AN S.E.M. SURVEY OF THE FIVE CARNIVOROUS PITCHER PLANT GENERA

Scanning electron microscopy was used to observe features of representative species of the five carnivorous pitcher plant genera which allow them to lure, capture, and digest insects. Nepenthes rafflesiana, Sarracenia purpurea, Darlingtonia californica, Heliamphora heterodoxa, and Cephalotus follicularis were studied. The many morphological similarities observed in the phylogenetically unrelated plants show evidence supporting the concept of their convergent evolution. Several previously undescribed features of some plants were resolved which help elucidate their insect trapping mechanisms.     

Phylogenetic assessment and biogeographic analyses of tribe <Emphasis Type="Italic">Peracarpeae</Emphasis> (Campanulaceae)

Peracarpeae is a small tribe consisting of three genera: Homocodon, Heterocodon and Peracarpa, with a disjunct distribution between eastern Asia and western North America. Homocodon is endemic to southwestern China and was previously placed in the western North American genus Heterocodon. Our phylogenetic analysis using four plastid markers (matK, atpB, rbcL and trnL-F) suggests the polyphyly of Peracarpeae. Homocodon is sister to a clade consisting of the eastern Asian Adenophora, Hanabusaya and species of Campanula from the Mediterranean region and North America, rather than forming a clade with Heterocodon. Homocodon and its Eurasia relatives are estimated to have diverged in the early Miocene (16.84 mya, 95% HPD 13.35–21.45 mya). The eastern Asian Peracarpa constitutes a clade with the North American Heterocodon, Githopsis and three species of Campanula, supporting a disjunction between eastern Asia and North America in Campanulaceae. The Asian-North American disjunct lineages diverged in the early Miocene (16.17 mya, 95% HPD 13.12–20.9 mya). The biogeographic analyses suggest that Homocodon may be a relict of an early radiation in eastern Asia, and that Peracarpa and its closest North American relatives most likely originated from a Eurasian ancestor.     

Phylogenetic relationships and evolution in Chrysosplenium (Saxifragaceae) based on matK sequence data

Chrysosplenium (Saxifragaceae) consists of 57 species widely distributed in temperate and arctic regions of the Northern Hemisphere, with two species restricted to the southern part of South America. Species relationships within the genus are highly problematic. The genus has traditionally been divided into two groups, sometimes recognized as sections (Oppositifolia and Alternifolia), based on leaf arrangement, or, alternatively, into 17 series. Based on morphological features, Hara suggested that the genus originated in South America and then subsequently migrated to the Northern Hemisphere. We conducted phylogenetic analyses of DNA sequences of the chloroplast gene matK for species of Chrysosplenium to elucidate relationships, test Hara's biogeographic hypothesis for the genus, and examine chromosomal and gynoecial diversification. These analyses revealed that both sections Oppositifolia and Alternifolia are monophyletic and form two large sister clades. Hence, leaf arrangement is a good indicator of relationships within this genus. Hara's series Pilosa and Macrostemon are each also monophyletic; however, series Oppositifolia, Alternifolia, and Nepalensia are clearly not monophyletic. MacClade reconstructions suggest that the genus arose in Eastern Asia, rather than in South America, with several independent migration events from Asia to the New World. In one well-defined subclade, species from eastern and western North America form a discrete clade, with Old World species as their sister group, suggesting that the eastern and western North American taxa diverged following migration to that continent. The South American species forms a clade with species from eastern Asia; this disjunction may be the result of ancient long-distance dispersal. Character mapping demonstrated that gynoecial diversification is dynamic, with reversals from inferior to half-inferior ovaries, as well as to ovaries that appear superior. Chromosomal evolution also appears to be labile with several independent origins of n = 12 (from an original number of n = 11) and multiple episodes of aneuploidy.     

