Plant speciation in the Namib Desert : potential origin of a widespread derivative species from a narrow endemic

This research was funded in part by the award of a Natural Environment Research Council (NERC) CASE research studentship to J.J.M.Background:  Parapatric (or ‘budding’) speciation is increasingly recognised as an important phenomenon in plant evolution but its role in extreme (e.g. desert) environments is poorly documented.  Aims:  To test this speciation model in a hypothesised sister pair, the Southwest – North African disjunct Senecio flavus and its putative progenitor, the Namibian Desert endemic S. englerianus.  Methods:  Phylogenetic inferences were combined with niche divergence tests, morphometrics, and experimental-genetic approaches. We also evaluated the potential role of an African Dry Corridor (ADC) in promoting the hypothesised northward expansion of S. flavus (from Namibia), using palaeodistribution models.  Results:  Belonging to an isolated (potential ‘relict’) clade, the two morphologically distinct species showed pronounced niche divergence in Namibia and signs of digenic-epistatic hybrid incompatibility (based on F2 pollen fertility). The presence of ‘connate-fluked’ pappus hairs in S. flavus, likely increasing dispersal ability, is controlled by a single gene locus.  Conclusions:  Our results provide evidence for a possible (and rare) example of ‘budding’ speciation in which a wider-ranged derivative (S. flavus) originated at the periphery of a smaller-ranged progenitor (S. englerianus) in the Namib Desert region. The Southwest – North African disjunction of S. flavus could have been established by dispersal across intermediate ADC areas during periods of (Late) Pleistocene aridification.Publisher PDFPeer reviewe

Hybridisation and detection of a hybrid zone between mesic and desert ragworts (Senecio) across an aridity gradient in the eastern Mediterranean

Background: Hybrid zones provide excellent opportunities for studying plant adaptation and speciation. Aims: We tested whether two herbaceous species of Senecio, S. vernalis and S. glaucus, hybridise in the eastern Mediterranean region and form a hybrid zone across an aridity gradient in the Jordan Rift Valley. Methods: Allozyme variation surveyed across both species was analysed by the programme STRUCTURE to assign individuals to genetic groups and determine levels of admixture. Populations in the Jordan Rift Valley were subsequently subjected to a cline analysis. Results: STRUCTURE showed that interspecific hybrids were produced at low frequency along the Israeli coastal plain where S. glaucus is represented by ssp. glaucus. In contrast, hybrids were more commonly produced in central populations of the Jordan Rift Valley. Here, the two species form a hybrid zone with S. vernalis occurring in mesic sites to the north and S. glaucus (ssp. coronopifolius) in arid sites to the south. Cline analysis showed that the hybrid zone is centred towards the northern end of the Dead Sea, but the analysis failed to distinguish how it is maintained. Conclusions: Future detailed genetic and ecological analysis of the Senecio hybrid zone should improve our understanding of plant adaptation and speciation across aridity gradients

X-Ray diffuse scattering study of boracites

X-ray diffuse scattering from boracite in the cubic phase shows the existence of fluctuation domains, having the form of cigarillos oriented with their main axis parallel to 〈100〉 directions. The relative magnitude of the at. displacements of the metal and halogen atoms in the soft fluctuation corresponds to the conservation of the center of mass, which seems to indicate that the simplest soft optic mode condensation picture of the displacive phase-transition theory may apply to boracites

Calycophyllum candidissimum_Nicaragua_AFLP matrix

This is a presence/absence matrix generated based on AFLP fingerprinting for 220 individuals from thirteen populations spread around the Seasonal Tropical Dry Forest of Nicaragua. As result of three AFLP primer combination, it was successfully scored 226 unambiguous fragments ranging from 87 to 411 base pairs (bp), of which 147 markers were polymorphic

Unbundling Open Access dimensions: a conceptual discussion to reduce terminology inconsistencies

The current ways in which documents are made freely accessible in the Web no longer adhere to the models established Budapest/Bethesda/Berlin (BBB) definitions of Open Access (OA). Since those definitions were established, OA-related terminology has expanded, trying to keep up with all the variants of OA publishing that are out there. However, the inconsistent and arbitrary terminology that is being used to refer to these variants are complicating communication about OA-related issues. This study intends to initiate a discussion on this issue, by proposing a conceptual model of OA. Our model features six different dimensions (authoritativeness, user rights, stability, immediacy, peer-review, and cost). Each dimension allows for a range of different options. We believe that by combining the options in these six dimensions, we can arrive at all the current variants of OA, while avoiding ambiguous and/or arbitrary terminology. This model can be an useful tool for funders and policy makers who need to decide exactly which aspects of OA are necessary for each specific scenario

Recurrent origin of peripheral, coastal (sub)species in Mediterranean <i>Senecio</i> (Asteraceae)

