The Mexican highlands are areas of high biological complexity where taxa of Nearctic and Neotropical origin and different population histories are found. To gain a more detailed view of the evolution ...of the biota in these regions, it is necessary to evaluate the effects of historical tectonic and climate events on species. Here, we analyzed the phylogeographic structure, historical demographic processes, and the contemporary period, Last Glacial Maximum (LGM) and Last Interglacial (LIG) ecological niche models of Quercus castanea, to infer the historical population dynamics of this oak distributed in the Mexican highlands. A total of 36 populations of Q. castanea were genotyped with seven chloroplast microsatellite loci in four recognized biogeographic provinces of Mexico: the Sierra Madre Occidental (western mountain range), the Central Plateau, the Trans‐Mexican Volcanic Belt (TMVB, mountain range crossing central Mexico from west to east) and the Sierra Madre del Sur (SMS, southern mountain range). We obtained standard statistics of genetic diversity and structure and tested for signals of historical demographic expansions. A total of 90 haplotypes were identified, and 29 of these haplotypes were restricted to single populations. The within‐population genetic diversity was high (mean hS = 0.72), and among‐population genetic differentiation showed a strong phylogeographic structure (NST = 0.630 > GST = 0.266; p < .001). Signals of demographic expansion were identified in the TMVB and the SMS. The ecological niche models suggested a considerable percentage of stable distribution area for the species during the LGM and connectivity between the TMVB and the SMS. High genetic diversity, strong phylogeographic structure, and ecological niche models suggest in situ permanence of Q. castanea populations with large effective population sizes. The complex geological and climatic histories of the TMVB help to explain the origin and maintenance of a large proportion of the genetic diversity in this oak species.
High genetic diversity in Mexican oaks. High phylogeographic structure in a widespread oak species.
Abstract
Lower Central America is an important area to study recent population history and diversification of Neotropical species due to its complex and dynamic geology and climate. Phylogeographic ...studies in this region are few in comparison with other regions and even less for tree species. The aim of the present study was to characterize the phylogeographic structure in 2 partially co-distributed endemic oak species (Quercus costaricensis and Q. bumelioides) of the Costa Rican mountains using chloroplast short sequence repeats (cpSSRs), and to test for the effect of geological and palaeoclimatic processes on their population history. Genetic diversity and structure, haplotype networks, patterns of seed-mediated gene flow and historical demography were estimated for both species. Results suggested contrasting patterns. Quercus costaricensis exhibited high values of genetic diversity, a marked phylogeographic structure, a north-to-south genetic diversity gradient and evidence of a demographic expansion during the Quaternary. Quercus bumelioides did not show significant genetic structure and the haplotype network and historical demography estimates suggested a recent population expansion probably during the Pleistocene-Holocene transition. The phylogeographic structure of Q. costaricensis seems to be related to Pleistocene altitudinal migration due to its higher altitudinal distribution. Meanwhile, historical seed-mediated gene flow through the lower altitudinal distribution of Q. bumelioides may have promoted the homogenization of genetic variation. Population expansion and stable availability of suitable climatic areas in both species probably indicate that palaeoclimatic changes promoted downwards altitudinal migration and formation of continuous forests allowing oak species to expand their distribution into the Panamanian mountains during glacial stages.
Due to a complex geological and biotic history, the Isthmus of Tehuantepec (IT), has been long recognized as a driver for the evolutionary divergence of numerous lowland and highland taxa. Widely ...distributed in the lowlands of the American continent, the White-Tipped Dove (Leptotila verreauxi) is a polytypic species with 13 recognized subspecies. Four of these have been recorded in Mexico, and the distribution of three abuts at the IT, suggesting a contact zone. To estimate phylogenetic patterns, divergence times and genetic differentiation, we examined two mtDNA (ND2 and COI) and one nDNA (β-fibint 7) markers. We also used correlative ecological niche models (ENM) to assess whether ecological differences across the IT may have acted as a biogeographical boundary. We estimated paleodistributions during the Middle Holocene, Last Glacial Maximum and Last Interglacial, to evaluate the influence of climate changes on the distribution and demographic changes. Our results showed genetically distinct lineages that diverged approximately 2.5 million years ago. Climatic and ecological factors may have played a dual role in promoting differentiation, but also in the formation of a secondary contact zone in the southern IT. Our ecological niche comparisons indicated that the ecological niche of sympatric lineages at the IT are not identical, suggesting niches divergence; in addition, environmental niche models across the region indicated no abrupt biogeographic barriers, but the presence of regions with low suitability. These results suggest that genetic differentiation originated by a vicariant event probably related to environmental factors, favored the evolution of different ecological niches. Also, the absence of a biogeographic barrier but the presence of less suitable areas in the contact regions, suggest that secondary contact zones may be also maintained by climatic factors for the eastern group, but also by biotic interactions for the western group.
