Distance Dispersal Events Research Articles

Geography and ecology structure diversification in Ziziphus Mill. (Rhamnaceae)

Understanding the processes responsible for creating and preserving biodiversity within tropical ecosystems is essential for gaining deeper insights into the history, dynamics, and resilience of these environments. We investigated the biogeography and evolution of Ziziphus Mill. (Rhamnaceae), a genus of c.50 species found in all major tropical biomes and across Africa, Asia and Australasia to evaluate how ecology and geography structures its diversification, and their associations with functional traits. We used consistency and retention indices, as well as the delta statistic to test for phylogenetic signal in ecology, geography and functional traits. We constructed a time-calibrated phylogeny using BEAST, followed by the reconstruction of biome and geographical affinities in BioGeoBEARS, and ancestral functional trait evolution using phytools and ape. At a global scale, geography structures Ziziphus’ diversification more than ecology, as evidenced by higher phylogenetic signal in retention indices and the delta statistic. Multiple ecological switches among biomes are associated with dispersal events, which structure Ziziphus’ diversification at smaller scales. Biogeographic estimation suggests that Ziziphus evolved out of closed biomes in Asia during the Oligocene. Long distance dispersal from Asia to Africa resulted in the occupation of two novel biomes, the expanding tropical grassy biome and the desertic biome. Geographic transitions across continents that retain the same biome are fewer but are demonstrated by a dispersal from the closed biome in Asia to the same ecological setting in Australia. In keeping with the younger age of the savanna biome and the Pliocene radiation of geoxylic species, the youngest species in Ziziphus are mostly found in open biomes, and the youngest habit is geoxylic. Leaf hair appears to confer advantages across biomes whilst being a synapomorphy for open and desertic clades. One of two evolutions back into closed biomes is associated with the development of the liana habit. We inferred the most complete phylogeny for Ziziphus to date. Ziziphus originated in closed biomes in Asia in the Oligocene. At a global scale, geography structures diversification more than ecology (biome preference) in Ziziphus. Biome shifts are frequently associated with long distance dispersal events. Shifts in growth form are frequently associated with biome shifts.

Bioclimatic and local drivers modulating the expansion of an introduced temperate reptile in a subtropical island

Extensive human-mediated translocation of species from their native ranges to alien environments is a trademark of the Anthropocene. Particularly in island ecosystems, established non-native species often have highly detrimental impacts on native taxa and thus the study of the drivers mediating the establishment and expansion of introduced species in areas outside their native range is crucial to delineate timely and effective mitigation measures. Species distribution models (SDMs) are widely used in invasion biology and offer great potential for the assessment of invasion risk and the identification of areas likely to be colonized by expanding alien species. Within reptiles, Gekkonidae is the second family with most introductions globally, a reflection of the group’s capacity to survive long distance dispersal events. The temperate Moorish gecko ( Tarentola mauritanica ) is native to the Mediterranean basin but has established alien populations in multiple localities throughout the word. It was first reported in the subtropical island of Madeira in 1993 and over the last three decades has colonized a substantial section of the island’s south coast. Here, we use Madeira Island as a case study to investigate the interplay between bioclimatic and local scale variables on the occurrence of T. mauritanica in areas outside its native range. We found that the species favors areas with high temperatures during the coldest month, low mean temperatures during the wettest quarter, low annual values of precipitation, and high precipitation during the driest quarter. This translates to an obvious preference for areas with more Mediterranean-like climates which in Madeira are primarily located in the south and south-eastern sections of the island. Additionally, our models predicted that some areas of the northern coast of Madeira offer suitable conditions for the gecko, although no observations have yet been recorded. Tarentola mauritanica is expanding its range in Madeira and has already colonized the nearby island of Porto Santo. It is paramount that more research is devoted to understanding the impact of this alien gecko on the island’s native species and ecosystems, and in particular on its endemic-rich arthropod communities. • The temperate gecko seeks for native-range conditions to prevail in the subtropics. • South and south-east areas of Madeira are particularly suitable for T. mauritanica. • SDMs revealed that T. mauritanica is likely to continue expanding its distribution. • Research on the potential impacts of T. mauritanica on native taxa is needed.

