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The animal gut microbiota is strongly influenced by environmental factors that shape their temporal dynamics. Although diet is recognized as a major driver of gut microbiota variation, dietary patterns have seldom been linked to gut microbiota dynamics in wild animals. Here, we analysed the gut microbiota variation between dry and rainy seasons across four Sceloporus species (S. aeneus, S. bicanthalis, S. grammicus and S. spinosus) from central Mexico in light of temporal changes in diet composition. The lizard microbiota was dominated by Firmicutes (now Bacillota) and Bacteroidota, and the closely related species S. aeneus and S. bicanthalis shared a great number of core bacterial taxa. We report species‐specific seasonal changes in gut microbiota diversity and composition: greater alpha diversity during the dry compared to the rainy season in S. bicanthalis, the opposite pattern in S. aeneus, and no seasonal differences in S. grammicus and S. spinosus. Our findings indicated a positive association between gut bacterial composition and dietary composition for S. bicanthalis and S. grammicus, but bacterial diversity did not increase linearly with dietary richness in any lizard species. In addition, seasonality affected bacterial composition, and microbial community similarity increased between S. aeneus and S. bicanthalis, as well as between S. grammicus and S. spinosus. Together, our results illustrate that seasonal variation and dietary composition play a role in shaping gut microbiota in lizard populations, but this is not a rule and other ecological factors influence microbiota variation. [ABSTRACT FROM AUTHOR]

Two new records of gomphotheriid proboscideans, one identified as Rhynchotherium and the other as Cuvieronius, are reported in México. Both records are in the southwesternmost points of their known distributional range. The remains of both genera consist of molars and tusks. Their measurements were compared with data available from the literature and collection specimens. The molar index of Rhynchotherium shows statistical differences between m2 and M2, and m3 and M3. However, differences between the m3 from both genera are not statistically significant, despite slight morphological differences. This suggests that metric and morphological information should be included for a reliable identification of isolated molars and, if available, any other data of the associated tusk. All known records relating to both genera suggest that they found southwestern México favorable for use as a dispersal corridor to South America, likely due to the region's tropical or subtropical climate. However, some distributional gaps in central México need to be resolved for Rhynchotherium. There are also important populations of Cuvieronius in central México, and preliminary information suggests that they occupied at least parts of eastern México, as well. [ABSTRACT FROM AUTHOR]

Most of the Pleistocene species of Equus from Mexico have been considered to be grazers and highly specialized on the basis of their craniodental features, and therefore analogous to their modern relatives from an ecological point of view. Here we rely on dental wear analyses of three different species of Rancholabrean Equus that exhibit differences in limb proportions and body mass and occurred in two different habitats in order to test whether species exhibited more heterogeneous dietary capabilities compared to modern horses. Overall, and although our analyses show grazer lifestyles, there is a significant degree of dietary variability among taxa according to the site, apparently as a response to differences in climate and environmental conditions, with intermediate feeding preferences on the basis of the last items consumed during the last days prior to death in some cases. Accordingly, fossil Equus might have been more sensitive to different environments and diverse in terms of dietary preferences, thus incorporating a higher proportion of browse vegetation if necessary, than their modern relatives. These results highlight the dietary plasticity of certain fossil species, and evidence the caution that should be paid when reconstructing the ecology of fossil species using their modern relatives as analogs. [ABSTRACT FROM AUTHOR]

The Gomphotheriidae family belongs to the Proboscidea order. Gomphotheres were elephant-like mammals whose representatives inhabited North America from the Middle Miocene to the late Pleistocene. In this work, a gomphothere remains from Santiago Tepeticpac (Tlaxcala, Mexico) are described. The comparative study with other Proboscidea, mainly from different localities of Mexico and South America, mostly Argentina and Brazil, allowed to identify them as Cuvieronius genus. The microwear signature together with carbon and oxygen stable isotopes showed that this animal was a mixer feeder and inhabited open zones with patches of wooded flora. These analyses also indicated the presence of high abrasiveness components and C 4 plants (grasslands) and medium to low wearing elements as well as C 3 vegetation (forest) in the site. The strontium isotopic signature implies that this gomphothere lived in the Puebla-Tlaxcala Valley. The paleoenvironmental inferences would show regional conditions. • We report a multidisciplinary study of a Cuvieronius hyodon ′s skull and tusks from the state of Tlaxcala, Mexico. • Diet analyses showed that this animal was a mixed feeder and inhabited open zones with patches of wooden flora. • The strontium isotopic ratios suggested that this gomphothere used to live in the Puebla-Tlaxcala Valley. • We describe a detailed work of conservation and anatomical reconstruction of the gomphothere skull. [ABSTRACT FROM AUTHOR]

