Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Botanists, ecologists and evolutionary biologists are familiar with the astonishing species richness and endemism of the fynbos of the Cape Floristic Region and the ancient and unique flora of the kwongkan of south-western Australia. These regions represent old climatically-buffered infertile landscapes (OCBILs) that are the basis of a general hypothesis to explain their richness and endemism. However, few ecologists are familiar with the campo rupestre of central and eastern Brazil, an extremely old mountaintop ecosystem that is both a museum of ancient lineages and a cradle of continuing diversification of endemic lineages. Diversification of some lineages of campo rupestre pre-dates diversification of lowland cerrado, suggesting it may be the most ancient open vegetation in eastern South America. This vegetation comprises more than 5000 plant species, nearly 15 % of Brazil’s plant diversity, in an area corresponding to 0.78 % of its surface. Reviewing empirical data, we scrutinise five predictions of the OCBIL theory, and show that campo rupestre is fully comparable to and remarkably convergent with both fynbos and kwongkan, and fulfills the criteria for a classic OCBIL. The increasing threats to campo rupestre are compromising ecosystem services and we argue for the implementation of more effective conservation and restoration strategies.

/pdf/ecology-and-evolution-of-plant-diversity-in-the-endangered-1q7wdjzpp8.pdf

Ecology and evolution of plant diversity in the endangered campo rupestre: a neglected conservation priority

