Higher Diversification Rates Research Articles

Risk factors for colostomy in military colorectal trauma: A review of 867 patients

Limited data exist examining the use of fecal diversion in combatants from modern armed conflicts. Characterization of factors leading to colostomy creation is an initial step toward optimizing and individualizing combat casualty care. A retrospective review of the US Department of Defense Trauma Registry database was performed for all US and coalition troops with colorectal injuries sustained during combat operations in Iraq and Afghanistan over 8 years. Colostomy rate, anatomic injury location, mechanism of injury, demographic data, and initial physiologic parameters were examined. Univariate and multivariate analyses were conducted. We identified 867 coalition military personnel with colorectal injuries. The overall colostomy rate was 37%. Rectal injuries had the highest diversion rate (56%), followed by left-sided (41%) and right-sided (20%) locations (P < .0001). Those with gunshot wounds (GSW) underwent diversion more often than blast injuries (43% vs 31% respectively, P < .0008). Injury Severity Score ≥16 (41% vs 30%; P = .0018) and damage control surgery (DCS; 48.2% vs 31.4%; P < .0001) were associated with higher diversion rates. On multivariate analysis, significant predictors for colostomy creation were injury location: Rectal versus left colon (odds ratio [OR], 2.2), rectal versus right colon (OR, 7.5), left versus right colon (OR, 3.4), GSW (OR, 2.0), ISS ≥ 16 (OR, 1.7), and DCS (OR, 1.6). In this exploratory study of 320 combat-related colostomies, distal colon and rectal injuries continue to be diverted at higher rates independent of other comorbidities. Additional outcomes-directed research is needed to determine whether such operative management is beneficial in all patients.

Characteristics of Hospitals Diverting Ambulances in a California EMS System

While several reports discuss controversies regarding ambulance diversion from acute care hospitals and the mortality, financial, and resource effects, there is scant literature related to the effect of hospital characteristics. The objective of this study was to describe specific paramedic receiving center characteristics that are associated with ambulance diversion rates in an Emergency Medical Services system. A retrospective observational study design was used. The study was performed in a suburban EMS system with 27 paramedic receiving centers studied; one additional hospital present at the beginning of the study period (2000-2008) was excluded due to lack of recent data. Hospital-level and population-level characteristics were gathered, including diversion rate (hours on diversion/total hours open), for-profit status, number of specialty services (including trauma, burn, cardiovascular surgery, renal transplant services, cardiac catheterization capability [both interventional and diagnostic], and burn surgery), average inpatient bed occupancy rate (total patient days/licensed bed days), annual emergency department (ED) volume (patients per year), ED admission rate (percent of ED patients admitted), and percent of patients leaving without being seen. Demographic characteristics included percent of persons in each hospital's immediate census tract below the 100% and 200% poverty lines (each considered separately), and population density within the census tract. Bivariate and regression analyses were performed. Diversion rates for the 27 centers ranged from 0.3%-14.5% (median 4.5%). Average inpatient bed occupancy rate and presence of specialty services were correlated with an increase in diversion rate; occupancy rate showed a 0.08% increase in diversion hours per 1% increase in occupancy rate (95% CI, 0.01%-0.16%), and hospitals with specialty services had, on average, a 4.1% higher diversion rate than other hospitals (95% CI, 1.6%-6.7%). Other characteristics did not show a statistically significant effect. When a regression was performed, only the presence of specialty services was related to the ambulance diversion rate. Hospitals in this study providing specialty services were more likely to have higher diversion rates. This may result in increased difficulty getting patients requiring specialty care to centers able to provide the needed level of service. Major limitations include the retrospective nature of the study, as well as reliance on multiple data systems.

The explosive radiation of Cheirolophus (Asteraceae, Cardueae) in Macaronesia.

