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Phylogeography supports lineage divergence for an endemic rattlesnake (Crotalus ravus) of the Neotropical montane forest in the Trans-Mexican Volcanic Belt

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Abstract

The formation of the Trans-Mexican Volcanic Belt (TMVB) and Pleistocene climatic fluctuations have been shown to influence the diversification of lineages and species distributed throughout central Mexico. In some taxa, however, evidence of lineage diversification is not easily recognized, as often is the case in reptiles. Here we present a phylogeographic study on a Mexican endemic rattlesnake species (Crotalus ravus), with the aim of understanding how distinct lineages are distributed across the TMVB. Genetic (mtDNA) and genomic (ddRADseq) data were generated from samples across the species' range to evaluate phylogeographic structure, estimate phylogenetic relationships and divergence times, and perform environmental niche modeling (ENM). Both datasets recover strong phylogeographic structuring of two distinct lineages on an east-west axis, with an estimated Pleistocene divergence (~1.47 Myr). The ENM suggest that the distribution of the two lineages experienced expansion and reduction events throughout recent evolutionary time. We attribute the diversification of C. ravus lineages to geological events associated with the formation of the TMVB, as well as Quaternary climate changes, both of which have been previously recognized in co-distributed taxa in the TMVB. This work emphasizes the existence of cryptic diversification processes in a morphologically conserved species distributed in a region of complex climatic and orogenic heterogeneity. ADDITIONAL KEYWORDS: endemism-mtDNA-phylogepography-snake-SNPs-TMVB.

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Plants respond to Pleistocene climatic change as species, not as associations or biomes. This has been demonstrated unequivocally by paleobotanical data for temperate latitudes. In the far richer vegetations of the tropics species populations also #uctuated independently in response to climatic forcing, from their longlasting glacial states to the patterns of brief interglacials like the present and back again. We use pollen data to reconstruct the vegetation of the Amazon basin in oxygen isotope stages 3 and 2 of the last glaciation in order to measure how the plant populations of the Amazon responded to the global warming at the onset of the Holocene. We "nd that plant communities of the neotropics vent copious pollen to lake sediments and that this pollen yields powerful signals for community composition. Three continuous sedimentary records reaching through oxygen isotope stage 2 are available from the Amazon lowlands, those from Carajas, Lake Pata and marine deposits o! the mouth of the Amazon River. All three records yield pollen histories of remarkable constancy and stability. By comparing them with deposits of equal antiquity from the cerrado (savanna) of central Brazil, we show that most of the Amazon lowlands remained under forest throughout a glacial cycle. This forest was never fragmented by open vegetation as postulated by the refugia hypothesis. Instead the intact forest of glacial times included signi"cant populations of plants that are now montane, suggesting that the global warming of the early Holocene resulted in the expulsion of heat intolerant plants from the lowland forest. Pollen data from the Amazonian #ank of the Andes and from Paci"c Panama provide evidence that populations of these heat intolerant plants survive the heat of interglacials in part by maintaining large populations at cooler montane altitudes. Our conclusion that the Amazon lowlands were forested in glacial times speci"cally refutes the hypothesis of Amazonian glacial aridity. Accordingly we examine the geomorphological evidence for glacial aridity and "nd it wanting. Of the three paleodune systems reported for tropical South America, that of NE Brazil was active in the Holocene as well as the Pleistocene. Parts of NE Brazil were actually moister than now in late-glacial times. Paleodunes in the Pantanal have never been seen on the ground, and those in the Orinoco Llanos are undated and may be of any age since the Tertiary. Arkosic sands in the Amazon fan deposits came from the Andean foothills or from down cutting by rivers and cannot be evidence of a former arid land surface. White sands of Amazonia formed as podzols, not by aeolian activity. Such Amazonian stone lines as have received critical scrutiny are concretionary pisolites in stratigraphic formations that are more than ten million years old. Although the Amazon was never arid, modeling cooler glacial tropics gives plausibility to a somewhat drier Amazon in glacial times, a concept given substance by pollen data for the movement of ecotones in Rondonia, by stream histories in the Bolivian Andes, and by evidence for lowered lake levels at Carajas and Lake Pata. But this reduced precipitation was never enough to fragment the forest in the Amazon lowlands themselves. Pleistocene mammals of the Napo river valley in Ecuador were able to live along the river system in a forested landscape. Our data suggest that the Amazon forests have been stable since the start of the Pleistocene, a fact that has contributed to the storage of vast diversity. The coming anthropogenic global warming and CO enrichment will add to the global warming already endured by Amazon biota in the Holocene. We think it possible that the expulsion from the lowland forests of heat intolerant species is already complete and that the forest property of maintaining its own microhabitat will allow the high species richness to survive more global warming, provided large enough tracts of forest are preserved.
