Source Of Speciation Research Articles

Interhemispheric biodiversity peaks of living brachiopods coinciding with warm-temperate zones and correlated to a multitude of biotic, abiotic and evolutionary factors

Applying Locally Weighted Scatter-plot Smoother (LOESS) regression, we analysed the global latitudinal diversity patterns of 394 living brachiopod species. We found a consistent bimodal pattern dominated by two mid-latitude peaks located respectively at 35–40°S and 30–35°N (~warm-temperate zones, WTZs). The bimodality was found to be largely persistent and consistent irrespective of taxonomic, bathymetric and spatial scales. We tested the strength of seven ecological hypotheses thought to potentially explain the classic unimodal latitudinal diversity gradient. The Rapoport's rule was found to be the strongest model fitting the bimodal pattern, followed by the Species-Energy hypothesis. The mechanisms through which the mean latitudinal ranges and thermal niches of living brachiopods may have combined to produce the bimodality are further linked to two other factors: 1) most living brachiopods seem to have a strong adaptation to the mesothermal conditions of the WTZs, and 2) for living brachiopods, the WTZs appear to represent both a source of speciation indicated by a relatively higher per-genus diversification rate and a ‘sink’ of biodiversity due to biogeographic mixing and a concentration of species range-end points.

Begomoviruses: what is the secret(s) of their success?

Begomoviruses constitute an extremely successful group of emerging plant viruses transmitted by whiteflies of the Bemisia tabaci complex. Hosts include important vegetable, root, and fiber crops grown in the tropics and subtropics. Factors contributing to the ever-increasing diversity and success of begomoviruses include their predisposition to recombine their genomes, interaction with DNA satellites recruited throughout their evolution, presence of wild plants as a virus reservoir and a source of speciation, and extreme polyphagia and continuous movement of the insect vectors to temperate regions. These features as well as some controversial issues (replication in the insect vector, putative seed transmission, transmission by insects other than B. tabaci, and expansion of the host range to monocotyledonous plants) will be analyzed in this review.

Recurrent speciation of a tomato yellow leaf curl geminivirus in Portugal by recombination

Recurrent evolution can involve interspecific interactions, recognized to play a primary role in the diversification and organization of life. Both in the plant and animal kingdoms, the recurrent formation of allopolyploid species has been described. In the virosphere, recombination between isolates of different species has been shown to be a source of speciation. In this work, complete genome analysis showed that speciation through recombination of an emergent DNA plant virus, tomato yellow leaf curl Malaga virus (genus Begomovirus, family Geminiviridae), has occurred independently in Portugal and Spain, confirming previous observations with tomato yellow leaf curl Axarquia virus, also originated independently in Spain and Italy. These results will guide future research to discover new cases of recurrent emergence of recombinant virus species in geographical areas where the putative parents co-exist or can be introduced. This will reveal the role that recurrent speciation through recombination plays in the evolution of the virosphere and will help to understand the consequences of this phenomenon on the diversification of life.

Historical biogeography and speciation in the Creole wrasses (Labridae, Clepticus).

We tested whether vicariance or dispersal was the likely source of speciation in the genus Clepticus by evaluating the evolutionary timing of the effect of the mid-Atlantic barrier, which separates C. brasiliensis and C. africanus, and the Amazon barrier, which separates C. parrae and C brasiliensis. Genetic data from three mitochondrial genes and one nuclear gene were used. Mitochondrial genes separated Clepticus into three well supported clades corresponding to the three recognized allopatric morpho-species. All analyses provided consistent support for an initial separation (~9.68 to 1.86 mya; 4.84% sequence divergence) of the Caribbean and South Atlantic lineages, followed by a much more recent divergence (~ 0.60 to 0.12 mya; 0.3% sequence divergence) of the Brazilian and African sister morpho-species. Both these phylogenetic events occurred well after the formation of the two barriers that currently separate those three allopatric populations. The planktonic larval duration of these species (35–49 days) and coastal pelagic habits may have facilitated dispersal by this genus across those dispersal barriers after they formed.

The use of flotation techniques in the remediation of heavy metal contaminated sediments and soils: an overview of controlling factors

The potential use of flotation as a remediation technique for heavy metal contaminated sediments and soils is discussed. In general, the flotation process is much less selective for heavy metals in sediments and soils compared to the results obtained in common mineral ore flotation practice. The following factors could be isolated as responsible for this different behaviour: the metal distribution over the different geochemical phases (metal partitioning), the metal distribution over the different size fractions (metal fractionation) and the presence of organic matter (humic substances). These controlling factors were illustrated by performing Denver flotation experiments on a natural canal sediment and column flotation tests on synthetic sediments. It is emphasised that sequential extraction techniques can be used as a tool for determining the original metal partitioning in sediments and soils and as a result helps to select the most appropriate procedure of flotation (e.g. a phase-specific collector). A chemical pre-treatment step (e.g. sulphidisation, hydroxylation) prior to the flotation of sediments and soils can be beneficial depending on the in-situ metal partitioning and serves to transfer heavy metals, which are associated with different speciation sources (oxides, sulphides , clay minerals, organic matter, etc.), into one unique-good floatable-chemical speciation form (e.g. oxides, sulphides). The selective flotation of metal-bearing particles from fine-textured sediments and soils is very difficult and therefore a major challenge for future research is to tackle the problems related with the flotation of these fines. Organic matter, which is rather selectively flotated, has an adverse effect on the metal (sulphide) flotation selectivity due to its adsorption onto mineral surfaces.

Subspeciation in the Western Whipbird Psophodes nigrogularis and its Zoogeographical Significance, with Descriptions of Two New Subspecies

Geographical variation in the Western Whipbird Psophodes nigrogularis is reviewed by routine morphometric procedures. Four subspecies are recognised: nominotypical nigrogularis in extreme coastal south-western Australia, oberon in the mallee heaths of eastern south-west Australia, lashmari on Kangaroo Island and leucogaster in the Murray Mallee and on Yorke and Eyre Peninsulas, South Australia. Two of the subspecies (oberon and lashmari) are described as new. The presence of two fonns (nigrogularis and oberon) in south-west Australia raises questions about their taxonomic status and parallels the occurrence of other pairs of Bassian taxa in that region. Reconstruction of the evolution of such pairs identifies the highlands about the South Australian gulfs as an important refuge and source of speciation for Bassian birds during Quaternary and perhaps later Tertiary times. Implications for conservation are reassessed.