Enrico A. Ruiz

Effect of geographic isolation on genetic differentiation in Dendroctonus pseudotsugae (Coleoptera: Curculionidae)

Genetic structure of phytophagous insects has been widely studied, however, relative influence of the effect of geographic isolation, the host plant or both has been subject of considerable debate. Several studies carried out on bark beetles in the genus Dendroctonus evaluated these factors; nonetheless, recent evidence has shown that genetic structuring is a more complex process. Our goal was to examine the effect of geographic isolation on genetic structure of the Douglas-fir beetle Dendroctonus pseudotsugae. We used mtDNA cytochrome oxidase I (COI) sequences and RAPD markers. One hundred-seventy-two individuals were obtained from 17 populations, for which we analyzed 60 haplotypes (among 172 sequences of COI gene, 550 bp long) and 232 RAPD markers (7 primers). Analyses of molecular variance (AMOVA and SAMOVA), F-statistics and linear regressions suggest that the genetic structure of D. pseudotsugae is strongly influenced by geographic distance. We found that D. pseudotsugae has high intra- and inter-population genetic variation compared with several other bark beetles. Genetic differences among populations based on COI and RAPD markers were correlated with geographic distance. The observed genetic differences between northern (Canada-USA) and southern (Mexico) populations on Pseudotsuga menziesii var. glauca confirm that these two sets of populations correspond to previously assigned subspecies.

Molecular and Morphological Analysis of Dendroctonus pseudotsugae (Coleoptera: Curculionidae: Scolytinae): an Assessment of the Taxonomic Status of Subspecies

ABSTRACT Dendroctonus pseudotsugae Hopkins infests Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, throughout the distribution of that tree species from British Columbia to northern Mexico. The subspecies Dendroctonus pseudotsugae barragani Furniss was described from the mountains of Chihuahua, Sierra Madre Occidental, Mexico, whereas the nominal subspecies, Dendroctonus pseudotsugae pseudotsugae Hopkins, occurs north of Mexico. The description of D. p. barragani was based on the only known Mexican population at that time. More recently, new populations of this beetle have been discovered at 13 additional localities in Chihuahua, Durango, Coahuila, and Nuevo Leon, Mexico. To test whether these additional populations support the existence of two subspecies, we performed a taxonomic reassessment combining molecular markers (cytochrome oxidase I), morphological characters used in the original description, and newly described morphological characters. Phylogenetic analysis of 89 haplotypes confirms that the Mexican populations are distinct from the sampled populations in the United States and Canada. Morphological analysis indicates that intraspecific variation is greater than previously considered within Mexican populations. However, at least seven characters on the head, pronotum, and elytra (including three previously undescribed characters of frons sculpture) consistently discriminate among Canada—U.S. and Mexico populations. The extension of the known distribution of this beetle in Mexico and verification of its subspecific status will aid in the management and conservation of Pseudotsuga in Mexico.

Historical Demography and Phylogeography of a Specialist Bark Beetle, Dendroctonus pseudotsugae Hopkins (Curculionidae: Scolytinae)

ABSTRACT Contemporary distribution of North American species has been shaped by past glaciation events during the Quaternary period. However, their effects were not as severe in the southern Rocky Mountains and Northern Mexico as elsewhere in North America. In this context, we test hypotheses about the historical demography of Dendroctonus pseudotsugae, based on 136 haplotypes of mitochondrial cytochrome oxidase I. The phylogenetic analysis yielded four haplogroups corresponding to northwestern United States and southwestern Canada (NUS), southwestern United States (Arizona, SUS), northwestern Mexico (Sierra Madre Occidental, SMOC), and northeastern Mexico (Sierra Madre Oriental, SMOR). Predictions of demographic expansion were examined through neutrality tests against population growth and mismatch distribution. Results showed that the NUS and SMOC haplogroups have experienced demographic expansion events, whereas the SUS and SMOR haplogroups have not. Divergence times between pairs of haplogroups were estimated from early to middle Pleistocene. The longer divergence time between NUS and all other haplogroups could be the result of refugia within the Pacific Northwest and northern Rocky Mountains and long-term isolation from southernmost populations in Mexico. The results obtained in this study are in agreement with the evolutionary history of the host Douglas-fir, as the warmer climates of interglacial periods pushed conifers northward of Colorado, New Mexico, and Arizona, whereas environmental changes reduced the population size of Douglas-fir and forced fragmentation of distribution range southward into northern Mexico.

