Geographic Disjunction Research Articles

A dated molecular perspective of eucalypt taxonomy, evolution and diversification

The eucalypts, which include Eucalyptus, Angophora and Corymbia, are native to Australia and Malesia and include over 800 named species in a mixture of diverse and depauperate lineages. We assessed the fit of the eucalypt taxonomic classification to a phylogeny of 711 species scored for DNA sequences of plastid matK and psbA–trnH, as well as nuclear internal transcribed spacer and external transcribed spacer. Two broadly similar topologies emerge from both maximum likelihood and Bayesian analyses, showing Angophora nested within Corymbia, or Angophora sister to Corymbia. The position of certain species-poor groups on long branches fluctuated relative to the three major Eucalyptus subgenera, and positions of several closely related species within those subgenera were unstable and lacked statistical support. Most sections and series of Eucalyptus were not recovered as monophyletic. We calibrated these phylogenies against time, using penalised likelihood and constraints obtained from fossil ages. On the basis of these trees, most major eucalypt subgenera arose in the Late Eocene and Early Oligocene. All Eucalyptus clades with taxa occurring in south-eastern Australia have crown ages <20 million years. Several eucalypt clades display a strong present-day geographic disjunction, although these clades did not have strong phylogenetic statistical support. In particular, the estimated age of the separation between the eudesmids (Eucalyptus subgenus Eudesmia) and monocalypts (Eucalyptus subgenus Eucalyptus) was consistent with extensive inland water bodies in the Eocene. Bayesian analysis of macroevolutionary mixture rates of net species diversification accelerated in five sections of Eucalyptus subgenus Symphyomyrtus, all beginning 2–3 million years ago and associated with semi-arid habitats dominated by mallee and mallet growth forms, and with open woodlands and forests in eastern Australia. This is the first time that a calibrated molecular study has shown support for the rapid diversification of eucalypts in the recent past, most likely driven by changing climate and diverse soil geochemical conditions.

Reinvestigating an enigmatic Late Cretaceous monocot: morphology, taxonomy, and biogeography of Viracarpon.

Angiosperm-dominated floras of the Late Cretaceous are essential for understanding the evolutionary, ecological, and geographic radiation of flowering plants. The Late Cretaceous–early Paleogene Deccan Intertrappean Beds of India contain angiosperm-dominated plant fossil assemblages known from multiple localities in central India. Numerous monocots have been documented from these assemblages, providing a window into an important but poorly understood time in their diversification. One component of the Deccan monocot diversity is the genus Viracarpon, known from anatomically preserved infructescences. Viracarpon was first collected over a century ago and has been the subject of numerous studies. However, resolution of its three-dimensional (3D) morphology and anatomy, as well as its taxonomic affinities, has remained elusive. In this study we investigated the morphology and taxonomy of genus Viracarpon, combining traditional paleobotanical techniques and X-ray micro-computed tomography (μCT). Re-examination of type and figured specimens, 3D reconstructions of fruits, and characterization of structures in multiple planes of section using μCT data allowed us to resolve conflicting interpretations of fruit morphology and identify additional characters useful in refining potential taxonomic affinities. Among the four Viracarpon species previously recognized, we consider two to be valid (Viracarpon hexaspermum and Viracarpon elongatum), and the other two to be synonyms of these. Furthermore, we found that permineralized infructescences of Coahuilocarpon phytolaccoides from the late Campanian of Mexico correspond closely in morphology to V. hexaspermum. We argue that Viracarpon and Coahuilocarpon are congeneric and provide the new combination, Viracarpon phytolaccoides (Cevallos-Ferriz, Estrada-Ruiz & Perez-Hernandez) Matsunaga, S.Y. Smith, & Manchester comb. nov. The significant geographic disjunction between these two occurrences indicates that the genus Viracarpon was widespread and may be present in other Late Cretaceous assemblages. Viracarpon exhibits character combinations not present in any extant taxa and its affinities remain unresolved, possibly representing an extinct member of Alismatales. The character mosaic observed in Viracarpon and the broad distribution of the genus provide new data relevant to understanding early monocot evolution and suggest that the (thus far) largely invisible Late Cretaceous monocot diversification was characterized by enigmatic and/or stem taxa.

