Does the Trans‐mexican Volcanic Belt represent a natural biogeographical unit? An analysis of the distributional patterns of Coleoptera

Aim We analysed the geographical distribution of beetle species of the families Buprestidae, Cerambycidae, Dryophthoridae, Melolonthidae, Passalidae and Staphylinidae from the Trans‐mexican Volcanic Belt (TVB) through a track analysis and a parsimony analysis of endemicity (PAE), in order to test its naturalness and determine its affinities. Location The area analysed corresponds to the TVB, which is a biogeographical province of the Mexican Transition Zone. Methods The panbiogeographical analysis was based on the comparison of the individual tracks of 299 species of Buprestidae, Cerambycidae, Dryophthoridae, Melolonthidae, Passalidae and Staphylinidae (Coleoptera). The TVB was divided into 1^o × 1^o grid cells and we also included in the analysis the remaining Mexican biogeographical provinces. Parsimony analysis of endemicity with progressive character elimination (PAE‐PCE) was applied to classify areas by their shared taxa according to the most parsimonious cladograms. The nested sets of areas were represented as generalized tracks. Results Three generalized tracks were obtained: (1) grid cells 9C, 9D, 10D, 10E, Sierra Madre Oriental, Chiapas, Mexican Gulf and the Sierra Madre del Sur; (2) grid cells 3B, 3C, 4B, 4C, 5C, 6C, 7C, Sierra Madre Occidental, Sierra Madre del Sur, Balsas Basin and the Mexican Pacific Coast, and (3) grid cells 8D, 9C, 9D, 10D, 10E, Yucatán Peninsula, Chiapas, Sierra Madre Oriental and the Mexican Gulf. Main conclusions We conclude that the TVB does not represent a natural biogeographical unit because it shows different relationships with other biogeographical provinces, being clearly transitional between the Nearctic and Neotropical provinces. Some parts of the TVB are related to Neotropical provinces (Chiapas, Mexican Gulf and Mexican Pacific Coast) and others to the remaining provinces of the Mexican Transition Zone (Sierra Madre Oriental, Sierra Madre del Sur, Sierra Madre Occidental and Balsas Basin).     

Halffter's Mexican transition zone (1962–2014), cenocrons and evolutionary biogeography

The Mexican transition zone is the complex and varied area in which the Neotropical and Nearctic biotas overlap. In a series of contributions, Gonzalo Halffter provided a coherent theory that explains how sets of taxa that evolved in different geographical areas assembled in this transition zone. Halffter's theory developed gradually, being refined and clarified in successive contributions from him and other authors. After a review of the historical development of the Mexican transition zone, including the characterization of the dispersal or distributional patterns recognized by Halffter, its relevance for evolutionary biogeography is discussed briefly. The Mexican transition zone in the strict sense includes the highlands of Mexico and Guatemala (Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur and Chiapas Highlands provinces), whereas northern Mexico and the southern United States are clearly Nearctic, and the lowlands of southern Mexico and Central America are clearly Neotropical. The distributional patterns recognized by Halffter are considered to represent cenocrons (sets of taxa that share the same biogeographical history, constituting identifiable subsets within a biota by their common biotic origin and evolutionary history). The development of the Mexican transition zone is summarized into the following stages: (1) Jurassic–Cretaceous: the four Paleoamerican cenocrons extend in Mexico; (2) Late Cretaceous–Palaeocene: dispersal from South America of the Plateau cenocron; (3) Oligocene–Miocene: dispersal from the Central American Nucleus of the Mountain Mesoamerican cenocron; (4) Miocene–Pliocene: dispersal from North America of the Nearctic cenocron; and (5) Pleistocene: dispersal from South America of the Typical Neotropical cenocron.     