Late-Pleistocene Phylogeography and Demographic History of Two Evolutionary Lineages of Artibeus jamaicensis (Chiroptera: Phyllostomidae) in Mexico

The Artibeus jamaicensis complex is an important component of the mammal biological diversity of the New World. Although there are numerous studies on the taxonomy and phylogeny of the complex, group relationships are still debated. Previous studies hypothesised that this species originated in South America and later colonised the Antilles Islands either through a northward migration or an eastward migration via Middle America. However, these studies do not include populations from Middle America west of the Yucatan Peninsula, making it difficult to obtain a clear description of the role of these populations in the evolutionary history of the species. In this study, we describe the phylogeography and demographic history of A. jamaicensis populations from Middle America west of the Yucatan Peninsula using cytochrome-b (612 bp) and D-loop (391 bp) mtDNA markers. Our phylogenetic analyses (maximum likelihood and Bayesian inference) did not recover clades corresponding to the previously recognised Middle American subspecies (A. j. triomylus and A. j. yucatanicus); rather, two haplogroups were observed, which showed extensive genetic diversity and strong genetic structure akin to that expected for a Middle American origin for the island populations. Bayesian skyline plots and mismatch distributions revealed that such haplogroups experienced a recent population expansion, which most likely took place in the late Pleistocene (100,000–216,000 BP). These estimates agree with earlier hypotheses that suggested a recent evolutionary history for A. jamaicensis, with hypotheses that suggested the existence of two different lineages migrating northwest from South America to Middle America, and with the possible colonisation of the Antilles Islands derived from both Yucatan Peninsula and northern South America.

Genetic Diversity of the Atlantic Ghost Crab Ocypode quadrata (Decapoda: Ocypodidae) in Two Beaches With Different Anthropogenic Disturbance in the North Coast of Veracruz, Mexico:

The constant demographic expansion of human population is now recognized as a stressing factor for ecological communities on beaches, and their effects have been barely explored in developing countries such as Mexico, where heavy coastline industrialization is currently undergoing. In this work, we study how anthropogenic factors have affected the Atlantic Ghost Crab (Ocypode quadrata) in two beaches with different anthropogenic disturbance in northern Veracruz (near Tuxpan and Tamiahua), Mexico. To this end, we evaluated the species genetic diversity using a fragment of the Cytochrome Oxidase I gene, along with several measurements (number of haplotypes, haplotype diversity, and nucleotide diversity, etc.), estimations of genetic relationship (haplotype network, phylogenetic analysis, gene flow), and statistical tests on average genetic distances (Student’s t test). We found 32 haplotypes, 22 from Tuxpan and 15 from Tamiahua. Despite the occurrence of almost 50% more haplotypes in Tuxpan than in Tamiahua, the correction for differences in sample size indicated that such a difference is statistically nonsignificant. A similar pattern was found with other genetic measurements. Similarly, the haplotype network and the phylogenetic reconstruction failed to recover haplotype clusters or haplogroups associated exclusively to one or another beach, whereas gene flow between localities was of the same order of magnitude in both directions. The Student’s t test showed that differences in genetic distances between localities (estimated using p-distances and Jukes-Cantor 69) were not statistically significant. Finally, although the anthropogenic effects between beaches in Tuxpan and Tamiahua are remarkable different, this has not been reflected in the genetic diversity of O. quadrata.

Recent Collecting Reveals the Presence of Boettgerilla pallens (Stylommatophora, Boettgerillidae) in Mexico

Abstract: An introduced slug, Boettgerilla pallens Simroth, 1912, was found both in the Pedregal de San Angel Ecological Reserve, Ciudad Universitaria, Mexico City and Teopancingo, Puebla. Although this slug is native to Europe, it has been recently recorded from various locations around the world. Through dissection, the diagnostic characters were identified as the spindle shaped swelling along the vas deferens characteristic of the genus, and the elongate shape of the bursa copulatrix typical of this species. In addition, cytochrome oxidase I mtDNA, and 16S and 28S ribosomal RNA genes were sequenced and used in a phylogenetic analysis to confirm its identity.

Correct Identification of Ochrobactrum anthropi From Blood Culture Using 16rRNA Sequencing: A First Case Report in an Immunocompromised Patient in Mexico

The present report describes the misidentification of Brucella spp. from a positive blood culture using traditional microbiology tests. A molecular test identified the bacterium as Ochrobactrum anthropi. According to the information available, this report is the first to include this type of case in Mexico.