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As DNA sequencing technologies and methods for delimiting species with genomic data become more accessible and numerous, researchers have more tools than ever to investigate questions in systematics and phylogeography. However, easy access to sophisticated computational tools is not without its drawbacks. Choosing the right approach for one's question can be challenging when presented with multitudinous options, some of which fail to distinguish between species and intraspecific population structure. Here, we employ a methodology that emphasizes intensive geographic sampling, particularly at contact zones between populations, with a focus on differentiating intraspecific genetic clusters from species in the Pantherophis guttatus complex, a group of North American ratsnakes. Using a mitochondrial marker as well as ddRADseq data, we find evidence of mitonuclear discordance which has contributed to historical confusion about the relationships within this group. Additionally, we identify geographically and genetically structured populations within the species Pantherophis emoryi that are congruent with previously described morphological variation. Importantly, we find that these structured populations within P. emoryi are highly admixed throughout the range of the species and show no evidence of any reproductive isolation. Our data support a revision of the taxonomy of this group, and we recognize two species within the complex and three subspecies within P. emoryi. This study illustrates the importance of thorough sampling of contact zones and consideration of gene flow when delimiting species in widespread complexes containing parapatric lineages.
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We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
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Snakes of the cosmopolitan family Viperidae comprise around 329 venomous species showing a striking heterogeneity in species richness among lineages. While the subfamily Azemiopinae comprises only two species, 70% of all viper species are arranged in the subfamily Crotalinae or the "pit vipers". The radiation of the pit vipers was marked by the evolution of the heat-sensing pits, which has been suggested to be a key innovation for the successful diversification of the group. Additionally, only crotalines were able to successfully colonize the New World. Here, we present the most complete molecular phylogeny for the family to date that comprises sequences from nuclear and mitochondrial genes representing 79% of all living vipers. We also investigated the time of divergence between lineages, using six fossils to calibrate the tree, and explored the hypothesis that crotalines have undergone an explosive radiation. Our phylogenetic analyses retrieved high support values for the monophyly of the family Viperidae, subfamilies Viperinae and Crotalinae, and 22 out of 27 genera, as well as well-supported intergeneric relationships throughout the family. We were able to recover a strongly supported sister clade to the New World pit vipers that comprises Gloydius, Ovophis, Protobothrops and Trimeresurus gracilis. Our results agree in many aspects with other studies focusing on phylogenetics of vipers, but we also recover new relationships as well. Despite the addition of new sequences we were not able to resolve some of the poor supported relationships previously suggested. Time of divergence estimates suggested that vipers started to radiate around the late Paleocene to middle Eocene with subfamilies most likely dating back to the Eocene. The invasion of the New World might have taken place sometime close to the Oligocene/Miocene boundary. Diversification analyses suggested a shift in speciation rates during the radiation of a sub-clade of pit vipers where speciation rates rapidly increased but slowed down toward the present. Thus, the evolution of the loreal pits alone does not seem to explain their explosive speciation rates. We suggest that climatic and geological changes in Asia and the invasion of the New World may have also contributed to the speciation shift found in vipers.
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The Mexican glacial chronology is based on morphostratigraphy, tephrochronology, 14C and cosmogenic 36Cl exposure ages. Glaciers formed moraines during MIS 6, between 21-17.5, 17-14, 14-13, 12-10 and 8.3-7ka BP. ELA depressions for the five late Quaternary advances were 1030, 930, 730, 550 and 250m, respectively. A temperature decrease of 5-9°C supports marked cooling over tropical land and oceans during the last glacial maximum. Evidence does not indicate glacier expansion during, but rather immediately after, the Younger Dryas and during the 8.2ka event. Little Ice Age cooling is documented by distinctive moraines.
