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Recognizing how populations fluctuate over time is a crucial factor in determining the environmental elements affecting population persistence. However, the limited information on wild bee populations complicates the estimation of the impact of anthropogenic threats leading to changes in population size. To address this, we conducted a study capturing and monitoring nine species of wild bees through monthly samplings over four years. Tray traps were placed in permanent plots, and capture records were used to determine population size (N) and density (D). A generalized linear model (GLM) was employed to determine how the use of traps affected bee species captures. The families Apidae and Halictidae represented the most captures. Apis mellifera, the Lasioglossum (Dialictus spp.) complex, and Macrotera sinaloana exhibited the largest number of captures and highest population density. Most species (77.7%) showed a tendency to remain constant over the years and to have a higher number of captures in the spring months. Moreover, yellow traps were the most effective in capturing bee individuals. We suggest that the availability of essential resources and the reduction in environmental stressors positively affected the capture of wild bee populations.

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Until recently, little research has focused on determination of the population dynamics of invasive species and evaluating their genetic variation. Consequently, not much is known of what drives clonal invasive species and their demography. Here, we describe the population dynamics of Kalanchoe delagoensis (Crassulaceae), considered invasive to several countries. We quantified the demography of a population in central Mexico using integral projection models (IPM) in a population that reproduced asexually exclusively through plantlets. The effect of clonal recruitment on population growth rate (λ) was evaluated by changing plantlet survival and simulating management scenarios that used previous data of watering and seven experimental herbicide treatments. The finite rate of population increase indicated that this Kalanchoe delagoensis population is growing (above one) and with water availability, growth rates will only accelerate. The IPM showed that plantlet survival and recruitment were the most critical steps in the cycle for the population, and simulations of different management scenarios showed that reducing plantlet survival significantly decreased λ only in two out of the seven herbicides used.

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Demographic analyses and ecological niche modeling (ENM) are two popular tools that address species persistence in relation to environmental conditions. Classic demography provides detailed information about the mechanisms that allow a population to grow or remain stable at a local scale, while ENM infers distributions from conditions suitable for species persistence at geographic scales by relating species' occurrences with environmental variables. By integrating these two tools, we may better understand population processes that determine species persistence at a geographic scale. To test this idea, we developed a model that relates climate to demography of the cactus Opuntia rastrera using 15 years of data from one locality. Using this model we determined the geographic area where populations would have positive growth rates given its climatic conditions. The climate-dependent demographic model showed poor performance as a distribution model, but it was helpful in defining some mechanisms that determine species' distributions. For instance, high rainfall had a negative impact on the population growth rate by increasing mortality. Rainy areas to the west of the distribution of O. rastrera were identified as unsuitable both by our climate-dependent demographic model and by a popular ENM algorithm (MaxEnt), suggesting that distribution is constrained by excessive rains due to high mortality. Areas projected to be climatically suitable by MaxEnt were not related with higher population growth rates. Instead, we found a strong correlation between environmental distance to the niche centroid (center of the niche hypervolume, where optimal conditions may occur) and population growth rate, meaning that the niche centroid approach is helpful in finding high-fitness areas.

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Demography of Caulerpa paspaloides var. wudermanni (Bryopsidales: Caulerpaceae) in the coastal zone of Campeche, México. The subaquatic vegetation of Los Petenes, Campeche, Mexico, stands out due to its considerable floristic diversity, composed of a great variety of sea grasses and several species of the genus Caulerpa sp. This is a genus of ecological relevance, with the invasive species in the Mediterranean, with negative impact on several native sub-aquatic plants; nevertheless, little is known about the demography and population dynamics of Caulerpa species and their contribution to food webs. Thus the main objective of this study was to describe the demographics of Caulerpa paspaloides var. wudermanni, using the number of stolons, complete and incomplete fronds, the diameter of the stolons and the biomass. The information was used to determine the growth rate (lambda) of this species. The study was conducted in the Biosphere Reserve of Los Petenes, which is located in the Northwest of the state of Campeche. The submerged aquatic vegetation (SAV) in the Petenes Biosphere consists of monospecific and mixed populations of seagrass species (Thalassia testudinum, Halodule wrightii and Syringodium filiforme). Although chlorophytes, brown algae and red algae, are fundamental elements in the specific composition of the SAV in Petenes, several species of Caulerpa are prominent because of their coverage and abundance. In May and June of 2010, significant differences in the quantity of stolons, their diameter, incomplete and complete fronds, and the size of the stolons and rhizomes, were observed. In 2010, the finite population growth rate (lambda) was 2.38 +/- 0.1571 for individuals and 1.20 +/- 0.1356 for the population, and in 2011 the values of lambda were 1.80 +/- 0.3608 and 1.35 +/- 0.1571, respectively. From these results it can be concluded that the population is growing; however, growth is controlled by biotic and abiotic factors. Despite there was no apparent threat, we suggest continuing the demographic studies of C. paspaloides var. wurdemannii, as well as of other species of the same genus, not only to detect invasion or explosive growth, but also their presence indicated low oxygen levels and high sulphates.

