Shifting dispersal modes at an expanding species' range margin

Area of Science:

• Ecology
• Population Genetics
• Invasive Species Biology

Background:

• Range expansion is crucial for species survival and ecological impact.
• Dispersal modes (contiguous vs. noncontiguous) are key to understanding range expansion dynamics.
• Local-scale dispersal mechanisms in expanding populations remain understudied.

Purpose of the Study:

• To investigate dispersal modes at a local scale for an invasive grass (Brachypodium sylvaticum).
• To determine if colonization at the edge of an expanding range occurs via contiguous or noncontiguous dispersal.
• To understand how dispersal strategies change as an invasion matures.

Main Methods:

• Utilized highly polymorphic genetic markers to analyze population structure.
• Employed Bayesian clustering to infer population relationships.
• Assessed patterns of genetic diversity and gametic disequilibrium.

Main Results:

• New populations were colonized via noncontiguous dispersal, even at local scales.
• Evidence suggests an establishment phase where pioneer populations do not disperse to adjacent sites.
• Admixture was observed in older populations.

Conclusions:

• Noncontiguous dispersal dominates initial colonization, even locally, for this invasive grass.
• Dispersal modes appear to shift from noncontiguous to potentially more contiguous as populations establish and mature.
• Understanding these local-scale dispersal dynamics is critical for managing invasive species.