Range extensions for the rare moss Plagiothecium handelii, and its transfer to the resurrected genus Ortholimnobium

Plagiothecium handelii is newly recorded for Europe (Austria and Romania) and eastern North America (Tennessee, USA). This dainty species was previously known only from Yunnan and Sichuan Provinces, China. Morphologically, the disjunctive populations belong to a single species. A 27-taxon phylogeny of Plagiothecium based on nuclear ITS and plastid rpl16 intron DNA sequence data resolved Austrian and Chinese populations of P. handelii as sisters, in a clade with P. paleaceum, a julaceous Himalayan species with cochleariform leaves. In contrast, P. handelii is a filiform plant with distant, ovate-acuminate leaves. In sequence identity the three terminals have a similar level of variation, suggesting that the geographic disjunction between the two populations of P. handelii is quite old. Morphologically and genetically the clade is a well defined lineage (Ortholimnobium) that is transitional between Plagiothecium s.str. and Struckia. The new combinations O. paleaceum and O. handelii are made. In Europe, O. handelii should be classified as vulnerable.

Tetrapod distribution and temperature rise during the Permian-Triassic mass extinction.

The Permian–Triassic mass extinction (PTME) had an enormous impact on life in three ways: by substantially reducing diversity, by reshuffling the composition of ecosystems and by expelling life from the tropics following episodes of intense global warming. But was there really an ‘equatorial tetrapod gap', and how long did it last? Here, we consider both skeletal and footprint data, and find a more complex pattern: (i) tetrapods were distributed both at high and low latitudes during this time; (ii) there was a clear geographic disjunction through the PTME, with tetrapod distribution shifting 10–15° poleward; and (iii) there was a rapid expansion phase across the whole of Pangea following the PTME. These changes are consistent with a model of generalized migration of tetrapods to higher latitudinal, cooler regions, to escape from the superhot equatorial climate in the earliest Triassic, but the effect was shorter in time scale, and not as pronounced as had been proposed. In the recovery phase following the PTME, this episode of forced range expansion also appears to have promoted the emergence and radiation of entirely new groups, such as the archosaurs, including the dinosaurs.

Eubria mesoamericana Barr and Shepard (Coleoptera: Psephenidae: Eubriinae), a New Psephenid Species from Central America with an Enigmatic Generic Distribution

Abstract Eubria mesoamericana Barr and Shepard, new species, is described from Panama and Costa Rica, accompanied by images of the adult and larva and illustrations of the male genitalia. Habitat information is provided for the specimens collected by the authors. The discovery of a new species of Eubria Latreille in the Neotropics reveals a surprising geographic disjunction from its only congener in the Palearctic, Eubria palustris (Germar). Placement of the new species in the genus Eubria is supported by adult and larval morphological characters.

Biogeography of the Gondwanan tree fern family Dicksoniaceae—A tale of vicariance, dispersal and extinction

AbstractAimAre the disjunct distributions of ancient lineages on continents in the Southern Hemisphere determined by vicariance following the Gondwanan tectonic breakup or recent long‐distance dispersal? We traced the historical biogeography of the tree fern family Dicksoniaceae (145 Ma), which has a typical Gondwanan distribution, to test for vicariance or recent long‐distance dispersal.LocationSubtropical, tropical and temperate forests of the Southern Hemisphere.MethodsWe performed a molecular phylogenetic study of the family based on four chloroplast markers using Bayesian and maximum likelihood inference. Spore fossils served to calibrate the dating of the phylogeny using beast. The historical biogeography of the family was traced via an ancestral area reconstruction using a maximum likelihood approach.ResultsWe corroborated the genus Dicksonia (widespread) as sister to Lophosoria (Neotropical), with Calochlaena (Palaeotropical) as sister to both. The phylogenetic splits between the genera predate the break‐up of Gondwana. Lophosoria is currently restricted to America but fossils document extinct populations in Australia, Tasmania and Antarctica. Within Dicksonia, we found three clades which separated 55–25 Ma: one including species from New Caledonia, New Zealand and Fiji; another containing species from the Neotropics as well as southern Australia and New Zealand; and one with species from northern Australia to the Philippines and Sumatra. Vicariance and ancient long‐distance dispersal can equally explain the occurrence of these three clades on different tectonic units of Gondwana. Other geographical disjunctions, for example, between Australia and Malesia, are more recent (15–3 Ma) and inferred to be the result of long‐distance dispersal. The combination of fossil evidence and island endemics whose ages predate the ages of the islands point to substantial extinction in the genus.Main conclusionsThe biogeographical history of the family Dicksoniaceae, and especially of Dicksonia itself, appears to have involved a much more dynamic interplay of vicariance, dispersal and extinction than inferred from current distributions alone. Dicksonia is one of the few biogeographical Gondwanan floristic elements whose current distribution can at least partly be linked to plate tectonic events.