This paper presents and reviews the processes responsible for the distribution and formation of regolith and associated landscapes of the Yilgarn Craton and highlights their implications for mineral exploration. It provides an analysis of regolith geology investigations that were conducted in many districts of contrasting contemporary geomorphic and climatic conditions.The Yilgarn Craton is composed of Archaean rocks, predominantly granitoids, that are crossed by north‐northwest‐trending belts of greenstones. It has an arid to humid climate at present. The gently undulating landsurface forms a partial etchplain and the topography is largely related to bedrock lithologies and a complex history of valley development and aggradation. Deep weathering has affected most lithologies and geological provinces across the craton. The depth of the weathered mantle may be as much as 150 m, but it varies considerably and rock outcrop may occur in any part of the landscape. The main factors influencing extent of weathering are rock type, mineralisation and deformation. Palaeomagnetic dating of deeply weathered regolith profiles suggest that they formed throughout the Phanerozoic.An idealised profile commonly comprises fresh bedrock, grading upwards into saprock and saprolite, commonly bleached towards the top, especially on felsic or sheared mafic rocks. This is overlain by a clay‐rich and/or quartz‐rich zone, a mottled zone and a ferruginous, bauxitic or siliceous upper zone. These horizons are formed by a combination of weathering and landscape processes. Landscape processes would have been continuous throughout the weathering period, with major environmental changes triggering particular erosional and depositional events. Thus, upper horizons, mottled zone, ferruginous duricrust and silcrete have developed in residuum, colluvium and alluvium of various ages.Weathering is the result of interaction between the hydrosphere, biosphere and lithosphere. During weathering some of the components of primary minerals are leached and secondary minerals are formed as residua. The pathways by which these minerals form are varied and complex. Biota were present in the regolith and it is likely that they and their associated chemical reactions played a significant part in the weathering process, as well as inorganic chemical processes. The final product of weathering of all rocks is a mineral assemblage of least soluble minerals (kaolinite, hematite, goethite, maghemite, gibbsite, anatase and boehmite) and the most resistant primary minerals (quartz, zircon, chromite, muscovite and talc), although neoformation of several generations of hematite, goethite, kaolinite and gibbsite may occur. Poorly crystalline minerals are an important constituent in surface or near‐surface materials. In addition, the more soluble minerals, including carbonates, sulfates and halides, occur in arid environments.The principal effects of weathering on element distributions relates leaching and retention of a range of elements to mineral transformations in the principal regolith profile horizons. However, the chemical patterns may not be consistent from profile to profile even for similar lithologies due to differences in groundwater regimes and topography. Minor and trace elements may be displaced from their primary host mineral. Thereafter, they may occur camouflaged in the newly formed secondary minerals, as major components of accessory new minerals, or in resistant minerals.In the present landscape, deeply weathered profiles may be preserved or partly eroded and buried beneath a variety of sediments. Three major regolith‐landform terrains were identified and the extents of these regolith‐landform terrains vary across the Yilgarn Craton. The first is dominated, in its upper part, by sands, ferruginous gravels and duricrust that commonly overlie mottled zones and saprolites. Ferruginous duricrust is developed in weathered Archaean bedrock and younger sediments that have been extremely weathered and/or indurated by Fe oxides. A second regolith‐landform terrain comprises saprolite with fresh rock in places. These may have been exposed by erosion of a pre‐existing weathered material, or may represent the most weathered form of the parent rock, which had never been capped with a ferruginous duricrust. A third terrain is of sediment‐dominated areas with fluvial, aeolian and/or lacustrine deposits, commonly several metres thick, that may be underlain by ferruginous duricrust, saprolite or bedrock. Sediments are highly variable in genesis, provenance, composition and thickness and were either derived from erosion of fresh and weathered Archaean bedrocks or the reworking of older pre‐existing sediments. They vary according to region, topography and age.Numerous buried palaeochannels occupy the lower parts of the landscape and are up to several hundreds of metres wide and many kilometres long. Drainage incision along palaeovalleys on the weathered landsurface resulted in development of channels that were subsequently filled with sand, lignite and kaolinite‐ and smectite‐rich sediments with lenses of ferruginous gravel. Palaeochannels are younger than the palaeodrainage system of broad, shallow valleys in which they occur and were probably incised during the final stages of rifting between Australia and Antarctica during the Early‐Middle Tertiary. Sediments were deposited under fluvial, lacustrine, estuarine and marine environments during the Middle‐Late Eocene. Further deep weathering occurred in both sediments and bedrock. Mixing occurred between the accumulating sediments and the underlying saprolite, possibly as a result of the formation of palaeosols. The collapse features and associated nodular and pisolitic materials in the underlying saprolite were probably formed during this period. Hematitic megamottles have developed in sediments and the upper part of some palaeochannel sediments contain ferruginous nodules and pisoliths. All this indicates post‐depositional weathering within the sedimentary sequence. The similarities in the nature and characteristics of palaeochannel sediments in the southern and northern regions suggest that similar conditions prevailed not only during the deposition of sediments, but also during their subsequent weathering. Parts of the palaeochannel sediments were eroded prior to deposition of Quaternary colluvium and alluvium. Colluvial, alluvial and aeolian sediments unconformably overlie palaeochannel sediments, ferruginous duricrust or saprolite. These sediments have been derived from increased erosion following the change to a more arid climate during the Late Miocene‐Pliocene, in part a result of instability caused by a reduction in the vegetative cover.A variety of soils occur in the three major regolith‐landform terrains, the nature of which is controlled largely by the parent material and erosional and depositional processes. There is a significant aeolian component in many soils, commonly in the finer fractions. Where these soils occur over basic or ultramafic rocks, the Ti/Zr ratio and quartz contents can be used to identify any aeolian contribution.Duricrusts occur in many different associations. In places, duricrusts of Fe, Si and Ca occur together in a single profile. Inland, ferruginous duricrust did not form on a simple, extensive, peneplained surface, but as a discontinuous cover on a broadly undulating plateau. It is developed on all rock types, but is particularly well developed on mafic and ultramafic bedrocks. By contrast, in the humid region of the Darling Range of the western Yilgarn, ferruginous duricrusts of various morphologies form an almost continuous sheet on all rock types. Transported hematite‐maghemite‐rich gravels at the base of the palaeochannel sequence are evidence that ferruginous duricrust existed prior to deposition of palaeochannel sediments in the Eocene. Ferruginous duricrusts have formed in residuum, in colluvium and in alluvium of various ages and are not necessarily associated with deep weathering. Thus, it is unwise to assign a single age to all ferruginous duricrusts or imply a single extensive surface of planation of continental extent. Residual duricrust (lateritic residuum) has developed from bedrock by essentially residual processes. In contrast, transported duricrusts (ferricretes) develop by impregnation and cementation of sediments by Fe oxides precipitated from groundwater, so that ferricretes have little direct relationship with the underlying rocks. In places they now form low hills because of relief inversion. Evidence of ferruginisation from the pre‐Eocene through to at least Pliocene can be seen in the arid parts of the Yilgarn Craton. However, this process is currently operating in humid regions of the Darling Range, where goethite‐rich ferricrete is forming on the edges of valley floors. Recent overprinting of ferruginous duricrusts has continued both inland and in the Darling Range. In the Darling Range, degradation of bauxitic ferruginous duricrust continues by dissolution of gibbsite and goethite. In the Kalgoorlie region, ferruginous duricrust is extensively modified by precipitation of carbonates to form calcretes.Inland with increased aridity, soil and groundwater‐related processes became dominated by gypsification, silicification and calcification. Silicification and calcification have affected a wide variety of regolith materials; calcification post‐dates silicification. There are at least two widespread episodes of silicification. One episode is related to silcrete formation and the other with red‐brown hardpan formation. It is possible that red‐brown hardpans were once more extensive, but were subsequently replaced by carbonates to form calcretes. The red‐brown hardpans are formed by partial replacement and cementation of the matrix and clasts by amorphous Si and aluminosilicates with minor goethite and hematite, accompanied by clay illuviation. Silicification of 

