38 research outputs found
Formation of the Isthmus of Panama
Get PDFThe formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed manymillions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways,withformationof theIsthmus of Panama sensustricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.Facultad de Ciencias Naturales y Muse
Urban coral reefs: Degradation and resilience of hard coral assemblages in coastal cities of East and Southeast Asia
Get PDF© 2018 The Author(s) Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including âreef compressionâ (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas
Overleving og vekst pÄ utsett elvemusling Margaritifera margaritifera i Audna, Vest-Agder
Get PDFAudna er ei gamal âperleelvâ, der forsuring tok knekken pĂ„ dei siste elvemuslingane om lag 1950. I 1991, med kalking frĂ„ 1985, vart det sett ut 250 elvemuslingar pĂ„ fire stasjonar i Audna, der 200 av dei var individmerka. Ein stor flaum 1.12.1992 fĂžrde vekk mesteparten av elvemuslingane pĂ„ stasjonane 1-3. Det er gjort opptellingar av muslingane i 1992, 1993 og 1994 og registreringar i 1996, 1999, 2001 og 2007. I 1996 vart det registrert gjenfunn pĂ„ 8, 32, 20 og 74% av dei utsette elvemuslingane pĂ„ stasjonane 1-4. I 2007 var det gjenfunn av 18 og 68% av elvemuslingane pĂ„ stasjonane 3 og 4. SjĂžlvetablerte og smĂ„ muslingar er minst utsette for Ă„ bli fĂžrde vekk ved store flaumar. Tilveksten pĂ„ elvemuslingane pĂ„ stasjon 3 har vore markert betre enn pĂ„ stasjon 4, truleg pga. rolegare straumtilhĂžve ved stasjon 3. I tidsrommet 1991-2007 var tilveksten 1,3 mm pr. Ă„r pĂ„ stasjon 3 og 0,1 mm pr. Ă„r pĂ„ stasjon 4. Fiskegjeller er undersĂžkt for glochidielarver, men med negativt resultat. Fiskegjeller av laks og aure frĂ„ vĂ„ren 2007 er analysert for aluminium (Al) og jern (Fe). Resultata viste hĂžge verdiar for bĂ„de stasjon 3 og 4. Det er gjeve rĂ„d for eventuell gjeninnfĂžring eller overfĂžring av elvemuslingar
Growth and size of Triturus vulgaris and T. cristatus (Amphibia) in different parts of Norway
No full textMicrohabitat selection and feeding relations of smooth and warty newts, Triturus vulgaris and T. cristatus, at an upland pond in mid-Wales
No full textSexual size and shape dimorphism in two species of newts, Triturus cristatus and T. vulgaris (Caudata: Salamandridae)
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