Phylogeography of the Buarremon brush-finch complex (Aves, Emberizidae) in Mesoamerica

The Buarremon brush-finches represent a complex suite of populations distributed in the montane New World Tropics from Mexico south to South America. Traditional taxonomic arrangements have separated populations of this genus into three species, based on plumage variation, although plumage patterns are well known to exhibit homoplasy. We present a first detailed phylogeographic and phylogenetic study, focused on Mesoamerican populations, and signal the existence of strong differentiation among populations with a clear geographic structure. We find well differentiated clades for (1) the Sierra Madre Oriental and Sierra Madre del Sur in Oaxaca, (2) western Mexican populations, including the B. brunneinucha populations in the Sierra Madre del Sur and B. virenticeps, (3) Sierra Madre Oriental and Sierra de los Tuxtlas, (4) northern Central America, (5) southern Central America, (6) middle Central America, and (7) South America. We demonstrate a lack of concordance with plumage patterns, and argue for several additional species to be recognized in the complex.     

The diversification of Nearctic mammals in the Mexican transition zone

The boundary between the Nearctic and Neotropical regions has been delineated using different approaches, methods and taxa. Using a panbiogeographical approach, identification of nodes can help understand the dynamics and evolution of the boundary. We analysed the distribution patterns of 46 Mexican land mammal species belonging to the Nearctic biotic component and delineated generalized tracks and nodes, in order to determine the southernmost boundary of the Nearctic region in Mexico. We found six generalized tracks and nine nodes; the latter located largely in the Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur and Chiapas biogeographical provinces. The highlands of Chiapas were found to represent the southernmost area inhabited by Nearctic taxa. The other biogeographical provinces, together with the Sierra Madre Occidental and Balsas Basin provinces, represent the Mexican transition zone in the strict sense. Instead of a classic static boundary, this transition zone represents an evolutionarily 'active' zone, where several speciation events have taken place in the past.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 327–339.     

Historical biogeography of the genus Rhadinaea (Squamata: Dipsadinae)

Multiple geological and climatic events have created geographical or ecological barriers associated with speciation events, playing a role in biological diversification in North and Central America. Here, we evaluate the influence of the Neogene and Quaternary geological events, as well as the climatic changes in the diversification of the colubrid snake genus Rhadinaea using molecular dating and ancestral area reconstruction. A multilocus sequence dataset was generated for 37 individuals of Rhadinaea from most of the biogeographical provinces where the genus is distributed, representing 19 of the 21 currently recognized species, and two undescribed species. Our analyses show that the majority of the Rhadinaea species nest in two main clades, herein identified as “Eastern” and “Southern”. These clades probably diverged from each other in the early Miocene, and their divergence was followed by 11 divergences during the middle to late Miocene, three divergences during the Pliocene, and six divergences in the Pleistocene. The ancestral distribution of Rhadinaea was reconstructed across the Sierra Madre del Sur. Our phylogenetic analyses do not support the monophyly of Rhadinaea. The Miocene and Pliocene geomorphology, perhaps in conjunction with climate change, appears to have triggered the diversification of the genus, while the climatic changes during the Miocene probably induced the diversification of Rhadinaea in the Sierra Madre del Sur. Our analysis suggests that the uplifting of the Trans‐Mexican Volcanic Belt and Chiapan–Guatemalan highlands in this same period resulted in northward and southward colonization events. This was followed by more recent, independent colonization events in the Pliocene and Pleistocene involving the Balsas Basin, Chihuahuan Desert, Pacific Coast, Sierra Madre Occidental, Sierra Madre Oriental, Sierra Madre del Sur, Trans‐Mexican Volcanic Belt, and Veracruz provinces, probably driven by the climatic fluctuations of the time.     

Ephemeral Pleistocene woodlands connect the dots for highland rattlesnakes of the Crotalus intermedius group

Aim To test how Pleistocene climatic changes affected diversification of the Crotalus intermedius species complex. Location Highlands of Mexico and the south‐western United States (Arizona). Methods We synthesize the matrilineal genealogy based on 2406 base pairs of mitochondrial DNA sequences, fossil‐calibrated molecular dating, reconstruction of ancestral geographic ranges, and climate‐based modelling of species distributions to evaluate the history of female dispersion. Results The presently fragmented distribution of the C. intermedius group is the result of both Neogene vicariance and Pleistocene pine–oak habitat fragmentation. Most lineages appear to have a Quaternary origin. The Sierra Madre del Sur and northern Sierra Madre Oriental are likely to have been colonized during this time. Species distribution models for the Last Glacial Maximum predict expansions of suitable habitat for taxa in the southern Sierra Madre Occidental and northern Sierra Madre Oriental. Main conclusions Lineage diversification in the C. intermedius group is a consequence of Pleistocene climate cycling. Distribution models for two sister taxa in the northern and southern Sierra Madre Occidental and northern Sierra Madre Oriental during the Last Glacial Maximum provide evidence for the expansion of pine–oak habitat across the Central Mexican Plateau. Downward displacement and subsequent expansions of highland vegetation across Mexico during cooler glacial cycles may have allowed dispersal between highlands, which resulted in contact between previously isolated taxa and the colonization of new habitats.     

