Central Mexican Research Articles

Taxonomical and functional diversity dynamics of conspicuous echinoderms in the northeastern tropical Pacific over a decade

Understanding what determines spatio-temporal changes in echinoderm assemblages from an integrative perspective that considers biodiversity, species evenness, and species’ niches could permit superior community-scale characterizations of habitat resilience to disturbance. Such an approach was taken herein by tracking a Central Mexican Pacific echinoderm assemblage between 2012 and 2021, and higher richness, diversity, evenness, and functional entity counts were associated with more heterogeneous benthic assemblages. Echinoderm taxonomic composition was influenced by ENSO events, with higher functional diversity found during La Niña events. Conservation strategies should focus on species with unique functional traits to maintain the balance of coral community functionality.

Biodiversity and new records of benthic amphipods (Crustacea: Peracarida: Amphipoda) from coral reef protected natural areas in the Mexican Caribbean Sea

The Mexican Caribbean Sea is the longest section of the Mesoamerican Caribbean Sea, with 16 protected marine areas. During 2015 and 2016, 2 sampling campaigns in the Puerto Morelos Coral Reef National Park and the Sian Ka’an Biosphere Reserve, Quintana Roo, Mexico, were carried out to determine the biodiversity of benthic amphipods. In addition, the previously documented amphipod data were included to summarize the first checklist of such amphipods along the Mexican Caribbean Sea. The present study found 35 families, 70 genera, and 121 species, of which 41 species had not been previously reported in the Mexican Caribbean Sea, and 5 species represented new records of amphipods from the Caribbean Sea. According to the information summarized in this amphipod’s inventory, both the coral reefs Puerto Morelos and Sian Ka’an, located in the north and central Mexican Caribbean Sea, represented the protected natural areas with the largest amounts of benthic amphipod species thus far.

Spatio-temporal variation in the growth of coral fragments of opportunity in the Eastern Tropical Pacific: implications for coral reef restoration

Introduction: Coral- reef communities are considered one of the most biodiverse, but also most threatened, marine ecosystems, and the accelerating loss of habitat over the past decades warrants active intervention. 
 Objective: The present study demonstrates the successful implementation of a low-impact restoration technique in three Central Mexican Pacific degraded coral communities, using a protocol based on natural fragmentation (“fragments of opportunity”) of the branching coral Pocillopora spp., considered the most abundant and primary carbonate-producing coral species of the Eastern Tropical Pacific. 
 Methods: The restoration program was implemented in two offshore and one inshore coraline areas. The relationships between seawater temperature and coral survival, growth, and attachment rate were assessed over one year, with 183 fragments monitored each month. 
 Results: The mean coral growth rate was 3.3 ± 0.1 mm mo-1, with annual growth rates in length and width of 39.9 ± 14.2 and 36.5 ± 19.5 mm yr-1, respectively. Self-attachment efficiency was 78 % and the survival rate was high (84 %). The growth rate differed significantly among reefs. 
 Conclusions: Upon monitoring directly fragmented corals over a year, growth rates were deemed high enough to merit active restoration in the region. However, our data show that structural and abiotic differences and seasonal variability must be considered overall in successful long-term coral community restoration initiatives in the eastern Pacific region.

The contribution of assisted coral restoration to calcium carbonate production in Eastern Pacific reefs

Introduction: Hermatypic corals have the capacity to construct the physical reef-framework and maintain the balance of coral reef functionality. However, in the past three decades, coral communities have been menaced by natural and anthropic pressures, resulting in an abrupt coral cover decline, and slow natural recovery. To mitigate coral reef collapse, assisted restoration techniques has been implemented and improved worldwide, However, the long-term effects of such interventions on ecological attributes have been scarcely reported. 
 Objective: This study evaluated the effect of assisted coral intervention on calcium carbonate production (kg CaCO3 m-2 yr-1) and ecological volume (cm3) yielded by branching and massive corals from the central Mexican Pacific. 
 Methods: We used colony size, extension rate, and skeletal density measurements of direct outplanted Pocillopora and Pavona coral species to calculate coral carbonate production, ecological volume, and model their long-term potential. 
 Results: Coral carbonate produced after one-year of outplanting increased by 42 % (1.17 kg CaCO3 m-2 yr-1), where Pocillopora spp. and Pavona clavus corals contribute with 0.97 and 0.20 kg CaCO3 m-2 yr-1, respectively. The ecological volume also increased by 384 cm3 for Pocillopora and 56 cm3 for Pavona after one year period. Furthermore, the results suggest that long-term coral restoration actions (10 years) have the potential to significantly increase carbonate production. 
 Conclusions: our data indicate that coral restoration initiatives have the potential to help mitigate the current low calcium carbonate production of Mexican Pacific reefs and may significantly contribute to the long-term maintenance of reef-framework based on ecological engineering tools, such initiatives represent essential functional properties related to reef ecosystem services provision.

