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The subterranean environment of Christmas Island is diverse and includes freshwater, marine, anchialine, and terrestrial habitats. The cave fauna comprises swiftlets, and a diverse assemblage of invertebrates, both terrestrial and aquatic, which includes a number of rare and endemic species of high conservation signicance. At least twelve species are probably restricted to subterranean habitats and are endemic to Christmas Island. Previously poorly known, the cave fauna of Christmas Island is a signicant component of the island's biodiversity, and a signicant cave fauna province in an international context. The cave fauna and habitats are sensitive to disturbance from a number of threatening processes, including pollution, deforestation, mining, feral species and human visitors.
In southwestern Australia, karst features occur in geological formations other than the coastal calcarenites of the Tamala Limestone. The Noondine Chert was formed by the silicification of carbonate rocks and contains relict carbonate textures and palaeokarst features such as intense brecciation and the presence of subsurface voids. This geological formation is an important aquifer to the east of the Perth Basin where groundwater resources are otherwise limited, and the aquifer is highly vulnerable to contamination from agricultural land use. The Noondine Chert may also contain a rich stygofauna. This has not been taken into account in groundwater protection policies, and needs to be assessed as a matter of urgency.
The relief of the Polish Jura Chain developed since Paleogene under climatic conditions changing considerably. Their main components are a peneplain crowned by numerous monadnocks, generated as hard-rocks on Upper Jurassic massive limestones (bioherms, carbonate buildups) surrounded by less resistant platy and bedded limestones of the same age. After the Miocene tectonic phase and following karstification deep valleys dissected the top surface of the plateau and cave levels connected with rocky terraces had been formed. During the Pleistocene the periglacial climate accelerated the congelifraction and relaxation of monadnocks. The modification of landforms and the environment in last ten thousand years, indicated by assemblages of molluscs was controlled by both climatic and anthopogenic factors. The geo- and biodiversity closely related to one another are still under the nature protection.
Understanding past environmental changes in tropical rainforests is extremely important in order to assess the response of such environments to present and future climatic changes and understand causes and the present patterns of biodiversity.
Earlier hypothesis on the origin of biodiversity have stressed the role of past climatic changes in promoting speciation. According to the “refuge hypothesis” (Haffer, 1982), dry periods could have led to forest fragmentation, isolating more humid forested zones (called refuges) within an environment largely dominated by savannas. The refuge hypothesis does not assign timescales for rainforest fragmentation, although recent studies have suggested that speciation could have occurred over timescales of millions of years (Knapp and Mallet, 2003). Although the focus of heavy criticism (Colinvaux, et a., 2000), the refuge hypothesis has generated a large amount of research. In general, pollen studies (Colinvaux, et a., 1996, Haberle and Maslin, 1999) tend to support a continuous forest cover throughout late Quaternary climatic shifts, although large variations in rainfall have also been demonstrated by other pollen and isotopic studies (van der Hammen and Absy, 1994; Maslin and Burns, 2000).
Amazon and Atlantic rainforests are the two major forested zones in South America. Amazon rainforest, the largest rainforest in the world, comprise a total original area of 4.1 million km2 and is renowned for hosting the large biodiversity in the world (30% of all the world’s known plant and animal species). Atlantic rainforest, also a biodiversity hotspot, occurs along the coast and has been subjected to heavy deforestation since European arrival. Nowadays only c. 7% of its original forested area of 1.3 million km2 remains. These two rainforests are separated by drought-prone semi-arid northeastern (NE) Brazil. Our study does not address the refuge hypothesis directly although it sheds new light on the dynamics of forest expansion in the past as well as indicates alternative ways of promoting speciation. It has long been hypothesized, due to botanical (Mori, 1989; Andrade-Lima, 1982) and faunistic (Costa, 2003) similarities, that the Amazon and Atlantic rainforests were once linked in the past. Although numerous connecting routes have been postulated (Bigarella, et al, 1975; Por, 1992; De Oliveira, et al, 1999), the timing of forest expansion and their possible recurrence have remained elusive.
The study area lies in the driest portion of NE Brazil “dry corridor”, close to the village of Laje dos Negros, northern state of Bahia. Mean annual precipitation is around 480 mm and potential evapotranspiration is in excess of 1,400 mm/year (Fig.1). Present vegetation comprises a low arbustive scrubland known locally as caatinga. The area contains a well-developed underground karst (Auler and Smart, 2003) with abundant secondary calcite precipitates, both underground (speleothems) and on the surface (travertines).
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