Mexican Transition Zone Research Articles

First report of Trypanosoma microti in Cricetid rodents from Querétaro, Mexico: Expanding the known distribution of Herpetosoma in the Mexican transition zone

First report of Trypanosoma microti in Cricetid rodents from Querétaro, Mexico: Expanding the known distribution of Herpetosoma in the Mexican transition zone

Endemism and regionalization of Neotropical mammals: a multi-taxon analysis

Abstract The distribution pattern of a taxon is a consequence of historical and contemporary processes—specifically ecological and evolutionary processes—which tend to result in distributional congruence among species that respond similarly to the same processes. This congruence leads to the establishment of areas of endemism that are important for delimiting biogeographic regions. In the Neotropical region, different definitions of area of endemism have been proposed based on the distributional patterns of mammal species, each according to different methods and assumptions. In this study, we aimed to identify areas of endemism of Neotropical mammals, represented by 361 species of Placentalia (Xenarthra, Chiroptera, and Carnivora) and Marsupialia (Didelphimorphia and Paucituberculata), using an endemicity analysis implemented by the software NDM (eNDeMism software) and a hierarchical cluster analysis based on Simpson’s beta dissimilarity metric (βsim). The results suggest alternative spatial configurations within northern and southern parts of the Neotropics along transition zones. Additionally, there are indications of more restricted areas of endemism throughout the Neotropical region and with more species supporting the areas, such 1 area located in the region corresponding to the Atlantic forest and 2 areas corresponding to Mexican transition zone. The study enhances our understanding of Neotropical mammal biogeography and underscores the importance of using primary distribution data. Previous studies found 82 endemic species based on range maps, whereas our analyses identified 172 endemic species, including 125 that are newly proposed as such, and also confirmed the existence of 47 previously reported endemic species.

Species richness, geographic distribution and endemism of Pinguicula (Lentibulariaceae) in the Mexican Transition Zone

The genus Pinguicula (Lentibulariaceae) is composed of 115 species of carnivorous plants and Mexico is a center of diversification. The Mexican Transition Zone (MTZ) is the boundary between the Nearctic and Neotropical regions. It includes the main mountain ranges of Mexico, which extend south to northeastern Nicaragua. Its geological history, physiographic diversity and climatic complexity would have provided the environment to support a rich flora as well as angiosperm endemism. It was expected that the distribution of Pinguicula would have the same pattern. To test this hypothesis, a database was constructed based on the review of herbaria specimens, digital herbaria, bibliography, and databases. Species richness distribution and endemism were evaluated by country, biome, biogeographic province, elevation gradient, and three grid-cells sizes. The species richness of Pinguicula was centered in Mexico in an elevation gradient extending from 1,501–2,000 m. Also, species richness was greatest in the Tropical & Subtropical Coniferous Forest biome. However, considering biogeographic criteria, the Sierra Madre Oriental (SMOr) was the richest province. This was also supported by the distribution of the cells with the highest species richness and endemism. The results showed that the pattern of species richness and endemism of Pinguicula was concentrated along the MTZ, particularly in the SMOr.

Adaptive shifts in Phanaeini dung beetles of the Mexican plateau cenocron in the Mexican transition zone

Adaptive shifts in Phanaeini dung beetles of the Mexican plateau cenocron in the Mexican transition zone

Genomic diversity and structure of a Neotropical microendemic fig tree.

Genetic diversity is a key component of evolution, and unraveling factors that promote genetic differentiation in space and time is a central question in evolutionary biology. One of the most diverse and ecologically important tree genera in tropical forests worldwide is Ficus (Moraceae). It has been suggested that, given the great dispersal capacity of pollinating fig wasps (Chalcidoidea; Agaonidae), the spatial genetic structure, particularly in monoecious fig species, should be weak. However, no studies have addressed the factors that determine the genetic structure of Ficus species in regions of high geological, geographic, and climatic complexity, such as the Mexican Transition Zone. Using nuclear single nucleotide polymorphisms (5311 SNPs) derived from low-coverage whole genomes and 17 populations, we analyzed the population genomics of Ficus pringlei to characterize neutral and adaptive genetic variation and structure and its association with geographic barriers such as the Trans-Mexican Volcanic Belt, environmental heterogeneity, and wind connectivity. From genomic data of 71 individuals, high genetic diversity, and the identification of three genomic lineages were recorded (North, South, and Churumuco). The results suggest that genetic variation is primarily determined by climatic heterogeneity. Ficus pringlei populations from the north and south of the Trans-Mexican Volcanic Belt also exhibited minimal genetic differentiation (F ST = 0.021), indicating that this mountain range may not act as an insurmountable barrier to gene flow. Wind connectivity is also highlighted in structuring putative adaptive genetic variation, underscoring the intricate complexity of the various factors influencing genetic variation in the species. This study provides information on the possible mechanisms underlying the genetic variation of endemic species of the tropical dry forest of Western Mexico, such as F. pringlei.

