Disjunct Range Research Articles

Phylogeographical study of the alpine plantCassiope lycopodioides(Ericaceae) suggests a range connection between the Japanese archipelago and Beringia during the Pleistocene

Given that East Asia is located south-west of Beringia and was less glaciated during the Pleistocene, species at higher latitudes were able to expand their range in this region during climate cooling. Although southward migration is an inevitable colonization process, the biogeographical history of the disjunct ranges of higher-latitude species in East Asia has been investigated less extensively. Here, we assess whether their disjunct distributions in the Japanese archipelago connected sufficiently with Beringia or persisted in isolation following their establishment. Sequences of nine nuclear loci were determined for Cassiope lycopodioides (Ericaceae) from the Japanese archipelago as well as its surrounding areas, Kamchatka and Alaska. According to the geographical pattern of genetic diversity, the northern populations from Kamchatka to the northern part of the Japanese archipelago were similar genetically and were differentiated from populations in central Japan. Our study suggested that the distribution of C. lycopodioides was connected between the northern part of the Japanese archipelago and south-western Beringia due to Pleistocene climate cooling. Conversely, central Japan harboured a disjunct range after its establishment. These inferences suggest that widespread range expansion in northern East Asia was plausible for species distributed in Beringia. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 497–509.

Effect of a Geographic Barrier on Adaptation in the Dwarf Sunflower (Helianthus pumilusNutt.)

Premise of research. Geographic isolation promotes local adaptation but may also prevent the movement of advantageous gene complexes throughout a species distribution. We identify a geographic barrier that inhibits gene flow and adaptation across the disjunct species range of the Rocky Mountain endemic sunflower Helianthus pumilus.Methodology. Habitat suitability modeling and least-cost path analysis were used to characterize environmental preferences across the species range and to identify barriers to gene flow. Simple sequence repeat data were used to assess genetic structure and estimate recent levels of gene flow across the distributional disjunction. A common garden was used to study phenotypic differentiation and local adaptation. Controlled crosses tested for intrinsic barriers to reproduction.Pivotal results. Despite significant differences in available habitat, individuals in northern and southern regions occupy similar sites, suggesting limited adaptive differentiation in environmental preferen...

Taiwanese montaneSambucus chinensisseeds require warm stratification, contrasting with other congeneric temperate members

AbstractMany temperate plant genera, likeSambucus, have species with range disjunctions among North America, Europe and/or Asia. Cold stratification (sometimes in combination with warm stratification) is the primary mechanism to break seed dormancy in these species. For some of these genera showing Northern Hemispheric disjunctions, members also occur in subtropical or tropical regions, mostly confined to higher elevations where climate and vegetation differ from those in northern latitudes. We made two hypotheses concerning germination for the subtropical TaiwaneseSambucus chinensis: (1) seeds from populations exposed to warm temperatures would require warm stratification, and (2) seeds from populations exposed to cold temperatures need cold stratification. We investigated the germination (including embryo growth) of non-stratified seeds over a range of temperatures and tested the effects of cold stratification and of gibberellins GA3and GA4on germination. The amount and timing of germination among populations varied substantially in response to temperature treatments. Seeds from all populations of this species required warm temperatures for dormancy break and germination, regardless of environmental conditions. As such, the majority of seeds had non-deep simple morphophysiological dormancy, which, until now, has not been reported in any members ofSambucus. The seed characteristics of the subtropicalS. chinensisare different from those of temperate members of the genus in which cold stratification is the predominate treatment to overcome dormancy.

