RESUMO
BACKGROUND AND AIMS: Aridity is increasing in many regions of the world, but microclimatic conditions may buffer plant communities from the direct effects of decreased precipitation, creating habitat islands. However, reduced precipitation can also impact these communities indirectly by decreasing the suitability of the surrounding habitat, thus limiting incoming propagules and increasing the chances of population decline and species loss. We test whether decreased precipitation results in loss of species and functional diversity within habitat islands, evaluating in particular whether declines in species diversity and abundance are less likely to result in loss of functional diversity if species/individual loss is stochastic (i.e. independent of species/individual traits) and communities/populations are functionally redundant. METHODS: Lomas communities are discrete plant communities embedded in the Atacama Desert, maintained by the microclimatic conditions created by fog. We recorded species and functional diversity in six Lomas communities along a 500 km long precipitation gradient in northern Chile. Functional traits were measured in 20 individuals per species, in those species that accounted for approx. 75 % of the abundance at each site. We calculated functional diversity and functional redundancy of the community, and intraspecific functional variation. KEY RESULTS: Decreased precipitation was associated with lower species diversity and lower species abundances. However, no traits or functional strategies increased or decreased consistently with precipitation, suggesting stochastic species/individual loss. Species with stress-tolerant strategies were predominant in all sites. Although species diversity decreased with decreasing precipitation, functional diversity remained unchanged. Lower functional redundancy in the drier sites suggests that mainly functionally redundant species were lost. Likewise, intraspecific functional variation was similar among communities, despite the lower species abundance in drier sites. CONCLUSIONS: Decreased precipitation can impact habitat island communities indirectly by decreasing the suitability of the surrounding habitat. Our results support the idea that a stochastic loss of species/individuals from functionally redundant communities and populations does not result in loss of functional diversity.
Assuntos
Ecossistema , Plantas , Animais , Chile , IlhasRESUMO
Un espécimen de siameses de tiburón azul, Prionace glauca, fue recolectado durante actividades de pesca en el norte de Chile. Según una clasificación basada en el grado de duplicación y el sitio de fusión de los gemelos, el espécimen corresponde a un monstruo del tipo diprósopo tetroftalmo. El individuo tiene una duplicación craneofacial parcial con presencia de cuatro globos oculares e igual número de narinas. Las cavidades orales están interconectadas convergiendo en una única faringe. El tronco es simple; la columna presenta lordosis torácica y una torsión helicoidal en su porción caudal. Este es el primer reporte de siameses en condrictios chilenos y primer registro mundial de diprosopa en tiburones.
A conjoined twins specimen of blue shark Prionace glauca was collected during fishing activities in Northern Chile. According to a classification based on duplication degree and fusion site of the twins, it represents a monster of diprosopus tetrophthalmus type. The specimen has a partial craniofacial duplication with presence of four eyeballs and an equal number of nostrils. Oral cavities are interconnected, converging in a single pharynx. The trunk is simple; the vertebral column presents thoracic lordosis and helical torsion in its caudal portion. This is the first Chilean record of conjoined twins to chondrichthyan and first world record of diprosopia in sharks.