L. Eguiarte | UNAM Universidad Nacional Autónoma de México (original) (raw)

Papers by L. Eguiarte

Molecular Phylogenetics and Evolution, 2018

A B S T R A C T Arid biomes are particularly prominent in the Neotropics providing some of its mo... more A B S T R A C T Arid biomes are particularly prominent in the Neotropics providing some of its most emblematic landscapes and a substantial part of its species diversity. To understand some of the evolutionary processes underlying the speciation of lineages in the Mexican Deserts, the diversification of Fouquieria is investigated, which includes eleven species, all endemic to the warm deserts and dry subtropical regions of North America. Using a phylogeny from plastid DNA sequences with samples of individuals from populations of all the species recognized in Fouquieria, we estimate divergence times, test for temporal diversification heterogeneity, test for geographical structure, and conduct ancestral area reconstruction. Fouquieria is an ancient lineage that diverged from Polemoniaceae ca. 75.54 Ma. A Mio-Pliocene diversification of Fouquieria with vicariance, associated with Neogene orogenesis underlying the early development of regional deserts is strongly supported. Test for temporal diversification heterogeneity indicates that during its evolutionary history, Fouquieria had a drastic diversification rate shift at ca.12.72 Ma, agreeing with hypotheses that some of the lineages in North American deserts diversified as early as the late Miocene to Pliocene, and not during the Pleistocene. Long-term diversification dynamics analyses suggest that extinction also played a significant role in Fouquieria's evolution, with a very high rate at the onset of the process. From the late Miocene onwards, Fouquieria underwent substantial diversification change, involving high speciation decreasing to the present and negligible extinction, which is congruent with its scant fossil record during this period. Geographic phylogenetic structure and the pattern of most sister species inhabiting different desert nucleus support that isolation by distance could be the main driver of speciation.

Antonie van Leeuwenhoek, 2011

At the desert oasis of Cuatro Ciénegas in Coahuila, México, more than 300 oligotrophic pools can ... more At the desert oasis of Cuatro Ciénegas in Coahuila, México, more than 300 oligotrophic pools can be found and a large number of endemic species of plants and animals. The most divergent taxa of diatoms, snail and fishes are located in the Churince hydrological system, where we analyzed the local diversification of cultivable Firmicutes and Actinobacteria. The Churince hydrological system is surrounded by gypsum dunes and has a strong gradient for salinity, temperature, pH and dissolved oxygen. In August 2003, surface water samples were taken in 10 sites along the Churince system together with the respective environmental measurements. 417 thermo-resistant bacteria were isolated and DNA was extracted to obtain their BOX-PCR fingerprints, revealing 55 different patterns. In order to identify similarities and differences in the diversity of the various sampling sites, an Ordination Analysis was applied using Principal Component Analysis. This analysis showed that conductivity is the environmental factor that explains the distribution of most of the microbial diversity. Phylogenetic reconstruction from their 16S rRNA sequences was performed for a sample of 150 isolates. Only 17 sequences had a 100% match in the Gene Bank (NCBI), representing 10 well known cosmopolitan taxa. The rest of the sequences cluster in 22 clades for Firmicutes and another 22 clades for Actinobacteria, supporting the idea of high diversity and differentiation for this site.

Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology, 2002

Our results show that experimental evolution mimics evolution in nature. In particular, only 1000... more Our results show that experimental evolution mimics evolution in nature. In particular, only 1000 generations of periodic recombination with immigrant genotypes is enough for linkage disequilibrium values in experimental populations to change from a maximum linkage value to a value similar to the one observed in wild strains of E. coli. Our analysis suggests an analogy between the recombination experiment and the evolutionary history of E. coli; the E. coli genome is a patchwork of genes laterally inserted in a common backbone, and the experimental E. coli chromosome is a patchwork where some sites are highly prone to recombination and others are very clonal. In addition, we propose a population model for wild E. coli where gene flow (recombination and migration) are an important source of genetic variation, and where certain hosts act as selective sieves; i.e., the host digestive system allows only certain strains to adhere and prosper as resident strains generating a particular microbiota in each host. Therefore we suggest that the strains from a wide range of wild hosts from different regions of the world may present an ecotypic structure where adaptation to the host may play an important role in the population structure.

