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Functional diversity is related to the maintenance of processes and functions in ecosystems. However, there is a lack of a conceptual framework that highlights the application of functional diversity as an ecological indicator. Therefore, we present a new initiative for motivating the development of ecological indicators based on functional diversity. We are interested in showing the challenges and solutions associated with these indicators. We integrated species assemblage theories and literature reviews. We considered plant traits related to ecosystem processes and functions (specific leaf area, leaf dry matter content, wood density, phenology, and seed mass) to show the application of a selection of functional diversity metrics that can be used as ecological indicators (i.e., community weighted-mean, functional divergence, functional richness and functional evenness). We caution that functional diversity as an ecological indicator can be misinterpreted if species composition is unknown. Functional diversity values can be over-represented by weed species (species established in disturbed sites) and do not maintain original processes and functions in ecosystems. Therefore, we searched for evidence to demonstrate that weed species are ecological indicators of functional diversity changes. We found support for two hypotheses that explain the effect of weed species on ecosystem function: functional homogenization, and functional transformation. Likewise, we showed the application of some tools that can help study anthropogenic effects on functional indicators. This perspective shows that the paradigm of addressing the effects of disturbances on ecosystem processes by using functional diversity as an ecological indicator can improve environmental evaluation, particularly in areas affected by human activities. Key words: weed species, leaf traits, seed mass, wood density, fruit and flower traits. La diversite fonctionnelle est liee au maintien des processus et des fonctions dans les ecosystemes. Cependant, il manque un cadre conceptuel qui mette en evidence l'application de la diversite fonctionnelle comme indicateur ecologi-que. Par consequent, les auteurs presentent une nouvelle initiative pour motiver le developpement d'indicateurs ecologi-ques bases sur la diversite fonctionnelle. Ils souhaitent montrer les defis et les solutions associes a ces indicateurs. Ils ont integre des theories sur les assemblages d'especes et des analyses documentaires. Ils ont pris en compte les traits des plantesliesaux processus et aux fonctionsdes ecosystemes(surface foliaire specifique, teneur en matiere seche des feuilles, densite du bois, phenologie et masse des graines) pour montrer l'application d'une selection de mesures de la diversite fonctionnelle qui peuvent etre utilisees comme indicateurs ecologiques (c'est-a-dire la moyenne ponderee de la commu-naute, la divergence fonctionnelle, la richesse fonctionnelle et la regularite fonctionnelle). Ils mettent en garde contre le fait que la diversite fonctionnelle en tant qu'indicateur ecologique peut etre mal interpretee si la composition en especes est inconnue. Les valeurs de diversite fonctionnelle peuvent etre surrepresentees par les especes adventices (especes eta-blies dans des sites perturbes) et ne permettent pas de maintenir les processus et les fonctions d'origine des ecosystemes. Ainsi, ils ont cherche des preuves demontrant que les especes adventices sont des indicateurs ecologiques des changements de la diversite fonctionnelle. Ils ont trouve un appui pour deux hypotheses qui expliquent l'effet des especes adventices sur la fonction de l'ecosysteme : l'homogeneisation fonctionnelle et la transformation fonctionnelle. De meme, ils ont montre l'application de certains outils qui peuvent aider a etudier l'effet anthropique sur les indicateurs fonctionnels. Cette syn-these montre que le paradigme consistant a etudier les effets des perturbations sur les processus ecosystemiques en uti-lisant la diversite fonctionnelle comme indicateur ecologique peut ameliorer l'evaluation environnementale, en particulier dans les zones affectees par les activites humaines. [Traduit par la Redaction] Mots-cles: especes adventices, traits foliaires, masse des graines, densite du bois, traits des fruits et des fleurs., Introduction At the global level, the implementation of ecological indicators for environmental evaluation and ecosystem conservation has expanded (LaPaix et al. 2009; Tyler et al. 2021). Ecological indicators are quantitative [...]

