AIM: Dioscorea (Dioscoreaceae) is a predominantly pantropical genus (< 600 species) that includes the third most important tropical tuber crop and species of pharmacological value. Fossil records ...from both the Northern and Southern Hemispheres were used to test hypotheses about the origin of the genus Dioscorea, and to examine potential macroevolutionary processes that led to its current distribution. LOCATION: Pantropical distribution. METHODS: Divergence times were estimated using the most comprehensive phylogeny of the group published to date based on plastid sequences and fossil calibrations, applying a relaxed‐clock model approach. Ancestral areas and range shifts were reconstructed using time‐stratified likelihood‐based models, reflecting past continental connectivity and biogeographical models incorporating the spatial range of fossils. RESULTS: Fossil‐informed biogeographical analysis supported colonization of the Nearctic by ancient yam lineages from the western Palaearctic and subsequent migration to the South. Most of the pantropical South American, African and Southeast Asian lineages experienced a relatively recent diversification in the Oligocene–Miocene. Long‐distance dispersals were inferred for the colonizations of the New World, Africa and Madagascar. MAIN CONCLUSIONS: Dioscorea likely originated between the Late Cretaceous and the Early Eocene in the Laurasian Palaearctic, followed by possible dispersal to South America via the Eocene North Atlantic Land Bridge.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Riella (Riellaceae) is a genus of rare, ephemeral, aquatic liverworts that includes some taxa specialized in growing submerged in brackish, seasonal water ponds and lagoons. One of these species, ...Riella helicophylla is the type of the genus. Apart from being of conservation concern, it has been used as a model organism for cytological and physiological processes. The species was described from Algeria in the mid‐nineteenth century and was not found elsewhere for almost a century, when it was discovered in central Spain. Nonetheless, those new populations were considered morphologically different and served to describe a new variety (var. macrocarpa), and a form (f. latealata) of the latter. The number of population records increased considerably in the following decades, especially in the late twentieth century; at the same time, it was discovered in several countries throughout the Mediterranean basin. Those reports, however, did not account for its infraspecific distinction. As part of a broader study of the genus, in this work, we have revisited the taxonomy of R. helicophylla based on an integrative approach considering morphological and molecular DNA sequence data. Our broadly sampled study revealed that R. helicophylla includes two morphotypes corresponding with the previously recognized varieties of this species. These varieties differ consistently in a number of morphological gametophytic and spore traits. Riella helicophylla was resolved as paraphyletic in phylogenies based on nuclear and plastid DNA sequences. The accessions clustered in two monophyletic clades in concert with morphology, supporting their recognition at the species level. Accordingly, a new combination is proposed, R. macrocarpa, which includes the neglected R. helicophylla var. macrocarpa and R. helicophylla var. macrocarpa f. latealata. Lectotypes are designated for the two latter taxa and for R. helicophylla. The two species are fully described and illustrated, and an updated identification key of the Mediterranean species is included. Updated information on the conservation status of both species is provided.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Understanding the processes of biological diversification is a central topic in evolutionary biology. The South African Cape fynbos, one of the major plant biodiversity hotspots out of the tropics, ...has prompted several hypotheses about the causes of generation and maintenance of biodiversity. Fire has been traditionally invoked as a key element to explain high levels of biodiversity in highly speciose fynbos taxa, such as the genus Erica. In this study, we have implemented a microevolutionary approach to elucidate how plant-response to fire may contribute to explain high levels of diversification in Erica. By using microsatellite markers, we investigated the genetic background of seeder (fire-sensitive) and resprouter (fire-resistant) populations of the fynbos species Erica coccinea. We found higher within-population genetic diversity and higher among-population differentiation in seeder populations and interpreted these higher levels of genetic diversification as a consequence of the comparatively shorter generation times and faster population turnover in the seeder form of this species. Considering that genetic divergence among populations may be seen as the initial step to speciation, the parallelism between these results and the pattern of biodiversity at the genus level offers stimulating insights into understanding causes of speciation of the genus Erica in the Cape fynbos.