Long distance dispersal of monk parakeets

Invasive species threaten biodiversity all around the world and for this reason, identifying the causes and mitigating their effects is a priority in conservation biology. One of the most important factors when dealing with invasive species is dispersal, because the distribution of dispersal distances among members of a population can greatly affect the rate of spread of these invasive populations. Long distance dispersal events have a disproportionately large influence on dispersal kernel estimations, but because of restricted spatial sampling scales they are difficult to detect. Here we use an extensive database of 3,114 monk parakeets ringed in Barcelona city since 2002 as part of an extensive control program across Catalonia where 3,460 birds have been captured since 2013. Our aim was to describe these long–distance movements of monk parakeets. We recorded dispersal distances of over 10 km for a total of eight individuals. Long–distance dispersions were in all directions and both males and females were involved. While some individuals moved in their first year, others delayed dispersal several years. Given that long–distance dispersal events can have a large influence on the rate of range expansion of invasive species this information can be of great utility when modeling the dispersal and spread of the species.

Reconstructing the nonadaptive radiation of an ancient lineage of ground‐dwelling stick insects (Phasmatodea: Heteropterygidae)

AbstractStick and leaf insects (Phasmatodea) are large terrestrial herbivorous arthropods known for masquerading as plant parts such as bark, twigs and leaves. Their evolutionary history is largely shaped by convergent evolution associated with adaptive radiations on geographically isolated landmasses that have repeatedly generated ground‐dwelling ecomorphs. The members of one lineage, however, the Oriental Heteropterygidae, are morphologically rather uniform, and have a predominantly ground‐dwelling lifestyle. The phylogeny of Heteropterygidae that comprises approximately 130 described species is controversial and remains uncertain. In particular, the systematic position of the giant Jungle Nymph Heteropteryx dilatata, whose males are capable of flight and exhibit the most plesiomorphic wing morphology among extant phasmatodeans, is of major interest to the scientific community. Here, we analysed a set of seven nuclear and mitochondrial genes to infer the phylogeny of Heteropterygidae covering the group's overall diversity. The divergence time estimation and reconstruction of the historical biogeography resulted in an ancestral distribution across Sundaland with long distance dispersal events to Wallacea, the Philippines and the South Pacific. We were able to resolve the relationships among the three principal subgroups of Heteropterygidae and revealed the Dataminae, which contain entirely wingless small forms, as the sister group of Heteropteryginae + Obriminae. Within Heteropteryginae, Haaniella is recovered as paraphyletic in regard to Heteropteryx. Consequently, Heteropteryx must be considered a subordinate taxon deeply embedded within a flightless clade of stick insects. Within Obriminae, the Bornean Hoploclonia is strongly supported as the earliest diverging lineage. Based on this finding, we recognize only two tribes of equal rank among Obriminae, the Hoplocloniini trib. nov. and Obrimini sensu nov. Within the latter, we demonstrate that previous tribal assignments do not reflect phylogenetic relationships and that a basal splitting event occurred between the wing‐bearing clade Miroceramia + Pterobrimus and the remaining wingless Obrimini. The Philippine genus Tisamenus is paraphyletic with regard to Ilocano hebardi, thus, we transfer the latter species to Tisamenus as Tisamenus hebardi comb. nov. and synonymize Ilocano with Tisamenus. We discuss character transformations in the light of the new phylogenetic results and conclude that the current taxonomic diversity appears to be mainly driven by allopatry and not to be the result of niche differentiation. This radiation is thus best described as a nonadaptive radiation.

Historical biogeography of Pomaderris (Rhamnaceae): Continental vicariance in Australia and repeated independent dispersals to New Zealand

