Mecanismos proximos determinantes de la ecologia de culebras simpatricas del valle de toluca

El estudio de la ecología poblacional en las especies silvestres provee explicaciones adaptativas respecto al origen y diversidad de los modos y ciclos de vida y es una herramienta para entender los mecanismos y los efectos de la selección natural sobre la dinámica de las poblaciones. Los organismos están sujetos a las condiciones del medio en que habitan, por lo que se ha propuesto que algunas características de su ciclo de vida deben haber evolucionado como respuestas adaptativas a su hábitat (Stearns 1992). Los organismos administran e invierten sus recursos hacia sus diferentes actividades (por ejemplo el forrajeo, la reproducción, el crecimiento), en base al balance entre los costos y beneficios implicados y que determinan la expresión de su ecología en particular (Caswell 1989)

SEXUAL SIZE DIMORPHISM, DIET, AND REPRODUCTION IN THE MEXICAN GARTER SNAKE, THAMNOPHIS EQUES

Although adult T. eques females had a longer SVL and HL than males, the sexes did not differ in their diet, and we found that larger females had more offspring. These results suggest that sexual size dimorphism in natural populations of T. eques may be determined by fecundity selection rather than by the ecological factors associated with the spectrum of available prey sizes. The lack of intersexual differences in the slope of the regression between HL and SVL, and the upward shift in the intercept of the regression line for females together with the shift along the common slope toward larger females (data for larger females do not overlap with the data for larger males), showed that the larger heads of the females are probably an outcome of their larger bodies (SVL) and not of the allometric relationship between these traits.In this study we examined diet, reproduction, and sexual dimorphism in body size of adult Thamnophis eques. We measured 307 adult snakes within the hydrologic system of High Lerma. Prey was obtained by forced regurgitation when snakes were collected, and gravid females were housed in the laboratory until parturition. Females had a longer snout-vent length and shorter tails than males, but there was no difference in total length between the two sexes. We found no evidence to support the hypothesis that sexual dimorphism is due to differences in prey size for this species because the sexes did not differ in the type and mass of prey they consumed; however, the size of gravid females was positively related to the number, but not size and weight, of their offspring. Our results suggested that sexual size dimorphism in natural populations of T. eques may be determined by fecundity selection rather than the ecological factors associated with the spectrum of available prey sizes. We also discuss possible reasons why the sexes did not differ in total lengthUniversidad Autónoma del Estado de México 2077/2005U, 2365/2006, 2865/2010U Consejo Nacional de Ciencia y Tecnología (33710)

Extrafloral nectaries in Opuntia robusta

Descubrimos la existencia de nectáreos extraflorales en Opuntia robustaTo our knowledge, there are no studies about the structure and ecological function of extra- floral nectaries (EFNs) in Opuntia robusta. This is the first description of EFNs in O. robusta, where young spines have an interesting structure and a secreting function, which are differ- ent from EFNs described in other Cactaceae species. We used light, scanning-electron, and transmission-electron microscopy to examine morphology, anatomy, and ultrastructure of the secretory spines in areoles in female and hermaphrodite individuals of O. robusta. Young cladodes develop areoles with modified and secretory spines as EFNs only active during the early growth phase. EFNs are non-vascularized structures, with no stomata, that consist of a basal meristematic tissue, a middle elongation region, and an apical secretory cone formed by large globular epidermal cells, containing nectar and medullar elongated cells. We observed the presence of Golgi apparatus, vesicles and plastids in the medullar and sup-epidermal cells of the spine. We propose that the nectar is stored in the globular cells at the apex of the spine and secreted by breaking through the globular cells or by pores. We recorded a more frequent presence of ants on younger cladode sprouts producing young secreting spines: this result is parallel with the predictions of Optimal Defense Hypothesis, which states that younger plant organs should be better defended than older ones because their loss produces a higher fitness impairment. Although Diaz-Castelazo’s hypothesis states that a more complex structure of EFNs correlates with their lower among-organs dispersion, comparing to less complex EFNs, non-vascularized structure of EFNs in O. robusta is not associated with their higher among-organs dispersion likened to O. stricta, which produces vascularized EFNs. We provide evidence that this characteristic is not a good taxonomic fea- ture of Opuntia genus. Moreover, the comparison of EFNs of O. robusta and O. stricta sug- gests that the hypothesis of Diaz-Castelazo should be revised: it is rather a rule but not a law.CONACyT 180694/201

