Mexican Clade Research Articles

Phylogenetic relationships among Mexican species of the genus Sechium (Cucurbitaceae)

The genus Sechium includes 11 species, which are highly related to the genus Sicyos. Sechium is native to Mesoamerica, but only S. edule and S. tacaco have been domesticated. Sechium edule is the most exploited species of the genus due to its broad phenotypic variability. A total of 68 samples from the species S. chinantlense, S. compositum, S.hintonii and S.edule were evaluated, as well as their respective varietal complexes (albus, nigrum and virens groups), thereby amplifying the loci of mitochondrial DNA (CoxIII), chloroplast DNA (rbcL) and the nuclear ribosomal ITS1-5.8S-ITS2 region. This was done with the aim of establishing phylogenetic relationships that help to understand evolutionary processes, which, in turn, will contribute to the taxonomy of the Mexican clade of Sechium and its exploitation in breeding. Phylogenetic trees obtained from Bayesian inference and the maximum parsimony show that S. chinantlense, S. compositum, and S. edule form a cluster with a high phylogenetic kinship. Sechium chinantlense and S. compositum could possibly be populations or varieties derived from S. edule.

Phylogenetics of the genus Sechium P. Brown: A review

The Sechium P. Br. genus composed of 11 species, which originated from the mountainous regions of Mesoamerica, have been domesticated and diversified. These species are clustered in two large groups: the Mexican clade and the Central American clade. Morphological and molecular studies have shown that species of the Mexican clade are formed through interspecific hybridizations and genetic flow, with the exception of S. mexicanum, which is strongly linked to the genus Sicyos. The objective of this review was to analyze the phylogenetics of Sechium based on morphological and molecular studies, which contributed to taxonomic knowledge and utilization, thereby favoring its conservation and improvement. The Central American clade is well supported with molecular data, but not so with morphological data. The species in this clade were geographically isolated and endemic. S. edule and S. tacaco are exploited species in the agricultural and industrial sectors, and both have an extensive genetic and phenotypic diversity that has allowed them to diversify and expand into different ecological niches. Finally, the Central American species of Sechium thrive in adverse environments of temperatures of mesophyll forest and high relative humidity, with characteristics that can give resistance to frosts and phytopathogenic agents, as well as cultivated species of this genus.

A New Section of Anthurium: Section Cordato-punctatum (Araceae), Restricted to Central America

Molecular studies have recently shown that a predominantly Mexican clade of Anthurium Schott species with ovate-cordate to ovate-sagittate leaf blades with glandular punctations on the lower (abaxial) surface is distinct from all other groups of Anthurium. This new section, Cordato-punctatum Croat & Carlsen, is one of three sections of Anthurium essentially restricted to Central America, and it contains six taxa. In this article, we describe and typify this new section, characterize its morphology, compare it to other Central American clades, and provide a current species list with geographic distributions.

Notes on Vampyressa thyone (Chiroptera: Phyllostomidae): distribution, genetics and hypopigmentation

Abstract: The frugivorous bats of the genus Vampyressa include five neotropical species, and some of them are considered relatively rare and uncommonly encountered. The northernmost distribution of this genus is in Mexico where only one species, the monotypic Vampyressa thyone, is found. Here, we report the Northwesternmost record for this species, extending its distribution range to the state of Guerrero, Mexico. This record extends the limit of the species distribution by more than 153 km. We also compared this specimens with other V. thyone, and using mitochondrial cytochrome-b sequences we detected three geographic clades within the species. The new Mexican specimen represent the most divergent cytochrome-b sequence within V. thyone. We recommend a taxonomic revision to validate the taxonomic status of the three groups detected within V. thyone, particularly the differentiated Mexican clade. Additionally, we report a case of hypopigmentation in another V. thyone collected in a mature tropical rainforest in Chiapas, Mexico.

Nahuatlea: a new genus of compositae (Gochnatieae) from North America.

In the course of a detailed molecular study of the tribe Gochnatieae (Compositae: Gochnatioideae) it became apparent that the genus Gochnatia (sensu Cabrera) was not monophyletic but composed of a number of morphologically, geographically, and molecularly distinct clades. All but one of these clades had previously been recognized at the generic or sectional level and therefore had a name that could be applied. However, one clade, whose members are from Mexico and adjacent parts of the United States, had never been recognized as a distinct taxon. The Mexican clade is the sister group of the Caribbean clade which seems to indicate a dispersal event from Southern South America to Mexico and from Mexico to the Caribbean. Here we provide the Mexican clade with a genus name, Nahuatlea, and make the necessary new combinations. The name is derived from Nahuatl, the major indigenous language that is spoken in the area where most of the collections were gathered. A genus description, key to species, images, and a short, species descriptions, are provided.

Chromosome number reduction in the sister clade of Carica papaya with concomitant genome size doubling.

