Lower Central America Research Articles

Unraveling the complex phylogeographic history of freshwater fishes in Lower Central America: A study of the electric fish Brachyhypopomus occidentalis

Lower Central America (LCA) has a complex biogeographic history shaped by the rise of the Isthmus of Panama and the global climatic oscillations of the Pleistocene. These events have been crucial in structuring biodiversity in LCA, but their consequences for the distribution and partitions of genetic diversity across the region remain to be elucidated. We combined complete mitochondrial genomes and nuclear ultraconserved elements (UCEs) to study the phylogeographic history and population genetic structure of the electric fish Brachyhypopomus occidentalis in LCA. Our results are consistent with the known phylogeographic history of B. occidentalis in LCA, but we update this history in several important ways that help illuminate the phylogeographic history of freshwater fishes in the region. We provide: i) support for three waves of colonization, two of which occurred prior to the final closure of the Panama Isthmus; ii) a more precise understanding of each colonization event, with evidence for a larger footprint of the first event, as well as genetic exchange across the continental divide in subsequent events; and iii) evidence for high levels of previously unrecognized population genetic structure across LCA. This updated model of colonization and diversification of B. occidentalis consists of three waves of dispersal and colonization, which triggered the evolution of geographic breaks in both nuclear and mitochondrial genomes across LCA. These processes are tightly linked to the dynamic uplift of the Isthmus, recent volcanic activity in the region, and the sea-level oscillations of the Pleistocene. These results improve previous phylogeographic inferences regarding the distribution and diversification of freshwater fishes in LCA, and generate testable hypotheses to guide future research exploring the factors shaping biodiversity in the region.

Early Maize in the Maya Area

The history of maize in Central America and surrounding areas has implications for the slow transition from hunting and gathering to agriculture. The spread of early forms of domesticated maize from southern Mexico across Mesoamerica and into South America has been dated to about 8,700–6,500 years ago on the basis of a handful of studies relying primarily on the analysis of pollen, phytoliths, or starch grains. Recent genomic data from southern Belize have been used to identify Archaic period south-to-north population movements from lower Central America, suggesting this migration pattern as a mechanism that introduced genetically improved maize races from South America. Gradually, maize productivity increased to the point that it was suitable for use as a staple crop. Here we present a summary of paleoecological data that support the late and uneven entry of maize into the Maya area relative to other regions of Central America and identify the Pacific coastal margin as the probable route by which maize spread southward into Panama and South America. We consider some implications of the early appearance of maize for Late Archaic populations in these areas; for example, with respect to the establishment of sedentary village life.

De Novo Genome Assembly of the Electric Fish Brachyhypopomus occidentalis (Hypopomidae, Gymnotiformes).

The bluntnose knifefish Brachyhypopomus occidentalis is a primary freshwater fish from north-western South America and Lower Central America. Like other Gymnotiformes, it has an electric organ that generates electric discharges used for both communication and electrolocation. We assembled a high-quality reference genome sequence of B. occidentalis by combining Oxford Nanopore and 10X Genomics linked-reads technologies. We also describe its demographic history in the context of the rise of the Isthmus of Panama. The size of the assembled genome is 540.3 Mb with an N50 scaffold length of 5.4 Mb, which includes 93.8% complete, 0.7% fragmented, and 5.5% of missing vertebrate/Actinoterigie Benchmarking Universal Single-Copy Orthologs. Repetitive elements account for 11.04% of the genome, and 34,347 protein-coding genes were predicted, of which 23,935 have been functionally annotated. Demographic analysis suggests a rapid effective population expansion between 3 and 5 Myr, corresponding to the final closure of the Isthmus of Panama (2.8–3.5 Myr). This event was followed by a sudden and constant population decline during the last 1 Myr, likely associated with strong shifts in both precipitation and sea level during the Pleistocene glacial-interglacial cycles. The de novo genome assembly of B. occidentalis will provide novel insights into the molecular basis of both electric signal productions and detection and will be fundamental for understanding the processes that have shaped the diversity of Neotropical freshwater environments.

