Bionotícias

Biologia 12 Ficha de Leitura nº6 Data: 07-04-2011 Unidade de Ensino: Engenharia genética Conteúdo/assunto: O número de cromossomas em plantas permite perceber se a planta corre risco de se extinguir ou se de tornar invasiva Título: Ecologistas descobriram que existe uma forte ligação entre o número de pares de cromossomas que compõe o genoma de uma determinada espécie de plantas e o seu risco de se extinguir ou de se tornar invasiva o que permite controlar a conservasão de espécies. Os estudos mostram que as plantas invasivas têm 20% de probabilidades de serem poliploides do que de serem diploides e as plantas em perigo de extinção têm menos 14% de probabilidade de serem poliploides do que diploides. Fonte: Nature Genetics Pesquisador:Ana Abraul Ecologists find genomic clues to invasive and endangered plants Ecologists have discovered strong links between how many sets of chromosomes a plant species has and whether it is in danger of becoming rare, or conversely, becoming invasive. The findings1 could help conservation scientists to predict whether species will need protecting or controlling and how to allocate resources to these efforts. Until now, ecologists have had varied success in finding reliable indicators to help them predict whether species are likely to become endangered or invasive. Most attempts have focused on taxonomic or ecological traits such as the size of the geographical area that the species is found in, while a handful of small-scale studies have looked at genomic traits. But all have proven "equivocal", says Maharaj Pandit, a plant ecologist at the University of Delhi in India, and lead author of the study. "Our findings show clear trends and demonstrate the importance of genomic attributes as risk factors of vulnerability to endangerment or invasiveness in plants," he says. All in the genes The researchers collected chromosome data on 640 endangered species across from the globe and from more than 9,000 related species. They collected the same data for 81 invasive species and around 2,300 of their relatives. In doing so, the researchers have built the biggest data set of its kind. The study was published online last week in the Journal of Ecology. The researchers found that endangered plants, such as Viburnum bracteatum, are "disproportionately" likely to have only two sets of chromosomes (diploid). Invasive plants, however, such as the noxious weed Parthenium hysterophorus generally had multiple sets of chromosomes (polyploid) and higher overall numbers of chromosomes. They found that invasive plants are 20% more likely to be polyploids than diploids, and a species is 12% more likely to become invasive if given the chance as its chromosome number doubles. By contrast, endangered plant species are 14% less likely to be polyploids than diploids, the study finds. The "very strong signals indicating rarity and invasiveness" could be incorporated into existing efforts to assess the risks of invasive and endangered species, adds Michael Pocock, an ecologist at the University of Bristol, UK, and another of the study's authors. Adaptability The researchers say that having multiple sets of chromosomes is often associated with a plant's vigour and the ability to adapt to different environments. This could enable plants to be more competitive and potentially invasive in a new environment. But further research is needed to pin down whether ploidy causes invasiveness or rarity, they say. "There is a need to improve our ability to predict the potential invasiveness of alien species," says Piero Genovesi, a conservation ecologist and chairman of the invasive species unit of the International Union for Nature Conservation. This study "adds an important brick to the construction" of those efforts, he explains. Genovesi says that he does not know of any risk-assessment methods that consider ploidy to help judge whether a plant species could become invasive. But he adds that the findings will not provide an "ultimate tool" to address invasions. "It is very unlikely we will ever be able to predict invasiveness with full certainty," Genovesi says.