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1.
LEDERGERBER STEPHAN; BAMINGER HELMUT; BISENBERGER AGNES; KLEEWEIN DORIS; SATTMAN HELMUT; BAUR BRUNO 《Journal of Molluscan Studies》1997,63(1):1-8
Resting-site preference and patterns of spatial distributionwere examined in the sympatric land snails Arianta arbustorumand A. chamaeleon on two opposite slopes in the south-easternAlps, Austria. The two slopes did not differ in proportion ofA. arbustorum and A. chamaeleon (74.4% vs. 25.6% on the NNE-exposedslope and 68.3% vs. 31.7% on the SSW-exposed slope). Individualsof both species showed aggregated dispersion patterns. The nearest-neighbourmethod indicated that in both species snail aggregations predominantlyconsisted either of A. arbustorum or A. chamaeleon on the NNE-exposedslope with a mosaic of rocks and distinct patches of differentplants. On the SSW-exposed slope, which was less variable invegetation cover, snail aggregations consisted of conspecificand hetero-specific individuals. Juvenile and adult A. arbustorumpreferred to rest attached to leaves of Adenostyles alliariae,but avoided rock surfaces and patches of grass on the NNE-exposedslope. In contrast, juvenile and adult A. chamaeleon preferentiallyrested on rock surfaces, and also avoided grass patches. Juvenileand adult A. chamaeleon did not differ in resting-site preference,whereas small differences in resting sites were observed betweenjuvenile and adult A. arbustorum. Differences in resting-sitepreference is one way of niche differentiation which may allowindividuals of the two Arianta species to coexist. (Received 14 March 1996; accepted 8 July 1996) 相似文献
2.
Hubert E. Arter 《Evolution; international journal of organic evolution》1990,44(4):966-980
The alpine snail Arianta arbustorum (Pulmonata, Helicidae) was sampled along an 8-km contour line in the Swiss Alps orthogonal to well-known altitudinal clines in life history and shell traits. The allele frequencies and the morphs of 16 populations were compared with habitats. Two hypotheses about the recolonization of the mountain slopes after the last glaciation were tested against the present population structure. The allele frequencies are best explained by the spatial structure whereas the morphs are better explained by the habitats. The genotypic distances point to a historical explanation by recolonization processes, the phenotypical dissimilarities to a selectionistic interpretation of the present distribution of the populations. The following conclusions are from the study of the spatial relationship and the gene flow paths for A. arbustorum at Mount Martegnas: (1) Streams are the main gene flow paths; gene flow is low, allowing differentiation of local populations. (2) Morphs and habitats are correlated, but the interpretation has to be made carefully. The spatial dependence of habitats has to be included into the analysis of selection. (3) The random assumption for gene flow of A. arbustorum is not a spatial isolation-by-distance model, but a functional isolation-by-distance model, assuming gene flow over the drainage system. 相似文献
3.
Arianta arbustorum is a European land snail, occurring in bothlowland and mountainous regions. Its shell is usually globular,which makes the species aberrant among the Campylaeinae in shellshape, habitat, and wide, not exclusively montane range. Withincreasing altitudes, the shells usually decrease in size andbecome more conical. However, in some mountain stocks thereare populations with depressed shells, provided with an openumbilicus. This form (subspecies) is only known from formerPleistocene refugia. It is hypothesized that in the Pliocene, the primary montaneA. arbustorum, with a depressed shell, entered an additional,adaptive zone, while conquering damp lowland habitats. Thisresulted in an enormous range extension. In the new habitata different (globular) shell shape evolved and the species becamepolytypic. The subsequent glaciations wiped out most of theoriginal montane A. arbustorum with depressed shells. Wherethis had occurred, post-Pleistocene re-colonizing conspecificsnails with globular shells, found vacant territory and coulddevelop the dines mentioned before. The invading populationsdid not regain the original, montane, depressed shell shape.This shape was only retained in a few refugia, where the populationssurvived amidst the glaciers. (Received 9 February 1990; accepted 31 May 1990) 相似文献
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The mitochondrial genomes of Cepaea nemoralis can differ widelybetween individuals in the same population. Various hypothesishave been proposed to account for this diversity, includingunusually fast evolution and the retention of deep lineagesin sub-divided populations. Another possibility is that pulmonatemitochondria are inherited in the doubly uniparental mode, asin Mytilus, allowing separate maternal and paternal lineagesto coexist. In Mytilus, separate lineages may differ by as muchas 20% and may pre-date the origin of the species carrying them. Until now, mitochondrial inheritance has not been studied inany molluscan group except the bivalves. I have investigatedit in C. nemoralis through a series of matings, and assayedindividuals for evidence of heteroplasmy. In five matings, mitochondrialinheritance was maternal, and no heteroplasmic individuals weredetected. The maintenance of the divergent haplotypes can notbe explained by doubly uniparental inheritance. (Received 30 April 1999; accepted 6 July 1999) 相似文献
6.