Active restoration efforts in the Central Mexican Pacific as a strategy for coral reef recovery

Introduction: The 1997-98 El Niño event caused massive coral bleaching and mortality in the Central Mexican Pacific (CMP). Punta de Mita alone used to harbor more than 30 % of the coral coverage in this region, with a mono-specific Pocillopora coverage. The 1997-1998 ENSO event caused massive coral mortality reducing live coral coverage to < 5 %. Despite being considered a coral region unlikely to recover, recent restoration efforts have been implemented to rehabilitate the coral community.
 Objective: To assess coral recovery by analyzing the coral growth and survival rates of branching Pocillopora species at Punta de Mita.
 Methods: Healthy coral fragments of opportunity were re-attached to the natural substrata using zip ties and measured considering their growth in terms of maximum length and width (cm) to determine their annual extension rates.
 Results: After 50 weeks, corals duplicated their size, with a mean growth of ~ 4 cm year-1. After 100 weeks (2 years), corals triplicated their size, increasing on average 8–9 cm in each diameter.
 Conclusions: Successful coral reef restoration activities in the Central Mexican Pacific are the result of Pocillopora’s physiological processes, such as fast growth rates, and recent life-history traits, like the ability to cope with thermal anomalies, which enable them to thrive in a dynamic region severely affected by natural and anthropogenic perturbations. Indeed, a region considered unlikely to recover has regained its live coral cover from < 5 % in 1998 up to 15 % in 20 years. This demonstrates the importance of assisting natural coral recovery with restoration efforts, especially in coral locations that, despite environmental perturbations, have proven to be resilient and may become coral refugia areas under the current climate change scenario.

Temporal oceanographic variation using satellite imagery data in the central Mexican Pacific convergence zone

The oceanographic variation of the central Mexican Pacific (CMP) is mainly driven by the California Current and the Mexican Coastal Current, which generate a convergence zone. Little information is available regarding changes in oceanographic variables at the mesoscale level in the CMP. Therefore, this study characterized 6 oceanographic variables (sea surface temperature, chlorophyll concentration [Chl], primary productivity [PP], diffuse attenuation coefficient [K490], and particulate inorganic/organic carbon concentration [PIC, POC]) in the CMP from 2010 to 2017 and their relationships with El Niño/Southern Oscillation (ENSO). The variables were standardized to monthly pixel values of 0.08 latitude degrees, and the study area covered 48,846.48 km2. Friedman tests were used to compare the temporal variation in the variables, while Spearman correlations were used to evaluate the relationship between each variable and the Multivariate ENSO Index (MEI). A cross-correlation analysis was performed to determine the temporal lag between the oceanographic variables and the MEI. The cyclicity of the variation in the CMP was determined by spectral analysis. All variables showed significant differences between months and years. Two seasons defined by temperature were also detected: a cold season (December–June), in which high values of these variables were observed, and a warm season (July–November), in which low values of these variables were observed. No variables were correlated with the MEI; however, a 4-month time lag was identified between the variables and the MEI. The cyclicity of the variables corresponded to the cold and warm seasons. The cold phase of ENSO increased the values of PP, Chl, and K490 up to 4 times compared to those of other years. Taken together, the observed variation in oceanographic conditions makes the CMP one of the most dynamic coastal regions of the Mexican Pacific.