The Botanical Review, 2013

Mexico is a megadiverse country, but less than 54 % of its original vegetation still remains. In ... more Mexico is a megadiverse country, but less than 54 % of its original vegetation still remains. In particular Mexican deserts and arid and semiarid ecosystems harbor a large number of endemic taxa, and the genus Agave is an outstanding example. Agave is one of the largest genera of the Mexican flora, including a total estimated number of 200 species, 74 % of them endemic to the country. Agave is also one of the Mexican plant genera with more population genetic studies. We describe here studies in 22 Agave species using different genetic markers. For the genus we found on average a high level of genetic variation, H s =0.19, and a low genetic differentiation, F st =0.15. We identify some species that should be subject to special conservation genetic efforts, in particular the endangered A. victoriae-reginae and both wild populations and landraces of A. angustifolia, including the cultivated A. tequilana. Resumen Aunque México es un país megadiverso, actualmente permanece menos del 54 % de su vegetación original. Los desiertos y ecosistemas áridos y semiáridos del país contienen un número muy alto de taxa endémicos, y el género Agave es un ejemplo notable. Agave es uno de los géneros con más especies de la flora Mexicana, incluyendo un total estimado de 200, 74 % de ellas endémicas al país. También es uno de los géneros Mexicanos de plantas con mayor número de estudios de genética de poblaciones. En este artículo describimos estudios en 22 especies de Agave usando diferentes marcadores genéticos. El género en promedio tiene altos niveles de variación genética, H s =0.19, y una baja diferenciación, F st =0.15. Identificamos especies donde debe hacerse un esfuerzo especial en relación a su genética de la conservación, en particular A. victoriae-reginae, una especie amenazada y A. angustifolia tanto a sus poblaciones silvestres, como a sus variedades cultivadas incluyendo a A. tequilana.

Se describen los patrones de actividad de los visitantes a las inflorescencias de 3 especies de A... more Se describen los patrones de actividad de los visitantes a las inflorescencias de 3 especies de Agave: Agave difformis, A. garciae-mendozae y A. striata en distintas localidades de la Barranca de Metztitlán, Hidalgo, México. Se define el posible papel de estos visitantes en el proceso de polinización, ya sea como ladrones de polen o néctar, o como polinizadores primarios o secundarios, estos últimos visitan menos flores y/o lo hacen de manera ineficiente. Se filmó la actividad de visitantes durante 24 h continuas en 5 inflorescencias. Se encontraron los siguientes grupos de visitantes: esfíngidos, murciélagos, abejas y colibríes. Los horarios de mayor actividad en las 3 especies de Agave se registraron durante la noche, entre las 21:00 y 03:00 h. La presencia de visitantes diurnos (abejas y colibríes) en las inflorescencias abre la posibilidad de que estos también actúen como polinizadores. Los polinizadores clasificados como primarios fueron los murciélagos nectarívoros Leptonycteris yerbabuenae, L. nivalis y Choeronycteris mexicana. El polinizador secundario más común fue el esfíngidos Erinnyis ello. El principal ladrón de polen y néctar fue la abeja europea, Apis mellifera, en A. striata, aunque tiene las flores más pequeñas; A. mellifera podría ser considerada como polinizador secundario. Derechos Reservados © 2015 Universidad Nacional Autónoma de México, Instituto de Biología. Este es un artículo de acceso abierto distribuido bajo los términos de la Licencia Creative Commons CC BY-NC-ND 4.0. Abstract Activity patterns of inflorescence visitors are described for 3 species of Agave: Agave difformis, A. garciae-mendozae and A. striata from different sites at Barranca de Metztitlán, Hidalgo, Mexico. The potential role of the visitors in the pollination process was defined: pollen or nectar robbers, or as primary or secondary pollinators, secondary if they visit less flowers or do so in an inefficient way. Visitor's activity was recorded for 24 consecutive hours on 5 inflorescences. The visitors were from the following groups: hawkmoths, bats, bees and hummingbirds. The peak of the activity in the 3 Agave species was registered between 21:00 to 03:00 h. In some cases, diurnal visitors (bees and hummingbirds) could also be pollinators. The primary pollinators were the nectar feeding bats Leptonycteris yerbabuenae, L. nivalis, and Choeronycteris mexicana. The most common secondary pollinator was the hawkmoth Erinnyis ello. The main pollen and nectar robber was the European honey bee, Apis mellifera, however, A. mellifera could also be considered as a secondary pollinator for A. striata, because this species