Do the Oaxacan Highlands represent a natural biotic unit? A cladistic biogeographical test based on vertebrate taxa

Aim  We analysed the distributional patterns of six terrestrial vertebrate taxa from the Oaxacan Highlands (Sierra Mazateca, Nudo de Zempoaltépetl and Sierra de Juárez) through a cladistic biogeographical approach, in order to test their naturalness as a biotic unit.
Location  The Oaxacan Highlands, Mexico.
Methods  The cladistic biogeographical analysis was based on the area cladograms of the Pseudoeurycea bellii species group (Amphibia: Plethodontidae), the genus Chlorospingus (Aves: Thraupidae), the genera Microtus , Reithrodontomys and Habromys , and the Peromyscus aztecus species group (Mammalia: Rodentia). We obtained paralogy-free subtrees, from which the components were coded in a data matrix for parsimony analysis. The data matrix was analysed with N ona through W in C lada .
Results  The parsimony analysis resulted in a single general area cladogram in which areas were fragmented following the sequence Sierra Madre Occidental, Trans-Mexican Volcanic Belt, Chiapas, Sierra Madre Oriental + Sierra Mazateca, Sierra Madre del Sur, Nudo de Zempoaltépetl and Sierra de Juárez.
Main conclusions  The general area cladogram shows that the Oaxacan Highlands do not constitute a natural unit. The Sierra Mazateca is the sister area to the Sierra Madre Oriental, whereas the Nudo de Zempoaltépetl and the Sierra de Juárez are closely related to the Sierra Madre del Sur. The events that might have caused these patterns include cycles of expansion and contraction of mountain pinyon, juniper and oak woodlands during the Pleistocene.     

Fundamental biogeographic patterns across the Mexican Transition Zone: an evolutionary approach

Transition zones, located at the boundaries between biogeographic regions, represent events of biotic hybridization, promoted by historical and ecological changes. They deserve special attention, because they represent areas of intense biotic interaction. In its more general sense, the Mexican Transition Zone is a complex and varied area where Neotropical and Nearctic biotas overlap, from southwestern USA to Mexico and part of Central America, extending south to the Nicaraguan lowlands. In recent years, panbiogeographic analyses have led to restriction of the Mexican Transition Zone to the montane areas of Mexico and to recognize five smaller biotic components within it. A cladistic biogeographic analysis challenged the hypothesis that this transition zone is biogeographically divided along a north‐south axis at the Transmexican Volcanic Belt, as the two major clades found divided Mexico in an east‐west axis. This implies that early Tertiary geological events leading to the convergence of Neotropical and Nearctic elements may be younger (Miocene) than those that led to the east‐west pattern (Paleocene). The Mexican Transition Zone consists of five biogeographic provinces: Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur, and Chiapas. Within this transition zone, at least four cenocrons have been identified: Paleoamerican, Nearctic, Montane Mesoamerican, and Tropical Mesoamerican. Future studies should continue refining the identification of cenocrons and the reconstruction of a geobiotic scenario, as well as integrating ecological biogeographic studies, to allow a more complete understanding of the patterns and processes that have caused the biotic complexity of this transition zone.     