Phylogenetic analyses of the subfamily Scarabaeinae (Coleoptera: Scarabaeidae) provide new insights into the Mexican Transition Zone theory.

Being areas of biotic overlap located between biogeographic regions, transition zones function as natural laboratories. The present study explores the phylogenetic history of the dung beetle subfamily Scarabaeinae, in order to present an evolutionary scenario that allows inference of the biogeographic history of the Mexican Transition Zone (MTZ) and integration of the distributional patterns of its biota. The species sampling included 94 New World taxa (93 species of Scarabaeinae and one species of Aphodiinae). The phylogenetic relationships of the main clades recovered in our study were supported with PP values 0.95. Based on the BAYAREALIKE model to reconstruct the ancestral distributional patterns of Scarabaeinae, we inferred a complex scenario with 19 dispersal events, 15 vicariance events, and three extinctions. We suggest that the Ancient Neotropical and Tropical Paleoamerican patterns represent the most likely ancestral distributional patterns for the Scarabaeinae of the MTZ, which probably settle there during the Eocene-Oligocene. The rest of the Scarabaeinae distributional patterns were assembled in subsequent periods. The results suggest that the MTZ had two separate formation stages: a Paleo-MTZ (Eocene-Miocene) and a current MTZ (Pliocene-Anthropocene). We conclude that the evolutionary history as well as the dispersal-vicariance scenario for the Scarabaeinae of the MTZ fits the out of the tropics model.

Thermal Tolerance of Honeybees (Apis mellifera L.) Changes Across an Elevation Gradient in the Mexican Transition Zone

The objective of this study was to determine the critical thermal minimum [CTmin], critical thermal maximum [CTmax], and thermal tolerance range of A. mellifera at three different elevations located in the Mexican Transition Zone: 11; 1,324, and 3,304 m.a.s.l. In general, we found that the CTmin of A. mellifera was lower at the site with the highest elevation (i.e., they tolerate colder temperatures). At the same time, the CTmax remained constant across the three studied elevations, revealing higher plasticity for cold tolerance rather than heat. Moreover, we did not find evidence that the body mass of the individuals was associated with their thermal tolerance at any of the three sampled elevations. Our findings suggest processes of local adaptation of A. mellifera populations in environmentally contrasting sites, allowing them to expand their range of distribution, which could be useful in predicting responses to future environmental change.

Niche conservatism and convergence in birds of three cenocrons in the Mexican Transition Zone.

The niche conservatism hypothesis postulates that physiological and phylogenetic factors constrain species distributions, creating richness hotspots with older lineages in ancestral climatic conditions. Conversely, niche convergence occurs when species successfully disperse to novel environments, diversifying and resulting in areas with high phylogenetic clustering and endemism, low diversity, and lower clade age. The Mexican Transition Zone exhibits both patterns as its biotic assembly resulted from successive dispersal events of different biotic elements called cenocrons. We test the hypothesis that biogeographic transitionallity in the area is a product of niche conservatism in the Nearctic and Typical Neotropical cenocrons and niche convergence in the Mountain Mesoamerican cenocron. We split the avifauna into three species sets representing cenocrons (sets of taxa that share the same biogeographic history, constituting an identifiable subset within a biota by their common biotic origin and evolutionary history). Then, we correlated richness, endemism, phylogenetic diversity, number of nodes, and crowning age with environmental and topographic variables. These correlations were then compared with the predictions of niche conservatism versus niche convergence. We also detected areas of higher species density in environmental space and interpreted them as an environmental transition zone where birds' niches converge. Our findings support the expected predictions on how niches evolved. Nearctic and Typical Neotropical species behaved as predicted by niche conservatism, whereas Mountain Mesoamerican species and the total of species correlations indicated niche convergence. We also detected distinct ecological and evolutionary characteristics of the cenocrons on a macroecological scale and the environmental conditions where the three cenocrons overlap in the Mesoamerican region.