Diversification of the American bulb-bearing Oxalis (Oxalidaceae): Dispersal to North America and modification of the tristylous breeding system

? Premise of the study: The American bulb-bearing Oxalis (Oxalidaceae) have diverse heterostylous breeding systems and are distributed in mountainous areas from Patagonia to the northeastern United States. To study the evolutionary processes leading to this diversity, we constructed the first molecular phylogeny for the American bulb-bearing Oxalis and used it to infer biogeographic history and breeding system evolution. ? Methods: We used DNA sequence data (nuclear ribosomal internal transcribed spacer, trnL-trnL-trnF, trnT-trnL, and psbJ-petA) to infer phylogenetic history via parsimony, likelihood, and Bayesian analyses. We used Bayes Multistate to infer ancestral geographic distributions at well-supported nodes of the phylogeny. The Shimodaira-Hasegawa (SH) test distinguished among hypotheses of single or multiple transitions from South America to North America, and tristyly to distyly. ? Key results: The American bulb-bearing Oxalis include sampled members of sections Ionoxalis and Pseudobulbosae and are derived from a larger clade that includes members of sections Palmatifoliae, Articulatae, and the African species. The American bulb-bearing Oxalis comprise two clades: one distributed in SE South America and the other in the Andes and North America. An SH test supports multiple dispersals to North America. Most sampled distylous species form a single clade, but at least two other independent distylous lineages are supported by the topologies and SH tests. ? Conclusions: Phylogenetic results suggest the American bulb-bearing Oxalis originated in southern South America, dispersed repeatedly to North America, and had multiple transitions from tristyly to distyly. This study adds to our understanding of biogeographic history and breeding system evolution and provides a foundation for more precise inferences about the study group.     

Molecular phylogenetics and biogeography of the eastern Asian–eastern North American disjunct Mitchella and its close relative Damnacanthus (Rubiaceae,Mitchelleae)

Mitchella is a small genus of the Rubiaceae with only two species. It is the only herbaceous semishrub of the family showing a disjunct distribution in eastern Asia and eastern North America, extending to Central America. Its phylogeny and biogeographical diversification remain poorly understood. In this study, we conducted phylogenetic and biogeographical analyses for Mitchella and its close relative Damnacanthus based on sequences of the nuclear internal transcribed spacer (ITS) and four plastid markers (rbcL, atpB‐rbcL, rps16 and trnL‐F). Mitchella is monophyletic, consisting of an eastern Asian M. undulata clade and a New World M. repens clade. Our results also support Michella as the closest relative to the eastern Asian Damnacanthus. The divergence time between the two intercontinental disjunct Mitchella species was dated to 7.73 Mya, with a 95% highest posterior density (HPD) of 3.14?12.53 Mya, using the Bayesian relaxed clock estimation. Ancestral area reconstructions suggest that the genus originated in eastern Asia. The semishrub Mitchella appears to have arisen from its woody ancestor in eastern Asia and then migrated to North America via the Bering land bridge in the late Miocene. © 2013 The Linnean Society of London     

Erratum to: Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

The genus Stevia comprises approximately 200 species, which are distributed in North and South America, and are representative of the species diversity of the Asteraceae in the New World. We reconstructed the phylogenetic relationships using sequences of ITS and cpDNA and estimated the divergence times of the major clade of this genus. Our results suggested that Stevia originated in Mexico 7.0–7.3 million years ago (Mya). Two large clades, one with shrub species and another with herb species, were separated at about 6.6 Mya. The phylogenetic reconstruction suggested that an ancestor of Stevia was a small shrub in temperate pine–oak forests and the evolutionary change from a shrub state to a herb state occurred only once. A Brazilian clade was nested in a Mexican herb clade, and its origin was estimated to be 5.2 Mya, suggesting that the migration from North America to South America occurred after the formation of the Isthmus of Panama. The species diversity in Mexico appears to reflect the habitat diversity within the temperate pine–oak forest zone. The presence of many conspecific diploid–polyploid clades in the phylogenetic tree reflects the high frequency of polyploidization among the perennial Stevia species.