A survey was done to estimate margay abundance and activity in the context of high forest loss rates from avocado plantations for the temperate forest region of Michoacán state. Camera trap surveys ...were conducted from November 2015 to April 2020, recording 21 Margay detections of seven individuals. The capture rate ranged from 0.09 to 0.83 records/100 trap nights. The mean temporal density was 0.12 ind./km
, with an activity peak between 04:00 and 05:00 h. The Margay could serve as indicator species for restoration and forest conservation initiatives.
While hybridization and introgression can have a strong adaptive importance, it can impede divergence of species.
Quercus magnoliifolia
and
Q. resinosa
are two endemic oak species distributed across ...the Mexican highlands. These species diverged ecological and morphologically; however, no nuclear genetic differentiation is evident. In this study, we determined the mechanisms that shape patterns of genetic variation and establish the role of migration and hybridization in the evolutionary history of these two oak species. To do this, Bayesian approaches were used for inference on migration rates and directionality and timing of divergence between species using chloroplast microsatellites. We then integrated species distribution models to infer the geographic distribution of
Q. magnoliifolia
and
Q. resinosa
during Last Interglacial, Last Glacial Maximum, and Mid-Holocene time frames. We failed in distinguishing a unique genetic composition for each species. Chloroplast differentiation was more congruent with geography than the taxonomic status of each species. Our study revealed that after the divergence (
c
. 10 Mya) of these two oak species, high rates of introgression took place at the end of the Pleistocene. Furthermore, past distribution models predicted that
Q. magnoliifolia
and
Q. resinosa
have likely been in sympatry presumable since Last Glacial Maximum and
Q. resinosa
probably expanded geographically towards its current distribution around Mid-Holocene. This expansion was supported by testing migration models, suggesting recent establishment of
Q. resinosa
to the north of Trans-Mexican Volcanic Belt. We hypothesized that after
Q. magnoliifolia
and
Q. resinosa
diverged, colonization events followed by hybridization between oaks and long-distance seed dispersal occurred, explaining the present-day patterns of distribution of chloroplast diversity. We propose that divergence of species remains mainly on loci under natural selection, providing evidence on the “porous” nature of species boundaries among oaks.
The northern Neotropical region is characterized by a heterogeneous geological and climatic history. Recent studies have shown contrasting patterns regarding the role of geographic elements as ...barriers that could have determined phylogeographic structure in various species. Recently, the phylogeography and biogeography of
Quercus
species have been studied intensively, and the patterns observed so far suggest contrasting evolutionary histories for Neotropical species in comparison with their Holarctic relatives. The goal of this study was to describe the phylogeographic structure of two Neotropical oak species (
Quercus insignis
and
Quercus sapotifolia
) in the context of the geological and palaeoclimatic history of the northern Neotropics. Populations through the distribution range of both species were collected and characterized using nine chloroplast DNA microsatellite loci. Both oak species showed high levels of genetic diversity and strong phylogeographic structure. The distribution of genetic variation in
Q. insignis
suggested an influence of two major barriers, the Isthmus of Tehuantepec and the Nicaraguan Depression, while
Q. sapotifolia
exhibited a genetic structure defined by the heterogeneity of the Chortis highlands. The haplotype networks of both species indicated complex histories, suggesting that colonization from the Sierra Madre de Chiapas to central Mexico and from the north of the Nicaraguan Depression to the Costa Rican mountains may have occurred during different stages, and apparently more than one time. In conclusion, the phylogeographic structure of Neotropical oak species seems to be defined by a combination of geological and climatic events.
We studied populations of Stenocereus pruinosus throughout Mexico, a species important for its edible fruit. The Tehuacán Valley is setting of ancient and the currently most active management of S. ...pruinosus; we hypothesized Tehuacán as the original area of domestication of S. pruinosus and expected to find there its highest genetic variation and original source of genes of cultivated plants. Through nuclear microsatellite loci we studied spatial distribution of genetic variation and population differentiation. We sampled wild and managed populations of the Central-western (Tehuacán, Central Valleys and Tehuantepec, Oaxaca), north-eastern (Huasteca) and south-eastern (Chiapas) regions. Differences among regions and populations were compared through homogeneity and exact test for F IS , AMOVA, Bayesian analysis, and genetic barriers. A niche analysis allowed corroborating taxonomic identity of populations. The highest genetic diversity was in Tehuantepec (H E = 0.841), decreasing towards the extremes of distribution (H E = 0.242 in Huasteca, H E = 0.254 in Chiapas). Genetic structure is significantly high among populations and regional groups, differentiating one group formed by northern and southern populations and other formed by populations of the Central-western region. Differences among groups suggested that populations from Huasteca could be species different to S. pruinosus, but the niche analysis did not support such hypothesis. Populations from Tehuantepec were different but genetically interconnected with those of Tehuacán. Tehuantepec is the main reservoir of genetic diversity of wild populations of S. pruinosus, but Tehuacán is the principal current area of domestication of S. pruinosus and probably where its domestication originated. Conclusions would be stronger by analyzing DNAc lineages.
