Draining the Swamping Hypothesis: Little Evidence that Gene Flow Reduces Fitness at Range Edges.

The genetic swamping hypothesis proposes that gene flow from central to peripheral populations inhibits local adaptation and is one of the most widely recognized explanations for range limitation. We evaluated empirical support for this hypothesis in studies quantifying patterns of gene flow to peripheral populations and their resulting fitness outcomes. We found little evidence that gene flow is generally asymmetric from central to peripheral populations and also that gene flow tends to have positive effects on edge population fitness.

Evidence for adaptive responses to historic drought across a native plant species range.

As climatic conditions change, species will be forced to move or adapt to avoid extinction. Exacerbated by ongoing climate change, California recently experienced a severe and exceptional drought from 2011 to 2017. To investigate whether an adaptive response occurred during this event, we conducted a "resurrection" study of the cutleaf monkeyflower (), an annual plant, by comparing trait means and variances of ancestral seed collections ("pre-drought") with contemporary descendant collections ("drought").

What can local and geographic population limits tell us about distributions?

Premise Of The Study: Understanding the evolutionary and ecological factors that determine plant distributions is of primary importance in botanical research. These factors may vary in predictable ways across different spatial scales, and thus, we can leverage scale to reveal the underlying processes limiting plant distributions.

Methods: We review various research considerations across local and geographic scales, including the investigation of dispersal and habitat limitation, evolutionary factors, abiotic and biotic factors, and research logistics.