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The effects of Pleistocene glaciations and geographical barriers on the phylogeographic patterns of lowland plant species in Mediterranean-climate areas of Central Chile are poorly understood. We ...used Dioscorea humilis (Dioscoreaceae), a dioecious geophyte extending 530 km from the Valparaíso to the Bío-Bío Regions, as a case study to disentangle the spatio-temporal evolution of populations in conjunction with latitudinal environmental changes since the Last Inter-Glacial (LIG) to the present. We used nuclear microsatellite loci, chloroplast (cpDNA) sequences and environmental niche modelling (ENM) to construct current and past scenarios from bioclimatic and geographical variables and to infer the evolutionary history of the taxa. We found strong genetic differentiation at nuclear microsatellite loci between the two subspecies of D. humilis, probably predating the LIG. Bayesian analyses of population structure revealed strong genetic differentiation of the widespread D. humilis subsp. humilis into northern and southern population groups, separated by the Maipo river. ENM revealed that the ecological niche differentiation of both groups have been maintained up to present times although their respective geographical distributions apparently fluctuated in concert with the climatic oscillations of the Last Glacial Maximum (LGM) and the Holocene. Genetic data revealed signatures of eastern and western postglacial expansion of the northern populations from the central Chilean depression, whereas the southern ones experienced a rapid southward expansion after the LGM. This study describes the complex evolutionary histories of lowland Mediterranean Chilean plants mediated by the summed effects of spatial isolation caused by riverine geographical barriers and the climatic changes of the Quaternary.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Many habitat specialist species are originally composed of small, discontinuous populations because their habitats are naturally fragmented or patchy. They may have suffered the long-term effects of ...natural patchiness. Mediterranean heathlands, a representative habitat in the Strait of Gibraltar region, are associated with nutrient-poor, acidic sandstone soils. Sandstone soil patches in the African side of the Strait (Tangier) are, in general, smaller and more scattered than in the European side (Algeciras). In this study, we analyze the effect of this sandstone patchiness on the population genetic diversity and structure of two Erica species from these Mediterranean heathlands that differ in their edaphic specificity, E. australis, sandstone specialist, and E. arborea, generalist. Average levels of within-population genetic diversity and gene flow between populations were significantly lower in Tangier (high sandstone patchiness) than in Algeciras (low patchiness) for the sandstone specialist, whereas no differences between both sides of the Strait were detected in the edaphic generalist. Since most endemic species in Mediterranean heathlands of the Strait of Gibraltar are sandstone specialists, these results highlight an increased vulnerability to loss of genetic diversity and local extinction of the heathland endemic flora in the Tangier side of the Strait of Gibraltar.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Divergence times and biogeographical analyses have been conducted within the Loliinae, one of the largest subtribes of temperate grasses. New sequence data from representatives of the almost ...unexplored New World, New Zealand, and Eastern Asian centres were added to those of the panMediterranean region and used to reconstruct the phylogeny of the group and to calculate the times of lineage-splitting using Bayesian approaches. The traditional separation between broad-leaved and fine-leaved
Festuca species was still maintained, though several new broad-leaved lineages fell within the fine-leaved clade or were placed in an unsupported intermediate position. A strong biogeographical signal was detected for several Asian–American, American, Neozeylandic, and Macaronesian clades with different affinities to both the broad and the fine-leaved
Festuca. Bayesian estimates of divergence and dispersal–vicariance analyses indicate that the broad-leaved and fine-leaved Loliinae likely originated in the Miocene (13
My) in the panMediterranean–SW Asian region and then expanded towards C and E Asia from where they colonized the New World. Further expansions in America (10–3.8
My) showed a predominant migratory route from North to South (N America
↔
the Andes
↔