AimGondwanan biogeographic patterns include a combination of old vicariance events following the breakup of the supercontinent, and more recent long-distance dispersals across the southern landmasses. Floristic relationships between Australia and New Zealand have mostly been attributed to recent dispersal events rather than vicariance. We assessed the biogeographic history of Pomaderris (Rhamnaceae), which occurs in both Australia and New Zealand, by constructing a time-calibrated molecular phylogeny to infer (1) phylogenetic relationships and (2) the relative contributions of vicariance and dispersal events in the biogeographic history of the genus. LocationAustralia and New Zealand. MethodsUsing hybrid capture and high throughput sequencing, we generated nuclear and plastid data sets to estimate phylogenetic relationships and fossil calibrated divergence time estimates for Pomaderris. BioGeoBEARS and biogeographical stochastic mapping (BSM) were used to assess the ancestral area of the genus and the relative contributions of vicariance vs dispersal, and the directionality of dispersal events. ResultsOur analyses indicate that Pomaderris originated in the Oligocene and had a widespread Australian distribution. Vicariance of western and eastern Australian clades coincides with the uplift of the Nullarbor Plain c. 14 Ma, followed by subsequent in-situ and within-biome diversification with little exchange across regions. A rapid radiation of southeastern Australian taxa beginning c. 10 Ma was the source for at least six independent long-distance dispersal events to New Zealand during the Pliocene–Pleistocene. Main conclusionsOur study demonstrates the importance of dispersal in explaining not only the current cross-Tasman distributions of Pomaderris, but for the New Zealand flora more broadly. The pattern of multiple independent long-distance dispersal events for Pomaderris, without significant radiation within New Zealand, is congruent with other lowland plant groups, suggesting that this biome has a different evolutionary history compared with the younger alpine flora of New Zealand, which exhibits extensive radiations often following single long distance dispersal events.

Morphological and molecular evidence of population divergence in a widespread shorebird across its southern mainland Australian distribution

We characterize geographical variation in the genetics, ecology, morphology and plumage of the Hooded Plover Charadrius cucullatus, a threatened shorebird widespread on coasts (south-east) and saltlakes (south-west) across the southern mainland of Australia. We confirm the distinctness of populations on either side of the Nullabor Plain/Great Australian Bight indicating that this apparent biogeographic barrier to terrestrial flora and fauna also influenced the phylogeographic pattern of a resident shorebird which is dependent on access to saline/hypersaline water. Western birds are genetically distinct, larger and have darker plumage than those in the east. Distinct ecological differences also exist, with eastern birds being resident, usually occurring on ocean beaches, with generalised diets and seasonal, solitary breeding. Western birds are nomadic, breeding when suitable conditions prevail, and exhibit more specialized diets, and may at times breed semi-colonially. Within the extensive eastern population, genetic analyses revealed an isolation by distance pattern, as well as genetic evidence of a long distance dispersal event. South Australian birds are distinct from Victorian birds, but cluster closely with Victorian birds in all genetic analyses. The western population features little genetic structuring, consistent with nomadism and congregatory behavior associated with drought/flood events. The distinctness of western populations found using multiple lines of evidence and the lack of evidence for any recent migration events across the Nullabor Plain, suggests that previously described subspecies warrant reinstatement, and that these evolutionary units require conservation assessment, as has been recognized by national conservation authorities. Conservation management of the eastern population should occur across its distribution, taking care to capture the genetic variability which is evident within this population. Further exploration of genetic variation between Eastern states is suggested.

Transoceanic dispersal of terrestrial species by debris rafting

Rare, long‐distance dispersal events are a key process in generating and maintaining patterns in biological diversity and species distributions across space and time. The 9.0 magnitude earthquake that struck the eastern coast of Japan in 2011, and the subsequent 38 m high tsunami washed large amounts of shoreline debris into the Pacific Ocean that led to a large‐scale biological rafting event carrying nearly 300 marine species to the western shores of North America. Whether oceanic, trans‐Pacific dispersal via rafting generates long distance dispersal events for small, flightless, terrestrial species is unknown. By sampling beach debris associated with known hot‐spots of tsunami debris along the north and east shores of Graham Island, Haida Gwaii, Canada, I document significantly dissimilar invertebrate communities associated with tide‐line beach debris and the occurrence of several putative Japanese species of soil‐dwelling mites (Acari: Oribatida). Previous explanations of Haida Gwaii's unique flora and fauna have been attributed to a proximity to the Beringian land bridge and the accumulated evidence of near‐offshore glacial refugia during the last glacial period. However, my research also suggests that stochastic, trans‐Pacific rafting events contribute to the biodiversity and biogeography of soil communities on the west coast of North America.

