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Mass Occurrence (mass + occurrence)
Selected AbstractsMass occurrence of the recent brachiopod Magellania venosa (Terebratellidae) in the fjords Comau and Reñihué, northern Patagonia, ChileMARINE ECOLOGY, Issue 3 2008Günter Försterra Abstract Mass occurrences of the terebratellid brachiopod Magellania venosa with more than 200 individuals·m,2 are reported from the fjords Comau and Reñihué in the northernmost region of the Chilean fjordland, whereas more southern fjords do not show these high numbers of the largest living brachiopod. This is an exception to earlier observations that the abundance of M. venosa on the Chilean shelf is positively correlated with increasing latitude. As the sympatric scleractinian coral Desmophyllum dianthus also occurs in unusually high numbers in the fjords Comau and Reñihué, the hydrographical regime and its associated environmental conditions in these fjords may be responsible for these mass occurrences. [source] Heimische Orchideen in urbanen Biotopen,FEDDES REPERTORIUM, Issue 5-6 2008W. Heinrich Dr. In den letzten Jahren häufen sich Angaben über das Auftreten von Orchideen an sekundären und vor allem auch urbanen Standorten. Durch diese auffällige Biotoperweiterung muss die Aussage, dass Orchideen als Anzeiger intakter Lebensräume gelten, relativiert werden. Gerade als konkurrenzschwache Arten haben dabei vermutlich euryöke Orchideen mit einer relativ breiten ökologischen Amplitude auf jungen, anthropogen entstandenen Böden, zumindest über eine begrenzte Zeit, Chancen einer Erstansiedlung, teilweise mit Massenvorkommen. Zahlreiche konkrete Beispiele werden dafür aus Deutschland mit Schwerpunkt Jena und Thüringen aufgeführt. Es wird belegt, dass vor allem klonal wachsende Orchideen (Epipactis helleborine, Listera ovata, Cephalanthera damasonium) sowie die autogame Ophrys apifera ihre ökologische Amplitude und ihre Biotopbindung erweitert haben. Man sollte aber auch in diesem Zusammenhang Aspekte eines Klimawandels berücksichtigen. Lohnenswert erscheint es, diese Prozesse weiter zu verfolgen, auf neue Fundorte an urbanen Standorten in Städten und Dörfern zu achten. Wichtig aber ist es, künftig die Zusammenhänge zwischen Keimungsbedingungen, Individualansiedlung und Populationsbildung im Wechselspiel mit Klima und Bodeneigenschaften (und ihren darin siedelnden Organismen) gezielt in solchen Biotopen zu erforschen. Weitere populationsökologische Studien sind daher dringend erforderlich, um diese neuen Prozesse folgerichtig interpretieren zu können. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Indigenous orchids in urban biotopes During the last years informations about the appearance of orchids multiplied in secondary and urban locations. The statement that orchids count as an indicator of intact habitats must be qualified by this remarkable biotope extension. Even as competition-weak species have, besides, presumably euryoecious orchids with relatively spread ecological amplitude on young, anthropogen resulted soils, at least on a restricted time, chances of a first settlement, partially with mass occurrence. Numerous precise examples from Germany with main focus Jena and Thuringia are mentioned for it. It is proved that, above all, klonal growing orchids (Epipactis helleborine, Listera ovata, Cephalanthera damasonium) as well as autogame Ophrys apifera her ecological amplitude and her biotope links have extended. Worthwhile appears to investigate these relations between germination terms, individual colonization, and development of population in the interaction with climate and soil qualities (and her organisms settling in it) concerted in urban biotopes. Further population-ecological studies are urgently necessary to interpret these new processes consistently. [source] A Skate in the Lowermost Maastrichtian of Southern SwedenPALAEONTOLOGY, Issue 3 2001Mikael Siverson A new skate, Walteraja exigua gen. et sp. nov., is described from the lowermost Maastrichtian Belemnella lanceolata Zone of Balsvik quarry, Kristianstad Basin, southern Sweden. It is the earliest known skate with a largely modern tooth morphology and the only known pre-Cenozoic rajoid displaying a very marked gynandric heterodonty, comparable to that in many living forms. The occurrence of W. exigua in the basal Maastrichtian at Balsvik coincides with a mass occurrence of the small ,deep-water' squaloid shark Proetmopterus hemmooriensis. Most living skates, and virtually all extant squaloids closely related to P. hemmooriensis, inhabit deep and/or cool water environments and do not occur in warm temperate to tropical coastal waters. The Walteraja/Proetmopterus association in a marginal, relatively shallow-water facies of the B. lanceolata Zone adds to other, recently described, unexpected occurrences of Late Cretaceous rajoids and etmopterids/centroscymnids in warm temperate to subtropical shelf environments. [source] Short-term transformation of matrix into hospitable habitat facilitates gene flow and mitigates fragmentationJOURNAL OF ANIMAL ECOLOGY, Issue 6 2007NIELS BLAUM Summary 1Habitat fragmentation has major implications for demography and genetic structure of natural plant and animal populations as small and isolated populations are more prone to extinction. Therefore, many recent studies focus on spatial fragmentation. 2However, the temporal configuration of suitable habitat may also influence dispersal and gene flow in fragmented landscapes. We hypothesize that short-term switching of inhospitable matrix areas into suitable habitat can mitigate effects of spatial fragmentation in natural and seminatural ecosystems. 3To test our hypothesis, we investigated the hairy-footed gerbil (Gerbillurus paeba, Smith 1836), a ground-dwelling rodent, in fragmented Kalahari savannah areas. Here, rare events of high above mean annual rainfall suggest short-term matrix suitability. 4During the field survey in ,matrix' areas in the Kalahari (shrub encroachment by heavy grazing) we never observed the hairy-footed gerbil in years of average rainfall, but observed mass occurrences of this species during rare events of exceptionally high rainfall. 5In a second step, we developed an agent-based model simulating subpopulations in two neighbouring habitats and the separating matrix. Our mechanistic model reproduces the mass occurrences as observed in the field and thus suggests the possibly underlying processes. In particular, the temporary improvement in matrix quality allows reproduction in the matrix, thereby causing a substantial increase in population size. 6The model demonstrates further how the environmental trigger (rainfall) impacts genetic connectivity of two separated subpopulations. We identified seasonality as a driver of fragmentation but stochasticity leading to higher connectivity. 7We found that our concept of temporal fragmentation can be applied to numerous other fragmented populations in various ecological systems and provide examples from recent literature. We conclude that temporal aspects of fragmentation must be considered in both ecological research and conservation management. [source] Mass occurrence of the recent brachiopod Magellania venosa (Terebratellidae) in the fjords Comau and Reñihué, northern Patagonia, ChileMARINE ECOLOGY, Issue 3 2008Günter Försterra Abstract Mass occurrences of the terebratellid brachiopod Magellania venosa with more than 200 individuals·m,2 are reported from the fjords Comau and Reñihué in the northernmost region of the Chilean fjordland, whereas more southern fjords do not show these high numbers of the largest living brachiopod. This is an exception to earlier observations that the abundance of M. venosa on the Chilean shelf is positively correlated with increasing latitude. As the sympatric scleractinian coral Desmophyllum dianthus also occurs in unusually high numbers in the fjords Comau and Reñihué, the hydrographical regime and its associated environmental conditions in these fjords may be responsible for these mass occurrences. [source] | ||||||||||