Nutrients affect allocation to male and female function in Abutilon theophrasti (Malvaceae)

In a pair of similar experiments, we examined the effects of varying substrate nutrient levels on several measures of male and female function in Abutilon theophrasti (Malvaceae). In the first trial, plants adjusted allocation to female function at several levels: number of flowers initiated, locule number, percentage of fruits matured, and percentage of ovules matured. In the second trial, plants were much larger, opened more flowers, and matured more fruit (in total but not on a percentage basis). However, in response to nutrient level, plants adjusted maternal investment at fewer levels than in the first trial. Seed mass varied between, but not within, trials. Little to no adjustment was seen in male characters within either trial, although flower number differed within trials and stamen number differed between trials. The lack of adjustment of paternal investment may be due to the fact that A. theophrasti is primarily an autogamous species. Between the two trials, growing conditions, primarily light intensity, varied and plants adjusted their allocation to reproduction differently, indicating plasticity in this trait.     

Old concepts,new challenges: adapting landscape-scale conservation to the twenty-first century

Landscape-scale approaches to conservation stem largely from the classic ideas of reserve design: encouraging bigger and more sites, enhancing connectivity among sites, and improving habitat quality. Trade-offs are imposed between these four strategies by the limited resources and opportunities available for conservation programmes, including the establishment and management of protected areas, and wildlife-friendly farming and forestry. Although debate regarding trade-offs between the size, number, connectivity and quality of protected areas was prevalent in the 1970–1990s, the implications of the same trade-offs for ongoing conservation responses to threats from accelerating environmental change have rarely been addressed. Here, we reassess the implications of reserve design theory for landscape-scale conservation, and present a blueprint to help practitioners to prioritise among the four strategies. We consider the new perspectives placed on landscape-scale conservation programmes by twenty-first century pressures including climate change, invasive species and the need to marry food security with biodiversity conservation. A framework of the situations under which available theory and evidence recommend that each of the four strategies be prioritized is provided, seeking to increase the clarity required for urgent conservation decision-making.     

Plant Production Responses to Precipitation Differ Along an Elevation Gradient and Are Enhanced Under Extremes

Ecosystems - The sensitivity of plant production to precipitation underlies the functioning of ecosystems. Studies that relate long-term mean annual precipitation and production across multiple...     

Retinal ganglion cell death and regeneration of abnormal retinotectal projections after removal of a segment of optic nerve in Xenopus tadpoles

Totally or partially disorganized visuotectal projections have been reported to develop following surgical manipulations in embryonic and larval Anura. Here it is shown that these are associated with a thin optic nerve arising from a retinal ganglion cell layer containing 20–30% of normal cell numbers, and entering the brain by the oculomotor nerve root. Such abnormal patterns of nerve growth have been found to result when a segment of optic nerve is removed. It is suggested that the abnormality represents a process of retinal ganglion cell death rather than a misprogramming of ganglion cell specificities as was previously hypothesized.