New species of Centris (Xanthemisia) Moure from the Mesoamerican Dominion and the Mexican Transition Zone (Hymenoptera: Apidae).

Three new species of oil-collecting bees of the genus Centris (Xanthemisia) Moure are described and illustrated: C. jakalteka sp. nov., C. maya sp. nov. and C. purhepecha sp. nov. The new proposed taxa are distributed in the north of the Neotropical Region, specifically in the Mesoamerican Dominion and the Mexican Transition Zone, between the Neotropics and Nearctic. In addition, a distribution map and an identification key for the species of the subgenus occurring in the aforementioned regions are also presented.

New and previously known ectoparasitic monogenoids (Platyhelminthes) on native and non-native fishes from tributaries of the Usumacinta River basin (southern Mexico), a Neotropical transition zone

During a research on morphological diversity of gill ectoparasites on native and non-native fishes from tributaries (Palizada, El Recreo and Lacantún rivers) of the Usumacinta River Basin in the states of Campeche, Tabasco, and Chiapas (southern Mexico), the following monogenoids were found: Icelanonchohaptor tropicalis n. sp. on Usumacinta buffalo Ictiobus meridionalis (Günther, 1868) (Catostomidae); Heteropriapulus simplexiodes n. sp. and Heteropriapulus heterotylioides n. sp. on catfishes Pterygoplichthys pardalis (Castelnau, 1855) (Loricariidae) (type host) and Pterygoplichthys disyunctivus (Weber, 1991); Ligictaluridus mirabilis (Mueller 1937; Klassen and Beverley-Burton1985 from the southern blue catfish Ictalurus meridionalis (Günther, 1864) (Ictaluridae); Aristocleidus mexicanus Mendoza-Franco, Tapia and Caspeta-Mandujano, 2015 on Eugerres mexicanus (Steindachner, 1863) (Gerreidae) (all monogenoidean species in the Dactylogyridae); and Diplectanocotyla megalopis Rakotofiringa and Oliver1987 (Diplectanidae) on tarpon Megalops atlanticus Valenciennes, 1847 (Megalopidae). The new species of Icelanonchohaptor and Heteropriapulus are herein described for the first time from a native catostomid and non-native Pterygoplichthys spp., respectively. While I. tropicalis n. sp. and L. mirabilis are morphologically comparable with their congeners from the Nearctic (i.e., United States and Canada), all other monogenoids exhibited Neotropical affinities. Present study shown that the gill monogenoids on native and non-native fishes in the Neotropical Mexican transition zone of the Usumacinta River basin are equally represented by species with Nearctic and Neotropical affinities including those adapted to freshwater environment in this area from marine ancestry.

Richness and endemism in Chusquea subg. Swallenochloa (Poaceae), a Neotropical subgenus adapted to temperate conditions

Chusquea subg. Swallenochloa comprises 52 species distributed in five biogeographical areas (Mexican Transition Zone, Brazilian subregion, South American Transition Zone, Chacoan subregion, and Andean region). Species of the subgenus grow from almost sea level in the Andean region to almost 4000 m in the northern South American Transition Zone (SATZ) and are often common or dominant elements of the vegetation. In this study, three questions related to species richness, endemism, and risk category of Chusquea subg. Swallenochloa were addressed. Analyses were based on the geo-referenced occurrence data of these 52 species, using different methods and software programs. Results indicate that the Chacoan subregion and SATZ had the highest richness with 16 and 15 species, respectively. The area of highest endemism was found in the Brazilian subregion. The AOO and EOO methods provided strongly differing estimations of conservation status.