Populations of the same species that inhabit contrasting environments may be subject to different selection pressures, promoted by the local environment. Therefore, the individuals of the different populations respond to these pressures with adaptations to local environments; however, not all species or populations respond in the same way. We compared some morphological and ecological traits of the lizard Sceloporus mucronatus that inhabits contrasting environments in central Mexico. The results show male-biased sexual size dimorphism in Tecocomulco, but no differences in size between sexes in Parque Nacional El Chico (PNCH). Significant differences were observed in morphometric traits and in body mass between sexes and populations, but not in the interaction between these two factors. In general, females were heavier than males, while males had larger head structures, jaws, and hind limbs than females. In addition, differences were recorded in the volume of the abdomen, which was female-biased in the PNCH, and male-biased in Tecocomulco. Between populations, it was recorded that the organisms from the PNCH were heavier and had larger heads than those from Tecocomulco. Thermal traits showed differences among populations, but not between sexes nor in the interaction among these factors. Individuals from the locality with lower temperature and higher precipitation (PNCH) reached higher body temperatures and used warmer microhabitats than those individuals from the locality with higher temperature and lower precipitation (Tecocomulco). Females from both populations showed a greater degree of active thermoregulation compared to males. In addition, in both sexes and populations, average values of behavioral thermoregulation were different from zero. Significant differences were recorded in microhabitat use between populations. In agreement with previous studies of morphology and thermal ecology carried out in this species from this and other localities, and in different years, we suggest that its populations present a wide phenotypic plasticity. Highlights: Sceloporus mucronatusis an active thermoregulator. Females from both populations showed higher percentages of negative values of behavioral thermoregulation compared to males. Males have larger head structures, jaws, and hind limbs than females. Between populations, differences were recorded in some morphometric and thermal traits, and use of microhabitat. [ABSTRACT FROM AUTHOR]

Background and aims – The reproductive characteristics of sympatric Cactaceae are important because they help to understand interfering or facilitating mechanisms that allow their coexistence. Globose Cactaceae show melittophily flowers that may be attractive to a shared set of pollinators, and if the flowering events are not overlapping, flower resources could be present for the pollinators through time. Ariocarpus kotschoubeyanus and Neolloydia conoidea are two sympatric cactus species in the southern Chihuahuan Desert. The objective of this study is to describe and compare some reproductive characteristics of these species.Material and methods – Individuals of Ariocarpus kotschoubeyanus and Neolloydia conoidea (n = 231 and 212, respectively) were marked and monitored during one year, recording for each species, the floral phenology, behaviour and morphology, flower visitors, breeding and mating systems (through pollination experiments).Key results – The flowering periods of these species do not overlap. The flowers of both species are melittophily, with the same shape, colour, and similar behaviour; both are obligate xenogamous plants. The mating system of Neolloydia conoidea is outcrossing but mixed in Ariocarpus kotschoubeyanus. They share 75% of pollinators (solitary and social bees).Conclusions – The temporal blooming separation of these species could be an important factor to facilitate coexistence within the xerophyte community since they share the same set of pollinators to achieve their reproductive success.

Question: Granivorous ants may affect plants negatively by diminishing their numbers, or positively by dispersing seeds, reducing aggregation and thus competition. We assessed whether, and how, ants affect plant populations and community diversity. Location: Semi‐arid grassland in southern Mexico. Methods: Over 5 years, using ant exclosures, we compared plant diversity in plots where ants were present or not using Hill numbers. Furthermore, we determined whether the effects of ants on plant species depend on the relative dominance or rarity of plants. We tested whether ants cause greater reductions in the abundance of the plant species they prefer most. We also determined whether plant species whose aggregation was reduced by ants increased in numbers. Results: Six plant species increased their numbers when ants were present, and four experienced reductions. Ants reduced richness, although evidence was inconclusive; however, they clearly increased dominant species diversity (2D). Although the overall effect that ants exerted on plant species did not depend on their dominance or rarity, four of the five most abundant species were favored by ants. Ants' preferences did not determine their effect on species' abundance. The species that benefited from ants were those whose spatial aggregation increased when exposed to ants. Conclusions: Ants do not maintain richness, but instead may reduce it by favoring a few dominant species. The lack of a relationship between ants' preferences and their effect on plant populations may arise from a mixture of positive and negative effects on the preferred seeds. Ants may increase aggregation by enhancing seedling performance near their nests, where conditions may be improved, and by dispersing seeds into these areas. This is in line with our finding that common species are favored by ants, because, at our study site, they are more likely to be dispersed. [ABSTRACT FROM AUTHOR]