The establishment of a pelagic Sargassum population in the tropical Atlantic: Biological consequences of a basin-scale long distance dispersal event

Starting in 2011, coastal areas of the Caribbean Sea and tropical Atlantic Ocean began to experience extraordinary yearly accumulations of pelagic Sargassum brown alga. Historical reports place large quantities of Sargassum only in the North Atlantic (mostly in the Gulf of Mexico and the Sargasso Sea). Accumulations of Sargassum in the tropical Atlantic have continued. We used a numerical particle-tracking system, wind and current reanalysis data, drifting buoy trajectories, and satellite imagery to determine the origin of the Sargassum that is now found persistently in the tropical Atlantic. Our analyses suggest that during the extreme negative phase of the winter 2009–2010 North Atlantic Oscillation (NAO), unusually strong and southward-shifted westerly winds explain the transport of Sargassum from the Sargasso Sea (∼20–40°N, 80–20°W) into the far eastern North Atlantic. Our hindcast Sargassum distributions agree with surface current simulations with the inclusion of “windage”. Windage is the additional, wind-induced drift of material floating at the free surface resulting from direct wind forcing on the sea surface, as well as on floating or partially-submerged objects. In our simulations, windage is included as an added vector (speed and direction) to the model-computed surface ocean currents equivalent to 1% of surface wind velocities. Lagrangian analysis of the regional circulation suggests that (1) part of the Sargassum subsequently drifted to the southwest in the North Equatorial Current (NEC) and entered the central tropical Atlantic, arriving in the Caribbean by the spring of 2011, with (2) another portion continuing southward along the coast of Africa in the Canary Current, eventually joining the seasonally-varying system of tropical Atlantic currents and thereby delivering a large Sargassum population to the tropical Atlantic. Since then, Sargassum patches aggregate from March to September in massive windrows along the Inter-Tropical Convergence Zone (ITCZ) under the action of converging winds. The windrows follow the ITCZ in its seasonal northward migration in the central tropical Atlantic. They are stretched across the central tropical Atlantic as the ITCZ crosses the latitude of the seasonal formation of the North Equatorial Counter Current (NECC). These patches and windrows are exposed to high sunlight and open-ocean upward flux of nutrients due to eddy and wind-driven mixing in the central tropical Atlantic. During the northern spring and summer, as the Sargassum drifts farther north with the ITCZ, large portions of the population are advected into the eastern Caribbean Sea. Some of these patches remain dispersed as the ITCZ migrates southward, and re-aggregate into new windrows as the ITCZ intensifies the following March-April. If wind mixing is strong and the mixed layer is deeper than about 50–60 m in the southern tropical Atlantic at this time, the Sargassum will bloom and form a massive windrow. Otherwise, the bloom will be inhibited. The extreme 2009–2010 NAO wind anomaly could be considered as triggering a biosphere “tipping point” that caused important ocean-scale ecosystem changes in the tropical Atlantic, with significant recurrent social and economic consequences. Understanding whether this new expanded geographic range of massive Sargassum blooms is temporary or whether it will revert to its pre-2009 distribution requires sustained monitoring and research.

Ecological specialization resulting in restricted gene flow promotes differentiation in door snails

We tested the hypothesis that ecological specialization that affects dispersal promotes diversification by a comparison of the genetic structure of two sister species of door snails across their broadly overlapping ranges in the Crimean Mountains. The hypothesized effect of ecological specialization on diversification is supported by STRUCTURE analyses that showed that Mentissa gracilicosta that is restricted to limestone rocks, is subdivided into several distinct clusters, whereas all populations of the species adapted to more continuous habitat, the forests-dwelling Mentissa canalifera, were assigned to a single cluster. Furthermore, it is supported by AMOVAs that showed that a larger part of the genetic variation of M. gracilicosta is apportioned among populations than in M. canalifera. The stronger genetic differentiation of the M. gracilicosta populations corresponds to their more distinct morphological differentiation that resulted in the classification of M. gracilicosta into several geographical subspecies, whereas the more continuously distributed M. canalifera was not subdivided into subspecies. The stronger differentiation of populations of M. gracilicosta compared to M. canalifera can be ascribed to reduced gene flow between the isolated populations of M. gracilicosta and to founder events associated with the long distance dispersal events that are necessary for the colonization of isolated rocks by M. gracilicosta. In Central Europe, the Pleistocene climatic oscillations selected for species with high dispersal abilities, whereas the more stable climate in southern Europe facilitated the non-adaptive radiation of rock-dwelling door snails. Thus, the intrinsic ecological properties of these species groups contributed to the latitudinal diversity gradient.

