Background
The authors write that "gene flow connects populations, maintains genetic diversity, prevents inbreeding and facilitates the spread of adaptive genes across a species range," citing Slatkin (1985, 1987) and Ellstrand and Elam (1993). And, therefore, they state that "understanding how plant populations are connected by gene flow, particularly across altitudinal gradients in mountain regions, will improve our understanding of how they will respond to future environmental change."

What was done
In an attempt to gain some of that important "understanding," the four Swiss scientists studied patterns of historic gene flow, flowering phenology and contemporary pollen flow in two common herbs (Ranunculus bulbosus and Trifolium montanum) along an altitudinal gradient of 1200-1800 meters a.s.l. over a distance of 1 km among five alpine meadows in Switzerland.

What was learned
Matter et al. discovered that "historic gene flow was extensive," with their data suggesting that "contemporary pollen flow is not limited across altitudes in either species."

What it means
Quoting the authors once again, their final conclusion was that "high levels of pollen flow among altitudes in both R. bulbosus and T. montanum should facilitate exchange of genes which may enhance adaptive responses to rapid climate change."

References
Ellstrand, N.C. and Elam, D.R. 1993. Population genetic consequences of small population size: implications for plant conservation. Annual Review of Ecology and Systematics 24: 217-242.

Slatkin, M. 1985. Gene flow in natural populations. Annual Review of Ecology and Systematics 16: 393-430.

Slatkin, M. 1987. Gene flow and the geographic structure of natural populations. Science 236: 787-792.