—Protein synthesis in an identified molluscan neurosecretory cell of the land snail, Otala lactea was examined using three different types of polyacrylamide gel electrophoresis. Cells taken from active snails synthesized specific low molecular weight proteins while those from aestivated snails did not. Most of the newly synthesized low molecular weight proteins in the active snails were lost from the cell body when the preparations was chased for 19 h in label-free enriched medium in the presence of anisomycin, an inhibitor of protein synthesis. If colchicine, a blocker of axonal transport, was included in the chase medium, the proteins present following a pulse were largely replaced by smaller molecular weight species. The results suggest that specific low molecular weight proteins are converted to smaller species and then transported from the cell body. 相似文献
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Activity and inactivity (dormancy) periods of the land snailHelix aspena MÜller were monitored at monthly intervalsduring two years in two natural populations in Galicia (NW-Spain),one m an area of Mediterranean climatic influence and anotherin an Atlantic -climate area The annual activity cycles of Haspena in Galicia are consistent with latitudinal adjustmentsof the life cycle of this species which shows a very wide distributionrange, but also showed some special features related to theparticular microclimate of each locality (Received 4 December 1995; accepted 6 May 1996) 相似文献
9.
Food consumption by juvenile and adult specimens Limicolariaflammea was measured as dry weight of food eaten. The snailwas fed weekly for 15 months on four types of food (lettuce,potato, apple and carrot) and chalk provided, hence an opportunityto select for food. Juvenile snails showed greater selectivitydepending on whether the food was needed for somatic growthor reproduction. On the other hand, when fed exclusively onone each of the same food items and given no opportunity tochoose, the snails grew better on the same food items they selectedin the choice experiment. The absorption efficiencies (AD) werehigh, the utilisation efficiency (ECI) was 113% and showeddistinct peaks corresponding to egg production. Values for ECDwere 1.2515.5%. Variation in growth rates was due mainlyto utilisation efficiencies of the four foods tested. Largeamounts of chalk were eaten during the period of somatic growthand greatly reduced during the reproductive phase of L. flammea.The significance of these findings to the snails ecology isdiscussed. (Received 9 April 1991; accepted 11 June 1991) 相似文献
10.
This study reports the results of mate-choice experiments betweenresident and non-resident individuals of the simultaneous hermaphonteland snail Helix aspersa. Snails from different sites differedin their mating proclivity, which resulted in non-random matingin laboratory mate-choice tests. Those snails with the highermating propensity therefore tended to mate with their own typeand tended to be chosen as partner because they were also activelyseeking mates. Keeping snails under crowded conditions did noteffect a lasting influence on mating behaviour in laboratorytests, despite the decline in copulatory behaviour under crowdedfield conditions. (Received 7 November 1994; accepted 31 August 1995) 相似文献
11.
Land snail faunas from maquis and phrygana sites on the islandsof Naxos and Crete, and from the eastern Peloponnese were sampledto determine the relationships between local (site) and regionaldiversities. Mean site diversities are similar in each region.In both the Peloponnese and Crete, however, these representa much lower proportion of total diversity than is the casefor forest faunas from more northerly parts of Europe. The smallisland of Naxos has more uniform faunas. Some of this between-sitediversity is a product of habitat heterogeneity, but most isa product of small-scale biogeographical differentiation. Despitethe short (c. 250km) distances between regions, the faunas ofeach region differ far more than do faunas from forests in northernEurope spread over much greater distances. Nearly 80% of speciesrecorded were found in only one region. These results are comparedwith those from elsewhere, and discussed in the context of thehigh diversity of snail faunas in the mediterranean area generally. (Received 5 May 1999; accepted 1 July 1999) 相似文献
12.
In the land snail H. aspersathe enzyme LAP has two loci, LAP-1and LAP-2, both of which arc monomeric enzymes under the controlof multiple alleles, the alleles being codominant. None of theobserved ratios in the pheno types in the experimental progenywere significantly different from Mendelian expectation.
* Present Address: Bournside School, Cheltenham, Glos. (Received 1 September 1981; 相似文献
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Feeding of the land snail Helix aspersa (Müller) was observedat monthly
intervals. Three natural populations in Galicia (NW-Spain)were studied. At two sites only a few
plants constituted thebulk of the diet and in spring the snails' diet had the highestdiversity
(H'). In the third population feeding and distributionof Helix aspersa
(Müller) were observed in a small plotwith permanent patches of Urtica dioica.
Nearly one half offeeding snails fed upon Urtica dioica. Most of the other observations
wereon Mentha suaveolens, Ranunculus repens and Gramineae. The diversity
ofthe snails' diet showed seasonal variation with the maximumin the autumn months.