Landscape and population genetics reveal long distance sharp-tailed grouse (Tympanuchus phasianellus) movements and a recent bottleneck in Minnesota

Sharp-tailed grouse (Tympanuchus phasianellus) are an area-sensitive species that relies on open landscapes of grass and brush. These areas have become highly fragmented in the Great Lakes Region by succession to forest, agriculture, and other human land uses. We used microsatellites in a landscape-genetic approach to identify landscape features that influence movement and connectivity for sharp-tailed grouse in Minnesota, where they have a regional stronghold. Feathers from leks and hunter wing submissions resulted in 367 individuals from the northwest (NW) and 84 from the east-central (EC) management regions. Both the NW and EC regions were genetically diverse and distinct, with high connectivity between them, although it is unclear whether this connection is contemporary or historical. Our analysis indicated that sharp-tailed grouse were structured across regions by land cover or by the amount of agriculture, grasslands, shrublands, and wet meadows on the larger landscape. Numerous long distance dispersal events were detected. Population clustering analysis indicated greatest support for two genetic clusters in the NW and three clusters in the EC region; however, mapping sample locations of individuals by assigned cluster revealed panmixia of clusters in the EC region. High genetic diversity, a low inbreeding coefficient, and significant excess in heterozygosity are consistent with a recent demographic compression or bottleneck in the EC region, and also consistent with surveys indicating a recent decline there. Sustained low population size or further declines would be expected to reduce genetic diversity. We recommend increasing grassland and shrubland quantity and quality to increase population size in the EC region soon.

Microsatellite Analysis and Urediniospore Dispersal Simulations Support the Movement of Puccinia graminis f. sp. tritici from Southern Africa to Australia.

The Australian wheat stem rust (Puccinia graminis f. sp. tritici) population was shaped by the introduction of four exotic incursions into the country. It was previously hypothesized that at least two of these (races 326-1,2,3,5,6 and 194-1,2,3,5,6 first detected in 1969) had an African origin and moved across the Indian Ocean to Australia on high-altitude winds. We provide strong supportive evidence for this hypothesis by combining genetic analyses and complex atmospheric dispersion modeling. Genetic analysis of 29 Australian and South African P. graminis f. sp. tritici races using microsatellite markers confirmed the close genetic relationship between the South African and Australian populations, thereby confirming previously described phenotypic similarities. Lagrangian particle dispersion model simulations using finely resolved meteorological data showed that long distance dispersal events between southern Africa and Australia are indeed possible, albeit rare. Simulated urediniospore transmission events were most frequent from central South Africa (viable spore transmission on approximately 7% of all simulated release days) compared with other potential source regions in southern Africa. The study acts as a warning of possible future P. graminis f. sp. tritici dispersal events from southern Africa to Australia, which could include members of the Ug99 race group, emphasizing the need for continued surveillance on both continents.

Phylogeography of western Mediterranean Cymbalaria (Plantaginaceae) reveals two independent long-distance dispersals and entails new taxonomic circumscriptions

The Balearic Islands, Corsica and Sardinia (BCS) constitute biodiversity hotspots in the western Mediterranean Basin. Oligocene connections and long distance dispersal events have been suggested to cause presence of BCS shared endemic species. One of them is Cymbalaria aequitriloba, which, together with three additional species, constitute a polyploid clade endemic to BCS. Combining amplified fragment length polymorphism (AFLP) fingerprinting, plastid DNA sequences and morphometrics, we inferred the phylogeography of the group and evaluated the species’ current taxonomic circumscriptions. Based on morphometric and AFLP data we propose a new circumscription for C. fragilis to additionally comprise a group of populations with intermediate morphological characters previously included in C. aequitriloba. Consequently, we suggest to change the IUCN category of C. fragilis from critically endangered (CR) to near threatened (NT). Both morphology and AFLP data support the current taxonomy of the single island endemics C. hepaticifolia and C. muelleri. The four species had a common origin in Corsica-Sardinia, and two long-distance dispersal events to the Balearic Islands were inferred. Finally, plastid DNA data suggest that interspecific gene flow took place where two species co-occur.