Caricaceae include six genera and 34 species, among them papaya, a model species in plant sex chromosome research. The family was held to have a conserved karyotype with 2n = 18 chromosomes, an assumption based on few counts. We examined the karyotypes and genome size of species from all genera to test for possible cytogenetic variation. We used fluorescent in situ hybridization using standard telomere, 5S, and 45S rDNA probes. New and published data were combined with a phylogeny, molecular clock dating, and C values (available for ∼50% of the species) to reconstruct genome evolution. The African genus Cylicomorpha, which is sister to the remaining Caricaceae (all neotropical), has 2n = 18, as do the species in two other genera. A Mexican clade of five species that includes papaya, however, has 2n = 18 (papaya), 2n = 16 (Horovitzia cnidoscoloides), and 2n = 14 (Jarilla caudata and J. heterophylla; third Jarilla not counted), with the phylogeny indicating that the dysploidy events occurred ∼16.6 and ∼5.5 million years ago and that Jarilla underwent genome size doubling (∼450 to 830-920 Mbp/haploid genome). Pericentromeric interstitial telomere repeats occur in both Jarilla adjacent to 5S rDNA sites, and the variability of 5S rDNA sites across all genera is high. On the basis of outgroup comparison, 2n = 18 is the ancestral number, and repeated chromosomal fusions with simultaneous genome size increase as a result of repetitive elements accumulating near centromeres characterize the papaya clade. These results have implications for ongoing genome assemblies in Caricaceae.

Phylogenetics and evolution of theTillandsia utriculatacomplex (Bromeliaceae, Tillandsioideae) inferred from three plastid DNA markers and the ETS of the nuclear ribosomal DNA

We performed a phylogenetic analysis using maximum parsimony and Bayesian inference of three plastid DNA markers and the external transcribed spacer (ETS) of nuclear ribosomal DNA to assess the species composition of the Tillandsia utriculata complex and their phylogenetic relationships, and to reconstruct patterns of character evolution and biogeography. The results showed that species of the T. utriculata complex are nested in a clade composed mainly of Mexican and Central American species of T. subgenus Tillandsia (Mexican Clade), and are organized in two lineages: the T. utriculata clade and the T. limbata clade. The ancestor of the core Mexican Clade was probably a T. utriculata-like epiphyte (Group II-type remote flowers and flexuous rachises). The T. utriculata clade is defined morphologically by the presence of acute petals. In this clade, there are two lineages: one of high-elevation, saxicolous, grey-leaved plants from the Mexican Plateau; and one which is more widespread and found from the Gulf of Mexico to Venezuela. The T. limbata clade probably arose in western Mesoamerica and is defined by rounded petals. These species are found mainly in tropical dry forests, but one species colonized wet environments of eastern Mesoamerica. Finally, analyses based on the ETS region allowed us to distinguish between T. utriculata and T. pringlei.

An Expanded Plastid Phylogeny of Marsilea with Emphasis on North American Species

Abstract Ferns of the genus Marsilea (water clover) are potentially invasive aquatic and wetland plants. They are difficult to identify to species because of subtle diagnostic characters, the sterile condition of many specimens, and unresolved taxonomic problems. We sequenced four plastid regions (rbcL, rps4, rps4-trnS spacer, and trnL-F spacer) from 223 accessions across ca. 38 species. Our goals were to: 1) attempt to identify problematic Marsilea specimens from the southeastern U.S., and 2) assess species delimitation using molecular data. Florida specimens previously identified as M. aff. oligospora do not match true M. oligospora (native to the western USA), and might represent an undescribed native species. The molecular data fail to resolve many species as monophyletic within the New World Marsilea section Nodorhizae. The data reveal two strongly supported clades within section Nodorhizae: 1) A western U.S. /Mexican clade; and 2) A U.S. Gulf coastal plain/Florida/Caribbean clade. This DNA/morpholog...

Phylogeny of the Linnaea clade: Are Abelia and Zabelia closely related?

Phylogenetic investigations based on molecular and morphological data have improved our understanding of Dipsacales phylogeny dramatically over the past 20 years. The Linnaea clade, however, has mostly been neglected and Zabelia has rarely been included in previous studies. We present the results of a molecular investigation including nine Abelia and five Zabelia species based on nuclear (ITS) and plastid (trnK, matK, atpB-rbcL, trnL-F) sequence data using maximum parsimony, Bayesian inference, and maximum likelihood. Our results indicate that Abelia is paraphyletic and possibly polyphyletic. The genus falls apart into a Mexican clade, corresponding to Abelia section Vesalea, and an Asian clade (excluding A. spathulata), corresponding to Abelia section Abelia. A close relationship between Zabelia and other members of the traditional Linnaea clade is not recovered by our analyses. Instead, Zabelia is associated with either the Morina or the Valeriana clade. Support for a monophyletic Linnaea clade without Zabelia is strong.