Patagonia). This late Tertiary scenario of successive colonizations and secondary polyploid radiations in the southern hemisphere from the northern hemisphere was accompanied by occasional transcontinental long-distance dispersal events between South America and New Zealand. Multiple Pliocene dispersal events (3.6–2.5
My) from the near SW European and NW African continents gave rise to the Macaronesian Loliinae flora, while a more recent Pleistocene origin (2–1
My) is hypothesized for the high polyploid lineages that successfully colonized newly deglaciated areas in both hemispheres.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Aim The Chilean endemic Dioscorea biloba (Dioscoreaceae) is a dioecious geophyte that shows a remarkable 600 km north–south disjunction in the peripheral arid area of the Atacama Desert. Its ...restricted present‐day distribution and probable Neogene origin indicate that its populations have a history linked to that of the Atacama Desert, making this an ideal model species with which to investigate the biogeography of the region. Location Chile, Atacama Desert and peripheral arid area. Methods Two hundred and seventy‐five individuals from nine populations were genotyped for seven nuclear microsatellite loci, and plastid trnL–F and trnT–L sequences were obtained for a representative subset of these. Analyses included the estimation of genetic diversity and population structure through clustering, Bayesian and analysis of molecular variance analyses, and statistical parsimony networks of chloroplast haplotypes. Isolation by distance was tested against alternative dispersal hypotheses. Results Microsatellite markers revealed moderate to high levels of genetic diversity within populations, with those from the southern Limarí Valley showing the highest values and northern populations showing less exclusive alleles. Bayesian analysis of microsatellite data identified three genetic groups that corresponded to geographical ranges. Chloroplast phylogeography revealed no haplotypes shared between northern and southern ranges, and little haplotype sharing between the two neighbouring southern valleys. Dispersal models suggested the presence of extinct hypothetical populations between the southern and northern ranges. Main conclusions Our results are consistent with prolonged isolation of the northern and southern groups, mediated by the life‐history traits of the species. Significant isolation was revealed at both large and moderate distances as gene flow was not evident even between neighbouring valleys. Bayesian analyses of microsatellite and chloroplast haplotype diversity identified the southern area of Limarí as the probable area of origin of the species. Our data do not support recent dispersal of D. biloba from the southern range into Antofagasta, but indicate the fragmentation of an earlier wider range, concomitant with the Pliocene–Pleistocene climatic oscillations, with subsequent extinctions of the Atacama Desert populations and the divergence of the peripheral ones as a consequence of genetic drift.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Calluna vulgaris (Ericaceae) is the most widespread and prevalent woody species of the European dry heathland, from the African side of the Strait of Gibraltar to northern Europe. However, ...previous biogeographic analyses of this species have ignored the western Mediterranean region, despite its preponderant role as a major glacial refugium for European biota. Here, we explore the existence of further Pleistocene glacial refugia for C. vulgaris in the Iberian Peninsula and the Strait of Gibraltar area and provide new insights into the post-glacial colonization of Europe by this emblematic heathland species. We carried out phylogeographical analyses of C. vulgaris samples from 44 locations using four plastid markers (matK, trnH-psbA, trnL-F and rpl16). We built palaeodistribution models using MAXENT to identify possible refugia for C. vulgaris during the mid-Pliocene, Last Interglacial (LIG), Last Glacial Maximum (LGM) and mid-Holocene. Our results identified a genetic lineage exclusive to the Strait of Gibraltar area s.l. (south-western Iberian Peninsula and north-western tip of Africa) as the most probable close to the clade of origin of the species. This lineage also had more private haplotypes than more recent, Eurosiberian clades. The obtained data highlighted two main refugia for C. vulgaris during the LGM, one around the Strait of Gibraltar and another in the north-western Iberian Peninsula. The Strait of Gibraltar area is a major centre of origin or glacial refugium for the heather C. vulgaris. However, the north-western Iberian Peninsula seems to have acted as a secondary glacial refugium for the more recent, Eurosiberian lineage of this species. This study stresses the importance of the Strait of Gibraltar area in the biogeographic history and conservation of the heather and, by extension, the European heathland habitat.
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