Moss endemism in the Mexican flora

Although the moss flora of Mexico consists of nearly 1000 species, only 77 are endemic. The country has many poorly collected or unexplored areas, but the number of endemic mosses is not expected to undergo a substantial increase; percent endemism has in fact decreased with taxonomic revisions and monographs and better exploration in other countries. Literature and herbarium records (n?=?584) were used to obtain an updated list of endemic mosses and their state distribution in Mexico. Cluster analysis and mapping indicate that there are three main areas of endemism: Lowland areas in various states, the mountain area along 19–20°N lat., and the highlands in Oaxaca and Chiapas. Similarity by province shows that Trans-Mexican Volcanic Belt, Sierra Madre Oriental, Chihuahuan Desert, and Sierra Madre del Sur have the highest numbers of endemic species. Five monotypic genera and 76 species (including two infraspecific taxa), many of which have comparatively narrow geographical ranges, suggest that speciation is recent, that species have had little time to disperse, and were formed by Pleistocene environmental climates in the highlands; older speciation may be represented by widespread disjunct species that still are found in the highlands of Mexico.     

Biogeographical analysis of two Polypodium species complexes (Polypodiaceae) in Mexico and Central America

We analyzed the geographical and elevational distributions of two Polypodium complexes from Mexico and Central America. Distribution data of nine species of the Polypodium colpodes complex and the Polypodium plesiosorum complex were obtained from almost 1500 herbarium specimens, field collections in Mexico and Costa Rica, and literature studies. The presence of each species was recorded for each Mesoamerican country, in 1° × 1° grid‐cells and biogeographical provinces. The rarity of species was also evaluated. Although the two complexes show extensive overlap, the P. colpodes complex is distributed mainly along the Pacific versant of Mexico and Central America, whereas the P. plesiosorum complex occurs mainly along the Atlantic versant. Those biogeographical provinces with maximum species diversity are Chiapas (seven species), Sierra Madre del Sur (six species), and the Trans‐Mexican Volcanic belt (six species). Grid‐cells with more species are located mainly in the mountains of central‐southern Mexico and northern Central America. Richness does not decrease or increase with latitude. Elevation distributions showed that most Polypodium species are concentrated in the montane interval and three species groups were recognized based on elevational preferences. Polypodium colpodes and P. plesiosorum are the most widely distributed species, whereas Polypodium castaneum and Polypodium flagellare are the only two species that possess the three attributes of rarity (narrow geographical distribution, high habitat specificity, and scarce local populations). Polypodium species of both complexes are present mainly in the montane regions of the study area and show some degree of geographical sympatry, especially in southern Mexico and northern Central America. This overlapping is explained by the elevation tolerance within montane systems and because most species inhabit three or more vegetation types. The distributional patterns of these complexes coincided with the three regional highlands of Mesoamerica, which are separated from each other by the Isthmus of Tehuantepec and by the lowlands of Nicaragua. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Genetic variation coincides with geographic structure in the common bush-tanager (Chlorospingus ophthalmicus) complex from Mexico

Cloud forests are distributed in the Neotropics, from northern Mexico to Argentina, under very specific ecological conditions, namely slopes with high humidity input from clouds and mist. Its distribution in Mesoamerica is highly fragmented, similar to an archipelago, and taxa are thus frequently represented as sets of isolated populations, each restricted to particular mountain ranges and often showing a high degree of divergence, both morphologically and genetically. The common bush-tanager (Chlorospingus ophthalmicus, Aves: Thraupidae) inhabits cloud forests from eastern and southern Mexico south to northwestern Argentina. Here we use 676bp of mtDNA (around the ATPase 8 gene) to explore the genetic variation and phylogeographic structure of the Mexican populations of C. ophthalmicus. Phylogenetic analyses of mtDNA sequences indicate deep genetic structure. Five major clades, which segregate according to geographic breaks, are identified (starting from the deepest one in the phylogeny): (1) Southern Chiapas and Northern Central America, (2) Tuxtlas massif, (3) Sierra Madre del Sur, (4) Eastern Oaxaca and Northern Chiapas, and (5) Sierra Madre Oriental. The long history of isolation undergone by each clade, as suggested by the phylogeny, implies that the species status of each of them should be revised.     

Do fleas (Insecta: Siphonaptera) parallel their mammal host diversification in the Mexican transition zone?