BackgroundConsidered a biodiversity hotspot, the Canary Islands have been the key subjects of numerous evolutionary studies concerning a large variety of organisms. The genus Cheirolophus (Asteraceae) represents one of the largest plant radiations in the Canarian archipelago. In contrast, only a few species occur in the Mediterranean region, the putative ancestral area of the genus. Here, our main aim was to reconstruct the phylogenetic and biogeographic history of Cheirolophus with special focus on explaining the origin of the large Canarian radiation.ResultsWe found significant incongruence in phylogenetic relationships between nuclear and plastid markers. Each dataset provided resolution at different levels in Cheirolophus: the nuclear markers resolved the backbone of the phylogeny while the plastid data provided better resolution within the Canarian clade. The origin of Cheirolophus was dated in the Mid-Late Miocene, followed by rapid diversification into the three main Mediterranean lineages and the Macaronesian clade. A decrease in diversification rates was inferred at the end of the Miocene, with a new increase in the Late Pliocene concurrent with the onset of the Mediterranean climate. Diversification within the Macaronesian clade started in the Early-Mid Pleistocene, with unusually high speciation rates giving rise to the extant insular diversity.ConclusionsClimate-driven diversification likely explains the early evolutionary history of Cheirolophus in the Mediterranean region. It appears that the exceptionally high diversification rate in the Canarian clade was mainly driven by allopatric speciation (including intra- and interisland diversification). Several intrinsic (e.g. breeding system, polyploid origin, seed dispersal syndrome) and extrinsic (e.g. fragmented landscape, isolated habitats, climatic and geological changes) factors probably contributed to the progressive differentiation of populations resulting in numerous microendemisms. Finally, hybridization events and emerging ecological adaptation may have also reinforced the diversification process.

Trait-driven vs. syndrome-driven diversification in the Mediterranean woody flora

In the woody flora from the Mediterranean basin there are two character syndromes which differ in diversification rate : the sclerophyll and the nonsclerophyll syndrome ; the latter has the highest diversification rate mainly due to rampant speciation. The cause of this increased diversification rate in nonsclerophylls could be the overall and complex interaction between their syndrome traits (conspicuous flowers, dry fruits, small seeds, non-animal dispersal, fireinduced germination) and environmental pressures (pollinator competition, summer drought, poor soils, frequent fires). Alternatively, one or very few of the syndrome traits could be responsible of most of the difference in diversification rate (trait-driven diversification). This work examines the relative role of syndrome traits on nonsclerophyll diversification using ANCOVA analyses for the flora of Western Andalusia (Spain). The results point that the increased diversification rate typical of the nonsclerophyll syndrome is largely caused by one single trait : the obligate seeder strategy (that is, fireinduced germination in fire-killed shrubs). This is the only trait whose consideration erases the difference in diversification rate between both syndromes. This result cannot be explained as the effect of altitudinal range as a potentially confounding variable. Furthermore, obligate seeder genera show a much higher diversification rate than the other genera and account for most of the species richness here considered. Thus the origin of this Mediterranean flora can be better understood as the outcome of traitdriven (seeder strategy) instead of syndromedriven diversification. The role of fire in the evolution of this regional flora stands out over the other possible factors here considered.

Proto-South-East Asia as a trigger of early angiosperm diversification

Darwin described as an ‘abominable mystery’ the abrupt origin of angiosperms in the mid-Cretaceous and the high diversification rates in their early history. The father of evolutionary theory could not fathom this rapid diversification and rather invoked that ‘there was during long ages a small isolated continent in the S. hemisphere, which served as the birthplace of the higher plants’. In this essay, we comment on the spatial origin of angiosperms, but focus primarily on understanding the abiotic factors that promoted the early diversification of angiosperms by reviewing palaeobotanical, palaeogeographical, phylogenetics and biogeographical evidence. We argue that islands located in the region today occupied by South-East Asia played a major role in angiosperm diversification during the Late Jurassic and Early Cretaceous. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 326–333.

Shifts in Climate Foster Exceptional Opportunities for Species Radiation: The Case of South African Geraniums

Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot.

Cambrian algoflora: Association of various microorganism groups

The Vendian-Cambrian algoflora provided food resources for the first shell organisms, which showed high rate of diversification throughout the world. Against the background of bacterial and cyanobacterial associations, which crossed the Precambrian boundary, certain members of the divisions Rhodophyta and Chlorophyta are determined with confidence among algae, while the taxonomic position of the majority of the algoflora remains uncertain. The study traditionally involves forms with different preservation types, including calciferous algae, organic-walled macroalgae, and acritarchs.

Mitochondrial phylogeny reveals cryptic genetic diversity in the genus Niviventer (Rodentia, Muroidea)

Niviventer is a muroid genus with 17 species widely distributed in East and Southeast Asia. These animals are important components of both extant and fossil small mammal communities, and they are among the most common infectious agents in humans. In this study, we employed partitioned Bayesian and relaxed clock divergence dating analyses and included the Niviventer mitochondrial cytochrome b genes of from GenBank (n = 223). Although the intra-generic relationships were not fully resolved, we recognized four major clades/subclades that could support further division of the genus. Paraphyletic and polyphyletic species were discovered, and 21 putative species were recognized through species delimitation analysis, which indicated an imperfect taxonomy and the existent of cryptic species. Molecular dating supported Niviventer origination in the late Miocene, and relatively higher diversification rates were observed in the late Pliocene and the Pleistocene, which might correlate with climate fluctuations.

Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes

Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all living vertebrates. Despite their dominant role in aquatic ecosystems, the evolutionary history and tempo of acanthomorph diversification is poorly understood. We investigate the pattern of lineage diversification in acanthomorphs by using a well-resolved time-calibrated phylogeny inferred from a nuclear gene supermatrix that includes 520 acanthomorph species and 37 fossil age constraints. This phylogeny provides resolution for what has been classically referred to as the "bush at the top" of the teleost tree, and indicates acanthomorphs originated in the Early Cretaceous. Paleontological evidence suggests acanthomorphs exhibit a pulse of morphological diversification following the end Cretaceous mass extinction; however, the role of this event on the accumulation of living acanthomorph diversity remains unclear. Lineage diversification rates through time exhibit no shifts associated with the end Cretaceous mass extinction, but there is a global decrease in lineage diversification rates 50 Ma that occurs during a period when morphological disparity among fossil acanthomorphs increases sharply. Analysis of clade-specific shifts in diversification rates reveal that the hyperdiversity of living acanthomorphs is highlighted by several rapidly radiating lineages including tunas, gobies, blennies, snailfishes, and Afro-American cichlids. These lineages with high diversification rates are not associated with a single habitat type, such as coral reefs, indicating there is no single explanation for the success of acanthomorphs, as exceptional bouts of diversification have occurred across a wide array of marine and freshwater habitats.

A phylogenetic subclade analysis of range sizes of endemic woody seed plant species of China: Trait conservatism, diversification rates and evolutionary models

AbstractAdaptive radiation predicted that diversification rate of species and/or the divergence of trait evolution are declined from ancient to contemporary time due to reduced novel niches, namely the “early burst” model. It is still controversial whether the early burst model is ubiquitous over various taxa for species diversification and/or phenotypic evolution. The applicability of the model on plants has little been tested yet in current literature. To address this question, in the present study, a subclade‐level phylogenetic comparative analysis of range size evolution and diversification rates of 6885 endemic woody seed plant species in China (i.e., species only found in China) was performed. My study showed that phylogenetic signals of range sizes depend on the phylogenetic scope and the sampling of subclades. Early burst model was not supported for the range size evolution for endemic woody plants of China, while the simple Brownian motion model of adaptive radiation had the best fit. Diversification of species over the subclades of the phylogeny showed that young clades have higher diversification rates than old clades, being contradictory to the “early burst” prediction of adaptive radiation. However, a whole‐phylogeny diversification analysis suggests that the BOTHVAR model where speciation rate is decreasing while extinction rate is increasing is the best one to describe the time‐dependent trend of diversification of endemic woody plants of China. Moreover, the evolution of range sizes of woody plants is found to be largely independent to diversification rates of species, deprecating the positive range sizes‐diversification hypothesis. At last, a strong positive relationship between phylogenetic mean and variance of range sizes was observed. In conclusion, the “early burst” model predicted by adaptive radiation might be applied to the diversification rates, but not the range size evolution of endemic woody plants of China. Further studies are required by sampling more taxa and building a high‐quality phylogeny to test and verify the patterns found in the present study.

Contrasting evolutionary hypotheses between two mediterranean‐climate floristic hotspots: the Cape of southern Africa and the Mediterranean Basin