Phylogeography and cryptic introduction of the ragworm Hediste diversicolor (Annelida, Nereididae) in the Northwest Atlantic

AbstractMany benthic marine invertebrates show striking range disjunctions across broad spatial scales. Without direct evidence for endemism or introduction, these species remain cryptogenic. The common ragworm Hediste diversicolor plays a pivotal role in sedimentary littoral ecosystems of the North Atlantic as an abundant prey item and ecosystem engineer, but exhibits a restricted dispersal capacity that may limit connectivity at both evolutionary and ecological time scales. In Europe, H. diversicolor is subdivided into cryptic taxa and genetic lineages whose distributions have been modified by recent invasions. Its origin in the northwest Atlantic has not been adequately addressed. To trace the age and origin of North American ragworm populations, we analyzed mtDNA sequence data (COI) from the Gulf of Maine and Bay of Fundy (n=73 individuals) and compared our findings with published data from the northeast Atlantic. Our results together with previous data indicate that two species of the H. diversicolor complex have independently colonized the northwest Atlantic at least three different times, resulting in two distinct conspecific assemblages in the Bay of Fundy and Gulf of Maine (respectively) that are different from the species found in the Gulf of St. Lawrence. North American populations had significantly lower genetic diversity compared with populations in the northeast Atlantic, and based on patterns of shared identity, populations in the Bay of Fundy originated from the Baltic Sea and North Sea. Populations from the Gulf of Maine were phylogenetically distinct and most likely originated from unsampled European populations. Analyses of the North American populations revealed patterns of post‐colonization gene flow among populations within the Gulf of Maine and Bay of Fundy. However, we failed to detect shared haplotypes between the two regions, and this pattern of complete isolation corroborates a strong phylogeographic break observed in other species.

Riella cossonianaTrab. (Riellaceae, Marchantiophyta) New to France

Riella (Riellaceae, Sphaerocarpales) is a genus of aquatic liverworts with disjunct range in areas of Mediterranean-type climates. Riella has been traditionally subdivided into two subgenera, subgenus Riella, whose plants show smooth or papillose female involucres and Trabutiella, whose plants show winged female involucres. To date only three species of Riella are known in France, all belonging to subgenus Riella. During the course of a study of the plant diversity of temporary brackish ponds in the Camargue area (Southern France), soil sediments were collected from 10 localities and cultivated in the laboratory. From cultures of five of these localities emerged dioicous plants of Riella showing winged female involucres that unambiguously assigned them to subgenus Trabutiella. The study of those specimens with Light and Scanning Electron Microscopy allowed us to identify them as R. cossoniana var. cossoniana. Fresh materials allowed for detailed morphological analyses on these new French materials which were fully described and illustrated. These findings represent the first report of a species belonging to subgenus Trabutiella from France and the second European country where R. cossoniana is reported. Four nearby populations occur within the perimeter of the Tour du Valat Regional Natural Reserve, and another in the industrial polygon of the Grand Port Maritime de Marseille.

Delineation of conservation units in an endangered marsupial, the southern brown bandicoot (Isoodon obesulus obesulus), in South Australia/western Victoria, Australia

Conservation programs for threatened species are greatly benefiting from genetic data, for their power in providing knowledge of dispersal/gene flow across fragmented landscapes and for identifying populations of high conservation value. The endangered southern brown bandicoot (Isoodon obesulus obesulus) has a disjunct distribution range in South Australia, raising the possibility that populations of the subspecies may represent distinct conservation units. In the current study, we used a combination of 14 microsatellite and two mitochondrial sequence markers to investigate the phylogeography and population structure of I. o. obesulus in South Australia and south-western Victoria, with the aim of identifying any potential evolutionarily significant units and management units relevant to conservation management. Our phylogenetic/population analyses supported the presence of two distinct evolutionary lineages of I. o. obesulus. The first lineage comprised individuals from the Mount Lofty Ranges, Fleurieu Peninsula and Kangaroo Island. A second lineage comprised individuals from the south-east of South Australia and south-western Victoria. We propose that these two lineages represent distinct evolutionarily significant units and should be managed separately for conservation purposes. The findings also raise significant issues for the national conservation status of I. o. obesulus and suggest that the current subspecies classification needs further investigation.

