RESUMO
Mexico has one of the highest diversities of barrel cacti species worldwide; however, all are threatened and require conservation policies. Information on their reproductive biology is crucial, but few studies are available. Ferocactus recurvus subsp. recurvus is a barrel cactus endemic to the Tehuacán-Cuicatlán Valley. Our research aimed to characterise its floral and pollination biology. We hypothesised bee pollination, as suggested by its floral morphology and behaviour, and self-incompatibility, like most barrel cacti studied. Three study sites were selected in the semiarid Zapotitlán Valley, Mexico. We examined 190 flowers from 180 plants to determine: morphometry and behaviour of flowers, flower visitors and probable pollinators, and breeding system. Flowers showed diurnal anthesis, lasting 2-5 days, the stigma being receptive on day 2 or 3 after the start of anthesis. Flowers produced scarce/no nectar and main visitors were bees (Apidae), followed by flies (Muscidae), ants (Formicidae), thrips (Thripidae) and hummingbirds (Throchilidae); however, only native bees and occasionally wasps contacted the stigma and anthers. Pollination experiments revealed that this species is self-incompatible and xenogamous. In natural conditions, fruit set was 60% and cross-pollination fruit set was 100%. Percentage seed germination resulting from cross-pollination was higher than in the control treatment. Our results provide ecological information for conservation programmes to ensure a high probability of breeding and seed production in natural populations of F. recurvus.
Assuntos
Cactaceae/fisiologia , Polinização/fisiologia , Reprodução/fisiologia , Animais , Formigas/fisiologia , Abelhas/fisiologia , Aves/fisiologia , Flores/fisiologia , México , Néctar de Plantas/fisiologia , Pólen/fisiologiaRESUMO
Taking the view that morphological characteristics represent behavioral strategies of plants to cope with environmental pressures, we defined 18 life-forms, using multivariate classification techniques in a tropical semiarid ecosystem in Central Mexico. A multiple discriminant analysis confirmed the existence of these groups. A null model of random membership of species to life-forms was significantly different from our classification. Vegetation-environment relationships were examined with Detrended Canonical Correspondence Analysis (DCCA). Ordination axes were interpreted mainly be altitude and soil moisture. Response curves of life-forms along these gradients were explored fitting generalized linear models (GLIM's). We believe that the life-forms approach for the study of vegatation-environment relationships is a valid alternative to the traditional species approach usually used in physiological research because: i) life-forms number was found to be an excellent species diversity predictor, ii) this approach enables considerable reduction in the bulk of data without losing ecological information, and iii) life-forms represent ecological strategies per se and, they constitute an index of the number of different ways the desert's resources are utilized.
Assuntos
Ecossistema , Filogenia , México , Análise MultivariadaRESUMO
Taking the view that morphological characteristics represent behavioral strategies of plants to cope with environmental pressures, we defined 18 life-forms, using multivariate classification techniques in a tropical semiarid ecosystem in Central Mexico. A multiple discriminant analysis confirmed the existence of these groups. A null model of random membership of species to life-forms was significantly different from our classification. Vegetation-environment relationships were examined with Detrended Canonical orrespondence Analysis (DCCA). Ordination axes were interpreted mainly be altitude and soil moisture. Response curves of life-forms along these gradients were explored fitting generalized linear models (GLIM's). We believe that the life-forms approach for the study of vegatation-environment relationships is a valid alternative to the traditional species approach usually used in physiological research because: i) life-forms number was found to be an excellent species diversity predictor, ii) this approach enables considerable reduction in the bulk of data without losing ecological information, and iii) life-forms represent ecological strategies per se and, they constitute an index of the number of different ways the desert's resources are utilized