Search results for "Systematics"

Resembling a Viper: Implications of Mimicry for Conservation of the Endangered Smooth Snake

2014

The phenomenon of Batesian mimicry, where a palatable animal gains protection against predation by resembling an unpalatable model, has been a core interest of evolutionary biologists for 150 years. An extensive range of studies has focused on revealing mechanistic aspects of mimicry (shared education and generalization of predators) and the evolutionary dynamics of mimicry systems (co-operation vs. conflict) and revealed that protective mimicry is widespread and is important for individual fitness. However, according to our knowledge, there are no case studies where mimicry theories have been applied to conservation of mimetic species. Theoretically, mimicry affects, for example, frequency…

Long-term changes in collembolan communities in grazed and non-grazed abandoned arable fields in Denmark

2004

Summary In order to explore long-term changes in microarthropod communities after introduction of livestock grazing in abandoned fields with herb–grass vegetation at Mols, E. Jutland, Denmark, soil and litter samples were collected from 7 pairs (blocks) of grazed and non-grazed plots over a period of 14 years. Sampling began just before fencing and initiation of cattle and sheep grazing in the spring of 1985. The total material included 76 collembolan species; 65 and 68 species were recorded in the grazed and non-grazed plots, respectively. The number of species recorded at individual sampling dates fluctuated considerably through the period. In the vegetation/litter layer the mean number o…

Does population genetic structure support present management regulations of the northern shrimp (Pandalus borealis) in Skagerrak and the North Sea?

2014

AbstractPopulation structuring in the northern shrimp (Pandalus borealis) in the North Sea area (including Fladen and Skagerrak) was studied by microsatellite DNA analyses. Screening 20 sample locations in the open ocean and Skagerrak fjords for nine loci revealed low, but significant genetic heterogeneity. The spatial genetic structure among oceanic samples of Skagerrak and the eastern North Sea was weak and non-significant, consistent with the current management regime of one single stock. However, Skagerrak fjord samples generally displayed elevated levels of genetic differentiation, and significantly so in several pairwise comparisons with other fjords and oceanic samples. Although the …

Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz

1998

A sediment core from a Mediterranean karstic lake was studied through its pollen, diatom, chydorid, ostracod, charcoal and authigenic mineral composition. Information about environmental history recorded in the sediment sequence since the Middle Ages is presented. The main fluctuations of water volume and trophic status of the lake occurred during periods of great change in land management and during climatic cold phases. The synergetic effect of these two factors led to a high water level phase and triggered a rising of the trophic level which produced meromixis. The onset of meromictic conditions at about 1700 AD coincides with the Maunder minimum in the Little Ice Age as well as with a p…

Ecology of Cryptomonas at the chemocline of a karstic sulfate-rich lake

2001

In a study from October 1989 to January 1992, a dense population ofCryptomonas cf. erosa (maximum density 38 000 cells mL–1) consistently developed at the chemocline of Lake Arcas, central Spain,where sharp physical and chemical gradients occurred during stratification. This population developed following the establishment of vertical water stratification and declined when the lake was near autumnal mixis. Population growth in situ, attributable to photosynthetic adaptation to low light intensities rather than to phagotrophy, causes these algal maxima. The population densities and net growth rates of C. cf. erosa in situ were influenced by the coexisting phototrophic prokaryotes at the che…

Curvilinear interspecific density-range size relationship in small mammals in Finland

2013

ABSTRACTAim Macroecological patterns have mainly been depicted as atemporal, withexisting research covering only short time periods. One fundamental pattern inmacroecology is the interspecific relationship between local abundance andregional range size, which is generally considered to be positively linear. Here,we examine structural details of the relationship between abundance and rangesize in cyclic populations of small mammals and its long-term temporal varia-tion.Location Finland.Methods We analysed 39 years of trapping data of Rodentia and Soricomor-pha collected in field and forest habitats across Finland. Abundance was mea-sured as the mean population density of individuals, and range…

Response to comments by Cardinale et al. on “Local cod (Gadus morhua) revealed by egg surveys and population genetic analysis after longstanding depl…

2019

Risk of Local Extinction of Odonata Freshwater Habitat Generalists and Specialists

2014

Understanding the risk of a local extinction in a single population relative to the habitat requirements of a species is important in both theoretical and applied ecology. Local extinction risk depends on several factors, such as habitat requirements, range size of species, and habitat quality. We studied the local extinctions among 31 dragonfly and damselfly species from 1930 to 1975 and from 1995 to 2003 in Central Finland. We tested whether habitat specialists had a higher local extinction rate than generalist species. Approximately 30% of the local dragonfly and damselfly populations were extirpated during the 2 study periods. The size of the geographical range of the species was negati…

Population dynamics of Cyclotella ocellata (Bacillariophyceae): endogenous and exogenous factors

1999

Population dynamics of Cyclotella ocellata PANTOCSEK were examined from 1991 to 1993 in an oligo-mesotrophic, gravel-pit lake near Madrid (Spain). Monthly and daily sampling was carried out to track seasonal- and auxosporulation dynamics, respectively. This species was the most abundant planktonic diatom in the lake. The population increased steadily in spring until the seasonal peak (3.8.10 6 ind/ L in April) and then abundance declined slowly through late winter. Time series techniques showed that the seasonal dynamics were driven by exogenous factors: there was a relationship between Cyclotella abundance and the chemical environment, both TP (synchronic) and SRSi (with delay). Auxosporul…

Relationship between egg features and maternal body size in the simultaneous hermaphrodite Oxynoe olivacea (Mollusca, Opisthobranchia, Sacoglossa)

2005

This paper provides information on spawn morphology and egg features of the stenophagous planktotrophic Mediterranean sacoglossan Oxynoe olivacea. Smith and Fretwell’s hypothesis, predicting that individuals of the same population growing in the same environmental conditions and varying in size should spawn eggs of a constant size, was tested in a population of O. olivacea living in the Straits of Messina. To determine whether (a) spawn mass size, (b) total egg number per spawn, and (c) egg size were related to parent size of O. olivacea, 21 egg masses (seven egg masses deposited by seven different 20 mm animals, seven egg masses deposited by seven different 25 mm animals and seven egg mass…