     

Molecular phylogenetics and biogeography of the Neotropical redstarts (Myioborus; Aves, Parulinae)

Montane areas in the Neotropics are characterized by high diversity and endemism of birds and other groups. The avian genus Myioborus (Parulinae) is a group of insectivorous warblers, characteristic of cloud forests, that represents one of the few Parulinae genera (New World warblers) that has radiated substantially in South America. The genus is distributed throughout most montane regions from the southwestern United States to northern Argentina. Here, I use mitochondrial sequences from the cytochrome b, ND2, and ND3 genes to present the first hypothesis of phylogenetic relationship among all Myioborus species level taxa. Phylogenetic reconstructions based on maximum parsimony, maximum likelihood, and Bayesian methods produced similar results and suggest a northern origin for the genus Myioborus with subsequent colonization of the Neotropical Montane Region. The lower-montane species, M. miniatus, is the sister taxon to a clade in which all taxa occupy upper-montane habitats. These "highland" taxa diverged early in the history of the genus and produced two well-defined monophyletic lineages, a Central-northern Andean clade formed by M. albifrons, M. ornatus, and M. melanocephalus, and a Pantepui (table-mountains of southern Venezuela, northern Brazil, and western Guyana) clade consisting of M. castaneocapillus, M. albifacies, and M. cardonai, and probably M. pariae. M. brunniceps, M. flavivertex, and M. torquatus were included in this upper-montane clade but without clear relationships to other taxa. Lack of resolution of nodes defining the upper-montane species clade is likely to result from a period of rapid diversification mediated by geological and climatic events during the Late Pliocene. These results suggest that an interplay of dispersal and vicariance has shaped the current biogeographic patterns of Myioborus.     

New insight into the phylogenetic and biogeographic history of genus Ficus: Vicariance played a relatively minor role compared with ecological opportunity and dispersal

Studies on the evolution of tropical taxa emphasize the role ofvicariance and the break-up of Gondwana in explaining modern distributions.Earlier studies on figs (Ficus spp.) support this view.In the current study,we used an expanded sample (208 spp.) and improved molecular dating techniques to reconstruct the phylogenetic and biogeographic history of Ficus.Consistent with previous studies,our biogeographic analysis indicated that the ancestor of Ficus was present in Gondwana.However,a relaxed clock analysis relying on uncorrelated rates in BEAST suggested that the Neotropical section Pharmacosycea split-off in South America 86.67 Mya,and that other Ficus lineage ancestors originated in India.Most of the basal lineages appeared to have diverged following KT extinction,then rapidly diversified after India collided with continental Asia.The Afrotropical species most likely evolved initially in the Indian subcontinent then dispersed to Africa,either in the late Cretaceous of Madagascar or even later,following the Eocene collision of India with Asia.The Neotropical section Americana,either islandhopped to South America or took a northern route to the Americas through Europe prior to the terminal Eocene global cooling event.Ficus may have arrived in eastern Malesia following the collision of India with Asia,then widely dispersed thereafter.Given the wide ranges in our date estimates,several other scenarios are possible.However,contrary to earlier reports,our analyses suggest that vicariance played a relatively minor role compared with ecological opportunity and dispersal in the diversification of genus Ficus.     

The evolution of South American endemic canids: a history of rapid diversification and morphological parallelism

The origin of endemic South American canid fauna has been traditionally linked with the rise of the Isthmus of Panama, suggesting that diversification of the dog fauna on this continent occurred very rapidly. Nevertheless, despite its obvious biogeographic appeal, the tempo of Canid evolution in South America has never been studied thoroughly. This issue can be suitably tackled with the inference of a molecular timescale. In this study, using a relaxed molecular clock method, we estimated that the most recent common ancestor of South American canids lived around 4 Ma, whereas all other splits within the clade occurred after the rise of the Panamanian land bridge. We suggest that the early diversification of the ancestors of the two main lineages of South American canids may have occurred in North America, before the Great American Interchange. Moreover, a concatenated morphological and molecular analysis put some extinct canid species well within the South American radiation, and shows that the dental adaptations to hypercarnivory evolved only once in the South American clade.     