A new species and endemism of Tigridia (Tigridieae, Iridaceae) in the Transmexican Volcanic Belt, Mexico

The Transmexican Volcanic Belt (TVB) extends across Mexico from east to west between 18°30’ and 21°30’ latitudes. It is part of the Mexican Transition Zone consisting of several plateaus at different elevations and hundreds of volcanic structures. These have promoted diversification and endemism in several plant lineages. Here, Tigridia azufresensis is described as a new endemic species of the TVB. Morphologically, this taxon belongs to the Violacea complex and is similar to T. durangensis. Tigridia azufresensis differs from other species in its robust habit, and larger flowers. It has a cauline leaf subtending the rhipidium, so it appears to have three spathe valves. The flowers have elliptic to elliptic-lanceolate outer tepals and clawed inner tepals, which have a geniculate blade and a triangular apiculate limb. The TVB is rich in endemic species of Tigridieae: Tigridia azufresensis, T. flammea, T. gracielae, T. matudae, and T. venusta are exclusive to this biogeographical province.

Rearranging and completing the puzzle: Phylogenomic analysis of bark beetles Dendroctonus reveals new hypotheses about genus diversification

Studies carried out on bark beetles within Dendroctonus have been extensive and revealed diverse information in different areas of their natural history, taxonomy, evolution, and interactions, among others. Despite these efforts, phylogenetic hypotheses have remained obscured mainly due to limited information analyzed (taxonomic, gene sampling, or both) in studies focused on obtaining evolutionary hypotheses for this genus. With the aim of filling these gaps in the evolutionary history for Dendroctonus, we analyzed ∼1800 loci mapped to a reference genome obtained for 20 of the 21 species recognized to date, minimizing the impact of missing information and improving the assumption of orthology in a phylogenomic framework. We obtained congruent phylogenetic topologies from two phylogenomic inference strategies: loci concatenation (ML framework) and a multispecies coalescent model (MSC) through the analysis of site pattern frequencies (SNPs). Dendroctonus is composed of two major clades (A and B), each containing five and four subclades, respectively. According to our divergence dating analysis, the MRCA for Dendroctonus dates back to the early Eocene, while the MRCA for each major clade diverged in the mid-Eocene. Interestingly, most of the speciation events of extant species occurred during the Miocene, which could be correlated with the diversification of pine trees (Pinus). The MRCA for Dendroctonus inhabited large regions of North America, with all ancestors and descendants of clade A having diversified within this region. The Mexican Transition Zone is important in the diversification processes for the majority of clade A species. For clade B, we identified two important colonization events to the Old World from America: the first in the early Oligocene from the Arctic to Asia (via Beringia), and the second during the Miocene from the Arctic-Western-Alleghany region to Europe and Siberia (also via Beringia). Our genomic analyses also supported the existence of hidden structured lineages within the frontalis complex, and also that D. beckeri represent a lineage independent from D. valens, as previously suggested. The information presented here updates the knowledge concerning the diversification of a genus with remarkable ecological and economic importance.

Temperature dissimilarity drives flower–visitor interaction turnover across elevation in the Mexican Transition Zone

AbstractAimMost biodiversity studies have considered species to be isolated entities, neglecting the fact that their biotic interactions and spatial variation are fundamental to their persistence across elevational gradients. Here, using a standardized sampling methodology, we evaluated how and why the composition of flower–visitor interactions (i.e. beta diversity) varies over an extensive elevational gradient. Specifically, we aimed to identify which biotic (species turnover) and abiotic factors (temperature, precipitation and primary productivity) inherent to elevational gradients can explain the distribution of floral visitor–plant interactions.LocationMexican Transition Zone.TaxonAngiosperms, Hymenoptera, Lepidoptera, Diptera, Hemiptera and Coleoptera.MethodsWe sampled ecological interactions between floral visitors and flowering plants at 10 sites along an elevational gradient from 4 to 3425 m.a.s.l. We measured the additive partitioning of the beta diversity of species interactions and used generalized dissimilarity modelling to assess how spatial and environmental factors can explain the observed dissimilarity.ResultsWe found that the composition of interactions between floral visitors and plant species differs from lowlands to highlands mainly due to differences in temperature across the studied elevation gradient, rather than geographical distance or other environmental factors (i.e. mean annual precipitation and net primary productivity). We also observed that the main component of the beta diversity of interactions was interaction turnover driven by the turnover of both plants and floral visitors along the elevation gradient studied, which may be influenced by both temperature and the biogeographical affinity of biotas.Main ConclusionsWe conclude that environmental filters play a crucial role in the establishment of novel interactions, as temperature can filter species and impact the behaviour and traits of floral visitors and plants across an elevational gradient. These findings underscore the importance of considering the role of abiotic factors in predicting and explaining the distribution of species interactions across different elevational gradients.