First record for the flora of Italy and lectotypification of the name Linum elegans (Linaceae)

Linum elegans has been detected in calcareous rocky garrigues on the Gargano promontory (Apulia, SE-Italy), representing the first record for the Italian flora and the first one outside the Balkan Peninsula. The geographical disjunction may provide evidence for past amphi-Adriatic/amphi-Ionic terrestrial connections. The population found was ascribed to L. campanulatum in the past. As a consequence, a comparison between these two species is undertaken. Furthermore, the name L. elegans is here lectotypified on a specimen preserved at G, and the IUCN assessment of the species in Italy is briefly discussed.

A molecular phylogeny reveals the Cuban enigmatic genus Behaimia as a new piece in the Brongniartieae puzzle of papilionoid legumes

The papilionoid legume tribe Brongniartieae comprises a collection of 15 genera with disparate morphologies that were previously positioned in at least four remotely related tribes. The Brongniartieae displays a wide geographical disjunction between Australia and the New World and previous phylogenetic studies had provided conflicting results about the relationships between the American and Australian genera. We carry out phylogenetic analyses of (1) a plastid matK dataset extensively sampled across legumes to solve the enigmatic relationship of the Cuban-endemic monospecific genus Behaimia; and (2) multilocus datasets with focus on all genera ever referred to Brongniartieae. These analyses resulted in a well-resolved and strongly-supported phylogenetic tree of the Brongniartieae. The monophyly of all American genera of Brongniartieae is strongly supported. The doubtful position of the Australian genus Plagiocarpus is resolved within a clade comprising all Australian genera. Behaimia has been traditionally classified in tribe Millettieae, but our new molecular data and re-assessment of morphological traits have resolved the genus within the early-branching papilionoid tribe Brongniartieae. Characters including the pinnately multifoliolate (vs. unifoliolate) leaves, a sessile (vs. stipitate) ovary, and an indehiscent or late dehiscent one-seeded pod distinguish Behaimia from its closer relatives, the South American genera Cyclolobium and Limadendron.

Footprint of the eastern euroasian past in Italian populations of Cryptotaenia thomasii (Ten.) DC

BackgroundThe knowledge of the genetic architecture of closely related species and/or populations of a single species can be very useful to shed light on the processes that led to their current distributions. The present study provides a preliminary evaluation of the conservation status of the populations of Cryptotaenia thomasii, a very narrow endemic species occurring in southern Italy. Previous studies showed that C. thomasii was phylogenetically closely related to C. flahaultii, endemic species of Caucasus, and to evaluate its conservation status and the genetic variability of plant species the internal transcribed spacers (ITSs) of nuclear ribosomal DNA were sequenced and the SNPs were analyzed.ResultsThe restriction analysis of nrDNA with the restriction enzymes allowed to detect the presence of two single mutations (SNPs) among the sequences of two species. Our molecular analysis pointed out that C. thomasii and C. flahaultii, in spite of their geographical disjunction, show a sign of an ancient contact as an extreme case of geographical disjunction Italian-Caucasus.ConclusionFrom the evolutionary history of the species and its distribution pattern one can reconstruct a possible scenario with some hypotheses that explain the hypothetical ancestral area where the two species were in contact. We speculate the two species may have originated from fragmentation of a common ancestor widespread in the Western Palearctic zone and have survived in two separated refuge areas limited by important mountain systems. This hypothesis is supported by our molecular analysis, in fact, the analysis of SNPs showed that some C. thomasii populations retain the signs of an ancient link with C. flahaultii.

Evolutionary history ofGymnocarpos(Caryophyllaceae) in the arid regions from North Africa to Central Asia

Gymnocarpos has only about ten species distributed in the arid regions of Asia and Africa, but it exhibits a geographical disjunction between eastern Central Asia and western North Africa and Minor ...