Regolith geology of the Yilgan Craton, Western Australia-implications for exploration

Current approaches to biodiversity conservation are largely based on geographic areas, ecosystems, ecological communities and species, with less attention ongenetic diversity and the evolutionary continuum from populations to species. Conservation management generally rests on discrete categories, such as identified species, and, for threated taxa, intraspecific units. Species, in particular, provide a common measure of biodiversity yet in both theory and nature, speciation is typically a protracted process progressing from connected populations to unambiguous species with variable rates of phenotypic, ecological and genetic divergence. Thus, most recognised species are not genetically uniform and are sometimes highly structured into historically isolated populations worthy of consideration as intraspecific units that represent unique genetic diversity for conservation. Genome screens offer unprecedented resolution of structure across taxonomic boundaries in species complexes, and have the potential to oversplit species if not interpreted conservatively. This highlights the blurred line between populations and species, and can confound simple dichotomies of ‘species’ versus ‘not species’. At the same time, like plants, there is increasing evidence than even distantly related animal species can hybridize and exchange genes. A review of conservation legislation reveals that legal definitions of ‘species’ are quite flexible and can accommodate a range of infra-specific taxa and divergent populations, as well as taxonomically recognised species. For example, the legislative definition of a species around the world can include: species, subspecies, varieties, and geographically and/or genetically distinct populations. In principle, this flexibility allows for protection of genetic diversity and maintenance of evolutionary processes at a broad range of infra-specific levels. However, evolutionary biologists often fail to adequately justify and then translate their evidence for genetically defined units into categories suited to assessment under local legislation. We recommend that (i). genomic data should be interpreted conservatively when formally naming species, (ii). concomitantly, there should be stronger impetus and a more uniform approach to identifying clearly justified intraspecific units, (iii). guidelines be developed for recognising and labelling intraspecific data that align with best scientific practice, and (iv). that the more nuanced view of species and speciation emerging from genomic analyses is communicated more effectively by scientists to decision makers.

/pdf/genetic-diversity-and-conservation-units-dealing-with-the-55f91rko4x.pdf

Genetic Diversity and Conservation Units: Dealing With the Species-Population Continuum in the Age of Genomics

SUMMARY: The two central paradigms of marine diversity are that there is a latitudinal cline of increasing species richness from poles to tropics and that species richness increases with depth to a maximum around 2,000 m and thereafter decreases. However, these paradigms were based on data collected in the late 1950’s and early 1960’s. Here I show that the 1960’s data, are not representative and thus the paradigms need re-examination. New data from coastal areas in the northern hemisphere record species richness as high as the highest recorded in the deep-sea. Whilst this suggests that the cline of increasing diversity from shallow to deep-sea does not exist, however, the database for the deep sea is not sufficient to draw such a conclusion. The basic problem with the data from the 1960s is that samples were taken on ecological scales and yet they are used to answer evolutionary questions. The questions that such data were to answer were why do the tropics have higher species richness than polar regions or why do deep-sea sediments have more species than coastal sediments? Evolutionary questions need data from much larger spatial areas. Recently, data representative of large scales have been collected from coastal areas in the northern hemisphere and show that there is a cline of increasing species richness from the Arctic to the tropics, but there does not yet seem to be a similar cline in the southern hemisphere. A number of hypotheses have been proposed for the observed patterns in biodiversity. In terrestrial ecology the energy-productivity hypothesis has gained wide acceptance as an explanation for the latitudinal gradient. Here I examine this and other hypotheses critically. Finally an analysis of research priorities is made. Assessment is urgently needed of the spatial scales and dynamics of species richness from point samples to assemblages, habitats and landscapes, especially in coastal areas and in the tropics, where the threats to biodiversity are greatest. New technologies are available, such as side-scan sonar, acoustics, and under-water digital video cameras but as yet have been relatively little used. Conservation of marine biodiversity must be based on sound theory, yet marine diversity studies lag well behind those of terrestrial habitats.