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Pollen profiles, mammalian macrofossils, packrat middens and extinct glaciers suggest that timberlines descended c1000m during the Wisconsin glacial in Mexico. Two closely situated subregions of alpine vegetation would have developed in NE Mexico, contrasting with the present-day, highly restricted distribution of seven disjunct refugia. The southern subregion would have centered around the present-day timberline refugium of Sierra Pena Nevada, Tamaulipas, and the northern subregion would have extended from the south of Cerro Potosi to Sierra la Viga, Nuevo Leon, linking in a continuous distribution the five most northerly alpine refugia of northeastern Mexico. -from Author
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Aim (1) To synthesize data on the physical and phylogeographical history of the Mexican highlands, with a focus on the Trans-Mexican Volcanic Belt (TMVB), and (2) to propose approaches and analyses needed for examining the interaction of climate and volcanism. Location Mexico. Methods We performed a literature and data survey of the climatic, geological and phylogeographical history of the Mexican highlands. We then assessed how the expected effects of topographic isolation, co-occurring palaeoclimatic fluctuations and volcanism can be tested against the distribution of genetic diversity of high-elevation taxa. Results The Mexican highlands present a complex biogeographical, climatic and geological history. Montane taxa have been exposed to a sky-island dynamic through climate fluctuations, allowing for long-term in situ population persistence, while also promoting recent divergence and speciation events. Volcanic activity transformed part of the Mexican highlands during the Pleistocene, mainly in the TMVB, leading to co-occurring climate and topographical changes. The TMVB highlands provide a suitable template to examine how low-latitude mountains can facilitate both the long-term persistence of biodiversity as well as allopatric and parapatric speciation driven by climatic and geological events. Main conclusions Climate fluctuations, together with recent volcanism, have driven the diversification and local persistence of biodiversity within the Mexican highlands. The climate–volcanism interaction is challenging to study; however, this can be overcome by coupling genomic data with landscape analyses that integrate the geological and climatic history of the region.
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AimWe tested whether populations of violet-crowned and green-fronted hummingbirds, Amazilia violiceps and Amazilia viridifrons, are genetically and environmentally differentiated, and examined the role of past geological and climatic changes in driving their diversification.LocationTrans-Mexican Volcanic Belt.Methods Mitochondrial and nuclear DNA of individuals collected throughout the species' ranges were sequenced and then analysed using maximum-likelihood and Bayesian approaches. Species tree analysis, Bayesian species delimitation, divergence time inference, historical demography, palaeodistribution modelling, and niche divergence tests were used to reconstruct the evolutionary history of the Amazilia species, and the isolation-with-migration coalescent model was assessed to determine whether genetic divergence between Amazilia species occurred in the presence of gene flow.ResultsGenetic divergence between A. violiceps and A. viridifrons was shallow, with incomplete lineage sorting and introgression. Species delimitation supported three independent lineages: A. violiceps populations located north of the Trans-Mexican Volcanic Belt; a mixture of A. violiceps south of the volcanic belt and A. viridifrons populations; and A. villadai populations east of the Isthmus of Tehuantepec. Gene flow and divergence time estimates, and demographic and palaeodistribution patterns support the model of species diversification by isolation with migration and habitat shifting in response to Pleistocene climatic fluctuations.Main conclusionsThe process of speciation in the Amazilia species complex may be explained by the combined effects of isolation resulting from the Trans-Mexican Volcanic Belt and the lowlands at the Isthmus of Tehuantepec and habitat shifting in response to Quaternary climatic changes.
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Niche conservatism, the hypothesis that niches remain constant through time and space, is crucial for the study of biological invasions as it underlies native-range based predictions of invasion risk. Niche changes between native and non-native populations are increasingly reported. However, it has been argued that these changes arise mainly because in their novel range, species occupy only a subset of the environments they inhabit in their native range, and not because they expand into environments entirely novel to them. Here, using occurrences of 29 vertebrate species native to either Europe or North America and introduced into the other continent, we assess the prevalence of niche changes between native and non-native populations and assess whether the changes detected are caused primarily by native niche unfi lling in the non-native range rather than by expansion into novel environments. We show that niche overlap between native and non-native populations is generally low because of a large degree of niche unfi lling in the non-native range. This most probably refl ects an ongoing colonization of the novel range, as niche changes were smaller for species that were introduced longer ago and into a larger number of locations. Niche expansion was rare, and for the few species exhibiting larger amounts of niche overlap, an unfi lling of the niche in the native range (e.g. through competition or dispersal limitations) is the most probable explanation. Th e fact that for most species, the realized non-native niche is a subset of the realized native niche allows native-range based niche models to generate accurate predictions of invasion risk. Th ese results suggest that niche changes arising during biological invasions are strongly infl uenced by propagule pressure and colonization processes, and we argue that introduction history should be taken into account when evaluating niche conservatism in the context of biological invasions.