AbstractAimThe Cape of southern Africa and the Mediterranean Basin, two of the world's five mediterranean‐climate biodiversity hotspots, are exceptionally species‐rich and constitute a well‐described example of ecological convergence. However, the area‐adjusted plant species diversity of the Cape is on average more than double that of the Mediterranean Basin. Here, we investigate the causes of this diversity asymmetry by drawing on phylogenetic information from a variety of plant groups and focusing on three competing hypotheses: diversity disparities arising from differential clade ages, diversification rates or diversity limits.LocationCape of southern Africa and the Mediterranean Basin.MethodsWe reviewed a variety of studies in order to contrast the geography, geomorphic history, biogeographical connectivity and ecological context in the two hotspots. We also tested the relationship between clade age and species richness in both regions based on phylogenetic information from 39 clades.ResultsClades are on average older in the Cape than in the Mediterranean Basin. Clade age is a strong predictor of species diversity in the Cape, suggesting that diversity‐dependent regulatory mechanisms may be weak. In contrast, we failed to find a relationship between age and diversity in the Mediterranean Basin, indicating that a diversity limit may have been achieved in multiple clades.Main conclusionsThe Cape has a higher species density than the Mediterranean Basin owing to a combination of older clade ages, high rates of diversification in certain lineages and an exceptionally high upper limit to diversity. High richness in the Cape is linked to long‐term lineage persistence in a heterogeneous but stable evolutionary context. In contrast, the climatically unstable Mediterranean Basin has offered fewer opportunities for diversity accumulation in the long term (owing to high extinction rates), but appears to be a hotspot of recent rapid speciation.

Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient

Latitudinal diversity gradients are underlain by complex combinations of origination, extinction, and shifts in geographic distribution and therefore are best analyzed by integrating paleontological and neontological data. The fossil record of marine bivalves shows, in three successive late Cenozoic time slices, that most clades (operationally here, genera) tend to originate in the tropics and then expand out of the tropics (OTT) to higher latitudes while retaining their tropical presence. This OTT pattern is robust both to assumptions on the preservation potential of taxa and to taxonomic revisions of extant and fossil species. Range expansion of clades may occur via "bridge species," which violate climate-niche conservatism to bridge the tropical-temperate boundary in most OTT genera. Substantial time lags (∼5 Myr) between the origins of tropical clades and their entry into the temperate zone suggest that OTT events are rare on a per-clade basis. Clades with higher diversification rates within the tropics are the most likely to expand OTT and the most likely to produce multiple bridge species, suggesting that high speciation rates promote the OTT dynamic. Although expansion of thermal tolerances is key to the OTT dynamic, most latitudinally widespread species instead achieve their broad ranges by tracking widespread, spatially-uniform temperatures within the tropics (yielding, via the nonlinear relation between temperature and latitude, a pattern opposite to Rapoport's rule). This decoupling of range size and temperature tolerance may also explain the differing roles of species and clade ranges in buffering species from background and mass extinctions.

Variables influencing germination and initial survival of two critically endangered plants: Warea amplexifolia and Lupinus aridorum

One challenge of ex situ conservation is developing propagation methods that promote a high rate of survival and genetic diversity. Developing successful propagation methods is especially important for rare species to prevent their extinction. Clasping warea, Warea amplexifolia (Nutt.) Nutt. (Brassicaceae), and scrub lupine, Lupinus aridorum McFarlin ex Beckner (Fabaceae), are two rare species endemic to imperiled Florida sandhill and scrub habitats, respectively. We tested whether the collection site of seeds, seed stratification temperature, and several propagation methods influenced germination and initial survival of W. amplexifolia and L. aridorum. The collection site of seeds and type of pot influenced percent germination of W. amplexifolia, whereas soaking seeds in water and stratification temperature did not. The site where seeds were collected did not influence germination of L. aridorum and treating seedlings with salicylic acid, nitrogen, or salicylic acid and nitrogen sometimes reduced, but did not increase, initial survival of seedlings. Overall, our results will inform additional experiments on ex situ conservation and may be applicable to other herbs endemic to Florida.

Revenant clades in historical biogeography: the geology of New Zealand predisposes endemic clades to root age shifts

AbstractAimOur aim was to elucidate the effect of mass extinctions on inferred crown ages of terrestrial clades endemic to ancient islands. We thereby assessed the potential for mass extinction events, such as the Zealandian marine incursion episode in the Oligocene, to skew the interpretation of the evolutionary history of clades of various sizes.LocationSimulation study focusing on New Zealand.MethodsClades of various sizes were simulated under a birth–death model with variable parameters for diversification, invoking a prolonged extinction event, using the R packageTreeSim. We measured the scaled root shiftJbetween actual (i.e. first cladogenetic event) and inferred (i.e. most recent common ancestor of extant taxa) clade divergence times in simulated phylogenies incurred by extinction processes.ResultsA pulse of extinction followed by a prolonged period of low cladogenetic potential – modelled after the geological history of Zealandia in the Oligocene – produced large root shifts in clades of all sizes. Small clades with high net diversification rates were especially prone to belying pre‐Oligocene history. In simulations invoking mass extinctions wherein a pre‐extinction root was retained, phylogenies of extant taxa were characterized by anti‐sigmoidal log lineage‐through‐time plots that mimicked an upturn in diversification rate after the extinction period.Main conclusionsNon‐selective mass extinctions can engender large discrepancies in actual and inferred root ages, particularly in small, old clades. The evolutionary histories of lineages that survive mass extinctions are difficult to distinguish from scenarios of rapid radiation. This outcome challenges previous interpretations of post‐Oligocene crown ages for clades endemic to New Zealand as sufficient evidence for rejecting a pre‐Oligocene evolutionary history. As a corollary, our results suggest that the extant size of a particular clade is the foremost indicator of its potential for historical biogeographical inference. We therefore review the hypothesis of the total submersion of Zealandia, highlighting empirical cases of lineages with demonstrable pre‐Oligocene history that refute the hypothesis of total submersion.