Cold Housing in Central Mexico: Environmental Dissatisfaction and Underheating Lowers Self-Perceived Health in Central Mexico

Despite being perceived as a warm country, winters in the Central Mexican Plateau frequently reach temperatures below zero Celsius. Prolonged exposures to low temperatures resulting in heart and respiratory morbidities are estimated to be responsible for 50% of the reported illness in the plateau, attributable primarily to the design of homes ill-suited to extreme temperatures. Consequently, there is a growing need to ensure that dwellings provide adequate indoor thermal conditions in the region. Hence, on-site sensors were used to collect temperature and relative humidity data every five minutes in 26 living rooms in the Plateau for 11 months. From these data, a subsample was determined, resulting in dwelling-level thermal comfort and health surveys on 15 homes. Computer simulations were used to investigate whether the building itself could provide thermal comfort under different retrofitting scenarios. Multiple linear regression relating the Predicted Percentage Dissatisfaction (PPD) index to self-perceived health was undertaken. Both monitored and simulated results were matched against our underheating model, finding that 92% of the homes had cold indoor environments, some even during summer. High PPD and intense levels of underheating were positive predictors of higher self-reported health problems. More self-reported health problems were correlated with both lower life satisfaction and self-worth, and with subjects’ use of more adaptive strategies against environmental dissatisfaction. Dynamic computer simulations suggested that indoor thermal environments could be improved by enforcing the non-utilised standard NOM-ENER-020, which recommends the addition of insulation on walls and roofs. These findings suggest that the cold environments within homes of the plateau influence the self-perceived physical and mental health of its population. Hence, the application of adequate measures, such as retrofitting homes with stronger standards than the existing NOM-ENER-020 are needed in place.

Weather, ultrasonic, cranial and body traits predict insect diet hardness in a Central Mexican bat community

Insectivorous bats exhibit food preferences for specific attributes in their prey. Hardness has been defined as an important prey attribute, and in some cases a limiting factor in foraging decisions for smaller compared to larger bat species. The goal of this study was to identify which factors influence the selection of prey hardness in a vespertilionid bat community. We investigated food consumed by bats by analyzing fecal samples obtained from eight bat species coexisting in a mountain ecosystem of central Mexico and correlate non-phylogenetically and phylogenetically prey hardness to weather, bat´s body, cranial and ultrasonic call structure variables. Results showed that diet of vespertilionid bats was mainly represented by Diptera, Neuroptera, Lepidoptera and Coleoptera consumption. The qualitative prey hardness index (From soft 1 to hard 5) ranked bats as: Myotis melanorhinus, Corynorhinus mexicanus, Myotis volans, Myotis californicus (< 3); Myotis velifer (< 4); Eptesicus fuscus, Idionycteris phyllotis and Myotis thysanodes (> 4.2). Prey hardness was positively correlated to minimum and mean temperatures, bat´s body weight, total and forearm lengths, cranial variables as: zygomatic breadth, mandibular length, height of the coronoid process, lower molar width, C-M3 superior and inferior rows length and upper molar width; and negatively to ultrasonic variables as total slope, call duration, low and high frequencies, band width and frequency maximum power. Considering phylogenies, prey hardness positively correlated to mandibular length, C-M3 inferior and superior rows lengths (p < 0.05). Our results showed that environmental, morphological and echolocation variables can be used as predictors of preferred insect prey in a community of vespertilionid bats.

Genetic Evidence for Indo-Western Pacific Olive Ridley Sea Turtles in Mexican Waters

The olive ridley sea turtle is predominantly an epipelagic species with no apparent migration corridors. Research in feeding areas in other sea turtle species has identified aggregations of individuals from diverse backgrounds; however, no specific feeding areas have been identified for the olive ridley. We used mtDNA control region sequencing to identify the haplotype composition of 85 olive ridley turtles (adult and immature turtles from both sexes) captured and released in Central Mexican Pacific waters. Amplified fragments of the control region (751 bp) revealed the presence of 17 haplotypes (h = 0.5877 ± 0.0622 and π = 0.001698 ± 0.001185), and 16 of them were phylogenetically grouped within the lineage of the Eastern Pacific, but the haplotype Lo37 showed close evolutionary relationships with the lineage of the East Coast of India. Lagrangian drifter data showed that West–East transport from the Indo-Pacific to the tropical Eastern Pacific might be possible through passive drift. These results highlight the importance of more genetic studies offshore and the role of the ocean currents in the migratory behavior of olive ridleys, as well as the need to establish multinational strategies for the conservation and management of the species in international waters.

