No abstract

In order to assess the impact of seed removal and seedling establishment for four species of pines, we designed experiments with and without the exclusion of seed removers in three vegetation types (pine forest, oak-alder forest, and subalpine grassland). Seed removal was significantly different between species of pines (P \ 0.01), as was the interaction between the vegetation types and category of exclusion (remover) (P \ 0.0001). The significant difference in terms of seed removal was between P. patula and P. montezumae (33.0 and 17.9%, respectively). Seed removal was significant between pine forest-without exclusion (20.0%) versus oakalder forest-without exclusion (7.0%). There was significant interaction between seedling establishment of the pine species and vegetation type (P \ 0.0001). Highlighting differences between the pine forest-P. teocote (84.1%) versus oak-alder forest-P. patula (19.0%), oak-alder forest-P. pseudostrobus (45.0%), pine forest-P. patula (20.2%), pine forest-P. pseudostrobus (45.6%), subalpine grassland-P. montezumae (24.3%), subalpine grassland-P. patula (27.9%), and subalpine grassland-P. pseudostrobus (17.5%). The impact of the food preferences of rodents and other granivores for P. patula and P. pseudostrobus seeds, as well as the poor survival of seedlings of these species in the pine and oak-alder forest are both factors which may explain the dominance of P. teocote in the study region.

The distribution of the nests of marine turtles on beaches is one of the most important factors for hatchling success. Beaches with fine sands, moderate slopes and good humidity and drainage, are the main environmental variables for ovoposition. The objective of this investigation was to determine the nesting variations of the green turtle during which the nesting frequency per year, beach morphology and distance from the nests to the tidal line were registered. During the nesting seasons, 1 654 nests were registered on 13 beaches, among which significant differences in the number of nests per month were noted (f= 14.07; p< 0.05). Central beaches displayed major nesting probability and included beaches with short distances from the intertidal zone to the supralittoral zone. Dunes were the sites with greater preference for oviposition, being different from the sandy beaches and the intertidal zone (f=54.68; p< 0.05). Significant differences were found in the location of the nests with respect to the tidal line (t=2.33; p< 0.05), and the greatest intervals for nesting were between 10 and 24 m from the tidal line. The area displayed beaches with moderate slopes and dunes with an average distance of 22.6 m from the tidal line. This area is the most important nesting site for green turtle in the American Continent.

No abstract

Survival and mating success are traits of quality in mass-reared sterile males. Thus, studying the trade-offs between these traits may help to improve process in the sterile insect technique (SIT). Here, we tested the hypothesis that modifying individual metabolism, especially of energetic reserves, may reduce the negative impact of an early reproduction on the survival of Anastrepha ludens flies. Appling metformin (a drug used to treat type II diabetes) that improves insects’ survival, through dietary restriction mimicry, and methoprene (a juvenile hormone analogue) that accelerates the age to reproduction in insects, we explore the dynamic of this trade-off. We fed A. ludens flies with metformin, methoprene, or a mixture of metformin–methoprene for five consecutive days. We determined the effect of these treatments on the fecundity and fertility (number of eggs and percentage of hatching) of females, on sexual maturation and mating success of males, and on the survival of both sexes. The results showed that the acceleration in sexual maturation by the action of methoprene significantly reduced survival in both sexes of two different fly strains. However, adding metformin to the diet buffered this negative effect, without reducing the mating propensity compared with the males treated only with methoprene. The response to metformin was sex-specific since females responded to high doses of the substance, whereas males responded better to low doses. These results suggest that trade-offs between survival and reproduction do not necessarily depend on energy reserves but they are intrinsically related to metabolic regulation and hormonal control.

Germination of Ficus insipida (Moraceae) seeds from toucan (Ramphastos sulfuratus) and spider monkey (Ateles geoffroyi) feces. To test the null hypothesis that two vertebrate fructivores, toucans (Ramphastos sulfuratus) and spider monkeys (Ateles geoffroyi), are equally specialized in germinating Ficus insipida seeds after these have passed through their digestive tracts, we fed fruits to captive individuals. We extracted seeds from feces and placed them on filter paper in petri dishes under controled light, temperature and humidity. Control seeds had not passed through a digestive tract. We found that a greater proportion of seeds from A. geofroyi (65%) germinated (R. sulfuratus: 4%). The germinative value was also greater in seeds from monkey feces (rate=13.76; toucan 0.046; control group 0.172). If, despite individual variability of seeds and dispersers, future studies continue to show that A. geoffroyi favors germination more (maybe because of a longer digestion time), this would indicate that diet specialization is not necessarily related to dispersal efficiency. Rev. Biol. Trop. 54(2): 387-394. Epub 2006 Jun 01.

No abstract

Displacements of the green iguana (Iguana iguana) (Squamata: Iguanidae) during the dry season in La Palma, Veracruz, Mexico. The green iguana (Iguana iguana) is said to be primarily sedentary, although the females travel long distances to nest. Displacement patterns must be known to help predict the effects of environmental disturbance on iguanas' survival. We studied nesting season (February-July) movements in La Palma, Los Tuxtlas, Veracruz, Mexico (18°33' N, 95°03' W). Individual movements and activity were monitored by radio tracking. The transmitters were implanted surgically in eight adult iguanas (four males and four females). Snout vent length (SVL) was used to determine the relationship between size of the body and size of home range. To estimate the size of home range, three or more points were used. Minimum convex polygons estimates of home range were calculated with McPAAL. The iguanas were radio-located between 23 and 30 occasions, mainly in trees (56 % between 3-9 m); only 4 % were localized under a height of 3 m (forest floor). The occupation area mean was larger for males (9 158.06±3 025.3m 2 vs. 6 591.24±4 001.1 m 2 ) although the differences were not significant (t= 0.51, p>0.05). SVL was correlated with home range (r= 0.76; gl= 7; p<0.05). Breeding males defended their home range vigorously against other adult males. We observed one separate male home range and large portions of overlap between the sexes. The home range generally formed a conglomerate of polygons and only two had linear shapes along the river: apparently iguanas use the riparian vegetation for foraging. The females display two strategies for nesting: 1) moving to the sandy area near the sea or, 2) laying eggs near the river, in loam. Iguanas responded to habitat fragmentation and reduction by modifying their nesting strategy. Rev. Biol. Trop. 55 (2) Key words: home ranges, green iguana, Los Tuxtlas, nesting, radiotracking.La iguana verde (Iguana iguana) ha sido considerada principalmente sedentaria, aunque se conoce que las hembras realizan largos recorridos para llegar a las playas arenosas para anidar comunalmente (Montgomery et al. 1973. No obstante, existen sitios donde algunas iguanas (Cyclura) llegan a anidar en suelos menos accesibles para la construcción de nidos (Wiewandt 1979). Cuando esto ocurre, las iguanas seguramente se enfrentan a conflictos de supervivencia que pueden estar relacionados con asegurar el éxito en la anidación, incubación y eclosión, viajando a los sitios arenosos; o permanecer en su ámbito hogareño, sin la necesidad de trasladarse grandes distancias por zonas poco conocidas.La extensión y la forma del ámbito hogareño (AH), están relacionadas con los factores ambientales que ejercen presión selectiva sobre las especies, principalmente la disponibilidad de recursos. La estimación del área que cubre el ámbito hogareño, no es un indicador suficiente de lo que se encuentra en su interior (Curtis y Zaramody 1998). Por esto, es necesario incluir