Historical translocations by M\u0101ori may explain the distribution and genetic structure of a threatened surf clam in Aotearoa (New Zealand)

The population genetic structure of toheroa (Paphies ventricosa), an Aotearoa (New Zealand) endemic surf clam, was assessed to determine levels of inter-population connectivity and test hypotheses regarding life history, habitat distribution and connectivity in coastal vs. estuarine taxa. Ninety-eight toheroa from populations across the length of New Zealand were sequenced for the mitochondrial cytochrome c oxidase I gene with analyses suggesting a population genetic structure unique among New Zealand marine invertebrates. Toheroa genetic diversity was high in Te Ika-a Māui (the North Island of New Zealand) but completely lacking in the south of Te Waipounamu (the South Island), an indication of recent isolation. Changes in habitat availability, long distance dispersal events or translocation of toheroa to southern New Zealand by Māori could explain the observed geographic distribution of toheroa and their genetic diversity. Given that early-Māori and their ancestors, were adept at food cultivation and relocation, the toheroa translocation hypothesis is plausible and may explain the disjointed modern distribution of this species. Translocation would also explain the limited success in restoring what may in some cases be ecologically isolated populations located outside their natural distributions and preferred niches.

Long distance dispersal in the assembly of floras: A review of progress and prospects in North America

AbstractHere, we review progress and prospects to explicitly test for long distance dispersal biogeographic events. Long distance dispersal represents a “jump” across some kind of barrier, such as a topographic feature or a zone of unsuitable climate and may include repeated jumps, or stepping‐stone dispersals. Long distance dispersals were considered integral for explaining the organization of biodiversity at large and small scales by early biogeographers, such as Darwin and Wallace. Darwin, Wallace, and others envisioned that long distance dispersals were predictable events because the vectors for dispersal, such as animals, winds, and currents, behaved in non‐random ways. However, these early biogeographers found that dispersal was hard to observe, and, later, with the advent of the theory of Continental Drift, vicariance became regarded as a better scientific explanation for the arrangement of biodiversity, because it represented a falsifiable hypothesis. Thus, long distance dispersal was reduced to a nuisance parameter in biogeography; a random possibility that could never fully be ruled out in a scenario in which evidence supported vicariance. Today, there is strong interest to more fully integrate long distance dispersal into understanding the assembly and organization of biodiversity on earth. In this review, we discuss progress and prospects for explicitly testing long distance dispersal hypotheses including through uses of molecular, morphological, paleontological, and informatics methods. We focus on hypothesis testing of long distance dispersals involved in the assembly of the flora of North America, which is a robust preliminary study system on account of its extant and extinct biodiversity being well‐catalogued.

Euphorbia Section Hainanensis (Euphorbiaceae), a New Section Endemic to the Hainan Island of China From Biogeographical, Karyological, and Phenotypical Evidence.

Euphorbia hainanensis is an endangered species endemic to the tropical Hainan Island in southern China and of historical importance for Chinese medicine. It is currently the only unplaced species of the genus Euphorbia (Euphorbiaceae) due to its isolated island distribution and debated placement by a previous molecular phylogenetic study. We sequenced nuclear ITS and chloroplast rbcL and ndhF for newly collected accessions of E. hainanensis and additional Euphorbia species found in Hainan, and analyzed the sequences in the context of the entire genus together with published data. All gene regions highly supported that E. hainanensis occupied an isolated phylogenetic position, showing no close affinity with any known Euphorbia sections suggesting it was a new section. ITS placed E. hainanensis sister to sect. Crossadenia (subgenus Chamaesyce) from Brazil with an estimated divergence time of 9.3-30.6 Mya while the chloroplast markers placed E. hainanensis at a position sister to the entire New World clade of Euphorbia subgenus Chamaesyce. In addition, our karyological results suggested a close affinity between E. hainanensis and the New World species of Euphorbia subg. Chamaesyce, with which shared the same chromosome number 2n = 28 and basic chromosome number x = 7. Phenotypically, E. hainanensis is unique with no close resemblance to other species in Euphorbia subg. Chamaesyce. Based on its isolated biogeographical, karyological, and phenotypical position, we propose a new section E. subgenus Chamaesyce section Hainanensis that might origin from long distance dispersal events because collective evidences showed a close affinity between the species from the Old World with those from the New World.