Chacmools in Costa Rica: long-distance interaction between lower Central America and Mesoamerica,c. AD 1000

Abstract

ON THE IDENTITY OF HOG-NOSED PIT-VIPERS FROM WESTERN PANAMA: A REVIEW OF SPECIMENS OF PORTHIDIUM LANSBERGII (SCHLEGEL, 1841) IN LOWER CENTRAL AMERICA.

Porthidium lansbergii is a relatively abundant pit viper in semiarid environments from eastern Panama, through the Caribbean plains and Magdalena Valley in Colombia to northeastern Venezuela. Like other members of this genus, P. lansbergii exhibits great variation in scutellation and other morphological characters, a situation that has complicated the taxonomy and identification of populations assigned to the species. In Lower Central America, P. lansbergii is known to inhabit seasonally-dry environments of the Pacific slopes of western Panama. Here, we aimed to clarify the taxonomic status of some enigmatic specimens collected in western Panama, with morphological ambiguity, resembling P. lansbergii. We used the mitochondrial marker cytochrome oxidase b to perform a Bayesian phylogenetic analysis, to evaluate the affinities ofthese specimens with P. lansbergii individuals from central and eastern Panama, and Venezuela. We also analyzed meristic morphological characters to discriminate among populations of P. lansbergii in Panama, including other species of the Porthidium genus. Our analyses indicate that the enigmatic individuals do not differ from others individuals identified as P. lansbergii, thus forming a monophyletic group. We conclude that P. lansbergii has a more extended range than currently recognized including the western Pacific in Panama.

Venom diversity in the Neotropical scorpion genus Tityus: Implications for antivenom design emerging from molecular and immunochemical analyses across endemic areas of scorpionism

Scorpions of the Neotropical genus Tityus are responsible for most severe envenomations in the Caribbean, South America, and Lower Central America (LCA). Although Tityus is taxonomically complex, contains high toxin polymorphism, and produces variable clinical manifestations, treatment is limited to antivenoms produced against species with restricted distributions. In this study, we explored the compositional and antigenic diversity of Tityus venoms to provide improved guidelines for the use of available antivenoms at a broader geographic scale. We used immunoblotting, competitive ELISA, and in vivo studies to compare reactivity against commercial antivenoms from Brazil, Venezuela, and Mexico, as well as MALDI-TOF mass spectrometry, cDNA sequencing, and phylogenetic analyses to assess venom sodium channel-active toxin (NaTx) content from medically important Tityus populations inhabiting Brazil, Colombia, Costa Rica, Ecuador, Panama, Trinidad and Tobago, and Venezuela. Additionally, we raised rabbit antibodies against Tityus venoms from LCA to test for cross-reactivity with congeneric species. The results suggest that Tityus spp. possess high venom antigenic diversity, underlying the existence of four toxinological regions in Tropical America, based on venom composition and immunochemical criteria: LCA/Colombia/Amazonia (Region I), Venezuela (Region II), southeast South America (Region III), and a fourth region encompassing species related to toxinologically divergent Tityus cerroazul. Importantly, our molecular and cross-reactivity results highlight the need for new antivenoms against species inhabiting Region I, where scorpions may produce venoms that are not significantly reactive against available antivenoms.

Phylogeny, taxonomy and distribution of the Neotropical lizard genus Echinosaura (Squamata: Gymnophthalmidae), with the recognition of two new genera in Cercosaurinae