<p><b><i>Background</i></b>: It is argued that coastal endemic taxa may evolve in parallel at the periphery of the distributional range of a widespread species.</p> <p><b><i>Aims</i></b>: We tested this hypothesis for the origins of three peripheral, coastal isolates of <i>Senecio, S. glaucus</i> ssp. <i>glaucus</i> (Israel), <i>S. g</i>. ssp. <i>coronopifolius</i> p.p. (Sicily), and <i>S. hesperidium</i> (Morocco), from widespread <i>S. glaucus</i> ssp. <i>coronopifolius</i>. We also determined the relative roles of selection vs. genetic drift in shaping phenotypic divergence in ssp. <i>glaucus</i> and <i>S. hesperidium</i>, using Lande’s test of neutral morphological change.</p> <p><b><i>Methods</i></b>: We surveyed morphological and/or allozyme variation in the three peripheral isolates and mainly inland populations of <i>S. g</i>. ssp. <i>coronopifolius.</i></p> <p><b><i>Results</i></b>: Genetic data supported independent origins of the coastal taxa from nearby populations of ssp. <i>coronopifolius</i>. These descendant and ancestral populations showed pronounced morphological but weak genetic differentiation. Phenotypic similarities between ssp. <i>glaucus</i> (Israel) and <i>S. hesperidium</i> (Morocco) in plant height and floral traits may have resulted from parallel divergent selection from ssp. <i>coronopifolius</i>, though drift remains an alternative cause in <i>S. hesperidium</i>.</p> <p><b><i>Conclusions</i></b>: Our results indicate parallel ecotype formation and (sub)speciation in <i>Senecio</i> in which primarily selective vs. neutral determinants promoted the recurrent origin of coastal types in, respectively, Israel and Morocco.</p

Plant speciation in the Namib Desert: potential origin of a widespread derivative species from a narrow endemic

Parapatric (or ‘budding’) speciation is increasingly recognised as an important phenomenon in plant evolution but its role in extreme (e.g. desert) environments is poorly documented. To test this speciation model in a hypothesised sister pair, the Southwest – North African disjunct Senecio flavus and its putative progenitor, the Namibian Desert endemic S. englerianus. Phylogenetic inferences were combined with niche divergence tests, morphometrics, and experimental-genetic approaches. We also evaluated the potential role of an African Dry Corridor (ADC) in promoting the hypothesised northward expansion of S. flavus (from Namibia), using palaeodistribution models. Belonging to an isolated (potential ‘relict’) clade, the two morphologically distinct species showed pronounced niche divergence in Namibia and signs of digenic-epistatic hybrid incompatibility (based on F2 pollen fertility). The presence of ‘connate-fluked’ pappus hairs in S. flavus, likely increasing dispersal ability, is controlled by a single gene locus. Our results provide evidence for a possible (and rare) example of ‘budding’ speciation in which a wider-ranged derivative (S. flavus) originated at the periphery of a smaller-ranged progenitor (S. englerianus) in the Namib Desert region. The Southwest – North African disjunction of S. flavus could have been established by dispersal across intermediate ADC areas during periods of (Late) Pleistocene aridification.</p

Hybridisation and detection of a hybrid zone between mesic and desert ragworts (<i>Senecio</i>) across an aridity gradient in the eastern Mediterranean

<p><b>Background</b>: Hybrid zones provide excellent opportunities for studying plant adaptation and speciation.</p> <p><b>Aims</b>: We tested whether two herbaceous species of <i>Senecio, S. vernalis</i> and <i>S. glaucus</i>, hybridise in the eastern Mediterranean region and form a hybrid zone across an aridity gradient in the Jordan Rift Valley.</p> <p><b>Methods</b>: Allozyme variation surveyed across both species was analysed by the programme STRUCTURE to assign individuals to genetic groups and determine levels of admixture. Populations in the Jordan Rift Valley were subsequently subjected to a cline analysis.</p> <p><b>Results</b>: STRUCTURE showed that interspecific hybrids were produced at low frequency along the Israeli coastal plain where <i>S. glaucus</i> is represented by ssp. <i>glaucus</i>. In contrast, hybrids were more commonly produced in central populations of the Jordan Rift Valley. Here, the two species form a hybrid zone with <i>S. vernalis</i> occurring in mesic sites to the north and <i>S. glaucus</i> (ssp. <i>coronopifolius</i>) in arid sites to the south. Cline analysis showed that the hybrid zone is centred towards the northern end of the Dead Sea, but the analysis failed to distinguish how it is maintained.</p> <p><b>Conclusions</b>: Future detailed genetic and ecological analysis of the <i>Senecio</i> hybrid zone should improve our understanding of plant adaptation and speciation across aridity gradients.</p

Genomic insights into historical population dynamics, local adaptation, and climate change vulnerability of the East Asian Tertiary relict Euptelea (Eupteleaceae).

The warm-temperate and subtropical climate zones of East Asia are a hotspot of plant species richness and endemism, including a noticeable number of species-poor Tertiary relict tree genera. However, little is understood about when East Asian Tertiary relict plants diversified, how they responded demographically to past environmental change, and to what extent their current genomic composition (and adaptive capacity) might mitigate the effects of global warming. Here, we obtained genomic (RAD-SNP) data for 171 samples from two extant species of Euptelea in China (24 E. pleiosperma populations) and Japan (11 E. polyandra populations) to elucidate their divergence and demographic histories, genome-wide associations with current environmental variables, and genomic vulnerability to future climate change. Our results indicate that Late Miocene changes in climate and/or sea level promoted species divergence, whereas Late Pliocene uplifting in southwest China likely fostered lineage divergence within E. pleiosperma. Its subsequent range expansion into central/east (CE) China bears genomic signatures of climate-driven selection, yet extant CE populations are predicted to be most vulnerable to future climate change. For E. polyandra, geography was the only significant predictor of genomic variation. Our findings indicate a profound impact of Late Neogene geological and climate change on the evolutionary history of Euptelea, with much stronger signals of local adaptation left in China than in Japan. This study deepens our understanding of the complex evolutionary forces that influence the distribution of genetic variation of Tertiary relict trees, and provides insights into their susceptibility to global change and potential for adaptive responses. Our results lay the groundwork for future conservation and restoration programs for Euptelea