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The evolutionary history of the Mexican sierras has been shaped by various geological and climatic events over the past several million years. The relative impacts of these historical events on diversification in highland taxa, however, remain largely uncertain owing to a paucity of studies on broadly‐distributed montane species. We investigated the origins of genetic diversification in widely‐distributed endemic alligator lizards in the genus Barisia to help develop a better understanding of the complex processes structuring biological diversity in the Mexican highlands. We estimated lineage divergence dates and the diversification rate from mitochondrial DNA sequences, and combined divergence dates with reconstructions of ancestral geographical ranges to track lineage diversification across geography through time. Based on our results, we inferred ten geographically structured, well supported mitochondrial lineages within Barisia. Diversification of a widely‐distributed ancestor appears tied to the formation of the Trans‐Mexican Volcanic Belt across central Mexico during the Miocene and Pliocene. The formation of filter barriers such as major river drainages may have later subdivided lineages. The results of the present study provide additional support for the increasing number of studies that suggest Neogene events heavily impacted genetic diversification in widespread montane taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 382–394.
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Young species complexes that are widespread across ecologically disparate regions offer important insights into the process of speciation because of their relevance to how local adaptation and gene flow influence diversification. We used mitochondrial DNA and up to 28,152 genome-wide SNPs from polytypic barking frogs (Craugastor augusti complex) to infer phylogenetic relationships and test for the signature of introgressive hybridization among diverging lineages. Our phylogenetic reconstructions suggest (1) a rapid Pliocene-Pleistocene radiation that produced at least nine distinct lineages and (2) that geographic features of the arid Central Mexican Plateau contributed to two independent northward expansions. Despite clear lineage differentiation (many private alleles and high between-lineage Fst scores), D-statistic tests, which differentiate introgression from ancestral polymorphism, allowed us to identify two putative instances of reticulate gene flow. Partitioned D-statistics provided evidence that these events occurred in the same direction between clades but at different points in time. After correcting for geographic distance, we found that lineages involved in hybrid gene flow interactions had higher levels of genetic variation than independently evolving lineages. These findings suggest that the nature of hybrid compatibility can be conserved over long periods of evolutionary time and that hybridization between diverging lineages may contribute to standing levels of genetic variation.This article is protected by copyright. All rights reserved.
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We quantify the population divergence processes that shaped population genetic structure in the Trans-Volcanic bunchgrass lizard (Sceloporus bicanthalis) across the highlands of south-eastern Mexico. Multilocus genetic data from nine nuclear loci and mitochondrial (mt)DNA were used to estimate the population divergence history for 47 samples of S. bicanthalis. Bayesian clustering methods partitioned S. bicanthalis into three populations: (1) a southern population in Oaxaca and southern Puebla; (2) a population in western Puebla; and (3) a northern population with a broad distribution across Hidalgo, Puebla, and Veracruz. The multilocus nuclear data and mtDNA both supported a Late Pleistocene increase in effective population size, and the nuclear data revealed low levels of unidirectional gene flow from the widespread northern population into the southern and western populations. Populations of S. bicanthalis experienced different demographic histories during the Pleistocene, and phylogeographical patterns were similar to those observed in many co-distributed highland taxa. Although we recommend continuing to recognize S. bicanthalis as a single species, future research on the evolution of viviparity could gain novel insights by contrasting physiological and genomic patterns among the different populations located across the highlands of south-eastern Mexico. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 852–865.
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A principal objective of this paper is to discuss a class of biased linear estimators employing generalized inverses. A second objective is to establish a unifying perspective. The paper exhibits theoretical properties shared by generalized inverse estimators, ridge estimators, and corresponding nonlinear estimation procedures. From this perspective it becomes clear why all these methods work so well in practical estimation from nonorthogonal data.
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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.
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Mexico City has long been known as one of the world’s largest mega-cities. Although, the city’s growth rates have slowed since the 1980s, this process is not manifested evenly in spatial terms. Peripheral municipalities continue to grow at higher rates, including those municipalities in the southern part of the Federal District that contain its remaining conservation land. This growth is largely, but not exclusively, driven by the ongoing search for housing among lower-income households in the form of irregular settlement. Over time, this incremental pattern of settlement expansion has fragmented conservation land and impaired its ecological functioning. Given their role in land use planning with the reintroduction of elected local governments in the Federal District in 1997, this situation has placed municipalities quite literally at the “frontlines” of this planning and sustainability challenge. This paper examines the approach for managing land use regularization processes related to irregular settlement in conservation land adopted by the municipality of Xochimilco in its 2005 urban development plan, with reference to the experience of a specific case study community. Based on a series of interviews with residents and planning officials, the paper documents the highly-negotiated nature of “normative” planning that focuses on mitigating the impact of settlement in the conservation zone rather than stopping it completely. Given the enormous social pressures to access land for housing, the paper concludes that realistic efforts to preserve the remaining conservation land must involve a more comprehensive approach that better integrates environmental and social equity issues within and among municipal and upper-levels of government.