AbstractThe family Gymnophthalmidae is a highly diverse Neotropical lizard clade. Although multiple phylogenetic and taxonomic studies have reshaped our understanding of gymnophthalmid systematics and diversity, many groups remain understudied. This is the case for the cercosaurine genus Echinosaura, which includes eight species of small riparian lizards distributed across lower Central America and northern South America. Here, we present a comprehensive phylogenetic analysis of Echinosaura, including DNA data for all species of the genus for the first time. To rigorously test the relationships of all Echinosaura, we have assembled the largest molecular dataset of cercosaurine lizards to date. Our analysis refutes the monophyly of Echinosaura, with E. apodema and E. sulcarostrum not closely related to the remaining species. To remedy the polyphyly of Echinosaura, we describe two new genera for E. apodema and E. sulcarostrum. Morphological distinctiveness and biogeography further support these taxonomic changes. In light of our phylogenetic results, we review the species-level taxonomy of the redefined Echinosaura based on morphological and genetic variation. We resurrect E. centralis and designate a neotype given the absence of type and topotypic material. In addition, we provide taxonomic accounts for each species and analyse their patterns of geographic distribution.

Comparative phylogeography of trans-Andean freshwater fishes based on genome-wide nuclear and mitochondrial markers.

The Neotropical region represents one of the greatest biodiversity hot spots on earth. Despite its unparalleled biodiversity, regional comparative phylogeographic studies are still scarce, with most focusing on model clades (e.g. birds) and typically examining a handful of loci. Here, we apply a genome-wide comparative phylogeographic approach to test hypotheses of codiversification of freshwater fishes in the trans-Andean region. Using target capture methods, we examined exon data for over 1,000 loci combined with complete mitochondrial genomes to study the phylogeographic history of five primary fish species (>150 individuals) collected from eight major river basins in Northwestern South America and Lower Central America. To assess their patterns of genetic structure, we inferred genealogical concordance taking into account all major aspects of phylogeography (within loci, across multiple genes, across species and among biogeographic provinces). Based on phylogeographic concordance factors, we tested four a priori biogeographic hypotheses, finding support for three of them and uncovering a novel, unexpected pattern of codiversification. The four emerging inter-riverine patterns are as follows: (a) Tuira+Atrato, (b) Ranchería+Catatumbo, (c) Magdalena system and (d) Sinú+Atrato. These patterns are interpreted as shared responses to the complex uplifting and orogenic processes that modified or sundered watersheds, allowing codiversification and speciation over geological time. We also find evidence of cryptic speciation in one of the species examined and instances of mitochondrial introgression in others. These results help further our knowledge of the historical geographic factors shaping the outstanding biodiversity of the Neotropics.

Contrasting Patterns of Population History and Seed-mediated Gene Flow in Two Endemic Costa Rican Oak Species.

Lower Central America is an important area to study recent population history and diversification of Neotropical species due to its complex and dynamic geology and climate. Phylogeographic studies in this region are few in comparison with other regions and even less for tree species. The aim of the present study was to characterize the phylogeographic structure in 2 partially co-distributed endemic oak species (Quercus costaricensis and Q. bumelioides) of the Costa Rican mountains using chloroplast short sequence repeats (cpSSRs), and to test for the effect of geological and palaeoclimatic processes on their population history. Genetic diversity and structure, haplotype networks, patterns of seed-mediated gene flow and historical demography were estimated for both species. Results suggested contrasting patterns. Quercus costaricensis exhibited high values of genetic diversity, a marked phylogeographic structure, a north-to-south genetic diversity gradient and evidence of a demographic expansion during the Quaternary. Quercus bumelioides did not show significant genetic structure and the haplotype network and historical demography estimates suggested a recent population expansion probably during the Pleistocene-Holocene transition. The phylogeographic structure of Q. costaricensis seems to be related to Pleistocene altitudinal migration due to its higher altitudinal distribution. Meanwhile, historical seed-mediated gene flow through the lower altitudinal distribution of Q. bumelioides may have promoted the homogenization of genetic variation. Population expansion and stable availability of suitable climatic areas in both species probably indicate that palaeoclimatic changes promoted downwards altitudinal migration and formation of continuous forests allowing oak species to expand their distribution into the Panamanian mountains during glacial stages.