Plastome phylogenomics reveals an early Pliocene North- and Central America colonization by long-distance dispersal from South America of a highly diverse bromeliad lineage.

Understanding the spatial and temporal frameworks of species diversification is fundamental in evolutionary biology. Assessing the geographic origin and dispersal history of highly diverse lineages of rapid diversification can be hindered by the lack of appropriately sampled, resolved, and strongly supported phylogenetic contexts. The use of currently available cost-efficient sequencing strategies allows for the generation of a substantial amount of sequence data for dense taxonomic samplings, which together with well-curated geographic information and biogeographic models allow us to formally test the mode and tempo of dispersal events occurring in quick succession. Here, we assess the spatial and temporal frameworks for the origin and dispersal history of the expanded clade K, a highly diverse Tillandsia subgenus Tillandsia (Bromeliaceae, Poales) lineage hypothesized to have undergone a rapid radiation across the Neotropics. We assembled full plastomes from Hyb-Seq data for a dense taxon sampling of the expanded clade K plus a careful selection of outgroup species and used them to estimate a time- calibrated phylogenetic framework. This dated phylogenetic hypothesis was then used to perform biogeographic model tests and ancestral area reconstructions based on a comprehensive compilation of geographic information. The expanded clade K colonized North and Central America, specifically the Mexican transition zone and the Mesoamerican dominion, by long-distance dispersal from South America at least 4.86 Mya, when most of the Mexican highlands were already formed. Several dispersal events occurred subsequently northward to the southern Nearctic region, eastward to the Caribbean, and southward to the Pacific dominion during the last 2.8 Mya, a period characterized by pronounced climate fluctuations, derived from glacial-interglacial climate oscillations, and substantial volcanic activity, mainly in the Trans-Mexican Volcanic Belt. Our taxon sampling design allowed us to calibrate for the first time several nodes, not only within the expanded clade K focal group but also in other Tillandsioideae lineages. We expect that this dated phylogenetic framework will facilitate future macroevolutionary studies and provide reference age estimates to perform secondary calibrations for other Tillandsioideae lineages.

Sixty years of Halffter’s Mexican Transition Zone: a systematic review using bibliometric tools

The Mexican Transition Zone (MTZ) has become a key concept that has promoted the consolidation of an integrative field of research. We reviewed the scientific publications on the MTZ with bibliometric tools to detect trends through time and analyze the conceptual structure and historiographic citation. We also performed a content analysis considering the conceptualization of the MTZ, the application of Halffter’s patterns of distribution, and the different disciplines where the term has been used. The number of publications per year has not been constant, but since 2012 there has been a general increase, becoming the MTZ frequently cited in papers and in some cases constituting a research topic. We identified divergences in the conceptualization of the MTZ and discussed the implications for biogeographic studies. Halffter’s conceptualization of the Mexican Transition Zone has inspired other authors to produce research focused on this area and to set biogeographic hypotheses but also to redefine the concept and make it applicable through its incorporation in the biogeographical regionalization of the Americas.

Diversity of the Pteridoflora of Montane Northwestern Mexico

This study compiles and updates the checklist of ferns and lycophytes from the Sierra Madre Occidental (SMOc). For this, we revised information on these taxa from regional floristic studies, databases, and herbaria. Our updated list includes 312 species, of which 276 are ferns and 36 are lycophytes integrated into 27 families and 75 genera. The richest families are Pteridaceae (118), Polypodiaceae (31), Selaginellaceae (30), Aspleniaceae (25), and Dryopteridaceae (25). The three most diverse genera were Selaginella (30), Asplenium (25), and Myriopteris (22). The species-rich Mexican states that include the SMOc are Durango (166 species), Chihuahua (149), and Jalisco (146). As in other tropical mountains, species richness in the SMOc is concentrated at the elevation interval of 1500 to 2000 m (236 species). The mid-mountain vegetation forests (Quercus and Pinus-Quercus forests) harbor the most pteridoflora richness (52% of the species). Four species of ferns are listed as threatened in the Mexican Official Norm NOM-059-SEMARNAT-2010, 17 species are listed in the IUCN, and only one tree ferns are in CITES. The SMOc has a Nearctic affinity, and its fern and lycophyte diversity are lower than in other Mexican Transition Zone mountain chains, such as the Sierra Madre del Sur, the Trans-Mexican Volcanic Belt, and the Sierra Madre Oriental. Notwithstanding, its biological composition is unique and distinctive. The species number reported in the SMOc represents 31% of the pteridoflora diversity recorded in Mexico.

