Effect of latitude, temperature and nitrogen in traits of native and invasive Impatiens species
Successful invasions depend on a number of abiotic and biotic factors such as resource availability, climate, and community structure of invading habitat. Global change phenomenon such as increase in global average temperature, high nitrogen deposition rates provide an explanation for enhanced dispersal of non-native species. There have been few studies which compared response of invasive with congeneric native species along latitudinal gradients. The overall research questions of this study are: a) Does latitude affect invasive species more than native species? b) Do invasive species show stronger positive response to temperature than native species?, and c) Do invasive species respond stronger to nitrogen availability than native species?
To answer these questions, we measured morpho-physiological traits in 30 native, Impatiens noli-tangere and 21 invasive I. parviflora populations along a latitudinal gradient in Europe. For each population, we measured average temperature and available soil nitrogen during six weeks of the growing season. We used mixed effect model to identify the effect of environmental factors on selected traits.
Plant height, leaf area, seeds per capsule and plant biomass of invasive species show stronger negative responses to soil nitrogen than that of native species. Native species show stronger negative responses to change in the six weeks growing season temperature than that of invasive species. Only leaf area and only in I. noli-tangere was varied consistently with the six weeks growing season temperature, leaves being smaller in warmer environments. Seed mass of both species were significantly affected by latitude. I. noli-tangere growing in northern latitudes produced heavier seeds than plants growing in southern latitudes but the opposite pattern was seen in I. parviflora. I. parviflora from northern latitudes also produced fewer seeds per capsule than plants from southern latitudes.
Our results suggest that I. noli-tangere shows adaptations to surviving in the north by producing bigger seeds, while I. parviflora does the opposite. Our findings further highlighted that with the increase in temperature, the native species will suffer more than that of invasive species and increase in nitrogen in soil might not be favourable for invasion by I. parviflora, although additional studies are required to untangle this phenomenon.