Geographic patterns in morphometric and genetic variation for coyote populations with emphasis on southeastern coyotes

Prior to 1900, coyotes (Canis latrans) were restricted to the western and central regions of North America, but by the early 2000s, coyotes became ubiquitous throughout the eastern United States. Information regarding morphological and genetic structure of coyote populations in the southeastern United States is limited, and where data exist, they are rarely compared to those from other regions of North America. We assessed geographic patterns in morphology and genetics of coyotes with special consideration of coyotes in the southeastern United States. Mean body mass of coyote populations increased along a west‐to‐east gradient, with southeastern coyotes being intermediate to western and northeastern coyotes. Similarly, principal component analysis of body mass and linear body measurements suggested that southeastern coyotes were intermediate to western and northeastern coyotes in body size but exhibited shorter tails and ears from other populations. Genetic analyses indicated that southeastern coyotes represented a distinct genetic cluster that differentiated strongly from western and northeastern coyotes. We postulate that southeastern coyotes experienced lower immigration from western populations than did northeastern coyotes, and over time, genetically diverged from both western and northeastern populations. Coyotes colonizing eastern North America experienced different selective pressures than did stable populations in the core range, and we offer that the larger body size of eastern coyotes reflects an adaptation that improved dispersal capabilities of individuals in the expanding range.     

Extensive genetic differentiation in Gobiomorphus breviceps from New Zealand

Partial mitochondrial DNA sequences for parts of the cytochrome b gene and control region were obtained for 89 upland bullies Gobiomorphus breviceps from 19 catchments in New Zealand. There were two highly distinctive mtDNA clades: a northern clade corresponding to the North Island, northern South Island and west coast South Island, and a south‐east clade, in the southern and eastern South Island. Within these major clades there were further distinct clades that correlated with geographic sub‐regions and catchments. The marked genetic differentiation has occurred in the absence of obvious morphological divergence. Based on cytochrome b sequence divergences and the molecular clock hypothesis, the northern and southeastern clades correspond with the uplift of the Southern Alps during the Pliocene, while populations in the North Island and northern South Island were estimated to have diverged during the Pleistocene. The widescale geographic divergences were similar to those observed in the galaxiids, Galaxias vulgaris and Galaxias divergens , but biogeographic management boundaries may not be the same, reflecting different evolutionary histories for non‐diadromous species occupying the same areas.     

Phylogeny and historical biogeography of true morels (Morchella) reveals an early Cretaceous origin and high continental endemism and provincialism in the Holarctic

True morels (Morchella, Ascomycota) are arguably the most highly-prized of the estimated 1.5 million fungi that inhabit our planet. Field guides treat these epicurean macrofungi as belonging to a few species with cosmopolitan distributions, but this hypothesis has not been tested. Prompted by the results of a growing number of molecular studies, which have shown many microbes exhibit strong biogeographic structure and cryptic speciation, we constructed a 4-gene dataset for 177 members of the Morchellaceae to elucidate their origin, evolutionary diversification and historical biogeography. Diversification time estimates place the origin of the Morchellaceae in the middle Triassic 243.63 (95% highest posterior density [HPD] interval: 169.35-319.89) million years ago (Mya) and the divergence of Morchella from its closest relatives in the early Cretaceous 129.61 (95% HPD interval: 90.26-173.16) Mya, both within western North America. Phylogenetic analyses identified three lineages within Morchella: a basal monotypic lineage represented by Morchella rufobrunnea, and two sister clades comprising the black morels (Elata Clade, 26 species) and yellow morels (Esculenta Clade, 16 species). Morchella possesses a Laurasian distribution with 37/41 species restricted to the Holarctic. All 33 Holarctic species represented by multiple collections exhibited continental endemism. Moreover, 16/18 North American and 13/15 Eurasian species appeared to exhibit provincialism. Although morel fruit bodies produce thousands of explosively discharged spores that are well suited to aerial dispersal, our results suggest that they are poorly adapted at invading novel niches. Morels also appear to have retained the ancestral fruit body plan, which has remained remarkably static since the Cretaceous.     