Phylogenetic placement of the enigmatic fern genus Trichoneuron informs on the infra-familial relationship of Dryopteridaceae

The taxonomic status and phylogenetic placement of the monotypic genus Trichoneuron is studied using DNA sequences of three plastid-coding genes. Trichoneuron was originally assigned to Thelypteridaceae but has been considered to be a synonym of Lastreopsis in recent treatments. In this study, the proposed relationship of Trichoneuron to Lastreopsis was tested using a comprehensive taxa sampling of Dryopteridaceae. Our results strongly support the recognition of Trichoneuron as a distinct genus belonging to Dryopteridaceae. Trichoneuron does not group together with Lastreopsis. Instead the genus was found to be sister to the Neotropical genus Polystichopsis. This sister relationship is supported by the occurrence of long pluricellular hairs attached to the rachis of both genera. The morphological distinction of Trichoneuron from Lastreopsis is backed by the structure of the adaxial groove of rachis-costa junction and the hairs at abaxial side of leaf axes. The Polystichopsis–Trichoneuron clade was found to form the sister clade to an entirely Neotropical clade comprising Polybotrya and its relatives. The new subfamily Polybotryoideae is introduced based on the presented observations. In turn, the newly recovered sister relationship between Polystichopsis and Trichoneuron provides evidence for geographic disjunctions involving the Caribbean islands and the Indo–Burma biodiversity hotspot.

Out of Africa: evidence of the obligate mutualism between long corolla tubed plant and long-tongued fly in the Himalayas.

Summary Mutualism between long corolla tubed plants and their potential pollinators, long‐tongued flies, is a classic example of coevolution, but to date, has only been reported from the regions of southern Africa. Many plant species from the Himalayas also show botanical characteristics that could be consistent with pollination by long‐tongued flies. Here, we seek the evidence of the “long‐tongued‐long tubed fly/flower” mutualism out of Africa, in a different continent and climatic region, the Himalayas.Floral traits of Himalayan region endemic alpine genus, Roscoea, indicate possible mutualism with long‐tongued flies for pollination success; however, effective pollinators of this genus are yet unknown. This study investigates whether long‐tongued flies and Roscoea purpurea in Nepal Himalayas show exclusive mutualism for their survival/reproduction.We made extensive observations of floral visitors of R. purpurea and food source of Philoliche longirostris across their wide ranges of populations in Nepal Himalayas for three consecutive years (2012–2014). To confirm the obligate reliance of R. purpurea upon P. longirostris for pollination success, manipulated pollination experiments were conducted at two populations for 2 years. Similarly foraging behavior, visitation frequency, and pollination efficiency of P. longirostris were assessed at two populations for 2 years, and its contribution for the reproductive success of R. purpurea was evaluated. Our results indicate that R. purpurea is self‐compatible but lacks autonomous selfing and obligatorily relies on P. longirostris for reproductive success. Across all populations, P. longirostris was observed as an exclusive and highly efficient pollinator of R. purpurea, while P. longirostris exclusively depends up on R. purpurea for food source.Out of Africa, this study provides the first evidence of long‐tongued fly pollination system and indicates the possibility of additional instances of such a rare phenomenon in the Himalayas. Finding of specialized pollinator of Roscoea only at its evolutionary center indicates that Roscoea species are originally pollinated by long‐tongued flies. Spatial mismatch with specialized pollinators may have induced the evolution of autonomous selfing in North Indochinese clades of Roscoea. This finding thus substantiates how geographic disjunction causes the shifting of pollination mechanism in closely related plant species.

Miscellaneous additions to Swartzia (Fabaceae) from Chocoan and Andean Colombia

Three new species of Swartzia are described and illustrated. All three are endemic to the western-Andean region and Pacific lowlands of Colombia, an important secondary area of diversity for this Amazonian-centered genus. Swartzia amabale is a multifoliolate member of the predominantly Amazonian section Unifoliolatae. It is closely related to S. glabrata of the eastern Guiana Shield and is one of only two species of its section that occurs outside of Amazonia. Swartzia radiale belongs to the small section Pittierianae and is notable for its nearly actinomorphic androecium and relatively high-elevation habitat. Swartzia versicolor is one of three subtly distinct species of the distinctive section Digynae. Its discovery augments a pronounced pattern of geographical disjunction, the other two species of the section being distributed in and around the Guiana Shield and in the littoral zone of eastern Brazil, respectively. The conservation status of each of the three new species is of concern, as indicated by small geographical ranges, rarity, and the ongoing fragmentation of forests in western Colombia.