/pdf/marine-diversity-the-paradigms-in-patterns-of-species-laqvcfg3de.pdf

Marine diversity: the paradigms in patterns of species richness examined*

Plant communities of ancient banded iron formation ranges of South Western Australia occur as islands in a matrix of the largest remaining area of Mediterranean woodlands and shrub lands on the planet. These xeric shrub lands are structurally and compositionally different from the surrounding matrix and exhibit high levels of endemism and species turnover that cannot be ascribed to geology or current climatic gradients. The pattern of the vegetation and flora on these ranges appears to be related to local topographical factors and the long period of time these landscapes have remained unglaciated and above sea level. Similar patterns have recently been described for iron outcrop communities in Brazil. In both regions these communities are being significantly impacted by mining. The high correlation between local endemism and restricted plant communities and high grade mineral deposits presents difficult challenges for achieving a comprehensive, adequate and representative reserve system in South Western Australia.

Plant communities of the ironstone ranges of South Western Australia: hotspots for plant diversity and mineral deposits

Patterns of plant diversity in ironstone ranges in arid south western Australia

The response of grassy vegetation to exclusion from grazing was found to be related to a major productivity gradient in the central highlands of Tasmania. All sites showed a trend toward increased structural complexity, a decrease in bare ground and a decrease in species richness when grazing was excluded. However, the effect was much more pronounced at sites of high productivity. These findings support the theory that species richness is a function of both disturbance and the rate of competitive exclusion (site quality), and support suggestions that stock grazing is inappropriate above 1000 m on the Central Plateau.

Effects of the Cessation of Grazing on the Grasslands and Grassy Woodlands of the Central Plateau, Tasmania

Gibson, N., Coates, D.J. & Thiele, K.R. Taxonomic research and the conservation status of flora in the Yilgarn Banded Iron Formation ranges. Nuytsia 17: 1-12 (2007). The Banded Iron Formation (BIF) ranges are small, ancient ranges scattered across the Yilgarn Craton in southern Western Australia. Increased exploration and mining of iron ore in Western Australia has resulted in a resurgence of botanical survey on and around the BIF ranges, including the discovery of at least 20 unnamed taxa, nine of which were new to science. Recent taxonomic work, published in this special edition of Nuytsia, has concentrated on naming 17 taxa with distributions centred on these ranges and a further 62 taxa of conservation significance in the southern half of Western Australia. Despite this increase in activity, the conservation status of the flora and vegetation remains poorly documented. Patterns in distribution of threatened, rare and poorly known taxa (Declared Rare Flora and Priority Flora) and patterns in endemism are examined on a subset of the 25 ranges most prospective for mining. Preliminary analysis of endemism supports the hypotheses that these ranges represent both refugial habitats of great antiquity and areas of recent speciation. Across Western Australia there are some 2,240 taxa under consideration for formal listing by the Department of Environment and Conservation as threatened; of these, 475 are yet to be formally named. This situation significantly impedes their conservation assessment.

/pdf/taxonomic-research-and-the-conservation-status-of-flora-in-yxx5o67kg1.pdf

Taxonomic research and the conservation status of flora in the Yilgarn Banded Iron Formation ranges

In the Australia–Pacific Region ultramafic outcrops are both widespread and extensive, covering thousands of km2. Soils derived from ultramafic bedrock impose edaphic challenges and are widely known to host highly distinctive floras with high levels of endemism. In the Australia–Pacific Region, the ultramafics of the island of New Caledonia are famed for harbouring 2150 species of vascular plants of which 83% are endemic. Although the ultramafic outcrops in Western Australia are also extensive and harbour 1355 taxa, only 14 species are known to be endemic or have distributions centred on ultramafics. The ultramafic outcrops in New Zealand and Tasmania are small and relatively species-poor. The ultramafic outcrops in Queensland are much larger and host 553 species of which 18 (or possibly 21) species are endemic. Although New Caledonia has a high concentration of Ni hyperaccumulator species (65), only one species from Western Australia and two species from Queensland have so far been found. No Ni hyperaccumulator species are known from Tasmania and New Zealand. Habitat destruction due to forest clearing, uncontrolled fires and nickel mining in New Caledonia impacts on the plant species restricted to ultramafic soils there. In comparison with the nearby floras of New Guinea and South-east Asia, the flora of the Australia–Pacific Region is relatively well studied through the collection of a large number of herbarium specimens. However, there is a need for studies on the evolution of plant lineages on ultramafic soils especially regarding their distinctive morphological characteristics and in relation to hyperaccumulation.

Neil Gibson

Papers

Plant communities of the ironstone ranges of South Western Australia: hotspots for plant diversity and mineral deposits

Patterns of plant diversity in ironstone ranges in arid south western Australia

Effects of the Cessation of Grazing on the Grasslands and Grassy Woodlands of the Central Plateau, Tasmania

Taxonomic research and the conservation status of flora in the Yilgarn Banded Iron Formation ranges

The flora of ultramafic soils in the Australia-Pacific Region: state of knowledge and research priorities