First insights on the biogeographical history of Phlegmariurus (Lycopodiaceae), with a focus on Madagascar

We explored the biogeographical history of a group of spore-bearing plants focusing on Phlegmariurus (Lycopodiaceae), a genus of lycophytes comprising ca. 250 species. Given its wide distribution in the Southern Hemisphere, Phlegmariurus provides a good model to address questions about the biogeographical processes underlying southern distributions, notably in Madagascar and surrounding islands, also called the Western Indian Ocean (WIO). Our aims were (i) to discuss the systematics of the Malagasy species in the light of molecular phylogenetic results, (ii) to provide the first dating analysis focused on Phlegmariurus and (iii) to understand the relative role of vicariance, dispersal and diversification in the origin of the Malagasy Phlegmariurus species.The phylogenetic relationships were inferred based on three plastid DNA regions (rbcL, trnH-psbA and trnL+trnL-trnF) and on a dataset comprising 93 species, including 16 Malagasy species (80% of the total Malagasy diversity for the genus). Our results highlighted the need to combine Malagasy Huperzia species in Phlegmariurus, as well as the polyphyly of widely distributed species: Phlegmariurus phlegmaria, P. squarrosus and P. verticillatus with the Malagasy species not belonging with the types of P. phlegmaria or P. squarrosus. This led us to propose new circumscriptions of Phlegmariurus species, especially in the WIO.Our dating analysis, relying on fossil calibrations, showed that Phlegmariurus would have originated in the Late Cretaceous and diversified in the Early Eocene. The biogeographical analysis highlighted uncertainties about the biogeographical origins of Phlegmariurus: the genus would have started to diversify in an ancestral range covering at least the Neotropics and Australasia. Hypotheses on the biogeographical history of Phlegmariurus were discussed, especially the roles of long distance dispersal, migration via Antarctica and via the Boreotropics. Six long distance dispersal events over the last 40 Ma would explain the Malagasy species diversity of Phlegmariurus, in combination with an important in situ diversification starting in the Miocene.

Myrteae phylogeny, calibration, biogeography and diversification patterns: Increased understanding in the most species rich tribe of Myrtaceae

Myrteae (c. 2500 species; 51 genera) is the largest tribe of Myrtaceae and an ecologically important groups of angiosperms in the Neotropics. Systematic relationships in Myrteae are complex, hindering conservation initiatives and jeopardizing evolutionary modelling. A well-supported and robust phylogenetic hypothesis was here targeted towards a comprehensive understanding of the relationships within the tribe. The resultant topology was used as a base for key evolutionary analyses such as age estimation, historical biogeography and diversification rate patterns. One nuclear (ITS) and seven chloroplast (psbA-trnH, matK, ndhF, trnl-trnF, trnQ-rps16, rpl16 and rpl32-trnL) DNA regions for 115 taxa representing 46 out of the 51 genera in the tribe were accessed and analysed using maximum likelihood and Bayesian inference tools for phylogenetic reconstruction. Dates of diversification events were estimated and contrasted using two distinct fossil sets (macro and pollen) in BEAST. The subsequent dated phylogenies were compared and analysed for biogeographical patterns using BioGeoBEARS and diversification rates using BAMM. Myrteae phylogeny presents strong statistical support for three major clades within the tribe: Australasian group, Myrtus group and Main Neotropical Lineage. Dating results from calibration using macrofossil are an average of 20 million years older and show an early Paleocene origin of Myrteae, against a mid-Eocene one from the pollen fossil calibration. Biogeographic analysis shows the origin of Myrteae in Zealandia in both calibration approaches, followed by a widespread distribution throughout the still-linked Gondwana continents and diversification of Neotropical endemic lineages by later vicariance. Best configuration shift indicates three points of acceleration in diversification rates, all of them occurring in the Main Neotropical Lineage. Based on the reconstructed topology, several new taxonomic placements were recovered, including: the relative position of Myrtus communis, the placement of the Blepharocalyx group, the absence of generic endemism in the Caribbean, and the paraphyletism of the former Pimenta group. Distinct calibration approaches affect biogeography interpretation, increasing the number of necessary long distance dispersal events in the topology with older nodes. It is hypothesised that biological intrinsic factors such as modifications of embryo type and polyploidy might have played a role in accelerating shifts of diversification rates in Neotropical lineages. Future perspectives include formal subtribal classification, standardization of fossil calibration approaches and better links between diversification shifts and trait evolution.