WHAT CAN MULTIPLE PHYLOGENIES SAY ABOUT THE LATITUDINAL DIVERSITY GRADIENT? A NEW LOOK AT THE TROPICAL CONSERVATISM, OUT OF THE TROPICS, AND DIVERSIFICATION RATE HYPOTHESES

We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16-22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no difference in diversification between tropical and temperate sister lineages; thus, diversity of tropical clades was not explained by higher diversification rates in this zone. Moreover, lineages with latitudinal stasis diversified more compared to sister lineages entering a new latitudinal zone. This preserved preexisting diversity differences between latitudinal zones and can be considered a new mechanism for why diversity tends to peak in the zone of origin.

Spatio‐temporal evolution of Fosterella (Bromeliaceae) in the Central Andean biodiversity hotspot

AbstractAimTo reconstruct the spatio‐temporal evolution of Fosterella (Bromeliaceae), a genus characterized by a high degree of endemism in the Central Andes, and to account for contemporary patterns of diversity and distribution within the genus.LocationFosterella has its centre of diversity in the Central Andes (24 species), where it occurs in two major biomes: the Yungas and seasonally dry tropical forests (SDTF). The genus displays three major disjunctions: Amazonia (one species), Central America (one species), and the Brazilian Shield (five species).MethodsPhylogenetic relationships within Fosterella were inferred based on six plastid DNA regions. Parsimony and likelihood methods, a Bayesian relaxed molecular clock, ancestral area reconstructions, and diversification rate analyses were used to infer the spatio‐temporal evolution of Fosterella.ResultsThe origin of extant lineages of Fosterella was placed in the late Miocene (c. 9.6 Ma) during the last rapid Andean uplift. SDTF and azonal lowland sites were inferred as the most likely ancestral habitats. The Yungas were colonized several times independently from c. 4.7 Ma onwards. Only one clade diversified in the Yungas, indicative of an ecological shift to moister and cooler conditions. Two recent long‐distance dispersals to Central America and to Amazonia were inferred. Diversification rates within Fosterella were found to be constant through time and comparatively low (0.4 species Myr−1).Main conclusionsAllopatric speciation is the main mode of diversification in Fosterella. The isolated distribution of suitable habitats fostered the evolution of a high degree of endemism. The low speciation rates in Fosterella contrast with high diversification rates of Andean high‐elevation taxa but are similar to other Andean low‐ to mid‐elevation taxa. The last rapid Andean uplift did not leave a detectable signature in the diversification rates of Fosterella.

The global diversity of birds in space and time

Current global patterns of biodiversity result from processes that operate over both space and time and thus require an integrated macroecological and macroevolutionary perspective. Molecular time trees have advanced our understanding of the tempo and mode of diversification and have identified remarkable adaptive radiations across the tree of life. However, incomplete joint phylogenetic and geographic sampling has limited broad-scale inference. Thus, the relative prevalence of rapid radiations and the importance of their geographic settings in shaping global biodiversity patterns remain unclear. Here we present, analyse and map the first complete dated phylogeny of all 9,993 extant species of birds, a widely studied group showing many unique adaptations. We find that birds have undergone a strong increase in diversification rate from about 50 million years ago to the near present. This acceleration is due to a number of significant rate increases, both within songbirds and within other young and mostly temperate radiations including the waterfowl, gulls and woodpeckers. Importantly, species characterized with very high past diversification rates are interspersed throughout the avian tree and across geographic space. Geographically, the major differences in diversification rates are hemispheric rather than latitudinal, with bird assemblages in Asia, North America and southern South America containing a disproportionate number of species from recent rapid radiations. The contribution of rapidly radiating lineages to both temporal diversification dynamics and spatial distributions of species diversity illustrates the benefits of an inclusive geographical and taxonomical perspective. Overall, whereas constituent clades may exhibit slowdowns, the adaptive zone into which modern birds have diversified since the Cretaceous may still offer opportunities for diversification.