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The isolation of South America from Central America and Africa during the Tertiary Period left a strong imprint on the flora of the Neotropics. South American Eocene through Miocene fossil assemblages, both pollen and macrofossils, document a rich tropical flora on the continental margins, and represent some of the only data on pre-landbridge lowland taxa in South America. Lowland Miocene floras from Amazonia are remarkably similar in their high diversity to Amazonian floras today based on lists of dominant families. Recent geophysical data on the uplift of the northern Andes show a strong correlation between uplift and the development and diversification of montane forests in Colombia and Venezuela. The emergence of a continuous landbridge at 3 Ma between Central and South America is well documented and is demonstrated by the arrival of temperate elements in South American highlands and concurrent appearance of South American taxa in Central America. There is no evidence for displacement of lowland tropical plants in South America by northern immigrants, which appears to stand in contrast to the published record for mammals. The mix of taxa in extant Mexican tropical floras derived from tropical South America, tropical Central America, and from remnants of northern tropical Eocene floras is strong evidence for the impact that the landbridge through the Panamanian isthmus had on the neotropical flora. The early appearance of low-elevation savannas is inferred from an increase in grass pollen in the middle Pliocene of Panama; however, widespread savannas are not indicated by pollen data from the Central American region. Rather, beginning in the latest Miocene Epoch and continuing up to the Quaternary, a mix of tropical rainforest and mixed tropical woodlands is suggested for the lowlands, based on pollen evidence. Accumulating data on temperature changes during the late Tertiary and Quaternary Periods points to low-latitude temperature fluctuations of up to 6 degrees C. Proposals of accompanying widespread rainfall fluctuations are more equivocal. Rainfall probably varied regionally, resulting in a mosaic of habitats controlled by river migration, sea level fluctuations. local dryness, and local uplift. Zones postulated as refugia provide testable hypotheses using neoecological and paleoecological data. The paleoecological data to test three hypotheses are still limited taxonomically and spatially. It is important to stress that the effect of the isolation of South American neotropical floras has not been erased in the 3 million years since their connection with Central America. New data front middle and late Miocene floras in South America will be critical in determining the degree to which the composition of South American floras has been influenced by immigration of plants from the better-known Central American area to the north.
Article
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.
Article
Aim To assess the genealogical relationships of widespread montane rattlesnakes in the Crotalus triseriatus species group and to clarify the role of Late Neogene mountain building and Pleistocene pine–oak forest fragmentation in driving the diversification of Mexican highland taxa. Location Highlands of mainland Mexico and the south-western United States (Texas, New Mexico, and Arizona). Methods A synthesis of inferences was used to address several associated questions about the biogeography of the Mexican highlands and the evolutionary drivers of phylogeographical diversity in co-distributed taxa. We combined extensive range-wide sampling (130 individuals representing five putative species) and mixed-model phylogenetic analyses of 2408 base pairs of mitochondrial DNA to estimate genealogical relationships and divergence times within the C. triseriatus species group. We then assessed the tempo of diversification using a maximum likelihood framework based on the birth–death process. Estimated times of divergences provided a probabilistic temporal component and questioned whether diversification rates have remained constant or varied over time. Finally, we looked for phylogeographical patterns in other co-distributed taxa. Results We identified eight major lineages within the C. triseriatus group, and inferred strong correspondence between maternal and geographic history within most lineages. At least one cryptic species was detected. Relationships among lineages were generally congruent with previous molecular studies, with differences largely attributable to our expanded taxonomic and geographic sampling. Estimated divergences between most major lineages occurred in the Late Miocene and Pliocene. Phylogeographical structure within each lineage appeared to have been generated primarily during the Pleistocene. Although the scale of genetic diversity recognized affected estimated rates of diversification, rates appeared to have been constant through time. Main conclusions The biogeographical history of the C. triseriatus group implies a dynamic history for the highlands of Mexico. The Neogene formation of the Transvolcanic Belt appears responsible for structuring geographic diversity among major lineages. Pleistocene glacial–interglacial climatic cycles and resultant expansions and contractions of the Mexican pine–oak forest appear to have driven widespread divergences within lineages. Climatic change, paired with the complex topography of Mexico, probably produced a myriad of species-specific responses in co-distributed Mexican highland taxa. The high degree of genetic differentiation recovered in our study and others suggests that the Mexican highlands may contain considerably more diversity than currently recognized.