Antecedentes: Las flores son elementos reproductivos costosos que presentan balances costo/beneficio en sus estructuras. La diversidad de éstas se ha atribuido a factores bióticos como las interacciones con sus visitadores florales y abióticos como las características del ambiente. Preguntas: ¿La morfología floral de M. geometrizans está relacionada con los tipos de vegetación? ¿La comunidad de artrópodos visitadores florales se relaciona con la morfología floral y/o el tipo de vegetación? ¿La morfología floral y la comunidad de artrópodos tendrán relación con la perturbación del ambiente? Especie de estudio: Myrtillocactus geometrizans (Mart. ex Pfeiff.) Console Sitio de estudio y fecha: Selva Baja Caducifolia y Matorral Xerófilo en las Reservas de la Biosfera Tehuacán-Cuicatlán, Puebla Barranca de Metztitlán, Hidalgo. México. Marzo 2017. Métodos: En los cuatro sitios (dos días por sitio), durante el pico de floración de M. geometrizans, se calculó el índice de disturbio, se recolectaron 30 flores (N = 120) y los artrópodos visitadores florales. Se determinaron la morfología floral y los artrópodos. Resultados: Los sitios de la Barranca de Metztitlán presentaron el mayor índice de disturbio, las flores más chicas y mayor número de estructuras florales. Los visitadores florales fueron más abundantes en los matorrales xerófilos, particularmente en el sitio más perturbado donde el grupo funcional más relevante fue el de los polinizadores. Conclusiones: Se encontraron diferencias significativas en la morfología floral de M. geometrizans relacionadas a los tipos de vegetación y ubicación geográfica. Se reportó una compensación entre tamaño y producción de estructuras florales.

Background: Understanding changes in local community composition along environmental gradients is essential for studying the long-term metacommunity dynamics. The metacommunity structure depends on the distribution of species along environmental gradients in terms of their coherence (continuity in their distribution range), species turnover and grouping of their range limits. A Clementsian structure would be defined by coherent ranges, significant turnover and sharp limits between local communities. All other things equal, a Gleasonian structure is distinguished by the absence of clear boundaries between local communities. Questions: The structure of a scrubland/semiarid/xeric metacommunity changes 23 years after its first characterization? Do environment and spatial variables determine the metacommunity structure? Species studied: 104 perennial-plant species. Study site and dates: Zapotitlán semi-arid valley, Puebla, in 1980 and 2003. Methods: Metacommunity structure and its relationship to environmental (edaphic) and spatial (altitude, slope and geographical location) variables were analyzed using data from the two historic surveys. Results: In 1980 a Clementsian structure was determined, which remained unchanged after 23 years. The importance of environmental filters decreased from 1980 to 2003. Conclusions: The prediction that, due to stochastic dispersion of propagules, the metacommunity would tend toward a Gleasonian structure was not fulfilled. There was no evidence for homogenization, although local tetechera communities (with dominance of the giant columnar cactus Cephalocereus tetetzo) had been invaded and transformed into shrubland communities. Local communities and the metacommunity should be monitored continuously to understand of the long-term structuration of these systems.