Comparison between the availability ofthe different plant species and their contribution to the
snails'diet showed that the snails did not eat at random; Urtica dioicawas eaten
much more than expected from its occurrence and grasseswere strongly under-represented in the
snails' diet. Temporalchanges of availability were significantly correlated with the
amountseaten in the case of Urtica, but not for the other food plants.The distribution of
the snails in the plot was significantlycorrelated with that of Urtica. Chemical analyses
of the foodplants revealed Urtica as the species with the higher protein,ash and calcium
contents. The strong preference of Helix aspersafor Urtica dioica could be
explained by the value of Urticaas food or by its suitability as habitat for the snails. The
largestproportions of green material in the snails' diet occurred inthe spring and juveniles
ate more green material than adultsin the three populations. (Received 16 March 1998; accepted 30 November 1998) 相似文献
15.
The pulmonate snail Arianta arbustorum from the Swiss Alps wasaged using thin sections of the shell margins cut from markedindividuals. Shell layers at the apertural lip and growth breaksin the juvenile can give a reliable estimate of age. (Received 16 May 1986; 相似文献
16.
Egg cannibalism by hatchlings has been demonstrated in somepulmonate land snails; this behaviour is promoted by a highhatching asynchrony within the egg-batch. Under laboratory conditions,the percentage of new-born snails Helix aspersa having cannibalisedunhatched eggs was not influenced by the soil factor: about70% of them ingested one egg within their first four days oflife whether soil was present or not. The propensity to eggcannibalism in hatchlings of H. aspersa increased with egg density.However, most of the new-born hatchlings consumed a single eggduring the four days following hatching, and only exceptionallytwo. The consumption of one egg increased the snails wet weightby 38.7% within four days. A weak ingestion of soil componentsalso occurred, but it induced a growth that was three-timesless than that due to the consumption of an egg. In addition,the survival of newly hatched snails maintained under non-dehydratingthermohygrometric conditions was high, even when they were submittedto four days food-deprivation. (Received 22 July 1999; accepted 24 November 1999) 相似文献
17.
A. J. Gaston 《Ibis》1974,116(4):432-450
The paper describes variation among species of the genus Phylloscopus in weight, relative wing-, tail-, tarsus-, and bill-length, tail/wing ratio and degree of roundness of the wing, wing formula, emargination, and plumage colour. This variation is compared with differences in niche preference within the genus, and relationships between niche, feeding strategies, and morphology are suggested. It is concluded that evolution within the genus has taken place mainly through the development of different feeding strategies, to suit the structural properties of different niches, without altering the range of size of the prey. The genus Sylvia is treated briefly in order to provide comparison, and other genera of Sylviinae are discussed where parallel adaptation seems likely. 相似文献
18.
Vassilis Douris Robert A. D. Cameron George C. Rodakis Rena Lecanidou 《Evolution; international journal of organic evolution》1998,52(1):116-125
The land snail genus Albinaria exhibits an extreme degree of morphological differentiation in Greece, especially in the island of Crete. Twenty-six representatives of 17 nominal species and a suspected hybrid were examined by sequence analysis of a PCR-amplified mitochondrial DNA fragment of the large rRNA subunit gene. Maximum parsimony and neighbor-joining phylogenetic analyses demonstrate a complex pattern of speciation and differentiation and suggest that Albinaria species from Crete belong to at least three distinct monophyletic groups, which, however, are not monophyletic with reference to the genus as a whole. There is considerable variation of genetic distance within and among “species” and groups. The revealed phylogenetic relations do not correlate well with current taxonomy, but exhibit biogeographical coherence. Certain small- and large-scale vicariance events can be traced, although dispersal and parapatric speciation may also be present. Our analysis suggests that there was an early and rapid differentiation of Albinaria groups across the whole of the range followed by local speciation events within confined geographical areas. 相似文献
19.
Jan Sauer Bernhard Hausdorf 《Evolution; international journal of organic evolution》2009,63(10):2535-2546
We investigated the importance of sexual selection in facilitating speciation in a land snail radiation on Crete. We used differences in the genitalia of the Cretan Xerocrassa species as potential indices of sexual selection. First, we rejected the hypothesis that differences in the genitalia of the Xerocrassa species can be explained by genetic drift using coalescent simulations based on a mitochondrial gene tree. Second, we showed that there is no evidence for the hypothesis that the differences in the genitalia can be explained by natural selection against hybrids under the assumption that this is more likely in geographically overlapping species pairs and clades. Third, we showed that there is a positive scaling between male spermatophore-producing organs and female spermatophore-receiving organs indicating sexual coevolution. The spermatophore enables the sperm to escape from the female gametolytic organ. Thus, the coevolution might be a consequence of sexual conflict or cryptic female choice. Finally, we showed that the evolution of differences in the length of the flagellum that forms the tail of the spermatophore is concentrated toward the tips of the tree indicating that it is involved in speciation. If speciation is facilitated by sexual selection, niches may remain conserved and nonadaptive radiation may result. 相似文献