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RESUMO

The subaquatic vegetation of Los Petenes, Campeche, Mexico, stands out due to its considerable floristic diversity, composed of a great variety of sea grasses and several species of the genus Caulerpa sp. This is a genus of ecological relevance, with the invasive species in the Mediterranean, with negative impact on several native sub-aquatic plants; nevertheless, little is known about the demography and population dynamics of Caulerpa species and their contribution to food webs. Thus the main objective of this study was to describe the demographics of Caulerpa paspaloides var. wudermanni, using the number of stolons, complete and incomplete fronds, the diameter of the stolons and the biomass. The information was used to determine the growth rate (λ) of this species. The study was conducted in the Biosphere Reserve of Los Petenes, which is located in the Northwest of the state of Campeche. The submerged aquatic vegetation (SAV) in the Petenes Biosphere consists of monospecific and mixed populations of seagrass species (Thalassia testudinum, Halodule wrightii and Syringodium filiforme). Although chlorophytes, brown algae and red algae, are fundamental elements in the specific composition of the SAV in Petenes, several species of Caulerpa are prominent because of their coverage and abundance. In May and June of 2010, significant differences in the quantity of stolons, their diameter, incomplete and complete fronds, and the size of the stolons and rhizomes, were observed. In 2010, the finite population growth rate (λ) was 2.38±0.1571 for individuals and 1.20±0.1356 for the population, and in 2011 the values of λ were 1.80±0.3608 and 1.35±0.1571, respectively. From these results it can be concluded that the population is growing; however, growth is controlled by biotic and abiotic factors. Despite there was no apparent threat, we suggest continuing the demographic studies of C. paspaloides var. wurdemannii, as well as of other species of the same genus, not only to detect invasion or explosive growth, but also their presence indicated low oxygen levels and high sulphates. Rev. Biol. Trop. 62 (2): 729-741. Epub 2014 June 01.

La vegetación subacuática de Los Petenes, Campeche, México, se destaca por su gran diversidad florística, compuesto por una gran variedad de pastos marinos y varias especies del género Caulerpa sp. Caulerpa es un género de relevancia ecológica, con especies como la Caulerpa taxifolia, que es invasiva en el Mediterráneo, con un impacto negativo en varias plantas sub-acuáticas nativas, pero poco se sabe acerca de la demografía y la dinámica poblacional de las especies de Caulerpa y su contribución a las redes alimenticias. El objetivo general es conocer la demografía de Caulerpa sp., por medio del número de estolones, frondas completas e incompletas, el diámetro de los estolones y la biomasa. El estudio se realizó en la Reserva de la Biosfera de Los Petenes, en Campeche, México. La Vegetación Acuática Sumergida (VAS) en la Biosfera de los Petenes está constituida por poblaciones tanto monoespecíficas como mixtas de las especies de pastos marinos Thalassia testudinum, Halodule wrightii y Syringodium filiforme. Aunque las especies de algas clorófitas, feofitas y rodófitas son elementos fundamentales de la VAS, destacan por su cobertura y abundancia las especies de Caulerpa. En mayo y junio del 2010, hubo diferencias significativas de la cantidad de estolones, su diámetro, frondas completas e incompletas y el tamaño de los estolones como el de los ejes erectos. En el 2010 el valor de la tasa finita de crecimiento poblacional (l) fue de 2.38±0.15 con el método de las marcas y con el de la biomasa 1.20±0.13 y en el 2011 los valores fueron de 1.80±0.36 con las marcas y de 1.35±0.15 con la biomasa. Los resultados indican que la población está creciendo, pero es controlada por factores bióticos y abióticos. A pesar de que no se detecta la especie como una amenaza aparente, sugerimos que se continúen estos estudios demográficos sobre C. paspaloides var. wurdemannii e incluso de otras especies del mismo género. No solo para detectar una invasión o un crecimiento explosivo, sino porque la presencia de estas especies no indican condiciones bajas en oxígeno y altas en sulfatos.

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The response of seed germination towards light and the relationship to seed traits has been studied particularly well in tropical forests. Several authors have shown a clear adaptive response of seed size and photoblastism, however, the evolutionary significance of this relationship for species inhabiting arid environments has not been fully understood and only some studies have considered the response in a phylogenetic context. We collected seeds from 54 cacti species spread throughout the tribe Cacteae to test whether there was correlated evolution of photoblastism, seed traits and germination using a reconstructed phylogeny of the tribe. For each species we determined the photoblastic response under controlled conditions, and seed traits, and analyzed the results using phylogenetically independent contrasts. All studied species were positive photoblastic contrasting with the basal Pereskia suggesting an early evolution of this trait. Seeds from basal species were mostly medium-sized, diverging into two groups. Seeds tend to get smaller and lighter suggesting an evolution to smaller sizes. No evidence exists of a relationship between seed size and photoblastic response suggesting that the photoblastic response within members of this tribe is not adaptive though it is phylogenetically fixed and that is coupled with environmental cues that fine tune the germination response.

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