Antecedentes: Los estudios sobre los patrones de floración, sincronía floral y éxito reproductivo en cactáceas son incipientes y de muchas especies se desconoce prácticamente su biología reproductiva como ocurre con la cactácea globosa Neolloydia conoidea. Preguntas: ¿Cómo es el patrón de floración a nivel poblacional? ¿Cómo es la sincronía floral? y ¿Existe relación entre la sincronía floral y el éxito reproductivo? Especie: Neolloydia conoidea Britton & Rose (Cactaceae) Sitio de estudio y fechas: Municipio de Tolimán en Querétaro, México. Dos años de observaciones (N = 146 individuos en 2015; 142 en 2016) en una población de Neolloydia conoidea. Métodos: Censo de las flores en antesis y análisis de la fenología de floración a través de Estimadores de Densidad por Kernel (EDK) y componentes gaussianos. Determinación de la sincronía floral a través de los índices de Augspurger (SA) y de Marquis (SM) y comparación del éxito reproductivo (fruit set y seed set) por año y por pulsos. Resultados: Neolloydia conoidea presentó un patrón de floración con 5 a 6 pulsos discretos al año. La sincronía por año y por pulsos fue baja y no se correlacionó con el éxito reproductivo. Conclusiones: Neolloydia conoidea presenta un patrón de floración en pulsos con bajos niveles de sincronía. Este es el primer registro de dicha estrategia para una cactácea globosa, aunque un patrón similar ya ha sido reportado para una cactácea columnar. Sugerimos que esto podría representar una estrategia de “bet hedging” en el sitio de estudio.

Background: Field observations of damage in columnar cacti of central Mexico, and previous evidence in scientific literature, indicated the absence of systematic information about kinds of damage, vectors, and pathogens, in this botanical family. Questions: How is the knowledge of damage and defense mechanisms in cacti? Is there a pattern in causal agents and their geographical distribution in the Americas? Methods: A database of 58 taxa by 51 types of damage was developed from literature recorded in ISI Web of Knowledge, Cabdirect, and Google Scholar, and it was analyzed by multivariate methods. Results: From 1,500 species of Cactaceae, only 58 have been studied through this scope. Subfamily Cactoideae has been the most studied, in particular tribe Echinocereeae (= Pachycereeae columnar cacti). Multivariate analysis grouped cacti according to the kind of damage: biotic, or abiotic. Damage due to biotic factors was sub-grouped depending on the herbivores. Damage by abiotic factors is more frequent in extreme latitudes. Fourteen species of columnar cacti were reported with herbivory and rot damage in Central Mexico, of which eight represent new records of damaged cacti. Conclusions: The evidence from field observations, and few recent publications suggest that some generalist herbivores are becoming dangerous in this region, Future research is necessary in order to understand the dynamics of the dispersion of some kinds of damage, the role of human disturbance, and the role and changes in defense mechanisms in wild and domesticated cacti.

Historic demography changes of plant species adapted to New World arid environments could be consistent with either the Glacial Refugium Hypothesis (GRH), which posits that populations contracted to refuges during the cold-dry glacial and expanded in warm-humid interglacial periods, or with the Interglacial Refugium Hypothesis (IRH), which suggests that populations contracted during interglacials and expanded in glacial times. These contrasting hypotheses are developed in the present study for the giant columnar cactus Cephalocereus columna-trajani in the intertropical Mexican drylands where the effects of Late Quaternary climatic changes on phylogeography of cacti remain largely unknown. In order to determine if the historic demography and phylogeographic structure of the species are consistent with either hypothesis, sequences of the chloroplast regions psbA-trnH and trnT-trnL from 110 individuals from 10 populations comprising the full distribution range of this species were analysed. Standard estimators of genetic diversity and structure were calculated. The historic demography was analysed using a Bayesian approach and the palaeodistribution was derived from ecological niche modelling to determine if, in the arid environments of south-central Mexico, glacial-interglacial cycles drove the genetic divergence and diversification of this species. Results reveal low but statistically significant population differentiation (FST = 0.124, P < 0.001), although very clear geographic clusters are not formed. Genetic diversity, haplotype network and Approximate Bayesian Computation (ABC) demographic analyses suggest a population expansion estimated to have taken place in the Last Interglacial (123.04 kya, 95% CI 115.3-130.03). The species palaeodistribution is consistent with the ABC analyses and indicates that the potential area of palaedistribution and climatic suitability were larger during the Last Interglacial and Holocene than in the Last Glacial Maximum. Overall, these results suggest that C. columna-trajani experienced an expansion following the warm conditions of interglacials, in accordance with the GRH.