The use of radiogenic strontium (87Sr/86Sr) and stable oxygen isotopes (δ18O) in macrofossil remains has impacted paleomobility studies. We performed 87Sr/86Sr and δ18O analyses in dental enamel of three Rancholabrean horse species (E. cedralensis , E. conversidens and E. mexicanus) and in sediments and rocks from two fossil sites in west-central Mexico (La Cinta-Portalitos, and La Piedad-Santa Ana). The aim was to obtain information on geographical origin (on a regional and a local scale) and the mobility behavior of the horses, as well as to investigate the implications for paleoecological studies of large mammals. Enamel 87Sr/86Sr values show that the possible geographical origin of fossil horse populations from both sites is the west-central Trans-Mexican Volcanic Belt (TMVB). This was additionally corroborated by similar δ18O signatures for species and sites indicating that horses drank water with the same isotopic composition and lived in the same geographical region. To the north, 87Sr/86Sr from TMVB back-arc volcanic and carbonate rocks are more enriched in radiogenic strontium. To the south, Sierra Madre del Sur igneous rocks are generally more depleted in radiogenic 87Sr. Therefore, there is no evidence for horse migration or dispersion from these areas. However, in the case of the La Piedad-Santa Ana site, differences in 87Sr/86Sr between sediments and enamel could result from non-local residence within the TMVB. On the other hand, in La Cinta-Portalitos, similar strontium signatures of sediments and enamel indicate strictly local residence. We also detected that small differences in 87Sr/86Sr between the three species could have resulted from different residential mobility behavior. Finally, we suggest that populations of sympatric fossil horse species might have a similar geographic origin on a regional scale, but locally different, which might possibly be related to a mobility behavior, as exhibited by extant species of equids. • Sr and O variation in enamel from fossil horses is useful to inference geographic origin and home range. • The relation between mobility patterns, Sr and O in fossil horses is more difficult to understand than assumed. • Results suggest that the geographical origin of fossil horses is the west-central of the Trans-Mexican Volcanic Belt. • There is no evidence for horse migration or dispersion from other morphotectonic provinces. • Fossil horses might have a similar geographic origin but a different local residence and mobility behavior. [ABSTRACT FROM AUTHOR]

The population genetics of Triatoma dimidiata haplogroups was analyzed at landscape and sub-regional scales in Chiapas and regional level across the Mexican Neotropics, and phylogeography of the complex was re-analyzed across its complete geographic range. Two contiguous fragments of the ND4 gene were analyzed due to bias from differential haplogroup specificity using a previously designed sequence. At both landscape (anthropic modification gradient) and regional (demographic, fragmentation, biogeographic, climate) scales, lowest T. dimidiata genetic diversity occurs where there is greatest historical anthropic modification, and where T. cruzi infection prevalence is significantly highest. Trypanosoma cruzi prevalence was significantly higher than expected in haplogroups 1 and 3, while lower than expected in haplogroup 2. There was also a significant difference of DTUI and DTUVI infection frequencies in both haplogroups 1 and 3, while no difference of either in haplogroup 2. All haplogroups from the Mexican Neotropics had moderate to high haplotype diversity, while greatest genetic differentiation was between haplogroups 1 and 3 (above FST = 0.868, p < 0.0001). Divergence of the complex from the MRCA was estimated between 0.97 MYA (95% HPD interval = 0.55-1.53 MYA) and 0.85 MYA (95% HPD interval = 0.42-1.5 MYA) for ND4A and both concatenated fragments, respectively, with primary divergence from the MRCA of haplogroups 2 and 3. Effective population size for Mexican haplogroups 1 and 2 increased between 0.02 and 0.03 MYA. This study supports previous ecological niche evidence for the complex´s origin surrounding the Tehuantepec Isthmus, and provides evidence for recent divergence of three primary dimidiata haplogroups, with differential T. cruzi infection frequency and DTU specificity, important components of vector capacity., Competing Interests: The authors have declared that no competing interests exist.