Mixed bird flocks are groups of individuals from different species that travel and forage together. Such groups are common in several bird communities around the world. We present species composition ...and activity patterns of mixed bird flocks in a region of the Central Andes of Colombia. We compared the number of species per flock, as well as the number of flocks among 3 different habitats. We tested hypotheses concerning the flocks daily activity and the co-occurrences of species within them. We recorded 75 species, and the species number per flock varied from 4 to 21. Our data suggest that habitat affects the number of flocks but not their species number, and that the activity of flocks is similar throughout the day. In addition, the association of birds in flocks is affected by interspecific facilitation, with some species co-occurrences found more times than expected by chance. We hypothesize that some tanager species could have a role in flock cohesion. We witnessed 2 predator attacks upon flocks, a number of agonistic interactions among flock members, and squirrels following bird flocks. Our results meet some general patterns described for mixed bird flocks.
Se presenta una revisión de las investigaciones en el campo de la Ecología Molecular en México. Entre 1990 y 2016 se identificaron 656 artículos científicos relacionados. Los temas mejor ...representados son la genética de poblaciones (35.3% de los estudios) y la filogeografía (30.3%), mientras que los campos emergentes de la Ecología Molecular, como la genómica del paisaje, la ecología trófica basada en secuencias de ADN y el análisis del parentesco y la conducta, estuvieron poco representados. Los sistemas más estudiados han sido los animales (58.5%) y las plantas (32.5%), mientras que otros organismos como hongos, protozoarios y bacterias han recibido mucho menos atención. En general, se observa un desarrollo considerable de la Ecología Molecular en nuestro país. Sin embargo, para continuar esta tendencia será necesario incorporar extensivamente los avances tecnológicos como la secuenciación de nueva generación y la bioinformática, así como incursionar en las áreas emergentes de esta disciplina.
A review of studies on Molecular Ecology in Mexico is presented. Between 1990 and 2016, we identified 656 published studies on Molecular Ecology. The best represented subject areas were population genetics (35.3% of the studies) and phylogeography (30.3%), while emergent fields in molecular ecology, such as landscape genomics, DNA-based trophic ecology, and kinship, parentage and behavior were scarcely represented. Most frequently studied systems were animals (58.5%) and plants (32.5%), while other organisms such as fungi, protozoa and bacteria have received much less attention. In general, a considerable development of Molecular Ecology is observable in our country. However, for this tendency to continue it will be necessary to incorporate more extensively technological advances such as next generation sequencing and bioinformatics, as well as to venture into the emergent areas of the discipline.
Mixed bird flocks are groups of individuals from different species that travel and forage together. Such groups are common in several bird communities around the world. We present species composition ...and activity patterns of mixed bird flocks in a region of the Central Andes of Colombia. We compared the number of species per flock, as well as the number of flocks among 3 different habitats. We tested hypotheses concerning the flocks daily activity and the co-occurrences of species within them. We recorded 75 species, and the species number per flock varied from 4 to 21. Our data suggest that habitat affects the number of flocks but not their species number, and that the activity of flocks is similar throughout the day. In addition, the association of birds in flocks is affected by interspecific facilitation, with some species co-occurrences found more times than expected by chance. We hypothesize that some tanager species could have a role in flock cohesion. We witnessed 2 predator attacks upon flocks, a number of agonistic interactions among flock members, and squirrels following bird flocks. Our results meet some general patterns described for mixed bird flocks.Las bandadas mixtas de aves son grupos de individuos de diferentes especies que viajan y forrajean juntos, y son comunes en varias comunidades de aves alrededor del mundo. Presentamos la composición de especies y los patrones de actividad de las bandadas mixtas de aves en una región de la Cordillera Central de los Andes Colombianos. Comparamos el número de especies por bandada y el número de bandadas en 3 hábitats distintos. Evaluamos hipótesis relacionadas con la actividad de las bandadas durante el día y la presencia simultánea de especies en estos grupos. Observamos 75 especies, y el número de especies por bandada varió entre 4 y 21. Nuestros datos indican que el hábitat parece afectar el número de bandadas pero no su número de especies y que la actividad de las bandadas es similar durante el día. La asociación de especies en bandadas parece estar influida por facilitación intraespecífica y algunas especies se presentan simultáneamente más de lo esperado por azar. Hipotetizamos que algunas tangaras pueden tener un papel en la cohesión de las bandadas. Observamos 2 ataques de depredadores, así como varias interacciones hostiles entre miembros de las bandadas y la participación de ardillas. Nuestros resultados se ajustan a ciertos patrones descritos para las bandadas mixtas.
PDF