Origin and evolution of Chrysobalanaceae: insights into the evolution of plants in the Neotropics

Some plant families show a striking imbalance in species diversity between the Neotropics and the Palaeotropics. The woody plant family Chrysobalanaceae is a typical example of this pattern, with 80% of the 531 species in the Neotropics. In order to test alternative interpretations for this pattern, we generated a dated phylogenetic hypothesis for Chrysobalanaceae, using DNA sequence data from one nuclear and six plastid markers. Using a maximum likelihood approach, we jointly inferred ancestral areas and diversification rates in the Neotropics and Palaeotropics. We found that Chrysobalanaceae most probably originated in the Palaeotropics about 80 Mya. The family dispersed into the Neotropics at least four times beginning 40–60 Mya, with at least one back-dispersal to the Palaeotropics. Members of Chrysobalanaceae have experienced higher extinction, speciation and net diversification rates in the Neotropics. Hence, the high species diversity of Chrysobalanaceae in the Neotropics appears to be primarily caused by a higher speciation rate in this region. Several recent studies have shown high diversification rates in Neotropical plant families, but have focused on Andean-centred taxa. Ours is the first study to find a similar pattern in a family for which the centre of diversity is in eastern and central Amazonia.

RECURRENT EVOLUTION OF DIOECY IN BRYOPHYTES

The origin and maintenance of separate sexes (dioecy) is an enduring evolutionary puzzle. Although both hermaphroditism and dioecy occur in many diverse clades, we know little about the long-term evolutionary consequences of changing sexual system. Here we find evidence for at least 133 transitions between sexual systems in mosses, representing an almost unparalleled lability in the evolution of their sexual systems. Furthermore, in contrast to predictions, the transition rate from hermaphroditism to dioecy was approximately twice as high as the reverse transition. Our results also suggest that hermaphrodites may have higher rates of diversification than dioecious mosses. These results illustrate the utility of mosses for understanding the genomic and macroevolutionary consequences of hermaphroditism and dioecy.

Global biogeography and diversification of palms sheds light on the evolution of tropical lineages. II. Diversification history and origin of regional assemblages

AbstractAimPalms (Arecaceae/Palmae) are a model group for evolutionary studies in the tropics. In two companion papers, we aim to establish a general framework of palm evolution, exploring the geographical distribution of palm lineages and species diversity patterns at global and regional levels. In this, the second paper, we analyse the biogeographical events underlying regional palm assemblages and diversification processes across the family. We investigate the timing and location of diversification rate shifts and test the ‘odd man out’ pattern of low species diversity observed in the African palm flora.LocationGlobal.MethodsA complete, dated phylogeny of palm genera and ancestral area reconstructions were used to infer the biogeographical history of regional palm assemblages. Diversification rates for all genera were estimated and significant shifts in diversification rates across the family were identified under a maximum likelihood model.ResultsFollowing their early diversification in Laurasia around 100 Ma, palms dispersed southwards before the end of the Cretaceous. Few dispersal events into Africa, North America and South America were inferred, whereas numerous lineages migrated between Eurasia, the Pacific and the Indian Ocean. Thirteen diversification rate increases were identified. High diversification rates were found only in lineages from Asia, the Americas, the Pacific and the Indian Ocean, but not in any African groups. Diversification decreases were not identified in any lineage.Main conclusionsDispersal of palms into their present‐day distribution started during the Late Cretaceous, consistent with the first fossil records for rain forests in Africa and South America. The few dispersal events into South America and Africa emphasize the isolated position of these continents for most of the Cenozoic. In contrast, high dispersal between Eurasia, the Pacific and the Indian Ocean, notably during the Miocene, can be attributed to geological activity in the region, especially in Malesia. Low species diversity in Africa relative to other regions is explained here by increased in situ diversification in Asia, the Americas, the Pacific and the Indian Ocean, rather than by diversification rate decreases in Africa. This may prove to be a general pattern in other organisms showing a similar disparity in richness in Africa.