Occurrence, spatio-temporal distribution, and human health risk assessment of pesticides in fish along the Ayuquila-Armería River, Mexico.

Pesticide usage has contributed to increasing food production; it has also caused them to be found in ecosystems inducing adverse effects on biota. Fish are the most abundant and diverse vertebrates in the world and are of great importance both economically and ecologically. Some fishes are indicators of the environmental quality of aquatic ecosystems and provide insight as to how pollutants might influence public health. The tilapias species can be considered biomonitors because they present little displacement representing the contamination level of a site. This study aimed at three goals: (1) to determine the concentration of 20 pesticides in tilapia muscle in the Ayuquila-Armería basin, (2) to describe the spatiotemporal variation of analytes and (3) to evaluate the risk of consuming contaminated fish. The presence of 11 pesticides was determined. Ametrine, glyphosate and malathion concentrations showed significant differences by season. The risk assessment showed that the consumption of tilapia muscle from the Ayuquila-Armería basin does not represent a risk for the population. Diazinon concentrations were relatively low compared to the other pesticides concentrations, but its toxic characteristics were the ones that most negatively influenced the risk assessment. The results obtained are relevant from the social and economic points of view.

Endozoochorous dispersal of forest seeds by carnivorous mammals in Sierra Fría, Aguascalientes, Mexico.

Some carnivorous mammals ingest fruit and disperse seeds of forest plant species capable of colonizing disturbed areas in ecosystems. The objective of the present study was to evaluate the dissemination of Arctostaphylos pungens and Juniperus deppeana seeds by the gray fox (Urocyon cinereoargenteus), coyote (Canis latrans), and other carnivores in the Protected Natural Area Sierra Fría, in Aguascalientes, Mexico. Scat collection was undertaken via transects using the direct search method, while the seasonal phenology of A. pungens and J. deppeana was evaluated by recording flower and fruit abundance on both the plant and the surrounding forest floor ground. Seed viability was assessed by optical densitometry via X-ray and a germination test. It was found that the gray fox, coyote, ringtail (Bassariscus astutus), and bobcat (Lynx rufus) disseminated seeds of A. pungens (212 ± 48.9 seeds/scat) and J. deppeana (23.6 ± 4.9 seeds/scat), since a large proportion of the collected scat of these species contained seeds (28/30 = 93.33%, 12/43 = 27.9%, 6/12 = 50% and 7/25 = 28% respectively). The gray fox, coyote, ringtail, and bobcat presented an average of seed dispersion of both plant species of 185.4 ± 228.7, 4.0 ± 20.0, 12.1 ± 30.4, and 0.8 ± 1.5 per scat; the seed proportions in the gray fox, coyote, ringtail, and bobcat were 89.6/10.4%, 82.3/17.7%, 90.4/9.6%, and 38.1/61.9% for A. pungens and J. deppeana, respectively. The phenology indicated a finding related to the greater abundance of ripe fruit in autumn and winter (p < .01). This coincided with the greater abundance of seeds found in scats during these seasons. Endozoochory and diploendozoochory enhanced the viability and germination of the seeds (p > .05), except in those of A. pungens dispersed by coyote. These results suggest that carnivores, particularly the gray fox, the coyote, and the bobcat, play an important role in forest seed dissemination, and thus forest regeneration, by making both a quantitative and qualitative contribution to the dispersal of the two pioneer species under study.

Pollination ecology of Stenocereus queretaroensis (Cactaceae), a chiropterophilous columnar cactus, in a tropical dry forest of Mexico.

Flowers of columnar cacti are animal-pollinated, often displaying a chiropterophylic syndrome. This study examined if the columnar cactus Stenocereus queretaroensis, a tropical species endemic to western Mexico, is bat-pollinated, by studying its pollination biology and the foraging behavior of potential pollinators. Flowers were produced in winter through spring, peaking in April. Anthesis was nocturnal, and stigma and anther turgidity began around 2200 hours. Production of nectar secretion and highest sugar concentration and energy supply were nocturnal, peaking between 2200 and 2400 hours. Manual auto-pollination and exclusion experiments showed that self-pollination yielded no fruits, while nocturnal pollinators resulted in high fruit set and seed set compared to diurnal pollination treatments. The nectar-feeding bat Leptonycteris curasoae (Phyllostomidae) was the main nocturnal pollinator with the highest effective pollination. Peak bat visitation coincided with peaks in nectar production. The high abundance of L. curasoae throughout the 4-yr study, suggests that it is a seasonally reliable pollinator for this columnar cactus. While pollination syndromes have been increasingly called into question in recent years, this study suggests that at least for this system, there is a fairly close fit between pollinator and pollination syndrome.