Systematics and Biogeography of the Silverside Tribe Menidiini (Teleostomi: Atherinopsidae) Based on the Mitochondrial ND2 Gene

The silverside fish tribe Menidiini (Teleostei: Atherinopsidae) consists of four genera, Menidia, Labidesthes, Poblana, and Chirostoma, that are distributed along the Atlantic coast of North America, throughout the Gulf of Mexico, insular United States, and the Mesa Central of Mexico. It has been suggested that Chirostoma, Poblana, and Menidia should be recognized as a single genus under the nominal Menidia. To test this hypothesis, phylogenetic relationships within the tribe Menidiini were assessed using the mitochondrially encoded ND2 gene. Monophyly of the Menidiini tribe was supported. Results also failed to support monophyly for the genera Menidia and Chirostoma as currently recognized. A central Mexican clade, inclusive of Chirostoma and Poblana, was recovered as monophyletic and strongly supported. Relationships within the Mesa Central clade support a previously recognized ''humboldtianum'' clade and the paraphyly of Chirostoma with respect to Poblana.

Phylogenetic relationships of Mexican minnows of the genus Notropis (Actinopterygii, Cyprinidae)

We conducted phylogenetic analyses based on complete mitochondrial cytochrome b gene sequences among southern and central Mexican cyprinid species, included in the genera Notropis and Hybopsis. In addition 15 northern species of the genera Notropis and Hybopsis were included in the analyses in order to place the Mexican species into a larger phylogenetic framework. The phylogenetic relationships supported the existence of five major clades: (1) including species of the subgenus Alburnops of the genus Notropis plus N. shumardi; (2) species of the subgenus Notropis; (3) species of the genus Hybopsis; (4) species of the N. texanus + N. volucellus species group of the genus Notropis; (5) Mexican endemic species of the genus Notropis plus the genus Yuriria. Previous phylogenetic inferences based on morphological characters resolved the Mexican minnows analysed as N. sallaei, N. calientis, N. boucardi and Y. alta, non-monophyletic. According to our cytochrome b evidence all Mexican minnows of the genera Notropis and Yuriria formed a monophyletic group with respect to the northern species of the genera Notropis and Hybopsis. Within the Mexican clade, three well-supported clades were identified: the first included the closely related species N. moralesi and N. boucardi, which occur in three independent drainages of south Mexico; the second consisted of two different lineages, N. imeldae and an undescribed species of Notropis, inhabiting two independent drainages of south Mexico; the third comprised two central Mexican Notropis species (N. calientis and N. sallaei) and the Y. alta populations. Based on this study and pending a more extensive taxonomic revision of the genus Notropis, we adopt the conservative criterion of considering all Notropis species from southern and central Mexico examined, including Y. alta, as belonging to the genus Notropis. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 323–337.

Phylogenetic Relationships of North American Garter Snakes (Thamnophis) Based on Four Mitochondrial Genes: How Much DNA Sequence Is Enough?

The clade of garter snakes (Thamnophis) includes some of the most abundant and well-studied snakes in North America. However, phylogenetic relationships within this group have been little studied. We used DNA sequences of four mitochondrial genes (cytochrome b and NADH dehydrogenase subunits 1, 2, and 4) to estimate relationships among 29 of the 31 recognized species of Thamnophis plus the related species Adelophis foxi. Both maximum parsimony (MP) and maximum-likelihood (ML) analyses of all these genes combined produced well-resolved trees with moderate (70–89%) to strong (90–100%) bootstrap support for most clades. MP and ML trees were very similar, with no strongly supported conflict between the two analyses. These analyses identify a clade of 12 species largely restricted to México (the “Mexican clade”), and a clade containing 15 species that collectively range from Central America to southern Canada (the “widespread clade”). These two groups are identified as sister taxa in both MP and ML analyses. A clade consisting of the ribbon snakes (T. sauritus and T. proximus) and the common garter snake (T. sirtalis) is placed as the sister group to all other Thamnophis (i.e., the Mexican + widespread clades) in our analyses. High bootstrap proportions at several levels in the tree support the inclusion of both Thamnophis validus, which has traditionally been placed in the genus Nerodia, and the poorly known species Adelophis foxi within Thamnophis. We used randomly sampled characters (i.e., standard bootstrapping) and randomly sampled contiguous blocks of characters to examine the effect of number of characters on resolution of and support for relationships within Thamnophis using MP. In general, these analyses indicate that we have reached a point of strongly diminishing returns with respect to the effect of adding mtDNA sequence characters for the current set of taxa; our sample of 3809 mtDNA characters is apparently “enough.” The next steps to improve the phylogenetic estimate may be to add nuclear DNA sequences, morphology, or behavior, or to sequence additional mtDNA lineages within species.