Distribution, Regionalization, and Diversity of the dung beetle genus Phanaeus MacLeay (Coleoptera: Scarabaeidae) using Species Distribution Models

The genus Phanaeus is a well-known group whose taxonomy has been described multiple times. Its distribution was previously classified into 11 ecogeographic groups that are equivalent to areas of endemism. Here we use Species Distribution Models to describe species richness patterns. We measured beta-diversity and regionalized its distribution into one region and one transition zone, both with three dominions: Mexican Transition Zone (North American, Mexican, and Mesoamerican dominions) and Neotropical region (Pacific, Brazilian, and Atlantic Forest dominions). We also present a species checklist and updated the distribution maps for 73 of 81 species described so far that reflects all the taxonomical updates. We include a list of all the recorded locations (by country, state, and province), list the recorded habitats and biomes, and describe the modelled environmental conditions for each species.

Distribution of Phloeosinus tacubayae Hopkins, 1905 (Curculionidae, Scolytinae), the Cypress Bark Beetle, and new records from potential distribution models

We evaluated the biotic and abiotic conditions related to the presence of Phloeosinus tacubayae Hopkins, 1905, to update its distribution and explore new areas to collect the species from potential distribution models and establish its host range. Our results support that P. tacubayae is an oligophagous species distributed mostly in five provinces from the Mexican Transition Zone; its distribution pattern belongs to the Nearctic cenocron and is related to the distribution pattern of its principal host. The modeling and distribution of its hosts suggest invadable zones where new records may exist.

Spatial distribution of species richness and endemism of Solanum (Solanaceae) in Mexico

The spatial distribution of the species richness is not aleatory. It responds to evolutionary, geographical, and climatic events, and it is important to establish biodiversity management and conservation priorities. The mountainous zones around the globe have been identified as centers of plant diversification. In Mexico, the Mexican Transition Zone (MTZ) which comprises the main mountainous chains is recognized as an area of high species richness and endemism. The genus Solanum (Solanaceae) includes 1228 accepted species distributed all over the world, but with centers of species richness and endemism in the neotropical mountains. Based on patterns observed in geographical distribution of Mexican biodiversity, we expect the MTZ to host the highest species richness and endemism of Solanum. Here, we evaluated the spatial distribution of the species richness and endemism of Solanum in Mexico. For that purpose, we used 10043 unique georeferenced records obtained from herbarium specimens, specimens cited in literature and electronic databases. Then, we quantified species richness and endemism using biogeographical regions and provinces, a grid-cell of 50 × 50 km, political division, vegetation types, elevational, latitudinal, as well as longitudinal gradients. In addition, we analyzed endemism through weighted endemism and corrected weighted endemism. In Mexico, there were 134 species of Solanum including 43 endemics. The species richness and endemism were concentrated along the MTZ, specifically in the Chiapas Highlands, Sierra Madre del Sur (SMS), and Transmexican Volcanic Belt (TVB). Eight cells containing 63.43% of the species were obtained in the grid-cell analysis. The species richness distribution assessment by vegetation type, elevation, and political division confirmed the MTZ as the richest region. Likewise, the endemism was found along the MTZ in the Sierra Madre Oriental, SMS, TVB as well as in Chihuahuan Desert. Complex geological and paleoclimatic history, irregular topography, current climate diversity, dispersal, and persistence influenced these patterns. Lastly, we confirmed the remarkable importance of the MTZ as a center of origin, diversification and endemism of Mexican plants, using one of the most representative genera in Mexico.