Bats are the main pollinators and seed dispersers of Stenocereus thurberi, a xenogamous columnar ... more Bats are the main pollinators and seed dispersers of Stenocereus thurberi, a xenogamous columnar cactus of northwestern Mexico and a good model to illustrate spatial dynamics of gene flow in long-lived species. Previous studies in this cactus showed differences among populations in the type and abundance of pollinators, and in the timing of flowering and fruit-ing. In this study we analyzed genetic variability and population differentiation among populations. We used three primers of ISSR to analyze within and among populations genetic variation from eight widely separated populations of S. thurberi in Sonora, Mexico. Sixty-six out of 99 of the ISSR bands (P = 66.7%) were polymorphic. Total heterozygosity for all populations sampled revealed high genetic diversity (H sp = 0.207, H BT = 0.224). The AMOVA showed that most of the genetic variation was within populations (80.5%). At the species level, estimates of population differentiation, θ = 0.175 and θ B = 0.194, indicated moderate gene flow among populations. The absence of a significant correlation between genetic and geographic distances indicated little isolation by geographic distance. The large genetic variation and diversity found in S. thurberi is consistent with its open reproductive system and the high mobility of bats, a major pollinator. However, small changes in number or kind of pollinators and seed dispersal agents, in the directionality of migratory routes, and/or in the timing of flowering and fruiting among populations, can critically affect gene flow dynamics.

American Journal of Botany 101(4): 730-736. 2014. J. Gasca for help in analyzing data; Carolyn Br... more American Journal of Botany 101(4): 730-736. 2014. J. Gasca for help in analyzing data; Carolyn Brown and Kendra Shannon from UNAM, Canada, who reviewed the redaction of this manuscript. The authors thank J. P. Jaramillo-Correa for his helpful comments on this manuscript and A. Schnabel, M. Moore and an anonymous reviewer for very useful comments on an earlier version of the manuscript. Leaf samples were collected under permission SGPA/DGVS/08578/12 of the SEMARNAT. The authors thank A. de Nova for the F. purpusii and F. columnaris leaf samples.

Journal of …, Jan 1, 1999

1 To assess the eect of annual environmental variability on the long-term population dynamics of ... more 1 To assess the eect of annual environmental variability on the long-term population dynamics of the invasive woody perennial Prosopis glandulosa var. torreyana (honey mesquite), we employed elasticity analyses of annual, mean and periodic matrix models. Growth, survival and reproduction were recorded for 1306 individuals in a 1-ha plot over a 4-year period. The volume of each individual was estimated, and transition matrices with nine size classes were constructed. Standard matrix analysis was performed, and the relative importance of individual life-cycle components to changes in the ®nite rate of population increase (l) was determined.

Plant Ecology, Jan 1, 2004

Nectar production in angiosperms is considered to represent a reproductive cost, and has been ass... more Nectar production in angiosperms is considered to represent a reproductive cost, and has been associated with a decrease in fruit set or an overall decrease in the energetic budget of the plant. Populations of Prosopis glandulosa var. torreyana ͑honey mesquite͒ are a suitable system to evaluate the demographic costs of nectar production, as populations are composed of a 1:1 proportion of nectarful to nectarless individuals. The study was carried out in a population of 404 individuals of Prosopis g1andulosa var. torreyana found in an area with differing water availability in the Southern Chihuahuan Desert. The possible costs of nectar production were assessed on 1212 shoots of the honey mesquite that were tagged in 1994 and followed until 1998. We used two methods of analysis to describe the effect of nectar production on modular population dynamics: matrix analysis and loglinear models. Water availability and the varying environmental conditions affected plant growth, but nectar production did not have an effect on the demographic parameters we measured. The values of did not differ between nectar morphs and the only important effects we detected were the year to year variation in precipitation and microclimate differences at each site. Furthermore, the elasticity of each demographic process ͑growth, fecundity, retrogression and stasis͒ between nectar morphs did not differ. The log-linear models suggested a similar pattern but could discriminate the importance of each factor ͑nectar morph, year and site͒ on module fate. We were not able to detect a demographic cost of nectar production in the honey mesquite. The absence of a demographic response could be due to the negligible cost of producing nectar for this species or that the resources allocated for growth are different from those allocated for reproduction. Our results suggest that the modular fates of mesquites are mainly determined by environmental factors.