Is Ronnbergia (Bromeliaceae, Bromelioideae) a geographically disjunct genus? Evidence from morphology and chloroplast DNA sequence data

A phylogenetic study testing the monophyly of the geographically disjunct genus Ronnbergia (Bromeliaceae, Bromelioideae) is presented. The phylogenetic analyses were based on taxon sampling that included all but one species of Ronnbergia, and representative lineages across the subfamily Bromelioideae. Three chloroplast DNA sequence markers (matK, psbA-trnH, and trnL-trnF) and morphological data were used for the phylogenetic reconstruction. Both the molecular and morphological datasets supported the polyphyly of Ronnbergia, either independently or in combination. These findings suggest that the geographic disjunction of this genus is most likely a product of taxonomic misinterpretation. The results also indicate that the species currently circumscribed in Ronnbergia are closely related to species in the genus Aechmea with similar geographic ranges. The datasets do not have enough resolution power to reconstruct a deep phylogenetic history that involves all the species of Ronnbergia. Nevertheless, this study provides clues for future approaches that should focus on a larger species sampling and the use of multi-locus DNA sequence data.

Identification of the notothenioid sister lineage illuminates the biogeographic history of an Antarctic adaptive radiation.

BackgroundAntarctic notothenioids are an impressive adaptive radiation. While they share recent common ancestry with several species-depauperate lineages that exhibit a relictual distribution in areas peripheral to the Southern Ocean, an understanding of their evolutionary origins and biogeographic history is limited as the sister lineage of notothenioids remains unidentified. The phylogenetic placement of notothenioids among major lineages of perciform fishes, which include sculpins, rockfishes, sticklebacks, eelpouts, scorpionfishes, perches, groupers and soapfishes, remains unresolved. We investigate the phylogenetic position of notothenioids using DNA sequences of 10 protein coding nuclear genes sampled from more than 650 percomorph species. The biogeographic history of notothenioids is reconstructed using a maximum likelihood method that integrates phylogenetic relationships, estimated divergence times, geographic distributions and paleogeographic history.ResultsPercophis brasiliensis is resolved, with strong node support, as the notothenioid sister lineage. The species is endemic to the subtropical and temperate Atlantic coast of southern South America. Biogeographic reconstructions imply the initial diversification of notothenioids involved the western portion of the East Gondwanan Weddellian Province. The geographic disjunctions among the major lineages of notothenioids show biogeographic and temporal correspondence with the fragmentation of East Gondwana.ConclusionsThe phylogenetic resolution of Percophis requires a change in the classification of percomorph fishes and provides evidence for a western Weddellian origin of notothenioids. The biogeographic reconstruction highlights the importance of the geographic and climatic isolation of Antarctica in driving the radiation of cold-adapted notothenioids.

Distrianthes exxonmobilensis (Loranthaceae), a new species in a formerly monotypic genus from Papua New Guinea

Distrianthes exxonmobilensis is described from karst environments along the PNG LNG Pipeline in southern New Guinea. It is the second species in a genus previously regarded as monotypic. The new loranth is distinguished by an inflorescence reduced to a single flower or triad, and by the geographic disjunction from previous generic localities.

Environmental niche and distribution of six deciduous tree species in the Spanish Atlantic region

Abstract: Understanding the influence of environmental factors on the distribution of tree species is essential for developing management actions at regional level. We computed species distribution models for six European tree species to determine their potential niche in the Spanish Atlantic region, where deciduous forests are relatively well preserved. We used data from the national Forest Inventory and topo-climatic and soil variables to construct distribution models by the Generalized Linear Model procedure. The main factors found to determine the presence of the selected species were minimum winter temperature and mineral fertility of soils. Suitable habitats for Quercus petraea and F. sylvatica were mainly high-altitude areas with low minimum temperatures. In contrast, Q. robur and C. sativa were restricted to low altitudes and warmer conditions. Betula pubescens was not influenced by the elevation, probably because it is adapted to Atlantic conditions, and distribution of this species was associated with low fertility soils. Although the submediterranean Q. pyrenaica was positively influenced by the slope, model performance was poor for this species, possibly because of the truncated environmental range of the species in the study area. The findings suggest that temperature rather than moisture is shaping the distribution of deciduous trees at the southern limit of the Atlantic biogeographic region. We also note that the strong elevational difference between the warm coast and the cold mountains may determine the geographical disjunction between Q. robur and Q. petraea in southern Europe.