Chemical and Physical Defense Traits in Two Sexual Forms of Opuntia robusta in Central Eastern Mexico

In this study, we showed that the seed output is higher in hermaphrodites than in females of O. robusta but also has a higher variance. Furthermore, the hermaphrodite sexual form is on average spinier than the female form, and reproductive cladodes are spinier in hermaphrodites than in females. In addition, we showed that hermaphrodite empty cladodes contain a higher concentration of phenolic compounds than female empty cladodes and found a possible trade-off between the production of phenolic compounds in parental cladodes and their content in daughter cladodes. There also was a possible trade-off between the density of spines on areolae and average number of areolae per cladode, and a positive relationship between physical and chemical defense traits. With the current data, we cannot conclude that sexual polymorphism in the study population is herbivore mediated. In addition, we cannot make inferences about the possible evolution from gynodioecy to dioecy in O. robusta because of the need for accurate information concerning the costs of inbreeding, the entire costs of reproduction, the lifetime reproductive success, the estimation of vegetative growth traits, and possible competition for pollinators with other plant species.Sexually dimorphic plants provide an excellent opportunity for examining the differences in the extent of their defense against herbivores because they exhibit sex-related differences in reproductive investment. Such differences enable comparison of the sex with high reproduction expenses with the sex that expends less. The more costly sex is usually also better defended against herbivores. Generally, females are considered more valuable than hermaphrodites in terms of fitness; however, hermaphrodites are more valuable if they can produce seed by autonomous selfing, provided that the inbreeding depression is low and pollen is limited. We studied a gynodioecious population of Opuntia robusta from Central- Eastern Mexico, which has been reported to be trioecious, dioecious, or hermaphrodite, and addressed the following questions: 1) Is the hermaphrodite’s reproductive output higher than the female’s, and are hermaphrodites thus better defended? 2) Are plant tissues differentially defended? 3) Do trade-offs exist among different physical defense traits? and 4) among physical and chemical defense traits? We found that 1) hermaphrodites had a higher seed output and more spines per areola than females and that their spines contained less moisture. Non-reproductive hermaphrodite cladodes contained more total phenolic compounds (TPCs) than female ones. In addition, 2) hermaphrodite reproductive cladodes bore more spines than female cladodes, and 3) and 4) we found a negative relationship between spine number per areola and areola number per cladode and a positive relationship between spine number per areola per plant and TPC concentration per plant. Non-reproductive hermaphrodite cladodes contained a higher concentration of TPCs than female cladodes, and parental cladodes contained fewer TPCs than both reproductive and empty cladodes.UAEM project 2823/2009U CONACyT project 180694/201

Bulletin of British earthquakes 2015

"To our knowledge, there are no studies about the structure and ecological function of extrafloral nectaries (EFNs) in Opuntia robusta. This is the first description of EFNs in O. robusta, where young spines have an interesting structure and a secreting function, which are different from EFNs described in other Cactaceae species. We used light, scanning-electron, and transmission-electron microscopy to examine morphology, anatomy, and ultrastructure of the secretory spines in areoles in female and hermaphrodite individuals of O. robusta. Young cladodes develop areoles with modified and secretory spines as EFNs only active during the early growth phase. EFNs are non-vascularized structures, with no stomata, that consist of a basal meristematic tissue, a middle elongation region, and an apical secretory cone formed by large globular epidermal cells, containing nectar and medullar elongated cells. We observed the presence of Golgi apparatus, vesicles and plastids in the medullar and sup-epidermal cells of the spine. We propose that the nectar is stored in the globular cells at the apex of the spine and secreted by breaking through the globular cells or by pores. We recorded a more frequent presence of ants on younger cladode sprouts producing young secreting spines: this result is parallel with the predictions of Optimal Defense Hypothesis, which states that younger plant organs should be better defended than older ones because their loss produces a higher fitness impairment. Although Diaz-Castelazo’s hypothesis states that a more complex structure of EFNs correlates with their lower among-organs dispersion, comparing to less complex EFNs, non-vascularized structure of EFNs in O. robusta is not associated with their higher among-organs dispersion likened to O. stricta, which produces vascularized EFNs. We provide evidence that this characteristic is not a good taxonomic feature of Opuntia genus. Moreover, the comparison of EFNs of O. robusta and O. stricta suggests that the hypothesis of Diaz-Castelazo should be revised: it is rather a rule but not a law.