It is still an open question as to whether genome size (GS) variation is shaped by natural select... more It is still an open question as to whether genome size (GS) variation is shaped by natural selection. One approach to address this question is a population-level survey that assesses both the variation in GS and the relationship of GS to ecological variants.

… Journal of Botany, Jan 1, 1999

Populations of Prosopis glandulosa var. torreyana in the Chihuahuan desert have a fixed dimorphic... more Populations of Prosopis glandulosa var. torreyana in the Chihuahuan desert have a fixed dimorphic system of nectar production in which half the individuals produce nectar (are nectarful) and the other half are nectarless. We analyzed the impact of nectar production on different estimates of fitness, comparing nectarful against nectarless individuals in size, mating system, seed traits, and fruit set in a 1-ha scrubland. Of the reproductive individuals (358), 46% were nectarful and 54% were nectarless. Neither tree size nor flowering phenology differed between nectar morphs. Fixation indices (F) for both progeny (F ϭ Ϫ0.2) and adults (F ϭ Ϫ0.45) were negative, and high heterozygosities were found in adults and progeny (H ϭ 0.45). No differences were found between nectar morphs for F, H, and single (t s ϭ 1.1) and multilocus (t m ϭ 1.03) outcrossing rates. Controlled pollinations showed differences between selfing and control treatments with no differences between nectar morphs. Nectarless individuals produced significantly more pollen grains than did nectar producers, but all other measured floral traits showed no differences. Nectarful trees were visited by pollinators 21 times more often and had a significantly higher overall fruit set than did nectarless trees. No differences between nectar morphs in seed mass or in percentage seed germination were found, but heavier seeds tended to have higher heterozygosities. Both morphs had similar success as females, but nectarless trees had ϳ7% higher male function. We discuss three possible scenarios for the evolution of the fixed dimorphism in nectar production, two involving unstable phases (substitution of one morph by the other, and evolution towards dioecy) and one stable scenario (maintenance of the dimorphic system).

American Journal of Botany, 2011

Journal of Ecology, Dec 24, 2001

Summary 1 To assess the effect of annual environmental variability on the long-term population dy... more Summary 1 To assess the effect of annual environmental variability on the long-term population dynamics of the invasive woody perennial Prosopis glandulosa var. torreyana (honey mesquite), we employed elasticity analyses of annual, mean and periodic matrix models. Growth, survival and reproduction were recorded for 1306 individuals in a 1-ha plot over a 4-year period. The volume of each individual was estimated, and transition matrices with nine size classes were constructed. Standard matrix analysis was performed, and the ...

PREMISE OF THE STUDY: Genetic data suggest that three lineages of Phragmites australis are found ... more PREMISE OF THE STUDY: Genetic data suggest that three lineages of Phragmites australis are found in North America: the Native North American lineage, the Gulf Coast lineage, and the Invasive lineage. In Mexico, P. australis is a common species, but nothing is known about the distribution or ecology of these lineages. We examined the phylogeography of P. australis to analyze the current geographic distribution of genetic variation, demographic history, and dispersal patterns to better understand its evolutionary history in Mexico.

METHODS: We sampled 427 individuals from 28 populations. We used two noncoding regions of chloroplast DNA to estimate the levels of genetic variation and identifi ed the genetic groups across the species’ geographical range in Mexico. We compared the genealogical relationships among haplotypes with those previously reported. A hypothesis of demographic expansion was also tested for the Mexican P. australis lineages.

K EY RESULTS: We found 13 new haplotypes native to Mexico that might be undergoing an active process of expansion and diversifi cation. Genealogical analyses provided evidence that two independent lineages of P. australis are present in Mexico. The invasive lineage was not detected with our sampling. Our estimates of population expansions in Mexico ranged from 0.202 to 0.726 mya.