East-west divergence in central Brazilian Cerrado revealed by cpDNA sequences of a bird-dispersed tree species

Population genetic studies of plant species can contribute to understanding the evolutionary history of the Brazilian Cerrado, a highly threatened hotspot and the richest tropical savanna in the world. Therefore, this study aimed at investigating the diversity and genetic structure of Byrsonima coccolobifolia (Malpighiaceae), one of the most common tree species in the Brazilian Cerrado, focusing mainly on the central area of the biome. This is a bird-dispersed species, and studies targeting species with this seed dispersal syndrome are scarce. First, we performed a careful screening of cpDNA markers to identify regions suitable for intraspecific genetic studies, and then we investigated the diversity and genetic structure in ten populations of B. coccolobifolia. The cpDNA regions selected (trnS-trnG and trnH-trnK) revealed considerable divergence among populations and a striking geographical structure, separating populations in two groups, east and west. Although seed dispersal by birds is expected to reach long distances, our results strongly corroborate studies targeting trees with limited seed dispersal. This suggests that historical fragmentation of Cerrado (possibly during cold and dry periods of the Quaternary) might have limited long distance dispersal events after climate amelioration even in bird-dispersed species, especially while Cerrado was expanding but still fragmented.

Extended dispersal kernels in a changing world: insights from statistics of extremes

Summary Dispersal ecology is a topical discipline that involves understanding and predicting plant community responses to multiple drivers of global change. Propagule movements that entail long‐distance dispersal (LDD) events are crucial for plants to reach and colonize suitable sites across fragmented landscapes. Yet, LDD events are extremely rare, and thus, obtaining reliable estimates of the maximum distances that propagules move across and of their frequency has been a long‐lasting challenge in plant ecology. Recent advances in dispersal ecology have provided reliable records of dispersal distances, but they remain confined to focal populations, limiting our ability to infer the frequency and actual extent of LDD events across landscapes. In this study, we view LDD events as extreme values of a dispersal function, and we apply statistics of extremes to derive the frequency and extent of LDD events of simulated and empirical data sets. We first briefly explain the rationale behind statistics of extremes, and we then illustrate how dispersal ecology can benefit conceptually and analytically from applying extreme value analyses. We apply the block maxima approach to simulated seed shadows, and we apply the peak over a threshold method to empirical data sets that contain pollen and seed dispersal distances recorded for a population of Prunus mahaleb, an insect‐pollinated and vertebrate‐dispersed tree species. Diagnostic plots reveal a distance threshold of υ = 80 m for pollen grains and of υ = 170 m for dispersed seeds. Values that exceed the threshold fit a light‐tailed distribution function for pollen and fit a fat‐tailed Pareto distribution for seed dispersal distances. Both distribution functions estimate a low (but nonzero) conditional probability of reaching distant locations, extending well beyond the borders of our focal population as follows: Pr (X ≥ 1 km) = 9 × 10−5 for pollen grains and Pr (X ≥ 10 km) = 7 × 10−5 for dispersed seeds. Synthesis. Dispersal ecologists can take the most of their dispersal distance records by applying statistics of extremes to infer the probability of occurrence of extremely rare, but crucial, long distance dispersal events that reach locations well beyond focal populations.

Phylogeographic analyses reveal Transpontic long distance dispersal in land snails belonging to the Caucasotachea atrolabiata complex (Gastropoda: Helicidae)

The phylogeography and population structure of land snails belonging to the Caucasotachea atrolabiata complex in the Caucasus region was investigated to obtain a better understanding of diversification processes in this biodiversity hotspot. So far the complex has been classified into three species, C. atrolabiata from the north-western Caucasus, C. calligera from Transcaucasia and C. intercedens from the eastern Pontus Mountains. Phylogenetic (neighbor-net and neighbor-joining tree) as well as admixture analyses based on AFLP data showed that the complex consists of two population clusters corresponding to C. atrolabiata and C. calligera. The populations assigned to C. intercedens in fact represent hybrids consisting of different proportions of the genomes of C. atrolabiata and C. calligera. There is a broad transition zone between C. atrolabiata and C. calligera in the Pontic Mountains and a second transition zone in Abkhazia. Because of evidence for gene flow, it is suggested to classify the two aforementioned taxa as subspecies, namely C. a. atrolabiata and C. a. calligera. The presence of mitochondrial C. a. atrolabiata haplotypes in Turkey can only be explained by passive dispersal across the Black Sea. The distribution of C. a. atrolabiata and additional cases of land snails with disjunct Transpontic distribution patterns cannot be ascribed to a common cause but are results of long distance dispersal events at different times.