Biogeography and ecological niche evolution in Diapensiaceae inferred from phylogenetic analysis

Diapensiaceae (Ericales) are a small family of about 15 species. Within this clade, two species are broadly distributed throughout the Northern Hemisphere, whereas the remaining species have a disjunct distribution between eastern North America and eastern Asia. To address patterns and processes of diversification in Diapensiaceae, we conducted biogeographic analyses and inferred shifts in the ecological niche across the phylogeny of the clade. Although Diapensiaceae have been the focus of multiple phylogenetic and biogeographic studies, previous studies have been taxonomically limited. This study has greatly improved the phylogenetic underpinning for Diapensiaceae with the most inclusive taxonomic sampling thus far, employing both nuclear and plastid gene sequence data for at least one sample per species in the family. Our estimates indicate that genera of Diapensiaceae variously diverged in the Eocene, Oligocene, and early to mid‐Miocene. The biogeographic analysis suggests that the probable ancestor of the Diapensiaceae crown clade originated in the Nearctic, with vicariance events contributing to the current distribution of the disjunct taxa. Ecological niche, when considered in a phylogenetic context, was observed to be clustered on the basis of biogeographic realm. In general, a greater ecological overlap was found at younger nodes and a greater niche divergence was found among distantly related species. Diversification in Diapensiaceae appears to have been shaped by both large‐scale biogeographic factors, such as vicariance, and divergence in an ecological niche among closely related species.     

Do ecological communities disperse across biogeographic barriers as a unit?

Biogeographic barriers have long been implicated as drivers of biological diversification, but how these barriers influence co‐occurring taxa can vary depending on factors intrinsic to the organism and in their relationships with other species. Due to the interdependence among taxa, ecological communities present a compelling opportunity to explore how interactions among species may lead to a shared response to historical events. Here we collect single nucleotide polymorphism data from five commensal arthropods associated with the Sarracenia alata carnivorous pitcher plant, and test for codiversification across the Mississippi River, a major biogeographic barrier in the southeastern United States. Population genetic structure in three of the ecologically dependent arthropods mirrors that of the host pitcher plant, with divergence time estimates suggesting two of the species (the pitcher plant moth Exyra semicrocea and a flesh fly Sarcophaga sarraceniae) dispersed synchronously across this barrier along with the pitcher plant. Patterns in population size and genetic diversity suggest the plant and ecologically dependent arthropods dispersed from east to west across the Mississippi River. In contrast, species less dependent on the plant ecologically show discordant phylogeographic patterns. This study demonstrates that ecological relationships may be an important predictor of codiversification, and supports recent suggestions that organismal trait data should be prominently featured in comparative phylogeographic investigations.     

Biogeographic effects of red fire ant invasion

The red imported fire ant, Solenopsis invicta , was accidentally introduced to North America over 60 years ago and has spread throughout the southeastern United States. We document the biogeographic consequences of this invasion. We censused ground-foraging ant communities on a 2000 km transect from Florida through New York that passed through invaded and intact biotas. Native ant species density peaks at mid-latitudes in the eastern United States, and the location of this peak corresponds to the range limit of S. invicta . In uninvaded sites, ant species co-occur less often than expected by chance. In the presence of S. invicta , community structure converges to a random pattern. Our results suggest that the effects of S. invicta on native ant communities are pervasive: not only does the presence of S. invicta reduce species density at local scales, it alters the co-occurrence patterns of surviving species at a biogeographic scale.     

Diversification of Lupinus (Leguminosae) in the western New World: derived evolution of perennial life history and colonization of montane habitats