Taxonomic status of the atherinid fish genus Melaniris in lower Central America, with the description of three new species

Seven species of Melaniris from southern Central America are discussed, their distributions are given, and a key to their identification is provided. Melaniris guatemalensis inhabits Pacific coastal lagoons and estuaries between Guatemala and southern Costa Rica. M. beani, known only from Colon. Panama, and M. milleri, n. sp. from Atlantic Nicaragua and Costa Rica arc principally brackish water forms, but the latter also frequents the Rio San Juan basin a great distance from the sea. M. hubbsi, n. sp. occurs in the Rio Escondido and San Juan drainages and is replaced in rivers to the south by M. chagresi which reaches to central Panama. M. sardina is a lacustrine species found in several Nicaraguan lakes and in the Rio Sapoa. Costa Rica. M. jiloaensis, n. sp. is endemic to Lake Jiloa, Nicaragua.

Phylogeny and biogeography of Poecilia (Cyprinodontiformes: Poeciliinae) across Central and South America based on mitochondrial and nuclear DNA markers

Poeciliids are a diverse group of small Neotropical fishes, and despite considerable research attention as models in ecology and evolutionary biology, our understanding of their biogeographic and phylogenetic relationships is still limited. We investigated the phylogenetic relationships of South and Central American Poecilia, by examining 2395 base pairs of mitochondrial DNA (ATPase 8/6, COI) and nuclear DNA (S7) for 18 species across six subgenera. Fifty-eight novel sequences were acquired from newly collected specimens and 20 sequences were obtained from previously published material. Analyses of concatenated and partitioned mitochondrial DNA and nuclear DNA sets resulted in a well-supported phylogeny that resolved several monophyletic groups corresponding to previously hypothesized subgenera and species complexes.A divergence-dating analysis supported the hypothesis of the genus Poecilia dispersing into Central America in the early Pliocene (ancestors of Psychropoecilia+Allopoecilia+Mollienesia: 7.3–2.0Mya) from predominantly South America. Subsequently, one lineage (subgenus Allopoecilia: 5.1–1.3Mya) expanded deeper into South America from Lower-Central America, and one lineage expanded from Nuclear-Central America into South America (subgenus Mollienesia: 0.71–0.14Mya). The subgenus Mollienesia diverged into three monophyletic groups that can be identified by nuptial male dorsal fin morphology and inner jaw dentition. A subclade of the unicuspid short-fins (subgenus Mollienesia) was the lineage that expanded into South America during the middle Pleistocene. Species in this subclade are now distributed across northern South America, where they are partially sympatric with Allopoecilia. However the P. (A.) caucana complex was not monophyletic, with P. (A.) wandae clustering in the Mollienesia subclade that expanded into South America. It is apparent that characters (body size, scale count, pigmentation, and gonopodium morphology) used to define the P. (A.) caucana complex are homoplastic and suggestive of rapid convergence in northern South America. Our improved taxon sampling and divergence-time calibration allowed for insights into the timing and direction of dispersals, and provides an improved understanding of the biogeographic history of an enigmatic group of fishes. Furthermore, we provided strong evidence for the monophyly of the subgenus Mollienesia and further substantiated its species complexes; therefore, we advise a taxonomic re-evaluation for the P. (A.) caucana complex to maintain monophyly of both Mollienesia and Allopoecilia.

New records of snipe eels (Anguilliformes: Nemichthyidae) from the Pacific coast of lower Central America

New records of occurrence of two snipe eels (Avocettina bowersii and Nemichthys scolopaceus), poorly known for the Pacific coast of Costa Rica and Panama are herein reported. Specimens, 45 in total (28 and 17, respectively), were collected between 1972 and 1973 at depths between 295 and 1000 m. Descriptions based on specimens as well as comparative morphometric and distributional information by species are herein presented and discussed. A key to the identification of the eastern Pacific species of the family also is presented. These findings increase the knowledge on the Central American marine ichthyofauna and provide evidence of a broader distributional pattern for these species in the eastern Pacific region.