Se estudió la estructura del banco de semillas en el valle semiárido de Zapotitlán, Puebla. El registro de la composición y abundancia del banco de semillas se realizó en 2 tipos de vegetación (tetechera y matorral espinoso) en los microhábitats (bajo arbustos, espacio abierto y basureros de la hormiga granívora Pogonomyrmex barbatus). Las semillas se recolectaron en las épocas de secas, lluvias y finales de lluvias durante 2 años. No se encontraron diferencias en la densidad de semillas entre las épocas y años, pero sí hubo diferencias entre los microhábitats evaluados. El microhábitat del hormiguero presentó la mayor abundancia de semillas, lo que resalta la importancia de las hormigas en la conformación espacial de la estructura de las comunidades en estos ecosistemas. Se registraron semillas de 38 especies de plantas. La densidad promedio varió de 23 800 a 28 000 semillas m-2, concordando con otros registros de regiones semiáridas y áridas. Las especies más frecuentes fueron las anuales Eragrostis mexicana, Bouteloua barbata, Kallstroemia rosei y Portulaca pilosa. Los resultados muestran que la heterogeneidad de sitios y de microhábitats en esta zona es alta. Es necesaria la realización de más estudios sobre patrones espacio-temporales en los bancos de semillas y su relación con la vegetación en pie en zonas áridas y semiáridas en México.The seed bank structure in the semiarid valley of Zapotitlán, Puebla was studied. The record of the composition and abundance of the seed bank was conducted in 2 types of vegetation (tetechera and thorny scrub) in the microhabitats (under shrubs, open space and refuse- dumps of granivorous ants Pogonomyrmex barbatus). Seed collection was carried out in dry, rainy and late rainy seasons for 2 years. There were no differences in seed density between seasons and years, but there were differences between microhabitats evaluated. The microhabitat of the ant refuse-dumps had the highest abundance of seeds, which highlights the importance of ants in the spatial conformation of the structure of communities in these ecosystems. Seeds of 38 species of plants were recorded. The average density ranged from 23 800 to 28 000 seeds m-2, consistent with other reports for arid and semiarid regions. The most frequent species were the annual Eragrostis mexicana, Bouteloua barbata, Kallstroemia rosei and Portulaca pilosa. Results show that this area had a high heterogeneity at site and microhabitat level. It is necessary to conduct more studies on spatio-temporal patterns in seed banks and their relationship with the standing vegetation in arid and semiarid areas in Mexico.

Los helechos y licófitas tienen diversas estrategias reproductivas que las habilitan para invadir ambientes perturbados y áreas sin vegetación. En este trabajo se estudió la presencia, abundancia y estrategias reproductivas de individuos que crecen en suelos de bosques templados, en la Sierra Nevada, Estado de México. Se eligieron cuatro zonas en las que se instaló un cuadrante permanente de 200m² para cada una, con el fin de registrar variables edáficas, ambientales y de vegetación. La relación entre variables se pudo explorar con análisis de varianza y Análisis Canónico de Correspondencia dando como resultado tres paisajes con base en el grado de alteración ambiental: baja, moderada y severa. Fueron recolectadas cinco muestras de suelo en cada zona para inducir la germinación de helechos y licofitas, obteniendo resultados que revelan una relación positiva entre el grado de alteración y la abundancia de Cheilanthes. En paisajes con baja alteración, la riqueza de especies fue mayor comparada con paisajes de alteración severa, en la que la presencia de especies se redujo a Cheilanthes bonariensis, C. marginata y Pellaea ternifolia subsp. ternifolia. El suelo fue un banco de esporas de Cheilanthes y Pellaea ternifolia subsp. ternifolia ya que las esporas permanecieron viables por diferentes intervalos de tiempo. La apogamia fue la estrategia reproductiva común para especies de Cheilanthes en ecosistemas alterados, aunque estas especies tienen reproducción sexual en ecosistemas naturales con suficiente agua. Por otro lado, Pellaea ternifolia subsp. ternifolia solo presentó reproducción sexual. La apogamia puede estar relacionada con que la alternancia de generaciones se realice en menos tiempo, comparado con un ecosistema de baja alteración.