Chemical and physical defense traits in two sexual forms of opuntia robusta in Central Eastern Mexico

Sexually dimorphic plants provide an excellent opportunity for examining the differences in the extent of their defense against herbivores because they exhibit sex-related differences in reproductive investment. Such differences enable comparison of the sex with high reproduction expenses with the sex that expends less. The more costly sex is usually also better defended against herbivores. Generally, females are considered more valuable than hermaphrodites in terms of fitness; however, hermaphrodites are more valuable if they can produce seed by autonomous selfing, provided that the inbreeding depression is low and pollen is limited. We studied a gynodioecious population of Opuntia robusta from Central-Eastern Mexico, which has been reported to be trioecious, dioecious, or hermaphrodite, and addressed the following questions: 1) Is the hermaphrodite's reproductive output higher than the female's, and are hermaphrodites thus better defended? 2) Are plant tissues differentially defended? 3) Do trade-offs exist among different physical defense traits? and 4) among physical and chemical defense traits? We found that 1) hermaphrodites had a higher seed output and more spines per areola than females and that their spines contained less moisture. Non-reproductive hermaphrodite cladodes contained more total phenolic compounds (TPCs) than female ones. In addition, 2) hermaphrodite reproductive cladodes bore more spines than female cladodes, and 3) and 4) we found a negative relationship between spine number per areola and areola number per cladode and a positive relationship between spine number per areola per plant and TPC concentration per plant. Non-reproductive hermaphrodite cladodes contained a higher concentration of TPCs than female cladodes, and parental cladodes contained fewer TPCs than both reproductive and empty cladodes

Replication data for: The effect of reforestation on bird communities in two types of forests in the Nevado de Toluca, Mexico.

Numbers of individuals and volumes of the plant species from the three strata (herbaceous, shrub, trees), for the native forest (natural forest; Amanalco) and reforested forest (Cacalomacan), as well as the corrresponding Importance Value Index (IVI). The vegetation attributes were measured in February and March 2016 within a 20 x 12 m rectangle. Inside each rectangle, a mist net was the symmetry axis (dividing the rectangle in two). We counted all the trees from each species inside the rectangle and measured the diameters of all the trees at breast high (DBH) to the nearest 0.5 cm in small trees, and to the nearest 1.0 cm in large trees. We estimated the volume of each tree at DBH, and both the density of all the tree species. To estimate the attributes of shrub and herbaceous strata, we traced 20-meter-long perpendicular lines at the limits and at the midpoint of the net, being the net the midpoint of these lines. We estimated the volumes of the shrubs crossed by these lines. When it was possible to distinguish an individual shrub, we approximated its volume as the volume of a cylinder. When the shoots of different individuals were indistinguishable (“shrub wall”), we approximated their pooled volume as the volume of a cuboid and counted the number of shoots. The volume of the herbaceous stratus was estimated in a similar manner (Fig. 2). The determination of the volume of the species refers to occupation and was read from the regular cylinder formula (w × l × h), where: w – width, l – length and h – height. The total volume of each species was estimated as follows: 1. When it was possible to distinguish between individuals of the same species, the total volume was obtained by adding the volumes of the stems of each plant. 2. When it was not possible to distinguish between individuals of the same species, the total volume was measured as all the individuals as one. A different group of individuals was considered if there was a distance equal to or greater than 50 cm between two neighboring groups. For each rectangle, dominance was obtained by dividing the total volume of each species by the total volume of all the species. Density was obtained by dividing the number of individuals of each species among the total number of individuals of all the species in the stratum. The importance value index (IVI) was obtained by summing the dominance and the density. The same indices were calculated for shrubs and herbaceous

Replication Data for: Secondary compounds in two sexual form of Opuntia robusta from Central-Eastern México

Dataset contain contains absorbances and concentrations of 4-hydroxybenzoic acid, chlorogenic acid and quercetine in the cladodes of hermaphrodite and female individuals of Opuntia robusta, growing at San Nicolas Tecoaco, Municipality of Singuilucan, Hidalgo State, Central-Eastern Mexico, as well as the results of statistical analysis

The number of herbivores in Opuntia robusta in San Nicolás Tecoaco, Hidalgo, México.

Young cladodes and flower buds developed areoles with modified and secretory spines as EFNs only active during the early growth phase of female and hermaphrodite individuals. In most species, EFNs reward ants in exchange for protection. We analyze this possible effect recording the number of herbivores in Opuntia robusta in San Nicolás Tecoaco, Hidalgo, México