Spruce colonization at treeline: where do those seeds come from?

Area of Science:

• Ecology
• Forestry
• Genetics

Background:

• Treeline ecosystems are limited by harsh environmental conditions, but warming temperatures and reduced traditional animal husbandry are facilitating upward shifts.
• These changes create opportunities to study the interplay of selection and gene flow in driving tree migration dynamics.

Purpose of the Study:

• To investigate the balance between local reproductive success and external gene flow in a Norway spruce population colonizing a treeline area.
• To evaluate the contribution of local adults versus immigration to juvenile recruitment at the treeline.

Main Methods:

• Parentage analysis was conducted using five microsatellite markers on 342 Norway spruce juveniles and 23 adults.
• Sampling occurred in a recently colonized treeline area in the Paneveggio forest, Eastern Alps, Italy.

Main Results:

• Only 11.1% of juveniles had both parents identified among the local adult population.
• Approximately two-thirds of the sampled gametes originated from outside the local population.
• Effective seed dispersal showed a peak at a mean distance of 344.66 m from the seed source, with skewed reproductive success among local adults.

Conclusions:

• While a few local Norway spruce adults contribute significantly to local recruitment, substantial gene flow from external sources persists.
• The advantages of local adults, such as local adaptation or phenological synchrony, did not impede significant gamete immigration into the treeline area.