Niche conservatism of Eulophia alta, a trans-Atlantic orchid species

The genus <em>Eulophia</em> embraces over 230 species distributed through the tropical and subtropical Africa, Asia, Australia and the Americas. In Neotropics it is represented by a sole species – <em>E. alta</em>. The aim of the presented study was to evaluate the difference between ecological niches occupied by American and African populations of this species based on the ecological niche modeling. The similarity between the glacial and present niches occupied by <em>E. alta</em> was calculated and the factors limiting the species occurrence were identified. Areas of seasonal tropical forest, tropical savanna and woodland served as refugia for the studied species during last glacial maximum and they were more widespread in Neotropics than in Africa. No significant niche shift after last glacial maximum was observed. The distribution of <em>E. alta</em> in its whole range is restricted mainly by temperature seasonality. The differences in the niches occupied by African and Neotropical populations of <em>E. alta</em> suggest preglacial disjunction of the species range and independent adaptation of both groups. Despite the significant range disjunction of <em>E. alta</em> the species is characterized by relatively high degree of niche conservatism.

Mind the gaps: investigating the cause of the current range disjunction in the Cape Platanna,Xenopus gilli(Anura: Pipidae)

Low-lying areas of the Cape at Africa’s south-westernmost tip have undergone dramatic marine-remodelling, with regular changes in sea-level following glacial cycles. Species for which marine barriers are impenetrable underwent concomitant radical distribution changes which may account for current range disjunctions. The Cape platanna, Xenopus gilli, is a frog distributed in only three disjunt areas within low-lying regions of the southwestern Cape. We determined the relationship between frogs from these three disjunct areas, by using a combination of morphometric analysis and mtDNA (ND2 and 16S fragments) sequences of 130 frogs from eight ponds. Coalescent analyses on molecular data dated the divergence in two major clades to around 4.6 Mya, a period during which major uplifting on the eastern side of the subcontinent caused climate changes throughout southern Africa. Principal components analysis showed significant morphometric differences between each clade on head and limb measurements. Consistent differences in ventral colouration and patterning were also observed. We report on increased levels of hybridisation with X. laevis throughout the range of X. gilli, which reaches at least 27% hybrids in some ponds. Urgent conservation actions are required to control habitat loss from alien invasive vegetation, and prevent introgression with the domestic-exotic, X. laevis.

A new treefrog of theLitoria gracilentagroup (Hylidae) from Papua New Guinea

I describe a new treefrog of the Litoria gracilenta group from the lowlands along an outlying volcanic peak in southeastern Papua New Guinea. The new species is distinctive among members of that group in a combination of details of color pattern and morphometric characters, and it is further unique within that group in being the only species known to have a call consisting of several notes. It is also unusual for the group in having been found breeding in a stream. This species complex has an extensive but disjunct range spanning the entire extent of New Guinea, outlying islands to the west and the east, and eastern Australia. The new species fills in a range gap of 830 km between its nearest relatives to the northwest and southeast.

Dynamics of the range of lily leaf beetle (Lilioceris lilii, Chrysomelidae, Coleoptera) indicates its invasion from Asia to Europe in the 16th–17th century

An analysis of 415 locations of Lilioceris lilii (Scopoli, 1763), a pest of ornamental liliaceous, allowed tracing the dynamics of the species range in Eurasia from the 18th century to the present. Now the area of distribution is a continuous band across the whole continent, from Portugal to the Khabarovsk krai, but until the end of the 19th century, the range was disjunctive. It consisted of two large subranges: European and Asian. There was a gap of about 2000 km between them. The easternmost of the known European locations of the 19th century lies in Voronezh oblast, while the far west of the Asian location is in the vicinity of Omsk. In Asia, the species ranged in Siberia, the Far East, and northern China. Taking into account the Asian origin of host plants of the lily beetle, as well as the genus Lilioceris in general, it can be assumed that the European subrange is secondary, invasive. The disjunctive range could hardly be of relict origin, since L. lilii can quickly establish and develop vast territories in decades. This ability of the lily beetle is evidenced by the distribution of this invasive species in Britain, Canada, and the United States. From the literature, it is known that in 1688 the lily beetle already inhabited Western Europe, and Siberian species of lilies were first brought there in 1596. Apparently, the pest was introduced together with planting material in this time interval. By the mid-20th century, L. lilii had settled in the Volga region, the Urals, and the south of Western Siberia. Thus, the range gap virtually ceased to exist. In recent decades, the range in the European part of Russia has expanded to the north and northeast. By now, the lily leaf beetle has populated even some areas where its host plants are found only as cultivated or adventive plants.