Previous phylogenetic studies of Lupinus (Leguminosae) based on nuclear DNA have shown that the western New World taxa form a monophyletic group representing the majority of species in the genus, with evidence for high rates of recent diversification in South America following final uplift of the Andes 2–4 million years ago (Mya). For this study, three regions of rapidly evolving non-coding chloroplast DNA (trnL intron, trnS–trnG, and trnT–trnL) were examined to estimate the timing and rates of diversification in the western New World, and to infer ancestral states for geographic range, life history, and maximum elevation. The western New World species (5.0–9.3 Mya, 0.6–1.1 spp./My) comprise a basally branching assemblage of annual plants endemic to the lower elevations of western North America, from which two species-rich clades are recently derived: (i) the western North American perennials from the Rocky Mountains, Great Basin, and Pacific Slope (0.7–2.1 Mya, 2.0–5.9 spp./My) and (ii) the predominantly perennial species from the Andes Mountains of South America and highlands of Mexico (0.8–3.4 Mya, 1.4–5.7 spp./My). Bayesian posterior predictive tests for association between life history and maximum elevation demonstrate that perennials are positively correlated with higher elevations. These results are consistent with a series of one or more recent radiations in the western New World, and indicate that rapid diversification of Lupinus coincides with the derived evolution of perennial life history, colonization of montane habitats, and range expansion from North America to South America.     

Phylogenetic relationships and historical biogeography of neotropical parrots (Psittaciformes: Psittacidae: Arini) inferred from mitochondrial and nuclear DNA sequences

Previous hypotheses of phylogenetic relationships among Neotropical parrots were based on limited taxon sampling and lacked support for most internal nodes. In this study we increased the number of taxa (29 species belonging to 25 of the 30 genera) and gene sequences (6388 base pairs of RAG-1, cyt b, NADH2, ATPase 6, ATPase 8, COIII, 12S rDNA, and 16S rDNA) to obtain a stronger molecular phylogenetic hypothesis for this group of birds. Analyses of the combined gene sequences using maximum likelihood and Bayesian methods resulted in a well-supported phylogeny and indicated that amazons and allies are a sister clade to macaws, conures, and relatives, and these two clades are in turn a sister group to parrotlets. Key morphological and behavioral characters used in previous classifications were mapped on the molecular tree and were phylogenetically uninformative. We estimated divergence times of taxa using the molecular tree and Bayesian and penalized likelihood methods that allow for rate variation in DNA substitutions among sites and taxa. Our estimates suggest that the Neotropical parrots shared a common ancestor with Australian parrots 59 Mya (million of years ago; 95% credibility interval (CrI) 66, 51 Mya), well before Australia separated from Antarctica and South America, implying that ancestral parrots were widespread in Gondwanaland. Thus, the divergence of Australian and Neotropical parrots could be attributed to vicariance. The three major clades of Neotropical parrots originated about 50 Mya (95% CrI 57, 41 Mya), coinciding with periods of higher sea level when both Antarctica and South America were fragmented with transcontinental seaways, and likely isolated the ancestors of modern Neotropical parrots in different regions in these continents. The correspondence between major paleoenvironmental changes in South America and the diversification of genera in the clade of amazons and allies between 46 and 16 Mya suggests they diversified exclusively in South America. Conversely, ancestors of parrotlets and of macaws, conures, and allies may have been isolated in Antarctica and/or the southern cone of South America, and only dispersed out of these southern regions when climate cooled and Antarctica became ice-encrusted about 35 Mya. The subsequent radiation of macaws and their allies in South America beginning about 28 Mya (95% CrI 22, 35 Mya) coincides with the uplift of the Andes and the subsequent formation of dry, open grassland habitats that would have facilitated ecological speciation via niche expansion from forested habitats.     

Molecular systematics and historical biogeography of tree boas (Corallus spp.)

Inferring the evolutionary and biogeographic history of taxa occurring in a particular region is one way to determine the processes by which the biodiversity of that region originated. Tree boas of the genus Corallus are an ancient clade and occur throughout Central and South America and the Lesser Antilles, making it an excellent group for investigating Neotropical biogeography. Using sequenced portions of two mitochondrial and three nuclear loci for individuals of all recognized species of Corallus, we infer phylogenetic relationships, present the first molecular analysis of the phylogenetic placement of the enigmatic C. cropanii, develop a time-calibrated phylogeny, and explore the biogeographic history of the genus. We found that Corallus diversified within mainland South America, via over-water dispersals to the Lesser Antilles and Central America, and via the traditionally recognized Panamanian land bridge. Divergence time estimates reject the South American Caribbean-Track as a general biogeographic model for Corallus and implicate a role for events during the Oligocene and Miocene in diversification such as marine incursions and the uplift of the Andes. Our findings also suggest that recognition of the island endemic species, C. grenadensis and C. cookii, is questionable as they are nested within the widely distributed species, C. hortulanus. Our results highlight the importance of using widespread taxa when forming and testing biogeographic hypotheses in complex regions and further illustrate the difficulty of forming broadly applicable hypotheses regarding patterns of diversification in the Neotropical region.     