Aim The Mexican transition zone is a complex area where Neotropical and Nearctic biotic elements overlap. A previous study on mammal species has shown a great diversification in the area. We analyse the diversification of their flea species (Insecta: Siphonaptera), in order to determine if a diversification similar to their mammal host species has occurred. Location The area analysed corresponds to Mexico. Methods The panbiogeographical or track analysis was based on the comparison of the individual tracks of 112 species belonging to 48 genera and eight families of the order Siphonaptera. Generalized tracks were obtained based on the comparison of the individual tracks. Nodes were found in the areas where generalized tracks overlapped. Results Thirty‐four generalized tracks were obtained, distributed within the Mexican transition zone (20), the Nearctic region plus the Mexican transition zone (8), the Nearctic region (4) and the Neotropical region plus the Mexican transition zone (2). In the areas where they intersected, 26 nodes were identified: 23 in the Mexican transition zone and 3 in the Nearctic region. Main conclusions The nodes are concentrated in the Transmexican Volcanic Belt (14), Sierra Madre Oriental (5) and Sierra Madre del Sur (4) provinces of the Mexican transition zone. These results show a significant diversification of the flea taxa, in parallel with the diversification of their mammal hosts.     

A new genus and eight new species of the subtribe Anillina (Carabidae,Trechinae, Bembidiini) from Mexico,with a cladistic analysis and some notes on?the?evolution of the genus

One new genus and eight new species of anilline carabids are described from southern Mexico. The new genus, Zapotecanillus gen. n., is established for Z. oaxacanus (type species) sp. n., Z. nanus sp. n., Z. iviei sp. n., Z. ixtlanus sp. n., Z. montanus sp. n., and Z. kavanaughi sp. n. from the Sierra Madre de Oaxaca, Z. pecki sp. n. from the Sierra Madre del Sur, and Z. longinoi sp. n. from the Sierra Madre de Chiapas. A taxonomic key for all described species of Zapotecanillus and a cladistic analysis, based on morphological data, are provided. Morphological, behavioral and biogeographical aspects of the speciation in the genus obtained from the resulting cladogram are discussed.     

A new species of solanum section geminata (Solanaceae) from western Mexico

Solanum malacothrix S. Knapp is described from the slopes of the Sierra Madre del Sur in the Río Balsas drainage in the state of Guerrero. It is apparently rare, and has been collected only twice. Its relationship to other species in Mexico and northern South America is discussed.     

Track analysis of the Nearctic region: Identifying complex areas with mammals

The Nearctic region is located on the North American plate. However, its tectonic history is related to convergence with other plates, which has promoted a complex topography. This complexity should be reflected by the distributional patterns of the biota. We used track analysis with 574 species of mammals to identify generalized tracks and panbiogeographic nodes in the Nearctic region and to propose an updated point of view of complex areas and their boundaries in North America. Seven generalized tracks with nested patterns (California, Columbia Plateau, Mesoamerican, Mexican Plateau, Neotropic, Southern Rocky Mountains, and Western Coast of USA) were identified using a parsimony analysis of endemicity with progressive character elimination. Nine panbiogeographic nodes were identified at the intersections of the generalized tracks, all of which were located in the Sierra of Chiapas and Central America physical features. A total of 192 nodes were identified for the nested patterns, located in only eight physical features. Our analysis revealed evolutionary patterns in generalized tracks, and the panbiogeographic nodes predicted areas with high evolutionary–geologic complexity, shared by other taxonomic groups.     

Phylogeography of the bark beetle Dendroctonus mexicanus Hopkins (Coleoptera: Curculionidae: Scolytinae)

Dendroctonus mexicanus is polyphagous within the Pinus genus and has a wide geographical distribution in Mexico and Guatemala. We examined the pattern of genetic variation across the range of this species to explore its demographic history and its phylogeographic pattern. Analysis of the mtDNA sequences of 173 individuals from 25 Mexican populations allowed to us identify 53 geographically structured haplotypes. High haplotype and low nucleotide diversities and Tajima’s D indicate that D. mexicanus experienced rapid population expansion during its dispersal across mountain systems within its current range. The nested clade phylogeographic analysis indicates that the phylogeographic pattern of D. mexicanus is explained by continuous dispersion among lineages from the Sierra Madre Occidental, the Sierra Madre Oriental and the Trans-Mexican Volcanic Belt. However, we also observed isolation events among haplotypes from the Cofre de Perote/Trans-Mexican Volcanic Belt/Sierra Madre Oriental and the Trans-Mexican Volcanic Belt/Sierra Madre del Sur, which is consistent with the present conformation of mountain systems in Mexico and the emergence of geographical barriers during the Pleistocene.     