In situ microplastic ingestion by neritic zooplankton of the central Mexican Pacific

Microplastics (MPs) are present across the global ocean and can be encountered by many species, including zooplankton. Although they fall within the size range of zooplankton prey, there are few studies on MPs ingestion carried out in situ. In this study, we analyzed MPs ingestion during two seasons (rainy and dry) of organisms from 5 taxonomic groups of zooplankton from two bays of the Mexican central Pacific: Manzanillo and Navidad. In total, 2643 individuals were analyzed, and of those 23 individuals contained MPs. The ingestion rate by taxonomic group was 1 MP/36 copepods (0.02), 1 MP/30 decapods–mysis (0.03), 1 MP/29 decapods–megalopa (0.03), and 1 MP/200 fish larvae (0.005). No plastics were found in chaetognaths, amphipods, or decapods–zoea. The average length of the ingested particles was 468.1 ± 113.8 μm, with a minimum of 15.6 and a maximum of 647.6 μm. All MPs >300 μm were fibers, with diameters <50 μm. Fragments were the most abundant MPs (54.2%), followed by fibers (34.2%) and spheres (11.4%). Statistical analyses showed no significant differences (p > 0.05) between the bays or seasons. Using RAMAN spectroscopy, it was possible to identify 6 different types of polymers, with poly (ethylene:propylene) being the most abundant (42.8%). This polymer is commonly used to manufacture plastic bags, ropes and fishing nets. The results confirm that certain zooplankton groups are consuming MPs and suggest that omnivorous species are more likely to ingest MPs, possibly due to their capacity for foraging flexibility and opportunistic feeding strategies. However, the ingestion of MPs cannot be attributed to a single factor; it is necessary to consider variables such as the sampling area, feeding strategy, size, and seasonality to understand the dynamics of MPs ingestion by zooplankton groups.

The invasive Australian redclaw crayfish Cherax quadricarinatus Von Martens, 1868: a new threat for biodiversity in the Sierra Gorda Biosphere Reserve, Central Mexican Plateau

The invasive Australian redclaw crayfish Cherax quadricarinatus Von Martens, 1868: a new threat for biodiversity in the Sierra Gorda Biosphere Reserve, Central Mexican Plateau

A Multivariate Study of Morphological Characters for Echinocactus horizonthalonius and E. texensis (Cactaceae) and Description of a New Subspecies, E. horizonthalonius subsp. australis

A study was conducted to ascertain the taxonomic validity of the endangered taxon Echinocactus horizonthalonius var. nicholii and whether there may be other groups of populations worthy of subspecies status within the range of the species. To test the hypothesis that individuals of E. horizonthalonius var. nicholii are morphologically distinct from those of the typical variety, a multivariate analysis was done to compare the degree of morphological variation or phenotypic plasticity of stem characters within populations to the variation among populations of E. horizonthalonius throughout its known range. Populations of E. texensis were sampled for outgroup comparison. Discriminant function analysis (DFA) assigning individuals by population showed loose groupings of geographically correlated populations. The DFA assigning individuals to regions or potential subspecific taxa indicated high percentages of correct classification for individuals within populations grouped into the Chihuahuan Desert, Sonoran Desert, and Central Mexican Plateau regions. Taxonomically, these groups correspond to E. horizonthalonius subsp. horizonthalonius (Chihuahuan Desert), E. horizonthalonius var. nicholii (Sonoran Desert), and unnamed taxon of E. horizonthalonius (Central Mexican Plateau). Because these morphological entities are correlated with regional distributions, they are placed here under subspecies, including a newly described taxon, E. horizonthalonius subsp. australis. Because no type for E. horizonthalonius could be located, a neotype is designated.