Mammillaria pectinifera (Cactaceae) es una especie endémica de la Región de Tehuacán-Cuicatlán en los estados de Puebla y Oaxaca. Aunque en la Norma Oficial Mexicana NOM-059-ECOL-2001 está considerada como amenazada y está incluida en el Apéndice I de la CITES, la información derivada de los escasos estudios ecológicos sobre esta especie revela serios riesgos de extinción de sus poblaciones. En el presente estudio se registra una evaluación del riesgo de extinción de M. pectinifera, para la que se empleó el protocolo del Método de Evaluación del Riesgo de Extinción de las Especies Silvestres en México (MER) del Anexo I de la NOM-059-ECOL-2001, el cual se basa en 4 criterios para evaluar cualitativamente el riesgo de extinción de cualquier especie silvestre en el territorio nacional. Dicha evaluación se apoya en datos de campo de 7 poblaciones e información procedente de diversas fuentes. De acuerdo con los 12 puntos obtenidos del MER, se propone que M. pectinifera se considere en la categoría de especie en peligro de extinción (P) en la NOM-059-ECOL-2001 y sea incluida de nuevo en la Lista Roja de la UICN. Finalmente se plantea una propuesta para mejorar la valoración del Criterio D del MER.Mammillaria pectinifera (Cactaceae) is an endemic species from the Tehuacán-Cuicatlán region at the Mexican States of Puebla and Oaxaca. Although it is considered as a threatened species under Mexican law NOM-059-ECOL-2001, and it is already included in the CITES Appendix I, ecological studies reveal serious vulnerability to extinction of its populations. In this study, we conducted an extinction risk assessment for M. pectinifera based on the protocol of the Method for Evaluation of Risk of Extinction for Mexican Wild Species (MER) from Appendix I of NOM-059-ECOL-2001, which is based on a qualitative assessment of 4 criteria for evaluating extinction risk of any wild species in the Mexican territory. The present assessment relies on data from field studies on 7 populations as well as information from several sources. The MER assessment resulted in a risk score of 12 points and, accordingly, we propose to consider M. pectinifera as a species under extinction risk (P) in NOM-059-ECOL-2001. Also, it should be included again in the Red List of IUCN. Finally, we suggest ways for improving the assessment of Criterion D of the MER.

Pteridophytes that indicate environmental alteration in the temperate forest of San Jerónimo Amanalco, Texcoco, México. Pteridophytes that indicate environmental alteration in the San Jerónimo Amanalco temperate forest, Texcoco, Mexico. The patterns of distribution of 26 pteridophyte species were studied as possible indicators of environmental alteration in the temperate forest of San Jerónimo Amanalco, Texcoco, State of Mexico. The presence and abundance of the pteridoflora was studied in relation to edaphic, topographic and vegetation variables in 100 sampling locations within an area of 494 hectares. The relationship between these variables was studied using Canonical Correspondence Analysis. Five landscapes were recognized in the study zone according to the degree of deterioration: severe erosion, erosion, mountain with moderate reversible deterioration, mountain with no evident deterioration, and canyon with no evident deterioration. Cheilanthes bonariensis and Pellaea ternifolia are indicators of environmental degradation. The taxa that only grow in landscapes without apparent alteration are Adiantum andicola, Adiantum poiretii, Argyrochosma incana, Asplenium blepharophorum, Dryopteris pseudo filix-mas, Equisetum hyemale and Pteris cretica. Rev. Biol. Trop. 56 (2): 641-656. Epub 2008 June 30.