Cladistic biogeography of the Mexican transition zone

Biogeographic relationships among nine montane areas of endemism across the transition zone between North and South America are analysed cladistically based on phylogenetic hypotheses of thirty‐three resident monophyletic taxa of insects, fish, reptiles, and plants. Areas of endemism include the Arizona mountains (AZ), Sonoran Desert (SD), Sierra Madre Occidental (OCC), southern Sierra Madre Occidental (SOC), Sierra Madre Oriental (ORI), Sierra Transvolcanica (TRAN), Sierra Madre del Sur (SUR), Chiapan‐Guatemalan Highlands (CGH), and Talamancan Cordillera (TC). Area relationships are summarized using Brooks Parsimony Analysis and Assumption 0, with the former resulting in more defensible biogeographic hypotheses. Areas of endemism are dividable into two monophyletic groups; a northern group including AZ, SD, OCC, and ORI, and a southern group consisting of TC, CGH, TRAN, SUR, and the isolated southern regions of the Sierra Madre Occidental (SOC). The northern set of areas are characterized by recent, probably Pleistocene, isolation and prevalent widespread species, whereas the southerly areas probably diverged after Pliocene closure of the Panamanian isthmus. The southern areas are redundantly represented on many of the taxon‐area cladograms by endemic species, indicative of much higher levels of endemism in the Sierra Transvolcanica and further south. Use of a general area cladogram in such a transition zone permits explicit exploration of biogeographic patterns and establishes a predictive framework for taxonomy and conservation prioritization.     

A new species of the Phanaeus endymion species group (Coleoptera: Scarabaeidae: Scarabaeinae), with comments on ecology and distribution

Phanaeus edmondsi n. sp. is described from the tropical forest of La Sierra Madre del Sur, estado de Oaxaca, Mexico. The new species belongs to the P. endymion species group. Distributional and ecological information of the new and allied species is included. A modification to update the identification key for related species is presented.     

Two new species of oak (Fagaceae, Quercus sect. Lobatae) from the Sierra Madre del Sur, Mexico

Two new species of oak (Fagaceae) with narrowly ellipticlanceolate leaves from the Sierra Madre del Sur of western Jalisco, Mexico, are described and illustrated.Quercus cualensis is a local endemic andQ. iltisii a more widespread species; they are closely related toQ. salicifolia Née.     

Phylogeny of the Pantomorus–Naupactus complex based on morphological and molecular data (Coleoptera: Curculionidae)

The Pantomorus–Naupactus complex is a Neotropical group of broad‐nosed weevils (Coleoptera: Curculionidae) including several parthenogenetic species usually assigned to the genera Naupactus Dejean, Pantomorus Schoenherr, Asynonychus Crotch, Aramigus Horn, Eurymetopus Schoenherr and Graphognathus Buchanan. Sixteen species were studied to test hypotheses on the monophyly of these genera, and on the origin of the parthenogenetic lineages. A matrix of 30 morphological characters and 999 positions of the Cytochrome Oxidase I gene, was analyzed with separate partitions and simultaneously, under equal and implied weights, and with different transversion/transitions costs. The ILD test indicates that the incongruence between the molecular and morphological data is not significant. Under equal weights, the molecular data resulted in a single tree and morphology in 34 trees; under implied weights morphology gave a different tree, and under TV:TS ≥ 4:1 molecular and combined analyses resulted in the same optimal tree. According to the latter, Naupactus includes Graphognathus, and is thus paraphyletic and basal regarding remaining genera, Pantomorus is polyphyletic and includes Aramigus and Asynonychus, and Eurymetopus is monophyletic. The species in which apomictic parthenogenesis has been verified (Aramigus tessellatus, Asynonychus cervinus and Graphognathus lecuoloma), belong to different clades of the Pantomorus‐Naupactus complex, with basal sexual relatives. © The Willi Hennig Society 2005.