Molecular, morphometric, and spatial data analyses provide new insights into the evolutionary history of the Peromyscus boylii species complex (Rodentia: Cricetidae) in the mountains of Mexico

Peromyscus is the most speciose genus in America, which occupies almost every terrestrial habitat type. However, its taxonomy and evolutionary relationships remain unsolved in several species, one species group with these issues is the P. boylii complex. This complex consists of 11 species (P. beatae, P. boylii, P. carletoni, P. ensinki, P. greenbaumi, P. kilpatricki, P. levipes, P. madrensis, P. schmidlyi, P. simulus, and P. stephani) largely distributed in Mexico and has been taxonomically studied during the last 40 years, resulting in the description of new species, several of them from the mountains of central Mexico. In this study, we aimed to integrate molecular, morphometric, and spatial data analysis approaches to inquire into the phylogenetic relationships. To clarify the taxonomic status of the P. boylii complex, particularly for the species distributed in the central Mexican highlands where the taxonomic uncertainty is high. We performed phylogenetic and divergence time analyses based on four molecular markers for all species within the complex, we explored cranium shape and size variation in 146 individuals of continental species (P. madrensis and P. stephani excluded) using geometric morphometrics. Also, we evaluated environmental differentiation and ecological niche modeling analyses of three species endemic to the central Mexican highlands to retrieve evidence on their evolutionary history. Our results recovered one well-supported clade including all mountainous species, in which P. schmidlyi was sister to the clade composed of P. greenbaumi and P. ensinki, which diverged during the late Pleistocene. The novel morphological data allowed a better differentiation of all continental species. The discovery of new specimens for P. greenbaumi and P. ensinki improved their taxonomic knowledge, as well as delimiting their habitat and distribution, showing substantial environmental divergence with low overlapped geographical distributions; P. schmidlyi restricted to the Sierra Madre Occidental, P. ensinki to the central-west Trans-Mexican Volcanic Belt, and P. greenbaumi to the center of the Sierra Madre del Sur. We discuss the biogeographic history of these three lineages and the role of the late Pleistocene climatic oscillations on their diversification.

Genome-wide species delimitation analyses of a silverside fish species complex in central Mexico indicate taxonomic over-splitting

BackgroundDelimiting species across a speciation continuum is a complex task, as the process of species origin is not generally instantaneous. The use of genome-wide data provides unprecedented resolution to address convoluted species delimitation cases, often unraveling cryptic diversity. However, because genome-wide approaches based on the multispecies coalescent model are known to confound population structure with species boundaries, often resulting in taxonomic over-splitting, it has become increasingly evident that species delimitation research must consider multiple lines of evidence. In this study, we used phylogenomic, population genomic, and coalescent-based species delimitation approaches, and examined those in light of morphological and ecological information, to investigate species numbers and boundaries comprising the Chirostoma “humboltianum group” (family Atherinidae). The humboltianum group is a taxonomically controversial species complex where previous morphological and mitochondrial studies produced conflicting species delimitation outcomes. We generated ddRADseq data for 77 individuals representing the nine nominal species in the group, spanning their distribution range in the central Mexican plateau.ResultsOur results conflict with the morphospecies and ecological delimitation hypotheses, identifying four independently evolving lineages organized in three geographically cohesive clades: (i) chapalae and sphyraena groups in Lake Chapala, (ii) estor group in Lakes Pátzcuaro and Zirahuén, and (iii) humboltianum sensu stricto group in Lake Zacapu and Lerma river system.ConclusionsOverall, our study provides an atypical example where genome-wide analyses delineate fewer species than previously recognized on the basis of morphology. It also highlights the influence of the geological history of the Chapala-Lerma hydrological system in driving allopatric speciation in the humboltianum group.

Trypanosoma cruzi and Leishmania spp. in rodents in a peri-urban area of Central Mexico

Rodents are one of the most relevant groups of mammals involved in the process of zoonotic disease transmission. Their ability to adapt to anthropized environments allows them to come into contact with humans with often negative consequences for the latter. The present study designed to detect the presence of Trypanosoma cruzi and Leishmania spp. in rodents living in the peri-urban area of Queretaro in central Mexico.This research was carried out during two seasons of collection of wild and domestic rodents, in three localities within the peri-urban area of the state of Queretaro. These collections were carried out during the dry season of February–May 2017 and in the rainy season of August–November 2017. Samples were obtained from the tail tip, from which DNA was purified using the DNeasy Blood & Tissue Kit. End-point PCR was used for the identification of Trypanosoma cruzi and Leishmania spp.A total of 82 rodents were caught, represented in three families, six genera and seven species, of which 29 (35.3%) were positive for Trypanosoma cruzi; 13 (15.8%) for Leishmania spp.; and 12 individuals presented co-infection with both parasites (14.6%).This study confirmed the presence of Trypanosoma cruzi and Leishmania spp. in synanthropic rodents in the peri-urban area of Queretaro, where Chagas and Leishmaniosis diseases are not considered endemic. It is necessary to continue researching for the presence of vectors, as well as for the detection of diseases caused by parasites in humans and thus be able to confirm the transmission cycle of Trypanosoma cruzi and Leishmania spp. in this central Mexican city.