The less-splendid isolation of the South American continent

news and update ISSN 1948-6596 commentary The less-splendid isolation of the South American continent Only few biogeographic scenarios capture the im- agination as much as the closure of the Isthmus of Panama. The establishment of this connection ended the “splendid isolation” of the South Amer- ican continent (Simpson 1980), a continent that had been unconnected to any other land mass for over 50 million years. When the Isthmus rose out of the water some 3 million years ago (mya) the Great American Biotic Interchange started. Since terrestrial biotic interchange was no longer blocked by the Central American Seaway, (asymmetrical) invasion of taxa across this new land bridge transformed biodiversity in North as well as South America (Leigh et al. 2014). Or so the story goes. A recent paper by Montes et al. (2015) casts further serious doubt on this scenario from a geo- logical perspective. They show that a river system existed, originating in the volcanic arc of Panama and flowing into northern Colombia, about 15 to 13 mya. They base this hypothesis on geological mapping in conjunction with geochronological analyses of river deposits found in northern Co- lombia. With this they built on previous work (Farris et al. 2011, Montes et al. 2012a,b) in which the hypothesis of a fairly recent closure of the Isthmus was also questioned. Montes et al. (2015) reason that when a river system existed in the Panama-Colombia area, a terrestrial connection needed to be present. Any connection between the Caribbean Sea and Pacific Ocean could only have existed to the west of the current day Pana- ma Canal area, where they postulate the origin of this river system. So, how do these data fit in with what biolo- gists know about migrations between North and South America? Leigh et al. (2014) provide a com- prehensive overview of the historical biogeogra- phy of the Isthmus and review for instance that ground sloths had reached North from South America around 10 million years ago and Panama was well populated with all kinds of animals in the Early Miocene (18-19 mya), that fresh water fishes already dispersed in the late Miocene between lower Central America (Costa Rica) and South America (northern Colombia), and that some snapping shrimp populations were already split long before the Isthmus had finally closed (most between 7–10 mya but some >15 mya). Next to this, several papers showed that plants also mi- grated between North and South America prior to the closure of the Isthmus (e.g., Erkens et al. 2007, Bacon et al. 2013), although for plants it is difficult to rule out that this happened via long-distance dispersal. Thus, the new findings of Montes and colleagues fit much better with a wealth of evi- dence from the biological realm that has been amassed over the last years, than the old model of a relatively rapid rise of the Isthmus. If the land-bridge was available much earli- er to many terrestrial organisms, the question that remains, of course, is why they only began to mi- grate in large numbers between North and South America around 3 mya? The generally accepted scenario that a wide seaway blocked their path is, given the above mentioned studies, not support- ed. The answer can probably be found in two di- rections. First of all, the sudden onset at 3 mya is just a remnant from past analyses. As discussed above, earlier migrations indeed have been found and the onset itself of the interchange is placed much earlier than previously accepted (Carrillo et al. 2015), starting already around 10 mya. Alt- hough the bulk of migrations might have hap- pened more recently, the onset is more gradual than was postulated. Second, another type of ex- planation can be found in the type of vegetation present (Leigh et al. 2014), accepting that species ranges can be limited by more than geographic barriers alone (Feeley et al. 2014). Due to climatic cooling around 3 mya a corridor of grassland and savannah allowed open-country animals and some plants to move between North and South America (Molnar 2008, Bacon 2013). Before and after cooling such migration was not possible since tropical forests formed effective obstacles to any migration of these open-country animals. Sup- port for such a scenario is, for instance, provided frontiers of biogeography 7.3, 2015 — © 2015 the authors; journal compilation © 2015 The International Biogeography Society

Phylogenetic analyses provide insights into the historical biogeography and evolution of Brachyrhaphis fishes