Biogeographic and diversification patterns of Neotropical Troidini butterflies (Papilionidae) support a museum model of diversity dynamics for Amazonia

ABSTRACT: BACKGROUND: The temporal and geographical diversification of Neotropical insects remains poorly understood because of the complex changes in geological and climatic conditions that occurred during the Cenozoic. To better understand extant patterns in Neotropical biodiversity, we investigated the evolutionary history of three Neotropical swallowtail Troidini genera (Papilionidae). First, DNA-based species delimitation analyses were conducted to assess species boundaries within Neotropical Troidini using an enlarged fragment of the standard barcode gene. Molecularly delineated species were then used to infer a time-calibrated species-level phylogeny based on a three-gene dataset and Bayesian dating analyses. The corresponding chronogram was used to explore their temporal and geographical diversification through distinct likelihood-based methods. RESULTS: The phylogeny for Neotropical Troidini was well resolved and strongly supported. Molecular dating and biogeographic analyses indicate that the extant lineages of Neotropical Troidini have a late Eocene (33-42 Ma) origin in North America. Two independent lineages (Battus and Euryades+Parides) reached South America via the GAARlandia connection, and later became extinct in North America. They only began substantive diversification during the Miocene in Amazonia. Macroevolutionary analysis supports the "museum model" of diversification, rather than Pleistocene refugia, as the best explanation for the diversification of these lineages. CONCLUSIONS: This study demonstrates that: (i) current Neotropical biodiversity may have originated ex situ; (ii) the GAARlandia bridge was important in facilitating invasions of South America; (iii) colonization of Amazonia initiated the crown diversification of these swallowtails; and (iv) Amazonia is not only a species-rich region but also acted as a sanctuary for the dynamics of this diversity. In particular, Amazonia probably allowed the persistence of old lineages and contributed to the steady accumulation of diversity over time with constant net diversification rates, a result that contrasts with previous studies on other South American butterflies.     

Biogeography of mutualistic fungi cultivated by leafcutter ants

Leafcutter ants propagate co‐evolving fungi for food. The nearly 50 species of leafcutter ants (Atta, Acromyrmex) range from Argentina to the United States, with the greatest species diversity in southern South America. We elucidate the biogeography of fungi cultivated by leafcutter ants using DNA sequence and microsatellite‐marker analyses of 474 cultivars collected across the leafcutter range. Fungal cultivars belong to two clades (Clade‐A and Clade‐B). The dominant and widespread Clade‐A cultivars form three genotype clusters, with their relative prevalence corresponding to southern South America, northern South America, Central and North America. Admixture between Clade‐A populations supports genetic exchange within a single species, Leucocoprinus gongylophorus. Some leafcutter species that cut grass as fungicultural substrate are specialized to cultivate Clade‐B fungi, whereas leafcutters preferring dicot plants appear specialized on Clade‐A fungi. Cultivar sharing between sympatric leafcutter species occurs frequently such that cultivars of Atta are not distinct from those of Acromyrmex. Leafcutters specialized on Clade‐B fungi occur only in South America. Diversity of Clade‐A fungi is greatest in South America, but minimal in Central and North America. Maximum cultivar diversity in South America is predicted by the Kusnezov–Fowler hypothesis that leafcutter ants originated in subtropical South America and only dicot‐specialized leafcutter ants migrated out of South America, but the cultivar diversity becomes also compatible with a recently proposed hypothesis of a Central American origin by postulating that leafcutter ants acquired novel cultivars many times from other nonleafcutter fungus‐growing ants during their migrations from Central America across South America. We evaluate these biogeographic hypotheses in the light of estimated dates for the origins of leafcutter ants and their cultivars.