The bird species distribution along a dry forest-oak woodland vegetation gradient was studied in autumn and spring in two consecutive years. Intra-seasonal comparisons showed that bird species had similar distributions in each of the two years. Inter-seasonal changes were mainly due to compositional differences even though resident species generally used similar habitats in both seasons. Ordination analyses, based on the first year bird species abundances, showed a clearly segregated distribution between forest and woodland birds. Within these two vegetation types, the distribution tended to be more individualistic. Nevertheless further habitats could be identified according to groups of birds having similar distributions. These habitats did not correspond to the plant associations which resulted from a previous classification of the vegetation. Observations of the plant use by the birds during the study period showed that, in most cases, the plant variables associated with ordination analyses are unlikely to be very important for the bird species life cycles. Rev. Biol. Trop. 54(2): 657-672. Epub 2005 Jun 01.Se estudió la distribución de especies de aves a lo largo de un gradiente de vegetación bosque seco - bosque de encino en el otoño y primavera de dos años consecutivos. Las comparaciones intra-estacionales mostraron distribuciones similares de las especies de aves en ambos años. Los cambios inter-estacionales se debieron principalmente a diferencias en la composición, aunque las especies residentes normalmente usan hábitats similares en ambas estaciones. Los análisis de ordenación, basados en las abundancias de las aves en el primer año de muestreo, mostraron una distribución claramente segregada entre aves del bosque seco y del bosque de encino. Aunque la distribución de las especies fue más azarosa dentro de cada tipo de vegetación, se pudieron identificar ciertos hábitats en base a grupos de aves con distribuciones similares. Estos hábitats no correspondieron con las asociaciones vegetales identificadas. Las observaciones del uso de las plantas durante el período de estudio sugieren, en la mayoría de los casos, que las variables vegetales asociadas con los ejes de ordenación no serían muy importantes para el ciclo de vida de las especies de aves. Sin embargo, se requiere investigación adicional para comprender su verdadera función.

Se elaboró una lista de taxa endémicos de la flora vascular de Veracruz. Se registraron 94 géneros de 56 familias que contienen 131 especies y 10 taxa subespecíficos con distribución restringida a los límites del estado. Las familias con el mayor número de unidades endémicas fueron Orchidaceae (11), Myrtaceae (10), Bromeliaceae (9), Poaceae (8), Begoniaceae (7), Zamiaceae (5) y Polypodiaceae (5). Los tipos de vegetación que presentaron la mayor diversidad de endemismo, son el bosque tropical perennifolio (52), el bosque mesófilo de montaña (43), el bosque tropical caducifolio (23), el bosque de Quercus (20), el bosque de coníferas (16), el bosque de galería (15) y el bosque tropical subcaducifolio (11).

Plant species with aerial seed banks are commonly referred to as "serotinous," an adaptation in which seed release happens in response to an environmental trigger. Individuals of Ariocarpus kotschoubeyanus (Cactaceae), a specially protected species, store some seeds on the plant over 1 year. We examined the seed retention time, the release mechanism, and the germination behavior of this species in Central Mexico. Flowers produced in a population of A. kotschoubeyanus were monitored, and the number of fruits retained or expelled was determined to calculate the serotiny degree (the number of seeds retained in the tubercules of the plant divided by the total number of seeds produced per plant). The seed retention in previous years was estimated for 30 individuals. The dynamics of retained seeds in the mother plant (seed age in "rings") were determined from the annual average production of tubercules per individual, using observations for 5 years. A germination test employing the seeds collected from recently formed fruits and those obtained from different rings was conducted. We observed that 86.6% of the plants showed seed retention (aerial seed bank) in some ring of the aerial stems. The serotiny degree was 37.3, having 32.68 seeds per plant. Seeds retained in the "rings" from 1‐ to 24‐year‐old plants had a higher germination proportion (between 0.40 and 0.73) than fresh seeds (0.13). Seeds increase their germination proportion with age; thus, seed retention by tubercules (serotiny) represents a reproductive strategy to conserve germplasm until favorable conditions to germinate are present. [ABSTRACT FROM AUTHOR]

Foraging strategies can be influenced by many factors such as abundance, availability, and toxicity of the resources. In arid zones, the distribution and productivity of plants also act as additional factors that affect foraging strategies. Twenty colonies of Pogonomyrmex barbatus ants were studied in an arid zone of central Mexico to evaluate the trophic niche breadth in two sites with contrasting productivities in terms of their diversity and amount of resources during two seasons. The results suggest that when the resources are abundant as in the rainy season, the trophic niche breadth is reduced in sites with high productivity and, in the same sites, the trophic niche breadth increases when the resources are limited as in the dry season. In contrast, the trophic niche breadth is similar in both conditions of resource availability (i.e., rainy and dry seasons) at sites with low productivity. During the dry season, populations of P. barbatus showed a similar foraging behavior in sites with high and low productivity. Thus, the particular characteristics of a site can significantly affect the foraging strategies of the ants in those environments.