The livebearing fish genus Brachyrhaphis (Poeciliidae) has become an increasingly important model in evolution and ecology research, yet the phylogeny of this group is not well understood, nor has it been examined thoroughly using modern phylogenetic methods. Here, we present the first comprehensive phylogenetic analysis of Brachyrhaphis by using four molecular markers (3mtDNA, 1nucDNA) to infer relationships among species in this genus. We tested the validity of this genus as a monophyletic group using extensive outgroup sampling based on recent phylogenetic hypotheses of Poeciliidae. We also tested the validity of recently described species of Brachyrhaphis that are part of the B. episcopi complex in Panama. Finally, we examined the impact of historical events on diversification of Brachyrhaphis, and made predictions regarding the role of different ecological environments on evolutionary diversification where known historical events apparently fail to explain speciation. Based on our results, we reject the monophyly of Brachyrhaphis, and question the validity of two recently described species (B. hessfeldi and B. roswithae). Historical biogeography of Brachyrhaphis generally agrees with patterns found in other freshwater taxa in Lower Central America, which show that geological barriers frequently predict speciation. Specifically, we find evidence in support of an ‘island’ model of Lower Central American formation, which posits that the nascent isthmus was partitioned by several marine connections before linking North and South America. In some cases where historic events (e.g., vicariance) fail to explain allopatric species breaks in Brachyrhaphis, ecological processes (e.g., divergent predation environments) offer additional insight into our understanding of phylogenetic diversification in this group.

Geographic Differentiation of Tree Ferns (Cyatheales) in Tropical America

Abstract The patterns of geographic differentiation in fern species have been linked to climatic differences across regions and the distribution of available habitat. In this paper, the association between some climatic features and patterns of geographic differentiation in American tree ferns was evaluated. For this, the occurrence ranges of 190 species were plotted and then analysed using track analysis. Here we identify six generalised tracks that span the main highland regions of tropical America: the Andes, the Guyana Highlands, the Brazilian Atlantic coast, lower Central America, the Greater Antilles, and upper Central America-Mexico. We did not find an association between cloud forest habitat and the differentiation pattern revealed by generalised tracks in Central America. Instead, these patterns are congruent with well-documented geological boundaries in the region. Climatic variables associated with cloud forest habitat were extracted from each generalised track and subjected to ANOVA, showing t...

Annotated checklist of the birds (Aves) of Cerro Hoya National Park, Azuero Peninsula, Panamá

Protected only by the extreme ruggedness of its terrain, the montane regions of Cerro Hoya National Park are among the least biologically known regions of Central America. Here we provide a checklist of 225 bird species recorded from five expeditions to the region over the last 18 years, which represents lower species richness than many comparable areas in Panama and lower Central America. However, we recorded nine IUCN globally threatened species, three species with range extensions over 150 km to the southern Azuero Peninsula, and at least two previously unknown bird taxa. These facts suggest that our list of montane taxa from Cerro Hoya may be incomplete, and that this region represents one of the most important—and neglected—protected areas in Panama.

PRE-COLUMBIAN “JADE”: TOWARDS AN IMPROVED IDENTIFICATION OF GREEN-COLORED STONE IN MESOAMERICA

The discovery of Pre-Columbian artifacts manufactured from green-colored stone is a noteworthy event within Mesoamerican archaeology, made even more significant as size and aesthetic value of the objects increase. Unfortunately, it is all too common that the color of such artifacts is used as a deciding factor in their identification and categorization. The lumping of green-colored artifacts into one category — that of “jade” or “greenstone” — is often the end of the material identification process, regardless of the fact that there are numerous different green-colored minerals found in different sources throughout Mesoamerica. The justification for merging these very different geological products stems from the fact that they were used in very similar ways throughout Mesoamerica and Lower Central America. However, the advent of portable techniques for elemental analysis has removed some of the difficulty and high costs that have traditionally inconvenienced the identification of green-colored artifacts, and can be used in combination with visual identification studies to improve accuracy of analyses.

Two new fringe-limbed frogs of the genus Ecnomiohyla (Anura: Hylidae) from Panama.

Forest canopy-dwelling frogs are usually among the rarest anuran species observed in the neotropical forest, mainly because they fall outside of the scope of the standard search methods used by herpetologists. During field explorations undertaken in western and eastern Panama in recent years, we discovered two species belonging to the genus Ecnomiohyla, which showed significant differences in genetic distances (16S mtDNA gene) and morphological characteristics different from any known Ecnomiohyla species. The first specimen originates from the Serranía de Jingurudó, Darién province, southeastern Panamá, and is described herein as E. bailarina sp. nov., and the second specimen was found at Santa Fe National Park, Veraguas province, central-western Panama, and is described as E. veraguensis sp. nov. We provide a detailed description of both new species, including comparisons of morphological and molecular characters of almost all members of the genus in lower Central America, as well as an identification key for the entire genus.