The cryptic and the apparent reversed: lack of genetic differentiation within the morphologically diverse plexus of the planktonic foraminifer Globigerinoides sacculifer

Previous genetic studies of extant planktonic foraminifera have provided evidence that the traditional, strictly morphological definition of species in these organisms underestimates their biodiversity. Here, we report the first case where this pattern is reversed. The modern (sub)tropical species plexus Globigerinoides sacculifer is characterized by large morphological variability, which has led to the proliferation of taxonomic names attributed to morphological end-members within the plexus. In order to clarify the taxonomic status of its morphotypes and to investigate the genetic connectivity among its currently partly disjunct (sub)tropical populations, we carried out a global survey of two ribosomal RNA regions (SSU and ITS-1) in all recent morphotypes of the plexus collected throughout (sub)tropical surface waters of the global ocean. Unexpectedly, we find an extremely reduced genetic variation within the plexus and no correlation between genetic and morphological divergence, suggesting taxonomical overinterpretation. The genetic homogeneity within the morphospecies is unexpected, considering its partly disjunct range in the (sub)tropical Atlantic and Indo-Pacific and its old age (early Miocene). A sequence variant in the rapidly evolving ITS-1 region indicates the existence of an exclusively Atlantic haplotype, which suggests an episode of relatively recent (last glacial) isolation, followed by subsequent resumption of unidirectional gene flow from the Indo-Pacific into the Atlantic. This is the first example in planktonic foraminifera where the morphological variability in a morphospecies exceeds its rDNA genetic variability. Such evidence for inconsistent scaling of morphological and genetic diversity in planktonic foraminifera could complicate the interpretation of evolutionary patterns in their fossil record.

An Extra-Limital Population of Black-tailed Prairie Dogs, <em>Cynomys ludovicianus</em>, in Central Alberta

An introduced population of Black-tailed Prairie Dogs, Cynomys ludovicianus, has persisted for the past 50 years east of Edmonton, Alberta, over 600 km northwest of the natural prairie range of the species. This colony has slowly expanded at this northern latitude within a transition ecotone between the Boreal Plains ecozone and the Prairies ecozone. Although this colony is derived from escaped animals, it is worth documenting, as it represents a significant disjunct range extension for the species and it is separated from the sylvatic plague (Yersina pestis) that threatens southern populations. The unique northern location of these Black-tailed Prairie Dogs makes them valuable for the study of adaptability and geographic variation, with implications for climate change impacts on the species, which is threatened in Canada.

Palaeodistribution modelling and genetic evidence highlight differential post‐glacial range shifts of a rain forest conifer distributed across a latitudinal gradient

AbstractAim We examine the range expansion/contraction dynamics during the last glacial cycle of the late‐successional tropical rain forest conifer Podocarpus elatus using a combination of modelling and molecular marker analyses. Specifically, we test whether distributional changes predicted by environmental niche modelling are in agreement with (1) the glacial maximum contractions inferred from the southern fossil record, and (2) population genetic‐based estimates of range disjunctions and demographic dynamics. In addition, we test whether northern and southern ranges are likely to have experienced similar expansion/contraction dynamics.Location Eastern Australian tropical and subtropical rain forests.Methods Environmental niche modelling was completed for three time periods during the last glacial cycle and was interpreted in light of the known palynology. We collected 109 samples from 32 populations across the entire range of P. elatus. Six microsatellite loci and Bayesian coalescence analysis were used to infer population expansion/contraction dynamics, and five sequenced loci (one plastid and four nuclear) were used to quantify genetic structure/diversity.Results Environmental niche modelling suggested that the northern and southern ranges of P. elatus experienced different expansion/contraction dynamics. In the northern range, the habitat suitable for P. elatus persisted in a small refugial area during the Last Glacial Maximum (LGM, 21 ka) and then expanded during the post‐glacial period. Conversely, in the south suitable habitat was widespread during the LGM but subsequently contracted. These differential dynamics were supported by Bayesian analyses of the population genetic data (northern dispersal) and are consistent with the greater genetic diversity in the south compared with the north. A contact zone between the two genetically divergent groups (corresponding to the Macleay Overlap Zone) was supported by environmental niche modelling and molecular analyses.Main conclusions The climatic fluctuations of the Quaternary have differentially impacted the northern and southern ranges of a broadly distributed rain forest tree in Australia. Recurrent contraction/expansion cycles contributed to the genetic distinction between northern and southern distributions of P. elatus. By combining molecular and environmental niche modelling evidence, this unique study undermines the general assumption that broadly distributed species respond in a uniform way to climate change.