Disjunct, highly divergent genetic lineages within two rareEremophila(Scrophulariaceae: Myoporeae) species in a biodiversity hotspot: implications for taxonomy and conservation

Effective conservation management should target appropriate conservation units, but evolutionarily and genetically divergent lineages within nominal taxa are often unrecognized. The south-western Australian biodiversity hotspot may harbour many cryptic taxa, as it contains many plant species with naturally fragmented population distributions. Using microsatellite markers, we tested the hypothesis that disjunct population groups in the rare species Eremophila microtheca and E. rostrata (Scrophulariaceae: Myoporeae) are highly genetically divergent and represent separate evolutionarily significant units (ESUs). Chromosome counts indicated that all individuals assessed were diploid (2n = 36). Genetic differentiation among disjunct population groups was highly significant (P < 0.001) for both E. microtheca (FST = 0.301–0.383; Dest = 0.756–0.774) and E. rostrata (FST = 0.325–0.346; Dest = 0.628–0.660), and was similar to their differentiation from allied species. These results, including high incidences of private alleles, suggest historical divergence among cryptic taxa within E. microtheca and E. rostrata. Population groups in E. rostrata have recently been taxonomically recognized as two subspecies. Our study suggests that E. microtheca should also be reassessed as two taxa or considered as two ESUs, and the southern occurrence should be listed as Critically Endangered. We suggest a precautionary approach for flora in this and similar landscapes, whereby historically wide geographical disjunctions are assumed to indicate separate units for conservation. © 2014 State of Western Australia. Botanical Journal of the Linnean Society © 2014 The Linnean Society of London, 2015, 177, 96–111.

Evolutionary history of a vanishing radiation: isolation-dependent persistence and diversification in Pacific Island partulid tree snails.

BackgroundPartulid tree snails are endemic to Pacific high islands and have experienced extraordinary rates of extinction in recent decades. Although they collectively range across a 10,000 km swath of Oceania, half of the family’s total species diversity is endemic to a single Eastern Pacific hot spot archipelago (the Society Islands) and all three partulid genera display highly distinctive distributions. Our goal was to investigate broad scale (range wide) and fine scale (within‐Society Islands) molecular phylogenetic relationships of the two widespread genera, Partula and Samoana. What can such data tell us regarding the genesis of such divergent generic distribution patterns, and nominal species diversity levels across Oceania?ResultsMuseum, captive (zoo) and contemporary field specimens enabled us to genotype 54 of the ~120 recognized species, including many extinct or extirpated taxa, from 14 archipelagoes. The genera Partula and Samoana are products of very distinct diversification processes. Originating at the western edge of the familial range, the derived genus Samoana is a relatively recent arrival in the far eastern archipelagoes (Society, Austral, Marquesas) where it exhibits a stepping‐stone phylogenetic pattern and has proven adept at both intra‐and inter‐ archipelago colonization. The pronounced east–west geographic disjunction exhibited by the genus Partula stems from a much older long-distance dispersal event and its high taxonomic diversity in the Society Islands is a product of a long history of within‐archipelago diversification.ConclusionsThe central importance of isolation for partulid lineage persistence and diversification is evident in time-calibrated phylogenetic trees that show that remote archipelagoes least impacted by continental biotas bear the oldest clades and/or the most speciose radiations. In contemporary Oceania, that isolation is being progressively undermined and these tree snails are now directly exposed to introduced continental predators throughout the family’s range. Persistence of partulids in the wild will require proactive exclusion of alien predators in at least some designated refuge islands.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0202-3) contains supplementary material, which is available to authorized users.

The remarkable congruence of New and Old World savanna origins.

The remarkable congruence of New and Old World savanna origins.