Rapid transformation of orchid floras

What does the future hold for the Orchidaceae? Historically the family has been quite plastic and responsive to large-scale habitat transformations, perhaps none so dramatic as the changes experienced during the formation of the cordilleras of the Northern Andes and lower Central America. Coupled with the backdrop of global fluctuations in climate, the rapid rise of these mountains over the last 0.5-2 M years have fragmented habitats and changed climate locally. These mountains are one of the most biologically diverse regions of the planet and may have served as a species pump for the Caribbean and other regions of Central and South America. The development of such diversity occurred over a scale of tens of millions of years to perhaps just a few thousand. While the same processes of the past are likely operational now, the current rate of habitat change may be unprecedented outside asteroid or major meteor impacts as global climate change accelerates, human- altered landscapes spread, and shifts occur in land use. We expect the structure and composition of orchid floras to change as populations respond evolutionarily through adaptation, extinctions and immigrations. Certainly the total destruction of a habitat, whether caused by volcanic eruptions or strip mining, is sure to have dire consequences but resiliency may occur if refugia serve as seed sources for colonization in the event of habitat recovery. As most orchids occupy ephemeral habitats or at least substrates, their natural population behavior likely entails cycles of local colonization and extinction as metapopulations. Another component of change is the increasing number of orchids that have become naturalized after human assisted dispersal (intentional or not). These alien orchids have overcome constraints imposed by pollination and mycorrhizal requirements. Will natural or human-assisted range expansions overcome extinction losses? Will they be among those that become the genetic material for a new wave of adaptive radiations? Much depends on population variation, patterns of gene flow, and rates of change. The Orchidaceae have had a history of ecological resiliency and evolutionary flexibility, which provides some degree of assurance. But this is no excuse for complacency since without some form of intervention the pace of change underway may be more than what orchid populations can overcome.

The influence of the complex topography and dynamic history of the montane Neotropics on the evolutionary differentiation of a cloud forest bird (Premnoplex brunnescens, Furnariidae)

AbstractAimTo examine the effect of geographical barriers and habitat dynamics related to climatic oscillations on the phylogeography of a widespread passerine of Neotropical cloud forests, the spotted barbtail (Premnoplex brunnescens).LocationNeotropical humid forests of montane areas in lower Central America and South America.MethodsWe sequenced two mitochondrial genes and one nuclear intron from specimens collected across the distribution of P. brunnescens. Phylogenetic relationships were inferred using Bayesian and maximum‐likelihood methods. Groups with maximum differentiation were estimated with spatial analysis of molecular variance (SAMOVA). We estimated timing of differentiation and relationships among groups with a species‐tree approach and historical demography with extended Bayesian skyline plots.ResultsSix highly differentiated clades of P. brunnescens are distributed in lower Central America, Sierra Nevada de Santa Marta, northern Venezuelan mountains, the Northern Andes, central Peru, and southern Peru and Bolivia. Within the Northern Andes clade, six phylogroups were identified associated with different slopes and isolated cordilleras. Most clades occupy opposite sides of low‐lying valleys and ridgelines, but little differentiation was observed across several putative barriers. Population divergence occurred in the late Miocene and Pliocene, perhaps in association with Andean uplift. Historical fluctuations in population sizes suggest that populations tracked the spatial dynamics of montane forests associated with glacial cycles.Main conclusionsExtensive genetic differentiation in mitochondrial and nuclear DNA exists among populations of P. brunnescens. Such marked divergence was probably promoted by the rugged topography and dynamic ecological history of the Neotropical mountains. Our study sheds light on mechanisms promoting population differentiation in the montane Neotropics.