Comparison of fish assemblages recorded by visual census and video census

Introduction: Underwater visual censuses are the basis of many studies on fish ecology, however, a series of limitations and errors influence the traditional visual estimation of fish richness and abundance. Video techniques have been proposed to mitigate such errors, but there are few studies that compare the effectiveness of both methods. Objective: To compare the estimates obtained through the traditional census and the video census of the fish community of two localities in the central Mexican Pacific. Methods: We studied the fish community of two bays of Huatulco, Oaxaca, Mexico. We established sampling points in each bay and applied a traditional census and a diver-operated video census. We used comparison tests and analysis of similarity tests to compare richness, abundance and diversity by locality; and permutation tests for the same parameters at each sampling point. Results: Both censuses provide similar estimates regarding the richness, abundance, and diversity by locality and by sampling points. There were no statistically significant differences between traditional census and a diver-operated video census in terms of richness, abundance, and diversity. Conclusions: Video census using the diver-operated video technique can be used as a complement or as an alternative to traditional census. Its use can provide a more complete assessment, increase data acquisition, and implement long-term monitoring programs in areas where there are economic limitations for its operation.

Is informal charcoal production necessarily unsustainable? A comparison of three oak management systems in the central Mexican Sierras.

A steady increase in charcoal production as an energy source is expected (FAO, 2017). Its negative effects due to above-ground biomass removal (BSS) suggest favoring conservation (Lee and Lautenbach, 2016; Monárrez- González, et.al., 2018). However, sustainable forest management [SFM] allows considering charcoal as a renewable source of energy (Antinori and Rausser, 2010; Camou-Guerrero, et.al., 2014; Sist, et.al., 2014; Aguirre-Calderón, 2015; FAO, 2017; Ramírez, 2017). Mexican regulations focus SFM on functionality, industrialization and large scale (Antinori and Rausser, 2010; Deschamps and Madrid, 2018; Cravioto, 2019); informality is considered unsustainable due to irregular and poor management practices (Sist, et.al., 2014; Monárrez- González, et.al., 2018). We analyzed impacts of three oak management systems on tons of BSS: [1] conservation, [2] formal production, and [3] informal production; influenced by [1] advantageous (nursery), and [2] disadvantageous (drying shed) biophysical conditions. We focused on verifying the existence of differences in BSS and structure between systems and conditions. With such analysis, we reconsider the bias towards conserving and the dismissal of informality as unsustainable.

Monumentalizing metaphors: diphrasis in the murals of Tulum

At Tulum, as well as other Maya sites in the Yucatan Peninsula, mural painting traditions are related to the style and symbol-set associated with Central Mexican manuscript cultures. The murals reflect the widespread Postclassic Mesoamerican manuscript cultures lourishing from the twelfth to sixteenth centuries AD, during which iconic and logosyllabic scripts were used in the construction of regionally distinct manuscript forms. The murals at Tulum relate to manuscript culture not only in their style and symbol set, but also in their use of metaphorical dualisms, in which significant iconic elements are contrasted as an indicator of a more abstract concept. Recognizing metaphorical juxtaposition as an underlying principle of Mesoamerican ritual language, this paper discusses the process by which manuscripts become monuments and considers the sacred metaphors painted on the temples of Tulum as mechanisms for reinforcing political power.

Coral performance and bioerosion in Central Mexican Pacific reef communities

Coral performance and bioerosion in Central Mexican Pacific reef communities

Symbiont-coral relationship in the main reef building scleractinians of the Central Mexican Pacific

Symbiont-coral relationship in the main reef building scleractinians of the Central Mexican Pacific