Recent phylogeographic structure in a widespread ‘weedy’ Neotropical tree species, Cordia alliodora (Boraginaceae)

AbstractAim Although hundreds of tree species have broad geographic ranges in the Neotropics, little is known about how such widespread species attained disjunct distributions around mountain, ocean and xeric barriers. Here, we examine the phylogeographic structure of a widespread and economically important tree, Cordia alliodora, to: (1) test the roles of vicariance and dispersal in establishing major range disjunctions, (2) determine which geographic regions and/or habitats contain the highest levels of genetic diversity, and (3) infer the geographic origin of the species.Location Twenty‐five countries in Central and South America, and the West Indies.Methods Chloroplast simple sequence repeats (cpSSR; eight loci) were assayed in 67 populations (240 individuals) sampled from the full geographic range of C. alliodora. Chloroplast (trnH–psbA) and nuclear (internal transcribed spacer, ITS) DNA sequences were sampled from a geographically representative subset. Genetic structure was determined with samova, structure and haplotype networks. Analysis of molecular variance (AMOVA) and rarefaction analyses were used to compare regional haplotype diversity and differentiation.Results Although the ITS region was polymorphic it revealed limited phylogeographic structure, and trnH–psbA was monomorphic. However, structure analysis of cpSSR variation recovered three broad demes spanning Central America (Deme 1), the Greater Antilles and the Chocó (Deme 2), and the Lesser Antilles and cis‐Andean South America (Deme 3). samova showed two predominant demes (Deme 1 + 2 and Deme 3). The greatest haplotype diversity was detected east of the Andes, while significantly more genetic variation was partitioned among trans‐Andean populations. Populations experiencing high precipitation seasonality (dry ecotype) had greater levels of genetic variation.Main conclusions Cordia alliodora displayed weak cis‐ and trans‐Andean phylogeographic structure based on DNA sequence data, indicative of historical dispersal around this barrier and genetic exchange across its broad range. The cpSSR data revealed phylogeographic structure corresponding to three biogeographic zones. Patterns of genetic diversity are indicative of an origin in the seasonally dry habitats of South America. Therefore, C. alliodora fits the disperser hypothesis for widespread Neotropical species. Dispersal is evident in the West Indies and the northern Andean cordilleras. The dry ecotype harbours genetic variation that is likely to represent the source for the establishment of populations under future warmer and drier climatic scenarios.

Cyclopes didactylus(Pilosa: Cyclopedidae)

Cyclopes didactylus (Linnaeus, 1758) is a small, arboreal anteater commonly called the silky anteater. This nocturnal denizen of diverse forests has a disjunct range with a western population from Central America into South America and an eastern population in the Atlantic rain forest of Brazil. The main population of C. didactylus is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources, but habitat loss and sugarcane production threatens its habitat in the Atlantic rain forest.

Testing the effect of transient Plio-Pleistocene barriers in monsoonal Australo-Papua: did mangrove habitats maintain genetic connectivity in the Black Butcherbird?