C ONCLUSIONS: P hragmites australis is a native species that has been in Mexico for thousands of years. Genetic data suggest that climatic changes during the Pleistocene played an important role in the demographic expansion of the populations that constitute the diff erent genetic groups of P. australis in Mexico.

PREMISE OF THE STUDY: Is there an association between bioclimatic variables and genetic variation... more PREMISE OF THE STUDY: Is there an association between bioclimatic variables and genetic variation within species? This question can be approached by a
detailed analysis of population genetics parameters along environmental gradients in recently originated species (so genetic drift does not further ob-
scure the patterns). The genus Agave, with more than 200 recent species encompassing a diversity of morphologies and distributional patterns, is an ad-
equate system for such analyses. We studied Agave striata, a widely distributed species from the Chihuahuan Desert, with a distinctive iteroparous
reproductive ecology and two recognized subspecies with clear morphological differences. We used population genetic analyses along with bioclimatic
studies to understand the effect of environment on the genetic variation and differentiation of this species.
METHODS: We analyzed six populations of the subspecies A. striata subsp. striata, with a southern distribution, and six populations of A. striata subsp. fal-
cata, with a northern distribution, using 48 ISSR loci and a total of 541 individuals (averaging 45 individuals per population). We assessed correlations
between population genetics parameters (the levels of genetic variation and diff erentiation) and the bioclimatic variables of each population. We mod-
eled each subspecies distribution and used linear correlations and multifactorial analysis of variance.
KEY RESULTS: Genetic variation (measured as expected heterozygosity) increased at higher latitudes. Higher levels of genetic variation in populations were
associated with a higher variation in environmental temperature and lower precipitation. Stronger population differentiation was associated with wetter
and more variable precipitation in the southern distribution of the species. The two subspecies have genetic differences, which coincide with their climatic
differences and potential distributions.
CONCLUSIONS: Differences in genetic variation among populations and the genetic differentiation between A. striata subsp. striata and A. striata subsp.
falcata is correlated with differences in environmental climatic variables along their distribution. We found two distinct gene pools that suggest active
differentiation and perhaps incipient speciation. The detected association between genetic variation and environment variables indicates that climatic
variables are playing an important role in the differentiation of A. striata.

Aim The history of Agave lechuguilla, a characteristic and dominant plant of the Chihuahuan Deser... more Aim The history of Agave lechuguilla, a characteristic and dominant plant of the Chihuahuan Desert, was reconstructed in order to determine the importance of the Neogene orogenic uplift and the Quaternary glacial–interglacial climatic changes on the genetic patterns of a native Chihuahuan Desert species.

Bulletin of Mathematical Biology, 1998

Ecología Molecular, 2007

... genética es sin lugar a dudas la materia prima para la evolución, ya que de ella dependen tan... more ... genética es sin lugar a dudas la materia prima para la evolución, ya que de ella dependen tanto la adaptación como la especiación. ... La mayoría de especies prioritarias se han propuesto a partir de un concepto tipológico, lo que trae como desventaja el que no se ...

Biological Conservation, 2007

Barrel cacti Conservation Tehuacá n-Cuicatlá n biosphere reserve A B S T R A C T Echinocactus pla... more Barrel cacti Conservation Tehuacá n-Cuicatlá n biosphere reserve A B S T R A C T Echinocactus platyacanthus is a candy barrel cactus endemic to Mexico and an endangered species owing to its exploitation and the destruction of its habitat. The population dynamic of this species is analyzed using matrix models. Three consecutive censuses were carried out (1997, 1998, and 1999) for six populations of this species in the Tehuacá n-Cuicatlá n Biosphere Reserve. Fruit contain many seeds (mean = 171 ± S.E. 11.03 seeds/fruit); seedling establishment and survival are low (2 · 10 À6 ), and fecundity increases as the diameter of the individuals increases (62 seeds in adult 1-4322 in adult 4). The rates of population growth (k) range from 0.9285 to 1.0005. Elasticity values for demographic processes indicate that the stasis of the adults is the greatest contribution (S = 0.982), followed by growth (G = 0.017) and fecundity (F = 0.001) to k. The populations are located in the lower left corner of the demographic triangle; however, there are variations for a given population from one