddruhem suchozemského plže od doby jeho popisu nikdo nezabýval.
Pomocí fylogenetické analýzy středoevropských zástupců rodu, založené na mitochondriálním genu pro 16S rRNA,
jsme ověřili, že se jedná o taxon blízce příbuzný východoalpskému nominotypickému poddruhu C. d. dubiosa. Naše
analýzy také naznačují možnou hybridizaci vřetenovky krkonošské s nejběžnějším středoevropským zástupcem rodu,
C. laminata. Získali jsme vůbec první údaje o biologii vřetenovky krkonošské, přičemž se zdá, že aktivita i rozmnožování
tohoto plže souvisí stejně s aktuálními výkyvy počasí jako s roční dobou. Úspěšně jsme revidovali známé lokality,
objevili řadu nových a ukázali jsme, že pro výskyt tohoto endemitu je nutná především přítomnost padlého dřeva
listnatých stromů. Výzkumem dvou holocenních měkkýších sukcesí jsme chtěli zjistit, kdy se tento taxon do oblasti
Krkonoš pravděpodobně dostal. Vzhledem k ne zcela vhodným fosilizačním poměrům v oblasti krkonošských krystalických
vápenců byly ale ulity C. d. corcontica nalezeny jen v subrecentním kontextu, takže stáří tohoto dálkového
výsadku zůstává nadále tajemstvím. Naše studie potvrzuje, že vřetenovka krkonošská je geograficky izolovaný taxon
s nejbližšími příbuznými v Alpách, jehož přežití závisí na zachování přirozených krkonošských horských bučin.

Abstrakt anglicky:

An endemic landsnail subspecies from the Krkonoše Mts (Krkonoše in Czech, Karkonosze in Polish),
Cochlodina dubiosa corcontica (Brabenec 1967), has not been studied since the description of this taxon. We have
performed a phylogenetic analysis based on the mitochondrial gene for the 16S rRNA, which confirmed close relationship
between the Alpine nominotypical subspecies C. d. dubiosa and C. d. corcontica. Common Central European
species C. laminata seems to be a close relative to C. dubiosa, and our study indicates their potential hybridization
at syntopic localities. Based on our field observations and laboratory breeding experiments, we present the
first data on ecology and life cycle of C. d. corcontica. The activity of this landsnail is strongly influenced both by
seasonality and current weather condition. We have reviewed distribution of C. d. corcontica in the Krkonoše Mts,
confirmed most previously known localities and discovered numerous new ones. Its local distribution and abundance
is determined primarily by the availability of dead wood of broadleaf deciduous trees. Two sites of suitable
fossiliferous sediments provided the Last Glacial and Holocene mollusc assemblages, but C. d. dubiosa was found
only in Subrecent layers; the age of the long-dispersal founder event of the Krkonoše Mts populations thus remains
unknown. Our study confirms that C. d. dubiosa is geographically isolated taxon with distribution far from the nominotypical
subspecies found in the Alps. Its survival depends on protection of the remaining natural mountain beech
forests in the Krkonoše Mts.

Souhrn anglicky:

The land snail Cochlodina dubiosa corcontica (Brabenec
1967) is one of the three endemic taxa of the
Krkonoše National Park. Unfortunately, no information
about this locally important taxon of the family
Clausiliidae has been provided since its description.
We are filling at least some gaps in our knowledge
by 1) performing a preliminary phylogenetic analysis
elucidating its affiliations to related taxa, 2) studying
its life cycle and basic biology in situ as well as
on individuals transferred to controlled conditions,
and 3) revising its distribution and habitat requirements
in the Krkonoše Mountains. Furthermore, we
attempted to estimate the age of the local population
by studying Holocene fossil material from suitable
sites.
A phylogenetic analysis of Central European Cochlodina
species based on the mitochondrial gene for 16S
rRNA verified that C. dubiosa corcontica is closely
related to the East Alpine nominate subspecies C. d.
dubiosa. Shared 16S haplotypes in specimens with
intermediate morphology may indicate that C. d. corcontica
hybridizes with the most common Central
European representative of the genus, C. laminata,
which is the closest relative to C. dubiosa and often
lives with it in syntopy, although an extreme morphological
variability cannot be exclude.
By a direct observation of two selected populations
over two years, we obtained the first data on the biology
of C. d. corcontica. We used colour marking on the
last whorl of the shell to determine individual growth
rate and survival. In the field as well in the laboratory,
we observed the course of reproduction during a year.
The growth rate varies substantially both between
different sites in the Krkonoše Mountains as well as
within the same population. This is probably caused
by different microclimatic conditions that may affect
different individuals even within a small scale. The
life span of C. d. corcontica cannot be determined
from our short observation period, but it is certainly
at least several years. The activity and reproduction
of this taxon seems to reflect the current weather
fluctuations as well as the seasonality. Mating were
observed throughout the whole period of snail activity,
from April to October. The mating typically results
in one clutch only, but we also recorded two clutches
indicating reciprocal fertilization. We have also noted
cannibalism on eggs, which can be explained by the
lack of calcium in the environment.
We selected from the geological maps potentially
suitable sites for the mollusc fossilization, situated on
crystalline limestone in the foothills of the Krkonoše
Mountains. Here, at two localities in Lánov and Horní
Maršov, we dug a standard 80 cm wide profiles in the
Late Glacial and Holocene colluvium and from the
lithologically distinguishable layers we took samples
from which we obtained communities of subfossil
land snail shells. The aim was to find the oldest
occurrence of C. d. corcontica and thus estimate
the timing of its presence at the studied sites. However,
because of an unsuitable fossilization situation,
C. d. corcontica was found only in subrecent layers,
so the age of this isolated population remains unresolved.
Considering that this taxon has never been
recorded in numerous well-studied Holocene mollusc
successions between the Alps and the Krkonoše
Mountains, we consider C. dubiosa corcontica a geographically
isolated taxon founded by a long-distance
dispersal event.
We have verified presence of C. dubiosa corcontica
at most previously known localities. Based on the
vegetation maps, we also selected additional potentially
suitable sites across the Krkonoše Mountains.
This way, we have recorded numerous new localities
with its presence, especially in the eastern part
of the range. It thus seems that population of C. dubiosa
corcontica in the Krkonoše Mountains is stable.
The occurrence of this endemic taxon requires the
presence of dead wood of broadleaf deciduous trees
(which should be left on the forest floor). Cochlodina
dubiosa corcontica, being a local endemic, may
thus serve as the flagship taxon for conservation of
the remains of natural beech forests in the Krkonoše
Mountains.

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