Changes in climate and sea level are hypothesized to have promoted the diversification of biota in monsoonal Australia and New Guinea by causing repeated range disjunctions and restricting gene flow between isolated populations. Using a multilocus (one mtDNA locus, five nuclear introns) phylogeographic approach, we test whether populations of the mangrove and rainforest restricted Black Butcherbird (Cracticus quoyi) have diverged across several geographic barriers defined a priori for this region. Phylogeographic structure and estimates of divergence times revealed Plio-Pleistocene divergences and long-term restricted gene flow of populations on either side of four major geographic barriers between and within Australia and New Guinea. Overall, our data are consistent with the hypothesis that mesic-adapted species did not disperse across the open dry woodlands and grasslands that dominated the transient palaeo-landbridges during the Plio-Pleistocene despite the presence of mangrove forests that might have acted as dispersal corridors for mesic-adapted species. Our study offers one of the first multilocus perspectives on the impact of changes in climate and sea level on the population history of widespread species with disjunct ranges in Australia and New Guinea.

Recent vicariance and the origin of the rare, edaphically specialized Sandhills lily, Lilium pyrophilum (Liliaceae): evidence from phylogenetic and coalescent analyses

Establishing the phylogenetic and demographic history of rare plants improves our understanding of mechanisms that have led to their origin and can lead to valuable insights that inform conservation decisions. The Atlantic coastal plain of eastern North America harbours many rare and endemic species, yet their evolution is poorly understood. We investigate the rare Sandhills lily (Lilium pyrophilum), which is endemic to seepage slopes in a restricted area of the Atlantic coastal plain of eastern North America. Using phylogenetic evidence from chloroplast, nuclear internal transcribed spacer and two low-copy nuclear genes, we establish a close relationship between L. pyrophilum and the widespread Turk's cap lily, L. superbum. Isolation-with-migration and coalescent simulation analyses suggest that (i) the divergence between these two species falls in the late Pleistocene or Holocene and almost certainly post-dates the establishment of the edaphic conditions to which L. pyrophilum is presently restricted, (ii) vicariance is responsible for the present range disjunction between the two species, and that subsequent gene flow has been asymmetrical and (iii) L. pyrophilum harbours substantial genetic diversity in spite of its present rarity. This system provides an example of the role of edaphic specialization and climate change in promoting diversification in the Atlantic coastal plain.

Phylogeography and the origins of range disjunctions in a north temperate fish, the pygmy whitefish (Prosopium coulterii), inferred from mitochondrial and nuclear DNA sequence analysis

Aim To investigate the degree of phylogeographical divergence within pygmy whitefish (Prosopium coulterii) and to test hypotheses concerning the origin of disjunct populations within North America.

Confirmation ofObovaria olivaria, Hickorynut Mussel (Bivalvia: Unionidae), in the Mississagi River, Ontario, Canada

A significant and recruiting population of Obovaria olivaria (Hickorynut Mussel) was confirmed in the Mississagi River, Lake Huron drainage, ON, Canada. This large river unionid mussel is known to use Acipenser fulvescens (Lake Sturgeon) and Scaphirhynchus platorynchus (Shovelnose Sturgeon) as hosts. The Mississagi River is known to have a spawning Lake Sturgeon population. In 9.1 person-hours of snorkel and SCUBA searches, 10 live O. olivaria ranging in length from 36 to 79 mm, including six gravid females, were collected in sandy substrates with water depths from 1.5 to 4 m. Obovaria olivaria in the Mississagi River represent a significant range disjunction from the other extant populations in Canada in the Ottawa and St. Lawrence river drainages. As the conservation status of this rare mussel in Canada is assessed, the geographic genetic population structure and spatial extent among known areas should be studied to understand the post-glacial redistribution of the species.

Choloepus hoffmanni (Pilosa: Megalonychidae)

Choloepus hoffmanni Peters, 1858 (Hoffmann's two-toed sloth) is 1 of 2 extant two-toed sloths. A high-canopy folivore, C. hoffmanni has a disjunct range with a northern population in Central America and northern South America and a southern population in South America. C. hoffmanni is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources because of its wide distribution.